Water Injection System Operating Procedure

SCHIEHALLION OPERATIONS

SYSTEM DESCRIPTION AND OPERATING PROCEDURE:

WATER INJECTION SYSTEM

Document no. Z-8000-BB-4076



2005 BP Exploration UK

Z1 20/01/2005 Revised RL RL

C6 2/12/2004 Addition of 4 th WI pump RL RL

C5 19/12/2003 4 th WI pump study RL RL

C4 14/12/2001 Risk assessed

C3 9/3/2001

C2 28/12/00

Revised onshore

Revised Offshore

CD RL

C1

B1

A1

Rev

7/7/98

20/5/98

2/7/97

Date

Validated for Use

Issued for Review

Issued for Comment

Description

DH RL

DH RL

AS DH

CD RL

PS RL

CD RL

By Check By Check By Check

REVISION Originated Validated Risk Assessed

Z-8000-BB-4076 Rev Z1 20 January 2005 Page 1 of 158

WATER INJECTION SYSTEM - DESCRIPTION & OPERATING PROCEDURE

Contents

1. 4 INTRODUCTION

1.1 Purpose of Equipment/System

1.2 List of Reference Documents

4

5

2.

3.

DESCRIPTION

2.1

2.2

Summary of Equipment

Water Injection Deaeration Package Z-44101

2.3 Water Injection Pumps P-45001A/B/C

2.3.1 Water Injection Pumps P-45001A/B/C Drive Motors 11

7

7

8

10

2.3.2 Water Injection Pumps P-45001A/B/C Lube Oil System 11

2.4 4 th Water Injection Pump Package 11

2.4.1 4 th Water Injection Pump Gas Turbine 13

2.4.2 GT Combustion Air Intake System

2.4.3 GT Combustion Exhaust System

2.4.4 Gearbox

2.4.5 Water Injection Pump P-45001D

15

18

18

19

2.4.6 Lubricating Oil System

2.4.7 Gas Turbine Enclosure

2.4.8 Gas Turbine Local Control Room & LER

2.4.9 Gas Turbine Enclosure Fire Protection System

2.4.10 Wash Cart

2.5 Water Overboard Discharges, Monitoring & Reporting

2.6 Chemical Injection

22

26

28

30

34

36

38

39

39

40

2.7 Turret Water Injection, Swivel and Turret Valves

2.8 Water Injection Flexible Risers

2.9 Subsea Water Injection System

2.10 WI Wellheads (Tree, Choke, Master & Subsurface Valves) 47

2.11 Well Injectivity Decline

2.12 Water Injection Subsea Flowlines

2.13 Water Injection Wells

WATER INJECTION SYSTEM CONTROL PHILOSOPHY

3.1 Deaerator Tower V-44101Control

3.2 Stripping Gas Regeneration Control

3.3 Water Injection Pumps P-45001A/B/C Control

3.4 Gas Turbine Control System

3.5 Water Injection Pump P-45001D Control

3.6 Subsea Water Injection Valve Control

50

50

51

53

53

54

55

56

59

60

4. WATER INJECTION SYSTEM & GAS TURBINE OPERATION

4.1 Pre-Start Checks

4.2 De-Aerator Package Purge Procedure

4.3 De-Aerator Package Start-up

61

61

62

63

4.4 Water Injection Pumps P-45001A/B/C Start-up 64

4.5 Solar Gas Turbine & Water Injection Pump P-45001D Start-up 67

4.6 Exhaust Gas Purging

4.7 4 th Water Injection Pump & Turbine Start-up from CCR

73

73


4.8 Gas Turbine Compressor Cleaning using Wash Cart

4.9 Routine Operations of the 4 th Water Injection Pump and GT

4.10 Subsea/Well Operating Limits

4.11 Water Injection Pump P-45001D Speed Control

4.12 Water Injection Pump P-45001D Standby Mode

4.13 De-Aerator & Pumps P-45001A/B/C Shutdown

4.13.1 Normal Shutdown

4.13.2 Emergency Shutdown

4.14 Water Injection Pump P-45001D & Turbine Shutdowns

89

4.14.1 Normal Shutdown or Trip Turbine to Idle Speed

4.14.2 Manual Emergency Stop

4.14.3 Control System Stops

4.14.4 Back-up Active Shutdown

4.14.5 GT Enclosure Fire Detection

4.14.6 Turbine Back-up Overspeed

4.15 Isolation for Maintenance

4.16 Winterisation

4.17 Video Display Computer Operation

5. CONTROL & MONITORING

5.1 Subsea Control & Monitoring

5.1.1 Interlocks

5.2 Control & Monitoring of Water Injection System

5.3 Monitoring of Pump P-45001D & Gas Turbine

6. ALARMS & SHUTDOWNS

6.1 De-Aerator HIPS

6.2 Pumps P-45001A/B/C Alarms and Actions

6.2.1 Pump P-45001A Alarms & Actions

6.2.2 Pump P-45001B Alarms & Actions

6.2.3 Pump P-45001C Alarms & Actions

6.3 Pump P-45001D & Turbine Local & Remote Alarms

6.4 Pump P-45001D

– Alarms, Actions, Shutdowns & Resets

121

6.5 Pumps P-45001A/B/C Shutdowns

6.6 ESD Actions & Valve Closure Sequences

6.6.1 Yellow ESD Shutdown

6.7 Design Parameters

6.6.2 Water Injection Pump Trip PSD

7. FAULT FINDING

7.1 Water Injection Pumps Malfunctions

7.2 Gas Turbine Malfunctions

7.3 Control System Malfunctions

7.4 Gas Turbine Acoustic & Filtration Package Malfunctions

APPENDIX A - VALVE POSITION TABLES

4 TH WI PUMP GAS TURBINE EXHAUST DISPERSION STUDY

75

77

83

85

86

86

86

90

91

91

92

94

95

95

95

95

96

97

97

98

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109

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112

115

118

126

129

130

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137

144


1. INTRODUCTION

1.1 Purpose of Equipment/System

As Schiehallion oil is produced, the space once occupied (reservoir voidage) is filled up by natural aquifers attached to the reservoirs, but not at a sufficient rate to maintain the required reservoir pressure/voidage replacement.

Produced water and seawater is therefore injected from the FPSO through subsea equipment to the wells to assist the natural drive. The aquifers provide edge drive from the west on Schiehallion and the North and West for

Loyal. Water injection minimises loss of productivity and increases Gas Oil

Ratio (GOR). All produced water is normally re-injected into the reservoirs.

However, de-aerated seawater is used as make-up feed to the water injection system to maintain production.

Three 13.8kV motor-driven water injection pumps each of capacity 630m 3 /hr pump water at high pressure (over 200 bar) to the subsea water injection wells. They are fed with a combination of produced water and de-aerated sea water, depending on well fluids BS&W, reservoir performance, process separation and operational requirements. To cater for the requirements of the future North West production centre water injection wells, a new Solar

Taurus 70 gas turbine-driven water injection pump has been installed of capacity 930 m 3 /hr. The turbine burns fuel gas from production.

The water injection system receives filtered seawater from the seawater distribution system and removes oxygen from this water to prevent contamination of the reservoir. The water injection pumps serve to drive the treated seawater and/or produced water into selected water injection wells.

Well fluids from the reservoirs contain entrained water that must be separated out, treated and disposed of prior to the oil being stored in the cargo tanks. If this produced water was not removed, the cargo would be adulterated with water, cause possible corrosion in the FPSO storage tanks, and be of unmarketable quality for export. Currently excess water is drained off at

Sullom Voe Terminal. Produced water production is expected to rise and plateau at 217,000 bbl/day (1438m 3 /hr) in year 15 of production.

The produced water system can process 225,000bbl/day (1490m

3

/hr) of produced water from the separation trains, with the facility to upgrade to

270,000bbl/day (1790m

3

/hr). Produced water is processed using hydrocyclones to 25 ppmv oil-in-water and is then injected into the reservoir with de-aerated seawater. Some may be discharged overboard if clean enough do so and if it cannot be re-injected.

The water injection system total capacity has now been increased to

2820 m

3

/hr following the addition of the 4 th Water Injection Pump.

The volume of water required for water injection is greater than the volume of produced water obtained from the production profile. A water injection rate of

1.1 times total fluid production rate is required, so de-aerated sea water is always used to supplement the produced water (the pumps are not designed to pump produced water only).


All water injection valving within the turret system is manually operated with no associated automatic control.

Treated produced water is utilised for water injection into the reservoirs under normal operations. Two hydrocyclone trains reduce the free oil content of the main flow of produced water; a separate hydrocyclone being utilised for water from the test separator. Both streams of treated water are then comingled, de-gassed, and fed to the water injection pumps.

When any produced water is discharged overboard, it is cleaner than current legislation requires thus minimising pollution and maximising recovery of oil back to the process system.

1.2 List of Reference Documents

The following drawings and documents have been referred to in the preparation of this System Operating Procedure.

L-8000-GF-0004.00

L-8000-GF-0104.00

UFD - Water Injection System

PFD - Deaeration Plant

L-1000-GP-0041.01

L-1000-GP-0041.02

L-1000-GP-0043.00

L-8000-GP-0044.00

L-8000-GP-0046.01

L-8000-GP-0046.02

L-8000-GP-0004.01

L-8000-GP-0076.03

M-5031-MA -8007.00

M-5021-GP-8004.00

S-9000-NP-9203.02

S-9000-NP-9220.01

S-9000-NP-9221.01

S-9000-NP-9213

S-9000-NP-9215

S-9000-NP-9216

S-9000-NP-9224

S-9000-NP-9225

S-9000-NP-9226

L-8000-JC-0002.024

L-8000-JC-0002.037

S-9000-GC-9200

Produced Water Degasser

Produced Water Booster Pumps

P&ID - Water Injection Deaeration Tower V-44101

P&ID - Compression & De-Oxidiser Vessels

Water Injection Pumps P-45001 A/B/C

P&ID - Water Injection Pumps Interfaces

SBM/B&R/ and B&R/H&W Interface P&ID

Seawater Distribution

12” Water Injection Swivel (Turret)

Water Injection P&ID (Turret)

Water Injection Tree (Type 1) sheets 1&2



P&ID - Schiehallion Central Manifold

P&ID - Schiehallion FPSO West Manifold

P&ID - Schiehallion FPSO Loyal/North Manifold

P&ID - Schiehallion Loyal Manifold

P&ID - Schiehallion West Manifold

P&ID - Schiehallion North Manifold

Process CPS Cause and Effect WI System

Process CPS Cause & Effect Chemical Injection

Subsea/Wells Cause and Effect


1.2 List of Reference Documents (continued)

Solar Turbine

Operator’s Guide, Volumes 1&2

Solar Turbine Data, Volumes IIIA, B & C

Solar Turbine Illustrated Parts List, Volume IV

Veritec Engineering, O&M manual for the LER

Sulzer Pumps O&M manuals, Volume 1, 2 & 3

WG Process Design Report, Volumes 1&2

Renk operation and maintenance instructions

Gas Turbine Filtration and Acoustic Package –

Installation and Maintenance manual, Altair Filter

Technology

GT Driven 4 th WI Pump Project Wood Group

37W022F0146/P/OP/000

7/000

Z-8000-BB-4001

Z-8000-BB-4007

Z-8000-BB-4051

Z-8000-BB-4052

Z-8000-BB-4054

Z-8000-BB-4057

Z-8000-BB-4035

Z-8000-BB-4023

Z-8000-BB-4077

Z-8000-BB-4029

Z-8000-BB-4012

Plant & Instrument Air Systems

Chemical Injection Systems

Methanol System

Nitrogen Generation & Distribution

Produced Water System

Seawater Circulation Systems

Fuel Gas System

Non-Haz Open Drains Collection System

Fresh Water System

Flare Systems

Cooling Medium System

Training and Competency in understanding this system is covered by documents Z-8000-BQ-4176/4276 which include questions and answers on the system.


2. DESCRIPTION

2.1 Summary of Equipment

The following table provides data on equipment in the water injection system:

Equipment

Water Injection

Deaerator Tower

V-44101

Water Injection Stripping

Gas Blowers P-

44201A/B

Stripping Gas

Exchanger

X-44201

Stripping Gas

De-oxidiser Vessel

V-44201

Start-up Heater

EEH-44201

13.8kV 5200kW Motordriven Water Injection

Pumps P-45001A/B/C

Gas Turbine-driven

Water Injection Pump

P-45001 D

Gear Box

Solar Taurus 70 gas turbine (burns fuel gas)

Wash Cart

Rating Location

Seawater Flow - 2250 m 3 /hr

Operating Pressure - 5 barg

Height - 15m

Diameter - 3.1m increasing to 4.2m

5 barg inlet - 6.4 barg outlet

Motor rating 55 kW

356 mm OD x 5180 mm

Shell side - 5.7 barg

Tube side - 6.4 barg

1200 mm OD x 3000 mm

187 mm x 1780 mm

Power - 20 kW

Max capacity 750 m 3 /hr (each)

Differential Pressure - 202 bar

(dependent on start-up DP or normal running DP)

Capacity 3 x 33%

Normal Case (100% Speed) 930 m 3 /hr

Package Z-44101

Fire Zone 201

(Port Aft)

Package Z-44101

Fire Zone 201

(Port Aft)

Package Z-44101

Fire Zone 201

(Port Aft)

Package Z-44101

Fire Zone 201

(Port Aft)

Package Z-44101

Fire Zone 201

(Port Aft)

Packages

Z-45001A/B/C

Fire Zone 251

(Starboard Aft)

Overspeed Case (105% Speed) 1150 m 3 / hr.

Installed forward of the aft Crane pedestal at frame 40

(Palette 7)

Fire Zone 258 Differential pressure: 202 Bar

(Dependant on the start-up DP or

Normal Running DP)

Rated for 6910 KW

Input Speed 11051 RPM

Output Speed 3650 RPM

Can be run continuously 5% above the rated speed.

6700-7800kW, depending on ambient temperature

Palette 7

Palette 7

Tank Capacity: 100 litres

Operating Pressure: 6.9 barg

Operating Temperature: Ambient

Design Temperature: 93.3 C

Design Pressure: 9 barg

Size (DxL): 0.406m x 0.483m

Palette 7

Table 1 Water Injection System Equipment Data

Note:

Information given in this document does not include details of the new

North-West drill centre.


2.2 Water Injection De-aeration Package Z-44101

Refer to P&ID L-8000-GP-0043.00

.

Z-44101 de-aerates seawater to an oxygen content of below 20 ppb prior to the seawater being injected into the reservoir. The de-aeration package is based on ‘Minox’ technology and uses nitrogen stripping gas to remove oxygen from the seawater. Oxygen is subsequently removed from the stripping gas using a catalytic de-oxidising process. This system was selected in preference to the more normal vacuum deaeration systems as the ‘Minox’ column operates with a single stage of packing which leads to a lower column height. The height of the column was a concern due to its location adjacent to the helideck. Alternative designs all had columns which were above helideck elevation.

The system uses conventional counter-current flow (stripping gas against seawater) within a compact deaerator tower which contains structured packing to promote contact between the nitrogen and seawater. The oxygen-contaminated stripping gas leaves the tower and passes through blowers and a heat exchanger before being purified (i.e. its oxygen removed) through a catalytic reaction with methanol vapour. The purified stripping gas is then recycled to the deaerator tower. The de-aerator package comprises:



water injection de-aeration tower V-44101



water injection stripping gas blowers P-44201A/B



stripping gas exchanger X-44201



stripping gas de-oxidiser vessel V-44201



start-up heater EEH-44201.

Seawater is supplied to V-44101 from downstream of the cooling medium coolers X-81501A/B/C. The seawater is normally supplied between 22



C and

27



C with a minimum supply temperature of 5



C and a maximum supply temperature of 33



C (design temperatures. -10/+50



C). The oxygen content of the seawater entering de-aeration is approximately 10 ppm.

Seawater enters V44101 via an 18” line at the top of the tower after passing through the inlet flow control valve. Seawater leaving V-44101 is normally routed to the water injection pumps P-45001A/B/C/D. In the event that the seawater demand of P-45001A/B/C/D is low, seawater from V-44101 is routed overboard via the overboard dump valve.

Seawater entering V-44101 falls under gravity through a distributor and a bed of structured packing, and exits at the bottom of the tower before being routed the water injection pumps. Over-pressure protection of V-44101 is provided by PSV-441005 or PSV-441006 (set at 10 barg) which relieve to a safe location.

The deaerator is protected by a HIPS system which shuts the seawater inlet valves XXV-441040 and XXV-441002 on high vessel level, initiated by

LAHH-441013 and LAHH-441014.

Note: A HIPS system is required on the deaerator as the vessel relief valves are not designed for full seawater flow relief.


The water passes down through the tower and mixes with a counter-current flow of stripping gas (nitrogen) fed into the tower at a mid-vessel point, below the packing column. The stripping gas absorbs oxygen contained in the seawater and then passes through a demister in the top of V-44101 before leaving the tower via a 6” line. Nitrogen is supplied to the deaerator tower at a flow of approximately 4,900 kg/hr. As the nitrogen passes through the tower packing, some of it is dissolved in the seawater and, therefore, there is a requirement to add nitrogen to the system to maintain the required stripping gas flowrate. In addition, to achieve the required oxygen concentration in the stripping gas, so as to maintain reactor efficiency, more oxygen must be added. The required nitrogen and oxygen make-up is achieved by using a combination of instrument air and nitrogen top-up lines.

Refer to P&ID L-8000-GP-0044.00.

Stripping gas is drawn off from V-44101 by the water injection stripping gas blowers P-44201A/B, which are rotary lobe, positive displacement type blowers. P-44201A/B are each fitted with their own single dedicated safety relief valve (PSV-442003 and PSV-442006 respectively) which have a setpoint of 10 barg and relieve to a safe location. P-44201A/B operate in duty/standby mode with auto-start of the standby blower initiated by the low flow alarm FAL-442008. P-44201A/B cannot be started until a normal operating level (i.e. flow and level healthy) is established in V-44101.

On leaving the blowers, the stripping gas passes through the tube side of the stripping gas exchanger X-44201 where it is pre-heated against stripping gas returning from the stripping gas de-oxidiser vessel V-44201.

Stripping gas from X-44201 enters the de-oxidiser vessel V-44201. The temperature of the gas entering V-44201 is controlled by TIC-442014. The gas flows downwards into a de-oxidiser catalyst bed in which is embedded the electric start-up heater EEH-44201. The catalyst is palladium pellets on an aluminium oxide core supported on a perforated plate.

To create the catalytic effect in V-44201 which is required to purify the nitrogen, methanol is added, as a fuel, to the stripping gas. This is injected as a side stream into the main stripping gas flow at an entry point upstream of the reactor V-44201. The catalyst within V-44201 needs to achieve a threshold temperature before the required catalytic reaction can take place.

The catalyst bed is pre-heated by EEH-44201 to this threshold temperature of

150



C. Once this temperature is achieved then the power supply to the start-up heater is shut-off as the resulting reaction within V-44201 is an exothermic reaction during which temperatures of 240



C to 260



C may be produced. Stripping gas leaving V-44201 is virtually oxygen-free (i.e. oxygen content below 20 ppb).

Stripping gas from the bottom outlet of V-44201 passes through the shell side of X-44201 and returns (via the restriction orifice RO-442022) to the deaerator tower, forming a closed loop for the circulation of stripping gas.

The gas path through the shell side is protected by a single relief valve

PSV-442011 (set at 10 barg) which relieves to a safe location.

Some of the stripping gas in the tower is dissolved in the seawater.

Additionally, the stripping gas oxygen concentration may fall below that required to maintain reactor efficiency. Nitrogen make up is supplied via

XV441024 on the 2” feed line from the nitrogen distribution system.

PIC-441021 on the deaerator outlet line controls nitrogen top-up via

PCV-441023 or vents to safe location via PCV-441021.


Seawater as Deaerator Oxygen Scavenger Carrier

When oxygen scavenger injection is needed to reduce the oxygen content of the injection water, produced water taken from downstream of the booster pumps is used as the normal oxygen scavenger carrier. There are situations, however, when it may be necessary to inject oxygen scavenger into the deaerator and if there is either no, or insufficient, produced water available.

This will occur during early production before the produced water cut increases, on de-aeration system start-up and also during seawater injection, when the separation trains are down. A facility has therefore been included to substitute deaerated seawater as the carrier by routing seawater into the degasser from the outlet of the deaerator.

The manually-operated crossover line 2”-WI-450010-A10B is designed to transfer water from the discharge of the deaerator to the inlet line of the degasser. The rate is controlled by the manual globe valve downstream of

XV-540010, which will pass about 30 m 3 /hr when fully open. The scavenger carrier, (pumped in this mode by a single produced water booster pump), and taken from upstream of LCV430010B via 2”-PW-441006-A01B, has a rate set at 15 m 3 /hr, controlled by RO-441029. The globe valve should be set such that deaerated seawater accumulates in the degasser.

2.3 Water Injection Pumps P-45001A/B/C

Refer to P&ID L-8000-GP-0046.02

.

3 x 33% Water Injection Pumps P-45001A/B/C are fed with a combination of de-aerated seawater and produced water.

The Sulzer 13.8kV 5200kW electric motor-driven water injection pumps take suction from deaerator V44101; or from produced water booster pumps P-

43001A/B/C and filters F-43001A/B via a 24” common inlet. The injection pumps then discharge via the oxygen analyser AT450020 into a common 16” line which reduces to a 12” prior to entering the turret and turret swivel N-

45080. Downstream of the turret, the water flows to a 12” water injection manifold and then down

10” flexible water injection risers. Subsea distribution routes the water to the water injection wells. The number of WI pumps in service is governed by the number of injection wells being fed.

If any of the injection pumps supply more water than can be injected subsea, the excess will be discharged overboard via minimum flow dump valves

FCV450145/245/345 (fitted to each pump A, B, C) through a common 10” overboard discharge with vent. There is no flow monitoring or sampling on this common line.

Each pump’s discharge pressure will depend upon the pumped fluid density, and this in turn varies both with the different proportions of seawater and produced water and with temperature. The expected pump performance may be calculated as follows:



P in bar = Head (m) x water density (kg/m 3 ) x 9.81/1 x 10 5

During seawater-only injection at a normal temperature of 22



C, the pumps could generate 246 barg at 750 m 3 /hr. Currently, the nominal output from each pump is 630m 3 /hr. The pump performance curves and associated documentation show two duty points. The higher head duty point is indicative of an early field life case when there are only a few injection wells and the water injection requirement has not peaked.


However, even for low injection water demand at the wells, a significant flow is required through the pump to reduce the system pressure and minimise the peak pressure which may be obtained due to pressure surge/locked-in pressure due to inadvertent wing valve closure. This is accomplished via a high set point for the minimum flow FCVs. At full capacity, the system is set up with four pumps operating. It is advantageous to inject as much water as possible into the reservoir and therefore no standby or auto-start operating mode is provided. The system can, however, be configured with any number of pumps (1, 2 ,3 or 4) as running duty pumps.

2.3.1 Water Injection Pumps P-45001A/B/C Drive Motors

Each water injection pump A/B/C is driven by a 13.8 kV electric motor

PM-45001A/B/C rated at 5200 kW and fed from the main switchboard

ESW-83401. Each motor winding is cooled by air circulation to vent using a

GEC Purgepak system. A heat exchanger cools the circulated air and is fed by water from the cooling medium system. High winding temperature is indicated locally. A casing high-level alarm and an anti-condensation heater are also fitted.

2.3.2 Water Injection Pumps P-45001A/B/C Lubricating Oil System

The water injection pump support and thrust bearings, together with the drive motor bearings, are lubricated by a self-contained lubricating oil system, integral with each unit. Oil is supplied by a main shaft-driven pump, backed up by a motor-driven auxiliary lubricating oil pump P-450100/200/300.

Lubricating oil is stored in a lubricating oil tank fitted with heater and level and temperature indicators. The auxiliary lubricating oil pumps are sited within the tank and supply oil to the bearings on starting. These pumps are automatically stopped when the shaft-driven pumps P-450101/201/301 supply sufficient lube oil pressure. Excess pressure flows back to the sump via

PCV-450137/237/337.

Oil flows through oil cooler X-450100/200/300 to lube oil filters A & B and

PCV-450138/238/338 and then to the bearings. Low oil pressure, high oil temperature, oil filter high differential, and high pump bearing alarms are indicated at the local control panel in the Aft Equipment Room. Sight glasses show oil flow back to the lube oil tank.

2.4 4

th

Water Injection Pump Package

Currently, three 13.8kV motor-driven water injection pumps each of capacity

630m 3 /hr pump high pressure water (over 200 bar) to the subsea water injection wells. They are fed with a combination of produced water and deaerated sea water, depending on well fluids BS&W, reservoir performance, process separation and operational requirements.

To cater for the requirements of the North West production centre water injection wells, a new Solar Taurus 70 gas turbine-driven water injection pump has been installed forward of the aft Crane pedestal at frame 40 in Fire

Zone 258, fuelled by fuel gas. This is fitted with a 900mm exhaust discharging at an elevation of 55m and pointing forward at an angle of 10

 above horizontal, thus creating minimal impact on Helideck operations. The output of the new engine is 6700-7800kW, depending on ambient temperature. The forward-pointing exhaust directs gases away from the

Helideck and the elevation eliminates any problems with hot gases on the

Crane boom.


Figure 1 4 th Water Injection Pump Package – Plan View

The blast wall (capacity 0.5 bar) is not affected by the installation of the gas turbine-driven water injection pump. The fuel gas supply to the skid is high on the starboard outboard side, allowing any potential leaks to be dispersed away from the FPSO. High integrity joints have been used to connect the minimal number of pipe sections.

Further details of the 4 th Water Injection Pump exhaust dispersion arrangements can be found in the 4 th Water Injection Pump Gas Turbine

Exhaust Dispersion Study (enclosed at rear of this document).

Water injection pump P-45001D is a gas turbine-driven pump using a Solar

Taurus 70 as the driver and operates in parallel to the existing three electric driven water injection pumps P-45001A/B/C. The pump suction line is connected from the existing water injection suction manifold and the discharge line is connected to the existing water injection discharge line to the turret. Injection water supplied to the 4 th water injection pump suction is a mixture of seawater and produced water.

The three electric-driven water injection pumps P-45001A/B/C were designed for a capacity of 2025 m 3 /h and the new water injection pump P-45001D is designed for a capacity of 930 m 3 /h normal operating case and 1150m 3 /hr overspeed case. The total designed maximum water injection capacity is now

2955m3/h (444,500 bbl/day).


The 4 th water injection package & system comprises:

1. 4 th water injection pump gas turbine

2. combustion air intake system

3. combustion exhaust system

4. gearbox

5. water injection pump

6. lubricating oil system

7. gas turbine enclosure

8. 4 th water injection pump gas turbine LCR & LER

9. CO

2

deluge system

10. wash cart.

2.4.1 4 th Water Injection Pump Gas Turbine

The 4th water injection pump driver is a Taurus 70S gas turbine which contains the following main components:















Accessory Drive Gear box

Air inlet plenum

Axial flow compressor

Annular Combustor with Fuel Injectors

Two Stage Gas Produce Turbine / Two Stage Power Turbine

Exhaust Collector

Output Drive Shaft to Gearbox and 4 th Water Injection Pump.

The gas turbine is mounted on a steel base frame. The accessory drive is attached to the air inlet assembly and is driven by the gas turbine’s axial compressor. This then supports and drives the lube oil pump and other accessories, which are initially driven by the start system. The turbine speed is directly related to the engine power level due to its two-shaft engine configuration and is electronically adjusted. Air enters the air inlet and is compressed by the 12-stage axial flow compressor. Pressurised air in the annular combustion chamber is injected with fuel and the mixture is ignited during the start cycle.

Figure 2 4 th Water Injection Pump Package – Looking to FPSO Port Side


If there is a sufficient flow of pressurised air the burning of fuel is maintained.

Hot pressurised gas from the combustion chamber expands and drives the turbine. As it exits the chamber its pressure and temperature drop.

Approximately a quarter of the total air compressed is required to completely combust the fuel. Excess air is used to cool the combustion chamber and mixes with the combustion products to reduce the gas temperature downstream at the inlet to the first stage turbine. The gas turbine is supported by the following auxiliary equipment:













Start System

Fuel System

Electrical Control System

Lube Oil System

Engine drain system

Acoustic and Filtration Package

Gas Turbine Start System

The start system consists of an AC direct start system, which includes a starter motor with variable frequency drive. It provides the torque to initiate rotation and enables the engine to reach a self-sustaining speed, after which the starter shuts down, the starter clutch overruns and the engine is able to accelerate under its own power to loading speed.

The starter motor (B330) is a squirrel-caged induction 15-minute inverter duty, polyphase-type motor which can accelerate the engine from standstill to starter dropout speed. The motor power is provided by the variable frequency drive (VFD430). This motor speed controller operates on 380-460V AC 3phase power at line frequencies of 48-62 Hz. It is rated at 231 amps

(maximum) and incorporates a keypad/display, which can be used to program configuration adjustments through software. When the start cycle is initiated a timed pre-lube sequence is activated. On expiry of this the control system directs power to the variable frequency drive, which provides power to the starter motor.

A low frequency and voltage is generated which begins rotation. The frequency and voltage are then ramped up to accelerate the engine to purging speed which is maintained by a programmed fixed current. Once purged, the engine coasts down to light-off speed. When light-off speed is detected the VFD430 is re-energized and it increases the motor velocity to starter drop-out speed. VFD430 is then deactivated by the control system, cuts power and the motor clutch is disengaged.

Gas Turbine Fuel System

The fuel system controls the fuel pressure and automatically regulates the fuel flow according to operating requirements in conjunction with the control system whilst the air system automatically schedules fuel for flow during the engine acceleration and load operation. Over-temperature and overspeed topping control of fuel flow and automatic shutdown is also provided by the fuel system, which comprises:







Gas fuel metering and control

Instrument air for the operation of the pilot-operated shutoff valves

SoLoNOx low-emissions system.


Before the engine cranks a valve check sequence is performed to confirm that the shut-off valves are operational. If the shut-off valve malfunctions, the control system initiates a valve failure and aborts the start cycle.

Once the valve check is complete the purge crank cycle is initiated; this removes all combustibles from the engine exhaust system. The start system cranks the engine and creates air movement through the exhaust system.

The purge crank cycle timer is programmed to correspond to the package exhaust system volume.

Following this, gas flows through the torch and is ignited in the presence of combustion air. The torch flares in to the airflow in the engine combustion liner. Equally-spaced fuel injectors mix fuel in the air stream and in the combustor liner. The torch then ignites the fuel/air mixture and the engine temperature increases rapidly. The control system increases fuel flow and consequently increases the engine temperature and the engine speed. When the engine speed reaches approximately 60-65%, the start system is deenergized. The engine continues to accelerate and the inlet variable vanes move toward the fully-open position. The compressor bleed valve also closes, which increases the engine temperature further. The control system then increases the fuel supply until the engine speed reaches 90% at which point the engine is ready for load.

Once the system is at 50% load and the engine speed is above 88% the fuel system transfers to the SoLoNOx mode. The inlet variable vane position, fuel flow and compressor bleed valve position are adjusted by the control system to maintain the engine temperature.

If the engine temperature exceeds the preset limit, a 20 second time delay is imposed. If the engine temperature remains above this limit, a high temperature alarm is initiated which shuts down the engine. A time delay is incorporated to allow for momentary over-temperature. If the temperature shutdown timer fails and the turbine temperature increases further, a backup high temperature circuit initiates engine shutdown.

2.4.2 GT Combustion Air Intake System

Air enters the engine through the air inlet plenum. Air through the annular opening is redirected from the radial flow path to an axial flow path. A heavy mesh screen minimises the entry of the large solid foreign material in to the engine compressor air inlet.

A Variable Inlet Guide Vane (IGVs) system is provided to avoid compressor surge and to maintain maximum engine performance over the full gas producer range. The variable vane control positions the angle of IGVs and the variable stator vanes (VSVs) of the first five compressor stages as a function of corrected gas producer speed (NgPcorr). This is done to aerodynamically match the effect of the air density changes over the -40 o C to 60 o C range of the compressor inlet temperatures.

The variable vane system uses a slave cylinder positioned by a hydraulic positioner connected to the engine ’s actuator arm. The positioner’s electronic control signal has a range of 4mA fully closed to 20mA fully open. If the electrical signal is lost, the IGVs and the VSVs move to a closed position

(minimum variable vane angle).


Acoustic and Air Filtration Package

To ensure clean air is supplied to the turbine (and to reduce noise surrounding the gas turbine) an acoustic and filtration package is employed.

The acoustic and filtration package (designed and manufactured by Altair

Filter Technology Ltd) is a modular system and is made up of the following major system components:



Combustion Intake System -Mini Module



Gas Turbine Enclosure



Gas Turbine Enclosure Ventilation System



Combustion Exhaust System -Mini Module



Electrical / Instrumentation / Fire Protection System



Structural Steelwork and Access Facilities



Lube Oil Pipe work assemblies

The system is designed to withstand the following conditions:



High wind speed



Wind strength changes & gusting



Chloride attack by the atmosphere



Turbine process conditions



Thermal growth



Static & installation loading

The filtration system provided is an Altair System High Efficiency Filtration package and comprises 4 stages:



1st stage - Marine Vane Separator and Snow Hood



2nd stage - PBR pre filter (12)



3rd stage - HVX bag filter (12)



4th stage - Vane Separator

A manometric drain system is provided for the 4th stage vane separator and the housing drains.

1st stage - Marine Vane Separator and Snow Hood

The function of the Marine Vane Separator is to reduce the quantity of driving rain or heavy spray which may otherwise enter the intake under adverse weather conditions. A snow hood is fitted prior to the 1st stage separator to provide protection against driving snow.

The vane stage comprises stainless steel vanes held apart by spacers. The high inertia of the water droplets causes them to be thrown out of the air stream onto the vanes. The droplets collected on the vanes are then drained down into the drain trough situated at the base of the vanes. Drain slots are provided in the bottom of the separator for self-draining


2nd Stage – Pre-filter Bag Type PBR

The Altair PBR Cleanable Prefilter bag is a synthetic bag filter designed to retain large particles of dust and hydrocarbons which may enter the intake.

The PBR prefilter bags make up the first stage of filtration and fit into a 316grade stainless steel holding frame. The PBR pre-filter has 4 polyester pockets which fit inside the HVX high efficiency filter located immediately behind.

3rd Stage - High Efficiency Filter Bag Type HVX

The Altair HVX bag is made up of two layers of filter media, is disposable and should not be washed. The initial layer is an open-density polypropylene filter mat which stores the majority of the dust collected. The final filter is a highdensity polypropylene filter material which captures the smallest particles.

The HVX bag also acts as a coalescer and collects fine salt particles in the airstream. The aerosol salt which enters the bag is coalesced into larger droplets which either drain away or are re-entrained into the air stream and removed by the vane separator downstream of the filter bags. The two layers are made up into individual pockets and fitted into a stainless steel frame, which fits into the holding frame.

4th Stage - Vane Separator

The purpose of the Vane Separator is to intercept droplets re-entraining from the upstream stages under conditions of high humidity. The water droplets collected on the stainless steel vanes are drained down through pockets into a drain trough situated at the base of the vanes and then flow into the drain system

Drain System

The drain system removes any water caught within the air intake from:



The filter access housing



The interspace between the 3rd stage filter and 4th stage



The 4th stage - vane separator

No drainage is required between the 2nd and 3rd stage filter. Drains are fed into a drain trap, which allows drainage but prevents air being sucked into the drain system by the provision of a water seal.

