In a power plant, lines differ by service. Superheated steam and cooling water may sit in the same plant, yet material grade, wall thickness and gasket choice are entirely different. We supply pipes, flanges, fittings, gaskets, studs and valves for main steam, feedwater, reheat, cooling water and auxiliary lines in combined cycle, coal and biomass plants.
As temperature rises, the allowable stress of carbon steel falls. Above 400 °C chromium molybdenum alloys take over, and above 550 °C stainless grades. The table lists the matches we meet most often.
| Line | Typical service | Pipe | Flange / fitting | Gasket |
|---|---|---|---|---|
| Main steam | Up to 540 °C | A335 P11 / P22 / P91 | A182 F11 / F22 / F91 | Spiral wound, 316L/graphite |
| Feedwater | 250 °C, high pressure | A106 Gr.B | A105 | Spiral wound with inner and outer ring |
| Reheat | High temperature, low pressure | A335 P22 | A182 F22 | Spiral wound |
| Cooling water | Ambient | A53 / A106 Gr.B | A105, galvanised option | Reinforced rubber or CNAF |
| Instrument lines | Variable | A312 TP316L | A182 F316L forged fittings | Metal to metal |
The table is indicative; the final choice follows the project specification and piping class list.
In a plant outage the critical factor is not price but date. A missing flange or a gasket with the wrong ring material pushes start up back by days. For outage material lists we recommend:
Which pipe material is used for plant steam lines?
It depends on temperature. A106 Gr.B is sufficient below 400 °C, while chromium molybdenum grades such as A335 P11, P22 and P91 are used between 450 and 540 °C. The choice follows the design temperature and pressure in the piping class list.
How should an outage material list be prepared?
Each item needs size, schedule or pressure class, material grade, standard, quantity and certificate level. Gasket and stud sets for joints to be opened should be planned with spares.
Do you provide PMI reports on alloy items?
Yes. On request, positive material identification reports are issued before shipment for P11, P22, P91 and stainless items.
Share your item list, isometrics or MTO file for your power requirement; we reply with price and lead time the same day.