Small Hole in ASME B16.5 Blind Flange 5

[bayardwv]

I am using an 8" 150# ASME B16.5 Blind flange with a 1/2" NPT connection drilled & tapped directly into the flange 3" off center. I am being told the Flange is no longer an ASME Flange and that calculations are required. I disagree for several reasons,
1.) The Flat head formulas in UG-34 don't change when there's a hole added. The addition of the hole is addressed in UG-39, so why would the thickness of an ASME flange change?
2.) ASME B16.5 allows holes less than 3-1/2" to be added to an 8" blind flange to create a reducing flange using the published press/Temp rating. I don't see why this can't still apply to small holes that are located off center and exempt from reinf per UG-39.
3.) The design in questions is exempt from Reinforcement per UG-39 & UG-36(c)(3) which implies the material removed is not enough to affect the integrity of the part with the hole. Why would this be different on a flange?
4.) Where does Sect. VIII Div.1 or B16.5 say that a flange thickness calculations is required when a hole is added to an ASME Blind Flange.

 

[bayardwv]

moltenmetal, perfectly said!

 

[84Volumex]

Would this interpretation apply to the case of a lug being welded/screwed to the side of a blind flange for say a manway davit?

I am unable to locate any part of B16.5 that specifically includes permission to weld a lug on the side of blind flange, although I have been accused many times of having a "boy look" for things.

 

[moltenmetal]

Holes drilled between stud holes, for use as orifice taps, jack screw locations etc., can be accommodated within certain limits. What are those limits? Not sure B16.5 gives thorough answers to those questions either.

Stuff welded to the side of the flange which puts no meaningful load on the flange in service, should not cause any problems as long as the welding process doesn't affect the metallurgy of the flange itself, i.e. welds done per ASME IX and examined properly shouldn't be a problem. Little different than bolting things to the extended threads of a couple of the flange studs.

 

[keyen]

Holes drilled between stud holes, for use as orifice taps, jack screw locations etc., can be accommodated within certain limits. What are those limits? Not sure B16.5 gives thorough answers to those questions either.

Orifice flanges are covered in ASME B16.36. Drilling holes in a B16.5 flange between stud holes will make your flange not compliant with B16.5

 

[Spoonful]

Orifice flanges are covered in ASME B16.36. Drilling holes in a B16.5 flange between stud holes will make your flange not compliant with B16.5

by doing so make your flange not compliant with B16.5 but to B16.36, but isn't B16.36 flange has the same pressure temperature of B16.5?