O
PY
Group Practice
C
GP 22-20
D
O
N
O
T
Flare Details for General Refinery and Petrochemical
Service (ISO 25457 or API 537)
5 October 2010
Engineering Technical Practice
Engineering
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Table of Contents
Page
Foreword ........................................................................................................................................ 4
Introduction ..................................................................................................................................... 5
Scope .................................................................................................................................... 6
2
Normative references............................................................................................................. 7
3
Terms and definitions............................................................................................................. 8
PY
1
Symbols and abbreviations ........................................................................................................... 10
Design ................................................................................................................................. 11
4.1
Introduction ............................................................................................................... 11
4.2
System design .......................................................................................................... 11
4.3
Process definition...................................................................................................... 23
4.4
Types of flares .......................................................................................................... 24
4.5
Flare burners ............................................................................................................ 40
4.6
Mechanical design .................................................................................................... 43
4.7
Pilots......................................................................................................................... 45
4.8
Pilot ignition systems ................................................................................................ 48
4.9
Pilot flame detection.................................................................................................. 49
4.10 Piping........................................................................................................................ 50
4.11 Auxiliary components................................................................................................ 52
4.12 Controls and instrumentation .................................................................................... 53
4.13 Precommissioning and commissioning ..................................................................... 59
4.14 Operations ................................................................................................................ 60
4.15 Inspections................................................................................................................ 60
5
Mechanical details - Elevated flares..................................................................................... 61
5.1
Mechanical design - Design loads............................................................................. 61
5.2
Design details ........................................................................................................... 63
5.4
Welding..................................................................................................................... 65
5.5
Inspection ................................................................................................................. 65
5.8
Aircraft warning lighting............................................................................................. 65
5.9
Platforms and ladders ............................................................................................... 65
D
O
N
O
T
C
O
4
6
Mechanical details - Enclosed-flame flare ............................................................................ 66
Copyright © 2010 BP International Ltd. All rights reserved.
This document and any data or information generated from its use are classified, as a
minimum, BP Internal. Distribution is intended for BP authorized recipients only. The
information contained in this document is subject to the terms and conditions of the
agreement or contract under which this document was supplied to the recipient's
organization. None of the information contained in this document shall be disclosed
outside the recipient's own organization, unless the terms of such agreement or contract
expressly allow, or unless disclosure is required by law.
In the event of a conflict between this document and a relevant law or regulation, the
relevant law or regulation shall be followed. If the document creates a higher obligation, it
shall be followed as long as this also achieves full compliance with the law or regulation.
Page 2 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
6.1
6.2
6.3
6.4
6.5
6.7
7
Combustion chamber................................................................................................ 66
Burners ..................................................................................................................... 69
Burner piping ............................................................................................................ 70
Pilots......................................................................................................................... 71
Wind fence................................................................................................................ 71
Guaranties ................................................................................................................ 72
Documentation..................................................................................................................... 73
Annex D (Informative) Instructions for flare data sheets................................................................ 74
Introduction.......................................................................................................................... 74
D.2
General information forms - Instructions .............................................................................. 76
D.2.1 Form Gen 1............................................................................................................... 76
D.2.2 Form Gen 2............................................................................................................... 76
D.2.3 Form Gen 3............................................................................................................... 77
D.2.4 Form Gen 4............................................................................................................... 79
D.2.5 Form Gen 5............................................................................................................... 79
D.2.6 Form Gen 6............................................................................................................... 80
D.2.7 Form Gen 7............................................................................................................... 80
D.3
Elevated-flare forms - Instructions........................................................................................ 80
D.3.1 Form Elev 1 .............................................................................................................. 80
D.3.2 Form Elev 2 .............................................................................................................. 81
D.3.3 Form Elev 4 .............................................................................................................. 81
D.3.4 Form Elev 5 .............................................................................................................. 81
D.4
Enclosed-flare forms - Instructions....................................................................................... 82
D.4.1 Form Enc 1 ............................................................................................................... 82
D.4.2 Form Enc 2 ............................................................................................................... 82
D.4.3 Form Enc 3 ............................................................................................................... 82
D.4.4 Form Enc 4 ............................................................................................................... 83
D.4.5 Form Enc 5 ............................................................................................................... 83
N
O
T
C
O
PY
D.1
O
Bibliography .................................................................................................................................. 84
List of Tables
D
Table 1 - Number of pilots for a single point flare .......................................................................... 47
Page 3 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Foreword
This is a revised issue of Engineering Technical Practice (ETP) GP 22-20. This Group Practice (GP)
has been substantially revised due to major revision of ISO 25457/API Std 537.
D
O
N
O
T
C
O
PY
This GP has also been updated and revised in several areas to reflect learnings and best practices in
various BP assets. These changes are so extensive that revisions have not been indicated by a bar in
the margin, as is normal practice.
Page 4 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Introduction
Requirements for Flare Details are based on ISO 25457:2008/API Std 537.
b.
Requirements of this GP are modifications to ISO 25457/API Std 537.
c.
Modifications to ISO 25457/API Std 537 are identified as Add, Modify to Read, or Delete.
d.
Paragraph numbers in this specification correspond to ISO 25457/API Std 537.
e.
Paragraphs of ISO 15457/API Std 537 that are not revised remain applicable.
PY
a.
O
Users of this GP should be aware that further or differing requirements might be needed for
individual applications. This GP is not intended to inhibit a vendor from offering (or BP from
accepting) alternative equipment or engineering solutions for the individual application. This
may be particularly applicable if innovative or developing technology is proposed. If an
alternative is offered to BP, the vendor should identify any variations from this GP and provide
details.
D
O
N
O
T
C
ISO 25457/API Std 537 is based on the SI system of units. Therefore, SI units are used
throughout this GP. As practical, U.S. customary units are included in parentheses.
Page 5 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
1
Scope
Add
This GP provides practice for selection, design, materials, fabrication, construction,
installation, testing, maintenance, and operation of flare gas disposal systems based on
engineering principles defined in ISO 25457/API Std 537.
b.
This GP and ISO 25457/API Std 537 specifically address flares and related combustion
and mechanical components used in pressure relieving and vapour depressurising systems
for petroleum, petrochemical, and natural gas industries.
c.
This GP is applicable to the design and installation of new plants and facilities and may be
used for assessment and modification of existing plants and facilities.
d.
This GP complements GP 44-70 and GP 44-80.
PY
a.
O
While GP 44-70 and GP 44-80 cover the process aspects of relief systems, this GP
covers issues associated with the flare as a disposal device, such as selection and
design issues, and provides greater details for mechanical design requirements.
C
There may be some duplication on covered topics in these GPs. These duplications
are considered as necessary and complementary with the sole purpose to aid
readers in better understanding issues related to presented topics.
T
ISO 25457/API Std 537 provides instructions for data sheets in Annex D and flare
data sheets in Annex E. Modified Annex D is included in this GP. However, Annex E
is not included in this GP. Both annexes will be included in a future edition of
DS 22-201.Until the data sheet (DS) is available, the user can use data sheets
provided in ISO 25457/API Std 537, Annex E and modified Annex D, included in this
GP.
N
O
Data sheets can be selected with SI units or U.S. customary units. Use of these data
sheets for new and existing flare systems is recommended. Completed equipment
data sheets provide a uniform means of recording and communicating design
information, such as general information, process design conditions, mechanical
design data, and system performance data.
ISO 25457/API Std 537 does not include issues associated with design of system for
relieving gases by venting into atmosphere. These issues are primarily addressed in
GP 44-80 and, as appropriate, in this GP.
The following additional types of flares that are not part of ISO 25457/API Std 537 are
within the scope of this GP:
O
e.
Pit flares.
2.
Marine or sea flares.
3.
Flares for offshore installations or floating production systems (FPS).
4.
Portable/temporary flares.
D
1.
f.
This GP provides practice for flare system design and operation for the following:
1.
Hydrocarbon processing plants, including refineries, natural gas installations, and
chemical plants.
2.
Steam and/or power generating plant and ancillary equipment.
3.
Terminals, including jetty and loading facilities.
4.
Offshore installations, including floating production systems.
Page 6 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
5.
Petroleum production facilities, including well pads and crude oil and gas gathering
centres.
6.
Storage installations.
7.
Vacuum systems and systems relieving at a pressure less than 1 barg (14,5 psig).
8.
Utility systems.
9.
Components of drilling systems on BP operated platforms in which the drilling rig is
an integral part of the facility or mobile drilling rigs that are owned or operated by
BP.
PY
10. Ships, vessels, such as floating production storage offload (FPSO), and road/rail
tanks, for which the system is a special purpose built facility that would normally be
considered a processing plant. This GP does not apply to other ships, vessels, or
road/rail tanks.
11. Well testing facilities.
Mobile drilling rigs or other equipment that are owned by others and assembled, as
required, on the facility are not covered in this document.
O
g.
C
Although BP does not own or operate mobile drilling rigs in most circumstances,
gaps and risks against this GP should be assessed, and risks should be mitigated if
these drilling rigs are being contracted.
Annexes A, B, and C that are included in ISO 25457/API Std 537 as informative
documents (but not included in this GP) provide further guidance and best practices for
flare selection, flare design, mechanical details, operation, and maintenance of flare system
and related equipment.
i.
Caution to user: ISO 25457/API Std 537 states that Annexes A, B, and C are informative
documents only. However, some statements/language used in these Annexes, such as
“shall” and “should”, may imply that requirements are mandatory. The mandatory
requirements are included in the ISO sections and this GP. This GP accepts the content of
these Annexes in unchanged form but as informative documents only.
j.
ISO 25457/API Std 537, Annex D, explains how to use the flare data sheets provided in
Annex E. This GP includes Annex D. The flare data sheets in Annex E are not included but
are available as separate documents in the ETP library or in ISO 25457/API Std 537. The
intent of flare data sheets is to provide, communicate, and record design information for
new flares or to record data for existing flares.
N
O
T
h.
Normative references
O
2
Add
D
BP DS 22-200
BP GDP 3.6-0001
BP GIS 72-001
BP GIS 72-002
BP GIS 72-003
BP GP 15-01
BP GP 30-10
BP GP 32-10
Flare Data Sheet (Under development; not yet published).
Environmental and Social Requirements for New Access Projects, Major
Projects, International Protected Area Projects and Acquisition
Negotiations.
Procurement of Refractory - Firebrick, Insulating Firebrick, Ceramic
Fibre (RCF), Alkaline Earth Silicate Wool (AESW), and Ferrules.
Refractory Installation.
Refractory Dryout.
Noise Control.
Nonfiscal Flow Instruments (Class 2 and Class 3).
Quality Management for Manufacturing - Overall Strategy.
Page 7 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Site Inspection, Testing, and Commissioning of Plant.
In Service Inspection and Testing of Onshore Civil - Structural Facilities.
In Service Inspection and Testing of Special and Other Equipment.
Overpressure Protection Systems.
Relief Disposal Systems.
Series on flow measurement.
Design and Selection of Refractory Lining Systems.
Guide for Pressure-relieving and Depressuring Systems.
Fired Heaters for General Refinery Services.
Centrifugal Fans for Petroleum, Chemical, and Gas Industry Services.
Process Piping.
Insulating Firebrick.
Standard Classification of Alumina and Alumina-Silicate Castable
Refractories.
Code of practice for protection of structures against lightning.
Method for Determining the Sound-Power Levels of Flares Used in
Refineries, Chemical Plants and Oilfields.
Protection of Environment. Standards of Performance for New Stationary
Sources. General control device requirements.
Protection of Environment. National Emission Standards for Hazardous
Air Pollutants for Source Categories. Control device requirements.
PY
BP GP 32-20
BP GP 32-46
BP GP 32-49
BP GP 44-70
BP GP 44-80
BP GP 64-xx
BP GP 72-00
API Std 521
API Std 560
API Std 673
ASME B31.3
ASTM C155
ASTM C401
O
BS 6651
CONCAWE 2/79
C
EPA 40 CFR 60.18
EPA 40 CFR 63.11
Terms and definitions
T
3
Modify to Read
3.29
flare
Add
N
O
Terms used in ISO 25457/API Std 537 as they relate to flares are defined in 3.1 through 3.63. In
addition, the following terms and definitions are added or modified:
Flare may take the form of flare stack, flare boom, ground flare, and/or enclosed flare.
O
3.30
flare burner
flare tip
D
Add
Flare burner includes all auxiliaries as attached to supporting stack or boom.
3.32
flare stack
flare boom
flare tower
Add
Flare boom is a horizontally displaced or inclined structure, together with other items listed for
flare stack.
Page 8 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Elevated stack (either self supported, guyed, or structure supported) supports other flare
components, such as the flare burner, pilot burners, igniters, smoke suppressing devices, flame
heat radiation suppressing devices, service pipes, and miscellaneous auxiliaries.
3.48
pin-actuated device
Add
Pin actuated devices can be reset in place without breaking a flange and may be considered
as alternative for rupture disc device.
b.
Pin actuated valves are more costly than rupture disk devices.
c.
Pin actuated valves are typically vendor proprietary designs. Design features and operating
characteristics need to be reviewed if pin actuated valves application is considered.
PY
a.
3.55
smokeless capacity
O
Add
Requirements are defined by local standards, such as UK Clean Air Act 1956, Section 34(2),
and U.S. EPA 40 CFR 60.18.
C
Add
T
3.64
Flare system
Closed disposal system for relief fluids discharged from pressure relief valves, other pressure relief
devices, control valves, or manually operated valves that terminate in one or more flares.
O
3.65
Flare vendor
Contractor who undertakes design, supply, and erection of flare or one or more of these activities.
N
3.66
Marine or sea flare
Flare remotely located from drilling/production platform. These types of flares are typically used in
shallow water platforms.
D
O
3.67
Radiation shield
Structure, typically steel plate or other heat resistant materials, that provides personnel or critical
equipment protection from intensive heat radiation emitted by flare flames.
3.68
Variable orifice
Flare tip that continuously changes size of exit orifice to maintain higher exit velocities, contributing
to better mixing between air and gas and achieving higher nonsmoking rates.
3.69
Water injection
System that provides water injection into flare combustion zone to achieve flame temperature
reduction and lower heat radiation rates emitted by flare flames.
Page 9 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
3.70
Water curtain
System consisting of numerous spray nozzles that provide water curtain protection from intensive heat
radiation emitted by flare flames.
3.71
Combustion support
Addition of fuel gas to effluent to be flared for any of the following reasons:
Increase fuel concentration to make effluent flammable and achieve required combustion
destruction efficiency.
b.
Increase volume of effluent to increase flare tip velocity to avoid the following:
PY
a.
1.
Burnback in flare tip.
2.
Flame lick outside flare tip.
3.
Lazy flame situation that could damage adjacent flare tip.
Maintain adequate slot velocity in flare tip using Coanda effect.
d.
Increase flame stability during high wind conditions (only as temporary solution until flare
flame instability is resolved).
O
c.
T
C
3.72
FPSO
Floating production storage and offloading (vessel). Ship used to store and offload hydrocarbon oil
and gas production.
O
3.73
FSO
Floating storage and offloading (vessel). Ship without hydrocarbon processing facilities used to store
and offload hydrocarbon liquids.
N
3.74
Jin pole
Jin poles and lifting cables are provided with derrick supported flare stack to facilitate removal of flare
burner.
O
Symbols and abbreviations
For the purpose of this GP, the following symbols and abbreviations apply:
Computational fluid dynamics.
DCS
Distributed control system.
E&C
Engineering and construction.
EA
Engineering authority.
EPA
Environmental Protection Agency.
FPSO
Floating production, storage, and offloading (vessel).
HP
High pressure.
LHV
Lower heating value.
LNG
Liquefied natural gas.
D
CFD
Page 10 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Low pressure.
LPG
Liquefied petroleum gas.
MMS
Minerals Management Service.
PSV
Pressure safety valve.
RCF
Refractory ceramic fibres.
SS
Stainless steel.
VOC
Volatile organic compound.
4
Design
4.1
Introduction
PY
LP
Add
b.
Technical guidance in the informative annexes addresses alternative designs or techniques
and provides good practice on the basis of which, through sound engineering judgment, the
practitioner can make appropriate design decisions and selections.
c.
In addition, some specific BP requirements are added in the appropriate clauses of this GP.
d.
The finalised basis of new flare design shall be recorded on data sheets (e.g., those
provided in ISO 25457/API Std 537, Annex E and in DS 22-200) to properly communicate
requirements and preserve design information.
e.
The standard data sheets may be used for existing flares to properly document and preserve
design information and current operating conditions.
f.
Annex D provides instructions for completing the flare data sheets in Annex E and is
included in this GP.
O
T
C
O
Functional requirements in this GP are in concurrence with ISO 25457/API Std 537 and
are supported by the technical guidance in Annexes A, B, and C.
System design
N
4.2
a.
Modify to Read
Selection of the most appropriate type and configuration of a flare system shall be based on
process and facility specifics outlined in the flare data sheets.
b.
Major and optional components for flare systems as discussed in 4.2 follow:
O
a.
Flare burner with or without smoke suppression capability.
2.
Pilot(s).
3.
Retractable pilot(s) (optional).
4.
Pilot igniter(s).
5.
Pilot flame detector(s).
6.
Automatic pilot relighting system (may be required or considered optional pending
the results of impact assessment analysis).
7.
Retractable thermocouple(s) (optional).
8.
Buoyancy or velocity seal (optional).
9.
Support structure.
D
1.
10. Knockout drum (optional).
Page 11 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
11. Flame/detonation arrestor (optional).
12. Liquid seal (optional).
13. Piping.
14. Smoke suppression control system (optional).
15. Blower(s) (optional).
16. Ladders (caged or with safety climbing system) and platforms (optional).
17. Davit for tip removal (optional).
18. Aircraft warning lights and painting (optional).
PY
19. Radiation heat shields (optional).
20. Rain shields (optional).
21. Flashback prevention (optional).
23. Isolation system (optional).
24. Gas sampling system (optional).
25. Oxygen analyser (optional).
O
22. Purge system.
C
26. Flow, temperature, and level measurements and alarms (optional).
27. Pumpout facilities for drum (optional).
28. Fire protection (optional).
T
29. Flame snuffing system (optional).
30. Insulation (optional).
O
31. Heating and heat tracing (optional).
32. Cold liquid/vapour vapourisation and heating system (optional).
4.2.1
N
33. Flare gas recovery system (optional).
Objective
Modify to Read
Functional requirements
D
4.2.2
O
The objective is to identify fundamental requirements, specific design criteria, and information
consistent with delivery of critical safety and operating goals of the specific flare under design.
The same criteria can be used for existing flares to document the current state of flare in
operation and identify possible gaps.
Modify to Read
a.
Fundamental process system design requirements shall be established primarily in
accordance with GP 44-70 and GP 44-80, from which all aspects shall be defined in the
flare data sheets.
b.
Safety and well being of all personnel in the vicinity (both onsite and offsite) under all
conditions shall be the guiding principle for flare system design. This includes startup,
purging, operational and emergency flaring, shutdown, inspection, and maintenance of all
or parts of the system.
Inherently safer design philosophy as described in GP 48-04 should be used if
possible for the flare system design.
Page 12 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Examples of inherently safer design features for flare systems include:
The following are primary issues that need to be addressed:
1.
Plot space/layout considerations.
2.
Design flow cases from the pressure relieving and vapour depressurising system,
including maximum continuous case and maximum intermittent case.
3.
Specified flare capacity shall represent actual anticipated operating conditions based
on the following criteria:
Final flare selected design capacity shall not be over or under specified design
capacity in flare data sheets.
C
a)
O
c.
Use of multiple pilots.
Pilots with redundant gas supply to ensure will ignite.
Pilot redundant ignition system.
Pilot flame status monitoring.
Automatic pilot relighting system.
Flare burner protection from internal burning.
Selection of flare system materials to mitigate corrosion issues.
Mitigation of flame radiation heat.
PY