Intake Silencer and Transition

The intake silencer and transition provide acoustic attenuation for the combustion intake to the gas turbine. The silencer comprises a series of vertical splitters and a lined duct which reduces external noise levels. The intake silencer can only be inspected internally during engine shut down and via the personnel access panel in the gas turbine collector duct.

Intake Elbow & Flexible Intake Silencer

The intake elbow is lined for acoustic attenuation and turns the combustion intake air through 90 degrees into the silencer. The system ensures an even distribution of air at the inlet to the flexible intake silencer which directs clean air into the turbine inlet. A weather seal and acoustic bolster is fitted around the interface within the acoustic enclosure.


2.4.3 GT Combustion Exhaust System

The combustion exhaust system consists of a diffuser duct connected to the enclosure exhaust flange and has a support mechanism to allow for thermal growth of the duct section. A high temperature flexible compensator is fitted between diffuser duct and exhaust silencer. The compensator is designed to accommodate lateral, radial and axial movements set up by the hot gases discharging through the exhaust volute into the exhaust system.

The ducting system above the silencer is routed to suit the adjacent equipment and crane location and a 90º elbow diverts the exhaust gases to a safe location.

The exhaust collector receives the axial flow of exhaust gases from the exhaust diffuser and turns them in a radial direction. The exhaust collector and most other external areas that have high temperature surfaces are covered with an insulating stainless steel blanket to minimize heat rejection and to cover exposed surfaces.

2.4.4 Gearbox

A Renk gearbox is located between the turbine and the WI pump:

Rated Power: 6910 KW

Rated Speed:

Input: 11051 rpm

Output: 3650 rpm

Maximum Continuous Speed:

Input: 11604 rpm

Output: 3832 rpm

The gearbox can be run continuously 5% above the rated speed (overspeed design case for the pump) and has a mechanical efficiency of 98.7%.

Measuring and control instruments include:



Insufficient oil pressure at the gear unit inlet



Excessive oil temperature at gear unit oil inlet



Failure of the oil pump



Excessive bearing temperatures



Excessive shaft vibration

Oil enters the system on the suction side of the oil pump via a filler neck. The oil system must be operating before the gearbox is started and once it is stopped the oil pump must remain running until the unit has come to a complete standstill. A separate auxiliary pump is available during start-up and shutdown to ensure enough oil is supplied. This pump remains operating until the gearbox has reached nominal speed or until it has come to a complete standstill during shutdown.


2.4.5 Water Injection Pump P-45001D

Refer to P&ID L-8000-GP-0046.03. This section is to be read in conjunction with the earlier text describing WI pumps P-45001A/B/C. P-45001D is fed with a combination of de-aerated seawater and produced water from a common suction line feeding the motor-driven water injection pumps, P-

45001 A/B/C. The pump then discharges into a common 16” line, which receives water from pumps P-45001A/B/C. The flow control valve FCV-

450445 protects the pump if the flow drops below a set value. The valve discharges any excess water overboard through a com mon 10” overboard discharge.

Pump Discharge Characteristics

The GT-driven pump discharge pressure depends not only upon the pumped fluid density, but also on the speed of the gas turbine. The expected pump performance may be calculated as follows:



P in bar = Head (m) x water density (kg/m 3 ) x 9.81/1 x 10 5

During seawater-only injection mode and at a normal temperature of 22



C, the GT-driven pump P-45001D can generate 222 barg at 745 m 3 /h, when two out of three electrically-driven pumps P45001A/B/C are in operation. The total injection capacity in this mode will be 1890 m 3 /h.

During combined Seawater and Produced water injection mode and at a normal temperature of 22



C, P-45001D can generate 207 barg at 930m 3 /h.

The total injection capacity in this mode will be 2955 m 3 /h.

P-45001D can also operate in an overspeed mode, when it can generate 207 barg at 1150 m 3 /hr.

Note:

The GT-driven pump can be run either with combined seawater and produced water or with seawater only. It is not designed to run with produced water alone.

Graph 1 overleaf shows pump discharge pressure as a function of pump speed and flow rate, based on a suction pressure of 5.5 bara.


PUMP DELIVERY PRESSURE

300

250

200

150

100

50

0

200 400

3833 RPM

3200 RPM

2250 RPM

Pump Speed Characteristics

600 800

FLOWRATE M3/H

3650 RPM

3000 RPM

TRIP-PRESSURE

1000 1200

3400 RPM

2750 RPM

The expected flow, head and power as a function of speed can be calculated as follows:

Q

NEW

= New Flow Rate, Q

OLD

= Old Flow Rate

Head

NEW

= New Head, Head

OLD

= Old Head

Power

NEW

= New Power, POWER

OLD

= Old Power

N

NEW

= New Speed of pump, N

NEW

= Old Speed of pump

The relationship for flow rate:

Q

NEW

= Q

OLD

*





N

NEW

N

OLD






The relationship for pump head:

HEAD

NEW

= HEAD

OLD

*





N

N

NEW

OLD





2

The relationship for power:

POWER

NEW

= POWER

OLD

*





N

NEW

N

OLD





3

The minimum flow rate for the pump is 330m3/h. When the pump discharge pressure exceeds 260barg, the pump will trip on high pressure.

Graph 2 below shows required power from the gas turbine as a function of speed and flow rate. The turbine has a power limit of 6755 kW at 23 o C.

Note: If low ambient temperatures are experienced the power limit increases,

Sulzer have specified a maximum overspeed power limit as 8075 kW.

REQUIRED TURBINE POWER

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

200

3833 RPM

3400 RPM

3000 RPM

2250 RPM

400 600 800 1000 1200

FLOWRATE M3/H

3650 RPM

3200 RPM

2750 RPM

POWER LIMIT @ 20 Deg C


Graph 3 below shows turbine power as function of air temperature. As the air temperature drops, more water can be injected in the wintertime. The turbine is designed for a maximum air temperature of 23 o C.



The pump design speed is 3650 rpm



Pump overspeed is 3833 rpm



Pump idle speed is 2555 rpm (70% turbine speed)

TURBINE POWER

9000

7500

7000

6500

8500

8000

6000

-6 0 5 10

AIR TEMPERATURE o

C

15 23

2.4.6 Lubricating Oil System

The lube oil system supplies filtered lubricating oil to the turbine engine bearings, the speed reducing gearbox, the pump bearings and various package components within specified operating temperature and pressure limits. In addition, the system supplies oil at engine inlet pressure to related hydraulic subsystems. The lube oil system consists of the lube oil reservoir, oil cooling system, pumps, filters, pressure control devices and temperature control valves and is monitored by the package control system.

Lube oil is pumped from the reservoir by the main lube oil pump to the lube oil manifold. The main lube oil pressure control valve regulates oil pressure in the manifold. If the oil temperature becomes low the temperature control valve diverts flow from the water/oil cooler. As the temperature rises the control valve gradually diverts the flow of oil back in to the water/oil cooler.

From the cooler oil flows through the main lube oil filters to the oil supply manifold and through various supply lines to points of lubrication.


Lube Oil Pump Checks

When the start cycle begins the control system tests the Backup Post Lube

Pump/ Motor Assembly. If the pressure at the assembly reaches 4 psi, the control system de-energises the Pump/ Motor assembly and energises the

Pre/Post Lube Oil Pump. When the oil pressure reaches 6 psi the control system allows the Engine Pre-lube Cycle to begin.

Pre-lube Cycle

Following the lube oil pump checks the pre-lube timeout timer (60 seconds) is started, this is the allowable time for the Pre/Post Lube Pump to complete the

Pre-lube cycle. When the lube oil pressure exceeds the pre-lube lowpressure limit of 6 psi the pre-lube timer (30 seconds) is started. The engine must be pre-lubed at 6 psi continuously for the full 30 seconds and it must occur within the pre-lube timeout period (60 seconds). If it is not completed within the 60 seconds the start is aborted and a pre-lube Fast Stop nonlockout alarm is enunciated.

Lube Oil Supply when Engine Running

On completion of the Pre-lube Cycle the Pre/ Post Lube Pump de-energises when the engine is above the starter dropout speed and when the lube oil pressure is above 35 psi. At this point the Engine-Driven Pump begins supplying Lube Oil Pressure and continues to steady state condition. Once this pump reaches steady state the Lube Oil Schedule become active.

During steady state condition the Pre/Post Lube Oil Pump energises if:



The engine is below the starter dropout speed and the lube oil pressure is at or below 25 psi.



Engine speed of greater than 5% engine speed (Ngp) is detected.

The Pre/Post Lube Pump will not be annunciated as failed during steady state engine running condition when the Lube oil pressure is less than the Post

Lube Low Pressure Shutdown Limit because the Engine Driven Pump may be at fault.

Run protection for the engine is provided during steady state engine running.

This achieved by energising the pump/motor assembly at any time the lube oil is below the lube oil low-pressure alarm limit. The pump runs for 30 seconds and is then de-energised. The following scenarios are possible:

 If the lube oil pressure continues to fall below the allowable limit to the shutdown limit, a Fast Stop Lockout engine shutdown is initiated and the pump/motor BP 903 helps to protect the engine bearings during shut down.





If the lube oil pressure continues to drop below the allowable low limit but stabilises between this limit and the shutdown limit continuously for 5 seconds again this initiates a Fast stop Non-lockout engine shutdown and the pump aids bearing protection during shutdown.

If the lube oil pressure increases above the low pressure limit after 30 seconds or when pump/motor BP 903 is de-energised and the pressure once again decreases, the pump/motor is energised again.


Lube Oil Reservoir Separator/Filter

Lube Oil Reservoir Separator/Filter (FSA901), located in the lube vent stack, is a coalescing-type separator/filter which collects oil mist droplets and drains oil back to the lube oil reservoir. The oil mist eliminator is a freestanding vessel with the oil reservoir vent ducted to it. The vented air stream enters the bottom of the case and passes through a glass-fibre element where the oil particles are captured. The clean air exits from the top of the vessel and oil collected drains to a liquid seal and back to the lube oil reservoir.

Figure 3 Main Lube Filter Assembly

1 Equalising Hand valve VH903 8 Stud (8 off)

2 Lube Oil Filter Transfer Valve VT901 9 Filter Case Cover

3&4 Filter 10 Filter Case Spiral Gasket

5&6 Filter Bleed Valve VH902-1 & VH902-2 11 Filter Element

7 Nut (16 off)


The main lube oil filter assembly FS901, located downstream from

Temperature Control Valve (TCV901/TCV01409D), is a non-bypass, pedestal-type oil filter assembly containing replaceable filter elements. Lube oil flow, as manually selected by positioning Lube Oil Filter Transfer Valve

(VT901), may be directed through either, or both, filters in the assembly. To facilitate filter element replacement, each filter case cover includes a Bleed

Valve (VH902-1, VH902-2). A Drain Valve (VH902-3, VH902-4) is installed at the bottom of each filter case. The two filters are interconnected by a line with a Cross Feed Valve (VH903) which enables equalizing the pressure within the cases during filter changeover and element replacement. The filter case should be completely drained before replacing filter elements.

Bellows-type Differential Pressure Gauge PDI902/ PDG01418D is connected in parallel with Main Lube Oil Filter Assembly Alarm Differential Pressure

Switch (S397-1/PDSHO1417D). The gauge indicates the differential pressure across the inlet and outlet of Main Lube Oil Filter Assembly (FS901).

Instrument Isolation Hand Valve (VI901 –1) is used to isolate the differential pressure gage from the system for calibration, testing, or replacement. After the first 1000 hours of engine operation and as appropriate thereafter, the following should be performed in addition to routine inspection items (shutting down engine prior to performing checks):



Replace lube oil and, if applicable, servo oil filter elements. Lube oil and servo oil filter elements should be replaced when visible contamination is present, when the differential pressure "pop-up" indicators are popped, or when differential pressure limits are exceeded. If none of these conditions occur, the filters should be replaced at least annually.



Check sample of lubrication oil for contamination and, if required, drain and refill oil reservoir with oil as specified on Mechanical

Installation Drawing 149708.



Check the oil cooler for accumulation of foreign material that could obstruct cooling airflow. Clean per manufacturer’s instructions.



Inspect all oil lines and oil system components for security and condition.



Top off oil reservoir as required.

Since the Main Lube Oil Filter Assembly is designed to operate using one filter of Main Lube Oil Filter Assembly (FS901) at a time, filter service may be performed during engine operation or during shutdown. It is preferred to shut the unit down and have the post lube cycle completed prior to servicing. This arrangement also permits the unit to be started while filter element replacement is in progress.

Filter elements should be changed when the filter dp indicates a need for service, whenever the oil is changed, or as annual maintenance. Increasing dp will activate an alarm.


REMOVAL OF FILTER ELEMENT

1.

2.

Open Equalising Hand Valve VH903

Position Transfer Valve VT901 to isolate the desired filter

3. Close hand valve VH903

4. Attach drain hose or place suitable container beneath drain outlet.

Remove cap from drain line and open Filter Drain Hand Valve VH902-

3 or VH902-4 for filter being serviced

5.

6.

7.

8.

Lube oil may be hot and squirt out as pressure is relieved.

Open Filter Bleed Valve VH902-1 or VH902-2 for filter being serviced.

Drain oil from filter.

Remove nuts and studs from filter case cover.

Swing filter case cover up and to one side from filter body

9. Remove spiral gasket and filter element

10. Clean filter case cover and filter case sides.

INSTALLATION OF NEW FILTER ELEMENT

1.

2.

3.

Install new filter element

Install new spiral gasket and swing filter case cover closed

Install case cover retaining studs and nuts. Torque nuts to 100 ft-lb

(135.6 N·m) torque

4.

5.

Replace cap on drain line & close hand valve VH902-3 or VH902-4

Leak check filter by opening hand valve VH903 slightly to allow transfer of oil into filter.

6.

7.

8.

When oil is seen draining from hand valve VH902-1 or VH902-2, close hand valve VH902-1 or VH902-2 and then close valve VH903.

Do not transfer oil filter to operating lube oil system until all air has escaped from filter body.

Move transfer valve VT901 to desired position.

If required, repeat procedure for second filter.

2.4.7 Gas Turbine Enclosure

The gas turbine enclosure is designed and constructed primarily to provide acoustic attenuation of the noise emissions from the gas generator and the gas turbine, and to meet hazardous area limitations. The enclosure is constructed in a panel form to provide maximum access for maintenance. All side panels can be removed. One plain end panel is nominated for electrical/instrumentation equipment and hook-up. The end panels around the drive coupling are split for access/installation to the drive coupling if required.

The roof panel is fixed and has a number of penetrations for each pipework and ducting.

Personnel access doors are provided in each side of the gas turbine enclosure for periodic maintenance and inspection. An access hatch is also provided for easy access to the intake collector duct.

Each door is fitted with a lock and an internal panic release, which is able to override the door lock if the door is inadvertently closed and locked.

An internal lighting system is fitted and operated by two-way switches located between each pair of doors. Mains and emergency lighting is installed for maintenance. The enclosure is fitted with a ventilation system to reduce the temperature within the enclosure.


Gas Turbine Enclosure Ventilation System

The GT enclosure ventilation system maintains a negative pressure of (-)700

Pa inside the enclosure; a maxim um air outlet temperature of 39ºC and a maximum inlet temperature of 25ºC. The intake system and silencer allows clean air to be drawn in through the filters and into the enclosure. All construction is in grade 316L stainless steel. The ventilation exhaust system includes 2 x 100% AC axial flow fans, an exhaust silencer, gravity exhaust louvre interconnecting ducting and a flexible connection to the GT Enclosure.

Shut-off dampers are provided at the inlet and outlet to the enclosure. The damper is automatically closed by the LER fire protection control panel, preventing system airflow if a fire occurs.

Gas Turbine Enclosure Ventilation Intake System

Two axial flow fans located within the ventilation exhaust ductwork provide cooling air for the gas turbine enclosure. One fan only is used in normal operation; the second fan provides a stand-by facility in the event of a fan failure. The air is drawn from atmosphere into the intake filter system. The system comprises of two stages. The first stage – storm-proof weather louvre and the second stage - GT2 bag filter.

Water drainage 'U' traps are provided in the base of the weather louvre. The filter house has a side access panel for filter withdrawal for maintenance: access to the panel is achieved by use of the platform adjacent to the filter house. A vent intake system silencer reduces the noise emissions from the gas turbine enclosure. The silencer is specifically designed to meet the system flow rates and noise levels generated by the gas turbine. The airflow from the silencer passes through an elbow and into the gas turbine enclosures. A flexible connection is installed at this interface to the enclosure for isolation and alignment of the equipment. An intake shut-off damper is provided on the inside of the Enclosure.

Gas Turbine Enclosure Ventilation Exhaust System

An exhaust shut-off damper is fitted inside the enclosure, at the air outlet connection on the gas turbine enclosure. When the CO

2 system is activated the shut-off damper will close sealing the enclosure ventilation apertures. An exhaust flexible is fitted for isolation and alignment of the equipment. The main and standby fan assemblies are mounted onto the end of the elbow duct. The vent fans are supported between the elbow and silencer transition.

The lower elbow has adjustable support brackets for use during fan removal.

The fans take the exhaust air into the exhaust silencer. The fans are fitted with a flow or no-flow status device. Each fan has a local emergency stop button. System Instrumentation monitors:

Combustion Intake Filter Condition

• Filter differential pressure gauge - local indication/monitor

• Filter diff pressure (high) transmitter - alarm/trip with LCD display

GT Ventilation System, Filter Condition and Air Flow Status

• Filter differential pressure gauge - local indication/monitor

• Filter diff pressure transmitter - local indication/monitor & LCD display

• Flow failure switch - alarm/control

GT Enclosure Pressure & Temperature

• Operating pressure transmitter - MCC & local indication / monitor

• Operating temperature - resistance temperature detector - alarm


2.4.8 Gas Turbine Local Control Room & LER

The electrical control system operates on 24V dc power and provides automatic starting, acceleration to operating speed, engine and driven equipment monitoring during operation and normal and emergency

(malfunction) shutdown. The system also controls safe operating parameters such as temperatures, pressures, flow, speed and vibration. Start-up and shutdown also require controlled sequenced processes.

The control system is operated from the local control room, which has a turbine control panel, with all the necessary switches, pushbuttons and indicators for engine operational status on the front; plus a programmable logic controller (PLC) and a computer adapted for control tasks which controls the turbine engine package systems. The PLC reads inputs such as control panel pushbuttons, makes decisions and sets the outputs such as indicators, positioners, or heating coils. Pressure and temperature sensors, speed, vibrations, pick-ups and other sensors, transfer measured data to the

PLC which evaluates the inputs and sends commands to control devices.

Communication modules accommodate data transmission between control system devices using dissimilar data formats.

The local control room is located above the 4 th water injection pump and performs various operations of the turbine package. It contains:



Batteries & Charger



Turbine Control Panel



Motor Control Centre



Variable Frequency Driver



Fire and Gas Panel



HVAC System

The Local Equipment Room (LER) provides a stand-alone self-contained room to house the equipment for the various operations of the turbine package. The LER structure is built on a carbon steel base raised at one end to allow the LER to be positioned clear of pipe work. The main walls are stainless steel outer, thermally insulated with Rockwool and finished internally with ‘Capeboard’. The main elements of the LER are as follows:



External weather cowls to inlet and exhaust



1 no. multivane coalescer / water separator



1 no. air filter



2 no pneumatically operated fire dampers and 2 fans /motors.



1 no 3 kW duct heater with T3 rating



EE xd pressurisation/F&G control panels with alarm outputs

 Fireman’s panel: includes vent valve & air supply regulator assembly



2 no. Eexi fan speed sensors



2 no. Eexd local fan motor isolators



External high gas purge button

The turbine is remotely controlled and monitored from the CCR.


LER Ventilation / Pressurisation

Two EE xd pressurisation fans (duty and standby) are located internally within the floor void. A connecting duct on the intake side joins the fans. Air is drawn through an external cowl located at the base of the LER. Air then flows through a coalescer, fore damper and filter before entering the intake plenum that connects both fans. Air passes through the duty fan and is expelled in to the supply duct, through a non-return back draught damper and finally through the 3 kW heater before entering the floor void. From the floor void air passes through two ventilation panels.

The pressurisation system maintains a positive pressure within the LER during normal operation. The fans deliver airflow of 0.1 cubic meters per second, which allows 12 air changes per hour within the LER. The pressurisation and ventilation system is primarily controlled from a pressurisation/F&G system comprising two EE xd rated panels. The control panel also interfaces with F&G devices within the turbine enclosure.

Either fan may be selected as the duty fan. It is possible to change the duty fan even when the system is running in normal mode. Engaging the start button on the panel starts the system. The fire dampers open and allow airflow and pressure to establish and the system energises the control power at the two MCCB (Motor Controller Centre Breaker) panels, ready for manual activation by the operator. If the duty fan fails the system will automatically changeover to the standby fan. A HVAC common fault output signal will also be activated so that the correct procedure can be followed to repair the failed fan. If there is a loss of LER air pressure or airflow, the system alarms for a period of 30 seconds (adjustable at the PLC controller in the control panel).

After this time the fire dampers are closed and the duty fan is stopped.

Gas Purge of LER

The LER must be purged occasionally to remove any residue gases. There is a keyswitch fitted in the local control panel and also remotely on the exterior of the LER for this function. Engaging either switch will open the fire dampers and run the selected duty fan for an indefinite period. When the gas has been purged the keyswitch is returned to the normal position and the normal start-up sequence initiated. During gas purge, gas levels are monitored at the control panel.

LER Gas & Smoke Detection

If 20% LEL gas is detected in the LER the system alarms. If 60% is detected the system will alarm, close the fire dampers, and stop the duty fan. If smoke is detected in the LER the system will alarm, close the fire dampers and also stop the duty fan (refer to Solar Installation & Maintenance Manual

104.471.253 Volume 3 for details regarding HVAC system).

The selector switch on the control panel must be set to Fan 1 or Fan 2.

Either fan can be selected as the duty fan while the other becomes the standby fan. To run a fan for duty the start button must be pushed to commence the purge period, then the selected fan will energise. The LER exhaust inlet and exhaust dampers then open and the damper status will be displayed on the screen. The fan will run when the fan speed has increased through the RPM monitor set point.


2.4.9 Gas Turbine Enclosure Fire Protection System

A CO

2

deluge system is provided for emergency use should a fire be detected within the turbine enclosure and comprises this equipment:

 An extinguishant skid complete with bottles, weight monitoring, valves and actuation/monitoring electrical equipment





Piping with isolation valve and position switches

Discharge nozzles (positioned within the acoustic enclosure)

Extinguishing agent

Type of system

Actuation method at the skid

System operating pressure

Extinguishant quantity

Engine requirements

Fire Zone

Carbon dioxide

Total flooding a) Electrical solenoid actuator/Pilot nitrogen b) Manual lever actuator c) Refer also to electrical operating instructions covering field devices and the control system (Altair operating manual 90398/L1327)

51 barg at 20 o C

45 kg capacity per cylinder

2 initial cylinders + 2 reserve cylinders

(each with a nitrogen Pilot cylinder)

258

GT Enclosure CO

2

Fire Protection System

A How Fire CO

2

Fire Protection System is provided for the 7.3m long x 3.0m high x 2.7 m wide turbine enclosure which complies with NFPA 12 or BS 5306

Part 4. The system comprises:



CO

2

Fire Protection System and CO

2 bottles (by How)



Field Run Pipe work (by WG / others)



Turbine Enclosure CO

2

Distribution System with nozzles.

The enclosure is fitted with seven personnel access doors. Visual indication is provided locally, one on each side of enclosure. A CO

2 lockout switch is provided each side of the enclosure should access to the enclosure be necessary whilst the engine is running. The status of lockout is visually indicated locally and in the CCR. Indications include:



System on Automatic Control (green)



System on Manual Control (amber)



System Operated - 1st shot (red)



System operated -2nd shot (red)



System Locked Out - (amber)

CO

2

fire protection system audible and visual alarms are installed on each side of enclosure. The CO

2

cabinet is fitted with extinguishant bottle rack and associated process hardware, and is located adjacent to the Gas Turbine

Enclosure. All equipment is suitable for open deck duty in a marine, offshore environment. The fire & gas panel in the LER controls the operation of the

CO

2

system.


Each cylinder is connected to an overhead manifold using flexible discharge loops; each manifold port is fitted with an adapter and a check valve. The adaptor is fitted prior to the check valve to provide a 3/16” flexible pilot loop connection to the relevant discharge pressure switch (initial/reserve). The check valve allows for cylinder removal whilst maintaining operation.

The manifold incorporates further check valves (100% redundancy) to allow for positive differentiation between initial and reserve discharge signals. The control/monitoring system is programmed to initiate reserve cylinder discharge if confirmation of gas in the pipe is not received within 5 seconds from instruction to release the initial system. The collector manifold is piped to both sides of the skid, offering options for field pipe work connection, with the unused port remaining plugged. The manifold is connected to a network of discharge pipe work and nozzles.

Connections are provided off the CO

2

pipework to operate dampers. An isolation ball valve is installed within the discharge pipe work outside the protected area at an accessible level. This device allows the CO

2

supply to be manually isolated. The ball valve is supplied with limit switches to provide electrical confirmation of operation (open and closed) back to the turbine control/monitoring system.

Note: The CO

2

bottles are clamped to allow for movement of the ship. The bottles are weighed periodically during calm conditions; the bottles are unclamped to allow counterweights to confirm the bottle ’s weight (details relating to the weight monitoring system can be found in the Altair operating manual 90398/L1327).

GT Enclosure Fire & Gas Detection System

The primary means of fire detection within engine compartments is electromechanical rate-compensated heat detectors located in the engine compartment between ventilation air inlet and outlet ducting, and in the vent exhaust duct.

To accommodate abnormal operating conditions (which could render the detectors in the ventilation outlet ducting ineffective) additional detectors are located in the engine compartment. 2 out of 3 voting is used.

Secondary fire detection is by optical beam smoke/oil mist detection

(Wormald model 6003/7). This is primarily for the detection of a release of lube oil or diesel, or the early stages of combustion, and comprises a single detector in the engine enclosure viewing across the ventilation air outlets.

The turbine enclosure is also protected with a gas detection system. Three

Infrared point-type detectors are installed at each of the following locations:



Combustion Air Intake



Ventilation Air Inlet



Ventilation Exhaust


Figure 4 4 th Water Injection Pump Package Fire & Gas Detection System Cause & Effect Chart


Z-8000-BB-4076 Rev Z1 20 January 2005

Figure 5 4 th Water Injection Pump Enclosure showing Fire & Gas Detectors

Page 33 of 158

2.4.10 Wash Cart

Contaminants such as dust, oil and salt can pass through the air filters and adhere to the compressor blades thus decreasing engine performance. The wash cart is used to supply demineralised water to the turbine for ingestive cleaning to help eliminate performance problems:









Failure to accelerate to full speed/general lack of acceleration

Compressor surge/ loss of compressor discharge pressure

Inability to develop full output power

Increase in turbine temperature.

To determine if cleaning is required, engine performance is evaluated using the following parameters:



















Gas producer speed (Ngp)

Compressor inlet temperature

Barometric pressure

Turbine gas temperature

Compressor discharge pressure

Output power

Inlet and exhaust duct pressure drop

Water injection rate

Fuel gas flow/usage.

When to clean is best determined by measuring performance loss. A rule of thumb is to clean before a 10% reduction in power occurs or the power turbine temperature increase by 5% or there is a 8-10% reduction in output power. Baseline conditions (output power and air inlet temperature) should be used for comparison. Deposits should not be allowed to accumulate, otherwise water-washing will become ineffective over time.

Water is used to remove water-soluble contaminants. Cleaning can be carried out while the engine is cranking ( on-crank cleaning ) or while the engine is operating in the simple cycle ( on-line cleaning ). On-crank cleaning is when the engine operates at the maximum speed obtainable by the starter alone with the fuel and ignition de-activated (providing turbine gas temperatures are below 66 o C and/or gas producer speed is below 60%).

This type of cleaning is more effective than on-line cleaning. On-line cleaning is when the engine operates at any power level ranging from idle to full rated power with the temperature stabilized at operating speed.

Wash Cart Components

The wash cart is a horizontal stainless steel pressure injection vessel, which is plumbed in to the on/crank / water wash and online manifolds. The tank is constructed to the Pressure Vessel Code ASME VIII specifications and PER

/PED for a normal working pressure of 6.9 barg and up to 95 o C. In addition to this the cart has the following components:











ASME UV stamped pressure relief valve set at 8.95 bar

Tank capacity of 26 gal (100L)

On-crank air and on-line air, water and chemical inlet ball valves with check valves

Air, water and chemical Y inlet strainers with 100 micron insert

Wash fluid outlet connection with ball valve


















Wash fluid outlet filter Y strainer with 100-micron filter insert

Drain and vent with ball valves

Magnetic level gauge with dial face

Heavy-duty chemical-resistant hose with female quick disconnects between injection tank and engine on-crank manifold ring and water/chemical supply

Heavy-duty hose with female quick disconnect at each end for air supply to tank

Hand-held spraying wand

Pressure Safety Valve (PSV)

Male quick-disconnect couplers for air, water and chemicals.

Figure 6 4 th Water Injection Pump Turbine Wash Cart (without PSV)

There are two separate skid edge connections; one for on-line cleaning and the other for on-crank cleaning. Each connection is plumbed to the respective manifold with the following components:









Inlet strainer

Shutoff solenoid

Triple cartridge filter

Three-way hand valve (on-crank only).

The on-crank three-way hand valve is downstream of the shutoff solenoid with a quick disconnect for the hand wand. The control system logic prevents the on-crank solenoid from opening when the turbine gas temperatures are above 66

°

C and/or the corrected gas producer speed is above 60%.


2.5 Water Overboard Discharges, Monitoring & Reporting

Not all overboard discharges from the Schiehallion FPSO process systems are monitored for oil-in-water content, but this does not mean that oily water is disposed of indiscriminately. There are several discharges to sea that could contain oil:

 Produced Water Degasser outlet (20”) discharge overboard



Deaerator Tower outlet (10”) overboard discharge & 3” drain



Water Injection Pumps (10 ”/14”) overboard discharge

For each discharge the information required for reporting is as follows. o Average monthly oil-in-water quality in ppm (wt) - by sampling o Average discharge rate in m 3 /day and number of days on stream o Total volume of water discharged in m

3 o Weight of oil discharged in tonnes.

The Degasser 20” overboard discharge oil-in-water content is determined by sampling on the Degasser outlet. An oil-in-water analyser provides continuous monitoring and initiates a high oil-in-water alarm if 30 ppmv oil-inwater is exceeded.

The De-aerator Tower V-44101 10” overboard discharge FCV-441019 controls the water flow overboard using a FIC which controls the flow through the tower by modulating the tower seawater inlet to match water injection demand. This opens the FCV which dumps water to sea to maintain a minimum flow through the tower. The 3” De-aerator drain is isolated by a manual valve and is only used for maintenance.

Each motor-driven water injection pump P-45001A/B/C 10” discharge has a

6” branch line FCV, which is modulated according to injection system demand. Supply overdemand will open each pump’s respective discharge

FCV and discharge water into a common 10” discharge line with vent and through the 14” discharge pipe overboard. There is no flow monitoring or sampling on this common line.

Minimum flow protection for the GT-driven pump is provided by an overboard dump valve FCV-450445 which opens at a predefined minimum flow of 330 m 3 /h to protect the pump from damage.

The quantity discharged overboard is determined by calculation in the CPS, being the difference between the total flow through the water injection pumps

(integrated over the same time period), less the amount discharged down the water injection risers:

{ Integration of (FI 450145 + FI 450245 + FI 450345) }

- (FQI 180800 + FQI 182800)

Quantity is displayed at FQI-450004.

All environmental discharges from Schiehallion Installation are published on the Schiehallion website.


Z-8000-BB-4076 Rev Z1 20 January 2005

3 ” Overboard

10 ”

10 ” Overboard

Figure 7 Water Injection System Schematic

Page 37 of 158

2.6 Chemical Injection

Antifoam, biocide and calcium nitrate may be injected at the inlet to the deaerator. A scale inhibitor injection point is provided at the outlet. Refer to Z-

8000-BB-4007 for details of the chemical injection system.

The biocide and anti-foam injection point is a common line. Biocide dosing must only occur when the deaerator tower is off-line to prevent foaming in the column and to ensure that biocide is not routed to the reservoir where it could negate the benefit of calcium nitrate injection. To maintain the quality of the injection water, scale Inhibitor may be required to be injected at the outlet of the deaerator on a continuous basis to avoid the scaling subsea which would result from the mixing of the produced water and seawater. Any scales formed would be pumped into the reservoir. Antifoam can be injected if required at the deaerator inlet. The chemical dosing rates are:

Antifoam

Scale Inhibitor

2 ppm (normal)

5 ppm (normal)

Oxygen Scavenger 5 ppm (normal)

Calcium nitrate 60 ppm (this will vary as the produced water make increases)

The de-aeration system is designed to be capable of meeting the required oxygen specification without the use of oxygen scavenger injection. However, rough weather may cause poor distribution of seawater in the deaerator column causing the unit to go off specification. Under these circumstances, the column may be returned to specification by the injection of oxygen scavenger chemical, which is fed into the tower by mixing via a 2” line from the discharge of the produced water booster pumps P-43001A/B/C.

The chlorine analyser AT-441017 and the oxygen analyser AT-441018 monitor water quality at the outlet of the deaerator. A manual sample connection is also provided. Sodium hypochlorite is injected to the seawater lift pumps

P-85401A/B/C suction and should not exceed 2 ppm(wt) of free chlorine. The maximum oxygen level is 20 ppb.

The chlorine analyser AT-441017 is located in a purged cabinet. The purge gas pressure is maintained at a constant pressure by an integral flow controller within the purge system control unit, which is located in the field. In the event that the purge pressure exceeds or falls below the set operating pressure then an alarm will be generated PAH/L-441034 by a pressure switch located in the purge cabinet. Initiation of this alarm will cause the power to the instrumentation within the purged cabinet to be isolated by the purge system control unit.

To safeguard against any leaks in the purged cabinet, a liquid level instrument is located at the bottom of the drip tray. In the event of liquids leaking into the cabinet, an alarm LAH-441033 will be generated by the level switch LS-441033.

Initiation of the alarm will remove power from the instrumentation within the purged cabinet. This is controlled by the purge system control unit.


2.7 Turret Water Injection, Swivel and Turret Valves

Refer to P&ID M-5021-GP-8004.00.

The 16” line containing produced water and de-aerated seawater from pumps P-45001A/B/C/D is discharged at approx. 22

°

C and up to 246 bar via a dedicated pressurised 12” turret water swivel N-45080 to three 10” risers. The injection water then flows to the subsea distribution system.

PG-450803 is located downstream of the turret.

The 12” water injection manifold in the turret has four connections. One is for future use and is currently blanked off. The re maining 12” line connects to three

10” nominal bore risers. Each 10” line has two sonic flowmeters (FE-180800A/B,

FE-181800A/B & FE-182800A/B), check valves (with 2” bypass to allow depressurisation of the downstream pipeline), local flow indicators, and 10” isolating valves. The three 10” risers then connect to two 9.5” ID flexible risers and one 11.5” ID flexible riser to form part of the subsea water injection distribution system.

