Buyer guide · approx. 8 min read

Pipes and fittings for steam lines – material selection and sourcing

In short: steam and hot-water lines need pressure-rated, elevated-temperature steel pipe.

• Typical grades: P235GH or P265GH to EN 10216-2 (seamless) or EN 10217-2 (welded).
• Higher service temperatures: 16Mo3.
• Power-plant steam: 13CrMo4-5 or 10CrMo9-10.

Fittings, flanges, gaskets and bolting must be rated for the same temperature and pressure as the pipe. Every pressure part should come with an EN 10204 3.1 inspection certificate.

This guide is for buyers, maintenance managers and mechanical designers. It helps you specify a complete steam line clearly in one request for quotation – from pipe to bolts – and avoid the gaps that later cause delays or rejected deliveries.

What makes steam piping different?

Several loads act on a steam or hot-water line at the same time:

• Sustained high temperature. Ordinary structural or line-pipe steels lose strength as temperature rises. Elevated-temperature steels have strength values that the standard guarantees at higher temperatures.
• Internal pressure. A steam line is pressure equipment. Material, manufacture and testing are therefore governed by pressure-equipment standards.
• Thermal expansion and cycling. At every start-up and shutdown the line expands and contracts. This loads welds, flanged joints and supports.
• Condensate and corrosion. Condensing water can cause internal corrosion and erosion, especially in condensate branches.

That is why "a steel pipe" is not enough. You need a grade whose standard was written for pressurised service at elevated temperature, and certificates that prove it.

Which grade should I choose?

The designer always sets the grade, based on service temperature, pressure and the applicable codes. The table shows typical choices. Its purpose is to help buyers understand the designations on a drawing and know what to request.

Exact temperature limits come from the applicable standard and your designer. Always check them against the design documents.

Seamless or welded?

Both can be used for steam if the standard and the test category match the design.

• Seamless (EN 10216-2): typical for small and medium diameters and heavier walls. There is no longitudinal weld, so many designers specify seamless for the more critical branches.
• Welded (EN 10217-2; EN 10217-5 for large submerged-arc welded sizes): more economical at larger diameters. The weld seam is non-destructively tested as the standard requires.

If a drawing just says "P235GH pipe", ask whether seamless is explicitly required. It affects both price and lead time.

TC1 or TC2? The test category

EN 10216-2 and EN 10217-2 define two test categories: TC1 and TC2. TC2 involves more extensive testing, including non-destructive testing. Which one applies depends on the pressure-equipment classification and the designer.

For purchasing, the key point is this: always state the test category in your RFQ. Without it, quotes are not comparable, and a mismatch may only surface at goods receipt.

The complete steam line in one quote

A steam line is only as reliable as its weakest component. Besides the pipe, you need:

• Pipe: P235GH / P265GH or 16Mo3 to EN 10216-2 / EN 10217-2, in the specified OD × wall.
• Butt-weld fittings: 90° and 45° elbows (typically 3D or 1.5D radius), equal and reducing tees, concentric and eccentric reducers, caps – to EN 10253-2, Type A or Type B, from the same material group as the pipe.
• Flanges: weld-neck (EN 1092-1 Type 11) and blind (Type 05) in the right PN, in elevated-temperature flange steel (e.g. P245GH, P250GH, 16Mo3).
• Gaskets: for steam typically expanded graphite with a metal insert, to EN 1514-1, matched to flange DN/PN.
• Flange bolting: elevated-temperature studs (e.g. 25CrMo4) and nuts (e.g. C35E) to EN 10269 and EN 1515-1.
• Valves: flanged gate valves, globe valves and strainers in the line's PN, with cast steel bodies (e.g. GP240GH).
• Forged fittings and branches: socket-weld couplings and Weldolets for instrument and drain connections.

Why source it from one place? When the whole package comes in one quote, grades, pressure ratings and certificates are matched to each other. You avoid the situation where the pipe complies but the flange or the bolts do not. WoodFlow quotes the complete package direct from manufacturers, with no minimum order.

Buyer checklist – what to put in your RFQ

1. Grade and standard – e.g. "P235GH, EN 10216-2". A grade without its standard is not enough.
2. Size – OD × wall in mm (e.g. 168.3 × 4.5), or DN and schedule / wall.
3. Manufacturing route – seamless or welded, if specified.
4. Test category – TC1 or TC2.
5. Certificate – EN 10204 3.1, or 3.2 if required.
6. Pipe ends – plain or bevelled for welding.
7. Lengths and quantity – fixed or random lengths; metres or pieces.
8. Fittings – radius (e.g. 3D), Type A/B, wall matched to the pipe.
9. Flanges – type (11, 05), PN, facing (e.g. B1), grade.
10. Delivery – single, partial, or time-slot delivery (e.g. for a shutdown).

If you already have a quote or a material list, send it. We compare it line by line and price the complete package.

Common mistakes when sourcing steam piping

• Only the pipe is elevated-temperature grade. The flange, bolts or valve are general structural material, which is not suitable at high temperature.
• PN mismatch between flange and valve.
• Missing certificate for a pressure part. This can stop installation at goods receipt.
• Mixing EN and ASME flanges on one line. Bolt patterns and facings differ.
• Wrong gasket material. Not every flat gasket suits steam, so always choose the gasket for the medium and temperature.
• Test category left out, which makes quotes incomparable.

Frequently asked questions

Request a quote for the complete package

Send us your material list or an existing quote. We reply with one quote based on manufacturer-level pricing for the whole steam line, from pipe to bolts.

Related: Boiler & high-temperature pipes · Butt-weld fittings · Flanges · Flange gaskets · Flange bolting · P235GH · 16Mo3 · EN 10216-2