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The post-fire integrity of pultruded phenolic/glass and polyester/glass floor gratings, of the type used offshore and elsewhere, was investigated. The aim was to determine whether glass/phenolic gratings may be safely walked on, post-fire, by offshore workers and fire-fighting teams. The load to be resisted was identified as equivalent to a running person carrying a load, the combined mass being 150 kg. The maximum resulting dynamic strains were determined by strain gauges on the undersides of the individual beam elements of gratings. This enabled target values of post-fire bending resistance to be identified. Individual beam elements from the gratings were exposed to heat fluxes of 12.5, 37.5 and 100 kW/m2 using a propane burner, for periods up to 16 min, after which the residual strength was measured. Phenolic gratings showed longer ignition times, with lower flame and smoke emission, as well as greater post-fire strength compared to polyester ones. At the lowest flux, 12.5 kW/m2, all gratings remained serviceable beyond 16 min. At higher heat fluxes, the phenolic gratings retained some post-fire strength, assisted by the formation of a carbonaceous char binding the fibres. However, this was somewhat below the target level. A study of the effect of testing speed indicated that fire-exposed gratings are not especially strain-rate sensitive.

In parallel to studies by the HSE resulting in the issuing of a Safety Alert warning to the offshore industry on possible failure of fire resistant composite gratings (Bulletin No: HID 2-2012), a study was made by MMI Engineering in conjunction with Newcastle University into the post-fire integrity of phenolic and polyester FRP gratings to determine whether such gratings can be safely used following exposure to fire. Firstly the range of weights of offshore workers was established. The recommended residual strength required for post-fire use should exceed the load generated by a running person, at the upper 5-percentile of the weight spectrum, carrying fire fighting or rescue equipment. This load includes a dynamic amplification factor to allow for the effect of running, additionally a further safety factor is required to account for fatigue effects. Samples of gratings were tested to determine the stresses resulting from running or walking by applying strain gauge instrumentation to individual beam elements of gratings to measure the strains produced. The strain gauge study was augmented by modelling to quantify the relationship between applied load and local strains. These strains were found to depend on the ‘footprint’ area over which the load was applied. Fire exposure tests involved using a propane burner to expose individual beam elements to three heat fluxes of 12.5kW/m2, 37.5kW/m2 and 100kW/m2 as well as jet fire testing at ~250kW/m2 representing the full range of fire types considered on oil and gas installations. The duration of the fires were increased in increments up to 16 minutes to establish the rate of deterioration. This paper presents the results of the testing, provides information to operators on where these materials can be safely used as well as providing grating manufactures with guidance on future product testing and development to produce more fire resistant systems.