2.8 Water Injection Flexible Risers

The two 9.5”ID risers connect at their bases with plastic-lined pipelines to

Schiehallion Central & North, and to Loyal and West via North. The third 11 .5”ID riser connects at its base with plastic-lined pipeline to Schiehallion North West.

Refer to P&ID M-5021-GP-8004.

Water from the turret’s 12” water injection manifold is passed down three

10” nominal bore flexible risers, each lined with a carcass to protect against vacuum conditions on injection pump shutdown. When the pumps are shut down, it is expected that the hydrostatic pressure in the risers will exceed water injection well(s) pressure. Closing the injection wells’ wing valves when the water injection pumps are shut down will minimise the likelihood of vacuum conditions occurring in the risers.

The unbounded flexible pipe structure is built with the specific arrangement of coaxial layers of different material. Each layer has its own function that helps the flexible system to fulfil its main functional requirements. The basic design used for the Schiehallion water injection lines is a smooth bore structure, because no gas is involved in the transport fluid and it remains full all the time. The structure comprises of the following layers:



Layer 1: Inner plastic tube for pipe leak resistance.



Layer 2: Spiralled steel layer to sustain the radial load generated by the internal pressure.



Layer 3: An anti-collapse thermo-plastic sheath to submit the external pressure onto the underlying steel layer - most of the time this layer is not needed if the line remains full of the fluid.



Layer 4: Cross-wound armoured layers to withstand tensile and torque loads.



Layer 5: External thermo-plastic sheath to ensure the leak resistance to environmental fluid.



Layer 6: Anti-friction layers for dynamic application.

The flexible risers and the flowline jumpers have essentially identical construction, with an inner carcass of Grade 316L austenitic stainless steel, which supports a pressure sheath of polyamide, or, for the WI risers, PE. The inner layers are mechanically protected by a hydrogen sulphide-resistant external wire armour layer, with polymer coating layers.


Riser Group Drill Centre

Schiehallion

Central

Schiehallion

West &

Gas Disposal

Loyal &

Schiehallion

North

Schiehallion

Central

Schiehallion

West

Gas Disposal

Loyal

Schiehallion

North

North West North West

Drill Centre Duty

Production wells

Water injection wells

Production wells


Gas disposal well

Production wells


Water injection wells only

Production wells


Riser/Flowline

Service

Production line A

Production line B

Production line C

Production/Test

Gas Lift [1]

Water Injection

Umbilical

Production

Production/Test

Gas Lift [1]

Water Injection [2]

Umbilical [4]

Gas Disposal

Umbilical [4]

Spare Riser Base

Gas Lift

Production

Production/Test

Gas Lift

Water Injection [2]

Umbilical [3]

Water injection

Umbilical

Production

Gas Lift [5]

Water injection

Umbilical [6]

Riser

NB

(in)

9.5

9.5

9.5

7.5

-

9.5 n/a

9.5

7.5

-

-

-

7.5

-

5

9

9.5

7.5

7.5

-

-

9.5 n/a

9.5

-

11.5

-

Table 2 Water Injection Flowlines & Umbilicals Dimensions

Notes: [1] Gas lift lines branched off Loyal Line

[2] Loyal and Schiehallion West Water Injection Line Branches off Schiehallion North

[3] Loyal Umbilical Branches off Schiehallion North

[4] Schiehallion West & Gas Disposal Umbilical Branches off Schiehallion Central

[5] North West gas lift is from West drill centre (HOLD)

[6] North West umbilical is from West drill centre (HOLD)

10

8

6

10 n/a

10 n/a

10

8

10

-

Flowline

NB

(in) length

(km)

10

10

10

8

8

12 n/a

10

8

6

10 n/a

8 n/a

2.65

2.65

2.65

2.65

2.90

2.65

2.630

4.30

4.30

4.75

4.80

2.989

9.30

5.009

5.90

5.90

5.90

4.90

4.920

2.40

2.313

6

2

2

2

2.9 Subsea Water Injection System

Refer to P&IDs S-9000-NP-9203/13/14/15/16/20/21/24/25/26

Subsea Water Injection System Equipment

The subsea water injection system consists of three sets of equipment: the first to deliver injection water to Schiehallion Central, the second to deliver injection water to Schiehallion West, North and Loyal, and the third (HOLD) to deliver water to the new North-West Drill Centre. Water delivered to these drill centres should have been filtered and the oxygen removed to the following specification:

Dissolved Gases

Maximum particle size

Negligible, i.e. < 20 ppb O

2

80 microns.

Each drill centre is supplied by a dedicated flowline, except for Schiehallion North and Loyal centres which share a flowline between the riser base and the North

Injection site. Distribution to individual wells is via a water injection manifold at each drill centre.


Injection rates to individual wells is controlled at each injection wellhead by ROVoperated chokes with flow control provided by shutting in components of the system - either individual wells or one of the four injection pumps. For operation of the first two injection wells, the pump minimum flow FCVs also serve to control the pump flow. The design is aimed at infrequent adjustments to the water injection rates; the rates being monitored using a venturi-type flowmeter which is mounted at each wellhead, upstream of the injection choke.

Note: If ROV control of the injection chokes provides insufficient operational flexibility, there is an option to provide actuated chokes on the later water injection trees with some impact to the control systems.

Schiehallion Central

Schiehallion Central is located some 2.9 km South East of the FPSO. The eight water injection trees are supplied ind ividually from the 12” plastic-lined flowline via two water injection manifolds M2 & M2A which are connected to the pipeline FTA using 10” flexible jumpers. Each water injection tree is connected to the manifold by a 6” flexible wellhead jumper.

Electro-hydraulic control functions and chemical supplies for the central manifold and the production and water injection trees are provided by a control umbilical from the FPSO. These services are distributed through the Controls Distribution

Trunking (CDT) which forms the upper section of the central manifold. The water injection tree controls are supplied by two separate umbilicals, connected to separate outlets on the CDT, each supplying an SCM on an injection tree, each of which in turn controls another injection wellhead by direct hydraulic control.

Schiehallion West

Schiehallion West is located 3.2 km to the South West of the FPSO and has five water injection wells. The wells are connected to the F PSO by 10” & 12” plasticlined rigid flowlines. These flowlines are terminated by FTAs at both ends. The water injection supply is provided from a 10” riser and a 12” riser via two FTAs, located beneath the FPSO, which supplies Schiehallion North and Loyal. The five water injection trees are supplied individually from the 10” & 12” plastic-lined flowlines via two connected water injection manifolds M22 & M22A; these are connected to pipeline FTAs with 10” and 12” flexible jumpers. The water injection tree controls are supplied by an umbilical jumper from the UTA to an SCM on one of the trees. This provides direct hydraulic control functions for all water injection trees.

Schiehallion North

Schiehallion North is located some 2.7 km to the North East of the FPSO and has three water injection wells. The wells are supplied with injection water through a

10”, plastic-lined flowline from the FPSO through a three-porch water injection manifold via 6” bore flexible wellhead jumpers. The flowline also extends via a

10” flexible jumper from one end of the manifold to the FTA on the end of a 10” plastic-lined pipeline which is routed to the Loyal wellsite. Control functions to the trees are provided from a UTA to an SCM on one of the trees. This controls the other tree using direct hydraulics, and has a spare connection for the third tree.


Loyal

Loyal is located 6.1 km North of the FPSO and has four water injection wells.

The water injection supply is provided from the FPSO by a 10” flowline which is routed via the Schiehallion North manifold. The four water injection trees are supplied individually from the 10” plastic-lined flowline via a separate four-porch water injection manifold which is connected to the pipeline FTA with a 10” flexible jumper. The water injection tree controls are supplied by an umbilical jumper from the UTA to the SCM on one of the trees. This provides direct hydraulic control to the other three water injection trees.

From Water 16

”

Injection

Pumps P-45001A/B/C/D

12

” Water Injection

Swivel N-45080

12

” Water Injection Manifold

FTA

9

½” ID

Flexible

Riser

FTA

Central Manifold

Schiehallion

Central WI Wells

FTA

9

½” ID

Flexible

Riser

Future Riser

Connection (blanked off)

FTA

11

½” ID

Flexible

Riser

Injection water to North-West Drill

Centre (HOLD)

FTA FTA

North Manifold

Schiehallion

North WI Wells

West Manifold

Schiehallion

West WI Wells

FTA

FTA

KEY

Riser

Jumper

Flowline

Loyal

WI Wells

Figure 8 Subsea Equipment Schematic (prior to NW drill centre development)


Components Location

Common Water Injection manifold Turret

One spare connector (for future use) Turret

Schiehallion Central – Water Distribution System

Schiehallion Central Riser (slot EC )

Schiehallion FPSO FTA

Flowline (FPSO FTA to Central FTA)

Schiehallion Central FTA (WI)

Flexible Jumper to Central Manifold

Central Water Injection Manifold

Flexible Jumper to Tree on Slot CW12

Water Injection Tree on Slot CW12 (Type 1)









Flexible Jumper, Central Manifold M2 to Manifold M2A


Water Injection Tree on Slot CW17 (DTHT)





Central

Central

Central

Central

Central

Central



Central

Central

Schiehallion West, North & Loyal – Distribution System

Under FPSO seabed

Seabed

Central

Central

Central

Central

Central

Central

Central

Central

Central

Central

Central

Central

Central

Central

West, North & Loyal Riser (Slot NF)

FTA FPSO

Flexible Jumper to FTA-185-92

FTA FPSO to West WI

Flowline to West FTA

FTA West WI

Under FPSO

Seabed

Seabed

Seabed

West

West

ID No

12”-WI-450803

-

10-R-180

FTA-180-92

12 ”-L-180

FTA-180-93

10-J-180

MAN-180-92

06-W-105-922

XTI-105-92P

06-W-105-923

XTI-105-92Q

06-W-105-921

XTI-105-92N

06-W-105-924

XTI-105-92R

06-W-105-923

XTI-105-92T

10-J-180-921

06-W-105-927

XTI-105-92U

06-W-105-925

XTI-105-92S

06-W-105-928

XTI-105-92V

06-W-105-929

XTI-105-92W

Flexible Jumper to West Manifold M22

West WI Manifold

Flexible Jumper to Tree XTI-125-92Q

Well WW05 Water Injection Tree (Type1)

Flexible Jumper to Tree XTI-125-92P

Well WW04 Water Injection Tree (Type1)

Flexible Jumper to Tree XTI-125-92N

Well WW06 Water Injection Tree (Type 3)

Flexible Jumper to West Manifold M22A

Flexible Jumper to Tree XTI-125-92R

Well WW08 Water Injection Tree

Flexible Jumper to Tree XTI-125-92S

Well WW09 Water Injection Tree

Flexible Jumper from West FTA-185-96 F29

West

West

West

West

West

West

West

West

West

West

West

West

West

West

10-R-182

FTA-182-92

10-J-185-921

FTA-185-92

10-L-185

FTA -185-93

FTA 26

10-J-185-93

MAN-185-92 M22

06-W-125-923

XTI-125-92Q

06-W-125-922

XTI-125-92P

06-W-125-921

XTI-125-92 N

10-J-185-923

06-W-125-924

XTI-125-92R

06-W-125-925

XTI-125-92S

12-J-185-926

Table 3 Subsea Components and Sizes (prior to NW development)

Size

12"

12 ”

6”

N/A

6”

N/A

6”

N/A

6”

N/A

9.5”

10”

10”

10”

10”

10”

10”

10”

6”

N/A

6”

N/A

6”

N/A

10”

6”

N/A

6”

N/A

12 ”

9.5

”

10 ”/12”

12 ”

12”/10”

10”

10”

6”

N/A

6”

N/A

6”

N/A

6”

N/A

6”

N/A

10”


Schiehallion North & Loyal - Distribution System

Flowline to North FTA

FTA North WI

Flexible Jumper to North Manifold

North Water Injection Manifold


Water Injection Tree NW02 (Type 1)





Flexible Jumper from North Manifold to

FTA-186-92

Flexible Jumper from FTA-186-92 to

Loyal FTA-186-93

Flexible Jumper from FTA-186-93 to

Loyal FTA-186-92

Loyal Water Injection Manifold


Water Injection Tree LW06 (Type 1)





Flexible Jumper to Tree XTI-145-92R

Water Injection Tree LW04

North

North

North

North

North

North

North

North

North

North

North to Loyal

North to Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

Loyal

10-L-182

FTA-182-93

10-J-182

MAN-182-92

06-W-135-922

XTI-135-92P

06-W-135-921

XTI-135-92N

06-W-135-923

XTI-135-92Q

10-J-186-921

10-L-186

10-J-186-922

MAN-185-92

06-W-145-923

XTI-145-92Q

06-W-145-922

XTI-145-92P

06-W-145-921

XTI-145-92N

06-W-145-924

XTI-145-92R

Table 3 Subsea Components and Sizes (prior to NW development)

(continued)

10”

10”

10”

10”

6”

N/A

6”

N/A

6”

N/A

10 ”

10 ”

10 ”

10”

6”

N/A

6”

6”

6”

N/A

6”

N/A

Normal Operation (Overview)

Once the chokes have been set by the ROV, the only operations will concern start up and shutdown of either the entire system or of individual wells. Fine tuning and optimisation of the water injection header can be controlled to an extent by the adjustment of surface-controlled choke valves on CW17, 18 and 19.

However, due to the design limitations of the water injection system, there will be a defined maximum operating flow rate for any component. This is to prevent over-pressurisation which can occur as a result of a hydraulic surge during an unplanned shutdown.

The relatively high pump discharge pressure of approximately 200 barg (3000 psig) at the design water injection rate has been aimed at overcoming uncertainties in the reservoir injectivity. Depending on the well injectivity and required injection rate, the pressure drop across the water injection chokes during normal operation could be high (i.e. up to 133 barg (2000 psig)). The system operating temperatures will also be relatively high (28 - 60



C). This is due to the injection of produced water, the use of the injection water as a cooling medium

(i.e. used in the topsides cooling medium coolers) and the polyethylene liner in the pipeline which provides a high level of insulation.


2 -3 /8 ” B y-P a ss T u b in g

N ip p le

P e rf. p u p a n d b u ll p lu g

T u b in g H a n g e r 7 ” x 2 ”, c/w 6 .1 8 7 ” p ro file

7 ” T R -S C S S S V

1 1 ¾ ” 6 0 lb /ft C a sin g

1 1 ¾ ” x 9 -5 /8 ” C ro sso ve r

9 -5 /8 ” 4 7 lb /ft L -8 0 C a sin g

7 ” 2 9 lb /ft o r 5 -1 /2 ” 2 0 lb /ft N S C C

T u b in g , L -8 0 , G R P L in e d

9 -5 /8 ” P e rm a n e n t P a cke r

(H y d ro s ta tic P re s s u re S e t)

5 1 /2 ” T a ilp ip e

S h e a ra b le T a ilp ip e C e n tra ils e r

L in e r T o p Is o la tio n V a lv e (L T IV )

5 ½ ” x 7 ” x 9 -5 /8 ” L in e r H a n g e r, P a cke r.

9 -5 /8 ” S h o e

5 1 /2 ” S a n d C o n tro l S cre e n s

(cro sse d o ve r to 7 ” T b g & H g r)

Figure 9 Typical Water Injection Well Completion Schematic

System Start up (Overview)

Start-up of the water injection system is based around ensuring the main water injection pumps are not started against a vacuum condition in the injection riser.

To achieve these aims, the produced water booster pumps or seawater lift pumps are employed to overcome any vacuum condition prior to starting the main pumps, but with the main pump discharge open to allow flow. If the well annulus pressure exceeds 275 barg, the wing valve will need to be closed before opening the cross-over valve otherwise it will not be possible to relieve sufficient pressure from the annulus.


System Shutdown (Overview)

On shut-down of the WI system there are four key considerations:



The potential for a vacuum condition in the water injection system due to reservoir under-pressure.



Hydraulic surge due to closure of the wing valves, with the potential for the shut-in pressure to exceed the system design pressure under certain circumstances and for the transient pressures during the shut-in process to exceed the maximum over-pressure allowances on some components.



Closure of the wing valves is required to ensure that cross-flow between injectors via the respective Xmas trees is prevented. Thus, reducing the potential for damage to the lower completion due to sand ingress. (Note that this is protected against to some extent by the use of sand screens within the water injection wells).



Excessive wear of WI wing valve if it is closed against the main pump.

Due to the above points, the shut-in of the wells is a compromise between the requirement to shut-in quickly to prevent a vacuum in the riser and cross-flow between wells and the requirement to shut-off slowly to prevent hydraulic surge in the system. To this end, any water injection trip will also close all subsea water injection wing valves with wing valve closure staggered over a period of 60 seconds to reduce the surge problem. This allows the run down of the pump and the closure of the pump discharge valve to occur before the closure of the last wing valve (once the water injection system is fully operational). The set point for opening the overboard dump valve on each pump ensures that the system pressure prior to shut down is relatively low – thus reducing the risk of over-pressure due to surge.

Protection of the wing valves against erosion is not possible and therefore closure against full operating pressure will occur under some circumstances. However, on a planned shut down of the water injection system, it is beneficial to close the wing valves and shut in pumps in a sequence that minimises the wear on the valves. To ensure that surge considerations are taken into account, safe operating limits for each well must be adhered to.

Corrosion Management

Refer to the Corrosion Management Strategy Z-8000-ZS-4027 .

The subsea components of the water injection system are constructed from corrosion resistant alloys. The flexible risers and flowline jumpers have a duplex carcass, the flexible well jumpers have a stainless steel 316 carcass, the carbon steel flowlines are provided with polyethylene lining and all other major components are alloy 625 clad carbon steel. Injection water is de-oxygenated to a level of <20 ppbv and OS-2 scavenger is employed, if required, to ensure that the sweet service design of the subsea system is satisfactory. During operation, corrosion management of the water injection system is limited to monitoring of the oxygen content of the injected water. There is no capability to intelligent pig the water injection system.

The well tubing is fibre glass-lined. However this lining can be damaged during well workovers giving the potential of the L80 carbon steel tubing to corrode. The maintenance of the water injection oxygen specification is primarily to protect against this corrosion potential.

No subsea chemical injection is required in the water injection system.


Injection of Oxygen Scavenger

These guidelines are used to determine when oxygen scavenger is required:

Oxygen Level (ppb O

2

) Duration Condition

< 20 ppb

> 20 ppb

50-500 ppb

> 500 ppb

-

> 2 hours

> 3 hours

> 1 hour

Normal Operations

Inject Oxygen Scavenger to bring down level

Shutdown Injection

Shutdown Injection

Table 4 Oxygen Scavenger Injection Decision Table

Scale Deposition

The potential for scale deposition is relatively low. However, to mitigate against the risk of deposition, the subsea system will be protected from scale deposition by the continuous injection of scale inhibitor on the FPSO.

2.10 Water Injection Wellheads (Tree, Choke, Master & Subsurface Valves)

Water Injection Tree Assembly (refer to P&IDs S-9000-NP-9203, S-9000-NP-

9220 & S-9000-NP-9221).

Three different types of water injection tree are installed subsea. The X-mas tree valving arrangement is the same for each tree, what does differ is whether a tree has a Subsea Control Module (SCM) and how many trees are controlled from that

SCM.

Type 1 has no SCM and control is via a Type 2 tree configuration

Type 2 has an SCM and controls one other Type 1 trees

Type 3 has an SCM and controls two other Type 1 trees.

Components

Slot Number

Tree Tag No.

SCSSV

UIMV

IWV

AMV

XOVT

Injection pressure & temp.

Annulus Pressure

WI Flowmeter

MP Hydraulic Supply

Pressure Sensor

HP Hydraulic Supply

Pressure Sensor

Schiehallion Central

CW12 CW13

XTI-10592P

105931P

105933P

105934P

105935P

105937P

PTT-105922P

XTI-10592R

105931R

105933R

105934R

105935R

105937R

PTT-105922R

PT-105923P

FT-105929P

PT-105991N

PT-105992N

PT-105923R

FT-105929R

PT-105991Q

PT-105992Q


CW16

XTI-10592T

105931T

105933T

105934T

105935T

105937T

PTT-105922T

PT-105923T

FT-105929T

PT-105991T

PT-105992T

Table 5 Type 1 Water Injection Wells


Components

Slot Number

Tree Tag No.

SCSSV

UIMV

IWV

AMV

XOVT

Injection pressure & temp.

Annulus Pressure

WI Flowmeter

MP Hydraulic Supply

Pressure Sensor

HP Hydraulic Supply

Pressure Sensor

PT-125992N

Components

Slot Number

Tree Tag Number

SCSSV

UIMV

IWV

AMV

XOVT

Injection Pressure & Temp.

Annulus Press. Sensor

WI Flowmeter

MP Hydraulic Supply Pressure

Sensor

HP Hydraulic Supply Pressure

Sensor

Schiehallion West

WW04

XTI-12592P

125931P

125933P

125934P

125935P

125937P

PTT-125922P

PT-125923P

FT-125929P

PT-125991N

LW05

PT-125992N

XTI-14592P

145931P

145933P

145934P

145935P

145937P

PTT-145922P

PT-145923P

PT-145929P

PT-145991N

PT-145992N

WW05

XTI-12592Q

125931Q

125933Q

125934Q

125935Q

125937Q

PTT-125922Q

PT-125923Q

FT-125929Q

PT-125991N

Loyal

LW06

XTI-14592Q

145931Q

145933Q

145934Q

145935Q

145937Q

PTT-145922Q

PT-145923Q

PT-145929Q

PT-145991N

Schiehallion North

NW02

XTI-13592P

135931P

135933P

135934P

135935P

135937P

PTT-135922P

PT-135923P

FT-135929P

PT-135991N

PT-135992N

PT-145992N

NW03

XTI-13592Q

13591Q

135933Q

135934Q

135935Q

135937Q

PTT-135922Q

PT-135923Q

FT-135929Q

PT-135991N

PT-135992N

Table 5 Type 1 Water Injection Wells (continued)

Component Schiehallion Central

Slot Number

Tree Tag Number

SCSSV

UIMV

IWV

AMV

XOVT

Injection Pressure & Temp.

Annulus Pressure Sensor

Water Injection Flowmeter



CW11

XTI-10592N

105931N

105933N

105934N

105935N

105937N

PTT-105922N

PT-105923N

PT-105929N

PT-105991N

PT-105992N


CW10

XTI-10592Q

105931Q

105933Q

105934Q

105935Q

105937Q

PTT-105922Q

PT-105923Q

PT-105929Q

PT-105991Q

PT-105992Q


Components West Loyal

Slot Number

Tree Tag Number

SCSSV

UIMV

IWV

AMV

XOVT

Injection Pressure and Temperature

Sensor




Sensor


Sensor

Components

WW06

XTI-12592N

125931N

125933N

125934N

125935N

125937N

PTT-125922N

PT-125923N

FT-125929N

PT-125991N

PT-125992N

LW04

XTI-14592N

145931N

145933N

145934N

145935N

145937N

PTT-145922N

PT-145923N

PT-145929N

PT-145991N

PT-145992N

North Central

Slot Number

Tree Tag Number

SCSSV

UIMV

IWV

AMV

XOVT

Injection Pressure and Temperature

Sensor




Sensor


Sensor

NW01

XTI-13592N

135931N

135933N

135934N

135935N

135937N

PTT-135922N

PT-135923N

PT-135929N

PT-135991N

PT-135992N

CW15

XTI-10592S

105931N

105933N

105934N

105935N

105937N

PTT-105922N

PT-105923N

PT-105929N

PT-105991N

PT-105992N


Components

Slot Number


CW17 CW18


CW19

Tree Tag No.

SCSSV

UIMV

IWV

XTI-10592U

105931U

105933U

105934U

XTI-10592V

105931V

105933V

105934V

XTI-10592W

105931W

105933W

105934W

AMV

XOVT

105935U

105937U

105935V

105937V

105935W

105937W

CHI 105926U 105926V 105936W

Injection pressure & Temp. Sensor PTT-105922U PTT-105922V PTT-105922W

Annulus Pressure Sensor PT-105923U PT-105923V PT-105923W

Injection Pressure Sensor

WI Flowmeter

Injection Choke Position Indicator

MP Hydraulic Supply Press. Sensor

HP Hydraulic Supply Press. Sensor

PT-105924U

FT-105929U

ZI-105926U

PT-105991U

PT-105992U

PT-105924V PT-105924W

FT-105929V FT-105929W

ZI-105926V ZI-105926W

PT-105991V PT-105991W

PT-105992V PT-105992W

Table 8 Type DTHT Water Injection Wells


Water Injection Tree Configuration

Refer to P&ID S-9000-NP-9203.

Each water injection tree has similar valves and instruments. The table below identifies valves which can be operated from the CCR and those valves which are

ROV operated. Remotely actuated valves are fitted with an override device which allows these valves to be operated by ROV if required. Injection Swab Valve and

Annulus Swab Valve are remotely operated from a workover vessel.

Component

WI Differential Pressure Flow Sensor

Injection Choke Valve

Injection Wing Valve (IWV)

Inlet Pressure & Temperature Sensor

Injection Swab Valve (SVI)

Annulus Swab Valve (ASV)

Crossover Valve (XOVT)


Upper Injection Master Valve (UIMV)

Annulus Master Valve (AMV)

Lower Injection Master Valve (LIMV)

Hydraulic Supply Valve to SCSSV

Surface Controlled Subsea Safety Valve

Remotely

Operated

N/A

CW17, 18, 19 only

Yes

N/A

Yes

Yes

Yes

N/A

Yes

Yes

No

No

Yes

ROV Operated

Table 9 Water Injection Tree – Valve Operation

N/A

Yes

No

N/A

No

No

No

N/A

NO

No

Yes

Yes

No

Note: Type 1 wells at the West, Loyal and North drill centres share the same control function on the subsurface safety valves. Hence, opening of the valve on one tree will also open the valve on the tree sharing this function, i.e. the following valves are operating by the same command:



SCSSV125931P and SCSSV125931Q



SCSSV135931P and SCSSV135931Q

This implies that the interlock sequences for these two wells are dependent on the position of valves on both Xmas trees.

2.11 Well Injectivity Decline

Injection of produced water can lead to a loss of injectivity of up to 40% relative to sea water injection. Generally, the “dirtier” the water injected, the greater the decline in injectivity. Thus, changing from produced water to sea water injection may restore original well injectivity. If a decline in well injectivity is experienced, it may be beneficial to revert to sea water injection for a period until injectivity rates are back to normal. During this time, all produced water would have to be discharged overboard. Further information on expected reservoir performance can be obtained from the Schiehallion Well Operating Handbook.

2.12 Water Injection Subsea Flowlines

The water injection seabed flowlines are rigid pipe of 10” diameter. A 1mm internal corrosion allowance has been included. No insulation is provided; however the pipelines are provided with a barrier coating for external corrosion protection. A system of sacrificial anodes supports the coating system.


2.13 Water Injection Wells

Water injection wells are not horizontal, but high angle. Flow calculations indicated that the majority of wells required 5 1/2” tubing, and some required 7" tubing, made of GRP-lined, carbon steel. Flow-wetted parts of crucial completion equipment such as the tubing-retrievable safety valve are made of 25% Cr for maximum reliability.

Other completion equipment is made of ceramic-coated carbon steel. Due to low reservoir temps (56°C), an expansion device is not required above the packer. If the wellhead is lost, downhole shut-in is achieved by a tubing-retrievable subsurface safety valve. In water injection wells completed below the oil-water contact (in a position where the well could not flow hydrocarbons if the wellhead was lost) the SSSV may be omitted from the completion. Nipples and profiles are included for testing the tubing, setting the packer and plugging the well for Xmas tree removal.

As in production wells the tailpipe below the packer is landed in a receptacle below the liner hanger. A permanent downhole gauge is not in the water injector as reservoir pressures can readily be calculated from wellhead pressures (which will always be higher than zero). For this purpose, a high-resolution injection xmas tree quartz gauge is specified.

Sand strengths are such that sand control is required in injectors to prevent sand fill due to possible cross flow during shut-in. sand control is achieved by using screens. On loyal, where sand strengths are slightly higher, cased and perforated injectors are installed instead, if necessary, for flow control.

Well Valve Status Date

IWV IMV SCSSV Date Time

CW10 Closed Closed Closed 03/05/2004 16:30

CW11 Closed Open Open 03/05/2004 16:30

CW12

CW13

CW15

CW16

CW17

CW18

CW19

WW04

WWO5

WWO6

WWO8

WW09

NW01

Closed

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Isol

Open

Open

Open

Open

Open

Isol

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Open

Isol

Open

Open

03/05/2004

03/05/2004

03/05/2004

03/05/2004

03/05/2004

03/05/2004

03/05/2004

16:30

16:30

16:30

03/05/2004 16:30

03/05/2004 16:30

03/05/2004

03/05/2004

03/05/2004

03/05/2004

16:30

16:30

16:30

16:30

16:30

16:30

16:30

16:30

NW02

NW03

LW04

LW05

LW06

Isol

Isol

Isol

Isol

Open

Open

Isol

Open

Open

Open

Isol

Open

03/05/2004 16:30

03/05/2004 16:30

03/05/2004 16:30

03/05/2004 16:30

Pressure after 1 hour

SIWHP (bar)

68.8

49.7

80.5

19.8

41.7

54.5

70.1

43.2

109.3

37

38.2

68.4

68.5

Isol Open Open 03/05/2004 16:30 99.2

Table 10 Pressure Fall-off Final Pressure Record – May 2004


Cluster

North

Central

West

Loyal

North West *

* Proposed

Slot name DTI Name

CW10

CW11

CW12

CW13

CW15

CW16

CW17

CW18

CW 19

WW04

WW05

WW06

WW07

WW08

WW09

NW01

NW02

NW03

LW04

LW04A

LW05

LW06

LW10

LW11

FP03

FP04

FW01

FW02

FW03

C08

C02

C04

C09

C14

C16

C19

WS29

C21

W06

W07

W03

W05

W08

W09

N03

N02z

N01z

L02

L02A

L05

L06

TBC

TBC

TBC

TBC

TBC

TBC

TBC

Table 11 Water Injection Wells Summary

Zone

T31a/T31b

T31a

T31a/T34/T35

T31a

T31 a

T31 a

T31 a

T31 a

T31a

T34a/T34b/T31a

T31qa

T31a/T31b

T31a

T31a

T31 a

T34

T31 a

T31a

T35b

T35b

T35

T35

Duty

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector

Water Injector


3. WATER INJECTION SYSTEM CONTROL PHILOSOPHY

3.1 De-aerator Tower V-44101 Control

The supply of seawater to and from the deaerator tower V-44101 is controlled by:



FIC-441001 (seawater inlet)



FIC-441019 (seawater outlet)



LIC-441010 (V-44101 seawater level).

During normal operation, the outlet flow from V-44101 (i.e. the demand of the water injection pumps P-45001A/B/C) is measured by FT-441019 and transmitted to FIC-441019.

FIC-441019 supplies a remote setpoint to FIC-441001 which modulates

FCV-441001, as required, to match inlet flow to outlet flow. LIC-441010 also has an input to FIC-441001 which affects the positioning of FCV-441001. In the event that the level in V-44101 falls below the setpoint of LIC-441010, this controller transmits a signal to FIC-441001 which tends to open FCV-441001 and increase the level in V-44101. Alternatively, when the level in V-44101 rises above the setpoint of LIC-441010 then a signal is transmitted which tends to close FCV-441001.

However, the operation of LIC441010 is ‘slow acting’ such that a small change in level does not immediately result in a signal being sent to FIC-441001.

FIC-441001 and FIC441019 are ‘fast acting’ controllers which are capable of responding quickly to changes in seawater demand and provide the main means of control of flow through V-44101. LIC441010 provides a ‘fine tuning’ control input which ‘smoothes’ the action of FIC-441001.

V-44101 has a 50% turndown capacity. When the demand of the water injection pumps P-45001A/B/C falls to less than 50% of the maximum throughput of

V-44101, the overboard dump valve FCV-441019 is opened, in response to a signal from FIC-441019.

Note: The control scheme described above ensures that the de-aeration system can cope with large changes in demand for seawater by the injection system.

FIC-441001 also provides output to the stroke control of the methanol injection pumps P-82601A/B to ensure that the amount of methanol injected for regeneration of the stripping gas (see below) is in proportion to seawater flow through V-44101. The calibration of the methanol pumps should be periodically checked to ensure that injection rates are correctly matched with seawater flow.

Refer to Z-8000-BB-4051 for details of the Methanol System.

Seawater outlet from V-44101 is continuously monitored for chlorine and oxygen content by AT-441017 and AT-441018 respectively.

Note: All actuated valves relay positional information to the CPS using limit switches, with the exception of control valves.


3.2 Stripping Gas Regeneration Control

The water injection stripping gas blowers P-44201A/B operate in duty/standby mode to draw stripping gas from V-44101. P-44201A/B suction pressure is controlled by the split level controller PIC-441021 which acts on PCV-441021

(vent valve) and PCV-441023 (nitrogen supply valve). Too high a suction pressure will cause PCV-441021 to open and relieve pressure via a local vent.

Too low a suction pressure will cause PCV-441023 to open and admit nitrogen into the suction line. The stripping gas supply to P-44201A/B is monitored by hydrocarbon analyser AI-441026 which will initiate and alarm if the hydrocarbon content of the gas exceeds a preset limit.

Instrument air must also be added to the stripping gas to ensure that the requirements of the de-oxidiser vessel reaction are met (i.e. sufficient oxygen is contained in the stripping gas to support the catalytic reaction in the de-oxidiser vessel). The addition of instrument air is controlled by FIC-441027 (locally compensated by TE-441029) acting on FCV-441027, in the instrument air supply line to provide a fixed flow of approximately 97.8 kg/hr.

The stripping gas blowers P-44201A/B can only be operated one at a time. Startup of the blowers is interlocked with level instrumentation in the deaerator tower to ensure that the blowers cannot be started until normal deaerator tower level has been established. The blowers are started via the CPS with no local start facility, however, local emergency stops are provided. The methanol supply to the

Minox reactor is interlocked with the stripping gas blowers running signal.

Addition of methanol without an established nitrogen flow through the deoxidiser could lead to excessive temperatures being generated in the vessel.

Discharge flow from P-44201A/B is monitored by flow transmitters FT-442008 and FT-442009 respectively. A minimum flowrate of 4410 kg/hr is required to ensure a sufficient volume of stripping gas is supplied to the deaerator tower. If the discharge falls below this minimum flowrate, FAL-442008 will initiate the automatic start-up of the standby blower. The electric start-up heater EEH-44201 is controlled by a gap action controller TIC-442015 which has a set point of

150



C. The heater is protected from overheating by TS-442017 and TS-442028 which initiate power isolation of the heater, via the MCC, if the heater temperature exceeds preset limits.

A high temperature in the deoxidiser indicates that there is an excess of oxygen or methanol in the vessel. If this temperature reaches 350C, the methanol feed will be shut off and the stripping gas blowers left running to quench the reaction to avoid potential damage to the vessel, which has a design temperature of 400C.

Pre-heating of the stripping gas, prior to it entering V-44201, is controlled by

TIC-442014 acting on TCV-442014 which is located in the heat exchanger bypass line. If the temperature exceeds the setpoint, TCV-442014 tends to open to increase the flow of gas through X-44201 bypass. If the temperature falls below the setpoint, the opposite applies.


