Welded vs Seamless ASME B16.9 Fittings

[AgsMyDude]

I have seen 24" listed as the maximum size for A234 WPB (seamless) fittings; beyond that they are welded (WPB-W).

Is there a standard that actually specifies this as as the breakpoint?

Additionally, their pressure ratings should both be equivalent to seamless pipe if built to B16.9 (para 2.1). It seems like it would make more sense to be able to specify an A234 WPB fitting of either construction but A234 does not allow this option as WPB by itself indicates seamless. Maybe there are other requirements triggered by use of welded fittings I'm not considering?

Thanks in advance

 

[1503-44]

Fabrication of seamless pipe and fittings over 24" becomes somewhat impractical and costly. Seamed pipe and fittings are more economical.

Pressure ratings for steel pipe and fittings are determined by the material strength and wall thickness per the design code in use. They do not have to meet any specific pressure rating, only the design pressure. Flanges have pressure ratings. Fittings and pipe no.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

There is no standard in aware of, is just what the manufacturers have determined as the practical cut off.

Pipe is the asme. You can find the odd supplier of 26" seamless, but you have to look hard.

I think it's something to do with the size of the steel billet which limits the mass of the seamless thing.

Some fittings are forged are they not?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r6155]

Flanges have pressure ratings. Fittings and pipe no.

See ASME B16.11
2 PRESSURE RATINGS
2.1 General
Fittings under this Standard shall be designated as Class
2000, 3000, and 6000 for threaded end fittings and Class
3000, 6000, and 9000 for socket-weld end fittings.
2.1.1 Basis of Rating. The sc..........

Regards

 

[1503-44]

Yeah I know. You are right. But he was asking about B16.9 and those are B16.11. We simply don't use any threaded or socket things because of corrosion and none of those, over 2" for strength assurance.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."