Aluminium grating

What it is

Aluminium grating is bar grating made from extruded aluminium bearing bars and cross bars. Its main advantages are low weight – roughly one third of a steel panel of similar size – and natural corrosion resistance from the oxide film that forms on the surface. Panels can be lifted by hand, removed for maintenance access without cranes and installed on light structures where every kilogram counts.

Typical uses include marine and offshore walkways, wastewater and water treatment channels, food and beverage plants, chemical areas where zinc would be attacked, cooling tower decks, roof access walkways, and floating or removable covers. World Steel supplies aluminium grating as part of a project package together with the platforms and walkways, support frames, handrails and fixings that it fabricates. Panels are produced on specialist aluminium grating lines; World Steel details the layout, coordinates the panel schedule with the steelwork, inspects, marks and packs everything for one delivery.

Types and options

Bearing bars are usually extruded in 6063-T5 / T6 or 6061-T6 alloy, with I-bar profiles that save weight while keeping the depth needed for stiffness. Bar depth and pitch are selected from the design load, span and deflection limit in the same way as for steel bar grating.

Design and compliance

Aluminium has about one third of the elastic modulus of steel, so deflection rather than strength usually governs the span. Panels are designed to AS/NZS 1664.1 in Australia and New Zealand, the Aluminum Design Manual (ADM) of the Aluminum Association in the US, and EN 1999-1-1 in Europe, using imposed loads from AS/NZS 1170.1, ASCE 7 or EN 1991-1-1. Access platforms must meet AS 1657, OSHA 29 CFR 1910 Subpart D or EN ISO 14122-2 for clear width, edge protection and toeboards, and the NAAMM grating manuals give guidance on aluminium types for US projects.

Galvanic isolation is essential: where aluminium panels sit on carbon steel or galvanised supports, use isolation pads, sleeves and washers (for example neoprene or nylon) and stainless or suitably coated fasteners, especially in wet or marine environments. Aluminium should not be in direct contact with wet concrete or mortar. Fire behaviour should also be considered – aluminium loses strength at much lower temperatures than steel, so check the fire strategy for escape routes. See design loads and bolts and fasteners.

Fabrication, finishing and supply

The grating panels themselves are manufactured by specialist aluminium grating producers and supplied by World Steel with the project package. World Steel produces the layout and panel schedule from the Tekla model, cuts and bands panels where required, inspects dimensions and marks each panel with its layout reference and span direction. Any welding of aluminium is carried out only by qualified welders to the applicable aluminium welding standard and is kept to a minimum; bolted banding and clips are often preferred.

The steel supports, frames, clips and fasteners and handrails are fabricated in the World Steel plant under its AS/NZS 5131 and EN 1090-2 systems, then hot-dip galvanised or painted. Everything is packed by area for export shipping so the site receives matching frames, panels and isolation kits together.

Installation and selecting

• Choose aluminium where weight, corrosion resistance, removability or the absence of zinc matter; choose steel where loads are high, spans are long or cost is the driver.
• Fix panels with stainless clips or saddle clamps over isolation pads; avoid drilling or cutting panels on site without re-banding.
• Keep a small expansion gap between panels – aluminium expands about twice as much as steel with temperature.
• Check with the client whether caustic cleaning chemicals are used, as strong alkalis attack aluminium.