EN 10255 — Non-alloy steel tubes suitable for welding and threading. Technical delivery conditions
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Scope
Welded and seamless non-alloy steel tubes in grade S195T (1.0026), sizes DN 6 to DN 150 (½" to 6"), suitable for screwing (EN 10226-1 threads) and welding: light series L/L1/L2, medium series M and heavy series H, plus the derived series L1/L2. Used for water, gas, compressed air, sprinkler and structural applications; galvanizing per EN 10240. The successor of BS 1387 (Class A/B/C) and DIN 2440/2441/2442.
Grades covered by EN 10255
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| S195T | 1.0026 | Non-alloy steel for welded and threaded tubes (water, gas, sprinkler, GI pipe) | ≤ 0.2 | 195 | 320–520 | A53 Grade A (Type E/F), Ст2сп / Ст3сп (GOST 3262), SGP (JIS G3452) |
Revision history and superseded standards
| Year | Change |
|---|---|
| 1985 | BS 1387 light/medium/heavy classes — the reference for GI pipe worldwide |
| 2004 | EN 10255:2004 — European harmonisation; L/M/H series |
| 2007 | EN 10255:2004+A1:2007 — current; amendment on marking and test pressures |
Supersedes: BS 1387:1985 (Class A, B, C); DIN 2440 / 2441 / 2442 (mittelschwer, schwer, leicht); NF A 49-145; UNI 8863.
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Related standards
The threadable tube standard
EN 10255 covers non-alloy steel tubes suitable for welding and threading — the water and gas pipe that replaced the old British and German threaded-pipe standards. Its defining feature is that the wall is thick enough to cut a taper thread into without breaching the pressure envelope.
Sizes are given in a nominal designation with its own outside diameters, and thickness comes in series: L (light), M (medium) and H (heavy). Medium is the common water and gas series. These are not schedule numbers and do not convert to them; a tube ordered as SCH 40 is a different product from one ordered as series M.
Galvanizing under EN 10240
Threaded tube for water service is normally hot-dip galvanized, and the coating is governed by a separate standard, EN 10240, with quality classes A1 and A2 covering the inside and outside of the tube.
That matters because pre-galvanized tube — formed from already-coated strip — leaves the weld seam and the bore bare. For potable water and gas the requirement is galvanizing after welding, which coats the bore, the seam and the threads. Substituting pre-galvanized tube against an EN 10255 with EN 10240 coating requirement is a common and consequential error.