Design should not be based on conditions that rarely occur during life of the
flare while sacrificing every other design criteria, such as reliability and
flexibility.
c)
Operating range of the flare shall be determined and specified. The flare shall be
operated within operating range that is specified in flare design.
N
O
b)
d)
Smokeless capacity shall not be less than capacity specified in flare data sheets.
Minimum flow to internal parts of flare burner shall be determined by design and
shall be maintained during flare in service to provide adequate internal cooling and
eliminate potential for internal burning.
O
4.
T
Overcapacity and under capacity selection in flare burner design (for various
reasons, such as anticipated future needs for capacity increase or decrease,
applying a “safety capacity factor”, etc.) could result in flare burner inferior
performance and reduced burner reliability. If capacity is increased or decreased in
future operation of the flare, a new flare burner (sized for revised capacity) could be
installed as the replacement of the original flare burner.
Flare burner design and selection shall address intermediate or low turndown cases
that may result in “burnback” within the burner.
6.
Minimum flare purge requirements to prevent flashback shall be determined.
D
5.
7.
Typically, the flare vendor provides minimum purge requirements for flare riser and
burner protection from flashback. This requirement varies with flare burner design.
The flare burner design is typically a proprietary design and purge requirements
may be different than flare blowdown line purge requirements that are established
by GP 44-80.
Rates for fuel gas assist to achieve flame stability and destruction efficiency in
accordance with applicable legal and regulatory requirements set by permit shall be
determined.
Page 13 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
8.
Type and quantities of assisting media to comply with smokeless rates in accordance
with applicable legal and regulatory requirements set by operating permit shall be
determined.
During the design stage and bidding process, the flare vendor shall typically
determine and specify quantities of assisting media to comply with smokeless rates
requirements set by operating permit. In the enquiry, BP will typically provide
information on available assisting media for applicable flare system.
9.
Flare staging requirement and method.
10. Allowable flare burner exit velocity.
PY
If practical, the assessed quantities of assisting media provided by the vendor are
typically based on actual flare burner test data either from vendor test installation
or field data from a similar flare application.
11. System hydraulics with respect to allowable pressure drop, static pressure, and
diameter of the flare.
C
O
BP or its designated representative will typically perform hydraulic design for the
overall pressure relief system and set allowable backpressure for flare system. Flare
vendor may, however, be requested to review and confirm if the proposed design is
adequate and explain the basis and methods used for determining system pressure
losses if losses differ from BP provided design. The bases used by BP for system
hydraulics design are outlined in GP 44-80.
12. Performance requirements in accordance with applicable legal and regulatory
requirements related to destruction efficiency, smokeless capacity, opacity limits,
pilot(s) flame monitoring and reporting, and permissible noise limits.
T
13. Method for flare operating control and performance monitoring.
14. Operating performance, such as peak radiation intensity at grade.
O
15. Functional description of the intended system operation.
16. Selection of major system components that can be integral to the flare, such as a
knockout drum, liquid seal, buoyancy seal, or purge reduction device.
N
17. Design meteorological and any other relevant environmental conditions pertaining to
the site.
18. Requirement for cold liquid/vapour vapourisation and heating system in situations for
which cold flare cannot be justified.
O
19. Need for prevention from freezing of wet streams, solidification of viscous materials,
or reactions that could lead to plugging of lines.
D
20. Need for segregation of relief headers for reasons of temperature, toxicity, corrosive
materials, etc.
For design issues related to toxic gas relief, corrosive relief, low temperature relief,
relief materials with plugging tendencies, and winterisation, refer to the special
relief arrangements clause in GP 44-80.
21. Handling systems for safe disposal of condensed hydrocarbons and sour water from
both knockout drums and seal drums.
22. Secure supply of seal fluid to seal drum with provision to prevent overfill to flare,
header, and knockout drum(s).
23. Utilities available.
24. Required life of flare system components.
Page 14 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Normally, process components have a design life of 20 yr. However, selection of
design life for particular components is at the discretion of the facility designer. Any
components that have a design life that is different from the system design life
should be clearly identified and appropriate plans for inspection, maintenance, and
replacement put in place.
25. Philosophy to be adopted on inspection and maintenance of flare system and flare
system critical components and possible impact of these requirements on plant
operation (flare system sparing requirements).
d.
GP 44-80 provides a checklist of potential hazards that should be reviewed and be
considered in the design of flare systems.
4.2.2.1
Smokeless flaring
4.2.2.1.1
General
PY
Add
C
O
Smokeless flares eliminate noticeable smoke over a specified range of flows.
Smokeless combustion is achieved by using gas, air, steam, pressure energy, or
other means to create turbulence and entrain ambient air into flame or within the
flared gas stream. Smoking is defined by Ringelmann numbering scale (i.e.,
#1 Ringelmann is 20% opacity, Ringelmann 0 is clear).
Typically, the smoking tendency is a function of the gas calorific value and the
bonding structure of hydrocarbons. The paraffinic series of hydrocarbons has the
lowest tendency to produce smoke, whereas olefins, diolefins, and the aromatic
series of hydrocarbons have a much higher tendency to produce smoke.
T
Requirement for smokeless operation is normally the overriding requirement in
designing a burner for a flare system.
a.
N
O
Other clauses in this GP cover mechanical details on design, operation, and
maintenance of a smoke suppression system used on flaring devices. This clause
addresses selection and design issues associated with application of a smoke
suppression system.
Smokeless flaring shall be subject to the following:
1.
Flowrates for both smokeless and non-smokeless flaring shall be either:
O
2.
Smokeless flaring shall comply with legal and regulatory requirements applicable to
the site.
a)
Specified by BP in data sheets.
b)
Submitted by the flare vendor in its proposal.
D
The BP responsible engineer shall approve the final flowrates provided by the vendor.
These requirements are typically determined by operating permit and are included
in BP flare data sheets.
The nonsmoking rates are heavily influenced by flare burner design and selection.
The flare burner design is typically a vendor proprietary design. Therefore, the
smokeless rates offered by flare vendors may vary significantly for a particular
application.
3.
The design shall provide smokeless flaring for all cases of “routine” operational
flaring (i.e., a controlled release of fluid to flare system for a continuous period
exceeding 30 min or minimum amount allowed by legal and regulatory
requirements).
Page 15 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Unless data sheets require higher rate or smokeless capacity for entire range (not
commonly the case), typical nonsmoking flaring rates are approximately 20% of the
maximum flaring capacity.
4.
Depending on specific facility or legal and regulatory requirements, the requirements
for smokeless flaring may be relaxed for periods of flare abnormal operation (e.g.,
initial commissioning, startup, and shutdown).
5.
To achieve smokeless combustion, the following criteria should be addressed by flare
design:
A minimum critical combustion temperature shall be determined by flare design.
The temperature should be maintained during flare operation to achieve thermal
destruction efficiency set by regulations or operating permit.
PY
a)
O
Destruction efficiency is heavily dependant on achieved combustion temperature.
Actual achieved combustion temperature (measured and maintained) is difficult to
assess during flare operation. There is no effective method to determine actual flare
combustion temperature because the temperature is so dependant on various
factors. The EPA and other regulating agencies have no choice other than to accept
flare vendor data/guaranties. Vendor provided data, due to practical limitations in
test facilities, may and may not be based on actual test data. Most of vendor data is
based on up or down model predicted scale change from actual test results.
C
b) If calorific value of flare gases is not adequate to fulfil minimum critical
combustion temperature condition, an enclosed flare or thermal oxidiser should
be used instead of open flame flare.
O
T
Smoking in flare operation is indication of incomplete combustion. Incomplete
combustion may be caused by either lack of combustion air or drop in combustion
temperature. Also, smoking could be caused by inadequate mixing (that is a function
of the flare burner design/selection for particular application) or as a result of
damage to the flare/burner.
Excessive use of assisting media (such as steam or air) to achieve smokeless flaring
could cause combustion temperature reduction and incomplete combustion resulting
in increased flare emissions.
b.
An adequate supply of air mixed sufficiently with the fuel.
N
c)
The following methods should be considered by BP and flare designer to achieve
requirement 5.c) in flare selection and performance:
Primary emphasis shall be given for design for which inlet gas supply pressure is used
to minimise smoking of flared gas.
O
1.
D
Multiple burner heads that are staged to operate and provide smokeless flare
operation may also be considered.
2.
Energy from additional fuel gas injection inspirating additional air into combustion
zone should be used.
This type of flare burner may be used for flares for which other means of smoke
suppression system, such as steam, air assisting, or high differential pressure across
flare burner, are not available, are not economical solutions, or cannot be used. The
system requires adequate gas pressure and has a poor turndown ratio.
In this type of flare, use of additional gas would be required, resulting in increased
costs of flaring, increased radiation, and higher flare emissions. Also, the reliability
of this type of flare is poor, due to higher heat loads on flare burner caused by use
of additional fuel gas for air inspiration.
Page 16 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
3.
Inspirating additional air into the flare burner combustion zone by using the Coanda
effect. The following are requirements for Coanda flare burner slot design:
a)
Slots shall be wide enough not to get blocked by impurities in the gas stream or
smoke suppressing media and protected against ambient conditions, such as
liquid carryover, icing, rain, and dust.
b)
If variable slot is used, additional protection from system overpressure due to
slot blockage or variable slot mechanism failure shall be provided. A reliable
bypass around the variable slot flare burner shall be used. The reliable bypass
should contain a full sized rupture disk, liquid seal drum, or buckling pins
installed in parallel.
PY
This method uses the aerodynamic skin adhesion effect known as the Coanda effect,
in which high pressure gas flowing from a narrow slot follows the profile of a
curved surface, entraining air up to 20 times its own volume and introducing oxygen
and turbulence required for complete combustion.
Steam may be used in Coanda flare burner to draw in additional air for mixing with
gas. The Coanda slot may be may be fixed or variable.
Providing a highly turbulent condition within the flame.
O
4.
C
Highly turbulent conditions within the flame, required for smokeless combustion,
may be achieved by using energy of incoming flare gas (multiport tips) or by
causing turbulence with use of assist media (such as steam, water, or air injection).
Also, selection of assisted media and required quantities are affected by flare tip
design/selection for particular application.
O
T
Steam assist can be achieved either by the discharge of multiple steam jets into the
combustion zone or by a high velocity steam jet centrally placed in the flare burner.
Both methods may be combined in one flare burner. The energy of steam entrains
air and creates enough turbulence to attain efficient mixing of fuel and air. Steam
assisting can also be accomplished by using steam/air tubes located internally or
externally in flare burner.
c.
Smoking shall be defined by Ringelmann numbering scale.
d.
Utility consumption estimates for proposed design shall be provided.
Smokeless flaring using steam assist
O
4.2.2.1.2
N
Air assist is typically achieved by injecting the flare gas flow into incoming air flow
at the flare tip discharge zone.
For flares using steam for smoke suppression, the following shall be observed and addressed:
Flares in the U.S.
1.
For steam assisted flares in the U.S. to qualify flare to be EPA approved regulated
VOC control device for disposal of relief gas streams, flare design and operation shall
comply with EPA 40 CFR 60.18 and EPA 40 CFR 63.11.
2.
These CFR regulations require that flare relief gas stream contains a minimum
calorific value of 11 175 kJ/scm (300 Btu/scf) and that burner flaring gas exit velocity
shall not exceed 18,3 m/s (60 ft/s).
D
a.
For flares located outside the U.S. and not subject to any permit requirements or
local regulations, EPA regulations or some other rules, if available, that are more
convenient and cost effective could be applied to flare design and operation.
b.
Height of steam assist smokeless flare should be designed for the limiting case during
which the flare can be required to operate without steam assist. This case can produce the
greatest flare radiation.
Page 17 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
See GP 44-80 for more information regarding flare radiation.
c.
The flame should not be over aerated with excessive use of assist steam.
Over aeration can produce combustion instability, reduce destruction efficiency,
and increase flare noise and vibration. At an extreme, excessive assist steam flow
can extinguish the flame.
d.
Steam consumption rates to promote smokeless burning and ability of different types of
flare burners to handle liquid hydrocarbon droplets should comply with rates and
guidelines in ISO 25457/API Std 537 or API Std 521.
PY
Steam consumption varies widely as a function of the particular gas being flared
and the manufacturer proprietary design of the flare burner. Ultimately, vendors
should be consulted for steam rate requirements for their specific flare burner
design.
The system shall be designed to provide dry steam at the flare burner, with the steam
pipework suitably insulated to avoid steam condensation introduced to the flare burner,
resulting in extinguishing the pilots or mechanical damage.
f.
The system shall be designed to provide ability for steam condensate to be drained from
the internal steam/air injection point and from any muffler surrounding the tube
assemblies.
g.
Drainage, with steam traps, shall be provided at the low points.
h.
Steam lines shall be frost protected.
i.
Steam flow should be either automatically or manually controlled in relation to the gas
flow or by the visible characteristics of the flame.
j.
Steam lines should be suitably filtered as close to the flare base as practical but upstream
of the flow control valve.
k.
As specified by the flare vendor, flare user shall design and maintain a minimum flow of
steam to cool pipework at the flare burner. The minimum flow should typically be
provided by a bypass installed around the steam control valve.
l.
Typical steam pressure used in steam assisting flare designs shall be from 210 kPag to
1 050 kPag (30 psig to 150 psig).
m.
Expansion loops shall be installed in the steam riser, as required.
n.
Care should be taken while operating centre steam systems in cold environments. The
potential exists to form an ice plug that reduces the hydraulic capacity of the flare below
that needed for plant safety.
O
N
O
T
C
O
e.
Backflow of combustible mixtures in the internal tubes shall be avoided.
D
o.
4.2.2.1.3
Backburning potential is a hazard with steam/air tubes. The most common cause of
backflow in the tubes is improper flare operation. If the upper steam ring is
pressurised prior to engaging the steam supply to the steam/air tubes, the upper
steam can cap the top of the flare discharge and force flow backward out of the
tubes.
Smokeless flaring using air assist
For air assist for smoke suppression, the following points shall be observed and addressed:
a.
Air assisted flares in the U.S.
1.
For air assisted flares in the U.S. to qualify flare to be an EPA approved regulated
VOC control device for disposal of relief gas streams, flare design and operation shall
comply with EPA 40 CFR 60.18 and EPA 40 CFR 63.11.
Page 18 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
2.
These CFR regulations require that flare relief gas stream contains a minimum
calorific value of 11 175 kJ/scm (300 Btu/scf).
3.
The minimum value of burner flaring gas exit velocity, for flares using air assist, is
not specified in EPA regulations. However, EPA provides methodology that shall be
followed to determine required exit velocity value for each application separately.
Maximum allowable burner flaring gas exit velocity shall comply with EPA
calculation method in facilities that fall under jurisdiction of EPA.
For flares located outside the U.S. and not subject to any permit requirements or
local regulations, EPA regulations or some other rules, if available, that are more
convenient and cost effective could be applied to flare design and operation.
Height of an air assisted smokeless flare should be designed for the limiting case during
which the flare can be required to operate without an air assist. This case can produce the
greatest flare radiation.
PY
b.
See GP 44-80 for more information regarding flare radiation.
Minimum airflow rate shall be maintained to protect the spider arms or internals of the
flare burner from overheating and provide a proper aerodynamic design across the burner
during low relief gas rates.
d.
Flame should not be over aerated.
O
c.
C
Over aeration can produce combustion instabilities, reduce destruction efficiency,
and increase flare noise and vibration. At an extreme, excessive assist airflow can
extinguish the flame.
Purge rate of the air assisted flare should take into consideration the flare burner design,
size, and how forced airflow interacts at turndown conditions with wind and environmental
factors.
f.
A blower system should be designed to produce the design airflow rate and velocity at the
flare burner at the coldest ambient temperature specified in the flare data sheet. Blower
power requirements should be selected with regard to delivery of the densest air (coldest
ambient temperature).
O
T
e.
N
Smokeless burning is achieved with a forced draught air supply. The quantity and
velocity of the forced airflow can be proportioned to the gas flow by a blower
damper, blower speed control, or other means. Alternately, the forced airflow can
also be controlled in discrete steps by multiple speed blowers or multiple blowers.
Noise levels
D
4.2.2.2
O
Blowers of all types, including axial or centrifugal, can be used for air assisted
smokeless flares.
Noise sources include gas exit velocity, combustion produced noise, and noise from
any assist utilities used as smoke suppression. In some cases, noise produced by
components located upstream of the flare can be carried along flare header,
contributing to increase of overall noise emitted by the flare.
The main contributor to flare noise in a smokeless flare using steam is the steam jet
noise. Therefore, in general, the lower the ratio of steam to flared gas, the quieter
the flare.
Tip design can incorporate some noise suppression features, such as use of low
noise injectors, mufflers, and careful distribution of suppressant media at the tip.
Page 19 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
To achieve acceptable flare noise level, the following criteria should be addressed by flare
design:
a.
Noise levels from operational flare systems shall comply with allowable levels in
GP 15-01 for normally manned areas or public exposure.
b.
The flare shall be sited such that, at maximum emergency flowrate, the noise level at
positions normally accessible to personnel shall not exceed 80 dB(A). Detailed noise
requirements are in c.
4.2.2.3
Anticipated flare noise
Typically, flare vendor shall provide data on anticipated noise from flare in its
quotation.
2.
The data shall provide information on noise emission from the flare at maximum
emergency flow and at maximum smokeless flaring rate.
3.
Noise emission data shall be provided based on test or previous installations data and
shall contain the sound-power levels in octave bands from 31 Hz to 8 kHz.
4.
Measurements shall be performed in accordance with CONCAWE report 2/79.
O
1.
C
c.
PY
BP may specify a higher limit if flare is located remotely and is not in proximity to
locations with permanent operator presence or proximity to local residence. Also, a
lower noise limit may be required/applied to a particular case/installation (e.g.,
offshore platform, ground flare, proximity to local residents).
Liquid removal
4.2.2.4
T
For design issues related to liquid removal from flare system, refer to the flare system liquid
removal clause in GP 44-80.
Air infiltration
4.2.2.5
Flame radiation
O
For design issues related to air infiltration into flare system, refer the flare and vent header
purging clause in GP 44-80.
4.2.2.6
N
For design issues related to flare flame radiation, refer to the thermal radiation of atmospheric
vent stacks and flare stacks clause in GP 44-80.
Supplemental fuel gas (combustion support) for flare systems
4.2.2.7
O
For design issues related to supplemental fuel gas for flame systems, refer to the supplemental
fuel gas (combustion support) for flare systems clause in GP 44-80.
Flare gas recovery
D
For design issues related to flare gas recovery system, refer to the flare gas recovery systems
clause in GP 44-80.
4.2.2.8
System cost considerations
To determine overall cost of flare installation, the following major requirements that heavily
influence system performance shall be considered:
a.
Safety, legal, and regulatory requirements (dispersion, smoking limits, radiation limits,
pilot(s) ignition, pilot(s) flame monitoring, noise, etc.).
b.
Type and quantities of released gases and nature of flaring event (toxic or nontoxic fluids,
emergency and routine flaring, etc.).
c.
Type of enclosed disposal system selected (single or multiservice system, etc.).
Page 20 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Disposal device selection (elevated flare, ground flare, enclosed flare, marine and platform
flare, etc.).
e.
Site and plant requirements (distance from unit to flare, additive effect of radiation from
multiple flare installation, potential for burning liquid droplets, etc.).
f.
Construction materials requirements (seawater environment, corrosive products of
combustion, high heat flame intensity, intermittent operation, multiple flare burners in
close vicinity, etc.).
g.
Utilities availability and cost (steam, air, high pressure gas, electricity, etc.).
h.
Accessibility (marine flare, boom flare, site with multiple flares, multiple flare burners on
common stack, remote site location, etc.).
i.
Climate conditions (arctic, desert, offshore, etc.).
PY
d.
For example, API provides the following data for relative costs of elevated flare.
The data is based on flare burner size 305 mm (12 in) and 610 mm (24 in) diameter
(API Publ 931, Table 15.4).
Equipment cost factors
O
Type of flare
305 mm (12 in)
Smokeless, steam burner
Smokeless, gas burner
Smokeless, water burner
1,00
1,25
1,25
1,30
1,30
1,20
1,20
2,80
3,38
T
Smokeless, forced air
4.2.2.9
1,00
C
Nonsmokeless flare
610 mm (24 in)
Siting of flare
Flare sparing philosophy
a.
Sparing of flares or other means for vent gas disposal should be considered in the facilities
that cannot be shut down to allow for maintenance, inspection, and flare breakdown.
N
4.2.2.10
O
For design issues related to siting of flare system, refer to the siting of flare or atmospheric vent
stacks clause in GP 44-80.
Typically, sparing of the flare is considered if a flare system serves more than one
unit that can function independently.
Flare vendor should typically specify expected time between overhauls. This estimated
time should be based on operational requirements set by BP. Adequate provisions in
design and material selection to enable flare and flare critical components continuous
operation for a full and intermittent specified range of flare gas flows during this period
shall be provided.
D
O
b.
4.2.2.11
Flare testing
The decision on the acceptability of pneumatic testing should be made at an early
stage in the design and cannot be left until the flare is constructed. On many
construction sites, there is a great reluctance to perform such testing. Apart from
procurement difficulties, consideration needs to be given to selecting welding
consumables with good fracture toughness to guard against brittle fracture and give
additional confidence in the safety of pressure components during a pneumatic test.
a.
Computer simulation and modelling shall be performed during flare design phase to
minimise actual flare testing scope.
Page 21 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Computer simulation and modelling by flare vendor is sometimes the only available
tool to ensure that flare performance will be met. This is due to limitations and
practicality of performing the actual flare test either in the vendor test facility or in
the field.
Simulation and modelling typically include calculations of combustion conditions,
radiation rates, assisting media rates, mechanical integrity, and sometimes the
dispersion of the flue gases and flare gases for the case of flameout.
Ultimately, the flare vendor is responsible for the design, performance, and
reliability of the flare system and components provided.
Vendor testing
1.
Unless specified otherwise by the BP responsible engineer, vendor should typically
perform full or maximum flow testing using air and measuring the associated pressure
drop at its fabrication facility.
PY
b.
O
BP responsible engineer may grant exception for flow testing if a test is not feasible
due to complexity or size of particular flare system or if vendor testing facilities are
not equipped to perform such test.
If reduced flow testing is proposed, vendor shall clearly demonstrate scale up factors
to validate full flow flare capacity.
3.
Flare vendor shall typically demonstrate, either at its facility or onsite, other
guaranteed flare performance values, such as smokeless flare capacity or steam/assist
gas flowrates, system hydraulics, and radiation levels, by using test methods proposed
by the vendor and approved by the BP responsible engineer.
4.
Flare vendor should typically perform flushing, cold testing, and static testing of the
flare system that are provided within the vendor scope of supply.
5.
Testing should comply with GP 32-10 and GP 32-20.
6.
Flare vendor should provide all necessary special equipment and instruments required
for testing.
O
Flare vendor shall produce documentation for BP responsible engineer approval that
includes listing the precommissioning and commissioning activities to meet requirements
outlined in GP 32-20.
N
c.
T
C
2.
Spares
D
4.2.2.12
O
Vendors typically provide a “generic type” of documentation that usually does not
meet BP requirements. BP typically specifies additional requirements that may
include the attendance of specialist operators and service staff during the
precommissioning, commissioning, and onsite performance testing of the flare
system.
a.
Flare vendor shall submit spares lists and cost for spare parts in their proposal. Spares lists
should consider/contain the following as a minimum:
1.
Replacement for all gaskets for joints that have to be broken during construction or
after testing.
2.
One set of spares to cover the first overhaul.
3.
One complete pilot burner.
4.
One complete set of spare thermocouples or pilot flame detection alternative device,
if used.
5.
One of each type of equipment forming part of the ignition system.
Page 22 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
b.
6.
One set of spares for the smoke suppressant apportioning instrumentation.
7.
Spare flare burner (tip).
Purchase and storing of these spare components should be evaluated on economic grounds,
including an allowance for changeout time.
4.3
Process definition
4.3.1
Objective
Modify to Read
4.3.2
PY
Process data outlined in flare data sheets should provide a clear process definition for the flare
capacity and process stream characterisation information relevant to system performance and
mechanical design considerations.
Functional requirements
Modify to Read
In addition to functional system design requirements as defined in 4.2, complete
composition, range of temperature, and hydrocarbon characterisation information of the
process stream(s) shall be provided.
O
a.
T
C
Operating or pressure relieving cases can individually define various aspects of the
design (i.e., hydraulic capacity, ground level radiation, aeration requirement for the
defined smokeless capacity, requirement for dilution gas, design metal temperature,
and thermal expansion). Multiple cases, together with expected duration and
frequency, should be provided to allow the designer to determine which cases
control the design.
Flare gas flowrates.
Flare gas composition.
Molecular weight.
Flare gas temperature.
Frequency and duration of process streams discharging into flare system at any
one time.
Inherent restrictions imposed (e.g., allowable backpressure, solids deposition).
Depressuring flowrates, especially if depressuring is activated because of fire or
due to utilities failure that might cause all depressuring valves to open
simultaneously (all fail open depressuring valves).
Permit emissions and height requirements.
Climate conditions (arctic, desert, offshore, etc.).
Available plot.
Flare radiation and noise limits.
Ignition and flame monitoring requirements.
Mechanical requirements.
N





O
BP typically provides design basis and requirements for flare design for engineering
contractor and to flare vendor. Data will be specified in flare data sheets and may
include the following:
D
O


b.