3.3 Water Injection Pumps P-45001A/B/C Control

Water injection pumps suction pressure is determined by the operating pressure of the deaerator tower, and is approximately 5 barg. The booster pumps always discharge water into the suction line at the expense of de-aerated seawater drawn from the tower. The pump overboard dump valves will open to maintain a minimum flow of 600 m3/hr through each pump: the pumps are also equipped with low-low flow trips via transmitters FIT-450146/450246/450346 set at 200 m3/hr. The pump discharge valves XV-450146/246/346 are manually opened following pump start. These valves will close automatically on a pump trip, but will not close automatically on a normal pump stop. On a pump stop, the respective minimum flow overboard dump valve FCV-450145/245/345 will at first move to the open position, driven by the minimum flow controller. Following a time delay of 60 seconds the dump valve will then be driven closed by the CPS logic. Closing the dump valve after pump stop prevents water flowing through the non-running pump casing, and the delay ensures the FCV will close only after the discharge valve is fully closed to minimise transient/locked-in pressures.

On receipt of pump start signal, CPS will confirm that the main discharge valve is closed, (by reference to the limit switch), open the respective overboard dump valve, and send a signal to the pump ECP to initiate a pump start sequence.

Start-up Overrides

Field inputs which cause a trip and require plant to be running before the field measurement goes healthy, require a start-up override applied and then to be reset in the PSD system. This is achieved at the operator workstations:

1. On “Main System” graphic select “PSD”, this will display “PSD

Shutdown/Reset Page”.

2. On this page all the process systems status will be displayed, i.e. input trip, output trip etc. On this page at the bottom there is a button for “Start-up

Overrides Page 1”, “Start-up Overrides Page 2”, etc. Select the page required, the override can be applied on a process group basis or individually.

3. Return to “PSD Shutdown/Reset Page”. On this page against each process system there is a reset pushbutton. Operation of this pushbutton should clear all healthy field inputs which were active and the ones which require a start-up override. Input trips should change from red to green.

Relative Speed of Control Loops

Whilst running, it is important that the water injection pumps are always supplied with suction pressure whatever the injection demand. This pressure is primarily ensured by flow from the de-aeration system and specifically the de-aeration tower. The residence time in the base of the deaerator, at the design rate of

1890 m 3 /hr, between NLL and low alarm, is 15 seconds; between NLL and lowlow trip, around 25 seconds. The response of controllers FIC-441019 and FIC-

441001 must be fast enough to prevent system shutdown on step changes in demand, such as start-up (and shutdown) of pumps. LIC-441010, which acts to adjust for any miss-match between the flow measurement out and flow measurement in, should be slow relative to the flow loops, to minimise overcorrection. The speed of LIC-430010, which is responsible for injecting the produced water into the suction of the water injection pumps, should be relatively slow to avoid introducing large changes in the deaerator flow loops.

The split range operation of the degasser level control will cause excess produced water to be safely dumped overboard should the degasser be subjected to a rapid influx from the separation trains.


3.4 Gas Turbine Control System

The gas turbine control system functions are:













Sequence

Local Control

Protect

Local Display

Display pre selected parameters via serial link in the CCR.

Remote control pre selected parameters via hardwire from the CCR.

The turbine control panel is electrical switch-based and allows command input and indicates status. In addition to this when included a video display device exhibits control parameters.

Instrumentation is included in the turbine package to report operating conditions to control the system and control devices to receive control outputs from primary and backup control systems.

Pre selected parameters can be monitored via serial link in the CCR and pre selected parameters can be controlled via hard wire in the CCR.

Figure 10 shows the control system block diagram for the gas turbine and link with the CCR.

Sequence functions monitor and sense events and perform computations to operate components in the system. Sequence elements include:









Start

Load

Stop

Post lube

Start includes the following manual actions:

 Arm the system: - turning on the electrical supply and resetting any alarm or shutdown malfunctions.

 Reset malfunctions. Prior to start, all shutdown malfunctions must be cleared. Uncorrected shutdown malfunction prevent the package from being started. Only cool down and fast lockout malfunctions require clearing from the LER.

 Select operating mode: Achieved by putting the OFF/LOCAL/ REMOTE key switch in a local or remote position. This package should always be remote operation and can only be started from the CCR.

 The turbine should only be started from the CCR and the Solar Turbine

Control Panel has had the key removed to the central control room. The key can be issued from there under the permit to work system when required for maintenance access or following a “Cooldown Lockout” or

“Fast Stop Lockout”.


 Initiate start: In summary, once a start has been initiated the control system performs a lube and driven equipment system check, starts package fans, performs a fuel shutoff valve test and pre-crank status check.

In detail, when a Start is initiated the following occurs:

The fuel valve and lube pressures are checked, the purge is cranked, light off

(includes; torch ignition, combustion and acceleration to self sustaining speed), starter dropout and lube monitoring.

The pre-crank check comprises of lube system and seal checks, confirmation of lube oil pressure and fuel valve checks. On completion of this the engine is cranked.

Once the start is set the post-lube back up and pre/post-lube oil pumps start on a test cycle and the pre-lube timer starts, if a hot re-start is being performed the pre-lube pump test is not carried out. Following this the control system performs a pressure check on the gas fuel valves, to ensure that they open and close correctly and fuel pressure switch/transmitter signals are verified.

Purge crank rotates the engine with the starter to circulate air and to purge gas accumulated in the engine, air inlet and the exhaust duct. This reduces rotor bow caused by an extended inactive period; on hot starts it cools the gas turbine hot section. Once the purge crank is initiated the engine accelerates to a preset speed typically 10-18% and the crank timer begins. If the engine fails to reach

10-15% within this time the start sequence is aborted and the fail to crank alarm is initiated.

When the preset speed is reached the purge cycle and timer begin. Once the liquid purge timer times out the liquid purge valve closes. The engine accelerates, purging the engine, inlet and exhaust ducts. The crank duration is determined by the exhaust duct volume and after time out of the purge time the start cycle begins.

After light off, the fuel control valves gradually ramp open during the combustion of the fuel gas. The inlet guide vanes ramp open and the bleed valve gradually ramps closed based on the corrected engine speed. The bleed valve and the guide vanes control the airflow through the engine to prevent surge.

If the correct engine temperature is not reached before the ignition times out an ignition failure malfunction is enunciated and the start sequence aborted. Speed and load is sensed by the controlling fuel valve and is regulated to accelerate the engine and to increase the engine temperature.


Operator control

REMOTE

CONTROL

CENTRAL CONTROL

ROOM

REMOTE

DATA

Figure 10 Gas Turbine Control Schematic


3.5 Water Injection Pump P-45001D Control

Pump P-45001D is installed in parallel to the three existing electric-driven pumps and its control philosophy is similar to that of the current pumps with the additional facility to control the pump speed which can be adjusted to match the required water injection flow rate. New and modified graphics have been installed. The pump is started, controlled and stopped from the CCR. There is no requirement to operate the pump from the LER, except for emergency stop of the turbine.

Valve control functions on the Valve Access Platform are performed via the CPS system in the CCR. The Turbine Control Panel TCP) in the LER provides a dedicated control/monitoring facility for the gas turbine driven pump package, with common fault and trip reporting back to the CPS.

The water injection pumps suction pressure is determined by the operating pressure of the deaerator tower and is approximately 5 barg. The produced water booster pumps always discharge water into the suction line at the expense of de-aerated seawater drawn from the tower.

Minimum flow protection for the pump is provided by an overboard dump valve

FCV-450445, which will open at a predefined minimum flow of 330 m 3 /h to protect the pump from damage. The pump is also equipped with a low-low flow trip, FT-

450445 LL set at 280 m 3 /h.

The pump has a discharge double block & bleed valve isolation facility. The discharge valve, XV-450446, start up equalisation line valve, XV-450501 and overboard dump valve, FCV-450445 are actuated based on the pump start-up or shutdown sequence. To prevent high flow rate in the start up equalisation line, an orifice plate has been fitted. On receipt of a pump start signal, the CPS confirms that the main discharge valve is closed (by reference to the limit switch), open the respective overboard dump valve, and then send a signal to the Pump’s Electric

Control Panel (ECP) to initiate the pump start sequence. The differential pressure across the actuated discharge valve will be monitored to provide a permissive to open the valve.

The existing pumps operate against backpressure from the wells and provide a water injection rate and discharge pressure as required by the system. When the

DP between the outlet PT-450443 and the inlet PT-450441 to the pump is less than 2.0 bar, the minimum flow control valve FCV-450445 is shut and the minimum flow controller FIC-450445 is inhibited. When the DP is larger than 2.0 bar, the minimum flow controller is activated and FCV-450445 is allowed to operate under automatic control. The minimum flow 330 m 3 /hr is achieved in a pre-determined time to prevent pump damage. This arrangement indicates when the pump has started ‘pumping’.

4 th Water Injection Pump Start-up Overrides

The 4 th water injection pump package is independently controlled by an associated TCP. The CPS provides routine control functions, which are carried out from the CCR. Start-up overrides are:











TA 850005 LL (fuel gas system)

TA 850006 LL (fuel gas system)

PA 850005 LL (fuel gas system)

PA 450444 LL (pump suction side)

FA 450446 LL (pump discharge side)

These are automatically set and removed by the control system.


Figure 11 CCR Start-up Override Graphic

3.6 Subsea Water Injection Valve Control

The subsea valves operated from the FPSO are:



Wing Valves



Upper Master Valve



SSSV



Annulus Master Valve



Crossover valve

These valves have a ROV override. Subsea valves operated by ROV are:



Choke Valves



Lower Master Valve



Vent valves (downstream of swab valves)



All WI manifold valves.

The choke is adjusted by ROV from the intervention vessel when the associated well is on-line. The swab valves (annulus and tubing) are remotely operated but only from an intervention vessel and not from the FPSO. These valves provide flow paths into the water injection well for the intervention rig and are only required to be operated when such work is ongoing. They must remain under control from the intervention vessel and therefore cannot be operated from the

FPSO. The swab valves remain closed when the well is under control from the

FPSO and they have no part to play in any operational scenario. It should be noted that once the workover riser is connected through the tree cap then all actuated tree valves operable from the FPSO are operable from the Intervention

Vessel.


4. WATER INJECTION SYSTEM & GAS TURBINE OPERATION

4.1 Pre-start Checks

5

6

7

8

9

Step

1

2

3

4

10

11

12

13

14

15

16

17

Procedure

Confirm that water injection system is mechanically complete and that all associated Work Permits have been closed out.

Purge deaerator tower if required.

Note: Purging must be carried out following intrusive maintenance.

Purging is not required if the system is to be started after a short-term shutdown (i.e. with a normal operating seawater level in the deaerator).

Confirm that turret and subsea system are prepared for water injection.

Confirm that the manual valves are positioned as detailed in the ‘Startup’ column of the Valve Position Tables.

Confirm that instrument air supply is available.

Confirm that the seawater distribution system is operational.

Confirm that a methanol supply is available to the de-aeration package.

Confirm that a nitrogen supply is available to the de-aeration package.

Confirm that power is available to the water injection pumps from the HV switchroom (switchboard SWBDB(P)) as below:



P-45001A - cubicle A



P-45001B - cubicle W



P-45001C - cubicle X.

Confirm that power is available to the auxiliary lube oil pumps (water injection pumping packages) from the LV aft switchroom (440V switchboard SWBDA(P)) as listed below:



P-45002A - cubicle BF3



P-45002B - cubicle AHR5



P-45002C - cubicle BF11.

Confirm that power is available to the water injection pumps’ lube oil heaters EEH-45001A/B/C from EDB-83801 in the LV aft switchroom.

Confirm that power is available to the stripping gas blowers from the LV aft switchroom (440V switchboard SWBDA(P)) :



P-44201A - cubicle DF8



P-44201B - cubicle AGR8.

Confirm that power is available to the de-oxidiser vessel start-up heater

EEH-44201 from the LV aft switchroom (440V switchboard SWBDA(P) - cubicle LR5).

Confirm that the de-aeration package trace heating system is operational.

Confirm that FIC-441001 is set to manual and that FCV-441001 and

FCV-441019 are closed.

Confirm that power is available for 4 th Water Injection pump and gas turbine auxiliaries, control systems and the fuel gas heater.

Confirm that the following shutdown valves are closed.



XV-441024 - nitrogen supply



XV-442026 - methanol supply



XV-441028 - air supply.

Signature


4.2 De-aerator Package Purge Procedure

Step

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Procedure

Confirm that water injection system is mechanically complete and that all associated Work Permits have been closed-out.

Ensure that the following shutdown valves are closed as listed below:



XV-441024 - nitrogen supply



XV-442026 - methanol supply



XV-441028 - air supply



XXV-441040 - V-44101 seawater inlet.

Ensure shutdown valve XXV-441002 (V-44101 seawater inlet) is open.

Ensure the manual valves on the package chemical injection lines are closed as listed below:



HV-441002 - biocide (V-44101 seawater inlet)



HV-441003 - antifoam (V-44101 seawater inlet)



HV-441088 - scale inhibitor (V-44101 water outlet)



HV-441019 - O

2

scavenger (V-44101 produced water inlet).

Ensure V-44101 manual vent line valves HV-441024 and HV-441025 are closed.

Ensure stripping gas de-oxidiser vessel manual vent valves HV-442029 and HV-442030 are closed.

Ensure HV-441016 (V-44101 water outlet) is open.

Ensure that HV-441017 (V-44101 produced water inlet) is closed.

Ensure that HV-441014 (V-44101 overboard dump line) is closed.

Set PIC441021 to ‘manual’ and ensure that PCV-441021 (nitrogen/air supply line vent valve) is closed.

Ensure stripping gas exchanger X-44201 bypass valves HV-442040 and

HV-442041 are open.

Set TIC442014 to ‘manual’ and ensure TCV-442014 is open.

Ensure de-oxidiser vessel outlet valve HV-442035 is open.

Ensure nitrogen supply manual block valves HV-441063 and HV-441065 are open.

Ensure stripping gas blowers’ P-44201A/B isolation valves are open:



HV-442001 and HV-442006 (P-44201A)



HV-442007 and HV-442012 (P-44201B).

Connect a temporary nitrogen hose to HV-442026 on the stripping gas exchanger X-44201 and open the utility station nitrogen valve to charge the hose.

Note: The system is now lined-up and prepared for purging.

CAUTION: Ensure that the start-up heater EEH-44201 is not energised throughout the purging procedure as this could result in excessive nitrogen temperatures which would damage the deaerator tower packing .

Open HV-442026 to begin nitrogen purge. Monitor pressure using PG-

441022 (V-44101 stripping gas outlet line) until the pressure reaches approximately 1.5 barg and then close HV-442026.

Note: Although system purging causes a reverse flow across the catalyst bed in V-44201, this should not cause any damage to the bed.

Open HV-441024 and HV-441025 in V-44101 manual vent line to depressurise the system and then close these valves.

Repeat steps 17 and 18 twice.

On completion of purging confirm that HV-441024, HV-441025 and HV-

442026 are closed.

Remove nitrogen hose and re-fit blank flange to HV-442026.

Signature


4.3 De-aerator Package Start-up

Step

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Procedure

Carry Pre-start Checks.

Confirm XXV-441002 (deaerator inlet) is open, then open XXV-441040.

Slowly open FCV-441001 to allow flow to V-44101 and set FIC-441001 to ‘auto’ when the control valve is open. FCV-441001 must be opened slowly to avoid water hammer.

Set FIC-441001 setpoint to approximately 945 m 3 /h so that all flow through V-44101 can pass through the overboard dump line. This is set by adjusting FIC-441019. The flow should be greater than the water injection pump(s) minimum flow.

Set controllers LIC-441010, FIC-441001 and FIC441019 to ‘auto’.

Note: LIC-441010 will send a diminishing signal to FIC-441001 as V-

44101 reached its normal operating level. This will cause

FCV-441001 to close. FCV-441019 in the overboard dump line will tend to open to maintain V-44101 level and establish flow though V-44101. FCV-441001 is a fail-closed control valve while FCV-441019 fails open.

CAUTION: Seawater circulation must be established before starting nitrogen circulation as heat generated by P-

44201A/B could cause localised overheating of V-44101 packing.

Confirm that TIC-442014 (de-oxidiser vessel V-44201 temperature controller) is set to ‘auto’.

Confirm that PIC-441021 (stripping gas blowers supply pressure controller) is set to ‘auto’ and controlling at a pressure of approx. 6 barg.

Open XV-441024 in the nitrogen supply line.

Confirm that FIC441027 is in ‘auto’ and then open XV-441028 in the air supply line.

Confirm that FIC-441001 is maintaining a seawater flow through V-

44101 of approximately 945 m3/h.

Confirm that FALL-442009 (stripping gas blowers discharge flow) is inhibited using the start-up over-ride and the PSD reset.

Start duty blower and monitor FI-442008 to confirm flow through X-

44201 and V-44201. Each of the blowers should not be started more than four times in any one hour period.

Note: The minimum nitrogen flow required prior to energising the startup heater EEH-44201 is 50% of the design flowrate 2450 kg/h.

Energise the start-up heater EEH-44201.

Note: EEH-44201 is controlled by the gap action controller TIC-442015 when temperature in V-44201 exceeds 150



C. It is anticipated that preheating should continue for 1-2 hours to ensure uniform heating of the catalyst bed is achieved.

Circulate stripping gas with the heater on for 1 hour to ensure the temperature is uniform throughout the bed and no longer rising. It will probably settle out at 45 50°C from a cold start.

15 Confirm that HV-442021 is open and then open XV-442026 to establish methanol flow to upstream of X-44201. Ramp up te methanol flow to 50 l/h over 30 minutes.

Note: Flow from the ‘Minox’ methanol pumps is controlled by FIC-

441001 which varies pump stroke length dependent on the flow through the deaerator tower.

Note: During start-up, the methanol injection rate should be manually controlled to provide a gradual increase in methanol flow until the setpoint is reached. The resulting exothermic reaction in V-42201 will initially only occur local to the start-up heater until the flow of stripping gas produces a uniform temperature across the catalyst bed.

Signature


4.3 De-aerator Package Start-up (continued)

Step

16

17

18

19

Procedure

Monitor the temperature in V-44201 and when the exit temperature reaches 250



C, set the methanol flow to maintain this temperature.

Dosing rates are controlled by FIC-441001.

Note: To ensure complete catalytic reaction, a 10% excess of methanol is injected.

Remove standby stripping gas blower inhibit when stripping gas flow is established.

Establish chemical injection, if required, by opening injection point valves as listed below:



HV-441121 - calcium nitrate(V-44101 seawater inlet)



HV-441003 - antifoam (V-44101 seawater inlet)



HV-441088 - scale inhibitor (V-44101 water outlet)



HV-441019 - O

2

scavenger (V-44101 produced water inlet).

Note: O

2

scavenger injection is required if the de-aeration package fails to reduce the oxygen content of the seawater to below

20 ppb (vol). The use of oxygen scavenger impacts on the type and amount of other chemicals used.

Monitor the oxygen content of the treated seawater using AI-441018.

Note: When the oxygen content has been reduced to below 20 ppb

(vol), the water injection pumps can be started.

Signature

4.4 Water Injection Pumps P-45001A/B/C Start-up

Prior to starting the pumps, the deaerator package must in operation, the oxygen content of the seawater be below 20 ppb (vol) and treated water be routed overboard via FCV-441019. Start-up of the water injection system is based around the following requirements:



Ensuring the main water injection pumps are not started against a vacuum condition in the injection riser.



Ensuring that the water injection wing valves are open against a low differential pressure.

To achieve these aims, the produced water booster pumps or seawater lift pumps are used to overcome any vacuum condition prior to starting the main pumps, but with the main pump discharge open to allow flow. To prevent wear on the water injection wing valves, these are opened after the system has been pressurised with the produced water booster pumps or seawater lift pumps, but prior to the start-up of the main pumps.

Start Permissives

The motor-driven water injection pumps can be started in one of three ways dependant upon mode selection at the electrical control panel (ECP):

Manual The main drive motor & auxiliary lube oil pumps are manually started/stopped via their start/stop pushbutton on the front of the

ECP. Manual control is for maintenance/testing purposes only.

ECP Auto On operation of the injection pump start pushbutton on the ECP, the auxiliary lube oil pump is automatically started. Once lube oil pressure is established, the main drive motor automatically starts.

CPS Auto The main drive and all auxiliaries are automatically started on receipt of a start command from CPS.


LOCAL/CPS START

Assuming all on-skid trips and PSD/ESD trips are healthy and all necessary drives available, the pumps can be started. Irrespective of start mode, the “CPS start permissive” is required. The “CPS start permissive” is dependent on:



suction pressure above 3 barg (measured by loop PI-450141)



discharge valve closed XV-450146)



activation of operator pushbutton.

This “CPS start permissive” is only valid for 20 minutes, if the pump has not started by then it times out and the operator must reactivate the CPS pushbutton

(assuming the valve position and pressure have not changed).

Local Start : for either Manual or ECP Auto only the “CPS start permissive” is required, all other status/indication can be monitored at the ECP.

CPS Start : on the water injection start sequence pop-up, the following indications aid start:

 “Water injection pump available” - indication from ECP that all onskid trips have been reset and start permissives are healthy

 “Injection pump CPS start available” - indication from ECP that

“CPS Auto” has been selected



Operati on off the “CPS start permissive” and then “Start” on the pop-up start the pump

 “Start sequence initiated” - indicates pump is in a start sequence

 “Water injection pump online” - this indicates the pump start sequence is complete.

Upon receipt of the pump running signal, CPS drives the overboard dump valve

FCV-450145 fully open for 20 seconds. Thereafter the FIC is placed in auto FCV to control the FCV. The water goes overboard until the discharge valve XV-

450146 is manually opened via CPS and forward flow to the turret is established.

Start Sequence Summary

1. Pump Stopped.

2. Pump Permitted to Start AND (ECP Mode AND Start P/B) OR (CPS Mode

AND Remote Start).

3. Start Aux Lube Oil Pump, Reset Low Lube Oil Press Alarm, Injection Pump

Sequence Initiated Sent to CPS.

4. Lube Oil established and Aux. Pump Running, Start Timer running (10 secs).

5. Main Injection Pump Main Drive Started. Confirmed Running.

6. Command Discharge Valve to Open, enable minimum Flow Valve Control.

Repeat Pump Running to CPS. Remove Lube Oil Override.

7. Discharge Pressure Established.

8. Start Timer Initiated ( 10 Sec,)

9. Stop Auxiliary Lube Oil Pump. Start Sequence Complete.

The required water injection rate is set by the position of the ROV-operated subsea choke valves on each water injection wellhead.

All stops are operable regardless of mode selected. The mode selector is keyoperated, the key being removable when in “CPS Auto”.


Water Injection Pumps P-45001A/B/C Startup Checklist Summary

Step

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Procedure

Confirm that the water injection pumps P-45001A/B/C are prepared for operation. This procedure covers start-up of water injection using a single injection pump A, B or C. Additional pumps can be started as required when injection flow is established.

Ensure that water injection riser(s) are correctly lined up, eg:

Schiehallion Central riser selected:



HV-180855 open - riser 10” block valve



HV-180853 closed - NRV bypass 2” globe valve

Schiehallion West, North and Loyal riser selected:






HV-182853 closed - NRV bypass 2 “ globe valve




Check pressure downstream of the injection pumps using PI-450001.

Note: If the pressure exceeds 5 bar, the water injection pump can be started and steps 4, 6, 7 and 8 below can be ignored.

Confirm that injection pumps are fully primed. Vent valves on pump’s suction and discharge lines can be used to purge air from the pump.

Confirm associated lube oil pumps are running.

Open pump equalisation line valves to charge the water injection system to 5 bar (i.e. de-aerator pressure). (HV-450133/4 or HV-450233/4 or HV-

450333/4).

Monitor de-aerator tower level as water injection system is charged.

After charging to 5 bar, close the pump equalisation line valves. (HV-

450133/4 or HV-450233/4 or HV-450333/4).

Start injection pump using correct start mode and sequence.

Note: Pump discharge valve should be closed and pump discharge water routed overboard via the minimum flow recycle valve.

Commence injection of Scale Inhibitor by opening HV-441088 (V-44101 water outlet).

Open pump discharge valve equalising line (HV-450133/4 or HV-450233/4 or HV-450333/4) to charge the subsea system to 250 barg on PI-450001.

When subsea system is charged, close the equalising line and open the pump discharge valve (XV-450146 or XV-450246 or XV-450346).

For selected injection well, confirm well’s upper master valve is open.

Notes: Software interlocks prevent the upper master valve being opened unless the wing valve is closed.

Subsea valves and indications are provided at the subsea

Master Control Station (MCS).

For the selected injection well, open annulus master valve.

For the selected injection well, open the wing valve.

Note: Software interlocks prevent the wing valve being opened unless the upper master valve is also opened.

Monitor FI-xxx929N to confirm flow into the injection well

Signature


Step

17

18

19

20

21

22

23

24

25

Procedure

For the selected injection well, confirm that the surface controlled subsea safety valve (SCSSV) is open.

Note: Software interlocks prevent the SCSSV being opened unless the wing valve and the upper master valve are open.

Monitor annulus pressure using PI-xxx923N until the injection water temperature (TI-xxx922N) stabilises. The allowable annulus pressure range is 0 to 310 barg.

If annulus pressure outside acceptable range, close injection wing valve.

Open crossover valve to equalise pressure.

Once pressure has equalised, close crossover valve and open wing valve to continue injection.

Record pressure downstream of the choke (PI-xxx922N) and the injection flowrate (FI-xxx929N)

Plot pressure and flow readings on graph provided with the Well

Operating Limits, associated with the selected injection well, to determine whether operating conditions are within the allowable range.

If conditions are outside allowable ranges, stop injection and report findings.

If required, open additional injection wells.

Start additional pump(s) as required while monitoring injection pressures and flow rates and confirming that conditions at each well are with acceptable operating limits.

Signature

4.5 Solar Gas Turbine & Water Injection Pump P-45001D Start-up

WARNING: Before starting the pump drive engine, contact maintenance personnel or verify from written records that all maintenance items have been completed. A physical inspection should be performed by walking around the package to verify that there are no maintenance tags attached to any equipment, that indicate equipment should not be energised or started. Injury to personnel or damage to equipment may result if this Warning is not observed.

The following pre-start checks should be performed prior to each engine start.

The combination of pre-start checks, start procedure and post start procedure should reveal any abnormal conditions that may affect package performance:







Turbine package and gearbox

Water Injection Pump D

Local Control Room LER - (the pressurisation and ventilation system is



 primarily controlled from a pressurisation / F&G system that comprises two EE xd-rated panels. The control panel also interfaces with F&G devices within the turbine enclosure)

Control System

There is a permissive to start in the fuel gas system: if the fuel gas temperature is above 10 o C upstream of XV-850005, permissive to open

XV-850005 will be given even at the maximum delta P across the PCV-

850012, i.e. 55barg –1 barg = 54 bar. If the fuel gas temperature is below

10 o C and the pressure above 17 barg downstream of PCV-850012 or the delta P is less than 38 bar across the PCV-850012, then a permissive to open XV-850005 will be given.


Gas Turbine Pre-Start Checks

Step

1

2

3

4

5

Procedure

Confirm that the gas turbine and auxiliary system are mechanically complete and that all associated work permits have been closed-out.

Verify that the water seals from the oil cooler drip pan are filled with water and valves are open.

Verify that the water seal from the oil filter drain is filled with water and the valve is open.

Verify that water seals from the combustion air coalescer and turbine enclosure HVAC intake coalescers are water filled.

Verify that the valves from the lube oil system are closed. HV-864513,

HV-864514, HV-864515. Reference drg: 37W022F0146-A-8000-GP-

0090.02-2C.

Confirm that instrument air supply is available. 6

7

8

Confirm that the Fuel gas supply is available.

Confirm that the cooling medium is available

9 Confirm that the flare system is available.

10 Confirm that the open drain is available.

11 Confirm that power is available from the switch room.

12 Check inside the turbine enclosure for any signs of leakage.

13 Close Enclosure doors.

14 Confirm that the enclosure F&G system is operational,

15 Confirm that CO2 deluge cylinders are charged and armed.

16 Start selected enclosure ventilation fan and confirm flow rate is acceptable by checking that the correct pressure is being maintained using the operating pressure transmitter

Gear Box Pre-Start Checks

Step

1

Procedure

Confirm that the gearbox is mechanically complete and that all associated work permits have been closed-out.

Local Control Room

Step

1

2

Procedure

Confirm that all associated work Permits are closed out.

Confirm HVAC air fan is running and that the fan and air pressure is being sustained and is remaining above the LER set point. (Indication lights should be green.)

Control System

Step Procedure

1 Confirm that all associated work permits have been closed-out.

Valve Access Platform

Step

1

Procedure

Verify that the fence area on the main walk way below the valve access platform is intact and present to prevent water up to 60 o C dripping on to personnel during start up.

Pump D Pre-Start Checks include:

Step

1

2

3

4

5

Procedure

Confirm that the water injection system is mechanically complete and that all associated Work Permits have been closed out.

Confirm that the manual valves for the pump are positioned for normal operation as detailed in this document.

Confirm that valves XV-450501, XV-450446 & FCV-450445 are shut.

Confirm that the pump is fully primed. If necessary use the vent valves on the pump’s suction and discharge lines to purge air from the pump.

Confirm pump casing drain valve HV-450443 is closed.

Confirm that all instrument impulse line valves are open.

Signature

Signature

Signature

Signature

Signature

Signature


Pump D start-up logic is dependant on the turbine start-up sequence, which is divided in to five main sections as shown by the start graphic in Figure 10 .

1 Request Permissive to Start the Turbine is firstly initiated from the start-up graphic by pressing the push button (XHS-450450). A signal is sent to set up the following valve positions:









Pump Discharge Valve, XV-450446 SHUT

Pump Discharge Equalisation valve, XV-450501 SHUT

Turbine Fuel Gas Supply Valve, XV-850005 OPEN

Set Start-up overrides

If the fuel gas temperature in the supply system is above 10 o C upstream of XV-

850005, permissive to open XV-850005 will be given even at the maximum delta

P across the PCV-850012, i.e. 55barg –1 barg = 54 bar.

If the fuel gas supply temperature is below 10 o C and the pressure above 17 barg downstream of PCV-850012 or the delta P is less than 38 bar across the PCV-

850012, then a permissive to open XV-850005 will be given.

Once the Request Permissive to Start the Turbine is initiated there may be a requirement for the water injection PSD Reset button to be pressed depending on the status of the 4 th water injection system trips; e.g. if trips exist, overrides will be required to be set before enabling reactivation of valves XV-450446, XV-450501 and XV-850005.

2 Permissive to Start the Turbine is given once the status of the valve positions is checked by the PLC:







Pump discharge valve XV-450446 confirmed closed

Pump discharge equalisation valve XV-450501 confirmed closed

Turbine fuel gas supply valve XV-850005 confirmed open.

In addition, the PLC will check whether the permissive to start the turbine is given by the Solar Turbine Control Panel or not. This permissive is indicated by XI-

450407. All required permissives are indicated on the start-up graphic when they are fulfilled. The request to start turbine to idle will only be given once the

Request to Start Turbine to Idle push button XHS-450451 has been pressed.

Once all the permissives are healthy XI450450 illuminates, which is ‘permissive to start’. This will be valid for 20 minutes; if this is exceeded and the request to start the turbine is not given the following will occur;





XV-850005 closes

Start up overrides, which were set will be removed.

3 Request to Start Turbine to Idle from the start graphic may be requested by using XHS-450451 pushbutton (when the start permissive is active). On detection of this, the TCP will proceed through the start sequence to bring the turbine to

70% of the design speed. A start request indication will be displayed through XI-

450408. Simultaneously, a request is sent to switch on the Fuel Gas Heater

ETP-85002. When the speed has reached idle status, the Solar Turbine Control

Panel will send a signal back to the CPS to indicate that the turbine is “ready to load

” through XI-450430. This forms the feed forward permissive.

When the differential pressure across the pump is larger than 2.0 bar, the minimum flow controller FIC-450445 will be activated and the FCV-450445 will be allowed to operate under automatic control. The minimum flow of 330 m 3 /hr will be achieved in a pre-determined time to prevent pump damage.


4 Request to Feed Forward Flow : When the turbine is ready to load the operator operates the Feed Forward pushbutton (XHS-450452) from the start-up screen.

When this has been initiated, the startup graphics indicate “Request to Feed” status through XI-450452. Feed Forward is based on the differential pressure across the discharge valve XV-450446 (Differential Pressure Indicator PDI-

450446). There are two routes:

 If the differential pressure is positive (the discharge pressure is greater than the downstream pressure) the discharge equalisation valve XV-

450501 opens. The downstream pressure will slowly increase. When the differential pressure is less than two bar the discharge valve XV-450446 opens; once fully open the equalisation valve XV-450501 is closed.

 If the differential pressure is negative (the discharge pressure is lower than the downstream pressure) the turbine set point will be increased using the SIC-450453 until the differential pressure is less than 2 bar. At this point, the CPS logic will open the discharge valve XV-450446.

Once the normal Feed Forward is established, the pump speed will be manually entered from the Control and Safety System (C&SS). The CPS logic will switch

SIC-450453 from auto to manual control mode and XI-450453 will indicate the set point speed of the turbine.

5 Request to Trip Turbine to Idle : To trip the turbine to idle pushbutton XHS-

450454 must be operated. This will generate an on screen indication that a Trip

Turbine to Idle has been requested. On detection of XHS-450454 the CPS will close XV-450446 and XV-450501 after a 30 second time delay. The CPS output

XHS-450454 sends a signal to the TCP which will proceed through the slow to idle sequence and bring the pump to idle speed. As XV-450446 closes, FIC-

450445 and FCV-450445 will open under PID (Proportional, Integral and

Derivative) control to protect the pump against low flow rates.

A cool down signal, indicated by XI-450410, will be generated to indicate a trip to idle/ Normal stop has occurred. The TCP will remain at idle for 3 hours before performing a full stop sequence, unless the feed forward button is pressed within the 180 mins. Restart to Feed Forward can only occur under these conditions:







XV-450446 CLOSED

XV-450501 CLOSED

Turbine tripped to idle.

Once feed forward is re-activated, the CPS will automatically bring the turbine up to idle speed and ‘ready to load’ before ‘re-feeding forward’.

Start faults may include:

Permissive not given to open the inlet fuel gas valve XV-850005

Fault: The gas from the fuel gas heaters is less than 10 o C and 17 barg, and too cold to enter the engine burner management system

Correction:

P&ID drawing: 37W022f0146-A-8000-GP-0090.00-2C

Open valve HV-850538 and HV-850539 until permission is given.

Permissive not given start the turbine

Fault: Fast stop or Cooldown lock-outs have occurred

Correction: Reset LER acknowledge & reset switches.

Table 12 Water Injection Pump P-45001 Gas Turbine Start Faults


Figure 12 shows the turbine start-up graphic displayed in the CCR and can be found in the screen f or pump “C” and “D”, Figure 13.

Figure 12 CCR Turbine Start-up Graphic

Figure 13 CCR Graphic Display Screen for Water Injection Pumps C & D


Refer to P&ID L-8000-GP-0046.03, A-8000-GP-0090.02.

