Mitered Pipe in S8D1?

[solinar]

Pretty simple question, are mitered pipe bends allowed in ASME Section VIII Div. 1?

I have a 30" nozzle which the buyer would like to have a mitered 45° joint in. After scouring code and the internet, I'm not seeing anything either allowing or prohibiting their use in Section VIII Div 1. Can I just use the provisions from B31.3 for this joint as an alternative?

Thanks

 

[trottiey]

Section VIII doesn't cover piping, just pressure vessels; that's why you won't find mitered joints there. I you're designing piping, you should use a piping code such as B31.3.

 

[solinar]

I'm designing a nozzle which requires a 45° mitered bend between the nozzle neck and the flange of the nozzle, so within the scope of Div 1 per U-1(e)(1)(c).

 

[Duwe6]

*If* you can show valid strength calculations, you can use miters. Problem is, you will probably go to VIII Div-2 to 'legally' calc it -- skew-angle corner welds as a pressure boundary.

Probably be cheaper to order a custom bent section of pipe and stay in VIII Div-1.

 

[trottiey]

Piping codes basically assume that thermal expansion and other displacements will be taken up by bending of straight sections, so the elbows see minimal stress. This is not such a good assumption for an elbow welded right onto a pressure vessel, and that's the engineering reason why you might not want to put a miter joint there. But as long as you can cram your reasoning within U-2(g) to the satisfaction of your inspector, then you can do anything you want.