- 6.3.1 Equipment Supporting Structure
- 6.3.2 Vessel / Equipment Supports
- 6.3.3 Pipe Racks and Pipe Supports
- 6.3.4 Air Coolers
- 6.3.5 Fired Heaters
- 6.3.6 ESD/BDV Valves and Actuators
- 6.3.7 Cabling
- 6.4 Fire Rating
- 6.5 Critical Temperature
- 6.6 Fireproofing Design Execution
The purpose of this design guide is to outline the recommended workflow and design basis for Fire Proofing requirements on EPC projects. This document will also identify the multidisciplinary action to develop the fireproofing document for site to implement the fireproofing.
This design guide is to be applied for development of Fire Proofing Schedule and Layout for hydrocarbon handling facilities. The workflow and responsibility of engineering disciplines shall be followed for all EPC projects. The design basis is to be adopted in the absence of client’s specific fire proofing basis for a project.
|Vessels, Pumps, Air coolers, Compressors, Heat exchangers, Fired heaters and similar equipment containing flammable or combustible materials. For
details refer to 6.1
|A three dimensional region that is horizontally within a specified distance of any Fire Potential Equipment and is vertically within a distance above any level at which a fire may be initiated.|
|Standard Fire Test||A test whereby the temperature attained at a certain time after the commencement of a fire can be assigned a specific value based on the standard time-temperature curve as included in BS 476 Part 20.|
|Jet fire||A turbulent diffusing flame, resulting from the combustion of a steady release of pressurized liquid or gaseous fuel. It constitutes the most severe fire scenario due to the effect of erosion as well as the significantly higher rate of burning due to turbulent fuel/air mixing.|
|Pool fire||A fire in which the material(s) of combustion is essentially hydrocarbon in nature. It can result in a more rapid rise of the time-temperature curve and a higher initial thermal shock than in a Standard Fire Test. Appendix D of BS 467-Part 20 (1987) provides guidance on the time-temperature relationship for such fires.|
|As per IP 15 petroleum liquid is classified as flammable if it has a flash point upto and including 55oC. For this guide flammable liquid is defined as any liquid whose
-Flashpoint ≤ 55oC OR
-Flashpoint < (higher of operating temperature or
maximum ambient temperature) + 5oC.
API – American Petroleum Institute
BDV – Blowdown Valves
BS – British Standard
CMPT – Centre for Marine and Petroleum Technology
EPC – Engineering Procurement and Construction
ESD – Emergency Shutdown
ESDV – Emergency Shutdown Valves
F&G – Fire and Gas
GA – General Arrangement
H2S – Hydrogen Sulphide
HLL – High Liquid Level
HSE – Health, Safety and Environment
IEC – International Electrotechnical Commission
ISO – International Organization for Standardization
MT – Metric Tonne
NFPA – National Fire Protection Association
NLL – Normal Liquid Level
OGP – International Association of Oil & Gas Producers
PFP – Passive Fire Protection
PFP – Passive Fire Protection
ppm – parts per million
UK HSE – United Kingdom Health and Safety Executive
UKOOA – United Kingdom Offshore Operators Association
Relevant standards/specifications that are frequently employed for the fireproofing of oil and gas facilities are as under:
1. BS 476 – Part20-24, 1987: Test Methods and Criteria for the Fire Resistance of Elements of Building Construction.
2. API 2218: Fireproofing Practices in Petroleum & Petrochemical Processing Plants
3. API 2510: Design and Construction of LPG Installation (Section 10.7)
4. NFPA 30: Flammable and Combustible Liquids code
5. NFPA 58: Liquefied Petroleum Gas code
6. Loss Prevention in the Process Industries by F P Lees, 2nd edition, 1996
7. A guide to Quantitative Risk Assessment for Offshore Installations by JohnSpouge, CMPT 1999
8. Methods for the calculation of physical effects, CPR 14E, TNO, 2005
9. PEC-EN-STN-S-3847 Rev.0, Fire proofing vertical extent drawing
10. Report No. 27.207.291/R1- version2, SCANDPOWER: Guidelines for the protection of pressurized systems exposed to fire.
11. Report no 434-15, March 2010, OGP Risk Assessment Data Directory:
Vulnerability of Plant and Structures,
12. ISO 13702, Petroleum and natural gas industries — Control and mitigation of fires and explosions on offshore production installations — Requirements and guidelines
13. UK HSE Research report no. 285, 2005, Protection of piping systems subject to fires and explosions
14. UKOOA Fire And Explosion Guidance Part 2: Avoidance and mitigation of fires,Final Draft, Feb 2006.
15. PEC-EN-GDE-S-5436, Scope Matrix – Fire Proofing Design
17. PEC-EN-WIN-L-11200, Stress Analysis of Piping Systems, Rev 0
18. IP 15 Area classification code for installations handling flammable fluids, 3rdedition, July 2005
5.0 RESPONSIBILITY & AUTHORITY
The Lead HSE Design Engineer is required to notify the Project Engineering Manager/Proposals Manager of the need to adopt the design guide for a certain project, and ensure that the Project Management notifies the client of the same.
