Welded A/SA 691 P91 pipe VS Smls A335 P91
Welded A/SA 691 P91 pipe VS Smls A335 P91
(OP)
A number of years back I worked with a domestic E&C getting A/SA 691 P91 pipe approved for use in Power Plant construction. After months of testing and qualification in Europe, the welded pipe was finally approved. I am trying to understand the current B31.1 and Section 1 requirements related to the use of welded construction in power (boiler) applications. Specifically, where can welded be utilized AND where does the code still mandate a seamless product.
thanks for the input on this topic.
thanks for the input on this topic.





RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
ASME B31.1 does permit use of A 691 pipe material (see Mandatory Appendix A, Table A-2.
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
The reason it can be done is that A 691 spec requires class 40+ pipes to be normalized and tempered, and class 50+ to be quenched and tempered. This normalizing to 1900 F + will restore the metalurgical properties of the HAZ .
There is also a note in B31.1 that states A 691 may NOT be used as boiler external piping ( ie section I)
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
Tks
RE: Welded A/SA 691 P91 pipe VS Smls A335 P91
Your best is to locate asme.org web site or a codes and standards web site and inquire about purchasing Section I, VIII and Section II. These three Code book sections are probably your best bet at having the necessary information as a piping producer.
As far as welded pipe, Section I only permits SA-660 which is Centrifugally Cast Carbon Steel Pipe for High Temperature Service.
For Section VIII Div 1, SA 671 and SA 672 welded pipe specifications are permitted.