Pump P-45001D valve positions for start-up and normal operation are listed below:

Valve Tag No.

HV-450527

HV-450501

HV-450502

HV- 450505

HV-450506

HV-450411

HV-450412

HV-450513

HV-450514

HV-450515

HV-450522

HV-450521

HV-450525

HV-450526

Description

P-45001D suction vent valve

P-45001D suction block valve

P-45001D suction drain valve

P-45001D air vent block valve

P-45001D discharge vent valve

P-45001D discharge drain valve

P-45001D suction automatic air vent valve

XV- 450446 (P45001D) drain valve

XV-450446 (P45001D) block valve

XV-450501 (P45001D) drain valve

FCV-450445 (P45001D) block valve

XV-450501 (P45001D) block valve

P-45001D vent system

P-45001D Bypass vent

Start-up

Position

Closed

Open

Closed

Open

Closed

Closed and blanked off

Open


Open

Closed

(Locked)

Open

Open

Closed

Closed

Pump P-45001D turbine valve positions for start-up and normal operation are:

Normal

Operation

Closed

Open

Closed

Closed

Closed


Closed


Open

Closed

(Locked)

Open

Open

Closed

Closed

Valve Tag

Number

HV-804807

HV-520503

HV-520510

HV-520511

HV-815502

HV-815503

HV-815515

Description

G-45001 instrument air block valve

G-45001 LP flare block valve

G-45001 LP flare drain line

G-45001 LP flare drain line

G-45001 cooling medium supply valve

X-45003 cooling medium drain valve

G-45001 cooling medium return block valve

Start-up

Position

Open

Open

Closed

Closed

Open


Open

Normal

Operation

Open

Open

Closed

Closed

Open


Open

HV-815514 G-45001 cooling medium return drain valve

HV-864510

HV-864516

G-45001 oil origin drain valve

G-45001 oil train drain valve


Closed

Closed


Closed

Closed

HV-864511

HV-864512

HV-864518

HV-864513

HV-864514

HV-864515

G-45001 lube oil filter drain valve

G-45001 combustion drain valve

G-45001 sampling Valve

G-45001 lube oil tank drain valve



Closed

Closed

Closed

Closed

Closed

Closed

Closed

Closed

Closed

Closed

Closed

Closed


4.6 Exhaust Gas Purging

If unburnt fuel or other combustibles are present in the exhaust system they may ignite and cause damage. Fuel may accumulate in the exhaust system before a start or after an engine flameout or ignition failure. Hence, the exhaust system must be purged by following the procedure below.







The internal free volume of the exhaust path to be purged is 1236 cu ft.

A purge of a minimum 3 air changes in the exhaust is required.



Ensure that the normal gas producer speed (NGP) is reached during the purge crank. Minimum speed is 15% and recommended speed is 20-25%.

Purging must not occur at speeds greater than 25%.

Purge Air Flow:

Crank Speed (NGP)

15%

20%

25%

Air Flow, SCFM

2250

3000

3750

 Purge Crank time required is calculated to be: 98 seconds (based on a crank speed of 15%)

The advised minimum purge time is 240 seconds. 



In addition, the following should be checked on a continuous basis:

 Properly maintain and adjust all gas turbine, controls and exhaust system as recommended by the manufacturer.



If the engine is to be started after an engine flameout it must be ensured that all corrective measures have been taken to correct any root causes for the failure before any attempt is made to restart.

Ensure that any exhaust gas valves are installed correctly and are working properly; particularly the free passage of exhaust gas to the atmosphere must be maintained during the engine start-up and operation.





Ensure that the exhaust collector and the exhaust system liquid drains are operating properly.

Maintain fuel quality. Any deviation from the required specification could lead to a malfunction of the fuel control system.

4.7 4

th

Water Injection Pump & Turbine Start-up from CCR

Step

1

2

3

4

5

6

The table below describes the start-up sequence on the turbine control panel in the LER, before the gas turbine can be started from the CCR.

Procedure

Ensure all relevant personnel are aware that the 4 th water injection pump is about to be started. Make a tannoy announcement.

Get the key to the turbine control panel from the CCR, under Permit to

Work

Rotate OFF/LOCAL/REMOTE Key switch (S101) to LOCAL position.

Verify LOCAL Light (DS101) is illuminated.

Select Operation Summary display screen.

Press LAMP TEST switch (S113). Verify all indicator lights illuminate.

Signature


7

8

9

10

11

12

13

14

Press and release the ACKNOWLEDGE Switch (S117) and then press and release RESET Switch (S114) to acknowledge and clear any alarm or shutdown indications.

Select alarm summary display screen and check for alarm and shutdown indications. Correct any alarm and shutdown indications that remains

Verify that AUTO/MANUAL switch is in AUTO

Verify READY light (DS177) illuminates and [Ready] is highlighted on

Operation Summary Display screen

Rotate OFF/LOCAL/REMOTE keyswitch (S101) to REMOTE position.

Verify that “Ready to start” light turns green on the start up screen for the turbine in the CCR.

Check fuel gas pressure on the LER control panel.

Return the key to the turbine control panel back to the CCR under Permit to Work.

Note: If any malfunctions remain the READY light will not illuminate. If this occurs the malfunction must be corrected and the ACKNOWLEDGE

Switch and RESET Switch (S114) must be pressed again to reset the malfunction circuit.

WARNING: The turbine package is now ready for operation from the CCR.

When the turbine is “ready to start”, “running” and “stopping”, DO NOT

ROTATE the OFF/LOCAL/REMOTE keyswitch (S101) to the LOCAL position.

If the switch is rotated to the LOCAL position all remote operation functions cease and all control is lost between turbine package and CCR.

When the turbine has totally stopped the OFF/LOCAL/REMOTE keyswitch

(S101) can be rotated to the LOCAL position.

On the turbine control panel there is a START Switch (S110) that has been disabled. The reason for this is that if the turbine is started from the LER, the water injection pump may be damaged.

The Key to the turbine control panel is held in the CCR and can only be used under a Permit to Work. Under normal operation, Keyswitch S101 should be in the REMOTE position at all times.

Note: Finally perform the post start sequence and compare against norms. If significant deviations are present shut down the engine and determine the cause.

The control system monitors the temperatures, system pressures, engine speed, vibration levels and other indicators. It also provides throttling (fuel topping) to compensate if parameters are exceeded, indicators for malfunctions on the operator display, and displays alarms providing automatic control of the engine shutdown and the post lube unit.


4.8 Gas Turbine Compressor Cleaning using Wash Cart

Reference drawing: 37W022F0146-A-8000-GP-0090.01-2C

As Schiehallion’s environment contains salt, cleaning needs special care. Online cleaning must be systematic not sporadic. If cleaning is sporadic, concentrated salt deposits will accumulate in the air compressor and then online cleaning will send a ‘slug’ of salt through the turbine. The slug acts as a catalyst for other contaminants provoking an erosive reaction. Frequent on-line washing will be required to prevent the build up of salt deposits.

2

3

4

It must be verified prior to cleaning that the Demineralised water plant is in operation, to ensure a Wash water supply.

The cleaning system must be flushed prior to use to ensure all debris is removed and to pressure check for leaks. Flush out as follows:

Step

1

2

3

4

5

6

7

8

9

10

11

12

13

Procedure

Check that the water inlet that connects the demineralised water source and the tank water inlet is opened.

Open the following valves: HV-803700, HV-803711, HV-803701, HV-

803702 and control the water rate by HV-803710.

The vent valve is also opened and the tank filled with water until it begins to flow out of the vent valve.

Open valve HV-530501, vent line on the skid

Close the water inlet.

Close the following valves: HV-803700, HV-803711, HV-803701, HV-

803702 and globe HV-803710

Close the vent valve HV-530501

Open the on-line air inlet valve to pressurize the tank to normal working air pressure 6.9 barg and then close the air inlet valve.

Open valve HV-804805 and HV-804808.

Leave the tank under pressure for 10 minutes. There should be no pressure drop or leakage to any of the fittings.

Slowly open the drain valve and allow the water to safely run to the drain until the tank pressure is zero.

Open valve HV-864517

Close the drain valve, remove and clean and replace filter inserts from the air water and chemical Y inlet strainers

Close valve HV-864517

Signature

14

Engine on-crank or on-line wash nozzle/manifold ring assembly pressure is checked thus:

Step

1

Procedure

Open the demineralised water inlet valve and the vent valve and half fill the tank.

Open the on-crank or online air inlet valve to pressurize the tank to 2.0 barg. Connect the corresponding hoses between the tank outlet and the on-line or on crank wash manifold inlet and slowly open the tank wash fluid outlet.

If any leaks occur tighten the fittings. Repeat this procedure increasing the pressure each time until the max working pressure of 6.9 barg is reached without leaks.

Pressure test the atomising nozzles to confirm correct spraying. If any of them appear blocked disconnect them and back flush the nozzle tip through the orifice with a commercial electrical instrument cleaner followed by high-pressure air or water.

Signature


On-Crank Engine Compressor Cleaning (maintenance only)

Cleaning

Method

Cleaning Solution

(Volume/Dosage)

Gallons

Solution

Rinse

16

25 2

Distilled

Water to solution

Ratio.

4:1

N/a

Flow GPM

Air

Pressure

Psig 1

4.4

4.4

85-100

85-100

Air Flow

SCFM

4.6

4.6

On-Line Engine Compressor Cleaning

The objective of on-line cleaning is to clean the engine compressor on a regular basis to reduce the build up of deposits in the compressor, i.e. maintaining a clean engine rather than allow it to become fouled. On-line cleaning extends the period between on-crank cleaning. However incorrect on-line cleaning can induce fouling and chemical cleaning frequency cannot be accurately estimated hence a trial run period should be used to determine this and before on-line cleaning commences the baseline fouling trend should be established.

Cleaning

Method

Solution

Rinse

Cleaning Solution

(Volume/Dosage)

Gallons

16

8

Distilled

Water to solution

Ratio.

4:1

N/a

Flow GPM

1.7

1.7

Air

Pressure

Psig 1

85-100

85-100

Air Flow

SCFM

1.8

1.8

Notes:

1) The optimum pressure at the injectors is between 90-100 Psig (6.1-6.9 barg) measured at the skid edge connection.

2) This is the recommended dosage. Compressor should be rinsed until a clean waste stream is noted in engine drains.

6

7

8

9

10

11

12

On-line Engine Compressor Cleaning Procedure

Step

1

2

3

4

5

Procedure

Confirm that engine is stabilised and at operating speed

Confirm that ambient temperatures are above 4 o C

Close all valves on the pressure injection tank

Open the wash cart vent valve and the wash cart water inlet valve

Fill the cart with the required amount of water and then close the tank water inlet valve and disconnect the water supply

Connect the hose to the chemical source and the chemical inlet

Open the cart chemical inlet valve and fill the tank as required

Close the chemical inlet valve and disconnect the chemical supply

Close the Cart vent valve

Pressurise the tank to normal working pressure by opening the cart air inlet valve and leave the valve open for the duration of the on-line wash to maintain a steady injection pressure and flow

By selecting the appropriate on-line wash key and by opening the fluid outlet valve start the on-line wash

Use all the cleaning solution in the tank

Signature


Post Cleaning Procedure

Step Procedure Signature

1

2

3

4

5

6

7

8

Purge the line for 2-3 minutes by leaving the air inlet valve open.

Close the air inlet valve and leave the outlet open to allow the cart pressure to drop between 1.4 and 2.1 barg.

Select the appropriate function key to switch off the on-line cleaning, close the fluid outlet valve and disconnect supply hose

Slowly open the vent valve and allow the pressure to discharge to 0 barg.

Within 20 minutes of the chemical wash a water rinse should be performed to ensure the Cart is free of the Chemical Solution/ Water mixture.

Open the water inlet valve and fill the cart with the required amount of demineralised water.

Close the water inlet valve, disconnect the hose and flush the system as above when the chemical wash was completed.

Compare performance figures with those before the wash and confirm the contamination factor has decreased below 5%.

4.9 Routine Operations of 4

th

Water Injection Pump and GT

A check out should be performed daily when the 4 th water injection pump package is running in order to confirm normal operation. A summary of the system condition is displayed on the operation summary screen. Normal operating data, instrument ranges, alarms, trip points for the water injection system, water injection pump, gear box, gas turbine, start motor, accessory gear box, lube oil and enclosure are listed below. If significant deviations occur the engine should be shut down and the cause of the deviation established.

Expected Operating Data for Water Injection System

Description

Suction to pump

Suction to pump

Discharge from Pump

Discharge from Pump

Water Injection Rate FIC-

450445

Instrument

PI-450441

PA-450442

PI-450443

PA-450444

FIC-450445

Discharge from Pump

Delta Pressure for

Valve XV-450501

FA-450446

PDI-450446

Minimum flow valve position ZI-450445

Value

Normal: 4.6 Barg

High Alarm: 7 Barg

Low Alarm 3 Barg

Trip high: 8 Barg

Trip Low: 2 Barg

Normal: 207-223 Barg

High Alarm: 250 Barg

Low Alarm 100 Barg

Trip high: 260 Barg

Trip Low: 95 Barg

Normal: 930 m3/h

Over speed case: 1150 m3/h

Low Alarm: 290 m3/h

Trip low: 280 m3/h

Normal: 0

Start up: 0 to 256 barg

Normal value: 0 to 100 % open


Expected Operating Data for Water Injection Pump P-4001D

Description

DE Vibration

DE Vibration

DE Seal Pressure

NDE Seal Pressure

DE Journal Bearing

Temperature

NDE Journal Bearing

Temperature

NDE Vibration

NDE Vibration

I/B Thrust Bearing

Temperature

O/B Thrust Bearing

Temperature

Balance Return Line

Temperature

Pump Speed

Pump HP

Instrument

YI-450400X

YI-450400Y

PI-450416

PI-450417

TI-450405

TI-450406

YI-450401X

YI-450401Y

TI-450407

TI-450408

TI-450409

SI-450404

XI-450425

Value m m m m m m m m

Range: 0 to 2.5 Barg Normal: 0

Barg

Alarm: 0.3 Barg

Trip: 0.5 Barg

Range: 0 to 2.5 Barg

Normal: 0 Barg

Alarm: 0.3 Barg

Trip: 0.5 Barg

Range 0 to 200 o C

Normal: 59 o C

Alarm: 90 o C

Trip: 100 o C

Range 0 to 200 o C C

Normal: 37.6 o C

Alarm: 90 o C

Trip: 100 o C m

Normal: 11 m m m m

Normal: 11 m m m

Range: 0 to 200 o C

Normal: 42 o C

Alarm: 110 o C

Trip: 120 o C

Range: 0 to 200 o C

Normal: 42 o C

Alarm: 110 o C

Trip: 120 o C

Range: 0 to 200 o C

Alarm: 90 o C

Trip: 95 o C

Range: 0 to 4000 RPM

Normal: 3650 RPM Design

Over speed: 3833 RPM

Range: 0-11 MW

Normal: 6.56 MW Design

Overspeed: 8.075 MW


Expected Operating Data for Turbine to Pump Gear Box

Description Instrument Value

Thrust Brg Outboard Temp

RDN

TI-450414B Range: 0 to 200 o C

Alarm: 70 o C

Trip: 75 o C

Thrust Overboard BRG Temp TI-450414A Range: 0 to 200 o C

LSS End Bearing Temp TI-450412

Alarm: 70 o C

Trip: 75 o C

Range: 0 to 200 o C

Axial ZI-450405

Alarm: 100 o C

Trip: 105 o C

Range: 1-0-1 mm

Accelerator

Bearing HSS Y axis

XI-450408

YI-450405Y

Alarm: 0.1 mm

Range: 0 to 25 mm/s rms

Alarm: 7.0 mm/s rms

Trip: 18.0 mm/s rms

Range: 0 to 150 µm

Bearing HSS X axis

Bearing LSS Y axis

YI-450405X

YI-450406Y

Alarm: 63 µm

Trip: 93 µm

Range: 0 to 150 µm

Alarm: 63 µm

Trip: 93 µm

Range: 0 to 150 µm

Bearing LSS X axis YI-450406X

Alarm: 97 µm

Trip: 142 µm

Range: 0 to 150 µm

LSS DE END Bearing Temp TI-450413

Alarm: 97 µm

Trip: 142 µm

Range: 0 to 200 o C

Alarm: 100 o C

Trip: 105 o C

Thrust inboard BRG Temp

RDN

Thrust inboard Bearing temp

HSS NDE end Bearing Temp

TI-450415B Range: 0 to 200 C o C

Alarm: 70 o C

Trip: 75 o C

TI-450415A Range: 0 to 200 o C

Alarm: 70 o C

Trip: 75 o C

TI-450411 Range: 0 to 200 o C

Alarm: 110 o C

Trip: 115 o C

Expected Operating Data for Water Injection Pump P-45001D Gas Turbine .

Description

Power Turbine Speed

Gas Turbine Air Inlet

Instrument

SI-450405

TI-450422

PDI-450401

Value

Maximum: 100% (Design

Speed)

Range: 0 to 120 %

Normal: -6 to 23 o C

Range: -40 to 70 o C

Range: 0 to 24.9 mbar Gas Turbine Air Inlet Filter Delta

Pressure:

Gas Turbine Inlet Filter Delta

Pressure:

Gas Turbine Compressor Discharge

Pressure:

PI-450432 Normal: 3 barg

Range: 0 to 20.7 barg


Expected Operating Data for WI P-45001D Gas Turbine (continued)

Gas Turbine T5 Average

Fuel Gas Rate

Gas Turbine T5 Max- T5 average

Fuel Gas Pressure

Fuel Gas Temperature:

At the turbine inlet, assuming that the superheater is online. (Trip low is to prevent dewpoint being reached and liquids reaching the turbine)

Power Turbine BRG 5-X-axis

Power Turbine BRG 5-Y-axis

Power Turbine Axial

Power Turbine Thrust Bearing

Power Turbine BRG 4-X-axis

Power Turbine BRG 4-Y-axis

Gas Producer NGP PV

Gas Producer BRG 3-X-Axis

Gas Producer BRG 3-Y-Axis





Gas Producer Axial

Gas Producer Thrust Bearing

TI-450433

FI-850005

TI-450434

PI-450433

TI-850099

YI-450415X

YI-450415Y

YI-450412

TI-450417

Y-450407X

Y-450407Y

SI-450406

YI-450408X

YI-450408Y

YI-450409X

YI-450409Y

YI-450410X

YI-450410Y

YI-450411

TI-450431

Range: 0 to 1000 o C

Set point: 290 o C

0 to 2177 kg/hr

Range: 0 to 1000 o C

Normal: 24 barg

Alarm low: 22 barg

Alarm high: 27.6 barg

Trip low: 19.7 barg

Trip High: 28.6 barg


Normal: 35.2 o C

Alarm low: 31 o C

Alarm high: 45 o C

Trip low: 28 o C

Trip high: 55 o C

Range: 0 to 150 o C

Norm

Range: -1 to 1 mm

Range: 0 to 150 o C

Maximum: 100%

Range: 0 to 120 %

Normal: -0.08 mm

Range: -1 to 1 mm

Range: 0 to 150 o C


Expected Operating Data for Gas Turbine Start Motor

Description

Voltage

Current

Motor Speed

Instrument

XI-450424

XI-450423

Si-450407

Value

Range: 0 to 500 V

Range: 0 to 600A

Range: 0-5000 RPM

Expected Operating Data for Gas Turbine Accessory Gear Box

Description

Accessory Gearbox Velocity

Instrument

XI-450428

Value

Range: 0 to 20 mm/s

Expected Operating Data for Gas Turbine Lube Oil System

Description

Header Temperature RDN

Header Temperature

Header Pressure RDN

Header Pressure

Oil Filter Delta Pressure

Pre Post Pressure

Oil Tank Temperature

Oil Tank Pressure

Oil Tank Level

Accessory Gearbox bearing Drain

Temperature

Gas Producer Bearing Drain

Temperature

Gas Producer Bearing Drain

Temperature

Power Turbine Bearing Drain

Temperature

Scavenge Pump Pressure

Back-Up Lube Pressure Test

Instrument

TI-450424

TI-450425

PI-450434

PI-450435

PDI-450405

PI-450436

TI-450426

PI-450437

LI-450401

TI-450427

TI-450428

TI-450429

TI-450430

PI-450438

PI-450439

Value

Normal: 57.6 o C

Maximum: 68 o C

Range: 0 to 150 o C

Alarm: 71 o C

Trip: 82.2 o C

Normal: 60.2 o C

Maximum: 68 o C

Range: 0 to 150 o C

Alarm: 71 o C

Trip: 82.2 o C

Normal: 3.4 barg


Alarm: 1.86 barg

Trip: 1.03 barg

Normal: 3.45 barg


Alarm: 1.86 barg

Trip: 1.03 barg


Alarm: 2.07 barg


Range: 0 to 150 o C Normal:

63.7 o C

Range: 0 to 37.3 mbarg

Range: 0 to 711 mm

High alarm: 550 mm

Low alarm: 483 mm

Maximum: 121 o C

Range: 0 to 150 o C

Maximum: 121 o C

Range: 0 to 150 o C

Maximum: 121 o C

Range: 0 to 150 o C

Maximum: 121 o C

Range: 0 to 150 o C




Expected Operating Data for Gas Turbine Enclosure

Description

Primary Vent Fan

Enclosure Temperature

Backup Vent Fan

Enclosure Pressure (note)

Instrument

XI-450426

TI-450432

XI-450427

PI-450420

Value

On / Off

Range: 0 to 150 o C

High alarm: 75 o C

On / Off

Range: 0 to 24.9 mbar

Range: 0 to 24.9 mbar Enclosure Filter Delta Pressure

(note)

PDI-450404

Note: The enclosure pressure is negative.

WI Pump P-45001D Discharge Pressure for Different Operating Scenarios

Case Flow from

Deaeration

Tower

1 m3/h

1411

Flow

Produced

Water m3/h

1490

Electric pumps

Running

A, B, C

Turbine driven pump

Design

Speed

Pump Discharge

Pressure Barg

Total flow rate: m3/h

2

3

4

5

6

7

8

9

10

1890

1890

1890

1890

300

300

1150

1631

930

0

0

0

0

0

0

0

1490

0

Running

A, B, C

Running

A, B

Running

A, B

Running

A, B, C

Not running

Not running

Not running

Running

A, B, C

Not running

Design

Speed

Design

Speed

Over

Speed

Not

Running

Over

Speed

Design

Speed

Over

Speed

Over

Speed

Design

Speed

Pressure: 206.2

Flow rate: 2901

Pressure: 234.9

Flow rate: 1890

Pressure: 221.9

Flow rate: 1890

Pressure: 231.8

Flow rate: 1890

Pressure: 210.7

Flow rate: 1890

Pressure: 271.9

Flow rate: 300

Pressure: 246.3

Flow rate: 300

Pressure: 208.6

Flow rate: 1150

Pressure: 206.1

Flow rate: 3121

Pressure: 210

Flow rate: 930

Design speed for water injection pump P-45001D:

Over speed for water injection pump P-45001D:

3650 PRM

3833 RPM


4.10 Subsea/Well Operating Limits

For each well there is a safe operating limit as defined on a graph of wellhead injection pressure (from PI-sss922n) against well injection flowrate (FI-sss929n).

An example is shown below:

Well Operating Limits

300

250

200

150

100

50

0

0

BHIP Limit

Erosional Velocity Limit

Surge Limits

Operating Line

Op Pt

50 100 150 200 250 300

Flowrate (m3/hr) - FIsss929n

350 400

Figure 14 Well Operating Limits

The allowable operating envelope is bounded by the following key limits:

Bottom Hole Injection Pressure Limit (BHIP Limit) - This is the maximum injection pressure allowable at the top of the completed zone. Injection pressures in excess of this limit could lead to failure of the formation above the completed zone and therefore permanent damage to the well’s injection capability. This line has been converted into a wellhead injection pressure limit which is flowrate dependent.

Erosional Velocity Limit - This is the maximum allowable injection rate from an erosion viewpoint. It also represents the maximum measurable rate on the wellhead venturi.

Surge Limit - This represents the maximum allowable injection rate to ensure that hydraulic surge on shutdown does not lead to an over-pressuring of the subsea system.

The allowable operating envelope lies below the BHIP limit curve and to the left of both surge limit and erosional velocity limit lines.


The additional limes on this plot show the expected operating point of the water injection based on the seawater injection choke position. This line covers the range of possible injection indices expected for this well (dotted line) and the most likely injection index range (solid line). This line is primarily for information.

Operation outside this line indicates incorrect choke position, an unexpected choke performance or an unexpected reservoir performance.

If operation of the well is outside this limit, the well must be shut in and advice obtained. It may be required that the ROV choke position will need to be modified before injection can recommence.

Note: The allowable operating envelope will change during field life and this plot will be updated on a regular basis.

In addition to the above operating limits there is also a maximum allowable injection rate to each drill centre (for Central it was 90mbd initially).

Well Annulus Operating Limits

The allowable range of operating pressures in the well annulus is 0 to 310 barg.

To ensure that annulus pressures are measurable using Pisss923n, the annulus master valve AMVsss935n, must be open.

If these values are exceeded during start-up or shutdown of the well, the well must be temporarily shut in at the wing valve and the tree cross-over valve must be opened to relieve pressure into the tubing. Note that due to the high injection temperatures at the tree, the pressure in the annulus may increase on shutdown or start-up.

Well Start-Up and Shutdown

The main consideration (operating the wing valves when the water injection pumps are running) applies equally to start-up and shutdown of individual wells.

Hence, prior to a wing valve on a water injection well being opened or closed, the main injection pumps will be shutdown and flow is maintained through these pumps using the produced water booster pumps and/or seawater lift pumps.

Once the wing valve operation has been completed, the main pumps can be restarted.


4.11 Water Injection Pump P-45001D Speed Control

The pump will float on the system pressure, at the prevailing flow rate when the system runs at constant speed.

The facility to adjust pump speed set point (SIC-450453) to match the flow rate to water injection requirements is provided. The CRT can manually adjust the speed of the turbine using “the Manual Speed Set Point Controller” SIC-450453.

Raising or lowering the speed would result in increase or decrease in flow rate.

Any adjustments to the speed set point will be carried out by sending a signal to

TCP SY-6000.

The rate of change of speed will be restricted within the TCP. The set point can only be in the range between 70-105% of the turbine speed.

The pump discharge PT-450443 will be used as a process variable input to the speed controller SIC-450443. If PT-450443 high discharge pressure alarm is activated the speed set point will be reduced to 95% of the pump design speed by the CPS, which will be done only once. This will reduce the pump shut in pressure in the event the discharge is closed.

It is possible to increase the pump speed to 5 percent above the pump design speed to allow the pump to flow at its maximum flow rate. This facility will only be required when one, or more of the three motor driven water injection pumps are not available and will only be possible to achieve when the ambient temperatures are below 12

°C, allowing the gas turbine to generate sufficient power, reference figure 6.3.

In addition, pump discharge PT-450444 will be used as a process variable input to the Control and Process Shutdown System (CPS) to trip the pump to full stop in the event the high high pressure set point is activated. Furthermore, the CPS has to monitor and record the pressure and duration.

The CPS shall report the following for each year of operation:

 Total duration of all pressure excursions that are above the design pressure of 270 barg, and below a 20% overpressure threshold of 359.1 barg.

 Total duration of all pressure excursions that are above the 20% overpressure threshold of 324 barg, and below a 33% overpressure threshold of 359.1 barg.

This can be achieved if the pump operates above its design speed or in an event of the discharge being closed. Figure 13 shows the pressure excursion graphic displayed on the screen in the CCR and can be found in the screen for pump “C” and “D”.

Figure 15 Pressure Excursion Graphic


4.12 Water Injection Pump P-45001D Standby Mode

The ability to reduce the pump speed to idle whilst running the turbine has several operating advantages. Primarily it will reduce restart time in the event of a process trip or the need to reduce flow for operational reasons.

The CRT may trip the turbine to idle speed using the push button XHS-450453.

On detection, the CPS logic will send a signal to the Solar Turbine Control Panel

(TCP) to slow down the turbine to idle speed. When the turbine has reached idle speed status, the TCP will send a signal to “Cool down Indication” XI-450410 and close XV-450446 and XV-450501 after a 30 second time delay.

As XV-450446 closes, FIC-450445 will open under PID control to protect the pump from damage at low flow rates. “Permissive to Restart Feed Forward” XI-

450454 will be given under the following conditions:





XV-450446 and XV-450501 are closed

Turbine operates in idle mode

The TCP will keep the turbine running in idle mode for 180 minutes, before it trips the turbine to full stop. If CRT presses “Request to Restart Feed Forward” push button XHS-450455 during this period, the CPS logic will send a signal to the

TCP to restart the turbine to idle. When the turbine has reached idle status, the

Solar Turbine Control Panel will send a signal to the CPS logic to bring the turbine automatically to the feed forward status and change “Speed Set Point

Controller” SIC-450453 from automatic to manual mode. This will bring the unit back on line again and the speed controller set point can be adjusted as necessary to suit the requirement.

If the CRT does not press “Request to Restart Feed Forward” push button XHS-

450455 during this period, the Solar Turbine control Panel will send a signal XI-

450411 to indicate that the “Gas Turbine is totally stopped” to the CPS.

4.13 De-aerator & Water Injection Pumps P-45001A/B/C Shutdown

4.13.1 Normal Shutdown

Following shutdown and valve isolation of the Deaeration Tower, XXV-441040 should be checked for leakage by using FCV-441001 drain valves. It is not desirable to allow leakage into, and filling, of the tower as this causes high stresses on the structural supports under severe weather conditions.

If leakage is found, either a double block and bleed should be set up on the inlet, or FCV-441019 and downstream manual valve should be left open to drain the tower overboard.

Excessive contact with oxygen will rapidly deplete the sensing elements of the analysers AT-441018 and AT-442019 when these sensors are active. Therefore the analysers should be de-energised to extend sensor life.

A planned shutdown of the de-aeration package can be initiated from the CPS:

Tag Number

P-44201A/B

XV-441024

XV-441028

XV-441040

XXV-441040

Description

Stripping Gas Blowers

Nitrogen Top-up Line

Instrument Air Top-up Line

Methanol Supply Line

Seawater Inlet Line

Action

Stopped

Closed

Closed

Closed

Closed


The system control valves can be moved to their shutdown positions thus.

Valve Tag No.

FCV-441001

FCV-441019

FCV-441021

PCV-441023

FCV-441027

TCV-442014

Shutdown

Position

Closed

Open

Closed

Closed

Closed

Open

Description

Seawater Inlet Valve

Overboard Dump Valve

Stripping Gas Vent Valve

Nitrogen Top-up Valve

Instrument Air Inlet

Stripping Gas Exchanger Bypass

Following shutdown of the deaerator package confirm the chemical injection valves are closed as detailed below. Refer to P&ID L-8000-GP-0043.00

:

Valve No.

HV-441002

HV-441121

Description

Antifoam

Calcium nitrate

Signature

HV-441008

HV-441019

Scale Inhibitor

Oxygen Scavenger

The deaerator package is now shutdown. However, the system trace heating should not be isolated until the deaerator has been drained and vented.

Additionally, each of the drain valves within the seawater pipework should be opened to ensure that no liquid is present.

The only subsea condition that will cause the water injection trees to close in is loss of hydraulic fluid, typically due to umbilical snagging.

VACUUM CONDITIONS ON SHUTDOWN

When the water injection pumps’ shutdown and discharge valves are closed, the reservoir pressure is such that water will be drawn into the formation, causing a vacuum to be pulled in the flexible risers. To prevent this condition, injection well wing valves are closed following shutdown of the injection pumps. Additionally, the risers are reinforced with steel liners to cope with vacuum conditions.

ISOLATION FOR MAINTENANCE

The water injection pumps are only provided with a single discharge isolation valve due to space limitations. The water injection pumps must therefore be shut down and locked out to achieve positive isolation for maintenance. The water injection wells are not capable of back-pressuring the FPSO and therefore work may be carried out without closing the turret isolation valves. The subsea well wing and master valves must be closed to prevent pulling a vacuum and drawing air into the system.


DEPRESSURISATION OF WATER INJECTION SYSTEM

Step

1

2

3

Procedure

Shutdown of main pump using operating procedure

Ensure all well injection wing valves are closed.

Monitor annulus pressure on PI-105923n to ensure that it remains within allowable operating range (0-310 barg)

Close UIMV

Close SCSSV

4

5

6

7

8

Re-open UIMV

Trend WHCIP on PI-105922n

Carry out flowline depressurisation back to FPSO using turret drain valve.

9 Continue to trend WHCIP for 1 hour after full depressurisation

10 Close UIMV & AIMV

Signature

SHUTDOWN NOTES:

On shut-down of the water injection system there are four key considerations:



The potential for a vacuum condition in the water injection system due to reservoir under-pressure.



Hydraulic surge due to closure of the wing valves, with the potential for exceeding the over-pressure allowances on some components, if the system is operated at above maximum steady state injection rate limits.



Closure of the wing valves against the main water injection pumps, leading to a transient under-pressure in the well which could damage the downhole sand screens.



Excessive wear of the water injection wing valve if it is closed against the main pump.

The inclusion of a carcass in the water injection risers and subsea flexible jumpers allows for vacuum conditions to exist in the system without the potential for collapse of the internal liner in these components. However, the system should be operated with the intention of minimising the potential for this condition.

This is primarily aimed at reducing the time taken to restart the system, but also provides assurance against collapse of the polyethylene liner within the water injection flowlines.

A similar philosophy to that used on the system start-up will be employed for a planned shutdown. Therefore, the main pumps will initially be shutdown whilst maintaining the water supply by using the produced water booster pumps or seawater lift pumps. This will be followed by closure of all wing valves and then shutdown of the produced water booster pumps or seawater lift pumps.

For an unplanned shut-down the water injection tree wing valves will be automatically closed on loss of al l water injection pumps.


4.13.2 Emergency Shutdown

In the event of an ESD/HIPS, the system is shutdown in the same way as for a normal shutdown with the exception that XXV-441002 (seawater inlet) is also closed. Once the cause of the shutdown has been investigated and rectified, the valves can be reset. XXV-441040 and XXV-441002 must be reset manually while the other valves are auto-reset. Additionally, there is a water injection PSD, refer to C&E L-8000-JC-0002.24.

An emergency shutdown affects the subsea tree valves as follows:

Yellow Shutdown









Red Shutdown

IWV closes

UIMV closes

AMV closes

XOVT closes as Yellow Shutdown above, but in addition -

 SCSSV closes


4.14 Water Injection Pump P-45001D & Turbine Shutdowns



The CRT may initiate a Normal Shutdown from the CCR or LER. The gas turbine will trip to idle speed, which will be indicated on the start up graphics. When the turbine remains in idle speed for 180 minutes, it will be totally stopped. If the CTR initiates “request to restart feed forward”

XHS-450455 before this time, the CPS logic will bring the pump automatically back on line.



The CRT may Fast Stop the turbine using XHS-450456 from the CPS

(see Control System Stop , below). The CPS logic will send a signal to

TCP S511-1 to trip the turbine to full stop. When the turbine comes to a full stop the CPS system will turn off the fuel gas superheater and shut valve XV-850005 instantaneously, XV-450446 and XV-450501 will close after a 30 second delay. (Note this does not depend on a return of a turbine full stop signal. This will happen on detection of ‘Fast stop the turbine’ XHS-450456). As XV-450446 closes, flow rate through the pump reduces and FIC-450445 will open under PID control to protect the pump from damage at low flow rates.



