ASTM A335 Chrome-Moly Alloy Pipe (P11, P22, P91)
ASTM A335 covers seamless ferritic alloy steel pipe intended for high-temperature service in power generation steam lines, refinery hydroprocessing units, and chemical synthesis heaters. The chromium and molybdenum alloying additions provide superior creep strength, hydrogen attack resistance, and oxidation resistance at temperatures up to 650°C.
Material Quick Reference
| Material Classification | Seamless Ferritic Alloy Steel Pipe for High-Temperature Service |
|---|---|
| Pitting Resistance (PREN) | N/A |
| Temperature Limits | +400°C to +650°C |
| Governing Specifications | ASTM A335 (P11, P22, P91), ASME SA335, ASME B31.1 (Power Piping), ASME Section I |
Typical Engineering Applications
- Main steam and hot reheat piping in combined cycle power plants (CCGT)
- Refinery hydrocracker and delayed coker high-temperature transfer lines
- Boiler superheater and reheater interconnecting piping
- High-pressure hydrogen process lines
Chemical Environment & Corrosion Resistance
High-temperature, high-pressure steam and hydrogen environments (Nelson curve compliant).
Performance in Qatar's Coastal & Industrial Climate
Essential for Qatar’s major power and desalination complexes (Ras Qartas, Facility D) and refinery furnaces.
Welding & Fabrication Guidelines
Demands strict preheating (150°C to 250°C), hydrogen bake-out, and precision Post-Weld Heat Treatment (PWHT at 700°C–760°C) with computerized chart recorders.
Positive Material Identification (PMI) Requirements
XRF testing confirming Cr and Mo content (P11: 1.25% Cr / 0.5% Mo; P22: 2.25% Cr / 1% Mo; P91: 9% Cr / 1% Mo + V/Nb).
Key Advantages
- Outstanding creep rupture strength above 500°C
- High resistance to high-temperature hydrogen attack (HTHA)
Engineering Limitations
- Strict PWHT compliance required; improper thermal cycles cause severe embrittlement or premature failure
Related Products & Contracting Services
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