On an offshore platform in the Gulf of Thailand, a maintenance foreman pointed to a section of steel grating on the cellar deck and said something that stuck: "That grating has been there 8 years. We've painted it 3 times. Every time we paint, we find more rust underneath. Next time, it comes out."
Oil and gas facilities — offshore and onshore — run on a demanding maintenance equation. Salt spray, hydrocarbon exposure, and fire safety requirements intersect in ways that few walkway materials can satisfy simultaneously. FRP has been earning its place in that equation, but the specification path is different from chemical plant service. Here, fire performance and non-sparking behavior enter the conversation with equal weight to corrosion resistance.
The offshore environment: corrosion without reprieve
An offshore platform is a steel structure in salt water. Every metal component above the splash zone is in a marine atmosphere — salt-laden air with relative humidity that rarely drops below 75%. The corrosion rate on unprotected carbon steel in this environment runs 0.1–0.3 mm per year, accelerating at crevices, under gaskets, and where coating systems have been mechanically damaged during installation.
FRP walkways on offshore platforms typically appear in three zones:
- Cellar decks and wellbay areas: The lowest occupied deck level, exposed to wave spray and salt-laden wind. Steel grating here is the first to show corrosion. FRP grating in these locations has been documented in service for 12+ years on North Sea platforms without section loss.
- Pipe rack and equipment access walkways: Continuous walkways along process pipe racks, providing operator access to valves and instruments. The combination of salt atmosphere and process heat makes these routes high-maintenance in steel.
- Accommodation module external walkways: Escape routes and external access around living quarters. Fire performance requirements here can be stringent, especially where walkways serve as muster-point access.
Fire-rated grating: when the walkway is also an escape route
Not all FRP grating is created equal for fire performance. Standard polyester or vinyl ester FRP grating will burn when exposed to a sustained flame — it's a polymer, after all. For applications where the walkway serves as a designated escape route or is located in a fire hazard zone, phenolic FRP grating enters the specification.
Phenolic resin is fundamentally different from polyester and vinyl ester. When exposed to fire, phenolic resin chars rather than igniting, forming a carbon layer that insulates the underlying material and emits minimal smoke and toxic fumes. Phenolic FRP grating achieves ASTM E84 flame spread index ≤ 25 and smoke developed index ≤ 50, and meets the IMO FTP Code requirements for marine applications including low flame spread, smoke density, and toxicity criteria. This is the grating specified for helicopter landing zones, muster areas, and primary egress routes on offshore installations where personnel safety during a fire event is non-negotiable.
The trade-off: phenolic grating has lower mechanical strength than equivalent polyester or vinyl ester grating — typically 70–80% of the flexural strength — and is more brittle. It's also more expensive. The specification is therefore selective: phenolic where fire rating is mandatory, vinyl ester or isophthalic polyester everywhere else.
Non-sparking: the overlooked safety property
In Class I Division 2 locations — areas where flammable gases or vapors may be present under abnormal conditions — steel walkways present a spark hazard if a dropped tool or dragged equipment creates a metal-to-metal impact. FRP grating doesn't spark on impact. It's a material property, not a coating, so it can't wear off. For walkways around gas compressors, hydrocarbon pumps, and LPG storage areas, this property matters in the hazard analysis.
Typical configurations in oil and gas service
| Parameter | Offshore Typical | Onshore (Refinery/Gas Plant) Typical |
|---|---|---|
| Grating type | Molded FRP, 38 mm, phenolic (fire zones) or vinyl ester (general) | Molded FRP, 38 mm, isophthalic polyester or vinyl ester |
| Load class | 4.8 kN/m² (100 psf) standard; 7.2 kN/m² (150 psf) in laydown areas | 4.8 kN/m² (100 psf) standard |
| Support structure | Pultruded FRP I-beam or existing steel structure with isolation pads | Pultruded FRP or galvanized steel with FRP isolating washers |
| Fasteners | 316 SS or FRP clips, Type 316 saddle clips for phenolic | 316 SS or FRP grating clips |
| Handrail | FRP pultruded tube, 1,100 mm top rail height | FRP pultruded tube or galvanized steel per project spec |
| Non-sparking | Inherent (all FRP) | Inherent (all FRP) |
| Weight | 15–30 kg/m² (3–6 psf) | 15–30 kg/m² (3–6 psf) |
| Design standard | ISO 14122, NORSOK C-004, IMO FTP Code | OSHA 1910.22, ASTM E84 |
"Replacing the steel grating on the cellar deck with FRP eliminated a 3-year coating cycle and removed 14 tonnes of topside weight. The phenolic grating on the helideck access walkway passed its fire integrity review without additional coatings."
This page describes where FRP walkways are used in oil and gas facilities. For broader industrial walkway context, see FRP Walkway Systems — Industrial Applications. For fire-retardant design strategies, see Fire Retardant Systems.