The operator may Emergency Stop the turbine from the TCP in the LER or from two different locations outside of the skid. The TCP will total stop the turbine, the Solar Turbine Control Panel will send a signal to the CPS and will be indicated on the start up graphics.

The turbine can be stopped from the CCR or LER, push buttons on the skid or by the control system. The system has the following stop functions:



Normal Shutdown from the CCR or LER, or Trip Turbine to Idle Speed from the CCR - the turbine will trip to idle speed, run for 3 hours and total stop



Manual Emergency Stop from the LER or from skid pushbuttons - the turbine will total stop



Control System Stop



Back-up Active Shutdown



Turbine Enclosure Fire Detection



Turbine Overspeed


4.14.1 Normal Shutdown or Trip Turbine to Idle Speed

Normal shutdown involves a cool down period in which the engine runs at idle speed for a preset time before the fuel is cut off and the engine coasts to a stop.

This can be done as follows:

 By activating the “Normal Stop” switch (S111) on the Turbine Control

Panel, or

 “Request to trip turbine to idle” from the Central Control Room.

This will be indicated by “Cool down” on the start-up screen for the pump in the

CCR. The Solar/Silvertech control systems will trip the gas turbine to idle speed, reset speed controller to 70% of turbine design speed, run for 180 minutes and total stop. The pump can be brought back on line by ac tivating the “request to restart feed forward” button on the start-up screen for the turbine in the central control room. After the engine coasts to a stop and the rundown timer expires, a preset lubrication cycle will be initiated.

When the gas turbine is brought to idle speed or a total stop, the CPS will initiate the following for the water injection pump P-45001D:

Tag Number

P-45001D

XV-450446

XV-450501

Description

4 th Water injection pump

Pump discharge valve

Pump discharge equalisation valve

Action

Stopped

Closed after a timer delay of 30 seconds

Shut

The system control valves can be moved to their shutdown position thus:

Tag Number Description Action

FCV-450445 Pump minimum flow valve Open

4.14.2 Manual Emergency Stop

The manual emergency stop is initiated by depressing the local, remote, or skidmounted emergency stop switch. When the stop is initiated, the start/run latch in the microprocessor is reset and the fast stop latch in the backup control is set.

Fuel valves and guide vanes are closed and the bleed valve is opened. The backup system controls lubrication oil for engine rolldown and post-lube. An emergency stop does not include a cool down period, which allows the engine to run with no load for a preset period before the engine is stopped. The emergency stop shutdown should only be used when plant conditions require an immediate shutdown. This can be done by:

 Activating the “emergency stop” switch (S112-A or S112-B) on the

Turbine Control Panel in the LER, or by



Activating o ne of the two “emergency stop” switches (S522 or S522A) on the skid.

“Gas Turbine to Full Stop” will indicate on the start-up screen for the pump in the

CCR. The engine shuts down immediately with no cool down cycle. After the engine stop, the post lubrication cycle will be initiated.


When the gas turbine is brought to a total stop, the CPS will initiate the following for the water injection pump (P-45001D):

Tag Number

P-45001D

XV-450446

XV-450501

Description

4 th Water injection pump

Pump discharge valve

Pump discharge equalisation valve

Action

Stopped

Closed after a timer delay of 30 seconds

Shut

The CPS will initiate the following for the water injection pump P-45001D driver:

Tag Number

XV-850005

XS-850003

Description

Fuel Gas Valve

Fuel Gas Heater ETP 85002

Action

Closed

Trip

The system control valves can be moved to their shutdown position thus:

Tag Number Description

FCV-450445 Pump minimum flow valve

Action

Open

4.14.3 Control System Stops

There are two main types of control system stops, depending on the severity of the malfunction and urgency to stop the GT or pump:



cooldown stop (cooldown non-lockout & cooldown lockout)



fast stop (fast stop non-lockout & fast stop lockout)

If an unsafe operating condition is detected by the control system, the control system will initiate a shutdown. Depending upon the severity of the shutdown, the control system will initiate either a cooldown stop or a fast stop. If the control system stop was initiated due to a condition that is self-correcting, the engine can be restarted after the condition returns to normal. If the control system stop was initiated due to a condition that is not self-correcting, contact maintenance personnel to perform corrective actions.

The Cooldown Stop unloads the driven equipment and allows the engine to idle for a cooldown period before shutting off fuel. The Fast Stop immediately shuts off fuel and unloads the driven equipment.

A Lockout inhibits control system operation. The control system cannot initiate a start until the malfunction is reset. Lockout-type malfunctions are generally more severe and require attention before the system can be restarted. Non-lockout malfunctions typically result from an operation disruption or an abnormal condition. Non-lockout malfunctions can be reset when conditions return to normal.


Cooldown Stop

If a cooldown stop has been initiated, the engine is shut down in the same manner as a normal stop. There are two types of cooldown stops; cooldown nonlockout and cooldown lockout.

 Cooldown Stop Non-lockout (CN) – Cooldown non-lockout shutdowns reduce engine speed to idle for a preset cooldown period before initiating a shutdown. Cooldown non-lockout shutdowns include operator-initiated normal stops, operating conditions that reached a shutdown limit because maintenance was not performed, a momentary disruption that causes an outof-limits condition, and operating conditions that exceed alarm levels but are not serious enough to cause any immediate damage. The turbine control system will automatically acknowledge and reset the cooldown non-lockout shutdowns and the turbine can then be started from the CCR without corrective action. Cooldown stop nonlockouts include normal stops as well as stops responding to alarms not serious enough to cause immediate damage.

These conditions include operation out of sequence, or a momentary out of limit condition.



Cooldown Stop Lockout (CL) - Cooldown lockout shutdowns reduce engine speed to idle for a preset cooldown period before initiating a shutdown.

Cooldown lockout shutdowns typically result from a component failure and not because operating conditions have exceeded alarm or shutdown levels.

Cooldown lockout shutdowns may not present immediate danger, but corrective action must be taken to avoid damage resulting from a component failure. When lockout shutdowns occur, the turbine can not be started until the shutdown is acknowledged and reset using the local acknowledge and reset switches.

Cooldown stop lockout shutdowns typically result from a component failure and not because operating conditions have exceeded alarm or shutdown levels.

Cooldown stop lockout malfunctions include:





 sensor failure lube tank level low lube tank overpressure

Fast Stop

If a fast stop has been initiated, the engine is shut down in the same manner as an emergency stop. There are two types of fast stops; fast stop lockout and fast stop non-lockout.



Fast Stop Lockout (FL)

Fast stop lockout shutdowns initiate an immediate shutdown of the engine and prevent package operation until the shutdown is acknowledged and reset using the local acknowledge and reset switches.

In addition to using the local acknowledge and reset switches, fast stop lockout shutdowns initiated due to a microprocessor failure, fire detection, backup overspeed, or pressing of emergency stop switch will require the backup relay system to be reset. Fast stop lockout shutdowns are the most severe shutdown types and require corrective action before the package can be restarted.


Fast stop lockouts respond to conditions that can cause serious damage if operation continues. Investigation for damage is required. Corrective action may be required before restart. These conditions include high bearing temperatures, high T5 temperature, node failure, transmitter failures, pump high thrust bearing temperature, gearbox high thrust bearing temperature, pump high vibration and gearbox high temperature.

WARNING: When a fast stop shutdown has been initiated due to fire detection, the post-lube oil pump will remain energised for a preset rundown period. After the preset rundown period expires, the post-lube oil pump will be de-energized for 20 minutes. After the 20 minute time period expires, the post-lube pump will cycle on and off for a preset post-lube period. If unsafe conditions still exist, the operator must manually abort the post lube cycle by opening the contactors for the post-lube and back-up lube oil pumps.

 Fast Stop Non-lockout (FN)

Fast stop non-lockout shutdowns initiate an immediate shutdown of the engine. Fast stop non-lockout shutdowns typically result from a disruption in operation due to abnormal operating conditions and may not require corrective action.

The turbine control system will automatically acknowledge and reset the fast stop non-lockout shutdowns and the turbine can be re-started from the CCR without corrective action.

Fast stop non-lockouts respond to conditions that can cause damage if operation continues. The conditions are caused by a momentary disturbance in the system or an occasional sequencing related malfunction. Momentary conditions typically include engine overspeed, flameout and high vibration

(engine). Sequencing-related malfunctions include fail to crank, ignition fail, fuel valve check fail, yard valve fail, and pre-lube fail.

4.14.4 Backup Active Shutdown

The backup active shutdown is enabled if there is a microprocessor failure, fire, backup overspeed, or manually initiated Emergency Shutdown (ESD). The backup system immediately shuts off fuel, opens system valves to eliminate driven equipment load, and controls lubrication oil for engine rolldown and postlube. After a backup active shutdown, the backup system must be reset with the

BACKUP RESET keyswitch. The ACKNOWLEDGE and RESET switches must be pressed before the package can be restarted.

Microprocessor Fail

A microprocessor fail malfunction is detected by the controller. When microprocessor failure is detected, a fast stop is initiated and backup control is activated. Fuel valves and guide vanes are closed, the bleed valve is opened, and the gas driven equipment is unloaded. The backup system controls lubrication oil for engine rolldown and post-lube.


4.14.5 GT Enclosure Fire Detection

When fire is detected, the backup system immediately sets the fast stop latch in backup control. The shutdown sequence proceeds as with the manual emergency stop except enclosure fans, are stopped, and lube continues for engine rolldown. If the PLC is functioning after the 20-minute hold, a post-lube cycle is completed.

4.14.6 Turbine Backup Overspeed

The turbine overspeed malfunction is sensed by the backup overspeed detection module. The magnetic pickup speed sensor is independent from primary control sensor. The backup overspeed monitor detects overspeed that indicates the normal control and protect systems are not operating. When overspeed is detected, the fast stop latch in the backup control is set and the stop sequence proceeds as with manual emergency stop.

4.15 Isolation for Maintenance

Water injection pump P-45001D is provided with discharge double block and bleed isolation and suction single isolation. The other three water injection pumps P-45001 A/B/C are only provided with discharge single isolation. To achieve positive isolation for maintenance of water injection pumps P-45001

A/B/C, a blank flange is to be fitted to the discharge non-return valve, when the water injection pump P-45001D is in operation.

WARNING: In case of an instrument air failure and if maintenance on the turbine fuel gas system is required, an entrapped pressure will occur and care should be taken on opening up the system for maintenance.

To achieve positive isolation for maintenance of the turbine:



Valve HV-520503 for the warm up line to flare has to be closed



Valve HV-804807 for the instrument air has to be closed



HV-815500 & HV-815501 for the cooling medium system have to be closed.

4.16 Winterisation

The demineralised water line to the wash cart should be emptied of water when the temperature falls below 5 deg C, to prevent freezing in the pipe, by opening valve HV-803709 (P&ID: 37W022F0146-A-8000-GP-0090.01-2C). There are two sets of drain water traps underneath both the HVAC (two traps) and combustion air Intakes (one trap) that are not winterised. A TQ has been raised to have these winterised.


4.17 Video Display Computer Operation

Use the following procedures to start up and shut down the video display computer and TT4000 software.

Start-Up of Computer

1.

2.

Switch on power to computer to start up Windows program.

When prompted to begin login: a. b. c.

Press Ctrl+Alt+Delete

Type user name Operator

Type password 1111 (four ones) and press Enter.

Start-Up of TT4000

1.

2.

3.

4.

5.

6.

From desktop, double-click TT4000 Designer icon.

From menu bar, click File.

From File pull-down menu, click Open Project.

Click C:\Jobs\70981\70981.ttprj.

From tool bar, click green Run button (right arrow).

NOTE: Project may take several minutes to load.

If “Server Busy” window pops up, click on Retry button.

Shutdown of TT400

1.

2.

3.

4.

5.

Move pointer arrow to bottom of screen. From Desktop Taskbar, click

TT4000 Designer Application button.

From toolbar, click red Stop button (square).

NOTE: Project may take several minutes to stop.

If “Server Busy” window pops up, click on Retry button.

From File pull-down menu, after Project has stopped, click Close Project.

When Project has closed, click Close button (X) at top right corner.

Shutdown of Computer

1.

2.

3.

4.

From Desktop taskbar, click Start button (bottom left corner).

From menu listing, click Shut Down (bottom of listing).

Select Shut down the computer and press Enter.

Wait for message. It is now safe to turn off your computer to appear.

Finally, switch off power to computer.


5. CONTROL & MONITORING

5.1 Subsea Control and Monitoring

The water injection system subsea is normally controlled and monitored from the operator workstation console within the CCR. The subsea control system is designed to be a ‘stand alone’ system to the normal process control system

(CPS), with a simple data hand-off system which allows the CPS to monitor any subsea data points as required.

The Master Control Station (MCS) provides appropriate well status indication to the CPS only if the CPS requests the information over the data hand-off system.

The information passed to the CPS is not employed by the CPS but is passed directly to the production information system. Any information displayed on the

CPS is indirectly obtained via the production information system.

Other topsides equipment supplied are the Hydraulic Power Unit (HPU), which provides the appropriate hydraulic pressures for subsea distribution, and the

Topside Umbilical Termination Unit (TUTU), which provides the interface between the umbilical systems and the platform cabling and piping. There is one TUTU for the Schiehallion Central, West & Gas Disposal Well (GDW) developments, and a second TUTU for the Schiehallion North and Loyal developments.

Two dynamic umbilicals are used to transport the electrical power, control signals and hydraulic supplies to the subsea systems. ROV installed and recoverable

Electro/Hydraulic/Chemical (E/H/C) jumpers are used to distribute the various supplies to the Subsea Control Modules (SCM) mounted on the Xmas Tree (XT).

The SCM is mounted on the XT via an ST001 ‘John Brown’ standard interface.

The SCM utilises through-base hydraulic and electrical connections which connect to the XT mounted E/H/C supplies stabplate and the Xmas Tree valves and instrumentation.

From the Umbilical Termination Assembly (UTA) or manifold, an E/H/C supplies jumper connection to each Xmas Tree. This jumper includes the following.



A dual power pair and a dual communications pair to the SCM.



A dual HP/MP hydraulic hoses to the SCM.



One multi-core cable for readback at the SCM of up to 3 off 4-20mA sensors on the manifold (valve position sensor, pressure and temperature sensor).


5.1.1 Interlocks

Interlocks serve to reduce valve wear. Interlocks when the MCS is in

OPERATOR mode are:

 Wing valve cannot be opened unless the Upper Master Valve is open

 Upper Master Valve cannot be opened or closed unless Wing Valve is closed

 SSSV cannot be opened unless upper master valve and wing valve are open

 SSSV cannot be closed unless the upper master valve is closed.

Note: When the MCS is set to SUPERVISOR mode, these interlocks can be overridden with the exception of the opening of the SCSSV, which can still only be opened if the wing valve and the upper master valve are open.

For the SCSSVs that share the same valve function, the upper master valves and wing valves on both trees must be open to enable the

SCSSV to be opened.

The SCSSV must not be opened until a positive indication of flow is obtained from the injection well venturi flow measurement. This protects the valve from being opened against a high differential pressure which could cause damage to the valve. Once flow is indicated, identifying that the pressures have equalised and the flapper type valve has opened, hydraulic pressure should be applied by opening the valve from the control system.

Water injection maintains reservoir pressure to minimise loss of productivity and maintain reservoir above the bubble point. The subsea water injection system is normally controlled and monitored from the operator workstation within the CCR. The subsea control system is a stand-alone system to the normal (topsides) process control system.

The Master Control System (MCS) can provide the CPS with well information if requested from the CP.

INDICATIONS, ALARMS AND TRIPS SUBSEA

Location Tag No.

Swivel - upstream of the water injection PG 450 803 manifold

Swivel - upstream of the 10” ball valves FE 180 800A

FE 180 800B

(Central Riser)

FE 182 800A

FE 182 800B

(West/North/Loyal Riser) dP sss929n xtree - venturi meter at the inlet to the xtree block xtree - downstream of the wing valve PTT sss922n

Instrument Type

Pressure Gauge

Flow Element

Flow venturi xtree - downstream of the cross over valve (tree) COVT

PT sss923n

Pressure/ Temperature

Transmitter

Pressure Transmitter

Table 11 Locations of Instruments on the Water injection system


The following table explains what the setting is for each instrument on the xtree.

Instrument

PTT d/s IWV

Design

PTT d/s IWV

Design

PT

@ XOUT

Design

FT

Design

PI on MP hydraulic supply

Design

PI on HP hydraulic supply

Design pressure

0/ 380 bara temperature

-30/ 80



C pressure

0/ 380 bara flowrate

0/ 331m 3 /d pressure

0/ 569 bara pressure

0/ 569 bara

Setting on the Alarms

HiHi Hi

Indicates that the pressure nearly at the design pressure of the system

Indicates that the pressure is approaching the design pressure

Indicates that the temperature near the maximum design temperature of the risers

Annulus pressure near the maximum operating pressure none none none

Indicates that the temperature approaching the maximum design temperature of the risers

Annulus pressure approaching operating pressure none none none

Lo

Indicates the pressure is getting near to the riser drawing a vacuum

Indicates that the temperature approaching the minimum design temperature of the risers

Annulus pressure near min. operating pressure none

Low pressure on

MP hydraulic supply; valves are closing , and should be closed under controlled manner

Low pressure for the HP hydraulic supply, close the valves in controlled manner

LoLo

Indicates that the riser has drawn a vacuum

Indicates that the temperature near the minimum design temperature of the risers

Annulus pressure near min. operating pressure none

Valves closing.

Hydraulic valves should be closed

Valves closing.

The valves should be closed.

Table 12 Indication of Alarm Setting on the Xtree

For alarms set on each xtree see Doc: Schedule of Alarm Settings, Doc No: S-9000-GY-9200.

5.2 Control & Monitoring of Water Injection System

The settings for normal operation of the water injection system are:

Deaeration Tower

FIC-441001

FIC-441019

PIC-441021

Stripping Gas Regeneration

Set by FIC-441019

945 m 3 /hr (minimum flow)

5 barg

FIC-441027

TIC-442014 & 5

FIC-441001

Water Injection Pumps P-45001A/B/C

98 - 140 kg/hr

150



C

40 – 60 litres/hr

FIC 450145

FIC 450245

FIC 450345

750 m 3 /hr design

750 m 3 /hr design

750 m 3 /hr design


5.3 Monitoring of Pump P-45001D & Gas Turbine

These parameters can be monitored on the inlet and outlet of the pump.

Monitoring

P-45001D suction pressure

P-45001D discharge pressure

P-45001D flow rate

P-45001D minimum flow valve position

P-45001D main discharge valve position

P-45001D bypass valve position

Device Location

PI-450441

PI-450443

FIC-450445

ZI-450445

Remote

Remote

Remote

Remote

ZLH/ZLL-450446 Remote

ZLH/ZLL-450501 Remote

Figure 16 Pump D Monitoring

Ref. P&ID: 37W022F0146-l-8000-GP-0046.03-2C

The Turbine Control Panel (TCP) in the LER controls the turbine, the gearbox and pump P45001D.

The CCR controls the turbine control panel, valves on the valve access platform and the fuel gas system.

The following hardware connections exist between TCP and CCR:



Permissive to start turbine from TCP



Request to start turbine from CCR



Trip gas turbine to idle speed from CCR



Cool down indication from TCP



Request to fast stop the turbine from CCR



Speed control of the turbine from CCR



Ready to load indication from TCP



Fast stop indication from TCP



Turbine Full Stop from TCP

Monitoring of pre-selected operating data for turbine, gearbox and pump will be carried out by using a serial link between TCP and CCR.


The Solar TCP in the LER has the following functions:

Lamps:

Ready light illuminated indicates that the turbine is ready to start.

Starting & Local/Remote split-type, dual-function indicator. The correct mode is selected by rotating the Off/Local/Remote switch. Normal operation is remote.

Cool down light illuminated indicates that Normal stop switch has been pressed.

Stopping light illuminated indicates that normal, emergency or control system stop has been initiated.

Alarm Summary light illuminated indicates an alarm condition. The light remains on until condition is cleared and system is reset.

Shutdown Summary light illuminated indicates that the shutdown was initiated manually or automatically. The light remains on until control system is reset.

Back-up Active light illuminated indicates that the backup relay system has been activated by the following events:











Failure of microprocessor

Detection of fire

Detection of engine overspeed by backup overspeed monitor

Pressing of emergency stop switch.

The backup relay system will maintain lube oil pump operation to avoid possible damage to the engine or driven equipment.

Switches:

Off/Local/Remote switch can be in the following positions:

Off: start sequence is inhibited.

Local: Turbine can be operated from the LER, but this is FORBIDDEN.

Remote: Turbine should only be operated from CCR, normal operation. The

Turbine MUST NOT be operated from the LER.

Rotating the switch to the off position when the unit is operating will initiate a control system stop of the engine with no cool down cycle.

The key to the panel is held in the CCR and is only released under a Permit to

Work.

Th e key is only required if “Cool-down Lockout “ or “Fast Stop Lockout” occur, and for maintenance.


Pushbuttons:

Emergency stop: This initiates immediate engine shutdown, with no cool-down cycle.

Horn Silence: This initiates the silence Audible Alarm Horn after an alarm or shutdown has occurred. Additional alarm or shutdowns will re-activate the alarm horn. To re-activate the horn silence, the button has to be pressed.

Acknowledge: This initiates the acknowledgement of alarms or shutdown and activates the Reset switch, which allows the system to be reset when an alarm or shutdown becomes inactive.

Reset: This initiates clearing of alarms or shutdown indicators, and the reset control system.

Start is permitted only if shutdowns are inactive and the control system has been reset.

Lamp Test: This initiates illumination of all indicator lights. If all of the lights are illuminated it indicates that all of the light circuits are intact.

Other Switches:

Back-up Reset: Rotary, two-position (off, on) switch, rotated clockwise to reset the back-up relay system. The back-up relay system cannot be reset until after the acknowledge and reset buttons are pressed. The back-up light will indicate when the back-up relay system has been reset.

Normal Stop: This initiates the cool down stop sequence. The engine speed is reduced to idle speed. Idle speed is maintained for a pre-selected cool down time before fuel gas is shut off and the engine shuts down.

Start: The Start switch on the local panel has been disabled and can only be started from the CCR.

Auto/Manual: Split type, dual-function switch, with individual indicator lights, illuminates to indicate mode selection. This switch should ALWAYS be in Auto.

Decrease: This initiates a decrease of speed from the LER, this is FORBIDDEN.

Increase: This initiates an increase of speed from LER, this is FORBIDDEN.


Engine Gauge Panel

The engine gauge panel has the following instruments: o Lube Oil Filters Differential Pressure Gauge

Indicates differential pressure across the engine lube oil filter. o Lube Oil Pressure Gauge

Indicates lube oil header pressure. o Engine Compressor Discharge Press Gauge

Indicates engine compressor discharge pressure. Operating pressure varies based on engine speed and inlet air temperature. o Lube Oil Temperature Gauge

Indicates lube oil header temperature. o Gas Fuel Pressure Gauge

Indicates the pressure of fuel gas prior to the primary shutoff valve. o Turbine Starting Horn

The Horn sounds the alarm for a preset period to alert the operator that a start sequence has been initiated. The Alarm is silenced when the preset time period expires.

Figure 17 Solar Local Control Panel

Ref. P&ID: 37W022F0146-l-8000-GP-0090.04/05/06/07-2C.


Figure 18 Solar Local Control Panel (showing emergency stop)

The following parameters can be monitored for the gas turbine:

Monitoring

Permissive to start

Start/Restart to Idle from CCR

Ready to Load

Trip to idle from CCR

Trip to Idle from CCR

Trip gas turbine to full stop.

Fuel Purge

Start Initiate

Starting

Purge Crank

Ignition

Light Off

Running

On Load

Stopping

Post Lube

Fast stop remote from CCR.

Power turbine speed

Gas turbine air inlet

Gas turbine inlet filter delta P

XI-450456

SI-450405

TI-450422

PDI-450401

Gas turbine inlet filter delta P PDI-450402

Gas turbine compressor discharge pressure PI-450432

Gas turbine T5 average

Gas turbine T5 max-T5 average

Fuel gas rate

Fuel gas pressure

Fuel gas temperature

Normal stop

Power turbine BRG 5-X-axis

TI-450433

TI-450434

FI-850005

PI-450433

TI-850099

XI-450419

YI-450415X

Device

XI-450407

XI-450440

XI-450430

XI-450409

XI-450410

XI-450411

XI-450412

XI-450413

XI-450414

XI-450415

XI-450416

XI-450417

XI-450418

XI-450420

XI-450421

XI-450422

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Location

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote


Monitoring

Power turbine BRG 5-Y-axis

Power turbine axial

Power turbine trust bearing



Gas producer NGP PV







Gas producer axial

Gas producer trust bearing

Device

YI-450415Y

YI-450412

TI-450450417

YI-450407X

YI-450407Y

SI-450406

YI-450408X

YI-450408Y

YI-450409X

YI-450409Y

YI-450410X

YI-450410Y

YI-450411

TI-450431

The following parameters can be monitored for the gearbox:

Location

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Monitoring

Thrust Brg Outboard Temp RDN

Thrust Outboard Brg Temp

LSS NDE End Bearing Temp

Axial

Accelerator

HSS DE End Bearing Temp

Bearing HSS Y Axis

Bearing HSS X Axis

Bearing LSS Y Axis

Bearing LSS X axis

LSS DE End Bearing Temp

Thrust Inboard Brg Temp RDN

Thrust Inboard Bearing Temp

Device

TI-450414B

TI-450414A

TI-450412

ZI-450405

XI-450408

TI-450410

YI-450405Y

YI-450405X

YI-450406Y

YI-450406X

TI-450413

TI-450415B

TI-450415A

HSS NDE End Bearing Temp TI-450411

The following parameters can be monitored for the start motor:

Location

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Monitoring

Start motor voltage

Start motor current

Start motor speed

Device

XI-450424

XI-450423

SI-450407

The following parameters can be monitored for the accessory gearbox:

Location

Remote

Remote

Remote

Monitoring

Accessory Gearbox

Device

XI-450428

Location

Remote


The following parameters can be monitored for the lube oil:

Monitoring

Lube Oil Header Temperature RDN

Lube Oil Header Temperature

Lube Oil Header Pressure RDN

Lube Oil Header Pressure

Lube Oil Filter DP

Lube Oil Pre Post Pressure

Lube Oil Tank Temperature

Lube Oil Tank Pressure

Lube Oil Tank Level

Accessory Gearbox bearing drain temp

Gas Producer Bearing Drain temp

Gas Producer Bearing Drain Temperature

Device

TI-450424

TI-450425

PI-450434

PI-450435

PDI-450405

PI-450436

TI-450426

PI-450437

LI-450401

TI-450427

TI-450428

TI-450429

Power Turbine Bearing Drain Temperature

Scavenge Pump Pressure

Back-up Lube pressure Test

TI-450430

PI-450438

PI-450439

The following parameters can be monitored for the enclosure:

Monitoring

Enclosure Primary Vent Fan

Enclosure Temperature

Enclosure Back-up Vent Fan

Enclosure Pressure

Enclosure Filter DP

Device

XI-450426

TI-450432

XI-450427

PI-450420

PDI-450404

The following parameters can be monitored for WI pump P-45001D:

Location

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Location

Remote

Remote

Remote

Remote

Remote

Monitoring Device

WI DE Vibration

WI Pump DE Vibration

WI Pump DE Seal Pressure

WI Pump NDE Seal Pressure

YI-450400X

YI-450400Y

PI-450416

PI-450417

WI Pump DE Journal Bearing Temperature TI-450405

WI Pump NDE Journal Bearing Temperature TI-450406

WI Pump NDE Vibration

WI Pump NDE Vibration

WI Pump I/B Thrust Bearing Temperature

WI Pump O/B Thrust Bearing Temperature

YI-450401Y

YI-450401X

TI-450407

TI-450408

WI Pump Balance Return Line Temperature TI-450409

Location

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

Remote

WI Pump Speed

Pump HP (Indicated in MW)

SI-450404

XI-450425

Remote

Remote

Figures 19-21 show the graphic display screens for the gas turbine where the following parameters can be monitored:



Pump power



Enclosure pressure & temperature



Enclosure vent fan on/off



Enclosure Filter DP



Gas turbine not running or running. When the speed of turbine is less than 5% of the design speed, this will be indicated as not running



Gas turbine air inlet filter DP



Operating data in the fuel gas system.


Figure 19 4 th Water Injection Pump Gas Turbine Graphic Display

Figure 20 Gas Turbine Monitoring & Lube Oil System Graphic Display


Figure 21 Gas Turbine to 4 th Water Injection Pump Gearbox Graphic Display


6 ALARMS AND SHUTDOWNS

6.1 De-aerator HIPS

The de-aerator HIPS shutdown valves XXV-441002 and XXV-441040 must be manually reset following activation.

Note: When the seawater inlet shutdown valve XXV-441002 is used as part of an isolation, the air supply to the actuator should be locked off and disconnected.

A high-high level HIPS is installed on the inlet to the deaerator tower to prevent the column overfilling. The support pallet steelwork is adequate for the occasional (less than once a year) flooding of the tower, however, no appraisal for fatigue has been performed. Therefore, it is important that each flooding occasion is logged.

The HIPS is arranged as a level transmitter initiated a one-out-of-two voting system acting on two independent ESD valves and located on the inlet to the vessel. The HIPS level transmitters and shutdown valves are driven via the hardwired ESD system.

The deaerator also has a primary protection system in the form of a high high level shutdown switch acting on the upstream shutdown valve, XXV-441040, via a dedicated CPS solenoid. The primary shutdown system operates via the software based CPS system.

The HIPS comprises the following:

HIPS Transmitters High-high Setpoint

LT-441013

LT-441014

HIPS ESD Valves

3050 mm

3050 mm

First Valve

Second Valve

XXV-441002

XXV-441040 (via a dedicated ESD solenoid)

Primary Protection Transmitter High-high setpoint

LT-441032 2600 mm

Primary Protection Shutdown Valve

Upstream Valve XXV-441040 (via a dedicated CPS solenoid)

The HIPS is installed on the deaerator as the vessel relief valves are not designed for full seawater flow relief.


PSD Resets

Field inputs which have caused a trip, after the measurement goes healthy, require to be reset in the PSD system. This is achieved at the operator workstations as follows:

1. On “Main System” graphic select “PSD”, this will display “PSD

Shutdown/Reset Page”.

2. On this page all process systems status will be displayed, i.e. input trip, output trip etc. On this page against each process system there is a reset pushbutton. If all field inputs for the process are healthy, the reset can be pressed and the status of input trips should change from red to green.

Note: Any field inputs which require a start-up override, and are therefore active due to plant not running, require a start-up override applied before the reset is pressed.

SUBSEA AND WATER INJECTION TREES

Refer to Cause and Effect S-9000-GC-9002

Input Cause

Red Shutdown

Yellow Shutdown

Water Injection Pumps Trip

Input

F&G or Manually from CCR

F&G or Manually from CCR

PSD

Action

Closes all wells, wing valves, master valves, annulus valves, SCSSV and crossover valve.

Closes all wells, wing valves, master valves, annulus valves, SCSSV and crossover valve.

Closes wing valves.

