PETROFED
(6th Programme on Oil & Gas transportation through Pipeline)
IIPM GURGAON
8th- -10th July , 2009
Intricacies
of
Design of a Gas Pipeline
&
Main Equipment , System in Gas Pipeline
by
Rahul Gautam
Chief Manager (Pipeline)
Project Development
GAIL(INDIA) LTD
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Contents
 Typical Pipeline System
 Typical Input Parameter for designing
 Design Basis
 Modeling & Simulation
 Optimization
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Typical Pipeline System
Pipeline Types
Gas
Source
Gas
Gathering
System
Gas
Treatment
Gas
Transmission
Gas
Distribution
Typical Gas Transmission & Distribution
DT
SV
DT: Dispatch Terminal
SV: Sectionalizing Valve
IP : Intermediate Pigging Station
RT : Receiving Terminal
IP
RT
RT
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Typical Pipeline System
x- ings
RAIL/ROAD/RIVER
GAS FIELD
RECEIVING
TERMINAL /
DELIVERY
TERMINAL
CS
GGS &
GT CTP
IP
SV
GAS
RECEIVING
STATION
SV: Sectionalizing Valve
IP : Intermediate Pigging Station
CS: Compressor Station
RT : Receiving Terminal
GGS : Gas Gathering System
GT: Gas Treatment
Typical Schematic for Pipeline System
Typical Pipeline System
A typical gas pipeline system comprise of the following
• Gas Receiving Station
- Place where pipeline receives the gas.
• Sectionalizing Valve Station
- To carry out routine maintenance or emergency
maintenance of pipeline venting of gas is to be restricted.
• Intermediate Pigging Station
- To ensure continuous gas flow through pipeline, regular
and periodical cleaning of pipeline is required.
- The pigging is carried out various kind of Pig e.g. Scrapper Pig,
Gauzing Pig, Foam Pig etc.
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Typical Pipeline System
TYPICAL SV STATION
P
G
Utility Connection – 2”
T
G
AV
P
G
T
G
By pass Line
MANIFOLD FOR PG
/TG
Utility Connection – 2”
MAINLINE
Typical Pipeline System
TYPICAL INTERMEDIATE PIGGING STATION From OriginatingStn
To Terminal
Stn
To Utilities
PRS
AV
AV
IJ
IJ
MOV
MOV
FLOW
TEE
RECEIVER
LAUNCHER
FLOW
TEE
BALL
VALVE
TS
V
GLOBE
VALVE
GATE
VALVE
Blow
Down
R-LNG FLOW
DIRECTION
TEG-THERMO
ELECTRIC
GENERATOR(Utilities)
Typical Pipeline System
• Compression System
- To economize the flow through pipeline
- Located enroute of the pipeline to boost the gas pressure
- Reciprocating compressor verse Centrifugal compressor
- Reciprocating compressor : up to gas volume of 200000 SCM/Hr
higher compression ration ( up to 10)
- Centrifugal compressor : higher volume flow
Compression ratio 1.5 to 2.0
Compressor installation like a process
plant requiring all kind of utilities
(Power, Water, Air, Fuel , Fire Fighting
and Control Room System)
• Receiving Terminal
- For supplying gas to various customers : designed to handle the
required flow for single
and multiple users.
