Warning to offshore industry on possible failure of fire resistant composite deck gratings
Health and Safety Executive - Safety alert
Hazardous Installations Directorate - Offshore Division
2 October 2012
This alert is to warn operators that fire resistant composite materials, especially FRP deck gratings, used offshore may fail, or lose integrity, after exposure to relatively short duration hydrocarbon pool fires. The time taken for this is considerably shorter than the specified resistance period of 60 minutes derived from the certifying test for cellulosic fires. Duty Holders must determine whether composite gratings are used in areas with potential hydrocarbon fire exposure and identify means of ensuring the safety of personnel should they walk on weakened gratings.
This Safety Notice is being issued a result of investigations by the Health and Safety Executive into the consequences of exposing Fibre Reinforced Plastic (FRP) deck gratings to hydrocarbon pool fires. These gratings are commonly used by the offshore industry as a result of their apparent advantages over steel gratings and factors such as fire resistance certification, light weight and improved environmental resistance.
At present FRP deck gratings are certified against US Coast Guard specifications PFM 2-98 and NVIC 9-97-CH1, which employ a combination of load tests and a 60 minute 'fire' exposure to a test furnace to mimic the heat profile of a cellulosic, rather than a hydrocarbon fire. Cellulosic fires have slow growth times and may reach a temperature of 880 ºC after 60 minutes, compared to hydrocarbon fires which can, typically, reach temperatures around 1100 ºC in significantly less time. Hydrocarbon jet fires will produce even higher temperatures within even shorter impingement times. Tests by the Health & Safety Laboratory (HSL), on behalf of HSE, have determined that certain types of FRP gratings based on a glass reinforcement embedded in a phenolic or isophthalic resin, may lose their load-bearing capabilities or fail after exposure to hydrocarbon pool fires. The tests show that the fire duration required for this failure or weakening is substantially shorter than for cellulosic fires against which the composite materials were certified.
These tests also identified the possibility that the grating may appear to have retained its integrity post-fire, but may actually have insufficient strength to support the dynamic loading arising from persons walking/running over it.
Duty Holders must identify whether composites are used in areas where they may be exposed to hydrocarbon fires. If so, Duty Holders must establish means of ensuring, in consultation with manufactures or suppliers, that sufficient integrity will remain for their safe use.
Relevant legal documents:
- The Health and Safety at Work etc. Act 1974, Sections 2 and 4.
- The Offshore Installations and Wells (Design and Construction etc.) Regulations, 1996, Regulation 5.
- Offshore Installations (Prevention of Fire and Explosion, and Emergency Response) Regulations, 1995, Regulation 5.
- Preliminary Fire Testing of Composite Offshore Pedestrian Gratings, G Burrell, S F Jagger and D Johnson, Health and Safety Laboratory internal report, FP/12/27
- US Coast Guard Navigation and Vessel Inspection Circular 9-97, Guide to Structural Fire Protection
- US Coast Guard Policy File Memorandum on the use of Fibre Reinforced Plastic (FRP) gratings and cable trays, PFM 2-98
Hazardous Industries Division
Health and Safety Executive
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