Table 13 ESD actions on tree valves

Alarm

Deaerator tower de-aerated seawater

LAH-441010

Deaerator tower de-aerated seawater

LAL-441010

Deaerator tower seawater inlet

FAH-441001

Deaerator tower seawater inlet

FAL-441001

Deaerator tower seawater outlet

FAH-441019

Deaerator tower seawater outlet

FAL-441019

Deaerator tower pressure

PAH-441003

Deaerator tower pressure

PAL-441003

Deaerator tower temperature

TAH-441008

Deaerator tower temperature

TAL-441008

Departed seawater outlet oxygen content

AAH-441018

Departed seawater outlet chlorine content

AAH-441017

Input

LT-441010

LT-441010

FT-441010

FT-441010

FT-441019

FT-441019

PT-441003

PT-441003

TT-441008

TT-441008

AT-441018

AT-441017

Action

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS


Alarm

Purge system pressure PAH/L-441034

Purge system liquid leak

LAH-441033

Blower inlet pressure PAH-441021

Blower inlet pressure PAL-441021

Blower inlet hydrocarbon analyser

Blower P-44201A dp PDAH-442027

Blower P-44201A dp PDAL-442027

Blower P-44201B dp PDAH-442004

Blower P-44201B dp PDAL-442004

Blower P-44201A temp TAH-442002

Blower P-44201B temp TAH-442005

Blower outlet flowrate FAH-442008

Blower outlet flowrate FAL-442008

Heat exchanger outlet temp TAH-442014

Heat exchanger outlet temp TAL-442014

De-oxidiser V-44201 temp TAH-442015

De-oxidiser V-44201 temp TAL-442015

De-oxidiser V-44201 dp PDAH-442016

De-oxidiser outlet O2 content AAH-442019

Methanol Inlet flowrate FAH-442025

Methanol Inlet flowrate FAL-442025

Instrument air inlet

(process) mass flow FAH-441027

Instrument air inlet

(process) mass flow FAL-441027

Input

AT-441017

PS-441034

AT-441017

LS-441033

PT-441021

PT-441021

AT-441026

PDT-442027

PDT-442027

PDT-442004

PDT-442004

TT-442002

TT-442005

FT-442008

FT-442008

TT-442014

TT-442014

TT-442015

TT-442015

PDT-442016

AT-442019

FT-442025

FT-442025

FT-441027

FT-441027

Action

Purge controller in field

Purge controller in field

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

CPS

Alarm

Deaerator Tower Seawater

Level LAHHH-441013


Level LAHHH-441014


Level LAHH-441032


Level LALL-441015

Deaerator Tower Temperature

TAHH-44107

Blower Inlet Pressure

PAHH-441020

Blower Inlet Pressure

PALL-441020

Blower Outlet Flowrate

FAHH-442009

Blower Outlet Flowrate

FALL-442009

De-oxidiser V 44201 Temperature

TAHH-442018

De-oxidiser V-44201 Temperature

Thermostats (in series)

Heater Tube Sheet Terminal Box

De-oxidiser V-44201

Heater Element Temperature

De-oxidiser outlet Temperature TAHH-441030

De-oxidiser Outlet Oxygen Level AAH-442019

Input

LT-441013

LT-441014

LT-441032

LT-441015

TT-441007

PT-441020

PT-441020

FT-442009

FT-442009

TT-442018

TS-442017

TS-442016

TT-441030

AT-442019

Action

ESD

ESD

PSD

PSD

PSD

PSD

PSD

PSD

PSD

PSD

MCC

MCC

PSD

CPS


6.2 Pumps P-45001A/B/C Alarms & Actions

6.2.1 Pump P-45001A Alarms & Actions

Alarm

GEC Purgepak PM 45001A

(mounted on front of UCP) PAL-450163

Injection pump P-45001A

DE journal bearing vibration high

YAH-450100 x/y


DE journal bearing vibration high sensor fail YA-450100 x/y


NDE journal bearing vibration high YAH 450101 x/y

Injection pump P-45001A pump NDE journal bearing vibration high sensor fail

YA 450101 x/y

Injection pump motor

PM-45001A motor

DE journal bearing vibration High

YAH-450102 x/y


PM-45001A DE journal bearing vibration high sensor fail

YA-450102 x/y


PM-45001A NDE journal bearing vibration high

YAH-450103 x/y

Injection pump motor PM-45001A NDE journal bearing vibration high sensor fail

YA-450103 x/y


DE journal bearing

TAH-450105


DE journal bearing temperature sensor fail

TA-450105


NDE journal bearing

TAH-450106


NDE journal bearing temperature sensor fail TA-450106


I/B thrust bearing TAH-450107

Input

PT-450163

YT-450100X/Y

YT-450100X/Y

YT-450101X/Y

YT-450101X/Y

YT-450102x/Y

YT-450102x/y

YT-450103 x/y

YT-450103 x/y

TT-450105

TT-450105

TT-450106

TT-450106

TT-450107


I/B thrust bearing temperature sensor fail TA-450107

TT-450107

Action

EPS

ECP Mounted hardwired available in

CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

(contd)


6.2.1 Pump P-45001A Alarms & Actions (continued)

Alarm


O/B thrust bearing TAH-450108

Input

TT-450108


O/B thrust bearing temperature sensor fail TA-450108

Injection pump P-45001A balance return line temp TAH-450109

Injection pump motor PM-45001A air circuit temperature TAH-450110

TT-450108

TT-450109

TT-450110

TT-450110 Injection pump motor PM-45001A air circuit temp sensor fail TA-450110

Injection pump motor PM-45001A DE journal bearing temp high TAH-450111

Injection pump motor PM-45001A DE journal bearing temp sensor fail

TA-450111

Injection pump motor PM-45001A NDE journal bearing temp high

TAH-450112

Injection pump motor PM-45001A NDE journal bearing temp sensor fail TA-450112

Injection pump motor PM-45001A winding temp high

TAH-450113

Injection pump motor PM-45001A winding temperature sensor fail

TA-450113

Injection pump motor PM-45001A winding temperature high

TAH-450114


TA-450114

Injection pump motor PM-45001A winding temperature high

TAH-450115


TA-450115

Injection pump P-45001A DE seal pressure high

PAH-450116

TT-450111

TT-450111

TT-450112

TT-450112

TT-450113

TT-450113

TT-450114

TT-450114

TT-450115

TT-450115

PT-450116

Action


CCR via Data Link


CCR via Data Link

CPS


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

(contd)


6.2.1 Pump P-45001A Alarms & Actions (continued)

Alarm

Injection pump P-45001A DE seal pressure high pressure sensor fail PA-450116

Input

PT-450116


NDE seal pressure high

PAH-450117


NDE seal pressure high sensor fail

PA-450117

Injection pump motor PM-45001A coolant leakage level

LAH-450120

Injection pump P-45001A lube oil reservoir temperature TAH-450128

Injection pump P-45001A lube oil reservoir temperature TAL-450128

Injection pump P-45001A lube oil reservoir temperature sensor fail TA-450128

Injection pump P-45001A lube oil cooler outlet temperature

TAH-450131

Injection pump P-45001A lube oil supply pressure PAL-450134

P-45001A lube oil supply pressure sensor fail PA-450134

PT-450134

PT-450134

P-45001A lube oil supply pressure sensor fail PA-450135 PT-450135

P-45001A lube oil filter differential pressure PDAH-

450136

P-45001A lube oil filter differential pressure sensor fail

PDA-450136

P-45001A lube oil reservoir level LAL-450139

P-45001A lube oil reservoir level sensor fail LA-450139

P-45001A suction pressure alarm PAL-450141

P-45001A suction pressure alarm PAH-450141

P-45001A discharge pressure alarm PAL-450143

P-45001A discharge pressure alarm PAH-450143

Pump DE journal bearing vibration YAHH-450100 x/y

Pump NDE journal bearing vibration YAHH-450101 x/y





Motor Air circuit temperature TAHH-450110

Motor DE journal bearing TAHH-450111

Motor NDE journal bearing TAHH-450112

Motor winding temperature TAHH-450113



Lube oil supply pressure PALL-450135

PT-450117

PT-450117

LT-450120

TT-450128

TT-450128

TT-450128

TT-450131

PT-450136

PT-450136

LT-450139

LT-450139

PT-450141

PT-450141

PT-450143

PT-450143

YT-450100

YT-450101

YT-450102

YT-450103

YT-450105

YT-450106

TT-450110

TT-450111

TT-450112

TT-450113

TT-450114

TT-450115

PT-450135

Action

ECP Mounted hardwired available in CCR via Data Link



ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator


ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

CPS

CPS

CPS

CPS

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ECP


6.2.2 Pump P-45001B Alarms & Actions

Alarm

GEC Purgepak PM-45001B

(mounted on front of UCP) PAL-450263

Injection pump P-45001B DE journal bearing vibration high

YAH 450200 x/y

Injection pump P-45001B DE journal bearing vibration high sensor fail

YA 450200 x/y

Injection pump P-45001B NDE journal bearing vibration high YAH 450201 x/y

Injection pump P-45001B NDE journal bearing vibration high sensor fail YA 450201 x/y

Injection pump motor PM-45001B

DE journal bearing vibration high

YAH-450202 x/y


DE journal bearing vibration high sensor fail YA-450202 x/y

Injection pump motor PM-45001B NDE journal bearing vibration high

YAH-450203 x/y


NDE journal bearing vibration high sensor fail YA-450203 x/y

Injection pump P-45001B

DE journal bearing TAH-450205

Injection pump P-45001B DE journal bearing temperature sensor fail TA-450205


NDE journal bearing TAH-450206

Injection pump P-45001B NDE journal bearing temperature sensor fail TA-450206


I/B thrust bearing TAH-450207

Injection pump P-45001B I/B thrust bearing temperature sensor fail

TA-450207


O/B thrust bearing TAH-450208

Injection pump P-45001B O/B thrust bearing temperature sensor fail TA-450208

Injection pump P-45001B balance return line temperature

TAH-450209

Injection pump motor PM-45001B air circuit temperature

TAH-450210

Injection pump motor PM-45001B air circuit temperature sensor fail

TA-450210

Injection pump motor PM-45001B DE journal bearing temperature high

TAH-450211

Injection pump motor PM-45001B DE journal bearing temperature sensor fail

TA-450211

Input

PT-450263

YT 450200X/Y

YT-450200X/Y

YT-450201X/Y

YT-450201X/Y

YT-450202x/Y

YT-450202x/y

YT-450203 x/y

YT-450203 x/y

TT-450205

TT-450205

TT-450206

TT-450206

TT-450207

TT-450207

TT-450208

TT-450208

TT 450209

TT-450210

TT-450210

TT-450211

TT-450211

Action

EPS


Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

Ditto

CPS


Ditto




6.2.2 Pump P-45001B Alarms & Actions (continued)

Alarm


NDE journal bearing temperature high

TAH-450212

Injection pump motor PM-45001B NDE journal bearing temperature sensor fail

TA-450212

Injection pump motor PM-45001B winding U temperature high

TAH-450213

Injection pump motor PM-45001B winding U temperature sensor fail

TA-450213

Injection pump motor PM-45001B winding V temperature high

TAH-450214

Injection pump motor PM-45001B winding V temperature sensor fail

TA-450214

Injection pump motor PM-45001B winding W temperature high

TAH-450215

Injection pump motor PM-45001B winding W temperature sensor fail

TA-450215


DE seal pressure high

PAH-450216

Injection pump P-45001B DE seal high pressure sensor fail

PA-450216



PAH-450217


NDE seal high pressure sensor fail

PA-450217

Injection pump motor PM-45001B coolant leakage LAH-450220

Injection pump P-45001B lube oil reservoir temperature

TAH-450228

Injection pump P-45001B lube oil reservoir temperature TAL-450228

Injection pump P-45001B lube oil reservoir temperature sensor fail TA-450228

Injection pump P-45001B lube oil cooler outlet temperature TAH-450231

Input

TT-450212

TT-450212

TT-450213

TT-450213

TT-450214

TT-450214

TT-450215

TT-450215

PT 450216

PT 450216

PT 450217

PT 450217

LT 450220

TT 450228

TT 450228

TT 450228

TT-450231

Injection pump P-45001B lube oil supply pressure PAL-450234

Injection pump P-45001B lube oil supply pressure sensor fail

PA-450234

Injection pump P-45001B lube oil supply pressure sensor fail

PA-450235

PT 450234

PT 450234

PT 450235

Action


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator


CCR via Data Link

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator


6.2.2 Pump P-45001B Alarms & Actions (continued)

Alarm

Injection pump P-45001B lube oil filter differential pressure PDAH-450236

Injection pump P-45001B lube oil filter differential pressure sensor fail

PDA-450236

Injection pump P-45001B lube oil reservoir level LAL-450239

Injection pump P-45001B lube oil reservoir level sensor fail LA-450239

Injection pump P-45001B suction pressure alarm PAL-450241

Injection pump P-45001B suction pressure alarm PAH-450241

Injection pump P-45001B discharge pressure alarm PAL-450243

Injection pump P-45001B discharge pressure alarm PAH-450243

Pump DE journal bearing vibration

YAHH-450200 x/y

Pump NDE journal bearing vibration

YAHH-450201 x/y


YAHH-450202 x/y


YAHH-450203 x/y


YAHH-450205 x/y


YAHH-450206 x/y

Motor air circuit temperature TAHH-450210






Lube oil supply pressure PALL 450235

Input

PT 450236

PT 450236

LT 450239

LT 450239

PT 450241

PT 450241

PT 450243

PT 450243

YT-450200

YT-450201

YT-450202

YT-450203

YT-450205

YT-450206

TT-450210

TT-450211

TT-450212

TT-450213

TT-450214

TT-450215

PT-450235

Action

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

CPS

CPS

CPS

CPS

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ECP


6.2.3 Pump P-45001C Alarms & Actions

Alarm

GEC Purgepak PM-45001C

(mounted on front of UCP)

PAL-450363

Injection pump P-45001C DE journal bearing vibration high

YAH-450300 x/y

Injection pump P-45001C DE journal bearing vibration high sensor fail

YA-450300 x/y

Injection pump P-45001C NDE journal bearing vibration high

YAH-450301 x/y

Injection pump P-45001C NDE journal bearing vibration high sensor fail

YA-450301 x/y

Injection pump motor PM-45001C DE journal bearing vibration high

YAH-450302 x/y

Injection pump motor PM-45001C

DE journal bearing vibration high sensor fail

YA-450302 x/y


NDE journal bearing vibration high

YAH-450303 x/y


NDE journal bearing vibration high sensor fail

YA-450303 x/y

Injection pump P-45001C

DE journal bearing

TAH-450305

Injection pump P-45001C DE journal bearing temperature sensor fail

TA-450305

Injection pump P-45001C NDE journal bearing

TAH-450306

Injection pump P-45001C NDE journal bearing temperature sensor fail

TA-450306


I/B thrust bearing

TAH-450307

Injection pump P-45001C I/B thrust bearing temperature sensor fail

TA-450307


O/B thrust bearing

TAH-450308

Injection pump P-45001C O/B thrust bearing temperature sensor fail

TA-450308

Injection pump P-45001C balance return line temperature TAH-450309

Input

PT-450363

YT 450300X/Y

YT-450300X/Y

YT-450301X/Y

YT-450301X/Y

YT-450302x/Y

YT-450302x/y


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

YT-450303 x/y

YT-450303 x/y


CCR via Data Link


CCR via Data Link

TT-450305

TT-450305

TT-450306

TT-450306

TT-450307

TT-450307

TT-450308

TT-450308

TT-450309

Action

EPS


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

CPS


6.2.3 Pump P-45001C Alarms & Actions (continued)

Alarm

Injection pump motor PM-45001C air circuit temperature

TAH-450310

Injection pump motor PM-45001C air circuit temperature sensor fail

TA-450310

Injection pump motor PM-45001C DE journal bearing temperature high

TAH-450311

Injection pump motor PM-45001C DE journal bearing temperature sensor fail

TA-450311

Injection pump motor PM-45001C NDE journal bearing temperature high

TAH-450312

Injection pump motor PM-45001C NDE journal bearing temperature sensor fail

TA-450312

Injection pump motor PM-45001C winding U temperature high

TAH-450313

Injection pump motor PM-45001C winding U temperature sensor fail

TA-450313

Injection pump motor PM-45001C winding V temperature high TAH-450314

Injection pump motor PM-45001C winding V temperature sensor fail TA-450314

Injection pump motor PM-45001C winding W temperature high

TAH-450315

Injection pump motor PM-45001C winding W temperature sensor fail

TA-450315


DE seal pressure high

PAH-450316


DE seal pressure high sensor fail

PA-450316



PAH-450317


NDE seal pressure high sensor fail PA-450317

Injection pump motor PM-45001C coolant leakage LAH-450320

Injection pump P-45001C lube oil reservoir temperature

TAH-450328

Input

TT-450310

TT-450310

TT-450311

TT-450311

TT-450312

TT-450312

TT-450313

TT-450313

TT-450314

TT-450314

TT-450315

TT-450315

PT-450316

PT-450316

PT-450317

PT-450317

LT-450320

TT-450328

Action


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link


CCR via Data Link

ECP Mounted

Annunciator

ECP Mounted

Annunciator


6.2.3 Pump P-45001C Alarms & Actions (continued)

Alarm

Injection pump P-45001C lube oil reservoir temperature TAL-450328

Injection pump P-45001C lube oil reservoir temperature sensor fail TA-450328

Injection pump P-45001C lube oil cooler outlet temperature

TAH-450331

Input

TT-450328

TT-450328

TT-450331

Action

ECP Mounted

Annunciator

ECP Mounted

Annunciator

Injection pump P-45001C lube oil supply pressure PAL-450334

Injection pump P-45001C lube oil supply pressure sensor fail PA-450334

Injection pump P-45001C lube oil supply pressure sensor fail PA-450335

Injection pump P-45001C lube oil filter differential pressure PDAH-450336

Injection pump P-45001C lube oil filter differential pressure sensor fail PDA-450336

Injection pump P-45001C lube oil reservoir level LAL-450339

Injection pump P-45001C lube oil reservoir level sensor fail LA-450339

Injection pump P-45001C suction pressure alarm PAL-450341

Injection pump P-45001C suction pressure alarm PAH-450341

Injection pump P-45001C discharge pressure alarm PAL-450343

Injection pump P-45001C discharge pressure alarm PAH-450343


YAHH-450300 x/y


YAHH-450301 x/y


YAHH-450302 x/y


YAHH-450303 x/y


YAHH-450305 x/y


YAHH-450306 x/y

Motor air circuit temperature TAHH-450310






Lube oil supply pressure PALL-450335

PT-450334

PT-450334

PT-450335

PT-450336

PT-450336

LT-450339

LT-450339

PT-450341

PT-450341

PT-450343

PT-450343

YT-450300

YT-450301

YT-450302

YT-450303

YT-450305

YT-450306

TT-450310

TT-450311

TT-450312

TT-450313

TT-450314

TT-450315

PT-450335


ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

ECP Mounted

Annunciator

CPS

CPS

CPS

CPS

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ESD via ECP

ECP


6.3 Pump P-45001D & Turbine Local and Remote Alarms

Ref. P&IDs: 37W022F0146-A-8000-GP-0090.05/06/07-2C

37W022F0146-A-8000-GP-0090.03-2C

Alarm Input

P-45001D pump vibration common alarm

P-45001D pump temperature common alarm

P-45001D pump seal pressure common alarm

Gearbox high temperature common alarm

Gearbox vibration alarm

P-45001D lube oil common alarm

Gas producer temperature common alarm

Fire & Gas common alarm

Gas producer vibration common alarm

Gas turbine other common alarm

Power turbine temperature common alarm

Power turbine vibration common alarm

Gas turbine start-up common alarm

Gas turbine common alarm

Alarm Summary (Package)

Gas turbine fast stop lockout alarm

Shutdown summary status (Package)

Gas turbine fast stop non lockout alarm

Gas turbine cool down lockout alarm

Gas turbine cool down non-lockout alarm

P-45001D Suction low pressure alarm

P-45001D Suction high pressure alarm

P-45001D Discharge low pressure alarm

P-45001D Discharge high pressure alarm

Water Injection Rate Low

Action

XA-450400 CPS

XA-450401 CPS

XA-450402 CPS

XA-450403 CPS

XA-450404 CPS

XA-450405 CPS

XA-450406 CPS

XA-450407 CPS

XA-450408 CPS

XA-450409 CPS

XA-450410 CPS

XA-450411 CPS

XA-450412 CPS

XA-450413 CPS

XA-450418 CPS

XA-450414 CPS

XA-450419 CPS

XA-450415 CPS

XA-450416 CPS

XA-450417 CPS

PI-450441 CPS

PI-450441 CPS

PI-450443 CPS

PI-450443 CPS

FIC-450445 CPS

NOTE: XA-450400 to XA-450412 are customized alarm groups. Predefined alarms in the LER are displayed in the CCR.


Figure 22 Lube Oil System Common Alarm Graphic

Figure 23 Gearbox Temperature & Vibration Common Alarm Graphic


Figure 24 Pump Temperature, Pressure & Vibration Common Alarm Graphic

Figure 25 Gas Turbine Common Alarm Graphic


Figure 26 Power Turbine Vibration & Temperature and

Gas Turbine Start-up Common Alarm Graphic

Figure 27 Gas Producer Vibration & Temperature and

Fire & Gas Common Alarm Graphic


SUCTION DISCHARGE

Figure 28 Water Injection Pumps P-45001C&D Graphic


6.4 Pump P-45001D Alarms, Actions, Shutdowns & Resets

The LER gathers information on pump and turbine controls and shutdowns, and fire & gas systems. There is also a connection to the ESD system in the LER via hardwires from the CCR. The fuel gas system ESD isolation is connected directly to the existing ESD system.

Ref. Cause and Effect: L 8000-JC-0002.24, L-8000-JC-0002.38

Input Cause

Injection pump P45001D suction pressure PAHH-

450442

Injection pump P45001D suction pressure PALL-

450442

Injection pump P45001D

Discharge pressure PAHH-

450444

Injection pump P45001D discharge pressure PALL-

450444

Injection pump P45001D low low flow FALL-450446

Injection pump P45001D Fuel gas system temperature

TAHH-850005

Injection pump P45001D Fuel gas system temperature

TALL-850005

Injection pump P45001D fuel gas system temperature

TALL-850006

Injection pump P45001D fuel gas system pressure PAHH-

850005

Input

PT-450442

PT-450442

PT-450444

PT-450444

FT-450446

TT-850005

TT-850005

TT-850006

PT-850005

Action

Intertrip to water injection system, close discharge XV-450446, equalisation XV-450501, fuel gas XV-

850005, trip fuel gas heater ETP-

85002 and fast stop gas turbine.



85002 and fast stop gas turbine


850005, open overboard dump valve

XV-450445, trip fuel gas heater ETP-

85002 and fast stop gas turbine










1 out of 2 voting (TT-850005 and TT-

850006). Intertrip to water injection system, close dischargeXV-450446, equalisation XV-450501, fuel gas XV-



1 out of 2 voting (TT-850005 and TT-

850006). Intertrip to water injection system, close discharge XV-450446, equalisation XV-450501, fuel gas XV-







Input Cause

Injection pump P45001D fuel gas system pressure PALL-

850005

Gas turbine trip to full stop, by fast or emergency stop.

Intertrip from existing fuel gas system.

Intertrip from water injection system

Input

PT-850005

Solar

CUST553

Intertrip

Intertip

Action

Intertrip to water injection system close discharge XV-450446, equalisation XV-450501, fuel gas XV-




850005 and trip fuel gas heater ETP-

85002.




Close discharge XV-450446, equalisation XV-450501, fuel gas XV-



Figure 29 Trips and Interlocks Graphic


Figure 30 Water Injection System Interlocks Graphic (1)

Figure 31 Water Injection System Interlocks Graphic (2)


6.5 Pumps P-45001A/B/C Shutdowns

Refer to Cause and Effect L 8000-JC-0002.24

Input Cause

Injection pump P-45001A suction pressure PAHH-450142

Injection pump P-45001A suction pressure PALL-450142

Injection pump P-45001A balance line TAHH-450109

Injection pump P-45001A discharge pressure PAHH-450144

Injection pump P-45001A discharge pressure PALL-450144

Injection pump P-45001A low-low flow FALL-450146

Injection pump P-45001B suction pressure PAHH-450242

Injection pump P-45001B suction pressure PALL-450242

Injection pump P-45001B balance line TAHH-450209

Injection pump P-45001B discharge pressure PAHH-450244

Injection pump P-45001B discharge pressure PALL-450244

Injection pump P-45001B low-low flow FALL-450246

Injection pump P-45001C suction pressure PAHH-450342

Injection pump P-45001C suction pressure PALL-450342

Injection pump P-45001C balance line TAHH-450309

Injection pump P-45001C discharge pressure PAHH-450344

Injection pump P-45001C discharge pressure PALL-450344

Injection pump P-45001C low-low flow FALL-450346

Yellow Shutdown

Input Action

PT-450142 Trip pump A via HV switchboard and close discharge XV-450146


TT-450109 Trip pump A via HV switchboard and close discharge XV-450146



FIT-450146 Trip pump A via HV switchboard and close discharge XV-450146

PT-450242 Trip pump B via HV switchboard and close discharge XV-450246


TT-450209 Trip pump B via HV switchboard and close discharge XV-450246



FIT-450246 Trip pump B via HV switchboard and close discharge XV-450246

PT-450342 Trip pump C via HV switchboard and close discharge XV-450346


TT-450309 Trip pump C via HV switchboard and close discharge XV-450346



FIT-450346 Trip pump C via HV switchboard and close discharge XV-450346

Trips water injection pumps

P-45001A/B/C/D and closes discharge valves


6.6 ESD Actions & Valve Closure Sequences

Valve

Water injection wing valve water injection master valve water injection annulus valve cross-over valve

SCSSV

Master Xtree

1

3

5

7

9

Slave Xtree

2

4

6

8

10

Table 14 Tree valve Closure Sequences

These sequences are typical for tree shutdown and follow directly from 1 to 10:



The master xtree shutdown would be in the sequence of 1,3,5,7,9 and the slave xtree in the sequence of 2,4,6,8,10.



The IWV sequence of valve closure would always be 1 followed by 2.



The UMIV valve closure could be 3 followed by 4 or 4 followed by 3.



The AMV valve closure: 5 and then 6 or 6 and then 5, etc.

The same typical and alternative shutdown sequences apply to all of the following tables. Table 15 shows the shutdown sequences for West and Loyal injection centres, which have two slave xtrees to a master xtree.

Valve Master Xtree First Slave

Xtree

1 2

Second Slave

3 Water injection wing valve water injection master valve water injection annulus valve cross-over valve

SCSSV

4

7

10

13

5

8

11

14

6

9

12

15

Table 15 Sequence of Master and Slave Xtree Shutdown

on Red ESD for West and Loyal Water Injection Drill Centres


6.6.1 Yellow ESD shutdown

The causes for a Yellow ESD shutdown for the water injection system are variable. On a Yellow ESD, the following order of valve shutdown would occur.

Sequence of

Valve closure

1

Time Delay after valve closed (s)

30

Valve Tag Number

IWVsss934n

2

3

4

15

15

90


UIMVsss933n

AMVsss935n

XOVTsss937n

Table 16 Sequence of Valve Shutdown on Yellow ESD

On a Yellow ESD, the sequences of master and slave xtree closure are shown in

Tables 17 & 18 below:

Valve


Master Xtree

1

3

5

7

Slave Xtree

2

4

6

8


on Yellow ESD for Central and North Water Injection Drill Centres

Valve Master Xtree First Slave

Xtree

1 2

Second Slave


SCSSV

4

7

10

13

5

8

11

14

3

6

9

12

15


on Yellow ESD for West and Loyal Water Injection Drill Centres

6.6.2 Water Injection Pump Trip PSD

On a water injection pump trip PSD only the IWV on the xtree will shut. The sequence of master and slave xtree will be as before, namely the master xtree closing first followed by the slave xtree(s).


6.7 DESIGN PARAMETERS

The design flowrates for existing drill centres and water injection wells are:

Design Flowrate (mbpd) maximum well flowrate design drill centre flowrate allowable drill centre flowrate

Table 19 Design Water Injection Flowrates

Pressure Parameters

Location

Schiehallion

Central

50

140

154

Schiehallion

West

50

100

96

Schiehallion

North

50

100

149

FPSO riser base

Schiehallion Central

West

North

Loyal

Design Pressure (barg) MAOP*

(barg)

323 315.7

323

323

323

323

312

314

316

322

Loyal

30

30

87.5

Transient Surge Pressure

(barg)

347.3

343.3

345.4

347.8

354.9

* This is equivalent to the maximum allowable operating pressure @ LAT of 276 barg.

Table 20 Pressure at the Water Injection Manifold

Temperature Parameters

Temperature: - Minimum

- Maximum

28 degC

60 degC

- Normal Discharge 63 degC

Shutdown



Normal Shutdown: Usually involves closing the wing valve



Process Shutdown: Wing valve closed

Start-up

The normal well start up sequence is:



Open subsurface safety valve (SCSSV)



Open water injection master valve (UMIV)



Monitor pressure indicator on the xtree



Open injection wing valve (IWV) when pressure across valve is equal.

Additional Well Start-up

To start a second or subsequent well, the sequence is:



open subsurface safety valve



open injection master valve



monitor pressure indicator on the xtree



open injection wing valve when pressure across the valve is equal.


7. FAULT FINDING

7.1 Water Injection Pumps Malfunctions

PUMP OVERHEATING / SEIZURE

Fault:

Pump operating below minimum flow

Correction:

Review pump-operating parameters with the pump vendor. Dismantle and repair unit and flow correct procedures during future operation.

HIGH BEARING TEMPERATURE

Fault:

Oil level too low or high

Correction:

Refer to Lubrication for correct level, and adjust as necessary

Fault:

Oil viscosity too high

Correction:

Use oil of recommended grade

Fault:

Excessive pump thrust

Correction:

Replace / overhaul pump cartridge

REDUCED PUMP OUTPUT FLOW

Fault:

Minimum flow line open or partially open.

Correction:

Review minimum flow circuit and make corrections to ensure proper operation.

Fault:

Impeller passages obstructed.

Correction:

Replace / overhaul pump cartridge.

Fault:

Pump internals worn on close running clearance surfaces

Correction:

Replace / overhaul pump cartridge.

VIBRATION AND NOISE

Fault:

Cavitation as air or gas comes out of entrainment at first stage impeller.

Correction:

Check pump design requirements. Make necessary changes or adjustment to system to create more pressure at pump suction.

LOSS OF DISCHARGE PRESSURE AFTER START UP

Fault:

Air pocket in suction line.

Correction:

Open all vents eliminate air from pumping.

LOSS OF DISCHARGE PRESSURE AFTER START UP

Fault:

Insufficient suction pressure causing product to vaporise in the pump.

Correction:

Check pump design requirements and proceed to make necessary changes or adjustments to system and create sufficient pressure.

NO DISCHARGE PRESSURE. FAILURE TO DELIVER LIQUID AT START

Fault:

Speed is too low – turbine or engine drives.

Correction:

Refer to the driver vendor information and take the recommended action.


7.2 Gas Turbine Malfunctions

Certain operating conditions constitute abnormal turbine engine operation.

Identification of the following malfunctions will help in determining package maintenance or repair requirements.

Engine Compressor Surge

If engine compressor surge occurs, do not wait for controls to actuate - PRESS

STOP SWITCH IMMEDIATELY. Transient conditions in fuel or air systems can cause the engine to surge as described by these sounds and conditions:



Surge in the lower speed range could be indicated by engine failure to accelerate coupled with increased exhaust temperatures and a sound of buffeting or fluttering air



Surge in the higher speed range could be indicated by a loud roar and/or popping noises plus engine failure to accelerate to rated speed.

If surge occurs, shut down the engine immediately to prevent the rapid buildup of damaging temperatures. After the engine has coasted to a stop, attempt to restart as usual. If a surge occurs a second time, contact Solar Turbines

Customer Service.

Explosive Atmosphere

Dangerously explosive accumulations of natural gas, fuel fumes, oil tank vent leakage, or solvent fumes must be avoided at all times. This is achieved by proper ventilation, elimination of leaks, and by confining the use of solvents to appropriate maintenance facilities

7.3 Control System Malfunctions

Permissive to start the Turbine is not given

Fault: Permissive not given by Turbine to Start

Correction: Check Status on TCP in LER, clear alarms & reset Control System

Fault: XV-450446 not Closed. XV-450501 not Closed. XV-850002 not Open

Correction: Check that the Status on the valves and Correct the Faults.

7.4 Gas Turbine Acoustic & Filtration Package Malfunctions

Combustion Air Intake System Differential Pressure High

Fault: Inlet blocked

Correction: Clear

Fault: PBR/HVX bags need change out. Check local pressure transmitter

Correction: Change

Fault: Object blocking face of PBR/HVX filter bags

Correction: Clear

Fault: Object blocking the face of the vane separator

Correction: Remove

Fault: Wrong type of filter bags have been fitted

Correction: Change

Fault: Pressure transmitter misreading or connections are damaged

Correction: Replace


Combustion Air Intake System Differential Pressure Low or Zero

Fault: Access door to PBR/HVX filter bags is open

Correction: Close

Fault: PBR/HVX filter bags missing or damaged

Correction: Fit or Replace

Fault: Seals on filter bags or access door not in place or damaged

Correction: Replace

Fault: Pressure transmitter not functioning. Instrument pipework damaged

Correction: Replace

Fault: Drain hoses damaged or leaking on vane separator

Correction: Clear / Replace

Fault: Interface flange joints leaking Seal

Correction: Seal

Fault: Ducting or flexible damaged or punctured

Correction: Repair.

Contamination Downstream of Intake Filter Elements

Fault: Access door to PBR/HVX filter bags if open

Correction: Clean/close

Fault: PBR/HVX filter bags missing or damaged

Correction: Replace

Fault: Wrong type of filter bag fitted

Correction: Replace

Fault: Seals on PBR/HVX filter bags or access door are damaged/leaking

Correction: Replace

Fault: Downstream duct flanges are damaged or leaking

Correction: Seal

Fault: Drain hose connections to vane separator are damaged/leaking

Correction: Clear/replace

Fault: Instrument pipe work connections are leaking

Correction: Replace

Intake Filter House Doors not Functioning Properly

Fault: Hinges binding due to improper lubrication and maintenance

Correction: Clean and lubricate

Fault: Door incorrectly adjusted

Correction: Adjust as necessary

Fault: Broken seal

Correction: Replace as necessary

Fault: Dirt around bottom seal

Correction: Clean and adjust as necessary

Gas Turbine Enclosure Doors not Functioning Properly

Fault: Hinges binding due to improper lubrication and maintenance

Correction: Clean and lubricate

Fault: Door incorrectly adjusted

Correction: Adjust as necessary

Fault: Broken seal

Correction: Replace as necessary

Fault: Dirt around bottom seal

Correction: Clean and adjust as necessary


Gas Turbine Enclosure Ventilation System Differential Pressure High

Fault: Inlet blocked

Correction: Clear

Fault: GT2 filter panel dirty

Correction: Replace

Fault: Wrong type of filters fitted

Correction: Replace

Differential Pressure Low or Zero

Fault: Fitted access cover loose

Correction: Replace

Fault: Door GT2 filter missing

Correction: Replace

Fault: Wrong type of filters fitted

Correction: Replace

Fault: Seals on filters or cover missing or damaged

Correction: Replace

Fault: Interface flanges leaking

Correction: Seal

Loss of Fan Performance

Fault: Fan stopped

Correction: Check electrical supply and connections

Fault: Filters blocked

Correction: Replace filter

Fault: Motor operating in reverse

Correction: Rewire phases of fan

Fault: Vent dampers not fully open

Correction: Reset dampers

Fault: Flexible bellows failed

Correction: Check all bellows

Fault: Enclosure doors open

Correction: Shut doors

Fan Unit Vibrating

Fault: Bearing requires lubrication

Correction: Lubricate

Fault: Loose motor fixings

Correction: Tighten or replace

Fault: Damaged fan blade

Correction: Replace fan blade

Fault: Foreign material in fan unit

Correction: Clear debris

Fault: No power to damper/ vent dampers closed

Correction: Check circuit/ open dampers

Combustion Exhaust Gases leaking from Assembly Joints

Fault: Fixing hardware loose or missing

Correction: Tighten or replace hardware as necessary

Fault: Gaskets between joints deteriorated or not working properly

Correction: Replace gaskets or if not working properly tighten

Fault: Compensator worn or deteriorated

Correction: Replace parts

Sudden Vibration or Noise

Fault: Thermal growth restricted

Correction: Check mounts and bearings for ease of movements


APPENDIX A - VALVE POSITION TABLES

CSO Car Seal Open

D/S Downstream

LC Locked Closed

LO Locked Open

U/S Upstream

Valve Position Table No.1

Refer to P&ID L-1000-GP-0043.00

Valve Tag

Number

Description

HV-441001 XXV-441040 D/S drain valve

HV-441004

HV-441005

HV-441121

HV-878031

FCV-441001 U/S drain valve

FCV-441001 D/S drain valve

V-44101 inlet calcium nitrate injection block valve

V-44101 inlet biocide injection block valve

Start-up

Position

Closed and blanked

Closed and blanked

Closed and blanked

Open

Closed and blanked

Normal

Operation

Closed and blanked

Closed and blanked

Closed and blanked

Open

Closed and blanked

HV-878032

HV-878033

V-44101 outlet biocide injection block valve

V-44101 outlet biocide injection bleed valve

HV-441112 V-44101 outlet biocide injection block valve

HV-441003 V-44101 inlet anti-foam injection

HV-441080 Z-44101 instrument air supply

HV-441020 PSV-441005 U/S block valve

HV-441021 PSV-441005 D/S block valve

HV-441023 PSV-441006 U/S block valve

HV-441022 PSV-441006 D/S block valve

HV-441024 PSV-441005/6 bypass (globe valve)

HV-441025 PSV-441005/6 bypass

Closed

Closed and blanked

Closed

Closed

Open

LO*

LO*

LC*

LC*

Closed

Closed

Closed

Closed and blanked

Closed

Closed

Open

LO*

LO*

LC*

LC*

Closed

Closed

HV-441017

HV-441019

HV-441026

HV-441100

HV-441012

Booster pumps P-43001A/B/C to V-44101

O

2

scavenger injection point

V-44101 drain to overboard

V-44101 outlet scale inhibitor injection

FCV-441019 U/S drain valve

Open

Closed

Closed

Closed

Closed and blanked

Open

Closed

Closed

Closed

Closed and blanked

HV-441013 FCV-441019 D/S drain valve

HV-441014 FCV-441019 D/S block valve

HV-441016 V-44101 outlet

Closed and blanked

Open

Closed

Closed and blanked

Open

LO

* Valves mechanically interlocked to ensure that either PSV-441005 or PSV-441006 is on line



Refer to P&ID L-1000-GP-0044.00

Valve Tag

Number

Description

HV-441066 PCV-441023 U/S block valve

HV-441065 PCV-441023 D/S block valve


HV-441061 PCV-441021 U/S block valve


HV-441070 FCV-441027 U/S block valve

HV-441068 FCV-441027 D/S block valve

HV-442001 P-44201A inlet

HV-442006 P-44201A outlet

HV-442007 P-44201B inlet

HV-442012 P-44201B outlet

HV-442024 FI-442025 U/S drain valve

HV-442021 FI-442025 D/S block valve

HV-442026 X-44201 tube side vent

HV-442027 X-44201 tube side drain

HV-442031 V-44201 vent valve

Start-up

Position

Open

Open

Open

Open

Open

Open

Open

CSO

CSO

CSO

CSO

Closed and blanked

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Closed

Open

Open

Open

Open

HV-442029 V-44201 manual vent (globe valve)

HV-442030 V-44201 manual blowdown (ball valve)

HV-442035 V-44201 outlet

HV-442039 X-44201 outlet

HV-442041 TCV-442014 block valve

HV-442040 TCV-442014 block valve


Refer to P&ID L-1000-GP-0046.01

The following valve position table covers the line-up of water injection pump P-45001A:

Valve Tag

Number

Description

HV-450100 Instrument air supply block valve

HV-450101 Air supply to 4-way block valve

HV-450135 Air supply to discharge valve

HV-450136 Air supply to minimum flow valve

HV-450137 Spare air supply valve


HV-450121 Lube oil tank T-45001A drain

HV-450104 Oil cooler X-45001A cooling medium supply

HV-450106 X-45001A cooling medium supply drain valve

Start-up

Position

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Normal

Operation

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Normal

Operation

Open

Open

Open

Open

Open

Open

Open

CSO

CSO

CSO

CSO

Closed and blanked

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Closed

Open

Open

Open

Open


Valve Tag

Number

Description

HV-450105 X-45001A cooling medium return

HV-450109 X-45001A cooling medium return line drain

HV-450139

HV-450110

HV-450111

HV-450113

HV-450114

HV-450115

HV-450116

-

HV-450123

HV-450132

HV-450144

HV-450141

HV-450142

HV-450125

HV-450126

HV-450127

HV-450128

HV-450134

HV-450133

HV-450129 FCV-450145 D/S block valve (overboard dump line)

X-45001A D/S lube oil drain valve

PDIT-450136 block valve

PDIT-450136 block valve

F-45001A vent valve

F-45001A drain valve

F-45002A vent valve

F-45002A drain valve

F-45001A/2A equalising valve

HV-450117 Lube oil line to PCV-450137

HV-450140 RO-450160 U/S block valve

HV-450118 PIT-450134 (lube oil supply) block valve

HV-450119 PT-450135 (lube oil supply) block valve

HV-450103 PIT-450117 (NDE seal pressure) block valve

HV-450102 PIT-450116 (DE seal pressure) block valve

HV-450143 Balance return line drain

HV-450122 Water inlet block valve

HV-450130 Water inlet drain valve

PIT-450141 (water inlet) block valve

HV-450124 PT-450142 (water inlet high/low trip) block valve

HV-450131 Water inlet vent valve

Discharge line vent

Discharge line vent

Discharge line drain


PIT-450143 (discharge line) block valve

PT-450144 (discharge high/low trip) block valve

FIT-450145 block valve

FIT-450145 block valve

Discharge line drain valve

Discharge line drain valve

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO

Start-up

Position

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed

Open

Open

Open

Normal

Operation

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed

Open

Open

Open

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO



Refer to P&ID L-1000-GP-0046.01

The following valve position table covers the line-up of water injection pump P-45001B.