- The terminal contain filters, pressure regulator, heater, metering
device, online gas chromatograph, flow computer and odorizing unit
(if required)
Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
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Contd.…
Typical Pipeline System
CS
Off take
of Gas
Gas
Supply
Pressure
CS
CS
CS
CS
Delivery of gas
TRANSPORTATION OF GAS WITH COMPRESSOR STATIONS
(TYPICAL)
Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
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Contd.…
Typical Pipeline System
Scrubber
Filters
P R Unit
PCVSDV-1
1
Metering Unit
Custody T/P
Meter-1
Flow computer-1
15 Mts
Gas Chromatograph
SDV-2PCV-2
By-Pass
Meter-2
Flow computer-2
40 Meter
Schematic (Typical ) for Receiving Terminal at Customer site
Not to Scale
Typical Input Parameters
 Type of Natural Gas
- Associated Gas
- Non Associated Gas / Free Gas
- Dry Natural Gas
- Wet Natural Gas
- Sour Natural Gas
 Gas Composition
 Gas Supply Pressure and Temperature
 Gas Volume ( To be Transported) and off-Take of gas enroute
pipeline ( if any)
 Route / Terrain
 Delivery Point
 Gas volume at delivery point
 Required Pressure and Temperature at Delivery Point
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Design Basis
 Pipeline System
Starting Point
- Supply Gas Pressure (Kg/Cm2g)
- Supply Gas Temperature (deg. C)
- Gas Volume
- Gas Quality and Gas Composition
Route /Terrain
- Class location
- x-ings ( NH/SH/RAIL/ROAD/RIVER/MAJOR RIVER)
Delivery Point
- Delivery Gas Pressure (Kg/Cm2g)
- Delivery Gas Temperature (deg. C)
- Gas Volume
- Gas Quality and Gas Composition
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Design Basis
Linepipe
- Design Pressure
- Wall Thickness
- Roughness with internal coating and without internal coating
- Gas Composition
- Soil temperature
- Elevation
- Efficiency
- Flow
- Configuration
-Velocity in pipe
Metering
- Supply Pressure and temperature
- Flow
- Gas Quality and Gas Composition
- Type of meter (Orifice / Turbine Meter / USM)
- Configuration
- Pressure Loss
- Accuracy
- Rangeability
Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
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Contd.…
Design Basis
Compressor Station
- Gas arrival pressure and Temperature
- Compressor Ratio
- Discharge Pressure and Temperature of Gas
- Flow
- Gas Quality and Gas Composition
- Compression efficiency
- Compression spacing
- Compressibility
- Configuration
- Compression Power
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Pipeline modeling constitutes a Graphical Representation of the pipeline system
involving receiving stations Sectionalizing Valve Station, Intermediate Pigging
Station, Compressor / Pump Station and Receiving Terminal.
- Pipeline design (optimal Line pipe size, compressor requirement, loop line and
other equipments location including SCADA & Telemetry System)
- Pipeline performance (Throughput optimization)
- Tracking gas composition
- Minimize fuel consumption
- Pipeline systems operation
- Create Emergency Plan
- Leak Detection Module
- Alarms Generation
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
End Point
Dedicated Pipeline
Spurline
Trunk Line
TRUNK LINE
40 KM
CUSTOMER LOCATION
TAP-OFF POINTS
CGD
SPURLINES
Compressor
Starting Point
TYPICAL SCHEMATIC FOR MODELLING PIPELINE SYSTEM
Modeling and Simulation
- Compressibility
- Improving delivery by making use of line pack which being function
of Pipeline pressure.
Simulator model basically works with various equation of state to
compute the desire result by employing advance numerical solutions
technique. Most of the simulator models have been developed by
various companies who have been involved in pipeline design or
information technology solution including monitoring & Control of
Physical parameters.
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Hydraulics /Simulation
Flow Equation
- General flow equation
- Cole-Brook white equation
- Modified Cole-Brook White equation
- AGA equation
- Weymouth equation
- Panhandle A Equation
- Panhandle B equation
The General Flow equation , also called the fundamental flow equation, for the steady state
isothermal gas flow in a gas pipeline is the basic equation for relating the pressure drop with
flow rate
Qb = 1.15 x 10^-3 * (Tb/ Pb) ( P1^2-P2^2 / G Tf L Z f ) ^0.5 * D^2.5
Where
Qb- gas flow rate in m3/day, Tb- base temperature , K (273+deg.C), P1- U/S pressure in kpa
f- friction factor, P2 –down stream pressure , kpa, G- gas gravity (air=1.00)
Pb- base pressure in kpa , Tf –average gas flow temperature, K (273+deg.C)
Z-gas compressibility factor at the flowing temperature , D-pipe inside diameter
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Velocity in Pipes
- Represents the speed at which gas molecules move from one point to another
- Due to compressibility , the gas velocity depends upon the pressure
- Vary in pipeline, even the pipe diameter is constant
- Highest velocity at the down stream of pipeline where the pressure is the least
- Least velocity at the up stream where pressure is higher
The gas velocity at any point in a gas pipeline is given by
u=14.74 (Qb/D^2) (Pb/Tb) (ZT/P)
Where
u – gas velocity( m/s) , Qb - gas flow rate, measured at standard condition
( m^3/day), D- pipe inside diameter ( mm ), Pb- Base pressure (Kpa), Tb- average
gas flowing temperature (deg. K), Z- compressibility factor at the flowing
temperature, dimensionless
Erosional Velocity
-Gas velocity is directly related the flow rate. As the flow rate increases, so the gas
velocity increases.
