Weld Neck Flanges / ASME B16.5 / MSS SP-44
Weld Neck Flanges / ASME B16.5 / MSS SP-44
(OP)
6" standard ASTM A105, Gr. B, ANSI 300, weld neck flanges were used in a standard wall X52 natural gas piping system. I need to calculate the percentage of SMYS (%SMYS) when the system operates at its MAOP. The weld neck flange has a minimum neck length of 1/4" per Fig. II-7 of ASME B16.5 (see attached). Do I calculate %SMYS (Hoop stress at MAOP / SMYS) for this short Gr. B section of the flange or state that it has the same %SMYS as the pipe it is connected to? Is this Gr. B flange the weak point in my system? Why isn't high yield strength carbon steel (ASTM A694)listed in Table 1A of ASME B16.5?





RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
To be honest I've never been entirely sure if having, as I think you're getting at , a thin strip of metal with a lower SMYS than the pipe is a real problem or a theoretical one. I've normally just made sure we specify and order A694 FXX flanges.
Why it isn't in 16.5 - don't know, but it is a listed referenced standard in MSS SP44.
It all depends which code this is designed to - B31.3 and you would get away with it as the allowable stress of X52 is actually the same as A105 at "normal" temperature, but if its 31.8 then you have issues.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
How long is the reduced wall thickness section? (Not 1/4 inch, right?)
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
IMHO in practice it probably doesn't make big difference, but it is just not right.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
And, whenever someone thinks this is not allowed, one can always resort to para. 302.2.2.
This is how I do it. Never had a problem with it.
The rest of the flange (starting from where the hub tapers away) obviously is goverend by the p,T-rating of the flange itself.
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
Hopefully you wont be above 72% of SMYS....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
If the pressure rating of a flange is based on the mated face properties (gasket, number of bolts, etc), why would anyone use a high yield strength slip-on flange? Is is due to welding specs? I don't see the advantage of using high yield strength slip-on flanges.
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
I don't see any advantages either for a slip on flange, only for a WN
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44
RE: Weld Neck Flanges / ASME B16.5 / MSS SP-44