Valve Tag

Number

Description







HV-450221 Lube oil tank T-45001B drain

HV-450204 Oil cooler X-45001B cooling medium supply

HV-450206 X-45001B cooling medium supply drain valve

HV-450205 X-45001B cooling medium return

HV-450209 X-45001B cooling medium return line drain

HV-450239 X-45001B D/S lube oil drain valve

HV-450210 PDIT-450236 block valve


HV-450213 F-45001B vent valve

HV-450214 F-45001B drain valve

HV-450215 F-45002B vent valve

HV-450216 F-45002B drain valve

F-45001B/2B equalising valve










HV-450223 PIT-450241 (water inlet) block valve

HV-450224 PT-450242 (water inlet high/low trip) block valve

HV-450231 Water inlet vent valve

HV-450232 Discharge line vent

Start-up

Position

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed

Open

Open

Open

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed

Normal

Operation

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed

Open

Open

Open

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed


Valve Tag

Number

HV-450244 Discharge line vent

Description

HV-450241 Discharge line drain

HV-450242 Discharge line drain

HV-450225 PIT-450243 (discharge line) block valve

HV-450226 PT-450244 (discharge high/low trip) block valve

HV-450227 FIT-450245 block valve


HV-450234 Discharge line drain valve


Start-up

Position

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO

Normal

Operation

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO HV-450229 FCV-450245 D/S block valve (overboard dump line)


Refer to P&ID L-1000-GP-0046.01

The following valve position table covers the line-up of water injection pump P-45001C.

Valve Tag

Number

Description







HV-450321 Lube oil tank T-45001C drain

HV-450304 Oil cooler X-45001C cooling medium supply

HV-450306 X-45001C cooling medium supply drain valve

HV-450305 X-45001C cooling medium return

HV-450309 X-45001C cooling medium return line drain

HV-450339 X-45001C D/S lube oil drain valve



HV-450313 F-45001C vent valve

HV-450314 F-45001C drain valve

HV-450315 F-45002C vent valve

HV-450316 F-45002C drain valve

F-45001C/2C equalising valve



Start-up

Position

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed

Normal

Operation

Open

Open

Open

Open

Closed

Closed

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Closed and blanked

Open

Open

Closed and blanked

Closed and blanked

Closed and blanked

Closed and blanked

Closed

Open

Closed


Valve Tag

Number

Description








HV-450323

HV-450324

HV-450331

HV-450332

HV-450344

HV-450341

HV-450342

HV-450325

HV-450326

PIT-450341 (water inlet) block valve

PT-450342 (water inlet high/low trip) block valve

Water inlet vent valve

Discharge line vent

Discharge line vent



PIT-450343 (discharge line) block valve

PT-450344 (discharge high/low trip) block valve





Start-up

Position

Open

Open

Open

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO

Normal

Operation

Open

Open

Open

Open

Closed

LO

Closed and blanked

Open

Open

Closed and blanked

Closed

Closed and blanked

Closed

Closed and blanked

Open

Open

Open

Open

Closed

Closed and blanked

LO HV-450329 FCV450345 D/S block valve (o’board dump line)


Refer to P&ID L-1000-GP-0046.02

Valve Tag

Number

Description

HV-450001 Injection water to V-43001 drain valve

HV-450002 Injection water to V-43001

HV-450003 F-43001A/B to P-45001A/B/C

HV-450005 Water make-up to 2 nd stage separator V-21201

HV-450012 P-45001A discharge to AT-450020

HV-450007 P-45001A discharge to AT-450020 low point drain

HV-450006 P-45001B discharge to AT-450020

HV-450013 P-45001B discharge to AT-450020 low point drain

HV-450014 P-45001C discharge to AT-450020

HV-450008 P-45001C discharge to AT-450020 low point drain

HV-450009 P-45001A/B/C discharge AT-450020

HV-450010 P-45001A/B/C discharge AT-450020 low point drain

Start-up

Position

Closed and blanked

Closed

Open

Closed

Open

Closed & blanked

Open

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Normal

Shutdown

Closed and blanked

Closed

Open

Closed

Open

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked

Open

Closed and blanked



SUBSEA VALVE LINE-UP (sample summary – not complete)

Position Signature/Date Tag No.

CW11/N

SCSSV-105931N

LIMV-105921N

UIMV-105933N

AMV-105935N

IWV-105934N

XOVT-105937N

CHI-105926N

Closed

Open

Closed

Closed

Closed

Closed

Set at a value of 2.3

(i.e. 23% or 1.7 turns)

CW12/P

SCSSV-105931P

LIMV-105921P

UIMV-105933P

AMV-105935P

IWV-105934P

XOVT-105937P

CHI-105926P

Closed

Open

Closed

Closed

Closed

Closed

Set at a value of 2.3

(i.e. 23% or 1.7 turns)

Central WI Manifold

ROVV-180921

ROVV-180922

ROVV-180923

ROVV-180924

Open

Open

Closed

Closed


Schiehallion FPSO 4

th

Water Injection Pump

Gas Turbine Exhaust Dispersion Study

Copy of Report No: S/UTG/ /02

(refer to parent document for up-to-date information)

REPORT NO: S/UTG/ /02

SECURITY CLASSIFICATION: UNCLASSIFIED

ISSUE DATE: 11/04/20

MAIN TITLE : Schiehallion FPSO

SUB TITLE : 4th Gas Turbine Exhaust Dispersion Study

CLIENT:

PRINCIPAL RECIPIENT:

BP Exploration - Schiehallion

COMMISSIONED BY:

ISSUING DEPARTMENT/DIVISIONS: UTG

PREPARED BY: AUTHORISED FOR ISSUE BY:

______________

Chris Savvides

________________

Vincent Tam

ACKNOWLEDGEMENT RECORD PAGE: Yes

ABSTRACT :

This report describes the results of the study for the dispersion of hot exhaust gas from the proposed

Water Injection 4 th Gas Turbine, on the Schiehallion FPSO. The study consisted of the following:

Assessment of the turbine exhaust temperature distribution on helicopter and crane operations for two turbine locations and various exhaust orientations

Quantify the temperature and air quality (NO

2,

and CO concentrations) for the chosen location and configuration and assess impact on Helideck, crane and personnel at different locations on the FPSO where they could be normally present.

The results showed that with the current Gas Turbine location, forward of the Crane pedestal at frame

40, with the exhaust discharging at an elevation of 55m and pointing forward, there should be minimal impact on the Helideck, Crane operations, or to air quality.

KEYWORDS : Turbine Exhaust, Dispersion

DISTRIBUTION: End of the Report

FOR EXTERNAL CLIENT LISTING: No

UTG JOB NO: UTG:

Original report held at Britannia Data Management (BDM), 628 Western Avenue, Park Royal, London, W3


SUMMARY

This report describes the results of the study for the dispersion of hot exhaust gas from the proposed Water Injection 4 th Gas Turbine, on the Schiehallion FPSO. The study consisted of the following:

Assessment of the turbine exhaust temperature distribution on helicopter and crane operations for two turbine locations and various exhaust orientations

Quantify the temperature and air quality (Nitrogen dioxide - NO

2

and Carbon Monoxide – CO, see

Footnotes 1 & 2 ) concentrations for the chosen exhaust location and configuration and assess impact on Helideck, crane and personnel at different locations on the FPSO where they could be normally present.

The results showed that with the current Gas Turbine location, forward of the Crane pedestal at frame 40, with the exhaust discharging at an elevation of 55m and pointing forward, there should be minimal impact on the Helideck, Crane operations or to air quality.

INTRODUCTION

The Schiehallion FPSO has been operating off the west of Shetland since 1998. Due to the requirement of water injection, a 4 th Gas Turbine will need to be installed to provide the extra power.

As part of safety requirements, the hot plume characteristics from a gas turbine need to be assessed and quantify so as not impair Helideck, crane or other operations. There is also a requirement to demonstrate that the air quality meets UK regulations. This report summarises the findings of the computational study to find the best location and orientation of the 4 th Turbine

Exhaust so that the effects of the hot exhaust plume would have a MINIMUM impact on the

Helideck, crane operations and at other manned areas.

The fluid flow software FLACS has been used for the plume dispersion calculations. BP has extensively used FLACS for a lot of projects involving dispersion and gas accumulation calculations. It has been validated for a number of large-scale experimental data.

1 Sulphur Dioxide is not considered because Sulphur is not present in the Schiehallion fuel gas supply.

2 Particulate matter is not considered, as the level present in the Taurus 70 exhaust gas is very low

(to be quantified by Solar).


Objectives

The main objectives of this analysis were to:

Assess the impact of the exhaust plume of the proposed 4 th Gas Turbine on Helideck and

Crane operations. Identify the location and orientation of the turbine exhaust that would have minimum impact on Schiehallion operations

Quantify the availability of the Helideck and Crane based on the wind conditions and temperatures distribution and also assesses the effect of the exhaust gases on the manned areas for the different locations and exhaust orientations. For Helideck operations, it is a requirement that the isothermal line at 20m directly above the Helideck is less than +2 degrees above the ambient temperature (Footnote 3 )

Quantify the air quality (NO

2 and CO) levels in manned areas for the final Gas Turbine location.

DESCRIPTION TURBINE EXHAUST DISPERSION MODEL

The study of the exhaust dispersion using Computational Fluid Dynamics requires an accurate representation of all the major structure and equipment, the wind and exhaust parameters. An accurate computer model of the Schiehallion FPSO Installation was already available (used previously for explosion hazards). This was constructed based on the as build PDMS CAD model

[1, 2]. Details of the Gas Turbine and exhaust were incorporated into the model.

Gas Turbine Exhaust Conditions

The new water injection Gas Turbine is a Taurus 70 from Solar Turbines Incorporated. Exhaust flow rates, temperatures and gas analysis are for full load output of 6700 -7800 kW, depending on ambient temperature.

3 The Civil Aviation Authority (CAA) paper 99004 Section 4.1.4 includes a sentence stating “CAP

437 requires that notification to operators be given if temperatures in excess of 2



C above ambient are liable to exist above the Helideck. Section 4.2.3 also states “Minimisation of the impact of hot exhausts (see Section 4.1.4) has generally been regarded as keeping the Helideck free of excess temperature, at least to a reasonable height (say greater than 20m above deck level). Ideally, in conjunction with flight operations planning, approach and take-off flight paths should also be considered.


The following Turbine Data [3] has been used in the simulations:

Load Case

1

2

Turbine Load

Exhaust Flow

Rate kg/s

100% at 5

100% at 23 o o

C

C

27.7

24.9

Exhaust Gas

Temperature, o

C

488

506

NO

2

Concentration mg/m 3

74.03

72.78

CO

Concentration mg/m 3

53.65

52.69

Table 1: Turbine Exhaust Conditions (see Footnote 4 )

During the course of this study 3 different exhaust diameters were used (1000, 900 and 800mm).

For the final results the exhaust diameter used is 900 mm

The exhaust gas is specified as a non-reacting mixture of gas and air with a molecular weight of

28.

The CFD analyses performed are 3-dimensional, steady state, turbulent simulations of the flow of a non-reacting mixture of ambient air and hot gases. Buoyancy forces due to the gas/air mixture density and temperature variations are incorporated directly.

Gas Turbine Location and Exhaust Orientation

Two locations on the FPSO were considered for the Gas Turbine. Both locations were on the

Starboard side

The lay-down area on Pallet 8 (Frame 35) just forward of the Blast Wall separating the

Living Quarters from the Process areas.

The lay-down area on Pallet 7 (Frame 40) forward of the aft Crane Pedestal

Several different orientations of the turbine exhaust have been tried for each of the two locations namely:

Discharging vertically up

Discharging to starboard

Discharging 45 degrees forward-starboard

Discharging forward, at 0, 10, 20 and 45 degrees to the horizontal

4 The NO

2

exhaust analysis figures relate to Solonox Combustion. For this analysis it is assumed that all oxides of nitrogen are considered to be nitrogen dioxide (NO

2

). This is a worst case assumption, which in practice means that calculated NO

2 levels would be slightly higher than actual levels. This will (together with other factors discussed later in this document) provide assurance that air quality will meet regulatory requirements.


Wind Conditions

For the preliminary investigations to evaluate the location and orientation of the turbine exhaust, only winds at 6 m/s from Forward and Starboard (0-45 degrees) were considered as these would have a direct impact on the Helideck operability, which was the primary reason for this evaluation.

For the final assessment, results were obtained for all wind directions at 6 and 12 m/s so that the impact of the exhaust temperatures and NO

2

levels on the Crane boom, Crane cabin and other manned areas is assessed. Table 2 lists all the weather conditions and the probability of occurrence for the Schiehallion FPSO [4].

0 - 2.5 2.5 - 7.5

Wind Speed, m/s

7.5 - 12.5 12.5 - 17.5 >17.5 % Probability

Wind Direction relative to vessel

Angle from Forward

10-30

40-60

70-90

100-120

130-150

160-180

190-210

220-240

250-270

280-300

310-330

340-360

% Probability

0.00%

0.00%

0.71%

0.71%

0.83%

1.18%

7.8%

1.18%

0.83%

1.18%

0.59%

0.35%

0.24%

1.65%

0.35%

1.89%

2.60%

3.90%

8.97%

39.6%

8.26%

5.90%

2.13%

2.24%

0.83%

0.83%

10.27%

5.67%

1.42%

0.47%

0.12%

0.35%

0.12%

0.00%

0.71%

1.42%

4.13%

9.45%

34.1%

0.00%

0.00%

0.00%

0.24%

1.42%

5.55%

16.3%

7.56%

1.18%

0.24%

0.12%

0.00%

0.00%

0.00%

0.00%

0.00%

0.00%

0.12%

0.47%

2.2%

1.30%

0.35%

0.00%

0.00%

0.00%

0.00%

1.8%

0.4%

3.3%

5.0%

10.4%

25.6%

100.0%

28.6%

13.9%

5.0%

3.4%

1.3%

1.4%

Table 2: Wind Frequency (Port 0-180, Starboard 180-360)

Assessment Standards

For Helideck operations, it is a requirement that the isothermal line at 18m directly above the

Helideck is less than +2 degrees above the ambient temperature

The temperature of the Crane boom (wire rope & lubricant, warning lights, load sensors) should not exceed 85 o C [5]

The UK air quality regulations objectives (NO

2

and CO only) are defined in the Environment

Agency (EA) Guidance Notes [6] and are shown in Table 3 below:


Pollutant

NO

2

NO

2

CO

Reference period

Hourly mean

Annual mean

8 hour mean

Limit Value

200

 g/m 3

40

 g/m 3

11.6 mg/m 3

Limit Value to be met by

31 Dec 2005

31 Dec 2003

Table 3: Environmental Quality Standards – Protection of Human health [table 1 Ref 6]

PRELIMINARY INVESTIGATIONS

Initially the 4 th Gas Turbine was to be located on the lay-down area, Pallet 8 (Frame 35), just forward of the Blast Wall. The distance of the discharging exhaust to the centre of the Helideck would have been approximately 40 metres. The elevation of the exhaust was restricted to 47m, as a higher exhaust would have interfered with Crane operations.

Preliminary investigations, examining different orientations of the exhaust, have shown that due to its proximity to the Helideck and also the restriction on the elevation of the discharge, the temperatures above the Helideck (hovering height) would be greater than +2 degrees C, which would restrict safe helicopter operations for winds from the Forward to 20 degrees Starboard.

From the wind frequency table 2, this would have made the Helideck unavailable for almost 30% of the time.

This factor was one of a number of reasons why the Pallet 8 location was changed to the Pallet 7 location.

FINAL TURBINE LOCATION - RESULTS

The second location for the Gas Turbine, the lay-down area on Pallet 7 (Frame 40) forward of the aft Crane Pedestal was then examined. This location is some 60 metres from the Helideck. From the results of the preliminary investigations for the first location, it was decided that the exhaust discharge should be forward and at an elevation at least above the Crane boom. The forward discharge allows the exhaust gases extra distance away from the Helideck, while the extra elevation, firstly eliminates any problems with hot gases on the Crane boom and cabin and secondly the exhaust is not in the lee of recirculation areas.


The final location and orientation of the turbine exhaust is:

Location

Orientation

Diameter

E=115m N=375m Elevation=55m

Discharging Forward at 10 degrees up from the horizontal

900mm

For this location and orientation a full set of results is presented for the 2 cases listed in Table 1.

All wind directions and wind speeds of 0, 6 and 12 are presented. These represent about 85% of all weather conditions. The other 15% are for higher wind speeds. One result for a 20 m/s wind from the Forward direction gave similar results to the 12 m/s case.

Load Case 1

– Results

For this load case, the gas Turbine is operating at 100%, with an exhaust flow rate of 27.7 kg/s and a temperature of 488 o C. The results are presented in Table 4. The temperatures are given in degrees Celsius above the ambient temperature. The NO

2

concentrations are given in

 g/m 3 .

Living Quarters refers to the area behind the Blast Wall and Process deck, areas forward of the

Blast Wall at elevations between 32 and 50m

The results show the following:



Helideck operations might be affected by winds from 10 degrees from

Starboard at 12 m/s or higher (8-10% of the time). The temperature is only 3 degrees above ambient just slightly above the requirements.



The maximum temperature at the crane boom would be less than 20 degrees for all weather conditions. This is well within the requirements

There will be concentrations higher than 40

 g/m 3 for the forward, and up to 10 degrees from

Starboard. The concentration increases almost linearly for higher wind speed. Wind directly from the aft of the FPSO will produce high levels of NO

2

concentration at the Turret area and the forward Crane cabin (300 and 240

 g/m 3 respectively). The frequency of the wind from the aft is very low, of the order of 1%.


Simulation

Number

Wind

Direction relative to

FPSO heading

Wind

Speed m/s

HELIDECK

NO

2

Temp

Deg C

CRANE

BOOM

Temp

Deg C

Crane Cabin

Living

Quarters

Process

Deck

NO

2

Concentration

060000 No Wind

060600

061200

062000

360600

260605

261205

260610

261210

260622

261222

260645

261245

260667

261267

260690

261290

260613

160622

161222

160645

161245

160667

161267

160680

161280

160690

161290

160600

161200

161213

FWD

FWD

FWD

BWD

STB 5

STB 5

STB 10

STB 10

STB 22.5

STB 22.5

STB 45

STB 45

STB 67.5

STB 67.5

STB 90

STB 90

STB 135

PORT 22.5

PORT 22.5

PORT 45

PORT 45

PORT 67.5

PORT 67.5

PORT 80

PORT 80

PORT 90

PORT 90

PORT 100

PORT 100

PORT 135

6

12

20

6

12

6

12

6

6

12

6

6

6

12

6

12

6

12

6

12

6

12

12

6

12

6

12

6

12

6

40

100

120

40

80

+3

40

120

160

240

Fwd crane

+5

+5

+3

Fwd crane

+15

+15

+5

+5

+8

+10

+17

60

80

120

80

Table 4: Load Case 1 - Temperature and NO

2

Concentrations on the Helideck, Crane and other areas

60

120

300

Turret

40


Load Case 2

– Result

For this load case, the gas Turbine is operating at 100%, with an exhaust flow rate of 24.9 kg/s and a temperature of 506 o C. The results are presented in Table 5.

Simulation

Number

Wind

Direction relative to

FPSO heading

Wind

Speed m/s

HELIDECK

NO

2

Temp

Deg C

CRANE

BOOM

Temp

Deg C

Crane Cabin

Living

Quarters

Process

Deck

NO

2

Concentration

070000 No Wind

070600

071200

270690

271290

170622

171222

170645

171245

170667

171267

170690

171290

270605

271205

270610

271210

270622

271222

270645

271245

270667

271267

FWD

FWD

STB 5

STB 5

STB 10

STB 10

STB 22.5

STB 22.5

STB 45

STB 45

STB 67.5

STB 67.5

STB 90

STB 90

PORT 22.5

PORT 22.5

PORT 45

PORT 45

PORT 67.5

PORT 67.5

PORT 90

PORT 90

6

12

6

12

6

12

6

12

6

12

6

12

6

12

6

12

6

12

6

12

6

12 +4

40

100

40

80

Table 5: Load Case 2 - Temperature and NO

2

Concentrations on the Helideck, Crane and other areas

+5

+15

+15

+5

40

120

60

80

80

60


As can be seen from the table, all the results are nearly identical to the previous load case.

Conclusions are similar to the load case 1.

AIR QUALITY DISCUSSION

In addition to the UK air quality regulations’ objectives, EA Guidance Note H1 [6] also tabulates long term and short term Environmental Assessment Levels (EALs) for a wide range of substances. The short term and long term EALs for NO

2

and CO are compared with typical exhaust gas quantities in Table 6 below. An indication of the required dilution factors for the exhaust gases (mixing with fresh air) for each contaminant is noted where contamination levels reach an acceptable level.

Substance Contaminant Acceptable level of Contaminant Dilution Factor Required to level at exhaust gas outlet

74,031

 g/m 3

(Short-term and Long-term EALs) reach acceptable air quality

NO

2

CO

74,031

 g/m 3

53,650

 g/m 3

53,650

 g/m 3

40

 g/m 3

Long-term EAL (Annual mean)

200

 g/m 3

Short-term EAL (Hourly mean)

350

 g/m 3

Long-term EAL (Annual mean)

10,000

 g/m 3

Short-term EAL (Hourly mean)

1851

370

5.365

153.3

Table 6: Dilution Factors required to reduce exhaust gas contamination to an acceptable level.

Observation of the results shown in Table 6 above shows that a greater dilution of exhaust gases

(with fresh air) is required to achieve acceptable NO

2

levels than for CO. Thus, it is valid to model the NO

2

levels only and infer that acceptable levels of CO will be achieved if acceptable levels of

NO

2

are reached. The Environmental Assessment Levels (EALs) for NO

2

and CO shown in Table

6 above are lower than the Occupational Exposure Limits (OELs) for NO

2

and CO set by the

Health & Safety Executive HSE in their document EH40/2002 [7]. A comparison of the two limits is shown in Table 7 below.

3

4

Row

1

2

Limit Description

HSE Defined OEL

Long-term exposure limit (8-hour TWA ref period

Environment Agency Defined EAL

Long Term

5

Limit in Row 1 above divided by Limit in row 2 above

HSE Defined OEL

Short-term exposure limit (15-minute ref period)

Short Term

6 Limit in Row 4 above divided by Limit in row 5 above

NO

2

5,700

 g/m 3

40

 g/m 3

Annual Mean

142.5

9,600

 g/m 3

200

 g/m 3

Hourly Mean

48.0

CO

35,000

 g/m 3

350

 g/m 3

Annual Mean

100.0

232,000

 g/m 3

10,000

 g/m 3

Annual Mean

23.2

Table 7: Comparison of EAL and OEL figures for NO

2

and CO.


The reasons for the differences between EALs and the OELs limits is explained in a section titled

“Derivation of Environmental Assessment levels for Air” in Appendix D of the Environment Agency

Guidance Note H1 [6]. A copy of this section is included in Appendix 1 of this document. This shows how a factor of safety is applied between the HSE defined OEL or maximum exposure limit

(MEL) if there is a specific concern about the pollutant (e.g. a carcinogen) and the environmental assessment level (EAL). The long and short term EALs for NO

2

were based upon the Expert

Panel on Air Quality Standards (EPAQS) guideline values. Also, the short term EAL for CO was based upon the EC Daughter Directive 99/30/EC. However, for these exceptions the philosophy of a large safety factor between OELs or MELs and EALs still applies.

An exhaust emissions study has already been carried out on the Schiehallion FPSO in May 2000 by Lindsay Ross (BP Occupational Health). This compared site readings with HSE OELs, rather than Environment Agency EALs objectives. The measurement instrument used by Lindsay to measure NO

2

levels during this survey was not capable of reading NO

2

levels less than 0.5 ppm

(1900

 g/m 3 ). It is not possible, therefore, to determine a precise impact of the exhaust from the two LM6000 gas turbines at different locations on the FPSO. Only one reading taken by Lindsay exceeded the 0.5 ppm measurement threshold value during his survey, but that reading was taken directly at the point of emission from a fire pump diesel engine. The main conclusion of the survey was that all emission measurements were very low and well within the respective OELs with the majority being below the limit of detection of the equipment used.

Use of the EA EAL values rather than HSE OELs does provide a level of assurance that air quality on the Schiehallion FPSO will be much better than required to meet occupational health requirements. The EA Guidance Note H1 [6] describes how operators can show that their proposals represent the Best Available Techniques (BAT) to prevent and minimise pollution from an installation. Use of the modelling approach for the 4 th WI pump’s GT exhaust can be demonstrated to meet this requirement. There are arguments for and against use of safety factors implicit in the use of EALs, as follows:


FOR USE OF SAFETY FACTORS:

Safety factor will cover impact of any errors caused by use of CFD model, e.g. the model does not take into account the impact of the FPSO motion and the tendency for locations on the vessel to move into areas of higher NO

2

levels than modelled.

CFD modelling does not take into account the emissions generated by exhaust from the existing two LM6000 gas turbines on Schiehallion. Use of EALs with target emission levels an order of magnitude below OELs provides assurance that there will be little, if any impact on occupational health issues for personnel on the FPSO.

A review of the NO

2

contour plots does show that for some combinations of wind speed and direction (20 metres per second with forward wind - 0 degrees), that NO

2

levels near the accommodation air inlets may reach a level of 60

 g/m 3, which is above the

Long Term EAL for NO

2

. This level is considered acceptable, because the frequency of its occurrence is low (< 1% wind speed exceeding 17.5 m/s from wind directions

350º, 0º and 10º was observed in 9 months data collected between 1 st February 2000 and 17 th October 2000. Similarly, for an aft wind, NO

2

levels of up to 300

 g/m 3 were observed. Again the frequency of this wind direction is very low (< 0.5% occurrence during the period 1 st February 2000 and 17 th October 2000). Any relaxation of the approach used could result in unacceptable NO

2 levels in the accommodation and/or at the turret.

AGAINST USE OF SAFETY FACTORS:

Use of a large safety factor increases the complexity and cost of the exhaust arrangement. It might be possible to reduce the safety factor because there is: 1) no local population living close to the installation, other than off duty hours in the accommodation; 2) there will be recovery periods between exposures; and 3) personnel on the FPSO will not include sensitive individuals, e.g. children, the elderly or those with diseases such as asthma.

On balance, the arguments are in favour of retaining the use of the large safety factors.


7. GAS EXPLOSION HAZARDS

This area is currently free of pressurized hydrocarbon gases. The introduction of the Gas Turbine

GT would change that. As there is only one pipe for the gas into the Turbine, it is possible to control the consequence of a potential gas explosion to an acceptable level by controlling the connection locations and the pipe routing.

The dimensioning explosion based pallet filled condition gave an overpressure of over 4 bar if the process deck is grated (i.e. when gas is allowed to accumulate above between the tank top and process deck). If this can be avoided then maximum overpressure would be reduced to about 1 bar. Further, if the volume of flammable gas can be reduced, maximum explosion overpressure would be further lowered. Our view is that if the recommendations below are implemented, then the maximum overpressure at the blast wall would be l below the blast wall capacity of 0.5 bar, and no further explosion analysis is required.

We reviewed the layout of the fuel gas line. The good points of the layout are: The fuel gas line is routed high, and high integrity joints are used to connect pipe sections which appears to have been kept to a minimum.

It is recommended to route the fuel gas line input into the skid on the outboard side (rather than the inboard side). This will allow any potential leaks to be dispersed away from the vessel. Our understanding from our discussion with the Schiehallion project is that in the unlikely event of the connection failing, then the release direction would be along the length of the pipe, i.e. the released gas from the fuel gas line would impact on the plating on the side of the Turbine skid and disperse mainly outboard, and the fuel gas from the skid would be directed outboard and again disperse outside the vessel.

It is also recommended that:

Plating the Gas Turbine skid around the fuel gas entry into the skid or ensure that a gas leak within the Gas Turbine skid cannot be dispersed below the process deck (if the process deck cannot be plated). This can be done using a flange guard

Ensure there is adequate explosion venting in the Gas Turbine module enclosure. We recommend that one of the panels of the Turbine should fail quickly under explosion load; the starboard panel (facing outboard) should fail, while the top panel should remain. This panel should be restrained (say by a chain) to avoid missile hazards. The design should ensure the integrity of the fuel gas line is not affected.


CONCLUSIONS AND RECOMMENDATIONS



The proposed location of the 4 th Gas Turbine, forward of the Crane pedestal at frame 40, with the exhaust discharging at an elevation of 55m and pointing forward at an angle of 10 degrees above horizontal, should have minimal impact on either the Helideck or Crane operations



There should be no additional explosion hazard, provided the gas from the fuel line is dispersed above the process deck



The air quality will remain within acceptable health guidelines (see following discussion).

REFERENCES



Schiehallion FPSO Final Design, Gas Accumulation and Explosion Studies,

UTG Sunbury Report SPR/OIT/012/97, December 1997



Schiehallion FPSO Updated Explosion Analysis Study, UTG Sunbury Report

S/UTG/155/00, December 2000



Weather Data, supplied by Schiehallion Project



Gas Turbine Data, supplied by Solar Turbines Inc



Crane boom limitations, supplied by Sparrows.



Environment Agency Guidance Note H1. Integrated Pollution Prevention and

Control (IPPC) – Environmental Assessment and Appraisal of BAT.



EH40/2002. Occupational Exposure Limits 2002.

AIR QUALITY ENVIRONMENTAL BENCHMARKS

IPPC Version 3.1, July 2002 89

Derivation of Environmental Assessment levels for Air

For many substances which are released to air EQSs have not been defined. Where the necessary criteria are absent then the Regulators have adopted interim values known as

Environmental Assessment Levels (EALs). The EAL is the concentration of a substance which in a particular environmental medium the Regulators regard as a comparator value to enable a comparison to be made between the environmental effects of different substances in that medium and between environmental effects in different media and to enable the summation of those effects. Ideally EALs to fulfil this objective would be defined for each pollutant:



based on the sensitivity of particular habitats or receptors (in particular three main types of receptor should be considered, protection of human health, protection of natural ecosystems and protection of specific sensitive receptors, e.g. materials, commercial activities requiring a particular environmental quality;




be produced according to a standardised protocol to ensure that they are consistent, reproducible and readily understood;



provide similar measure of protection for different receptors both within and between media;



take account of habitat specific environmental factors such as pH, nutrient status, bioaccumulation, transfer and transformation processes where necessary.

A suite of EALs derived in this consistent manner is not currently available, therefore, interim values based on published information have been adopted. The list below shows the sources from which information has been obtained. For consistency, risk based values proposed by the World Health Organisation or given in the IRIS database have been excluded.

Currently some 460 substances or groups of substances are authorised by the

Regulators for release to the environment and many of these may be released to air.

However, established environmental criteria (other than a limited number of EQSs) are available for only a small fraction of this number. For example, in the case of releases to air, EPAQS have produced guideline values for only six substances (Ozone, Benzene,

Carbon Monoxide, Sulphur Dioxide, Particles and 1,3 Butadiene, nitrogen dioxide, PAHs and lead) and the WHO Air Quality Guidelines contain values for 27 substances.

Information sources :



Expert Panel on Air Quality Standards (EPAQS)



EC Air Quality Directives - limit values and guidelines



World Health Organisation Air Quality Guidelines for Europe (1987, 1995)



Other International Organisations (e.g. United Nations Economic Commission for Europe)



Other National Organisations (e.g. US IRIS data base)



Health and Safety occupational exposure limits.



Expert judgement

Ideally, EALs for those substances where there are no existing criteria would be derived direct from toxicological data on the effects of the pollutant on a particular receptor.

However, an assessment of this type would be a very substantial undertaking which could only be considered over an extended timescale. One approach to overcoming this problem is to make use of occupational exposure limits which provide an assessment for a specific receptor (i.e. adult human workforce) of the toxicological effects of a pollutant.

These values might then be progressively revised as further information and resources allow. Indeed a similar approach to this was followed by the then Factory Inspectorate in

1968 when a large number of occupational standards were adopted from the American

Conference of Governmental Industrial Hygienists (HMSO 1968) which has since been progressively revised by the Health and Safety Executive on the basis of new information and UK experience.