HSE Design Engineer is responsible for preparing the fire proofing schedule and fireproofing layout. Piping Engineer is responsible for modeling the fire proofing envelope in the 3D model. Responsibility of material specification for fireproofing lies with Metallurgy. Civil Engineer will be responsible for application offire proofing design in the detailed engineering documents, MTO etc. Scope split between the disciplines are given in PEC-EN-GDE-S-5436, Scope Matrix – FireProofing Design document.
Responsibility matrix for detailed fireproofing activities is shown in Appendix 1.
Fireproofing is provided for the protection of the structures that supports significant hydrocarbon inventories, emergency systems or heavy loads that, if they were to fail, would lead to significant hydrocarbon release or damage to emergency system.
Fire proofing is applied on the surface of the steel structures as steel fails due to excessive heat from a nearby fire incident. Fireproofing thickness is based on the fire rating duration and the failure temperature of the substrate material. Fire rating duration will depend on the applicable standards, emergency evacuation time, time for the firefighters to reach site and time to complete the depressurization.
Combination of prescriptive and risk based design approach shall be employed to identify the fire potential equipment and the extent of fire exposed areas on a facility.
API recommended guidelines 2218 should be followed for developing Passive FireProtection (PFP) designs. This standard addresses mainly liquid releases and PFP requirements associated with the liquid pool fire. API RP 2218 does not give a clear guideline on fireproofing requirement for jet fire. However, API standard also states that determination of fireproofing should involve risk-based evaluation and assessment of the probability of an incident materializing. API RP 2218 is under the revision now and the draft version of the revision also does not suggest to provide fireproofing against the jet fire. Therefore, Company’s approach on fireproofing, based on international practices, is to follow the API RP 2218 for pool fire and undertake a risk-based assessment as explained in Section 6.2 in order to identify the extent of PFP for jet fire scenarios.
6.1 Fire Potential Equipment
Based on the API standard and industry practices [Ref. 10] following equipment are considered as Fire potential equipment on hydrocarbon handling facilities:
Pumps with a rated capacity of over 45m3/hr that handle flammable liquids or combustible liquids above or within 8oC of their flash point temperatures.
Air Coolers handling flammable liquids. Air cooler handling gas alone will not be considered as fire potential equipment.
Vessels, heat exchanger (including air cooled exchangers) and other equipment containing flammable or combustible liquids over 315oC or their auto-ignition temperature, whichever is less.
Compressor, together with related lube-oil system.
API RP 2218 suggests liquid inventory need to be considered for identification of fire potential equipment. Based on the industry practice, equipment containing hydrocarbon liquid inventory more than 4 MT are to be considered as fire potential for the pool fire based fireproofing. For cases where jet fire to be considered for fireproofing, the equipment containing flammable gas inventory more than 1 ton[Ref.10] is considered as fire potential. While considering the gas inventory the entire inventory within the isolatable section need to be considered. For liquid inventory, it is only the individual equipment liquid inventory to be considered. If the liquid inventories are connected then the sum of the connected liquid inventories to be considered, for example, when of re-boiler is connected to the lower part of the vessel.
The liquid inventories are calculated based on equipment size and normal liquid level (NLL) values of the respective equipment. If the liquid level is not controlled by control valve and the pumping out of the liquid is based on intermittent operation or manual operation then high liquid level (HLL) shall be considered for the inventory calculation.
6.2 Fire Scenario Envelope
6.2.1 Pool Fire
Extent of fire scenario envelope is based on API 2218 recommendations and time to burn the liquid inventory within the pool. API suggests an extent of 6-12 m radius for pool. Industry guideline [Ref. 11] suggests a vulnerability criterion of 5 minutes for steel supports against fire. Considering the average burning rate for hydrocarbon liquid (Crude 0.045-0.06 kg/m2s, Condensate 0.1 kg/m2s), 9m radius pool will burn out about 4 MT of hydrocarbon in 5 minutes. Therefore any areawithin 9m from the Fire Potential Equipment is identified as the horizontal extentof a fire scenario envelope based on pool fire. Within such envelope, fire proofing shall be provided for equipment supporting structures.
As per API 2510 [Ref. 3] fireproofing is required for pipe supports within 15 m of the LPG vessel, or within its spill containment area. This is applicable only to theLPG storage and loading area.
