Steel gratings are open panels of flat load bars held apart by cross bars, used as floors, platforms, walkways, stair treads and trench covers. They carry people and vehicles while letting light, air, water and dirt pass through, and they are the standard flooring of industrial plants, refineries and offshore structures.
A grating is a grid of parallel load bearing bars — flat bars set on edge, which carry the load — and cross bars at right angles that keep them upright and spread a point load. In welded (electro-forged) gratings the cross bars, usually twisted square bar, are pressed into the top of the load bars and resistance-welded at every crossing in one stroke. In press-locked gratings slotted bars are pushed into each other under high pressure, which gives a neater, more even mesh for architectural use. The panel is then cut to size, banded round its edges and hot-dip galvanized.
A grating's capacity is set by the depth and thickness of the load bars and their spacing, and by the span between supports, which must always run along the load bars. Makers publish load tables of uniform load and concentrated load against span and deflection, and designers pick the lightest grating that meets them. Serrated (notched) load bars give a better grip where floors are wet or oily.
In American practice a grating is named by its load bar spacing and cross bar spacing, for example 19-W-4: load bars at 19/16 in (30 mm) centres, welded, cross bars at 4 in (100 mm). European makers give the pitch in millimetres, for example 30 × 100 (load bar pitch × cross bar pitch).
Gratings are used throughout the GCC's refineries, gas plants, power and desalination plants, port and offshore facilities, and in building services and car parks. They are fabricated and galvanized in the region from flat bars and twisted bars, and imported as panels from China, India and Europe. Hot-dip galvanizing is standard because of the region's coastal and industrial atmospheres.
Gratings are ordered as panels to a layout drawing: each panel's size, the load bar size and pitch, the cross bar pitch, the span direction, cut-outs and their banding, the surface (plain or serrated) and the finish.
| Region | Standard | What it covers |
|---|---|---|
| USA | ANSI/NAAMM MBG 531 | Metal Bar Grating Manual — designations, load tables and fabrication of steel, aluminium and stainless bar gratings |
| USA | ANSI/NAAMM MBG 532 | Heavy-duty metal bar grating manual, for vehicle and truck loads |
| UK | BS 4592-1 BSI |
Industrial type flooring and stair treads — metal open bar gratings; specification |
| Germany | DIN 24537-1 DIN |
Gratings used as flooring — gratings made of metallic materials |
| International | ISO 1461 ISO |
Hot dip galvanized coatings on fabricated iron and steel articles |
| USA | ASTM A123/A123M ASTM |
Zinc (hot-dip galvanized) coatings on iron and steel products |
| International | ISO 14122-2 ISO |
Safety of machinery — permanent means of access; working platforms and walkways |
Grade equivalents and the standards bodies: Steel grades & standards
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