High-Temp Pipe Economics

[CW3]

Does anybody have experience in A335 P2 vs. A335 P11 pipe as far as cost and availability? In a low-pressure (<200 psig) high-temp (1000F max) application, we have always used the P11 material (F11 flanges, forgings, etc). Is there any cost savings or availability issues with P2 material???


Tahnks,
\
Curtis

 

[davefitz]

P2 has been used as waterwall tubing in boiler furnace membrane walls,since it does not require the post weld stress relief that is required for a P11 membrane wall.

P11 has 1.25% Chrome,which resists erosion -corrosion damage and is useful in some applications where this is a problem. Also,some codes will not permit you to use a material if it can ever be overheated above the max tempfor which the code provides an allowable stress. For P11thatmay be 1100 F but for P2that may be 1000 F.

 

[metengr]

P2 (nominally 0.5%Cr - 0.5% Mo) has lower chromium in comparison to P11 and is limited by ASME B&PV Code to 1000 deg F. The reason for this limitation is the lower chromium content that results in higher oxidation rates and higher creep deformation rates at or above 1000 deg F.

If you want to use P2, you will need to account for the reduced allowable stresses by increasing the thickness of the component, which adds weight. This could result in availability issues and increased cost in comparison to P11. Personally, I would stick with P11 material because you have increased design margin.