The potential for liquid introduction, the condensation of hydrocarbons, or the formation of
hydrates in the flare header or flare riser that can be carried to the combustion zone shall be
considered by both BP and the flare designer. This functional requirement shall be
Page 23 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
evaluated based on criteria established by the relief system design and flare and
atmospheric vent - system design clauses in GP 44-80.
c.
Flare system knockout drum design and heat tracing systems downstream of the knockout
drum shall be designed in accordance with GP 44-80 to address potential problems with
liquids introduction into flare burner.
Hydrocarbon droplets entrained in the gas stream that are carried into the flame
usually burn incompletely, can produce burning liquid droplets, form soot, and
decrease the smokeless capacity of the flare. The maximum liquid droplet size that
can enter the combustion zone and can be handled within achievable measures for
smokeless control depends on the burner design.
Special design requirements should be specified in flare data sheets for flares in cold
service that are handling cryogenic fluids, such as in gas processing and LNG plants.
These requirements shall comply with the cold service clause in GP 44-80.
Types of flares
4.4.1
Objective
O
4.4
PY
d.
Modify to Read
C
Selection of the most appropriate type and configuration of a flare system shall be based on
given process and facility specifics outlined in the flare data sheets. The most economic type of
flare that meets all objectives outlined in the flare data sheets shall be selected.
T
The type of flare, as well as any design features required, will be based on many
factors, such as characteristics of the flare gas (i.e., composition, quantity, pressure
level), economics, including both initial investment and operating costs, availability
of space, and public relations.
O
A derrick supported stack is the most expensive to build and maintain. Usually, it is
a four sided derrick, but a three sided derrick has also been used. This type of stack
is normally selected for stacks above 61 m (200 ft) high and for locations where
flare is exposed to strong winds.
N
The self supported flare is a more economical design. However, the height of this
type of flare is limited, and wind can set up forces that can make the structure
oscillate rhythmically. Tapering the stack, using different diameters of riser pipe, or
welding wind spoilers on the outside can prevent this effect. The cost of this type is
higher than the guyed stack, but its appearance is better, and it is easier to maintain.
D
O
The guyed type of stack is very economical design. However, the main disadvantage
of this design is requirement to provide space for guyed cables and anchors.
Ground flares in the form of pit flare and open or enclosed flame multitip flare are
economical design for flares with large variation in process flows and are
commonly used where space is available.
Offshore facilities primarily use remotely located marine type of flare or flare
located in platform, typically a boom type flare.
Mobile enclosed flame flares are sometimes used while the main flare is being
repaired or modified, allowing the operating facility uninterrupted service. Major
flare vendors offer mobile enclosed flares in various capacities. These flares can be
rented either for use and operation by renter or could be provided on a “full
service” basis, which will be then operated by vendor for duration of the rental
agreement.
Refer to ISO 25457/API Std 537, Figure 1, for a general flare type selection guide.
Within each general type of flare, various alternatives and proprietary design
Page 24 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
aspects can exist. An understanding of alternatives and/or proprietary design
aspects can be obtained and evaluated using the flare data sheets in DS 22-200 and
instructions for their use in Annex D of this GP.
4.4.2
Functional requirements
Modify First Paragraph to Read
Flare selection and design shall be based on the following:
a.
Designer shall specify the most appropriate type of flare, configuration, and components to
comply with the safety, operability, and functional requirements in this GP, GP 44-80, and
ISO 25457/API Std 537.
PY
Refer to ISO 25457/API Std 537, Figure 1, for a general flare type selection guide.
Within each general type of flare, various alternatives and proprietary design
aspects can exist. An understanding of alternatives and/or proprietary design
aspects can be obtained and evaluated using the flare data sheets in Annex E and
instructions for their use in Annex D (located in ISO 25457/API Std 537 and this
GP).
O
Vendor may quote alternative type of flare and components selection if the change
would result in improved design over design specified by BP.
Complete understanding of the process, performance, and operability needs for the flare.
c.
Safety and well being of all personnel and objects in vicinity (both onsite and offsite)
under all conditions of flare operation.
d.
Inherent safety of flare system itself, especially with respect to the following:
C
b.
Flammable or explosive mixtures.
2.
Blockages or flow restrictions.
3.
Toxic components.
4.
Chemical reactions.
5.
Mechanical damage.
6.
Corrosion, erosion, and hydrogen embrittlement.
8.
O
Flare flame stability.
Security of pilot and main flare burner ignition.
Security of pilots (reliability, flame monitoring, automatic pilot reignition, etc.).
O
9.
N
7.
T
1.
10. Changeover to another flare.
Site and plant requirements (distance from unit to flare, additive effect of radiation from
multiple flare installation, potential for burning liquid droplets, etc.).
D
e.
f.
Consideration of the mechanical, operability, and maintenance implications for selected
flare system, including construction materials requirements for seawater environment,
corrosive products of combustion, high heat flame intensity, intermittent operation, and
multiple tips in close vicinity.
g.
Protection of flare system from damage by external events (e.g., fires).
1.
This functional requirement shall be evaluated based on criteria established by
GP 48-04 and the flare and atmospheric vent - system design clause in GP 44-80.
2.
Consideration should be given to such effects as potential damage from blast
overpressure, fire exposure, etc.
Page 25 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
h.
Consideration of the applicable legal and regulatory (i.e., operating permit requirements)
for selected flare system that may include destruction efficiency, smoking rate limits, flare
height, flame monitoring, and aviation lights.
i.
Flares in the U.S.
1.
Design and operation of flares in the U.S. shall comply with EPA regulations.
2.
EPA regulations were established to comply with provisions of the Clean Air Act
(CAA) and National Emission Standards for Hazardous Air Pollutants (NESHAP).
3.
Offshore facilities do not fall under jurisdiction of the EPA. These facilities are
regulated by the MMS.
The following applies to flares located within EPA jurisdiction:
General control device requirements applicable to flares in EPA 40 CFR Part 60.18,
issued as a final rule on January 21, 1986. These requirements are applicable to
control devices that comply with New Source Performance Standards (NSPS).
2.
Control device requirements of EPA 40 CFR Part 63.11, issued as a final rule on
March 16, 1994. These requirements are applicable to control devices that comply
with NESHAP issued under the authority of CAA amendments of 1990.
3.
Amendment to EPA 40 CFR Part 60 and EPA 40 CFR Part 63 existing specifications
to permit the use of hydrogen fuelled flares.
4.
Specifically, operating requirements from EPA 40 CFR 60.18(b) through
EPA 40 CFR 60.18(d) and EPA 40 CFR 63.11(b) shall apply to flare operating
conditions to comply with requirement that flares shall achieve VOC or volatile
hazardous air pollutants (HAP) destruction efficiency of 98% or higher.
5.
The regulations in 1. through 4. apply to flares combusting organic emission streams.
Current regulations do not permit use of flares not meeting specifications to satisfy
control requirements under the CAA.
O
T
C
O
1.
N
j.
PY
Flares located outside of the U.S. and not subject to any permit requirements or
local regulations could be designed and operated to comply with EPA, MMS
regulations, or any other applicable legal or regulatory requirements, if available,
that provide safe operation and economical design of flare system.
More details on specific flare design requirements are in 4.5.
O
There are flare applications that do not involve VOC control. Such flares are not
required to comply with regulations in j. but may still be subject to different
regulations.
6.
If local operating, legal, and regulatory requirements are not available, EPA design
regulations for all new flare applications should be followed.
GDP 3.6-0001 should be followed.
l.
Utilities availability and cost (steam, air, high pressure gas, electricity, etc.).
m.
Accessibility (marine flare, boom flare, site with multiple flares, multiple tips on common
stack, remote site location, etc.).
D
k.
Add
4.4.3
Additional functional requirements for specific types of flares
4.4.3.1
General
ISO 25457/API Std 537 provides mechanical detail requirements for two basic types
of flares, elevated and enclosed flame flares. ISO 25457 also provides, in
Page 26 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Annexes A, B, and C, a comprehensive overview of types of flares systems and flare
equipment components.
Clauses 4.4.3.2 through 4.4.3.6 provide additional BP requirements for flare types addressed in
ISO 25457/API Std 537 and flare types that are not included in that standard.
4.4.3.2
Elevated flares
Elevated or vertical flares generally fire flames in an upward direction. Sometimes,
it is necessary, such as in platform boom flares or onshore well test flares, that the
flame be directed away from the facility to reduce the flame radiation level and
reduce effects of potential liquid carryover.
PY
The simplest type of elevated flare typically uses a utility or pipe flare burner. The
burner consists of an open pipe type flue gas exit with a flame retention device for
flame stability and pilots for gas ignition. The elevated flare is well suited for smoke
control by using steam or air assisted type of flare burner.
C
O
Elevated flares have the best dispersion characteristics. Visual and noise pollution
can present public relations problems. Capital and operating costs are relatively
high, and a significant plan area may be required to mitigate radiation heat
concerns. Despite disadvantages, elevated flares are the most common installations
in onshore facilities. The height of a flare is determined by ground level limitations
of thermal radiation intensity, luminosity, noise, height of surrounding structures,
and dispersion of exhaust gases.
T
Typically, the elevated flare supports a single flare service. Sometimes, due to space
or other limitations, two or more services with dedicated tips are installed on a
single stack. For such installations, numerous issues need to be addressed and
considered, such as flame impingement from tip to tip, combined heat radiation
rates and noise, and difficulty in scheduling maintenance work.
O
Elevated flares can use a majority of types of flare burners that are currently being
offered by flare manufacturers. Flare burners that can be used include those that
use assisting media for smoke suppression, such as steam, air, and high pressure
gas, as well as multipoint tips.
N
Due to lower overall installation cost, the first choices in selection of elevated flares
are, if practical, either guy supported or self supported, unless special requirements
call for another type of flare.
The following are general requirements for elevated flares:
Typically, flare vendor providing the flare system shall confirm adequacy of height of flare
stack.
b.
Unless supported by dispersion modelling as described in GP 44-80, flare height of any
elevated flare type should be at least 7,6 m (25 ft).
D
O
a.
c.
This requirement is primarily set to provide adequate dispersion and protection
from flare radiation.
Shorter flare stacks can be considered, provided that flaring does not impose
excessive thermal radiation or other safety hazards to the vicinity.
Dispersion modelling
1.
Dispersion modelling, as described in GP 44-80, Annex A, shall be conducted to
evaluate “flame out”.
2.
Adequate dispersion of flammable and/or toxic gases with the flare extinguished or
dispersion of combustion products of flaring shall be necessary so that concentrations:
a)
Do not cause adverse impact to personnel.
Page 27 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
b)
3.
d.
Comply with legal and regulatory requirements.
Results of ground level and maintenance or operations access level dispersion
modelling shall be submitted for entity EA approval.
If two or more services with dedicated tips are installed on single stack, the following shall
be addressed:
1.
Flame impingement from burner to burner.
2.
Combined heat radiation rates and noise.
3.
Difficulty to schedule maintenance work.
Vendor supplying riser and flare support structure shall perform structural design
calculation as outlined in specifications.
f.
Flare structures shall be designed to withstand loads imposed by known environmental
conditions, such as wind, ice, and temperature, subject to BP specification.
g.
In addition to environmental loadings, structure shall be designed to withstand thrusts from
liquid slugs (if there is risk that these can occur), gas discharging from flare tips, and
imposed structural and equipment loads.
h.
Structure shall be designed for maintenance loads, such as supporting spare flare tip during
tip replacement, additional scaffolding, lifting beams, tools, and personnel.
i.
Structural plans indicating complete arrangement, including flare foundation requirements,
manner of reinforcements, ladders, and platforms, shall be provided.
j.
Structure shall be analysed for rhythmical oscillations. Adequate structural design shall be
ensured.
C
O
PY
e.
O
T
Wind can set up forces that can make the structure oscillate rhythmically. This can
be prevented by tapering the stack, using different diameters of pipe, or welding
wind spoilers on the outside. The cost of this flare type is higher than the guyed
stack, but its appearance is better and it is easier to maintain.
Guidelines or recommendations for transportation to site and for installation of stack shall
be provided.
l.
The following are specific requirements for self supported elevated flares:
N
k.
This type of flare is well suited for air assisted flare. In some cases, base of stack
can incorporate water seal drum.
Flare riser pipe shall provide structural support for all flare components.
O
1.
2.
The following are specific requirements for guyed stack elevated flares:
D
m.
This type of flare should be used for short and medium height flares, typically from
7,6 m to 30 m (25 ft to 100 ft), but can be designed for up to 76 m (250 ft), if
minimum ground area is available.
Guyed supported flare structure requires large plot area. If there is no room for guy
wires or concrete block foundations, use of derrick or self supporting type of flare
may need to be considered.
1.
Guyed stack should be used for heights up to 107 m (350 ft).
2.
To limit deflection of structure guyed stacks, design should use guy wires that are
attached to riser at one or more elevations.
3.
If more than four levels of guys are required to support stack, a derrick supported
structure should be proposed as an alternate.
Page 28 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Guy wires are typically positioned in triangular plan and shall be anchored by buried
concrete block foundations.
5.
If there is no room for guy wires or concrete block foundations, stack shall be
supported by derrick, or stack may be self supporting.
6.
Proposal for detail design of guyed structure shall outline all design scenarios to be
considered and shall include load types, load directions, and stack conditions for
design.
7.
Vendor shall list and recommend maintenance procedures, recommended frequency
for nondestructive testing (NDT), inspection, and special tools required, such as
hydraulic tensioners and lubricants required for guy ropes. This will allow proper
maintenance of guyed wire ropes, prevent corrosion, and extend flare and flare
component useful life span.
PY
n.
4.
The following are specific requirements for derrick supported elevated flares:
O
These types of flares are the most costly to build and maintain and could be selected
if other less costly types of flares cannot be used. This type of stack is normally
selected for stacks higher than 61 m (200 ft) and for locations where flare is exposed
to strong winds.
Usually, it is a four sided derrick, but a three sided derrick has also been used.
2.
Fixed derrick structure on offshore facilities shall have davit provision for tip removal
or maintenance.
C
Documentation to verify structural design and other general requirements for
transportation of structure to final site shall be provided by flare vendor.
Boom and tower mounted flares
T
4.4.3.3
1.
O
Boom and tower mounted flares are found on marine drilling and production
platforms. These flares use various standard flare burners designed for elevated
flares. Booms are typically projected out over the water at an angle from the
platform. The towers are located on the platform as far as possible from living
quarters and critical equipment.
N
Except for structural details, sizing of this type of flare is similar to an elevated flare
commonly used on onshore installations.
O
Boom and tower mounted flares should, if possible, be situated downwind of the
helicopter deck, drilling deck, and operating area of the platform. If a single boom
cannot be satisfactorily located, the use of two booms or one tower and one boom
should be considered, with the facility to switch over as wind conditions change.
D
In general, there is a HP flare, LP flare, and atmospheric vent on typical offshore
production platform flare system.
Heat radiation limits imposed by platform design criteria have important influence
on the flare boom length and overall cost of platform. Use of heat radiation
reduction options, such as inclined tip orientation, water injection and water
curtains, and radiation shields, may be cost effective solutions, resulting in boom
length reduction and significant savings in the overall platform cost.
The following are specific requirements for boom and tower mounted flares:
a.
Type of flare for offshore production platforms should be specified by BP on flare data
sheets.
Page 29 of 84
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Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
c.
d.
HP flare
1.
HP flare should typically use low radiation sonic type burner or other low radiation
type burner.
2.
HP flare should be used to dispose PSV discharges from vessels designed for
700 kPag (100 psig) maximum allowable working pressure (MAWP) or greater.
LP flare
1.
LP flare should typically use standard pipe flare burner.
2.
LP flare should be used to dispose PSV discharges from equipment less than
700 kPag (100 psig) but greater than 14 kPag (2 psig).
Atmospheric vents
1.
PY
b.
Atmospheric vent system design and its use on offshore production platforms shall
comply with the atmospheric discharge clause in GP 44-80.
O
Atmospheric vents are used to dispose low pressure streams, such as tank vents and
other low pressure equipment designed for operating pressure less than 14 kPag
(2 psig).
Atmospheric vents should typically use an unlit open end pipe termination.
3.
Atmospheric vent typically terminates midway up flare boom and should be pointed
away from boom structure.
4.
Atmospheric vents shall have flame snuffing system to prevent vents from burning (if
vents are accidentally ignited) that may result in flare boom structural damage.
5.
As a minimum, flame snuffing system should be sized to snuff flame caused by
residual gas flow to the vent once the primary gas flow to the vent is stopped.
T
C
2.
Sizing for full vent flow is often not practical.
In addition to radiation heat concerns, design of flare structure shall take into consideration
potential for and effect of liquid carryover and dispersion and location of hot gas plume.
f.
If several flare burners have to be sited in close proximity (i.e., HP and LP service) by
sharing same support structure, attention shall be given to potential for interactive thermal
damage to flare burners and maintenance of each flare burner.
g.
Maintenance and inspection
1.
N
O
e.
Access to flare burner(s) should usually be required for maintenance and inspection.
If used, maintenance platform shall be capable of withstanding heat produced by flare
flame and anticipated loads.
3.
If platform is not needed or provided, alternative method for access to flare burners(s)
should be provided.
D
O
2.
4.
Mechanical system should be provided to allow removal and replacement of flare
burner.
As an alternative to mechanical system, helicopter or barge based crane could be
effective but is costly to provide mechanical system for flare burners installation
and/or replacement.
h.
Except for instruments required to be located at flare tip, instruments shall be accessible
for testing, repair, and replacement without shutdown.
i.
The pilot system shall be reliable and capable of operating for the same estimated life
expectancy as the flare burner, because the pilots cannot be accessed for repairs or replaced
while the flare is in operation.
Page 30 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
j.
Dual ignition system, primary and backup, shall be provided for pilot ignition.
Typically, direct electrical automatic ignition as primary and a flame front
generator as a backup are used for pilot ignition.
Flame detection devices for monitoring pilot flames shall be provided. Flame failure shall
be alarmed locally and in the unit DCS.
l.
Automatic pilot reignition should be incorporated into the system design.
m.
Flare structure, riser, flare burner, and pilots shall be constructed of materials suitable for
exposure from both higher temperatures caused by flare flame radiation and exposure to
marine environment.
n.
Typically, materials for structure are specified in BP data sheets. If specified by others,
including the flare vendor, the material selection shall be approved by the BP responsible
engineer.
PY
k.
4.4.3.4
O
The proposed material alternative, if it is different from material selection outlined
in BP data sheets, will be accepted only if it can be shown to the satisfaction of BP
that it meets or exceeds requirements of material referenced in data sheets.
Marine flares/remote flares
C
These types of flares are primarily used in shallow water drilling and production
platforms.
T
There are numerous disadvantages associated with this type of installation, such as
additional cost of connecting piping, difficulties with use of ignition system, and cost
of constructing underwater foundations. These types of flares were used in the past
primarily for venting purposes rather than for flaring service.
a.
O
These facilities may be a bridge linked remote or a fully remote structure. Bridge
linked structures can be floating, fixed, or articulated. Fully remote structures can
be fixed or articulated.
Flare systems shall preferably be on the main platform.
N
This is due to the lower overall installation costs and ease of operation and
maintenance. Occasionally, but rarely, if conditions require, the flare system can be
located remotely from the main platform.
If amount of gas to be flared is so high that a flare system installed on the platform is not
practical or if local statutory regulations require, remote flare facilities shall be provided.
c.
Specific attention shall be given in the design of the system to include:
O
b.
Subsea equipment (lines and risers, knockout drum, etc.).
2.
Condensate removal methods.
3.
Maintenance and repair (no hoists or cranes permanently available).
4.
Provision to avoid liquid accumulation from carryover or vapour condensation or
seaspray into the flare line.
D
1.
d.
Location of bridge linked flare shall be chosen to avoid hot gas stream or unburned gas
that is carried by wind from affecting personnel and equipment on main platform.
e.
Fully remote flares should be used for HP flare only.
f.
LP flare pressure may be sufficient to allow mounting on bridge linked structure.
Otherwise, main platform should have facilities for LP flaring.
Page 31 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
4.4.3.5
Horizontal or pit flares
Horizontal low level open burn ground flare or pit flare is a simple construction,
with low capital and operating costs and capable of burning gas and liquid
hydrocarbon streams. Its use is primarily limited by local regulations, spacing
requirements, smoke formation, and the dispersion of combustion produced gases.
Depending on heat release, the minimum unobstructed distance surrounding a flare
may vary from 76 m to 152 m (250 ft to 500 ft). This type of flare is used primarily in
remote locations in drilling and completion and other facilities, if there are no
opacity restrictions, heat radiation concerns, and local legal and regulatory
requirements allow the use of this kind of disposal system.
Although this type of flare has been used in BP facilities, due to potential for negative
environmental impacts, such as flue gas dispersion and ground water contamination, their
future use shall be limited or completely eliminated. Horizontal flares may be required to
allow operation of temporary installations in remote locations, and their use is subject to
approval by the entity EA.
O
a.
PY
High maintenance cost, short tip life expectancy, and difficulties with pilot ignition
system can be expected in this type of flare in windy areas if liquids are frequently
being burned. Typically, a utility type of flare burner (an open pipe low pressure
type), with or without assisting media for smoke suppression, is used in pit flare
installations.
T
If horizontal flare is considered, the following general requirements for flare selection and
design shall be addressed:
Local legal and regulatory requirements.
2.
Spacing requirements.
3.
Smoke formation.
4.
Flare burner selection and life expectancy.
5.
Pilot ignition system selection and life expectancy.
6.
Need for use of assisting media for smoke control.
Dispersion of combustion produced gases
a)
Dispersion modelling as described in GP 44-80, Annex A shall be conducted to
evaluate dispersion of combustion products of flaring.
b)
Adequate dispersion is necessary to ensure concentrations do not cause any
adverse impact to personnel and comply with local regulations.
D
O
7.
O
1.
N
b.
C
The approval to use horizontal or pit flare can be granted only if an environmental
impact study is completed and all provisions to minimise impact on the environment,
as determined by the study, are implemented.
8.
9.
c.
Dispersion of unburned gases due to flame failure
a)
Dispersion modelling as described in GP 44-80, Annex A shall be conducted to
evaluate “flame out”.
b)
Adequate dispersion of flammable and/or toxic gases with the flare extinguished
shall not result in ground concentrations that cause any adverse impact to
personnel and shall comply with local regulations.
Results of dispersion modelling as outlined in 7. and 8. (including ground level
concentrations to which operations or maintenance personnel could be exposed) shall
be submitted for entity EA approval.
Flare lines leading to pit flare shall not be buried.
Page 32 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Flare header layout is an important design consideration. Radiation heat effect may
cause overheating of buried header piping, resulting in a rupture type failure.
Experience has shown that a flare line leading to pit flare presents no problem from
flame radiation. The flow through lines provides sufficient cooling effect and lines
remain cool. If the lines are buried for protection from radiation, the fill above the
line may reach a high temperature during prolonged heavy flaring. If flow stops, it
will heat the pipe, which will expand and may lift out of the ground. Better options
for piping protection are use of heat shields or adequate height of berm. The typical
height of berms is 1,2 m to 1,8 m (4 ft to 6 ft). The berms are installed in all four
sides of a squared shape burn basin. The basin is either excavated or a diked area.
The following design enhancement options should be considered in existing and/or new pit
flare design:
1.
PY
d.
Flare burner location: Flare burner should be installed on upwind side of prevailing
wind direction to carry flame away from flare tip.
Burner protection from heat: Use of some type of additional burner protection from
heat or burning flash fires caused by presence of liquids should be considered.
Options may include selection of higher metallurgy for burner components, refractory
protection of components exposed to direct heat, and use of heat shields.
3.
Use of retractable pilot(s): Retractable pilot(s) can significantly increase flare
operational safety, reliability, and availability by allowing on stream pilot
repairs/replacement.
4.
Use of multiple burners and/or multiple stage design: This design should provide
improved distribution of combustion gas over a wider area and minimise smoke and
radiant heat.
T
C
2.
Ground flares
O
4.4.3.6
O
These flares are typically operated at low flare burner pressure. Gas exit velocities
are low, allowing wind at lower release rates to blow air inside of burner, causing
internal combustion and premature flare burner mechanical failure.
N
Ground flares have three basic configurations:



