Three themes at an LNG terminal

Grating selection at an LNG terminal turns on three themes: cryogenic spill, fire and smoke, and coastal corrosion. They sometimes conflict, because a fire-retardant resin is often less chemical resistant and less tough than a standard resin, so the choice has to balance them.

The first theme is cold. LNG boils at about minus 162 degrees Celsius at atmospheric pressure, and a spill chills the grating locally; whether the material cracks depends on the resin, its moisture content and the cooling rate, so ambient data cannot answer the question.

The second theme is fire. A terminal is laid out in fire zones, and the grating has to meet the project's flame spread, smoke and burning drip requirements. The third is salt spray and UV, because most terminals sit on the coast and the grating lives in damp, salty air.

How the material reacts to a cold spill

FRP is a composite of resin and glass, and the two have very different thermal expansion. On sudden cooling the resin contracts faster than the fibre, which puts shear stress on the interface; the sharper the gradient and the faster the cooling, the higher the stress, and the surface resin cracks first.

Water absorption is the key variable. Grating in damp air takes up a little moisture, which freezes and expands at low temperature and prises resin from fibre. Cold duty needs a low-absorption resin and data on cold, wet behaviour.

The grating does not contain the LNG; its job is to survive the cold environment after a spill and to keep escape routes usable. The design has to define the spill scenario, whether splash, pooling or vapour cloud, because each gives the panel a different temperature and duration.

Cold and wet slip often arrive together, and surface choice is covered under choosing anti-slip FRP grating

Fire, smoke and dripping

Fire requirements at an LNG terminal are usually stricter than on a general platform. Projects cite ASTM E84, EN 13501 or GB and set limits for flame spread, smoke class and burning drips, with figures from the fire documents and local code.

Fire-retardant resins use additives or phenolic. Phenolic gives low smoke and little dripping but is brittle and dark; additive polyester is cheaper, yet the additive can migrate in damp service, so the maker's aged data matters.

Grating is an open member, and smoke passes through the grid more freely than across a solid plate. Cable trays, pipe insulation and the underside of the grating can all collect combustible material, so fire design cannot rest on the panel rating alone.

Static and earthing

LNG vapour mixed with air sits in the explosive range, so static is an ignition source that must be controlled. Ordinary FRP grating is an insulator with high surface resistance, and charge from walking or tool friction does not drain away, so earthing and anti-static measures are needed.

Two routes are common: a grating with lower surface resistance, or an earthing conductor bonded to the site earth grid. Anti-static grating relies on conductive filler or a coating, and its effect falls with wear and contamination, so test it regularly.

Earthing should not rely on one point. Long walkways and multi-level platforms need sectioned bonding between metal plates, handrails and supports, with joints locked, protected from corrosion and restored after maintenance.

The electrical and earthing practice at a terminal has much in common with the power industry, and the options are set out under FRP grating for power and utilities

Coastal air and corrosion

Most LNG terminals stand near a port, where salt spray, damp and UV arrive together. The grating surface crystallises and chalks, and fasteners and supports usually corrode before the panel itself, so they are inspected together.

LNG carries no electrolyte and does little chemical damage to the resin; the long-term attack comes from sea mist, rain and wash water. Choose the resin for coastal air and occasional chemical contact, not strong acid or alkali, but not the cheapest orthophthalic grade either.

Stainless fasteners can pit in chloride and galvanized parts rust and stain the panel. Fastener, hold-down plate and support materials have to be considered together, with an isolating barrier at each contact, as described under FRP grating fasteners and installation

Offshore platforms meet the same salt spray and steel connections, and their fixing detail is summarised in FRP grating for marine environments

Loads on pipe racks and platforms

Pipe rack platforms carry pipe weight, product weight, insulation, valve operating force and maintenance load. Load tables give uniform, concentrated and line loads separately, and selection uses the worst combination, not uniform load alone.

Concentrated loads gather around valves and flanges. Turning a large valve puts foot load on a small area, so concentrated capacity and support spacing are checked there, with a secondary beam where needed.

Deflection limits matter as much. Pipe rack walkways commonly use span divided by 160, or one quarter of an inch, whichever is smaller; too much deflection lets water stand and makes the walkway feel springy.

Connections, fixings and thermal movement

Grating is usually fixed to steel beams with stainless clips, hold-down plates and bolts. Terminal steelwork carries fireproofing, so a hold-down plate must not damage the coating; fixings avoid the thick edge, with a pad to spread pressure where needed.

FRP expands more than steel across the bars, so long walkways change length with day and night temperature. An expansion gap is needed, fixed at one end and sliding at the other, not locked at both; crossings over fire walls and settlement joints need a transition support.

Platform edges, openings and equipment bases need banding and kick plates. Banding protects the cut edge as well as the panel, and it stops tools and small parts falling through; kick plate height follows the project requirement, and the grating itself is not a substitute for a toe board.

Slip resistance in cold and wet conditions

After an LNG spill, water vapour condenses and the grating can frost or ice over; wash water and rain also freeze at low temperature. Choose the surface for the ice-water mix, and grit is usually more reliable than concave.

Grit still gives some mechanical key through a thin ice layer, but any surface fails under thick ice. The platform needs a de-icing and sanding procedure, drains must not be blocked by ice, and treads and ramps deserve priority inspection.

Low temperature also makes some anti-slip overlays brittle and lets adhesive release. Plate-type surfaces need confirmed low-temperature performance and a sample test before installation, and mechanical fixing is more dependable than adhesive alone.

Specification and acceptance checklist

The specification should state the cold scenario, fire class, anti-static requirement, corrosive environment and load conditions. Miss one and the supplier can only quote a standard product, and adding it later moves both price and delivery.

At acceptance, check the resin system, fire report, anti-static record, fastener material and edge sealing. Grating is a batch product, so site samples must match the approved sample in colour, grit and thickness.

After installation, check earth continuity, fixing torque, sealed cuts and drainage fall. Earthing and fire protection are concealed items that are hard to recheck once covered, so the acceptance record must be kept.

• Describe the cold scenario as splash, pooling or vapour.
• State the fire standard and the limit values.
• List the anti-static target and the earthing method separately.
• Write the fastener material and isolation detail into the specification.