Valve Flange Face Parallelism Standard
Valve Flange Face Parallelism Standard
(OP)
Does anyone know of a published standard for straight-pattern valve body flange face parallelism? When flanges are welded to a butt weld glove valve body, there is no assurance of inherent parallelism as there would be if the facings were machined on a cast or forged body.
I've been to the piping forum to find out if there is a standard for perpendicularity of flange faces to pipe, which of course would work with that of a valve to assure that excess strain is not induced when the flanges are mated. Nothing there so far, though weld-neck flanges are butt-welded to pipe "all the time", and I can't imagine there is no standard. Don't weldments ever get rejected for being out-of-square? If they do, why?
I've been to the piping forum to find out if there is a standard for perpendicularity of flange faces to pipe, which of course would work with that of a valve to assure that excess strain is not induced when the flanges are mated. Nothing there so far, though weld-neck flanges are butt-welded to pipe "all the time", and I can't imagine there is no standard. Don't weldments ever get rejected for being out-of-square? If they do, why?





RE: Valve Flange Face Parallelism Standard
RE: Valve Flange Face Parallelism Standard
What "Code"? I'm very familiar with ASME B16.34 and somewhat familiar with B&PV and B31.3 and have yet to find a standard there. A specific reference would be a very "valuable post"
I'm wondering if parallelism between faces is simply established by face-to-face or end-to-end tolerance, typically +/- .06"(B16.10, API 6A) for valves to 10" size. For a 2" Class 1500 RF flanged valve, that would permit the angle to be 1.9 degrees, which may cause the customer to quiz the manufacturer.
RE: Valve Flange Face Parallelism Standard
If I have a perfectly straight and true piping installation and the flanges on the valve were such that it could not be dropped into a square and true set of piping flanges, within the tolerance specified in B31.3, I would reject it.