ASME B16.5 flange issue

[samvanwesen]

Hello,

we buy blind flanges according to B16.5, EN1092-1, etc. We make thermowells out of these flanges, and e.g. with 2500lbs full penetrant welded flanges, we get quite some distortion in the bolt holes.
For larger orders, we subcontract thermowells and we have one supplier that offers thermowells with perfect round holes. They are able to do so, because they drill the holes after welding.

Is this something we are allowed to do acc. to the b16.5 standard?
=>
Buy flanges according to B16.5 but without bolt holes. I checked with our supplier, and they will not be B16.5 marked obviously. Are we allowed to mark these B16.5 if we machine the holes after welding? Holes will be acc to the b16.5 standard.

I am curious about what is allowed and what not. If we stamp B16.5, do we need to be inspected by asme of some sort?

Thanks for your ideas.

Sam

 

[LittleInch]

Interesting.

B 16.5 isn't very prescriptive

E.g
4.2.4 Conformance. The designation B16 or B16.5
shall be applied to the flange or flanged fitting, preferably
located adjacent to the class designation, to indicate
conformance to this Standard. The use of the prefix
ASME is optional.

Appendix D relates to a QA system that is required, but so long as your flange meets the spec and is in conformance then it can be marked accordingly.

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

 

[KevinNZ]

If you are getting distortion in the holes, then will then also be distortion in other places too? e.g the gasket face.

 

[timsch]

There is no tolerance spec for the bolt hole roundness in B16.5. Obviously it's preferable to have them undistorted, but when you bore that much material out of them and then full-pen weld a bar into it, the heat input will have its effect, particularly on smaller flanges with larger stems. As long as the flange is still within spec on all critical dimensions, it's compliant with the code. Whether the customer has an issue with it is another story.