The released flammable liquid from a storage tank may be contained within bundprovided around the storage tank. The area within bund or 6m from the tankwhichever is larger will be considered as fire scenario envelope.
6.2.2 Jet Fire
In the gas plants 80% of leaks are from gaskets and flanges; which are equivalent to3-6mm leak sizes depending material and operating conditions. Therefore apply10mm leak size for jet fire cases. It is not cost effective to consider the remaining20% as cost of mitigation is disproportionate to the benefits. Therefore the firescenario envelope in case of jet fire shall be the flame length from a 10mm holeleak using suitable consequence modelling software. The vertical extent of firescenario envelop can be considered as 9m which takes account of approximately80% of release direction in the vertical plane.
6.3 Fire Proofing Requirement
Fireproofing shall be provided only for the equipment supporting structures if theyare within the fire scenario envelope. The fire scenario envelope can be due to itsown envelope or due to the adjacent hydrocarbon equipment.
6.3.1 Equipment Supporting Structure
Steel structures supporting fire potential equipment located within a fire scenarioenvelope shall be fireproofed upto the highest level at which the equipment issupported. Vertical, horizontal and diagonal bracing members in the structure thatcontributes to the support of vertical loads shall be fireproofed.
If a non-fire potential equipment having gross weight more than 10 MT and itssupporting structure is within the fire scenario envelope then the vertical,horizontal and diagonal bracing members supporting vertical loads shall befireproofed up to 9m above grade.
For air coolers refer to Section 6.3.4.
6.3.2 Vessel / Equipment Supports
Exterior surfaces of skirts supporting towers or vertical vessels within fire scenarioenvelope, containing hydrocarbons, shall be fireproofed. Consideration should alsobe given to fireproofing interior surfaces of skirts if there are flanges or valvesinside the skirt, or if there are unsealed openings exceeding 600mm equivalentdiameter in the skirt.
Brackets or lugs used to attach vertical reboilers or heat exchangers to towers ortower skirts should be fireproofed. The earthing lug should be kept clear of thefireproofing.
Elevated exposed legs supporting towers or vessels shall be fireproofed to their fullload bearing height.
Steel saddles supporting horizontal exchangers, condensers, drums, receivers andaccumulators that have diameter greater than 750mm and located within a fireexposed envelop shall be fireproofed, if the narrowest vertical distance betweenthe concrete pier and the shell of the vessel exceeds 300mm. At sliding saddlelocation the fireproofing shall be provided such that sliding plates are not affectedby the fireproofing.
6.3.3 Pipe Racks and Pipe Supports
Pipe rack and pipe support, within the fire scenario envelope, which supportshydrocarbon carrying pipes greater than 6 inches, essential duties lines such asflare, relief, blowdown, firewater lines and ESD cables or pipe containing toxicfluid (H2S more than 500 ppm), shall be fireproofed.
Further details on the fire proofing for the supports designed by Piping group aregiven in Section 6.52 of PEC-EN-WIN-L-11200, Rev 0, Stress Analysis of PipingSystems. Fireproofing for the structural supports is identified in the structural GAand the erection drawing (xSteel) drawings.
Vertical, horizontal, knee and diagonal bracing members of the pipe rack thatcontributes to the support of vertical loads or to the horizontal stability ofstructure located within the fire-scenario envelope shall be fireproofed up to 9mabove grade. Knee and diagonal bracing or non-load-bearing stringer beams thatrun parallel to piping that is used only for wind, earthquake, or surge loading neednot be fireproofed. In case of flare line supports the bracings used to support thehorizontal pipe load due to the flare fluid movement shall be fireproofed.
Individual pipe supports including trunions for supporting the hydrocarbon pipesmore than 6 inches shall be fireproofed upto 9m.
All members, except horizontal beams, shall be coated on all sides. Beams shall beprotected on three sides with the top of the beam normally left uncoated.
If air fin-fan coolers for flammable liquid are installed on top of a pipe rack withina fire scenario envelope, fireproofing should be considered for all vertical andhorizontal support members on all levels of the pipe rack including supportmembers for the air fin-fan coolers, regardless of their elevation above grade
6.3.4 Air Coolers
Air coolers within the fire scenario envelope which handle flammable liquids shallhave all vertical and horizontal support members fireproofed up to the base of thecooler regardless of their elevation above grade.
Fire proofing is required for the support structure of air coolers which handlehydrocarbon gas if it is within fire scenario envelope. The vertical extent for fireproofing is 9m from grade.
6.3.5 Fired Heaters
Where common stacks handle flue gas from several heaters, structural memberssupporting ducts between heaters and stacks shall be fireproofed, if it is within thefire scenario envelope.