Enclosed flame flare.
Ground flares with radiation shield.
Ground flares with access limiting fence.
D
O
All three types may also be termed as multipoint flares.
Enclosed flame flares and flares with radiation shields offer the advantages of
having large smokeless capacity, hiding flames, reduced combustion related
emissions, lower flame radiation rates, and lower noise.
Ground flares with fences for restricting unauthorised to access to flare are
typically used in facilities in which sufficient plot space is available and radiation
and noise limits are not required. These types of flares also provide smokeless
operation.
For large footprints, ground flares wind effects can be significant as flow separation
occurs over the enclosure fence creating a down draught in the centre. This can lead
to internal burning within runners causing overheating and risers and tips damage.
It is recommended that CFD modelling be conducted for large flares to ensure that
these effects are identified and addressed in design.
Enclosed flame ground flares provide stable combustion, due to isolation from wind
effects, and have ability to provide controlled conditions in the combustion zone.
Page 33 of 84
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Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Therefore, higher thermal destruction efficiency can be achieved. Also, complete
combustion can be achieved with lower calorific value vent gases than is possible
with open flame flare designs. This type of flare is desirable if high destruction
efficiency is required and local regulations require continuous monitoring of
destruction efficiency performance. The enclosed flame flare system is
disadvantageous because of capacity limitations, high capital cost, and high
maintenance requirements.
Refer to later clauses of this GP and ISO 25457/API Std 537 for further details on
mechanical design, operation, and maintenance of enclosed flame ground flares.
4.4.3.6.1
Ground flares general design requirements
PY
BP or its representative will typically propose use and type of ground flare for
particular application. However, vendor may propose alternate type of ground flare,
subject to BP review and approval. Use of the alternative design may be approved
by BP only if it can be shown to the satisfaction of BP that required performance
and function are attained.
O
The following are general design requirements that are common for all three types of ground
flares:
Multipoint ground flares should use staged design to allow a wide range in flare loads (i.e.,
high turndown rates).
b.
Care shall be taken if specifying the turndown ratio for each stage to avoid possible stage
run conditions below and above design rates.
c.
The exit area of ground flares shall provide adequate dispersion of all combustion products
exiting the flare.
T
C
a.
A significant disadvantage of ground flares is the flare gas is released near grade
level in the event of a flameout and flare ignition system failure.
O
Dispersion and consequence analyses shall be performed to evaluate potential impact due
to release of unburned flare gases in the event of ground flare ignition system failure and
the effects of delayed ignition. Dispersion and consequence analysis shall comply with
GP 44-80, Annex A that discusses dispersion modelling methodology for atmospheric vent
and flare systems.
N
d.
Typically, the temperature factor dominates for the dispersion of combustion
products.
D
O
Since the flame is near ground level, dispersion of flare gases may result in severe
air pollution or hazard if the combustion products are toxic or if there is flameout.
Partial flameout can occur delaying the ignition of released gases. During the time
delay until the flame or pilot of neighbouring runners ignites the released gases, a
temporary local vapour cloud and pressure surge within the enclosure can result.
The hot plume from the ground flare can impinge upon structures and components
that are nearby and above the elevation of the combustion zone discharge.
e.
Installations located in well used areas or close to public facilities shall be surrounded by
plenum or radiation fence. Plenum height and radiation shields shall be specified and
provided to completely hide the flames throughout entire flare operating rates.
f.
Height of fence shall be determined by specific shielding requirements for each particular
installation.
g.
Plenum and radiation shield design shall accommodate proper flare combustion air
requirements and air distribution within the flare stages.
Page 34 of 84
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Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Cold flow and/or CFD modelling may need to be performed to confirm that air
supply and distribution is adequate.
Radiation shielding may be limited to stage manifold area or may be required
around entire area.
Radiation fence is normally approximately 3,7 m (12 ft) high.
h.
Division of burners into zones and stages.
The following are operational, design, and functional requirements for ground flare
staging:
Operating cases should be clearly defined. Design shall account for operating
conditions outside of normal operating conditions, such as initial plant commissioning
and flare testing.
2.
Minimum turndown for each stage shall be determined to avoid potential burnback
inside the flare piping that may occur if the flare load drops below the minimum.
3.
Gas flow to flare stages shall be controlled by main control logic housed in control
panel enclosure that is usually located near staging manifold or integrated into plant
control system.
O
1.
C
i.
PY
Ground flares are typically based on use of zone or staged flare gas operation. Each
zone or stage activates sequentially into operation, providing greater turndown. The
flare zones and stages are normally arranged in a pattern intended to allow
adequate ingress of combustion air to ensure smokeless operation.
T
Control logic usually operates by sensing backpressure in the flare system and
subsequently opening control valves in the inlets to various stages according to
demand. The control logic also effectively closes stages at the end of a flare event to
minimise smoke from larger stages.
Control shall operate automatically without human intervention and may be by means
of valves.
5.
If valves are used, liquid seals, rupture disks, or pin valves shall be installed in
parallel for each stage to retain full flaring capacity and header protection from
overpressure in event of primary control system failure.
N
O
4.
Buoyancy and velocity seals are typically not applicable to multiburner staged
flares.
Purge gas rates shall be properly selected for types of flares that use flow staging to avoid
flashback and internal burning due to air egress into the flare burners, risers, and headers.
O
j.
D
Lower than required purge rates, possibly caused by leaking staging valves, is of
great concern. Internal combustion and detonations can quickly deteriorate a stage
if left unchecked.
At low flowrates, only the first stage of a multitip array will normally be open to the
atmosphere, and this stage is the only one that needs to be included in the
continuous purge rate calculations. As a result, a substantial purge gas savings may
be possible for a large capacity multiple stage flare as compared to a similar
conventional flare tip. It is important that proper purge gas rates are maintained at
all times in the first stage.
For ground flares, if the purge gas flow is not sufficient, exit velocities may become
lower than flame velocity and flames could be “pulled” inside of risers. The most
common occurrence in this case is that part of the tips will maintain the flames on
the tips, creating increased buoyancy in that section. As a consequence, less purge
gas will be available for the remaining tips, causing internal combustion in raisers
and potentially causing significant damage to the raiser and header over time. The
Page 35 of 84
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Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
same problem (low flow condition) can occur if the control valves in one or more
stages develop a leak and pilots ignite leaking gas. If that occurs, the second and
higher stages may require addition of purge gas to avoid internal combustion.
In addition to complying with requirements for purge gas system design as described in
GP 44-80, the following are additional requirements that are specific for this type of flare:
1.
Provision for purge gas addition shall be provided for all stages.
2.
The system shall be capable of delivering sufficient amount of purge gas for all flare
stages being in service simultaneously.
3.
Either continuous purge in all stages during flare operation or stage valve leak
detection shall be required.
PY
k.
The various methods for valve leak detection may be used (i.e., valve position
feedback, flare operation visual observation to detect presence of flame, sample
point located downstream of control valve, etc.).
The pilot system shall be reliable and capable of operating for the same estimated life
expectancy as the flare burner, because pilots cannot be accessed for repairs or replaced
while the flare is in operation.
O
l.
Direct electric ignition (as primary source of ignition) and a flame front generator
(as a backup) are typically used for pilot ignition.
Each flare stage shall have pilot burners to maintain stable source of ignition for
discharged gases. At least two pilots per stage shall be provided.
C
m.
T
If a flare pilot fails to ignite a particular stage in proper sequence, subsequent
stages can be prevented from operating properly. Releasing the unburned gas and
subsequently igniting this gas by adjacent working stage burners may cause very
hazardous conditions with possibility of explosion inside of ground flare enclosure
affecting the surrounding flare area.
N
O
Precise number of pilots and pilot locations is determined based on layout of
burners, numbers of stages used, and climate conditions (wind direction, ambient
temperature, etc.). If only two pilots are installed per stage, a preferred location for
pilots is one on the first and one on the last burner or on first and third burners. By
spacing pilots in these patterns, influence of unfavourable wind directions is
reduced and failure of one pilot on stream allows stage to be reliably ignited.
However, flare vendor needs to be consulted for the exact pilot locations and
number of pilots required for particular application.
Flame detection devices for monitoring pilot flames shall be provided. The flame failure
shall be alarmed locally and in the unit DCS.
o.
Automatic pilot reignition should be incorporated into the system design.
D
O
n.
p.
Purge or sweep gas should be used after ground flame flare system shutdown.
q.
For relief gas compositions with a wide ratio of upper to lower flammability limit, an inert
gas post purge of a burner stage as it turns off shall be required. Gases of concern include
hydrogen, ethylene, acetylene, and others, as defined by a high ratio of upper to lower
flammability limits.
The post purge sweeps the reactive gas out of the burners and burner piping and
mitigates flashback and combustion in the flare system piping.
r.
Potential noise produced by ground flare shall be addressed in design. The following are
ground flare noise requirements:
1.
Noise emission from flare shall be set at maximum emergency flow and at maximum
smokeless flaring rate.
Page 36 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
2.
Noise levels shall comply with general requirements in flare data sheets and comply
with allowable levels in GP 15-01 for normally manned areas or public exposure.
The noise levels produced by ground flares may not be a problem in isolated areas
and from flares that use shields because flames are somewhat enclosed within shield
walls.
The flare is typically sited such that it is not in direct line of sight and noise at
positions normally accessible to personnel, at maximum emergency flow, does not
exceed 115 dB(A). Lower noise limits are sometimes applied in a particular
application.
The following is a list of typical design information that needs to be provided by ground
flare vendor:
1.
Performance guaranteed to comply with all operating conditions specified in flare
data sheets.
2.
Guarantee that waste stream is continuously ignited and explain how proposed flare
design will achieve this requirement.
O
s.
Noise emission level shall be controlled on sound-power levels in octave bands from
31 Hz to 8 kHz.
PY
3.
Guarantee maximum emissions limits.
4.
Guarantee the noise level produced by proposed ground flare design and that design
complies with noise emissions limits set by flare data sheets.
5.
Provide purge gas requirements and estimate of service life of burners at normal and
at minimum purge rates.
6.
Identify, at early stage of project, ground flare maintenance requirements and outline
maintenance procedures, provide estimates for annual cost, and list all special tools
and spare parts requirements.
O
T
3.
Enclosed flame ground flare general design requirements
N
4.4.3.6.2
C
If vent stream to be burned is low BTU gas, it is important to have stable and
complete combustion, especially if toxic gases are present.
There are circumstances when it is desirable that all or part of a flare load be
disposed of in a way that causes the minimum of disturbance to the immediate
locality, such as:
To eliminate or reduce radiant heat to nearby equipment or work areas.
To reduce noise in the immediate vicinity.
To make the flare flame less obvious for community relations.
To potentially achieve improved emissions.
To burn flare gases that are difficult to burn in open flame environment.
D
O





Typical applications for enclosed flame flares are:


In refining and petrochemical applications in which the flare acts as a lower
stage to the complete relief system, designed to handle “day to day” or
“routine” flaring, such as startup/shutdown flows and normal process
venting/flaring.
Landfill biogas disposal. The products of anaerobic digestion (e.g., from
landfills, industrial digestion processes, or sewage processing) that are fed at a
fairly steady and predictable rate.
Page 37 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Truck, barge, and marine vessel vapour disposal from loading operations and
petroleum terminal vapour control.
 Onboard FPSO vessels, in which the bulk of flaring events are handled in a safe
way in the confined space of enclosed flare, to minimise impact on operating
personnel and reduction of VOC emissions.
 Flare applications for which the assist fuel gas quantity can be reduced by use
of an enclosed flame.
 Flare applications in environmentally sensitive area where operating permit
requires combustion chamber to be operated at high temperature to achieve
high destruction efficiency.
In addition to requirements in ISO 25457/API Std 537, application and design of an enclosed
flame flare type shall be subject to the following additional BP requirements:
Due to high capital and operating costs and relatively small capacity as compared to other
types of flares, use of enclosed flame type of ground flare should be considered only if it is
desirable that all or part of a flare load be disposed of in a way which causes minimum
disturbance to the immediate locality and achieves high destruction efficiency that is
imposed by operating permit.
O
a.
PY

C
Mobile enclosed flame flares are sometimes used while the main flare is being
repaired or modified, allowing the operating facility uninterrupted service. Major
flare vendors offer mobile enclosed flares in various capacities. These flares can be
rented either for use and operation by renter or may be provided on a “full service”
basis, which will be then operated by vendor for duration of the rental agreement.
If enclosed flame flare is used for routine and reduced capacity flaring, an auxiliary
elevated flare shall be provided and used for emergency flaring to provide supplemental
capacity to enclosed flare.
c.
Flow of gas through the burner, the flow of air into the combustion chamber, and the flow
of flue gases out of the combustion chamber shall be engineered to comply with all
requirements listed in flare data sheets.
d.
Combustion chamber size and shape design should address the following:
2.
Enclosed flame flare chamber shall be designed to operate at temperature sufficient to
allow complete combustion of all incoming gases and hydrocarbon fuels.
N
1.
O
T
b.
Required chamber temperature and residence time shall be provided by enclosed
flame flare vendor and shall be subject to approval by the BP responsible engineer.
D
O
Enclosed flame flare vendors use their proprietary design methods to determine the
optimum values of chamber temperature and residence time. It is normally required
that the vendor provides the design basis and design results for review and approval
before the design is finalised.
3.
Required residence time and combustion temperature values are selected primarily
based on flare gas composition and required thermal destruction efficiency.
Therefore, each application is somewhat unique. Those two variables are closely
interrelated, and correct design is always based on selection of optimum ratio
between the two values. Typically, lower combustion temperature requires longer
residence time, and vice versa. For example, low Btu value flare gases would
require addition of supplementary fuel to support combustion. Therefore, fuel gas
savings can be achieved by lowering the combustion temperature and increasing the
residence time. As a consequence, larger combustion chamber would be required in
this application.
Combustion of waste gases shall be completed within combustion chamber without
any flames issuing from flare stack.
Page 38 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Due to ionisation, flue gas temperature in excess of 980°C (1 800°F) can produce
visible emissions that are not actually flames.
e.
Enclosed flame flare combustion chamber should be typically designed for a volumetric
heat release of approximately 1 120 MJ/m3 (30 000 Btu/hr/ft3). Any deviation from this
value shall be subject to approval by the BP responsible engineer.
Deviation from this requirement may be acceptable, subject to BP approval, if it can
be shown to the satisfaction of BP that required performance and function are
attained.
Plenum height
1.
Plenum height shall be specified and provided to avoid wind causing downdrafts that
force flames outside bottom of enclosed flame flare.
2.
Plenum height is typically specified by flare vendor and shall be subject to approval
by the BP responsible engineer.
O
f.
PY
Design volumetric heat release selection is primarily influenced by the number of
burners, burner size and design, combustion chamber geometry dictated by
combustion temperature and residence time, and relief gas composition.
Height of the plenum shall be determined by specific shielding requirements for each
particular installation.
4.
Wall or fence to cut off direct route for light and noise to immediate surroundings
may need to be added to shell to screen air inlet at bottom of the plenum.
O
Gas flow control requirements
1.
If fuel gas staging is used, gas flow to flare stages shall be controlled by main control
logic housed in control panel enclosure that is usually located near staging manifold.
2.
Control logic shall be integrated into plant control system.
3.
For control valve(s) or control system malfunctions, rupture disk or pin valve bypass
lines shall be installed for each stage as header protection from overpressure.
Purge gas system shall be carefully selected and for the types of flares that use flow
staging to address the following:
O
h.
T
3.
N
g.
C
Flare vendor will specify the plenum height in the proposal unless the plenum height
requirement is specified in BP data sheets. The height value proposed by the vendor
is based on vendor proprietary design method. BP normally requires that the vendor
provide design basis and design results for review and approval before the design is
finalised.
Proper purge gas rates shall be maintained at all times in an active stage to avoid
internal combustion in raisers and header.
D
1.
2.
3.
At low flowrates, only first stage of multitip array should be open to atmosphere, and
this stage is only one that needs to be included in continuous purge rate calculations.
As is typical for staged burner systems, only the first stage would require purge gas
flow. Some smaller enclosed flame flares eliminate purge gas flows by opening and
closing the first stage burners to maintain minimum pressure in the flare header.
Provisions for adding purge gas in all stages shall be provided to avoid internal
combustion if control valve in one or more stages develops a leak. Adequate purge
system capacity shall be provided to meet this requirement.
i.
Purge or sweep gas should be used after enclosed flame flare system shutdown.
j.
For relief gas compositions with a wide ratio of upper to lower flammability limit, an inert
gas post purge of a burner stage as it turns off shall be required. Gases of concern include
Page 39 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
hydrogen, ethylene, acetylene, and others, as defined by a high ratio of upper to lower
flammability limits.
The post purge sweeps the reactive gas out of the burners and burner piping, and
mitigates flashback and combustion in the flare system piping.
k.
The pilot system shall be reliable enough to operate without maintenance until the flare
receives scheduled maintenance (typically many years), because the pilots cannot be
accessed for repairs or replaced while the flare is in operation.
l.
A proper number of pilot burners shall be provided on the flare to maintain stable source of
ignition for discharged gases. At least one pilot per stage shall be provided.
PY
The combustion chamber in an enclosed flare provides a somewhat controlled
environment and enables easier stage ignition from a neighbouring lit stage within
the enclosed combustion chamber.
Typically, the required number of pilots is determined based on layout of burners
and number of stages used in the particular application and is proposed by flare
vendor for specific application.
C
O
If a flare pilot fails to ignite a particular stage in proper sequence, subsequent
stages, under certain operating conditions, can be prevented from operating and
may cause very hazardous conditions within the enclosed flare chamber and
surrounding flare area.
Direct electric ignition and a flame front generator, as a backup, shall be used for pilot
ignition.
n.
Flame detection devices for monitoring main flames shall be provided.
o.
Flame failure shall be alarmed locally and in the unit DCS.
p.
Pilot flame detection shall be incorporated into the system design.
r.
Automatic pilot reignition should be incorporated into the system design.
Flare burners
4.5.1
Objective
N
4.5
O
T
m.
Modify to Read
Flare burner design shall comply with all objectives identified as being critical attributes for
flare performance as defined in the flare data sheets.
Functional requirements
O
4.5.2
Modify First Paragraph to Read
A flare burner supplied in accordance with this GP and ISO 25457/API Std 537 shall
perform as specified under the defined service conditions for at least 5 yr, if installed and
operated in accordance with manufacturer recommendations.
b.
Although many design alternatives for flare burners exist, including those of a proprietary
nature, the minimum life expectancy and functional requirements shall be as outlined in
this GP.
D
a.
The type of flare and configuration is primarily established through consideration
and application of the procedures, practices, and recommendations of this GP and
ISO 25457/API Std 537. The most critical mechanical component integral to all
flare types is the flare burner and burner components, with which all aspects of safe,
reliable, and efficient discharge and combustion of relief gases from the flare system
Page 40 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
are associated. The integrity and reliability of the flare burner has a direct effect on
the operability and run length between maintenance intervals for the facility.
Add
In addition to requirements outlined in ISO 25457/API Std 537, the following shall be taken
into account in the design and selection of flare burners:
All flare burners
For plant design, the full range of relief gas compositions and flare burner exit
velocities shall be engineered to operate successfully with the size of selected flare
burner.
2.
Design exit velocity and minimum heat content of flaring gas shall comply with
applicable legal and regulatory requirements (typically contained in flare operating
permit requirements) as outlined in flare data sheets.
3.
For elevated flares located in the U.S., exit velocity requirement and minimum heat
content of flare gas shall comply with EPA 40 CFR 60.18 and EPA 40 CFR 63.11.
Both these standards were amended May 4, 1998, to allow different requirements for
flares disposing gas with hydrogen content greater than 8%.
4.
For elevated flares located outside U.S., the local legal and regulatory requirements
for exit velocity and minimum heat requirements shall be followed. If local operating
permit requirements or regulations are not available, the following regulations for
new flare applications shall be observed:
C
O
PY
1.
a)
EPA for onshore facilities.
b)
MMS.
c)
Any other requirements that provide safe and environmentally acceptable flare
design and performance.
T
a.
Flare burner diameter at least 75 mm (3 in).
Nonassisted type burner.
Designed for and operated with an exit velocity less than 37,2 m/s (122 ft/s).
Velocity calculation method is in EPA 40 CFR 63.11, paragraph (i)(A).
N



O
In accordance with requirements outlined in EPA regulations, the user may adhere
to either the heat content specifications in paragraph (c)(3)(ii) and maximum tip
velocity specifications in paragraph (c)(4) or the following requirements for flares
that are disposing gas with hydrogen content 8% or greater:
O
The following are typical EPA design requirements for exit velocity and minimum
heat content for various flare burners applications in elevated flares:
D




