Welding P-1 to P-4 material?

[ngiguy]

I have existing piping (SA-335, P11 material) requiring relocation to avoid new construction. Can I use P-1 material (SA106, Gr. C) for the relocated piping instead of the original SA335 material?

line size 1/2" (instrument tap)
700 deg. F, 4700 psi design conditions

It's a simple matter of using existing plant specifications, or writing a new one from scratch.
It's just easier on the troops if we can safely weld these two materials than it will be to write a complete new specification and then waste a month getting it through approvals just for a 40' length of relocated piping.

Thx.

 

[metengr]

ngiguy;
Given your stated operating conditions, the ASME SA 106 Grade C material would work. The allowable stress values for SA 106 Grade C at 700 deg F is 16.6 Ksi. For the original SA 335 Grade P11, at 700 deg F , the allowable stress values is 15 Ksi, so yes, the SA 106 Grade C would be feasible to use. Just remember, if your connection welds will be joining SA 106 Grade C (P-No 1) material to SA 335 Grade P11 (P-No 4) material you need to follow preheat requirements for the P-No 4 base material. Also, note the material change on your piping diagrams for reference purposes.

 

[stanweld]

While from a strength standpoint the A-106 C is quite attractive, corrosion resistance may be impaired depending on the process fluid composition.