6.3.6 ESD/BDV Valves and Actuators
If the Emergency Shut Down Valve (ESDV) body is certified as fire safe, fireproofing is not required for the valve body. The actuator vendor normally confirmsthe maximum governing temperature (which is typically 85oC since soft parts areused), hence the fire proofing vendor shall accordingly design the fireproofing toensure that the actuator and the other components are within the temperaturelimits specified by the actuator vendor. Actuating system shall be fireproofed forthe duration (typically 30 minutes) specified in the fire proofing specification orstudy.
Blow down valves (BDVs) body shall be of fire safe design and their actuatingsystems (including air back up system, tubing etc.) lying within a fire scenarioenvelope shall be fireproofed. The duration of fire rating depends on the durationof sequential blow down as the blow down valve’s time to start opening dependsupon its position in the blow down sequence.
All critical cabling, power supply cabling and instrument cabling for ESD, F&G and emergency communication systems shall be fire resistant to IEC 60331. However, ESD cables laid underground may not be fire resistant, provided theportions of such cables which are above the ground are provided with fire proofinginsulation.
Similarly, cables for blow down valves may not be fire resistant if the blow downsystem is intended for simultaneous blow down. In case client’s specification calls for non-fire resistant cables for ESD function then the same to be followed. This is considered from fail safe point of view.
Cable trays running on fireproofed pipe-rack or any other fireproofed cable wayneed not be fireproofed if the cable tray is adequately supported by thefireproofed structures so that the cables running on the tray are not expected tobe snapped in case of damage of cable tray due to fire. However this shall bereviewed during detailed engineering.
6.4 Fire Rating
Actuating system for ESDV and BDV shall be minimum 30 minute fire rating. BDVactuating system can be higher fire rating depend on the time required for thesequential blow down.
6.5 Critical Temperature
The critical temperature (core temperature) is the temperature at which yieldstress is reduced to the minimum allowable strength under operating loadingconditions. Fire proofing material thickness is designed based on the Criticaltemperature. For structural steel the critical temperature shall be 400OC2 based onthe recommendations given in ISO 13702 [Ref. 12] and UK HSE guidance [Ref. 13].
Actuating system for ESDV and BDV fire proofing thickness will be based on thedesign temperature of the actuating system as the core temperature.
6.6 Fireproofing Design Execution
HSE Design shall prepare the fire proofing study report which contains the basis offire proofing, list of fire potential equipment, extent of fireproofing, identificationof technological structure within fireproofing envelope, list of equipment whosesupporting structure required to be fireproofed.
HSE design also prepare the fire proofing drawings shall reflect the horizontalextent of the fire proofing around Fire Potential Equipment. The fire scenarioenvelope as defined in Section 6.2 shall be marked from the edge of theequipment. The fire proofing envelope thus marked provides the horizontal extentof fireproofing. Drawings for vertical extent of fireproofing can be developed usingRef.9. This document shall be used as an input for 3D modelling of fire scenarioenvelope.
Civil Engineering shall prepare the individual structural GA and sectional details toidentify each member that require fire proofing. The fire proofing member shall be prepared in unique colour code or hatching to clearly identify which members arefire proofed and whether it is fireproofed in all four sides or three sides. Thisdrawing shall be used by the site subcontractor for applying fireproofing at site.
In addition Civil Engineering will also prepare the miscellaneous support detailswhere individual pipes supports that required fireproofing will be identified. Thiswill be consolidated report considering secondary supports provided by piping.
Piping department will model the fire scenario envelope based on the fire proofingdrawings prepared by HSE Design. This envelope will be linked to the fireprotection equipment and any movement of the fire potential equipment will leadsto the movement of fire scenario envelope. Isometrics generated by Piping willclearly indicate the supports that require fireproofing.Mechanical will include the fireproofing requirement for the supports in theequipment datasheets. The datasheet will also state the different primer to beused for the fire proofing area and non-fireproofing area of vessel or equipment.
Metallurgy will prepare the fireproofing material specification which will identifythe type of fireproofing material, thickness for fire proofing material and primerfor the fireproofing material.
Instrumentation will prepare the cable specification and actuator specificationwhich is suitable for fire and also identify the valves within the fire scenarioenvelope which require fireproofing for its actuators.
Appendix 1- Fireproofing Activity and Responsibility Matrix
|Definition of Fire proofing basis||
|Preparation of Fireproofing layout||
|Communication of horizontal and
vertical extent of fireproofing to
|Finalization of fireproofing
|Modeling the fireproofing
envelope in 3D Model
|Piping Designer will work under guidance of HSE Engineer|
|Modeling the fireproofing on
|Review of fireproofing on 3D
|Identification of piping supports
|Fireproofing marking on vessel
|Identification and procuring
fireproofing for valve actuator
|Communication of changes in
Fireproofing extent after issued
for Design to all affected
|Consolidation of fireproofing