Air and steam assisted flares may be used only with net heating value of the gas
being combusted as 11,2 MJ/scm (300 Btu/scf) or greater.
Unassisted flares may be used only with net heating value of the gas being
combusted as 7,45 MJ/scm (200 Btu/scf) or greater.
Steam assisted and nonassisted flare exit velocities are limited to 18,3 m/s
(60 ft/s).
Allowable air assisted flare exit velocity is a calculated value rather than fixed
value. EPA provides the following formula to determine exit velocity for air
assisted flares:
Vmax = 8,71 + 0,708(HT)
Where:
Vmax = Maximum permitted velocity, m/s
Page 41 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
8,71 and 0,708 are constants
HT = Net heating value as determined by EPA methodology in
EPA 40 CFR 63.11, paragraph (b)(6)(ii).
5.
Flare vendor shall submit the calculated flare tip velocity over the given range of flare
operability to the Project EA for approval. The maximum velocity shall be selected to
satisfy requirements for flame stability, noise, and dispersion.
PY
The latest designs of pipe flare tips permit smokeless flaring at velocities greater
than Mach 0,2. If this velocity is exceeded, experience of satisfactory operation of
the design should be examined. For emergency flaring, Mach 0,5 is generally
accepted as a maximum for pipe flares. Above that figure, the flame could become
unstable and lift off, resulting in the risk of flame instability for pipe flares. High
pressure flares are available in which the flame is stable even at Mach 1,0.
However, a detailed design review of the vendor proposal should be conducted.
Flare burners shall be designed for minimum maintenance. Object is that no
maintenance should be needed between regular scheduled unit shutdowns.
7.
Flare burners shall have flame retention devices or aerodynamic methods with proven
capability to provide stable combustion and protection from flame blowoff.
8.
Air or steam injection, if applied for smoke rate reduction, shall not disrupt the basic
flame stabilisation mechanisms of the flare burner.
9.
Flare burners, in combination with their system of pilot(s)/ignition system(s), shall be
capable of maintaining stable combustion of the main flame for the specified service
conditions, including environmental conditions for pilots as specified in this GP and
ISO 25457/API Std 537.
C
O
6.
T
10. Minimum flow to internal parts of tip shall be maintained during flaring to provide
adequate internal cooling and eliminate potential for internal burning.
O
11. Flare burner should be designed to withstand effects of such internal and attached
external burning.
N
12. Windshields should be used on pipe flares to help mitigate wind induced attachment
of flames to the external flare burner surfaces.
O
Wind action at low flaring rates can produce internal burning and/or external
flames that remain attached to the flare burner. On larger flare burners, internal
refractory linings are sometimes used to mitigate the thermal effects of internal
burning. Refractory linings reduce high thermal gradients that produce buckling in
flare burners. Buckling of the flare burner is the first sign of almost all flare burner
failures.
Flare burners with internal steam injection to induce air
1.
Steam condensate shall be drained from the internal steam/air injection point and
from any muffler surrounding these tube assemblies.
2.
Air tube inlet should be venturi type.
3.
Internal steam tubes should be designed as pipe in accordance with piping
specification requirements.
4.
Steam tubes should be reinforced at exit. High alloy casting materials are preferred
for these reinforcements.
5.
Steam tubes should be internally supported to prevent failure from vibration.
6.
Noise mufflers should be used for noise control. Ceramic fibre insulation material is
preferred.
D
b.
Page 42 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
c.
If supersonic steam tips are used, potential increase in noise level shall be addressed.
4.6
Mechanical design
4.6.1
Objective
Modify to Read
Mechanical requirements for the design, fabrication, inspection, and testing of the flare
components shall comply with this GP and ISO 25457/API Std 537.
4.6.2
Functional requirements
PY
Modify through Third Paragraph after d) to Read
There are numerous physical arrangements and mechanical designs available from which
the most appropriate for the application can be selected.
b.
Mechanical design shall comply with the local codes and regulations and the plant
conditions and requirements outlined in the flare data sheets.
c.
Whichever selection is made, the following shall apply:
O
a.
Pressure components shall comply with the applicable pressure design code and
supplemental requirements in this GP and ISO 25457/API Std 537.
2.
Mechanical design codes shall be specified or agreed by the BP responsible engineer.
C
1.
T
Specified standards may be replaced by equivalent standards that are
internationally or otherwise recognised, subject to BP approval, if it can be shown
to the satisfaction of BP that they meet or exceed requirements of referenced
standards.
Structural components shall comply with the applicable structural design code and
supplemental requirements in this GP and ISO 25457/API Std 537.
4.
BP or BP E&C contractor and the vendor shall mutually determine the measures
required to comply with any local or national regulations applicable to the equipment.
5.
If the flare mechanical design involves pressure and structural design codes (e.g., self
supported or guyed flares), the more severe shall govern.
N
BP or BP E&C contractor shall specify the design temperature and design pressure.
For the design wind case, a credible metal temperature under design wind conditions
shall be established, listed on the flare data sheet, and used in the design. For
insulated or shielded flare risers, design temperature and wind loads shall be
considered to apply simultaneously.
D
O
6.
O
3.
7.
For uninsulated flare risers, it is not necessary to consider that the maximum design
temperature and wind loads apply simultaneously because of the cooling effect of
the wind.
Further guidance on metal temperature considerations is in ISO 25457/API Std 537,
section D.3.3, Form Elev 4.
Add to End of 4.6.2
In addition to requirements in ISO 25457/API Std 537, the following shall be taken into account
in the mechanical design:
a.
Typical operating and range of operating conditions shall be fully considered in deriving
mechanical design.
b.
Protection of flare system from damage by external events (fires, explosions, etc.).
Page 43 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
c.
Burner and burner component life expectancy, as a minimum, shall be selected to provide
uninterrupted operation between typical scheduled shutdown events.
d.
If possible, flame burner components metal temperature should be controlled below 482°C
(900°F).
e.
As a minimum, flare burner shall be constructed of materials specified in flare data sheets.
f.
The following are general requirements related to material selection:
Flare burner design and materials selection shall minimise potential damage to burner
and ancillaries due to high temperature, erosion, and corrosion.
2.
Materials for burner and related components shall be subject to approval by the BP
responsible engineer.
PY
1.
Alternative materials for flare components provided by flare vendor may be
acceptable, subject to BP approval, if it can be shown to satisfaction of BP that
required performance, functions, and durations are attained.
Material selection should take into consideration special issues associated with
potential autorefrigeration from depressuring.
4.
Selected materials shall not embrittle or lose critical physical properties under
anticipated operating conditions.
5.
Selected flare burner materials shall be suitable to survive flame lick and thermal
cycling.
6.
Unless approved otherwise, minimum material grade for flare burner shall be
type 310S SS for upper 3 m (10 ft).
C
O
3.
Unless otherwise specified in data sheets, materials for flare burner flanged joint and
remainder of flare burner body lower than 3 m (10 ft) may be carbon steel but shall be
compatible with flaring stream (corrosion, cryogenic, etc.).
N
7.
O
T
Vendor may propose use of alternative material to 310 SS for part of the flare tips or
flare components. Alternative materials to 310 SS material may be acceptable,
subject to BP approval, if it can be shown to satisfaction of BP that required
performance and function is attained by use of alternative materials.
The most frequently used materials for flare tips, in order of increasing cost, are
310 SS, Alloy 800H, 330 SS, and Inconel 625.
O
The “step up” of the grade is typically required to address specific flare burner
operating conditions, such as high flame temperature, climate conditions, and
corrosive nature of flare gas.
If flare gases are expected to contain H2S, nickel based alloys should be avoided, or
some protective material should be installed to prevent high temperature corrosion in
this environment.
D
8.
g.
h.
For flare burners with internal steam injection to induce air:
1.
Internal steam tubes should be designed as pipe in accordance with piping
specification requirements.
2.
Steam tubes should be reinforced at exit. High alloy casting materials are preferred
for these reinforcements.
3.
Steam tubes should be internally supported to prevent failure from vibration.
For internal refractory in flare tips:
1.
If damaging burnback inside tip cannot be prevented or is anticipated, internal
refractory lining of tip should be considered.
Page 44 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Flare burners experience rapid changes in temperature. Internal refractory should
be well anchored, and the refractory material should include stainless steel metal
needles to help hold it in place.
2.
Refractory design and procurement shall comply with GP 72-00, GIS 72-001,
GIS 72-002, and GIS 72-003.
3.
Type of refractory selected by flare vendor and method of application shall be subject
to approval by the BP responsible engineer.
PY
Material selection and method of application offered by flare vendor that differ from
requirements set by GP 72-00, GIS 72-001, GIS 72-002, and GIS 72-003 may be
acceptable, subject to BP approval, if it can be shown to the satisfaction of BP that
required performance and function of proposed refractory system is attained.
Refractory curing should be performed in flare vendor shop, in which much better
curing conditions can be achieved.
5.
As an alternative to use of refractory, a higher grade of metallurgy for tip material
should be considered.
4.7
Pilots
4.7.1
Objective
O
4.
C
Modify to Read
Pilot shall reliably light the flare burner and maintain stable combustion throughout the full
range of process conditions and under severe weather conditions.
b.
Pilots shall be reliable and capable of operating for the same estimated life expectancy as
the flare burner, because the pilots cannot be accessed for repairs or replaced while the
flare is in operation.
T
a.
N
O
If there is a long history of pilot malfunctions that are not attributed to poor pilot
design or selection or if periods between scheduled flare outages are too long, use
of retractable pilot(s) could be considered. Retractable pilot(s) can also be used in
flare applications in which loss of pilot flames, real loss of flame, or loss of signal
that confirms flame presence are a violation of operating permit.
The retractable pilots are typically flare vendor proprietary designs and design
features need to be reviewed if retractable application is considered.
c.
Due to their complexity, use of compressed air premix pilots should be limited.
D
O
Forced draft pilots are better suited for harsh environments. However, forced draft
pilot systems require additional piping, controls, and reliable air supply that make
them more complex to install and maintain in operation. Control of air and pilot gas
pressures are required to maintain air to pilot gas ratio within combustible limits.
4.7.2
Functional requirements
Modify to Read
Numerous pilot designs are available from which to select the most appropriate for the
application. Although design alternatives exist, the following are the functional requirements
that shall be met:
a.
Pilots shall be continuously burning with or without flare gas flow to flare.
Some legal and regulatory requirements or operating permits require continuous
monitoring of flare pilot operation. Loss of pilot flame indication is qualified as an
environmental incident, even though pilots remain lit. These events are required to
be reported, and citations possibly may follow.
Page 45 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
b.
Pilots shall reliably light the flare flame on single burner and multiburner flares.
Flame retention devices and wind shrouds may be used to achieve reliable ignition
and stable pilot flames.
c.
To ensure stable operation and ignition of the flare gas, minimum pilot heat release shall
be 13,2 kW (45 000 Btu/hr) LHV, if flaring hydrocarbon gases with a lower heating value
of 11 175 kJ/scm (300 Btu/scf) or greater.
Typical pilot heat releases in common practices range from this minimum up to
102 500 W (350 000 Btu/hr). Flare vendor typically determines the actual size of
pilot for particular applications.
Pilots shall be capable of remaining lit even if the flaring gases are not flammable.
PY
d.
For nonhydrocarbon gases or hydrocarbon/inert mixtures with heating values less
than 11 175 kJ/scm (300 Btu/scf), additional pilots, higher heat release pilots, or
some other form of fuel gas addition may be required.
Pilot shall remain lit and continue to ignite the flare at wind speeds up to 160 km/hr
(100 mph) under dry conditions and 140 km/hr (85 mph), if combined with 50 mm/hr
(2 in/hr) rainfall. Flare vendor shall provide data on pilot testing to demonstrate
compliance to these requirements.
f.
Pilot(s) shall be capable of being relit under the environmental conditions specified in flare
data sheets.
g.
Pilots shall be designed for the specified fuel gas supply pressure, range of heating value,
and composition. These values shall be specified in the flare data sheet.
C
O
e.
T
A natural gas pipeline, a LPG vapouriser, or some other reliable source of gas is
typically used for pilot gas supply. Most commonly, the pipeline natural gas is used.
Automatic backup gas supplies should be used, if necessary, to achieve acceptable
overall reliability/availability.
Each pilot shall have primary means of ignition with backup and at least one dedicated
means of pilot flame detection.
O
h.
i.
N
Exception from this requirement for a specific application may be granted by entity
EA only if alternative means of flare ignition is provided.
Each pilot should have automatic pilot reignition system.
O
Impact assessment analysis is typically used to determine need for an automatic
pilot relighting system for each application. Based on results of analysis, exception
to this recommendation can be granted.
The number of pilots shall comply with Table 1.
D
j.
The number of pilots required is a function of the flare burner diameter. As the flare
burner diameter increases, the number of pilots required to reliably light the flare
increases, regardless of wind direction. The minimum number of pilots
recommended for most flare burners is given in Table 1 as a function of burner
outlet diameter (actual connection size, not hydraulic diameter) if flaring
hydrocarbon gases with a lower heating value of 11 175 kJ/cm3 (300 Btu/scf) or
greater. Pilots in excess of those shown are often added to further reduce the risk of
an unburned release.
For very small flares, a single 13,2 kW (45 000 Btu/hr) pilot reliably lights the flare
gas. However, if only a single pilot is used, a single pilot failure represents a
complete failure of the ignition system. Greater reliability can be achieved if at least
two pilots are installed on every flare.
Page 46 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Table 1 - Number of pilots for a single point flare
Minimum number of
pilots
DN (mm)
Flare burner outlet diameter
NPS (in)
1 (1)
2
3
4
(2)
< 200
from 200 to 600
from 600 to 1 050
from 1 050 to 1 500
> 1 500
<8
from 8 to 24
from 24 to 42
from 42 to 60
> 60
PY
Notes:
1. For toxic gas, the minimum number shall be 2.
2. Subject to agreement between BP responsible engineer and vendor.
Pilot tip is continuously exposed to the pilot flame and can routinely be exposed to the
flare flame. The pilot tip shroud/enclosure shall be constructed of a heat resistant material,
such as 309 SS, 310 SS, 310H SS, CK 20, or a nickel based alloy, such as 800H. The other
pilot tip internal components (such as igniter temperature sensor, etc.) shall be type 321 SS
as a minimum.
C
k.
O
For flare burners with outlet diameter larger than DN 1 500 mm (NPS 60 in),
vendor proprietary number of pilots may be selected. However, vendor proposed
number of pilots might be acceptable, subject to BP approval, if vendor can show to
satisfaction of BP that proposed number of pilots, performance, and function is
attained.
Type 316 SS should not be used and type 316L is not recommended because of
potential for catastrophic oxidation.
If the flare or pilot gases are expected to contain H2S, nickel based alloys should be
avoided, or some protective material should be installed to prevent high temperature
corrosion in this environment.
m.
Self aspirating pilots
2.
O
The air inlet shall be located such that it has uninterrupted air access and shall be at
least 1,8 m (6 ft) or 125% of the actual burner diameter (whichever is greater) from
the top of the flare.
N
1.
T
l.
Two filters or dual strainer type should be installed in parallel in pilot gas supply line
at grade ahead of pressure regulator. Differential pressure drop indication through
filter or strainer shall be provided.
If single filter is used, a bypass across filter should be installed to allow maintenance while
the flare is in operation.
o.
Filter elements shall have a mesh size of approximately 0,5 mm (0,020 in).
D
O
n.
p.
To avoid blockages by products of corrosion, the filter, piping, and fittings downstream of
the filters to the pressure regulator shall be type 321 SS or 347 SS.
q.
Stainless steel piping shall be used for pilot gas supply from the pressure regulator
(typically located at base of flare structure) to the pilot gas orifice.
Rather than installing at grade, the strainer or settling chamber can be installed
immediately upstream of the pilot gas orifice. However, if an elevated flare is used,
the strainer will be located at height and will be difficult to access for maintenance.
r.
Piping and components between the pilot tip and the air mixer shall be austenitic stainless
steel.
Material for components (piping, fittings and bracing, etc.) should preferably be the
same material grade as that used for the flare burner.
Page 47 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
s.
For guidance on pilot selection, maintenance, and troubleshooting, refer to
ISO 25457/API Std 537, Clause A.3.
4.8
Pilot ignition systems
4.8.1
Objective
Modify to Read
Pilot ignition system reliability and presence of pilot flames under all operating
conditions are considered to be the most critical factors for safe and proper flare
system operation.
4.8.2
PY
The objective is to reliably light the pilot under all relevant ambient conditions as specified in
flare data sheets.
Functional requirements
Modify to Read
O
Pilot igniters are typically based on use of remotely operated electrical igniter
located in pilot head and front flame generator located at the ground level.
C
Means of direct ignition of the flare flame exist other than a continuous pilot.
However, they are not typically used in refinery or petrochemical services. Such
technology includes direct electrical ignition and pellet pyrotechnical ignition
(Vetco Gas Technology) systems and may be used in noncontinuous flare systems
that include flare gas recovery. These technologies are not included in this GP or
ISO 25457/API Std 537.
T
Novel ignition systems may be considered if it can be shown to the satisfaction of BP
that required performance and function are attained.
O
There are numerous pilot ignition system designs available from which to select the most
appropriate for the application. Although design alternatives exist, the following are the
functional requirements that shall be met:
Pilot ignition system shall, as a minimum, be able to reliably light and relight the pilot at
wind speeds of up to 160 km/hr (100 mph) under dry conditions and 140 km/hr (85 mph) if
combined with at least 50 mm/hr (2 in/hr) rainfall. This performance shall be verified by
type testing in accordance with a documented test protocol and documented results. A
typical test protocol is in ISO 25457/API Std 537, Clause A.6.
b.
Pilot ignition system shall be able to light the pilot during all defined operating and
emergency relief cases, including a sitewide general power failure.
O
N
a.
Ignition system shall be capable of igniting each pilot independently of the other pilots
without depending on the flare flame for ignition.
d.
Ignition system components shall be suitable for surrounding zone classification.
e.
Ignition panel shall, if possible, be located in nonhazardous classification area.
f.
Igniter fuel gas system shall be designed such that it is not itself a source of hazard.
g.
Typically, a flare ignition system should consist of a primary ignition system and a backup
system. The system should be configured to have a remotely operated igniter (i.e., piezo
spark element) located in the pilot burner and a manually or automatically operated flame
front generator as a backup system.
D
c.
Manually and automatically operated flame front generators have been proven to be
costly and less reliable than other means for pilot ignition.
Page 48 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
h.
Flame front ignition system shall be designed to operate satisfactory without adjustments
to air and gas flows for specified pilot gas molecular weight and calorific value range.
i.
Flame front ignition system lines
1.
Each pilot in flame front generator system shall have dedicated flame front line.
2.
One manifold that connects these lines with necessary valving to accommodate
ignition of one pilot at the time shall be provided.
3.
Use of one front flame line to simultaneously ignite more than one pilot shall not be
allowed.
If a flame front generator pilot ignition system is being used, a check valve shall be
installed on the air line and pilot gas line.
k.
A pilot automatic reignition system based on pilot flame monitoring information should be
provided on all flare applications.
PY
j.
O
Loss of flames can cause a serious operational hazard to humans and equipment.
Also, most operating permits require the pilot to be operational at all times. These
two requirements support the need that a pilot flame monitoring based automatic
pilot reignition system is provided.

O

Operating permit requirements that pilots be lit at all times to confirm that flare
is operational.
Protection from hazard associated with unlit flare (i.e., formation ground level
vapour clouds, toxics release, odours release).
Reduces need for operator intervention, requiring operator to go in field to
relight the pilots during unit upset conditions when the loss of pilot flames is
most likely to occur.
T

C
The following are some of the reasons that may lead to a decision to provide an
automatic pilot reignition system:
A flare gun is not an independent manual backup.
The Impact Assessment process should be used in each flare application to determine need
for automatic pilot reignition.
m.
Auto reignition shall be installed for ground flares, flares discharging toxic gases, and for
continuously operated flares in regions where uncombusted discharges from flares could
affect license to operate and/or violate local laws.
N
l.
O
This requirement provides protection from hazards associated with unlit flare (i.e.,
formation ground level vapour clouds, toxics release, odours release, etc).
For additional guidance on pilot ignition equipment selection, maintenance, and
troubleshooting, refer to ISO 25457/API Std 537, Clause A.
D
n.
4.9
Pilot flame detection
4.9.1
Objective
Add
The objective is to reliably detect the pilot flame under all relevant ambient conditions as
specified in flare data sheets.
Page 49 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
4.9.2
Functional requirements
Add
A pilot flame detection system may use the heat, ionised gas, light, or sound
generated by a pilot flame to verify that a pilot is burning. An example of the use of
each of these energy sources for flame detection is described in
ISO 25457/API Std 537, clause A.5.2.2 to A.5.2.5.
PY
For pilot flame detection system based on use of thermocouple, thermocouple leads
are usually connected to a temperature switch with predetermined set point. If the
thermocouple temperature is above the set point, the pilot is assumed to be
operating. Selection of temperature set point is important for proper system
operation (i.e., if high set point temperature selected system would provide more
rapid indication of pilot failure). However, in this mode, it also increases the
potential for nuisance false alarms caused by wind, rain, or flare operations.
Pilot flame detection system shall be able to confirm presence of flame in operating pilots
independently of the system that monitor flame status of the main flame.
b.
Pilot flame detection, pilot flame status, should be based on use of two independent flame
detection devices.
O
a.
C
Use of duplex thermocouples as two independent flame detection methods would be
acceptable and cost effective in some applications. However, Impact Assessment
review may be needed to determine if in certain applications use of dual
thermocouples meet all operating and reliability requirements.
Any pilots that are required to be automatically relit shall be activated on loss of flame
indication from the pilot flame detection system.
d.
Loss of pilot flame shall be alarmed locally and in DCS.
e.
For guidance on pilot flame detection equipment selection, operation, maintenance, and
troubleshooting, refer to ISO 25457/API Std 537, Clause A.5.
O
T
c.
Piping
4.10.2
Functional requirements
N
4.10
Add
For guidance on functional and design requirements for flare piping, refer to the flare and
atmospheric vent systems, headers and piping clause in GP 44-80.
b.
The following are additional piping requirements that are not included in
ISO 25457/API Std 537 or GP 44-80:
O
a.
Auxiliary flare piping required for flare operation shall be provided.
D
1.
Such piping may include:









Pilot gas line.
Pilot air line in forced draft pilots.
Flame front igniter line to each pilot.
Steam line to main smoke suppression system.
Steam line to auxiliary system.
Oxygen sampling lines.
Assist gas.
Electrical conduit.
Instrumentation conduit.
Page 50 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
a)
To simplify flare burner changes, joints between flare stack and flare burner,
such as burner joint, utilities (steam, air, water, pilot gas, etc.), and flame front
generator (FFG) piping, regardless of size, shall be flange joint type.
b)
Except for electrical conduits, joints shall not be threaded.
c)
Mechanical suitability shall be confirmed for the specific application.
Flanges shall be as follows:
For DN 600 (NPS 24) and smaller burners: ASME B16.5, Class 150 RFSO, or
EN 1092, PN 20 Type 01.
b)
For sizes greater than DN 600 (NPS 24): forged flanges in accordance with
ASME B16.47 or fabricated plate flanges as specified in
ISO 25457/API Std 537, Table A.2. For flange sizes greater than those in
Table A.2, flare manufacturer standard shall be followed.
c)
Auxiliary connections larger than DN 25 (NPS 1), such as those for steam and
natural gas: flange ratings shall comply with ASME B16.5.
d)
The attaching flange should comply with the metallurgical requirements of the
flare support structure. For a carbon steel stack, a carbon steel burner flange
shall be acceptable.
PY
a)
O
3.
Flange joints
C
2.
Typical bolting material used for bolting flanges shall be cadmium plated A193-B16
studs and A194-2H nuts. Bolting of grades B and M and Class 2 of B and T should be
avoided because of stress corrosion cracking.
5.
Gaskets shall typically be Flexitallic Style CG or equivalent, type 304 SS, filled with
filament materials, and with type 304 SS gage ring if style CG is used.
6.
Components that are made of carbon steel shall have minimum corrosion allowance
of 3 mm (1/8 in) for unlined flare tube/body and 1,5 mm (1/16 in) for refractory lined
flare tube/body.
7.
The surface of stainless steel burner components that are exposed to high temperature
during flare operation shall not be contaminated by contact with galvanised piping
and supports. Presence of zinc contamination can cause cracking in stainless steel
material that may lead to flare burner catastrophic failure.
O
Differential thermal expansion of auxiliary flare piping shall be specifically allowed
for in design.
Piping in elevated flares shall preferably be anchored at top of stack in vicinity of
bottom of flare burner and guided along length of stack, with expansion taken up by
flexing of sufficient horizontal length of connecting piping at ground level.
D
O
9.
N
8.
T
4.
The described preferred method to allow for thermal expansion is considered much
simpler and better than the often used expansion loops, one per riser section. The
loops produce additional wind loads, are often subject to vibration, and are difficult
to insulate and inspect properly.
10. Stainless steel that is used for oxygen sampling lines shall be type 321 SS or 347 SS.
11. Oxygen sampling line should be 15 mm (1/2 in) outside diameter (OD).
12. Igniter piping and flame front generator piping up to flange near flare burner may be
carbon steel.
13. Attachment of pilots, steam injection equipment, windshields, and similar items
should accommodate the differential thermal growth that can occur during service.
Page 51 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
14. Consideration shall be given to need for hydrotesting after construction. If
hydrotesting is required, all components, particularly foundations and supports, shall
be designed for this condition.
If using steam for smoke suppression, flare steam piping shall comply with the following:
Steam lines should be suitably filtered as close to flare base as practical but upstream
of flow control valve.
2.
To cool steam pipe components at flare burner, minimum flow of steam shall be
maintained by using bypass around steam control valve.
3.
Material of the upper steam ring and ejectors shall be selected on the basis of
exposure to the flame and cyclic conditions.
4.
Material selection for the flare burner steam piping should take into account effects of
itergranular corrosion due to the wet, cyclic, high temperature service and corrosive
flue gas effluent characteristics.
5.
Steam piping shall be designed for all operating and test loads, including water filled
steam piping.
PY
1.
4.11
Auxiliary components
4.11.2
Functional requirements
a.
C
Add
O
c.
Flare burner handling and lifting lugs shall comply with the following:
Three lifting lugs on 120 degree centreline should typically be used for flare burner
lifting. Vendor may request exception from this requirement, subject to approval by
the BP responsible engineer, if type of flare burner and lifting procedure/method
cannot accommodate use of three lifting lugs.
T
1.
If height of flare is such that mobile lifting facilities available at site are not adequate
for removing and replacing flare burner, flare stack shall have derrick or other
suitable handling appliance. Information on maximum size of lifting crane that is
available at the site will be provided.
O
2.
N
O
Lifting lugs or brackets cannot be reused because, if left attached, will be subjected
to flare operating conditions, including potential internal or external flame
attachment. They are typically removed after installation is completed and prior to
placing the flare burner in service. Often such lifting lugs are made of carbon steel,
designed to “burn off” in operation.
In normal flaring operations, derrick shall be lowered below level of top platform or
below bottom of the inverted gas seal, if fitted, to position where it will not be
affected by flare operation. Derrick shall be stored such that full load testing is not
required before subsequent reuse.
D
3.
b.
4.
Suitable lifting tackle shall be provided to raise derrick to lifting position. Wire ropes
used for lifting derrick and flare burner and seal, if fitted, shall be replaced by reeving
lines and removed to storage.
5.
Derrick anchor system and associated lifting equipment shall be designed for
temperatures to which it will be subjected during flaring without significant
deterioration and shall be capable of operation after exposure to these temperatures.
Purge gas conservation seals shall comply with the efflux velocity acceleration (velocity
seals) clause in GP 44-80.
Page 52 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
c.
Windshields for flare burners
1.
Windshields are typically applied to unassisted pipe flares. As a basic consideration,
windshields for pipe flares should be considered sacrificial equipment.
The windshield is likely to burn up, sacrificing itself to promote improved service
life of the pipe.
2.
Windshields often can be provided for ground flares. Their design and application can
have a significant impact on flare performance.
3.
A properly designed steam assisted flare, air assisted flare, or high pressure flare
burner should not require a windshield.
d.
PY
Windshield design is somewhat proprietary to the flare burner manufacturer.
Flare burner barrel and welded attachments should be welded in accordance with
applicable pressure design and/or structural design welding requirements.
Add
Controls and instrumentation
O
4.12
C
ISO 25457, Annex A, Clauses A.10, A.11, and A.12, provides general information
for controls and instrumentation for flares. Annex A is informative and is not
included in this GP.
This clause contains some BP specific controls and instrument requirements.
4.12.1
Functional requirements
b.
For flare gas from knockout drum to flare stack:
Flow indication and recording.
2.
Temperature indication.
3.
High/low temperature alarm (either or both as appropriate).
O
1.
N
a.
T
The following are normal controls and instrumentation requirements that should be considered
for use in a typical flare system:
For steam to flare stack for smoke control (if installed):
1.
2.
Flow indication and recording.
Steam pressure indication (local or remote) located downstream of control valve.
O
3.
Flow control: automatic and/or manual.
For flare stack internal atmosphere:
1.
Oxygen contents indication (if oxygen monitor is required and installed).
2.
High oxygen contents alarm (if oxygen monitor is required and installed).
D
c.
d.
For each knockout drum:
1.
Level indication.
2.
High level alarm (This alarm shall be a critical alarm).
3.
Level switches or transmitters (if automatic operation of pumps is used).
4.
Level gage.
5.
Upstream pressure gage.
6.
Temperature indicators/alarms for liquid phase (as appropriate).
Page 53 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
h.
i.
Level indication.
2.
Low level alarm.
3.
High level alarm.
4.
Liquid temperature indication.
5.
Temperature control (by steam or electricity).
6.
Adequate instrumentation for liquid sump tank and liquid overhead drum if fitted.
For pilot gas:
Flow indication.
2.
Pressure control valve.
3.
Pressure indication located downstream of control valve.
4.
Low flow alarm.
5.
Indication of backup supply in operation.
O
PY
1.
For purge gas:
Flow indication.
2.
Flow control.
3.
Low and high flow alarm.
4.
Staging valve leak detection.
C
1.
For air to pilots (if forced draft type is used):
T
g.
1.
1.
Flow indication.
2.
Low flow alarms.
3.
Pressure control valve.
4.
Pressure indicator.
O
f.
For each liquid seal:
N
e.
For smoke control and monitoring:
1.
2.
Flame radiation sensors.
Flare gas density meter.
O
3.
Closed circuit television monitoring of flare flame.
j.
For pilot flame:
Pilot flame sensors.
D
1.
4.12.2
2.
Pilot flame ignition (electrical and front flame generator).
3.
Pilot flame failure (alarm).
Flare smoke controls and instruments
a.
Smokeless flares using steam or other pressurised fluids for smoke suppression should
have either manual or automatic control systems that will apportion suppressant to the flare
gas to produce clean burning without excess flow. The control system selection and
requirements shall be specified in flare data sheet.
In many cases, if steam is used for smoke control, manual actuation and flow control
of the steam upon visual detection of smoke is adequate to minimise and eliminate
smoking.
Page 54 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Excessive steam flow is not only costly but also increases flare noise.
b.
If using automatic controls, one of the following four main types of control should be
considered:
1.
Ground mounted optical flare infrared radiation sensor.
2.
High radiant heat sensor.
3.
Measurement of the flowrate of flare gas through an ultrasonic mass flow meter.
4.
Pressure measurement of flare gas.
Preferred method of control is by flare gas flow.
Smoke control system using ground mounted or high level radiation sensor should be
based on the difference between greater radiation rates from a smoking flame than that
from a smokeless one.
PY
c.
The optical monitor shall be a rugged telescope with a restricted field of view and have a
photocell sensitive to near infrared radiation. The telescope shall be waterproof design and
allow regular cleaning of the lenses.
C
d.
O
Measuring the radiant heat energy from a portion of the flame may be achieved
either by an optical monitor located at ground level at moderate distance from the
flare stack base and trained on the base region of the flame or by paralleled high
level radiation sensors spaced around the stack immediately below the tip.
T
The advantage of an optical monitor is that it is located at ground level. Therefore,
it can be checked and maintained at any time. It also has fast response. The
disadvantages are that it requires a very precise aiming which can easily be
disturbed and is not sufficiently selective to allow its use for multiburner
installations.
For both types of radiant heat measurement, need for compensation for ambient variations
(night/day, sun/cloud) should be considered.
f.
Signals from the monitor shall operate an actuated control valve, via appropriate
converters, which shall be adjustable up to the required flow range and down to zero flow
under normal conditions.
g.
Appropriate control algorithms shall be developed to automatically position valves and
controls for smoke suppression with the following considerations:
Controls shall be matched to flaring conditions in the process to conserve smoke
suppression fluids while preventing smoke from being formed during a flare event.
O
1.
N
O
e.
2.
The following are design requirements for systems that use flare gas flowrate for smoke
control:
D
h.
Manual control to allow direct operator intervention as an override of automatic
control shall be provided.
1.
Flow measuring device shall not obstruct line or reduce its capacity.
2.
Flow measurement should be by flow sensing elements inserted into blowdown line.
3.
Elements should be removable and serviceable while flare is in service.
4.
Density measurement and compensation need only be considered if flared gas
accounting is necessary and to provide corrections that allow more suppressant for
heavier hydrocarbon gases.
5.
Signals from monitor shall operate smoke suppressant media via appropriate
converters, adjustable for range and zero.
Page 55 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
6.
i.
System based on incoming flare gas pressure measurement of flare gas could be used to
appropriate required amount of suppressant added for smoke control. The design
requirements for this system are similar to requirements for system based on flare gas flow
measurement.
j.
Systems that use either flow or pressure sensors for control smoking in flares shall contain
facilities for onstream inspection and maintenance of all the important parts of the system.
If specified by BP in flare data sheets, system shall include a density measuring device to
provide correction using more suppressant for heavier hydrocarbon gases.
Burnback
PY
4.12.3
Manual control to allow direct operator intervention as override of automatic control
shall be provided.
Burnback detection is not normally required. However, if burnback protection is required, the
following shall be provided:
b.
Burnback detection shall be provided by one or more thermocouples in thermowells
located inside the flare burner.
c.
Thermocouples shall be wired to control room alarms through a temperature switch
adjustable for a temperature range appropriate for the flare burner.
O
Either refractory lining or burnback prevention methods (i.e., adequate purging) should be
used.
C
4.12.4
a.
Purge control
4.12.5
Oxygen monitoring
T
Continuous purge flowrates for the flare system shall be controlled, monitored, and alarmed on
high and low flow conditions.
O
The primary purpose of oxygen monitoring equipment is to ensure that, if a
minimum purge rate is used, an explosive atmosphere does not result. It may also
highlight the spurious ingress of oxygen due to operating deviations, such as
contraction of flare stack gas during rapid cooling or a process shutdown.
N
Oxygen monitoring is not generally required in every flare system application or if
there are alternate means of ensuring that the system is air free, such as a reliable
continuous purge.
O
If measuring the oxygen content is required to prevent deflagration to occur inside
the flare system, an oxygen analyser is added to the flare system. Typically, purge
gas rate is set to achieve less than 6% oxygen in the disposal stack at 8 m (25 ft)
down from the discharge point.
To prevent air egress into flare system, proper purge gas rate and allowable percentage of
oxygen in flare stack shall be determined in accordance with GP 44-80.
b.
If there are alternate means of ensuring that the system is air free, such as a reliable
continuous purge, oxygen monitoring shall not generally be required.
c.
If oxygen monitoring is required and installed, the following shall apply:
D
a.
1.
Alarm point for the oxygen monitor should typically be set at approximately 1%
oxygen in flare gas.
2.
The oxygen sampling probe shall be located 8 m (25 ft) or 15 diameters, whichever is
the smaller, below the flare burner exit. Probe piping shall comply with vendor
requirements and shall be resistant to fouling or contamination by CO2 or other waste
gases in the flare stream.
Page 56 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
The oxygen analyser installation should be suitable for access and mounting in an
outdoor, exposed location at the base of the stack or at the flare knockout drum.
4.
Monitoring system, if located in an area where radiation level may exceed
4,73 kW/m2 (1 500 Btu/ft2 hr), shall have suitable shielding.
5.
Oxygen sensor and its electronic support package shall be capable of operating in the
expected temperature ambient range, particularly considering potential flare radiation
impacts.
6.
Sample gas shall be withdrawn by a diaphragm type vacuum pump, fitted upstream
with liquid knockout pot, and returned to the stack above the sample point. This is
required to avoid fluctuating pressure in the sampling line due to changes in pressure
drop through the stack induced by changes in flowrates.
7.
A portion of the sample gas shall be taken through a regulating needle valve to an
oxygen analyser and exhausted to atmosphere. Local and control room indications
and alarms shall be provided as specified by BP.
PY
4.12.6
3.
Flow measurement
Control of the flowrate of the smoke suppressant.
Regulatory reporting purposes (i.e., flaring rates).
Information (e.g., loss management, accounting).
C



