Actual suitability comes from code allowable stresses, design temperature, pressure, wall thickness and creep requirements.
Matching fittings and flanges generally use WP11/F11 or WP22/F22 families as specified.
Key points
- P11: lower chromium-molybdenum level
- P22: higher Cr-Mo content
- Both require controlled welding and heat treatment
- PMI and hardness checks are common