Slip-on Flange Weld Detailing
Slip-on Flange Weld Detailing
(OP)
I'm just curious how other people detail welds on slip-on flanges. Specifically, with reference to Fig UW-21(1) in ASME B&PV Code Section VIII Div 1.
Suppose you have a 4" Sch 80 pipe and need a 0.337" fillet weld on the inside. Do you show a decimal dimension for weld size? Show it as "full"? Show 5/16" or 11/32"? The difference between flange ID and pipe ID is slightly less than 3/8", so theoretically, it can't be 3/8".
On the back side, the fillet weld size is limited by the hub thickness, but per the flange catalog, the hub "may" be tapered up to 7 degrees, and only the untapered diameter is shown in the flange dimensions. So do you assume it's tapered, assume it's not, show it as "full" or what? That taper, or lack thereof, makes a 0.17" difference in the weld size on a 24" 150# flange.
Suppose you have a 4" Sch 80 pipe and need a 0.337" fillet weld on the inside. Do you show a decimal dimension for weld size? Show it as "full"? Show 5/16" or 11/32"? The difference between flange ID and pipe ID is slightly less than 3/8", so theoretically, it can't be 3/8".
On the back side, the fillet weld size is limited by the hub thickness, but per the flange catalog, the hub "may" be tapered up to 7 degrees, and only the untapered diameter is shown in the flange dimensions. So do you assume it's tapered, assume it's not, show it as "full" or what? That taper, or lack thereof, makes a 0.17" difference in the weld size on a 24" 150# flange.





RE: Slip-on Flange Weld Detailing
RE: Slip-on Flange Weld Detailing
RE: Slip-on Flange Weld Detailing
So, my practice is to add the corrosion to the 1/4" inside fillet when the pipe neck allows, and to not do so when it doesn't.
For the outside fillet, my practice at my most recent employer, due to an overly legalistic frame of mind by QC, is to refer to a note at the fillet symbol. Note states something like "Minimum of 1/2" or hub small end thickness". 1/2" being an example of course of the calculated thickness required by UW-21. Again, not clear if the "tn" used as the basis is in the corroded condition or not. I never dimension welds in increments smaller than 1/16".
Yuk. Miss the old days when it was just neck x neck.
Really good reason to just use weld necks, IMO :)
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Slip-on Flange Weld Detailing
RE: Slip-on Flange Weld Detailing
I agree with the 1/4" minimum fillet weld on the ID. For the OD, I typically dimension the calculated value and specify that it is the minimum and let the welder use their judgement on the actual or maximum dimension considering hub thickness. I like to let the welder know what is required per code rather than just some nominal size.
RE: Slip-on Flange Weld Detailing
Regards
r6155
RE: Slip-on Flange Weld Detailing
The welder only knows what is provided by the drawings, more than that, is wishful thinking.
Rarely have I been on a project where the welder or anyone on the field crew even knew what pressure piping code they were welding to. "Its just pipe." is the response I usually hear.
Best regards - Al