O
Flow measurement of the flare gas may be required for three reasons:
A potentially very wide range of flowrates between a purge and a full emergency
release presents a difficult problem for the instrumentation.
T
If flow measuring is required and used, the following should be addressed in instrument
selection:
The flow measuring device shall not obstruct the line or reduce its capacity.
b.
The proper flow measuring instrument should be selected for a potentially very wide range
of flowrates between a purge and a full emergency release. If the single instrument cannot
cover entire range, two instruments should be considered.
c.
Flow sensing inserted probes, if used, shall be:
1.
2.
Mounted in the flare line downstream of the offsite knockout drum.
Inserted via a seal housing and isolating valve.
Capable of being withdrawn during flare operation.
O
3.
N
O
a.
Density measurement and compensation should be considered only if flared gas accounting
is necessary.
e.
Potential presence of contaminants in the flaring gas should influence flow measuring
instrument selection.
f.
Unless an alternative is approved by the BP responsible engineer, flow measurement
should be made by an ultrasonic mass flow meter type. Refer to GP 30-10 and the GP 64
series on flow measurement for specific instrument requirements.
D
d.
Instrument requirements that differ from the requirements set above may be
acceptable, subject to BP approval, if it can be shown to the satisfaction of BP that
required performance and function is attained.
g.
Ultrasonic mass flow meters, if used, shall be mounted in the flare line downstream of the
offsite knockout drum and installed in accordance with manufacturer recommendations.
Page 57 of 84
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h.
4.12.7
If an alternative type of flare meter is used that is installed in the flare gas stream, the
measurement device should be inserted via a seal housing and isolating valve, providing
the capability of withdrawing the instrument during flare operation.
Enclosed flame flare controls and instruments
Enclosed flame flares require a number of operational and safety controls. As for
any flare, the relief gas should never be ignited without the assurance that safe
operating conditions exist by providing adequate purge and all operating and safety
systems are fully functional.
As a minimum, facilities shall be provided for permanent monitoring of enclosed flame
flare flame status, chamber temperature, and draught.
b.
Flame supervision shall be provided to include the following:
1.
Each main flame zone of enclosed flame flare shall be individually monitored with
flame detector capable of discriminating between that zone and adjacent flame zones,
including pilot flames.
2.
Alarms shall be provided, locally and in DCS, to indicate loss of main flame.
O
c.
PY
a.
If burner staging is used, on/off tight shutoff valve shall be used.
A dedicated programmable controller normally controls staging.
d.
T
C
Tight shutoff valves are required to avoid gas leaks in quantities that are below
minimum design flow to burner stages. Gas leaks can cause flame instability and
release of unburned gases within enclosed flame flare. Use of modulating pressure
control for staging is not preferred because staging is used for modulation.
Therefore, there is no need to modulate the flow by these types of valves.
Dampers or other means should be used to control the natural draught airflow into the
combustion chamber.
Forced draught air movement should be considered to achieve the following:
1.
2.
To supplement flame energies to produce smokeless flames and reduced flame
volumes.
N
e.
O
Control of the airflow can allow for control of the combustion chamber operating
temperature over variations of relief gas flowrate and composition.
If tighter temperature control of the combustion chamber is required, 100% air
volume should be provided by forced draft.
O
Excessive use of forced draught can contribute to enclosed flame flare noise,
resonance, and vibration.
If using a forced draught fan and its driver, impact on reliability and availability of the
overall system should be evaluated.
D
f.
g.
h.
As a minimum, a high temperature alarm shall be provided for protection from combustion
chamber overheating.
The combustion chamber of an enclosed flame flare can overheat if the gas heat
release is too high and/or if the airflow is not sufficient. The gas heat release can be
too high due to excessive gas flow or due to changes in gas composition. The airflow
demand can exceed the design or can become restricted.
Shutdown of an enclosed flame flare shall not restrict safe discharge and disposal of relief
gases.
The control action to protect combustion chamber from exceeding high temperature
conditions can be to limit flare gas flow to enclosed flare by disengaging a burner
Page 58 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
stage or stages and divert part of the relief gases to other systems, such as an
elevated flare.
For enclosed flare flames that are located in an area where gas vapours can be present,
lower explosive limit (LEL) meters with an alarm should be provided and located adjacent
to the flare.
j.
Relief gas compositions that are difficult to ignite and combust should be aided by the use
of fuel enrichment.
k.
If fuel gas enrichment is required, a flare gas analyser combined with fuel gas enrichment
control systems shall be provided.
l.
Combustor temperature control in an enclosed flame flare should be integrated in fuel gas
enrichment control. By varying enrichment fuel gas rates to maintain combustor
temperature set point, a reduced amount of required enrichment fuel gas rates can be
achieved and required combustion/destruction efficiency maintained.
PY
4.12.8
i.
Noise and vibrations
O
As some heat release energy in an enclosed flame flare is converted to acoustical
energy, high noise levels can be encountered. Burner design and burner stability are
key elements to controlling enclosed flame flare noise.
Anticipated noise level should be evaluated based on heat release and number of stages
that are operating.
b.
A wind fence should be used to acoustically isolate combustion chamber noise.
c.
Wind fence should be designed to achieve an 85 dBA noise level or less at a distance of
1 m (3 ft) from the wind fence with all stages in operation.
d.
Forced draught fan and its driver shall have antivibration mounts and comply with
API Std 673 for centrifugal fans of more than 20 kW (27 hp).
O
T
a.
Precommissioning and commissioning
N
4.13
C
The following noise and vibrations control issues should be addressed by enclosed flame flare
design:
Pipework associated with the flare should be tested prior to the installation of the flare burners
and pilots, with consideration of the following:
Scaffolding, supports, tools, etc., shall be removed from within the perimeter of the wind
fence or other barrier that indicates restricted access.
O
a.
Flare lines shall be free from debris and obstruction.
c.
Lines should be blown down prior to installing the flare burners, pilots, and steam nozzles
(if fitted).
D
b.
d.
Lines should be blown down with a velocity greater than that which is encountered during
normal operation. Typically, such velocity exceeds 90 m/s (300 ft/s).
e.
Pilot orifices shall not be blocked.
f.
Purging
1.
The flare line downstream of the main header blind should be purged with inert gas to
reduce the oxygen levels to safe proportions.
2.
The header should be purged with at least 10 times the free volume of the header with
a noncondensable, inert gas.
Page 59 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
a.
Once flare is commissioned, control unit should monitor operations and operation
sequencing. No operator intervention should be required.
b.
Operations of flare system should be observed to ensure that preselected pressure and
control parameters/settings operate satisfactorily.
c.
Sweeping combustibles from system for shutdown
If shutting down system, it may be necessary to sweep all combustible gases from
headers. Inert gas injection into flare header at a point farthest from flare should be
used.
2.
Inert gas flow should continue until some time after flare is extinguished to sweep all
combustibles remaining in system.
3.
Pilots should remain in service during sweep operation.
4.
If plant personnel are scheduled to enter flare area for any reason, sweep of all
combustibles from all stage headers shall be performed.
PY
1.
Designs that maintain the first stage in operation on a constant basis shall have a small
continuous bleed/purge gas flow at all times. It is not normally necessary to purge any
stages with a minimum flow during normal operations.
e.
Leak/flow detection devices shall be installed and maintained downstream of stage
isolation devices.
f.
If a leak is detected through a staging device, appropriate stage purge shall be activated to
prevent internal combustion.
C
O
d.
a.
T
Inspections
Inspection requirements
1.
The inservice inspection requirements for flare burners and appurtenances are in
GP 32-49.
2.
Requirements for elevated flare support structures inspection are in GP 32-46.
3.
Flares shall be designed to facilitate the inservice inspection requirements in 1. and 2.
O
4.15
Operations
N
4.14
Normal inspection and maintenance procedures as specified by the manufacturer or that
are normal good practice should be followed.
c.
General inspections of all aspects of the flare should be undertaken at every convenient
shutdown. In particular, the following conditions should be assessed:
O
b.
1.
General burner condition, such as:
D
a)
2.
Distortion/damage.
b)
Condition of feeder piping.
c)
Excessive carbon deposits should be removed.
d)
Port blockage: nozzles and orifices should be cleaned and blown clear, as
appropriate.
e)
Pilot burners.
Refractory lining
a)
The internal lining should be examined visually and an assessment made on the
level of damage at every suitable opportunity when the flare is shut down. See
ISO 25457/API Std 537, clause C.3.3, regarding expansion joint condition and
cracking considerations.
Page 60 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
b)
Temporary patching should be considered to avoid further damage.
c)
Visual inspection for hot spot distortion should be performed during an outage.
d)
Visual or infrared inspection for hot spots should be performed while operating.
3.
Flare structures and burner manifolding should be examined using normal
maintenance procedures and action taken as appropriate.
4.
Staging and block valves
Valves should be regularly stroked to ensure continued operation.
b)
Actual valve position should be compared versus the intended position from
control signal.
c)
Valves should be maintained in accordance with manufacturer instructions.
5
Mechanical details - Elevated flares
5.1
Mechanical design - Design loads
O
Modify First Paragraph to Read
PY
a)
Clause 5 of this GP covers the additional BP requirements, in addition to requirements
contained in ISO 25457/API Std 537, for support structure and includes both single burner
and multiburner elevated flares.
b.
Structural design of elevated flares, whether guyed, mast (self supported), or tower
supported, shall be performed by specialists in this field with a proven record of
experience.
c.
If possible, a single contractor should be responsible for design, detailing, supply, and
erection of flare system.
d.
Materials of construction, standards for fabrication, inspection, and nominated fabricator
shall be subject to approval by the BP responsible engineer.
O
T
C
a.
N
BP may specify requirements for materials of construction in data sheets. However,
vendor may propose alternatives that are subject to BP approval, if it can be shown
to the satisfaction of BP that required performance and function are attained.
Typically, the flare vendor proposes standards for fabrication, inspection, and
nominated fabricator for BP acceptance and approval.
Self supporting stack for facilities located within North America shall be designed in
accordance with API Std 560.
O
e.
f.
Facilities located outside of North America shall be designed in accordance with
ISO 13705.
D
Modify Third Paragraph to Read
a.
Design of a support structure for a vertical elevated flare shall address, as a minimum,
design criteria and loads as specified in ISO 25457/API Std 537 and as given in flare data
sheet provided by BP, as appropriate.
b.
Designer shall review the intended application and may ignore loads that are not applicable
or significant for the selected design option.
The following are some aspects of design that may require consideration:


Static wind loading.
Dynamic effect of wind, including the effect of wind turbulence on the dynamic
response of the structure.
Page 61 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)


PY

Earthquake loads.
Internal pressure and sudden internal pressure.
Credible external fire and blast loads for the mechanical design.
The vortex shedding phenomenon.
The dynamic response of guys, including “galloping” response.
Ice loading on the structure and its effect on the static and dynamic response.
Local stress at guy attachment points and local stress due to the choice of
structural element (i.e., in the case of tubular joints, punching shear stress).
Radiant heat and its effect on the riser, guys, upper guy fixings, and upper
members in the case of a structure.
The effect of fatigue. Analysis needs to be performed in accordance with the
Department of Energy (U.S.) guidance notes “Offshore Installations: Guidance
on Design and Construction”, using n/N no greater than 0,5 for the design life.
The fatigue design needs to take into account the full extent of the allowable
misalignment of circumferential seams.
Shell and strut buckling for the static and dynamic loads.
O







