Power plants and high-temperature systems – pipes, fittings and bolting
In short: power-plant steam and feedwater lines need alloyed elevated-temperature steel to EN 10216-2:
- 13CrMo4-5 and 10CrMo9-10;
- for the highest temperatures, X10CrMoVNb9-1 (P91) and X10CrWMoVNb9-2 (P92);
- or their ASTM A335 counterparts.
Every component of the system should be in the same or an equivalent material group:
- fittings;
- flanges;
- elevated-temperature bolting.
Documentation is at least EN 10204 3.1, often 3.2.
This guide is for buyers at power plants, thermal-plant maintenance teams and energy contractors.
What makes power-plant piping special?
- Very high temperature and pressure over long service lives.
- Creep. At high temperature, material slowly deforms under sustained load. Alloyed elevated-temperature steels are designed for this.
- Welding and heat treatment. Alloyed steels need preheating and post-weld heat treatment. Purchased parts must arrive in matching condition and with matching documentation.
- Strict acceptance. Independent inspection (3.2) and extensive NDT are common.
Material overview
| System | Typical material (EN) | ASTM counterpart |
|---|---|---|
| General steam, feedwater | P235GH, P265GH, 16Mo3 | A106 Gr. B / C |
| Higher-temperature steam | 13CrMo4-5, 10CrMo9-10 | A335 P11, P22 (related grades) |
| Main and reheat steam lines | X10CrMoVNb9-1, X10CrWMoVNb9-2 | A335 P91, P92 |
| High-pressure feedwater | 15NiCuMoNb5-6-4 | – |
Equivalents are for guidance. The designer and the applicable standard set the exact material and temperature limits.
The complete package
- Pipes: EN 10216-2 / ASTM A335, seamless, TC2 tested.
- Fittings: EN 10253-2 or ASME B16.9 (WP11, WP22, WP91, WP92), including heavy wall.
- Flanges: 16Mo3, 13CrMo4-5, A182 F11 / F22 / F91.
- Bolting: elevated-temperature studs and nuts (e.g. 21CrMoV5-7, X22CrMoV12-1).
- Gaskets: graphite or metallic, depending on temperature.
- Valves: high-pressure gate and check valves, including pressure-seal designs.
- Heat-exchanger tubes: U-bent for tube bundles.
For nuclear facilities, pipes, fittings and flanges to special codes (e.g. RCC-M) can also be sourced.
Buyer checklist
- Grade and standard for every component.
- Size: OD × wall; for fittings, the wall at the weld bevel.
- Test category: TC2, NDT requirements.
- Heat-treatment condition, if specified.
- Certificate: 3.1 or 3.2, naming the inspection body.
- Ends: bevels to the welding procedure.
- Delivery: scheduled to the outage.
Common mistakes
- Fittings or flanges from a different material group in a P91 line.
- Non-elevated-temperature bolting in a high-temperature flanged joint.
- Lead time for 3.2 inspection not included in the schedule.
- Incomplete end preparation, which causes site rework.
Frequently asked questions
What is P91?
P91 is the ASTM designation of X10CrMoVNb9-1 (1.4903), an alloyed elevated-temperature steel used for very-high-temperature power-plant steam lines.
Do you supply the bolting too?
Yes, elevated-temperature studs and nuts, including custom sizes.
Can you schedule to an outage?
Yes, with time-slot delivery to the outage schedule.
Request a quote
Send your material list and acceptance requirements. We quote pipes, fittings, flanges, bolting and valves in one offer.
Related: Boiler & high-temperature pipes · Flange bolting · P91 · 13CrMo4-5 · Steam guide
Send us your material list – one quote for the complete package (pipe, fittings, flanges, gaskets, bolting), sourced direct from manufacturers, no minimum order.
Request a quote