Superheater coils and tube sheets: special parts for boiler & power plant
In boiler and power plant construction, standard parts are not enough. Superheater coils, membrane walls and tube sheets are manufactured to drawing – from creep-resistant materials, to recognised codes and with complete documentation.
Superheater coils
Superheater coils are bent tube runs in which steam is heated beyond saturation temperature. They sit in the hottest part of the boiler and carry full internal pressure at the same time – the toughest combination any pipe material has to withstand.
They are manufactured to drawing, with defined bend radii, run spacings and weld positions. Decisive is the remaining wall thickness in the bend: bending thins the outside, and that is exactly where stress is highest.
Materials by temperature
| Material | Material no. | Continuous service up to approx. |
|---|---|---|
| P235GH / P265GH | 1.0345 / 1.0425 | 400 °C |
| 16Mo3 | 1.5415 | 530 °C |
| 13CrMo4-5 | 1.7335 | 570 °C |
| 14MoV6-3 | 1.7715 | 565 °C |
| 10CrMo9-10 | 1.7380 | 600 °C |
| X20CrMoV11-1 | 1.4922 | 580 °C |
| P91 / X10CrMoVNb9-1 | 1.4903 | 620 °C |
Guide values for continuous service. The governing figures are the creep rupture values of the relevant standard and the design to code.
Tube sheets and drilled plates
The tube sheet is the plate in which the boiler tubes terminate. In a three-pass boiler the flue gas passes through three passes; the tubes are expanded or welded into the drilled tube sheet. The hole pattern – number, diameter and pitch – is manufactured exactly to specification, as are manholes, headers and distributors.
Expanding or welding
| Criterion | Expanding | Welding |
|---|---|---|
| Joint | friction grip by expansion | metallurgical bond |
| Pressure and temperature | limited | higher capability |
| Replacement in service | easier | more involved |
| Testing effort | low | weld testing required |
Which option suits depends on pressure, temperature and maintenance concept – frequently both are combined: welded and additionally expanded.
Codes and standards
| Code | Applies to |
|---|---|
| EN 12952 | Water-tube boilers |
| EN 12953 | Shell boilers |
| AD 2000 | Pressure vessels; W 4 applies to pipes, W 2 to austenitic parts |
| Pressure Equipment Directive 2014/68/EU | Placing pressure equipment on the EU market |
| EN ISO 3834 | Quality requirements for welding |
Documentation and traceability
Creep-resistant grades are supplied with inspection certificate 3.1 to EN 10204, where required 3.2 with survey by a notified body. Every item remains traceable through batch and mill, welding procedures are qualified to EN ISO 3834, pressure test reports are included on request.
This is not a formality: it is exactly this chain that is examined at inspection. If a certificate is missing, the component cannot be installed – regardless of how well it was made. More in inspection certificate 3.1 or 2.2.
The full range for boilers and power plants is under power plant, boilers and machining, manufacture to drawing under special parts and custom manufacture.
Frequently Asked Questions
What material are superheater coils made from?
Creep-resistant boiler tube, depending on temperature 16Mo3 to about 530 °C, 13CrMo4-5 to 570 °C, 10CrMo9-10 to 600 °C, X20CrMoV11-1 to 580 °C, and P91 to about 620 °C.
What matters when bending?
The remaining wall thickness in the bend. Bending thins the outside, and that is exactly where stress is highest. The remaining wall must still satisfy the design.
Expanding or welding tubes into the tube sheet?
Expanding is a friction grip, simpler in service and requires less testing. Welding is a metallurgical bond with higher capability but requires weld testing. The two are frequently combined.
Which codes apply?
EN 12952 for water-tube boilers, EN 12953 for shell boilers, the AD 2000 code, Pressure Equipment Directive 2014/68/EU and EN ISO 3834 for welding.
What documentation is supplied?
Inspection certificate 3.1 to EN 10204, where required 3.2 with survey by a notified body, plus welding procedures qualified to EN ISO 3834 and pressure test reports on request.
Do you need exactly these parts?
Grade, size, pressure rating and quantity are enough – you usually receive your quote the same day, with an inspection certificate 3.1 on request.
Request a quote