Structural calculations shall be submitted by flare vendor, be subject to review by the BP
responsible engineer, and shall demonstrate that, in proposed design, vendor addresses
design requirements that are listed in ISO 25457/API Std 537 and BP flare data sheets.
a)
Wind loadings
C
c.
Modify to Read
2)
As appropriate, wind loading on supporting derrick structures shall be included.
3)
Wind loads shall be based on local regulations (e.g., ASCE 7).
T
Wind loadings shall take into account the riser and all of its appurtenances, such as
piping (including insulation, if any), access platforms and ladders, formation of ice,
and all other wind related considerations as specified in flare data sheets.
O
b)
1)
Earthquake-induced loads
1)
Earthquake-induced loads shall be based on local regulations (e.g., ICBO or
ASCE 7).
BP will provide flare designer with data on applicable earthquake zone in which the
flare is located.
O
2)
N
Modify to Read
3)
Wind-induced vibration loads
D
c)
Structural design shall be based on wind loads and earthquake loads occurring
separately.
Modify to Read
Structural design for wind-induced vibration shall comply with the ISO limit state method in
ISO 13705, Annex H, or ASME STS-1 for flares located outside of North America and API 560
for flares located in North America.
d)
Internal pressure
Add
In addition to requirements in ISO 25457/API Std 537, structure shall be designed to withstand
thrusts from liquid slugs (if there is risk that these can occur).
Page 62 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
e)
Jet loads
Modify to Read
1)
In consideration of sonic type flares with an exit velocity greater than Mach 0,8,
special considerations related to vibration and fatigue shall be considered in the
mechanical design.
2)
Refer to ISO 25457/API Std 537, Section A.2.6, for guidance.
3)
The requirement for vibration and fatigue analysis shall be subject to mutual
agreement between BP and flare vendor.
f)
PY
BP may specify requirements for vibration and fatigue analysis in data sheets.
However, vendor typically proposes to BP analysis method for acceptance/approval.
The proposed method, subject to BP approval, should demonstrate to satisfaction of
BP that proposed analysis meets performance and functional requirements.
Flashback pressure
Modify to Read
h)
C
O
If BP has specified in data sheets that flashback pressure shall be taken into account, BP shall
either specify the pressure used in the calculations on the data sheets or the pressure shall be
provided by the vendor. Vendor shall provide information for BP responsible engineer approval
on method used to determine the pressure generated by flashback.
Thermal loads
Add
i)
T
Structural components shall be designed to ensure that allowable stresses will not be exceeded
at temperatures which may be reached due to thermal radiation, hot gas flow, and, if applicable,
flame impingement.
Erection and/or maintenance loads
2)
5.2
Structure shall be designed for maintenance loads, such as supporting spare flare tip
during tip replacement, additional scaffolding, lifting beams, tools, and personnel.
N
1)
O
Add
Design of flare stack shall take into account proposed method of transportation and
erection.
Design details
O
Add
a.
The following requirements shall be incorporated into design of foundations:
Foundation design should be performed by principal civil contractor in accordance
with loads and moments specified by supporting structure designers.
D
1.
2.
If guys are used, specific attention shall be paid to potential for differential settling of
main foundation and those of concrete block foundation.
3.
Earthing (grounding) of flare structure and riser shall be independent of foundation
reinforcement and piling.
4.
Templates for anchor bolts shall be supplied and delivered to site in a timely manner
to enable associated civil works to commence.
5.
Templates for anchor bolts and design details of concrete block foundation shall be
provided by vendor to site in time for foundation construction. This requirement shall
be written into contract of supply to ensure compliance.
Page 63 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
b.
Field assembly of the gas riser or stack sections shall be by welding, unless specified
otherwise on the flare data sheets. Flanged assembly may be used on multiple section,
demountable risers.
c.
If flanges for guyed flares are used, the following requirements shall apply:
1.
Flanges for risers of guyed flares shall be forged weld neck type with flat faces.
2.
Jointing faces of flanges should be machined after welding flanges to pipe.
The machining is for ensuring proper alignment and flush fit of the components after
welding.
Accuracy shall be such that, after assembly, deviation of centreline from vertical shall
not be greater than 30 mm per 100 m (0,36 in per 100 ft).
4.
Gas inlet to guyed flares should be of same size as riser and may be in form of either
“tee” branch or bend.
5.
In both cases in 4., sufficient reinforcement shall be provided to transmit vertical
loads in riser from above inlet to below inlet without exceeding allowable stress
levels.
6.
Near atmospheric pressure in riser does not require use of raised face flanges.
O
PY
3.
7.
Full face gaskets with supporting inner and outer rings should be used.
The following are additional design requirements for guyed flare:
End fittings, turnbuckles, rods, and pins shall have a load capacity suitable for the
maximum guy wire tension expected. Guy wire hardware shall be strong enough to
withstand a force at least equal to the minimum breaking force of the guy wire.
2.
If effect of incident heat flux will reduce termination efficiency by more than 5%,
radiation shield in type 321 SS shall be provided.
T
1.
O
d.
C
Flat face flanges also reduce stresses in the bolting if the flare riser in a guyed flare
is subjected to bending from wind loads.
e.
N
The calculated heat flux is used to derive an equilibrium temperature for the
termination or guyline. For example, the incident heat load per unit length of a
guyline is proportional to the flux, the projected area in the flux plane, emissivity,
and diameter of the guyline.
The following are additional requirements for guyed flare installation and maintenance:
Initial guy wire tension shall not be less than 2% or greater than 12,5% of the
maximum guy wire tension expected.
O
1.
Initial guy wire tension shall include consideration of the ambient temperature
variation and loads offset along the relief gas riser.
3.
Sufficient articulation shall be provided in connections between guy wire
terminations at one end and rigging screws at other end to ensure that no bending
moment is transmitted to their respective attachment points.
4.
In light of experience, guys and associated equipment (i.e., shackles, turnbuckles,
anchor points) should be checked and regreased every 4 yr to 5 yr.
5.
Guys should be retensioned after first year of operation and every 4 yr to 5 yr
thereafter.
D
2.
Page 64 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
5.4
Welding
Add
a.
Welding procedures shall be subject to approval by the BP responsible engineer prior to
start of fabrication.
Typically, flare vendor provides welding procedures that will be used in fabrication
of flare components for BP approval. The welding procedures should be based on
applicable industrial standards and flare vendor internal fabrication specifications.
c.
Welds joining components of type 310S SS to same type or to carbon steel materials shall
be made with 309 filler rods.
d.
Flare vendor shall submit welding procedure and filler metal selection information for
welding of dissimilar metal joints for approval by the BP responsible engineer prior to start
of fabrication.
PY
Butt welds in the sections designed under pressure design code shall be full penetration
welds.
Inspection
O
5.5
b.
Add
b.
Butt welds in flare body and piping shall be 100% radiographed.
c.
Radiographic procedures and acceptance criteria shall comply with ASME B31.3 or other
pressure code applicable for particular application.
C
Flare vendor shall submit inspection scope and procedures for approval by the BP
responsible engineer prior to start of fabrication.
T
5.8
a.
Aircraft warning lighting
BP will provide requirements for aircraft warning lighting in flare data sheets. If BP does
not provide the requirements, lighting on the support structure shall comply with the code
specified by the local aviation authority, which is typically the national incorporation of
ICAO, Annex 14.
b.
Warning lights on the structure shall be fixed or retractable and shall be shielded from
radiation as necessary. Retractable aircraft warning lighting should be used.
N
a.
Platforms and ladders
O
5.9
O
Modify to Read
Add
Unless specified otherwise in BP flare data sheets, the elevated flares shall have ladders
and platforms to provide access for maintenance and inspection of flare burner and fixed
nonretractable aircraft warning lights and, on guyed flares, inspection of guy attachment
points.
D
a.
A ladder is the preferred means of access to a platform, but alternative access can
be achieved via a crane basket or helicopter.
b.
BP will specify requirements for access platforms for manways on knockout drum, liquid
seal, level instruments, staging valves in multistage flare, and other flare components in the
flare data sheets.
c.
BP should specify in the flare data sheet compliance design requirements for platforms and
ladders. If this data is not provided, flare vendor design shall comply with local
regulations.
Page 65 of 84
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d.
If two or more stacks are within 150 m (490 ft) of each other, access ladder shall be placed
such that stack shields ladder from heat radiation from other stacks.
e.
Platforms and ladders on flare stacks should present minimal wind resistance.
6
Mechanical details - Enclosed-flame flare
6.1
Combustion chamber
Modify to Read
The following are design mechanical requirements:
PY
Mechanically, combustion chambers are considered to be self supported stacks.
Therefore, most mechanical requirements for self supporting stacks apply to
combustion chambers.
Stack design should comply with code specified by BP or an acceptable code (e.g.,
ASCE 7) if information on applicable code is not provided.
b.
Design shall be based on site parameters from flare data sheets for wind speed, rain,
exposure factor, seismic factor, etc.
c.
Walls and floors and structural steel shall be designed to allow lateral and vertical
expansion of all enclosed flame flare parts under design conditions.
d.
Materials of structures and accessories shall be adequate for all load conditions at lowest
specified ambient temperature if flare is not in operation.
C
O
a.
The external shell of the combustion chamber is typically fabricated of carbon steel.
Casing plate shall be seal welded to prevent air and water infiltration.
f.
Consideration shall be given to potential occurrence of low temperature conditions,
particularly below acid dewpoint level, and potential effects of resultant condensation
within enclosed flame flare.
g.
Surfaces of flare that may come into contact with corrosive gases shall be given protective
coating against acid attack resulting from potential downwash of gases, in addition to
protection from atmospheric corrosion.
h.
If liquid carryover may occur, floor shall be gravel.
i.
Stack design and material shall accommodate thermal requirements of the enclosed flame.
N
O
T
e.
O
Most enclosed flame flares are designed to operate with a maximum internal
temperature of approximately 980°C to 1 090°C (1 800°F to 2 000°F).
The combustion chamber shall have an internal refractory lining.
D
j.
k.
Refractory insulation for thermal heat loss is not a factor in the design. A large
percentage of the heat of the enclosed flame flare is lost to the atmosphere. The
lining is provided for combustion chamber wall protection.
Refractory system selection and design shall consider:
1.
Peak operating temperature (with a safety factor).
2.
Exterior shell temperature limits for materials and coating.
3.
Thermal cycling with rapid increase and decrease of combustion chamber operating
temperature with changes in relief gas flows to the flare.
4.
Velocity of airflow into the combustion chamber and flue gas velocity out of the
combustion chamber.
5.
Environmental exposure to rain, wind, etc.
Page 66 of 84
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Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Refractory weight, friability, expansion/contraction factors, durability,
maintainability, and service life.
7.
Refractory curing schedules and startup plans.
The following refractory materials should be considered for use in the combustion
chamber lining:
1.
RCF in the form of blanket.
2.
RCF in form of modules.
3.
Combination of RCF modules and blanket.
4.
Gunned lightweight castable refractory.
5.
Ram plastic type refractory.
6.
Brick.
PY
l.
6.
RCF lining
1.
Restriction for use of first generation of ceramic RCF lining is required by each
application because this material is classified as a Class 2E carcinogen (in Europe,
RCF is classified as Category 2).
2.
Use of this material shall be subject to approval from BP industrial hygienist prior to
specifying this type of RCF lining.
C
m.
O
The most prevalent material used for internal linings is RCF. Use of RCF lining will
avoid refractory cracking due to sudden firing rate changes causing fast change in
combustion temperature.
3.
O
T
BP may require flare vendor and flare manufacturing shop to follow BP internal
policy that outlines requirements for personnel whom are working with and exposed
to RCF materials. The policy primarily addresses use of personnel protection
equipment (PPE) during fabrication, inspection, and preparations for shipment.
Use of RCF lining based on alkaline earth silicate wool shall be the first choice in
lining selection for combustion chamber.
O
N
Manufacturers of refractory ceramic fibres developed an alternative refractory
ceramic fibre material called alkaline earth silicate wool. This fibrous product,
which is made with alkaline earth silicates, does not contain aluminium oxide and
has proved to dissolve in body fluids of the lung. Manufacturers have performed
significant and thorough studies on this fibre material and have provided a safer
product for industrial use.
D
Potential limitation for use of alkaline earth silicate wool is in high temperature
applications.
Each facility is encouraged to research this material with manufacturers to ensure
that the workforce is adequately protected.
n.
Refractory design and procurement shall comply with GP 72-00, GIS 72-001, GIS 72-002,
and GIS 72-003.
o.
If air and flare gas velocities are suitable, ceramic fibre blanket system should be used for
enclosed flame flare lining as lowest cost option.
Generally, gas velocities in excess of 10 m/s (33 ft/s) are a potential problem for
ceramic fibre blanket, although there are ways to overcome the problem, such as
covering with expanded metal lathe, metal sheet, or wet felt soaked in rigidiser type
materials.
Page 67 of 84
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Choice of type of ceramic fibre lining will also depend on the combustion zone
design temperature. The application of the ceramic fibre modules or blocks may be
required for higher temperature. However, these systems are more costly than
ceramic fibre blanket system. These systems increase lining resistance to
temperature and erosion and should eliminate potential gas traps or areas where
gas could gain entry.
The following are additional mechanical requirements for refractory system:
Combustion enclosure refractory shall comply with relevant grade in ASTM C401 or
ASTM C155.
2.
Lining shall be capable of withstanding, without damage, temperature of 165°C
(300°F) above normal maximum flue gas operating temperature.
3.
If ceramic fibre construction is used:
PY
1.
a)
Casing shall have internal protective coating to prevent corrosion.
b)
Vapour barrier shall be required.
c)
Lining system shall be selected and applied in such a way to prevent water
ingress.
O
p.
C
If improperly installed, the lining for ceramic fibre lined ground flares can become
saturated with water and then with added weight, peel away from the walls.
Lining material selection shall be resistant to corrosion products of combustion
process.
5.
If multilayer linings are used, expansion joints shall not be continuous throughout
adjacent layer.
6.
Access doors shall be protected from direct radiation by material of at least same
quality as adjacent liner.
T
4.
Ladders and platforms, including bolting and other attachments, shall be hot dip
galvanised. In some applications, ladders and platforms shall have acid resistant protection
coating in addition to galvanising.
r.
Special consideration shall be given to selection and application of protective coating
systems, since exterior and interior metal temperatures can exceed 205°C (400°F). Type of
coating selected by vendor shall be subject to approval by the BP responsible engineer.
N
O
q.
O
BP may specify requirements for protective coating system in data sheets. However,
vendor typically proposes to BP, after preliminary design is completed, coating
type/system for acceptance/approval. The proposed coating system, subject to BP
approval, should demonstrate to satisfaction of BP that proposed system meets
performance and functional requirements.
Shape and size of the combustion chamber affects the degree to which the flare can be
preassembled to meet field erection requirements and shipped to the site. Flare vendor
shall submit its proposal, which shall be subject to approval by the BP responsible
engineer, prior to the fabrication start.
D
s.
BP may specify field construction specific requirements in data sheets. These
requirements may influence shape and size of the combustion chamber as well as the
extent of shop preassembling scope. However, vendor is typically responsible for
determining shipping routes and allowable shipping clearances for supplied flare
shop preassembled components. The proposed plan, subject to BP approval, should
demonstrate to satisfaction of BP that proposed shipping and field installation plan
meets BP requirements.
t.
Protection shall be provided against lightning.
Page 68 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
6.2
u.
Earthing (grounding) of the structure shall comply with BS 6651 or equivalent national
standards.
v.
Ladders and service platforms for access to enclosed flame flare instruments and for stack
emissions sampling shall be provided, if specified in BP flare data sheets.
w.
Personnel protection shall be required adjacent to the combustion chamber, if surface
temperatures exceed 80°C (175°F) for areas for personnel access during operation.
Burners
Modify to Read
PY
The design of burners for enclosed flame flares is typically proprietary to the
manufacturers.
Typical enclosed flame flare burners use a multiport design feature. Flaring gas
primarily provides energy for air and flaring gas mixing. The air pressure drop
across the burner is kept to a minimum.
O
Enclosed flame flares can have the burners firing in a vertical upward direction or
the burners can be horizontally fired into the combustion chamber. The choice of
burner firing direction is a function of size and manufacturer experience.
All enclosed flame flares, except the very smallest, use multiple burners.
C
For larger capacity enclosed flame flares, multiple burners typically operate in
staged systems.
Combustion temperature, gas composition, and potential flame impingement are the
primary criteria in burner material selection.
T
Enclosed flame burner design shall comply with the following:
Burners shall be designed for the relief gas flowrates, composition, and pressure and
temperature ranges of the gases as specified in BP enclosed flame flare data sheets.
b.
Use the utilities that are available for burner operation.
c.
Achieve the desired level of combustion emissions with flame volumes that are contained
within the combustion chamber.
N
O
a.
O
A large gas flowrate at a low pressure discharge produces a softer, larger flame,
unless supplemented by energy from the combustion airflow. Such flames can be
difficult to contain in the combustion chamber and have a propensity to produce
smoke and poor combustion.
Produce a stable flame for all relief gas flow conditions and compositions within the
design parameters.
D
d.
Burner flame stability is produced by the flare manufacturer proprietary means.
Mechanisms include mechanical elements of the burner design in conjunction with
air and gas flow dynamics.
e.
Not induce any combustion rumble that can trigger excessive noise and resonance from the
combustion chamber.
f.
Burners should be designed to combust low heating values and hard to combust relief
gases with a minimum addition of fuel gas to enrich the mixture to achieve desirable
combustion efficiency.
g.
With a staged burner system, only the first stage turns down to purge flowrates.
h.
If an unstaged burner system is used, all of its burners should be capable of turndown from
maximum flare gas flow to the minimum purge rate.
Page 69 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
i.
Gas jets in main burners should be sized sufficiently to remain free from blockage during
all operating conditions and with all possible gas conditions.
Gas jets in burners are typically sized to provide an optimal burner performance.
Requiring very large holes to provide some chance that blockage might be avoided
may impact burner design resulting in loss of mixing ability and poor performance.
If plugging of the burner jets is possible, some other means (e.g., use of strainers)
can be considered for prevention of burner jets plugging.
j.
Flare burner assemblies are typically connected to burner piping by flanged or screwed
fittings or by welding. Welding connection is preferred.
PY
Selection of the connection type needs to take into account the composition and
temperature of the relief gas and potential exposure to high thermal loads from
proximity to the flames or the combustion chamber. These temperature effects can
loosen screwed and flanged connections.
Heat affected areas are typically fabricated of heat resistant stainless steel. Burners shall
typically consist of minimum stainless steel grade 310 materials.
l.
Due to the potential for failure in the event of fire, burner pressure parts and their
associated supports, bolts, nuts, springs, etc., shall not consist of brittle materials (e.g., cast
iron, spheroidal graphite cast iron, malleable iron) and low melting point materials (e.g.,
copper or aluminium and their alloys or plastics).
6.3
C
O
k.
Burner piping
Modify to Read
Enclosed flame burner piping design shall comply with the following:
Piping material selection shall be compatible with the relief gas composition and
temperature and shall comply with requirements set by enclosed flame flare design. Flare
system operation may include situations in which releases become cryogenic.
b.
Burner piping should comply with applicable pressure design code, as a minimum.
c.
If liquid carryover and/or gas condensation can occur, piping design should accommodate
drainage. Liquid hydrocarbons that are retained in the piping can form blockages.
d.
Piping shall be engineered to have the flexibility to accommodate thermal expansion of the
combustion chamber and piping.
N
O
T
a.
O
Piping design needs to take into consideration the requirements to support and
maintain the burner position with respect to the air inlet to the combustion chamber.
Piping located inside the combustion chamber enclosure shall be designed for high
temperature exposure, since this piping can be subjected to flame impingement.
D
e.
f.
Piping internal to the combustion chamber can be subjected to flame impingement
resulting from poor air or gas distribution or as a result from liquid pool fires that
can form if condensation and liquid drainage into the combustion chamber occurs.
It can be necessary to protect piping external to the combustion chamber (but within
the wind fence) from radiant heat loads by radiation shields.
Burner riser
1.
Burner riser material shall be of suitable grade to withstand operating flare and flare
gas temperatures.
2.
Typical material for the riser is type 304 SS in the upper portion (approximately
1,8 m [6 ft]).
3.
The lower portion of the riser can be carbon steel.
Page 70 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
4.
g.
6.4
The riser should be properly insulated and jacketed, if required.
Manifold materials shall be of suitable grade to withstand operating flare and flare gas
temperatures. These individual manifolds may be externally insulated or covered by earth
and stone, as appropriate.
Pilots
Modify to Read
PY
Pilots for burners in enclosed flame flares are typically more protected from the
weather than those of open air elevated flares. With a properly designed enclosed
flame flare and with an effective wind fence design, airflow across the pilot and
burner is unidirectional, whereas open air elevated flare pilots are affected by wind
from varying directions.
Enclosed flame pilot design shall comply with the following:
a.
Each stage of an enclosed flame flare shall have at least one pilot.
O
A single pilot can light one main burner in each stage and cross ignition to other
burners can be achieved. At higher gas relief capacity, a substantial flame and a
high temperature exist in the combustion chamber. This can ignite the relief gas flow
from the subsequent stages.
C
The first stage can require more than one pilot for improved reliability.
b.
T
The precise number of pilots is primarily determined by layout of burners, number
of stages used, and ease to ignite the incoming flare gas. Climate conditions (wind
direction, ambient temperature, etc.) typically do not play a major role in selection
of the number of pilots required.
Pilot fuel and supply systems should be the cleanest and from the most reliable fuel source
in the plant.
c.
N
O
Due to lower cost, fixed firing rate premix burner type of pilot could be a first
choice in selection of pilots for enclosed flame burners if clean natural gas is used
as pilot gas. Consider use of forced air pilots in applications where pilot gas is not
natural gas.
Potential plugging of a quite small pilot orifice shall be mitigated by the following:
1.
2.
Use of a strainer located upstream of the pilot gas orifice.
Use of stainless steel piping from a strainer up to the pilot.
O
3.
Good piping design.
Pilots for enclosed flame flares should be engineered to facilitate inspection and
maintenance while the flare remains in service. This should be accomplished by locating
key components external to the wind fence and/or making the pilot assemblies easily
removable from outside the wind fence.
D
d.
6.5
Wind fence
Modify to Read
Enclosed flame natural draught flares use wind fences or other designs to mitigate
the potential of the wind to upset air and flue gas flows. Uniform airflow to all sides
of all burners is important in achieving controlled combustion. Wind fences
surround burner air inlets and are designed to allow control of the airflow
distribution to the burners.
Enclosed flame wind fence design shall comply with the following:
Page 71 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
a.
Wind fence design shall not restrict airflow to the burner openings and shall ensure that
sufficient amount of air is provided for all operating draught levels.
b.
Wind fence design shall acoustically dampen the noise to achieve an 85 dBA noise level or
less at a distance of 1 m (3 ft) from the wind fence with all stages of operation.
Wind fences also offer safety protection for personnel from radiation of the flare
flames and from external surfaces of the combustion chamber.
PY
The wind fence also isolates the air intake for the enclosed flame flare from the
adjacent ground level environment. Elevating the air intake can mitigate the
potential ignition of combustible ground level hydrocarbon vapour clouds. This is
an important factor if the enclosed flame flare is in close proximity to hydrocarbon
storage or processing equipment.
The inside surface of the wind fence and all components of the enclosed flame flare inside
the wind fence shall be engineered for temperatures that are experienced from the thermal
radiation of the flames visible there.
d.
Personnel access inside the wind fence of an operating enclosed flame flare shall be
restricted while enclosed flame flare is in service. Doors or manways shall be provided to
limit access to inside of the wind fence.
O
c.
C
This access is for inspection, maintenance, and repairs. Wind fences may also have
viewing ports for observation while the flare is in service. The number of doors and
viewports is selected based on inspection and access requirements and on
limitations to view and movement inside the wind fence.
Wind fence designs should comply with structural requirements as defined for the
combustion chamber. Wind fence enclosures are typically of steel and concrete.
f.
Wind fence material selection shall provide for an external surface temperature acceptable
for worker exposure.
Add
Guaranties
a.
Typically, flare vendor shall provide the following performance guarantee for enclosed
flame flare:
1.
2.
N
6.7
O
T
e.
Combustion efficiency at design flow.
Performance of flare hydraulically, mechanically, and electrically.
Capacity of flare for specified composition range.
4.
Flame stability and that flame envelope will be contained within confines of flare
chamber.
5.
Emission levels over specified operating range.
6.
Smokeless capacity for full operating range.
7.
Turndown ratio.
8.
Minimum purge gas requirement for each burner.
9.
Noise levels over specified operating range.
D
O
3.
10. Flare lining will not suffer deterioration/degradation between anticipated overhauls.
11. Noise at design flow.
b.
Guarantees shall apply to both summer and winter operation.
Page 72 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
7
c.
Recommendations for method to be used for field test to determine actual emissions rates
shall be provided.
d.
If personnel exposure could be expected, vendor shall advise whether dispersion modelling
should be performed to ensure that material release is below acceptable ground
concentrations.
Documentation
a.
Detailed operating procedure and maintenance manuals shall be developed for each flare
system.
b.
PY
Typical vendor supplied procedures and manuals are not usually sufficient because
they tend to be of a “generic” nature and, in many cases, lack plant and system
specifics for the particular application.
Operating procedure should include the following major topics:
O
ISO 25457/API Std 537 provides comprehensive operating instructions and
troubleshooting for various components of flare systems. This information and
instructions could be included in operating manuals and training manuals for
particular type of flare used in facility.
Detailed system description.
2.
Operating envelopes containing range and operating limits, describing limiting flow
scenarios and assumptions, alarms and trip set points, and required corrective actions
by the operator.
3.
Operating logs that may include data on flow to flare measurements, assisting media
flow measurements, purge gas flow measurements, and pilot operational status.
4.
Flame observation permit requirements (opacity requirements, remote camera
operation, visual observation, aviation lights status, etc.).
5.
Flare operational data required by permit (smoking severity and duration of smoking
event, venting volumes, pilot operational status report, etc.).
6.
Operator training requirements and training frequency.
D
O
N
O
T
C
1.
Page 73 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Annex D
(Informative)
Instructions for flare data sheets
Modify to Read
Introduction
This annex includes instructions for completing ISO 25457/API Std 537 flare data sheets.
The data sheets are not included in this GP but will be available as a separate document,
DS 22-200. Until the DS is available, data sheets provided in ISO 25457/API Std 537 can
be used.
b.
The flare data sheets are designed to provide a concise but thorough definition of the flare
system and its performance for new flares and can be used for the same purpose for
existing flares.
c.
For new flares, the data sheets should evolve throughout the course of a project. The level
of detail reflected in the data sheets should be consistent with the current stage of the
project. Early in a project, the sheets may contain less detail than later revisions. Some of
the fields on these sheets may remain blank if the information is not known or is not
relevant to the particular application. Users of these data sheets are encouraged to apply
reasonable judgment in determining which fields apply.
d.
Fields
PY
a.
C
O
D.1
These data sheets should become the controlling document in specifying flare
equipment.
2.
Accordingly, all parties involved with the flare, including vendors, engineering
contractors, purchasers, and end users, shall share a clear understanding of the
meaning of each field.
3.
While many of the fields are self explanatory, some require clarification beyond the
wording of the field labels.
4.
These instructions describe in more detail fields whose labels can be inadequate to
fully define their purpose.
O
N
5.
T
1.
In addition, to support the goal of defining the flare system, it is often appropriate to
append a process control diagram to the data sheets at the start of a flare project.
Data sheets are divided into groups to facilitate use. Each group of data sheet is in either SI
or U.S. conventional units. User should select data sheets with units that are appropriate for
his facility.
f.
Data sheets Form Gen 1 to Form Gen 7 set forth the general information regarding a
project and may be used for any type of flare (elevated, enclosed, etc.).
g.
Information specific to an elevated flare can be recorded on the data sheets Form Elev 1 to
Form Elev 5.
h.
Enclosed flare data belongs on sheets Form Enc 1 to Form Enc 5.
i.
A combination of “Gen” and “Elev” or “Enc” forms can be used to specify a particular
type of flare used in the flare system.
j.
The flare data sheets cover both mechanical and process aspects of flare design. Those
using the data sheets are referred to GP 44-80 and this GP for process information. The
combination of information contained in this GP, GP 44-80, and ISO 25457 provides a
broad source of information for BP user in flare applications.
D
O
e.
Page 74 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
m.
All forms have a line in the header at the top that contains Page ____ of ____.
2.
This page numbering system is an integral part of the “General notes” system.
3.
The preparer of this form is strongly encouraged to include both page numbers and
total pages on all forms.
4.
If subsequent revisions result in additional pages (such as additional gas stream or
notes pages), it is recommended to modify the page numbers by using 3A, 3B, etc.,
for gas stream pages, as an example. This avoids having to renumber all pages and
note references on Form(s) Gen 7 and prevents the confusion that can result from
renumbering errors.
5.
Changes to the total page count at the top of each page are necessary whenever pages
are added to the package.
PY
1.
Notes
All forms have a column labelled “Note”, which is intended to refer to additional
notes on one or more copies of Form Gen 7: General notes. Numbering of the notes
should start with “1” on each new page.
2.
The liberal use of explanatory notes is strongly encouraged to ensure a clear
communication of all job requirements.
3.
For example, a system using Form Gen 3 to define the flow conditions can be more
clearly described by placing a numeral “1” in the N column on line 1 or 2, even
though previous pages already contain notes.
4.
On a copy of Form Gen 7, the user would place a note referring, perhaps, to Page 3,
Note 1.
5.
The note can define normal flowrates, frequency, and duration for various streams on
that Form Gen 3, as opposed to maximum hydraulic flow or smokeless capacity
required. Such a note helps both the designer and the operator to understand how the
equipment will actually be used.
T
C
O
1.
Revisions
1.
It is expected that revisions will occur to the data sheets during the course of a
project.
All forms include one or more columns labelled “REV”, where a revision can be
marked.
O
2.
O
l.
Page numbering
N
k.
In addition, the heading section of each form contains a “revision number” field.
4.
When a set of changes is made to a set of data sheets, this set of changes is referred to
as a revision and is assigned the next revision number.
D
3.
5.
The original issue should be noted as revision zero.
6.
All changes made in a revision are marked with the same revision number.
7.
As a matter of reference, a copy of Form Gen 7 containing the revision history should
be included.
8.
Each revision note should contain, as a minimum, the revision number, the revision
date, and some description of the revision, such as “Revised per vendor quote” or
“Revised for purchase”.
9.
Additional information, such as a list of affected forms/lines, can be useful for
tracking purposes.
Page 75 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
10. Each revision should be issued as a complete set of pages, not as individual pages.
This ensures that all recipients have a complete, current set of data sheets.
D.2
General information forms - Instructions
D.2.1
Form Gen 1
Form Gen 1
Jobsite climate
Indicate type of climate, such as dusty desert, arctic tundra, or tropical
jungle. Can indicate a requirement for dust filters, freeze protection,
special radiation considerations, instrument packaging, etc.
Line 16
Local codes
State or local codes can affect electrical equipment, mechanical design,
process performance, shipping, or other aspects of a major construction
project, such as a flare system. Any regulations that can affect the
design, fabrication, delivery, construction, or operation of the system
should be identified as early in the project as possible.
Line 19
Ambient conditions
(design/normal)
Each of the conditions listed has design values and normal values.
Design values can be necessary for proper selection of metallurgy or
piping growth. Normal values can provide a better idea of conditions
that will normally prevail and can allow for certain operational
efficiencies most of the time. Provide minimum and maximum
temperatures, as they influence such items as blower design, structural
materials, and thermal growth/shrinkage.
Line 22
Relative humidity
Some radiation models allow a credit for atmospheric attenuation at
large distances. Atmospheric humidity can affect smokeless
performance, electrical circuit design, etc.
Line 24
Predominant wind
direction
If the jobsite has a very predominant wind direction, it is sometimes
possible to design the system to take this into consideration. A wind
rose can be provided if it is available. Suitable orientation of pilots, for
example, can allow longer equipment life by avoiding the predominant
flame pulldown area.
Lines 25-26
Solar radiation
Line 27
Jobsite elevation
Form Gen 2
O
C
T
Altitude of jobsite affects local atmospheric pressure, which affects
pressure drop calculations, fan sizing, etc.
O
Form Gen 2
Refer to GP 44-80 for a discussion of solar radiation allowances.
N
D.2.2
PY
Line 9
Minimum flare height
Nearby structures, electrical classification issues, independent
dispersion calculations, or BP standards can impose a minimum flare
height requirement.
Line 2
Anticipated flare
header diameter
Fields in lines 2, 3, and 4 allow the designer to estimate the flare header
volume, surface area, pressure drop, etc. These factors can affect
purge system design, peak waste gas flowrate, or actual gas
temperature arriving at the flare and other important design issues. It is
sometimes possible to anticipate transient behaviour in the flare system
that can affect overall performance. Flare header volume includes all
piping and drums that can be pressurised by a flare event, regardless of
whether the relief actually passes through that section of the flare
header system.
Line 3
Approximate flare
header length
Flare header network
volume
D
Line 4
O
Line 1
Line 5
Plot space available
This can affect selection of the support method, size of component
parts, guy wire radius, etc.
Line 11
Special erection
requirements
Plans to construct a system using gin poles in lieu of a crane, single
point lifting requirements, limited laydown areas for construction, or
preference for bolted construction are examples of special requirements
that are necessary to define early in a flare project.
Page 76 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Form Gen 2
Nozzle location and
loads
Position of the relief gas nozzle connection to the gas riser is of primary
importance to the structural and foundation design of the flare. The
minimum elevation is typically imposed by the presence of a liquid seal
and/or knockout drum. Nozzle location, unless specified otherwise,
should be 10 m (33 ft). Refer ISO 25457/API Std 537, Table 2, for
allowable nozzle forces and moments.
Line 24
Utilities available
(design/normal)
Each of the conditions listed has design values and normal values.
Design values can be necessary for proper selection of metallurgy or
piping growth, for example. Normal values can provide a better idea of
conditions that will normally prevail and can allow for certain operational
efficiencies most of the time.
Line 27
Location of steam
conditions
Steam temperature and pressure vary from one point in the steam
system to another, due to heat losses and pressure drops. It is
necessary that the designer know whether the indicated pressure is
available at the flare burner, at the base of the stack, at a point outside
a sterile radius, or at a boiler somewhere. It is necessary that the
designer also know whether the pressure and temperature are
downstream or upstream of the control valve.
Lines 28-29
Electrical power
It is important to know whether the local power supply is 50 Hz or
60 Hz, as this has a profound effect on blower motor performance. It is
necessary that the voltage be known before vendors can select
appropriate control equipment.
Line 34
Fuel gas
One of the compositions that should be defined on a copy of Form
Gen 3 is that of the fuel gas to be used for pilots, flame front generator,
enrichment gas, etc. As a minimum, it is necessary that the designer
know the MW (this needs to be shown as molecular weight [MW] or
specific gravity [SG] and LHV of the fuel gas). If the fuel gas contains
more than 10% volume fraction hydrogen, unsaturated hydrocarbons,
hydrogen sulphide, or inerts, the composition needs to be identified.
Line 35
Purge gas
Purge gas composition should be defined on a copy of Form Gen 3.
Line 38
Nearby structures
(distance, height)
Lines 39-42
Other active flares
T
C
O
PY
Lines 13-16
O
Flares are usually sized to meet a specified radiation criterion at grade.
Radiation on nearby structures, especially heat sensitive structures,
such as cooling towers, can be accounted for only if such structures are
identified and located.
Form Gen 3
D
D.2.3
O
N
If there are other flares in the vicinity of the specified flare that are
expected to be flaring simultaneously with the specified flare, these
should be accounted for in the design of the specified flare. To account
for such flares properly, some clear definition of the other flare radiation
information is necessary. Heat release and radiant fraction, as a
minimum, enable only a rough accounting. Direct information (e.g.,
isopleths from the other flare vendor) is preferred. It should be included
by reference with a note and any attachments that can be useful.
Consideration can be given to performing maintenance work on one
flare while any nearby flare is operating.
Form Gen 3
Line 2
Smokeless capacity,
opacity
Smokeless capacity is defined on the data sheets in kg/hr (lb/hr) rather
than some percentage of design flow. The smokeless capacity
requirement should be established by a thoughtful review of actual relief
scenarios. Conditions that are expected to occur often enough to
require smokeless operation, either by regulation or BP standards,
should set the smokeless requirement. Indicate the opacity or
Ringelmann number that is allowable at the flowrate for smokeless
operation.
Page 77 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Form Gen 3
Static pressure
Static pressure, in this context, is the pressure exerted by the gas on
the walls of the flare header. This pressure determines the gas density.
A conventional pressure gage mounted on the side of a pipe measures
static pressure. An additional component of pressure at the flare inlet is
the velocity pressure. The sum of these two components is called total
pressure, also known as stagnation pressure. The total pressure is a
good measure of the energy available in the flowing fluid. A properly
positioned pitot tube measures total pressure on the port facing the flow
stream. Due to the tendency for plugging, pitot tubes are not often used
for common pressure measurements. Velocity pressure can be
calculated for a given flow stream if the static pressure and pipe
diameters are known. This approach allows the use of conventional
pressure gages to check performance. This is the reason for requiring
declaration of both static pressure and diameter at the flare inlet. If BP
does not define the flare inlet diameter, the specified pressure should
be indicated as total pressure. Pressure is based on relieving conditions
as identified by different operations specified on these data sheets.
Line 6
Veq
Veq is the volumetric flowrate of air at standard temperature (15°C
[60°F]) that produces the same velocity pressure as the specified flow
stream at local atmospheric pressure and the defined stream
temperature. It is proportional to the waste gas flowrate and is
independent of the pipe diameter used to evaluate velocity pressure.
The volumetric flowrate, Veq, is given by equations (D.1) to (D.4):
O
PY
Line 4
Tgas
Mgas
C
Veq  259  qm 
Veq   normal  qm 
(D.2)
O
T
Where:
qm
=
Tgas =
Mgas =
δnormal =
Mgas Tgas

