What mining demands

Grating in a mine faces ore, water, dust and heavy machinery. Crusher stations, screening plants, conveyor galleries and thickener platforms all use grating, and falling ore, washdown and equipment vibration act together, so damage usually starts locally.

Ore impact and abrasion are more severe than on an ordinary industrial floor. Sharp ore falls from a belt or chute and creates point loads on the grating; loaders and service vehicles add concentrated load and horizontal thrust. Capacity cannot be estimated from an allowance per person.

Mining also brings corrosion. Acid mine water, process reagents and damp dust accelerate metal corrosion, and steel grating needs frequent coating or replacement. The corrosion resistance of FRP grating cuts that maintenance, but its strength and stiffness differ from steel, so selection must use FRP data.

Abrasion and impact

The wear resistance of FRP grating comes from the resin and the surface layer. Resin binds the glass fibre, and the surface layer takes the cutting action of abrasive particles. A high wear class usually means a thicker resin-rich layer or wear filler, but the smoother the surface, the lower the slip resistance.

Impact is a separate problem. FRP is brittle, and a local impact can crack resin and break fibre; the damage may look like a small pit while delamination has already started inside. Fit a buffer plate or wear liner under drop points rather than letting ore strike the grating directly.

Point load is more dangerous than uniform load. An ore lump or a tool acting on a single bearing bar produces local stress far above the design value. Ask for the maximum lump weight and drop height, not just a uniform load figure.

Wear and impact usually arrive together. Falling ore both strikes and slides, so the surface first shows scuffing and then develops pits. Inspecting grating at drop zones and transfer points regularly is cheaper than replacing whole runs.

Load capacity and span

The capacity of FRP grating depends on bearing bar depth, wall thickness, fibre content and span. At the same nominal depth, makers may use different bar sections, so load tables are not interchangeable. Select from the maker's span and load table and keep a safety factor.

Deflection often governs before strength. If a mine walkway deflects too much, people feel it sink, and repeated movement loosens the fixings. Deflection is usually limited to a proportion of the span, with the exact limit set by the project specification.

Dynamic load needs separate treatment. Equipment vibration, vehicle traffic and ore impact all amplify load, and a static table cannot simply be applied. Reduce the allowable span or add supports for dynamic duty. To read span and load tables, see FRP grating load capacity

Fire performance and static

Mines have fire requirements, and the fire rating of the grating must be confirmed. FRP grating can be made fire retardant, but the rating and test standard should be stated, for example flame spread index and smoke density. Ratings under different standards are not interchangeable.

Fire retardant does not mean non-combustible. A retardant resin may self-extinguish once the flame source is removed, but it still decomposes and produces smoke at sustained high temperature. Treat the grating rating as part of the area's fire design, not as a fire barrier on its own.

Static is a risk in mines, especially underground and in dusty areas. Ordinary FRP grating does not conduct, and friction and moving dust can build a charge. Where static control is required, specify an antistatic grade and confirm the surface resistance range and the earthing method.

Antistatic performance falls with surface wear and contamination. Even with antistatic grating, clean and test periodically; one selection does not last forever. Earth connections should use stainless parts and avoid paint and coatings.

Dust and cleaning

Mine dust is heavy, and fine or damp material blinds the openings. Once blocked, drainage and slip resistance fall and weight rises. Design around the dust: where necessary, use a more open pattern.

The cleaning method affects panel life. A pressure washer suits dust but damages the resin surface at too high a pressure; scraping clears build-up but scratches the panel. Remove large lumps first so hard material is not dragged across the grating.

Dust also hides damage. Cracks, whitening and delamination are hard to see under a layer of dirt, so regular cleaning is part of inspection. Focus on drop points, transfer stations and vehicle routes.

Supports and fixing

Mine supports vary: steel structures, concrete beams and rock. Grating should bear continuously on its supports, with spacing taken from the load table. Uneven support loads the panel locally and can lead to cracking.

Fixings must take vibration. Mine equipment vibrates strongly, ordinary bolts work loose, and locking nuts or clips plus periodic re-tightening are needed. Not every fixing should be locked; leave allowance for thermal movement.

Where grating sits on steel beams, the contact face collects water and dust and corrosion starts there. Coat or FRP-encapsulate the beam, and fit an isolating pad between grating and beam to reduce crevice corrosion.

Compared with steel grating

FRP grating weighs roughly a quarter of steel grating, so installation needs no heavy lifting and transport underground is easier. Lower weight also means less load on supports and structure, which suits replacement in existing plants.

The corrosion difference is larger. Steel grating in acid mine water needs hot-dip galvanizing or coating, and corrosion runs fast once the coating is broken; FRP grating needs no coating, and maintenance is mainly cleaning and inspection.

The weaknesses of FRP are stiffness and impact resistance. Where spans are long and impact is severe, steel still suits better, or the FRP panel must be deeper with closer supports. Choose material by location rather than applying one answer across the mine. For the overall case, see the benefits of FRP grating

Selection and purchasing

The purchase document should state resin type, fire rating, antistatic requirement, panel depth, bearing bar section, open area, anti-slip surface, colour and edge sealing. Mining projects often also ask for load tables and material certificates.

• State resin, fire rating and antistatic separately.
• Check load tables against real span and dynamic load.
• Fabricate special shapes in the factory.
• Verify dimensions and batch on first delivery.

Confirm batch and dimensions before delivery. Site modification is difficult in a mine, and a wrong size can reject a whole batch. Fabricate special shapes in the factory and keep site adjustment to a minimum.

After installation, carry out a full check of support contact, fixing torque and surface damage. Inspect again after the first month in service, then follow the maintenance plan. To match grating type to the duty, see mining and heavy-industry applications