BS EN 10255 Steel Pipe: What the Standard Covers and How to Specify It

Standard: BS EN 10255:2004 · GI & black welded steel pipe (MIG-MELEWAR)

What BS EN 10255 covers

BS EN 10255 specifies non-alloy steel tube suitable for welding and threading, in nominal bores from 6 mm to 150 mm. Threads are cut to BS EN 10226-1 (the successor to BS 21). The tube is supplied in black (self-colour) or hot-dip galvanised finish, in standard 6 m or 6.4 m lengths, with plain-end (PE) or threaded-and-socketed (T/C) ends — T/C comes with one parallel-threaded malleable iron socket.

It is the default steel-pipe standard across Malaysian trades: GI conduit and water lines, chilled-water and condenser pipe in cooling plant, fire sprinkler and hydrant lines, and general compressed-air and process pipework.

The wall series — L1, L2, Medium, Heavy

The standard grades tube by wall thickness series, each identified by a colour band (~50 mm wide, ~300 mm from each end):

Series	Colour band	Typical use
Type L1	White	Light-duty
Type L2 (Light)	Brown	Light mechanical / conduit
Medium	Blue	General service
Heavy	Red	Higher-pressure / structural service

Two pipes of the same nominal bore but different series carry different wall thickness — and therefore different weight, pressure capability, and price. Ordering “50 mm GI pipe” without the series is how the wrong wall arrives on site.

Material and testing requirements

Per the manufacturer’s published data for MIG-MELEWAR pipe to BS EN 10255, the tube meets defined chemical and mechanical limits (cast analysis: carbon, manganese, phosphorus, sulphur capped; yield 195 MPa minimum, tensile 320–520 MPa). Every length is leak-tested — a hydrostatic test at minimum 50 bar for at least 5 seconds, or equivalent automatic electromagnetic testing. Bend and flattening tests apply by diameter (EN 10232 / EN 10233).

BS EN 10255 vs BS 1387

BS 1387 was the earlier British Standard for screwed and socketed steel tube; BS EN 10255 superseded it. Malaysian specifications and drawings still cite “BS 1387 Class B / Class C” out of habit — Class B maps broadly to Medium and Class C to Heavy. When a drawing says BS 1387, confirm with the consultant that BS EN 10255 of the equivalent series is accepted before substituting.

What to confirm before you order

For the published dimensions and mechanical data, see the GI pipe spec table, then send your schedule for a quotation across the series you need.