-As the velocity increases, vibration and noise are evident
-Higher velocities will cause erosion of the pipe interior over a long period of time.
u (max) =100 / (d) ^1/2
u (max) – ft/ s, d = gas density at flowing temperature , lb/ ft ^3
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Reynolds Number
-Reynolds number is used to characterize the type of flow in a pipe, such as laminar, turbulent
or critical flow
- It is also used to calculate the friction factor in pipe flow
- It depends upon property of gas, pipe diameter etc.
Re = u D d / n
Where
Re- dimensionless, u-average velocity (m/s), D- inside diameter (mm),
d- gas density(kg/m^3), n-gas viscosity (kg /m-s)
The Reynolds number is
Re =0.5134 (G Qb/n D) (Pb/Tb)
Where
G – specific gravity of gas (air=1.0), Qb - gas flow rate, measured at standard
condition ( m^3/day), D- pipe inside diameter ( mm ), Pb- Base pressure (Kpa), Tbaverage gas flowing temperature (deg. K), n-viscosity of gas , poise
Laminar flow – The Re. No. is less than and equal to 2000
Turbulent flow - The Re. No. is greater 4000
Critical flow - The Re. No. is undefined and in between 2000 and 4000
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Friction factor
- Friction factor is dimensionless parameter and depends upon Reynolds Number of flow.
- Darcy and Fanning two friction factor are generally used, But Darcy friction factor is more
common.
Friction factor (ff )
= Darcy Friction factor (fd) /4
Moody diagram is graphic plot of the variation of the friction factor with the Reynolds number
for various values of relative pipe roughness. It is a dimensionless parameter obtained by
dividing the absolute (or internal pipe roughness )by the pipe diameter.
Where
Re- dimensionless, u-average velocity (m/s), D- inside diameter (mm),
d- gas density(kg/m^3), n-gas viscosity (kg /m-s)
Relative roughness : e / D
Where
e = absolute or internal roughness of the pipe (mm)
D= pipe inside diameter (mm)
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Modeling and Simulation
Moody diagram
Critical
Turbulent
Pipe internal Roughness
Pipe Material
Roughness
(mm)
•Riveted Steel
0.9 to 9.0
•Commercial/
0.045
Welded Steel
•Cast Iron
0.26
•Galvanized Iron
0.15
•Asphalted Cast Iron
0.12
•Wrought Iron
0.045
•PVC, drawn tubing, glass 0.0015
•Concrete
0.3 -3.0
Roughness
Friction factor
Laminar
Reynolds Number
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Modeling and Simulation
Other Parameters
- The effect of intermediate delivery volumes and gas injection rates along a gas pipeline
- The effect of contract delivery pressure, and regulating the pressure through control valve
- Thermal effects due to heat transfer between the gas and the surrounding soil in the buried
pipe due to
Soil temperature
Thermal Conductivities
Joule Thompson Effect
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Optimization
Pipeline Configuration
- Without Intermediate Compressor
- With Intermediate Compressor
- With Intermediate Compressor and Loop Lining
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Optimization
Pipeline Configuration
- The total pressure required for transporting gas in a pipeline under various configuration,
such as series and parallel
100MMSCMD
80 MMSCMD
50MMSCMD
Series
20 MMSCMD
30 MMSCMD
50MMSCMD
Parallel
100MMSCMD
50 MMSCMD
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Optimization
Metering System
Orifice
Standard
AGA Rep 3
Accuracy
< 1%
Turbine
Ultrasonic
AGA Rep. 7
AGA Rep. 9
+/_0.5 %
Rangeability
3:1
10:1
Pressure Loss
(Kg/Cm2g)
0.5
0.1
Cycle Flow
Variation
Generally
over reg.
Liquid in gas
Corrosion &
erosion
Appreciable
Corrosion &
damage to moving
parts
< +/- 0.5%
50:1
Negligible
Not Affected
Corrosion possible
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Rahul Gautam Chief Manger (Pipeline) Project Development GAIL(INDIA) LTD
Contd.…
Thank You
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