29 288
(D.1)
mass flowrate of gas (kg/hr)
absolute temperature of the gas (K)
relative molecular mass of the gas
volumetric flowrate (scm/hr)
Tgas
Mgas
(D.3)
Mgas Tgas

29 520
(D.4)
N
Veq  3,091 qm 
D
O
Veq   SCFH 
Where:
qm
=
mass flowrate of gas (lb/hr)
Tgas =
absolute temperature of the gas (Rankine)
Mgas =
relative molecular mass of the gas
δSCFH =
volumetric flowrate (scf/hr)
Veq is intended as a means to compare hydraulic performance or
requirements among flowing conditions at a fixed jobsite. If comparisons
to other jobsites at other altitudes are required, a correction should be
made for atmospheric pressure variations.
Line 8
Duration at maximum
rate
Duration of the relief can affect allowable radiation levels, noise levels,
smokeless requirements, and other aspects of the design.
Line 9
Relief source
Some indication of the relief source and its cause is useful to the
designer. A label, such as “Power failure” or “Demethaniser overheads”,
can help for communication about cases and understanding the
character of the relief.
Line 10
Controlling case for…
Indicate whether this relief case is the controlling case for pressure drop
(DP), radiation (RAD), noise (NOI), smokeless performance (SMK), etc.
Page 78 of 84
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5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Form Gen 3
Gas composition
The designer needs to know whether the specified composition is on a
mass or a molar basis to properly evaluate stream properties. Either
circle one of the options (if that option applies to all streams) or define
the basis explicitly for each stream.
Lines 12-40
Compounds
Several blank lines have been left at the end of the list to allow for
inclusion of compounds not found on the preprinted list. If necessary,
one or more of the unused compounds in the preprinted list can be
struck through and replaced with additional unlisted compounds.
Line 41
Total
Ideally, gas composition should total 100%. Compositions are
sometimes provided in the form of flowrates of each component, in
which case, the total of flowrates should match the design flow
condition.
Lines 42-48
Hydrocarbon
characterisation
information
This information is used for combustion, smoking tendency, and
hydraulic considerations.
D.2.4
PY
Line 11
Form Gen 4
Form Gen 4
Flame monitors
Indicate the number of flame monitors required and whether this count
is per pilot or per flare.
Line 9
Flame monitor type
Indicate type K (or other) thermocouples, optical, ionisation, acoustic
detectors, or as appropriate.
Line 14
Retractable pilots
This information is used primarily for enclosed flares. Indicate whether
pilots should be removable while the flare is in service.
Line 15
Retractable
thermocouples
Indicate whether pilot thermocouples should be removable while the
flare is in service.
Line 21
Distance from stack
Indicate the distance in terms of piping length from the ignition panel to
the flare stack. This can be substantially longer than simple radial
distance if the piping runs along a pipe rack.
Form Gen 5
Integral/separate
from stack
Line 10
Seal depth
Indicate whether it is required that this vessel be integral with the stack
or separate from the stack. It is often more economical to build the
vessel into the base of an elevated structure. However, high corrosion
rates or a requirement to bypass and isolate the vessel while the flare is
in service can require a separate vessel.
D
O
N
Line 4
Line 11
C
T
Form Gen 5
O
D.2.5
O
Line 8
Maximum vacuum
Seal depth determines the inlet pressure at which the first bubble of gas
flows through the vessel. Design seal depth varies, depending on the
purpose of the liquid seal. Simple maintenance of a positive upstream
header pressure can require only a few centimetres of depth. Flare gas
recovery systems often require 500 mm to 750 mm (20 in to 30 in) of
seal depth to ensure adequate suction pressure for the compressor.
Liquid seals used for staging between multiple flares can have seal
depths of 2,5 m (100 in) or more.
Flare gas recovery systems or hot gas thermal contraction and/or
condensation can result in substantial vacuums in the flare header. A
vertical section of piping in the liquid seal inlet line can allow seal fluid to
be drawn up by the vacuum without drawing air in through the flare
burner. This protects the plant against a potentially dangerous situation.
To achieve this level of protection, it is necessary to design the vessel
with sufficient liquid volume in the normal seal depth area to fill the
vertical section of piping. Safe design of this liquid volume should take
no credit for the addition of supplemental liquid. Operationally, it is
necessary to maintain the proper liquid level in the liquid seal and to
restore that level promptly after any hot relief and before the vacuum
forms. The maximum vacuum protection achievable can be limited by
piping or vessel elevations.
Page 79 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Form Gen 5
Lines 13, 17-28
D.2.6
Various connections
Each of these lines asks for a description of a vessel connection,
including the type of connection (flanged, threaded, welded), the size in
millimetres (inches), and the number of these connections.
Form Gen 6
Form Gen 6
Integral/separate
from stack
Indicate whether it is required that this vessel be integral with the stack
or separate from the stack. It is often more economical to build the
vessel into the base of an elevated structure. However, high corrosion
rates or a requirement to bypass and isolate the vessel while the flare is
in service can require a separate vessel.
Line 6
Design code
BP will specify.
Line 11
Maximum liquid level
Maximum liquid level may be defined either as a distance above bottom
tangent or as an absolute elevation. Vendor may define this value to
prevent reentrainment of accumulated liquid in the waste gas stream.
Line 12
Liquid holdup volume
BP, based on the anticipated liquid volumes that can be sent to the flare
system, may define the liquid holdup volume. Sufficient volume should
be provided to prevent overfilling of the knockout drum, which can lead
to liquid carryover to the flare burner, smoke, flaming rain, and other
hazardous conditions.
Lines 14, 18-29
Various connections
Each of these lines asks for the description of a vessel connection,
including the type of connection (flanged, threaded, welded), the size in
millimetres (inches), and the number of these connections.
O
C
D.2.7
PY
Line 5
Form Gen 7
O
T
The “Page No.” and “Note No.” columns are intended to allow all notes associated with all
pages to be collected on a single set of pages appended to the back of the data sheet package.
“Page” and “note” numbers should precede each note to indicate the location in the data sheet
package to which the note refers. Notes can be several lines long and require the “page” and
“note” references only on the first line.
Elevated-flare forms - Instructions
D.3.1
Form Elev 1
Form Elev 1
N
D.3
Sound pressure level
(SPL) at flare base
Unless specified otherwise, noise at the base of the flare is defined at a
point 1,5 m (5 ft) above grade and 10% of the flare stack height
distance from the flare stack centreline. Nearby noise sources, such as
blowers or steam control valves, should be identified and a general note
should indicate whether or not these nearby sources are included in the
noise prediction.
Lines 14-15
SPL at distance
Noise at a distance is measured 1,5 m (5 ft) above grade at the
specified distance from the flare stack centreline. Typical background
noise levels in the target area, if known, should be indicated with a
general note.
Line 27
Smokeless definition
Environmental regulations usually specify that a flare may not exceed
some opacity level for more than a certain amount of time. That opacity
level defines the smokeless criteria. An opacity level of 20%
corresponds to Ringelmann 1 and 40% to Ringelmann 2. Zero opacity is
Ringelmann 0.
D
Line 13
O
Radiation and noise performance is often specified in terms of the maximum flaring rate. Similarly, smokeless
performance specifications require smokeless operation up to some specified flowrate. In practice, it is often the
performance of the flare at rates substantially below maximum and below peak smokeless capacities that actually
determines whether the flare is acceptable to the user or the community. Some representation of these turndown
conditions can be provided as an additional gas stream on Form Gen 3. Performance expectations for these
conditions can be specified either by using one of the blank lines on Form Elev 1 or through the use of General
notes.
Page 80 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
D.3.2
Form Elev 2
Form Elev 2
In some cases, it can be necessary to add a general notes page to include any clarifications in the areas of
predicted system performance.
Static inlet pressure
Normally, this should be based on the specified flare inlet diameter
(Form Gen 3, Line 5). If vendor is proposing a different flare inlet
diameter, the proposed diameter should be clearly defined on this line,
such as “20 kPag @ 600 mm” (“3 psig @ 24 in”).
Line 11
(blank)
Some vendors provide radiation information in the form of graphical
outputs. Such outputs should be appended to the data sheets and may
be referred to here by filling in “Radiation plot” as the description and
“See attached” as the value.
Lines 13-17
Noise performance
Some vendors provide noise information in the form of tables showing
octave band breakdowns. These can be appended or included as
general notes.
Line 27
Steam to
hydrocarbon (S/HC)
ratio
Steam consumption has often been characterised in terms of mass
ratios of steam to hydrocarbon required for smokeless performance.
The value provided on this form is based on operation at or near the
smokeless capacity. BP is cautioned that the ratio necessary for waste
gas flows in the turndown range can exceed the ratio near the
smokeless capacity.
Lines 32-33
Air capacity and
pressure
Vendor should clearly indicate whether the pressure basis is static or
total pressure at the blower outlet. If static pressure is used, the outlet
area of the fan shall be indicated.
O
C
D.3.3
PY
Line 2
Form Elev 4
Form Elev 4
Loop seal depth
Line 12
Stack design
pressure
Line 13
Stack design
temperature
Some purge conservation devices, such as buoyancy seals, include a
drain to continuously remove rainfall, steam condensate, or other liquids
that can enter the seal. A loop seal, similar to that used for an API
knockout drum or liquid seal skimmer, should be used to prevent flare
gas from migrating into the drainage system. Refer to ISO 23251 for
further information on determining this depth. The required depth of this
loop seal should be defined on this line.
O
T
Line 8
N
O
D
D.3.4
BP is cautioned against excessively high design pressures, as the
combination of stack loadings from wind, earthquake, and internal
pressure can result in much thicker walls than are actually required.
If gas temperatures differ substantially from ambient temperature, a
significant heat transfer rate can exist between the waste gas and
ambient air. This heat transfer can affect stack design temperatures in
two ways. First, heat transfer to or from the waste gas while it is flowing
from the plant to the flare stack generally causes the waste gas
temperature to move closer to ambient temperature. Second, the steel
temperature is somewhere between the waste gas temperature arriving
at the flare stack and the ambient temperature. Both of these effects
should be considered in establishing the stack design temperature to
avoid overspecification. Vendor and BP can work together to specify
this temperature, if so noted on the data sheet.
Form Elev 5
Form Elev 5
Line 10
Maximum motor
current - winter
As discussed in 9.3, flare fans deliver a certain maximum volumetric
flow of ambient air to the flare burner. At minimum ambient
temperatures, the density of this air is the highest. As a result, the motor
horsepower required is highest in winter. The electrical current required
to drive the motor under these conditions usually dominates the design
requirements for the switchgear and substation that delivers this power
to the fan motor.
Page 81 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
D.4
Enclosed-flare forms - Instructions
D.4.1
Form Enc 1
Form Enc 1
Enclosed capacity
Indicate the maximum continuous flowrate that the enclosed flare needs
to handle without visible flame, excessive temperature, or noise.
Line 7
SPL at windfence
Noise at the wind fence is measured 1,5 m (5 ft) above grade at a
distance of 1 m (3 ft) from the major bounding surface at the base of the
flare. This is usually the windfence. Nearby noise sources, such as
blowers or steam control valves, should be identified, and a general
note should indicate whether or not these nearby sources are included
in the noise prediction.
Line 8-9
SPL at distance
Noise at a distance is measured 1,5 m (5 ft) above grade at the
specified distance from the flare stack centreline. Typical background
noise levels in the target area, if known, should be indicated with a
general note.
Lines 27-28
Purge gas
Staging is often used in enclosed flares to improve turndown
performance. A continuous purge is recommended to keep the flare
header swept clear and to prevent air ingression through the first stage
of burners. In many cases, a brief, relatively high purge flow is injected
downstream of each staging valve to flush out residual waste gases
after that staging valve is closed. Purge gas capacity limitations, if any
exist, should be specified by BP.
D.4.2
C
O
PY
Line 1
Form Enc 2
Form Enc 2
Lines 7-11
Noise performance
Line 12
Smokeless capacity
Line 19
S/HC ratio
Vendor should indicate maximum enclosed capacity for the specified
composition from Form Enc 1. If there are multiple flow streams, vendor
should indicate maximum enclosed capacity for each stream as a
general note. Any discussion relating to the interpretation of enclosed
flaring should be included as a general note.
T
Enclosed capacity
Some vendors provide noise information in the form of tables showing
octave band breakdowns. These can be appended or included as
general notes.
O
Line 1
O
N
Vendor should indicate smokeless capacity for the specified
composition from Form Enc 1. If there are multiple flow streams, vendor
should indicate smokeless capacity for each stream as a general note.
Steam consumption has often been characterised in terms of mass
ratios of steam to hydrocarbon required for smokeless performance.
The value provided on this form is based on operation at or near the
smokeless capacity. BP is cautioned that the ratio necessary for waste
gas flows in the turndown range can exceed the ratio near the
smokeless capacity.
Purge gas
Vendor should indicate both the continuous purge requirement and the
maximum intermittent purge flow requirement during staging operations.
Line 33
Supplemental gas
If supplemental fuel gas is used to maintain a minimum temperature in
the firebox, vendor should indicate the flowrate necessary in cold
weather.
D
Lines 27-28
D.4.3
Form Enc 3
Form Enc 3
Lines 21-29
Firebox and
windfence
dimensions
Most enclosed flares fall into one of the following shape categories:
rectangular, round, or polygonal. BP should indicate any preferences
regarding shape. Vendor should indicate selected shape and
associated dimensions.
Line 30
Refractory material
BP should indicate any requirements or limitations on refractory
material.
Line 32
Maximum service
temperature
Vendor should indicate service temperature of the proposed refractory.
Page 82 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Form Enc 3
Maximum shell
temperature
Vendor should indicate expected shell temperature for ambient
conditions of 27°C (80°F) and still air. This calculated temperature is
used to select the paint system for the outside of the firebox. BP should
indicate hot face temperature basis for calculation as either maximum
allowable temperature for the refractory or calculated operating
temperature at the enclosed flaring capacity. Significant cost savings
can accrue with the use of a lower hot face temperature basis.
Line 35
Maximum expected
flue gas temperature
Vendor should indicate expected flue gas temperature for ambient
conditions of 27°C (80°F) and still air.
Line 39
Maximum personnel
exposure
temperature
Vendor should indicate the maximum temperature on any surface
where personnel exposure can occur. This is often limited to the outer
windfence surface if access to the upper stack platforms is not
necessary during maximum operation.
D.4.4
PY
Line 33
Form Enc 4
Form Enc 4
Heat shielding
If air assisted burners are used, BP should indicate any preferences for
either a large, single blower with distribution by manifolds and valves
versus individual blowers for various stages or sections of burners.
Vendor should indicate proposed/actual method for distributing air. Use
general notes, if necessary, to clarify the issue.
C
Lines 19, 25,
31, 37
D.4.5
Any material or equipment with a view of the burner windows can be
exposed to high heat radiation. Heat shielding is often used to reduce
metallurgical requirements and piping stresses.
O
Line 4
Form Enc 5
Form Enc 5
Line 11
Supplemental
requirements
Vendor should indicate whether any air dampers/valves are modulated
(based on temperature or flow), automatically opened/closed, or
manually set.
T
Damper control
required
BP should indicate the existence of any special requirements for the air
blowers, such as explosion proof motors or inlet filters.
D
O
N
O
Line 5
Page 83 of 84
GP 22-20
5 October 2010
Flare Details for General Refinery and Petrochemical Service (ISO 25457 or API 537)
Bibliography
Add
BP GIS 22-201, Flare Details (API 537).
[47]
BP GIS 52-101, Insulation.
[48]
BP GIS 72-101, Fluid Catalytic Cracking Unit Refractory Details.
[49]
BP GIS 72-102, Vee Anchoring Systems.
[50]
BP GIS 72-103, Hex-Mesh Anchoring Details.
[51]
BP GP 22-10, Fired Heaters.
[52]
BP GP 30-35, Control Valves and Pressure Regulators.
[53]
BP GP 42-10, Piping Systems (ASME B31.3).
[54]
BP GP 44-10, Plant Layout.
[55]
BP GP 46-01, Pressure Vessels.
[56]
BP GP 62-01, Valves.
[57]
API Publ 931, Manual On Disposal Of Refinery Wastes.
[58]
U.S. Department of Energy (DOE) guidance notes “Offshore Installation: Guidance on Design and
Construction”.
[59]
UK Clean Air Act 1956.
D
O
N
O
T
C
O
PY
[46]
Page 84 of 84
GP 22-20
5 October 2010