Welded A/SA 691 P91 pipe VS Smls A335 P91 2

[ravera]

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.

 

[metengr]

Section I does not permit the use of A 691 material (see ASME B&PV code, Section I, PG-9). At the last code meeting I attended, there was some talk about re-opening this item. Basically, for Power Boiler application, Section I has administrative authority (see Section I for boundaries of boiler components). Beyond the first isolation valve for main steam piping in single boiler design, B31.1 has administrative authority and A 691 piping can be used.

ASME B31.1 does permit use of A 691 pipe material (see Mandatory Appendix A, Table A-2.

 

[ravera]

Does a Section I boiler require a code stamp and what is the stamp?

 

[metengr]

From your original post I am assuming that your question pertains to supplying boiler components or pressure parts. If so, ASME B&PV Code, Section I requires a fabricator of boiler components to have a valid Certificate and "S" stamp.

 

[davefitz]

Meteng is right, although I was surprised to see that a longitudinally welded P91 pipe is permitted, considering the past problems with type IV creep damage along a weld line.

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)

 

[ravera]

Further to my previous post and recognizing that A691 is not an acceptable material under Section I, does the same hold true for welded pipe produced under ASME SA671 and ASME SA 672?

 

[metengr]

Yes. Please see ASME Section I, PG-9

 

[ravera]

Thanks metengr for your post. Unfortunately I do not have a copy of Section I. I work for a large seamless pipe producer and am trying to get a copy from our office in Italy however, to date no luck. Can you elaborate further on the information on Pg-9. Specifically I'm trying to verify the codes in the power and process industries that today accept pipe of welded construction (A671,672,691). In my prior life I worked with customers to get welded products accepted in the various industries. That was several years back and during the interim, I've had little exposure to the changes that have been recognized by the varous codes (Sect I, Sect III, B31.1, B31.3 etc. etc.). Now that I work for a Seamless producer, I'm trying to understand the changes in acceptability and where my efforts may have affected our large diameter (Through 28")seamless production in (A333 Gr 6, A106 B/C, A335 P11 thru P91). Any insight is appreciated.

 

[ravera]

Sorry, One more spec that should be included in the list identified above is Section VIII Div1.

Tks

 

[metengr]

ravera;
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.