fillet weld size for slip on flanges B31.1

[bhart192]

looking at details acceptable fillet weld size detail indicates X mim = 1.4 Tn ; tn is defined as nominal pipe wall thickness , is TN the required design wall t or the actual pipe wall t

 

[pennpiper]

A fillet weld for a Slip-On Flange cannot be 1.4 times the thickness of the pipe wall.
This link is from ASME B31.3 but the pipe and the flange are the same for both B31.1 and B31.3

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http://

http://www.lanl.gov/orgs/eng/engsta...jISoBg&usg=AFQjCNHdb7UOzEaHF7N0InN9R4AdlSkujQ

Sometimes its possible to do all the right things and still get bad results

 

[SnTMan]

bhart192, since Sec VIII, Div 1 was revised to match, I have been taking it as nom wall less corrosion.

pennpiper, this is for the outside fillet.

Regards,

Mike

 

[Duwe6]

Gotta disagree with pennpiper, but I'll bet it is over terminology. FILLET WELD size in B31 pipe codes figured by the leg length -- see page 3 of pennpiper's attachment. Thus the minimum Fillet size is 1.4 x nominal wall. The 'weld size' is figured as the theoretical/effective throat so min 'weld size' is 1.0 x nominal wall. And that's the entire reason for the 1.4 x; it gives a weld as strong as the pipe.

And back to the original question; Any SO flange welds that are at least 1.4 x nominal pipe wall are acceptable; IF the pipe can be proved to be thinner than Nominal [12½% below nominal is allowed on the SA-53 and SA-106 pipe spec's] a weld that is 1.4 x Actual Wall is acceptable.

In no case is 1.4 x Actual Wall thickness required for pipe that is actually thicker than nominal. The reason is simple; that extra pipe thickness was not used for figuring the MAWP of that pipe system. ASME design rules use Nominal Wall.