Fillet Weld on a Socket Weld End Flange Calculations

My advice for you is to pay someone with adequate knowledge of welding and your specifications to solve your problem.

What does the specification say.

Where is the pressure system located?

Why do you need to bother? For tangential stress, if the pipe itself is OK, so is the part of it inside the flange, and the weld + flange gives additional area to take the load.

For longitudinal stress, you can work out the load based on pressure and pipe OD (worst case, assuming the pipe is not restrained elsewhere). It shouldn't be hard to estimate the weld area that takes the force (thickness x circumference) to get the stress. Most unlikely the stress will turn out excessive. Helped by fact that based on the pipe wall only, longitudinal stress = 0.5 x tangential stress.

I used to use a very short length of the same diameter pipe to accommodate this recessing of the pipe before welding. The length of this insert was equal to the length that I wanted the pipe recessed. i.e. for welding 2" pipe with a recess of 1/2" inside the flange, use a piece of 2" pipe 1/2" long. Insert this in the flange and rest the flange with this ring in it on the welding table or other surface. Run a couple of long tacks or stringers of the outer weld and then remove the ring. Complete your outside and inside welds and you have a perfect recess. I would make these rings on a good power hacksaw or band saw every time I had the chance for one of a size I didn't have. Different recesses too. Organized them on one of those "giant safety pins".

Many welders and pipe fitters caught onto the idea and made themselves a set!

Good Luck, Old Salt

Try to become at least a bit familiar with the Codes and Standards that govern your piping installation.

ASME B31.1 allows piping system design, construction and installation using full penetration butt welds and PROPERLY SIZED FILLET WELDS without calculation of individual weld strengths.

Of course, a qualified weld procedure and properly rated pipe flange is also required to meet the code.

thanks everyone for the input

@lyn

we cannot hire someone from outside because our contract makes it very hard, we do have certified/qualified welders on site, I have talked to them and while their experience/training tells them what to do, the "why" that I need to document is missing.

@codemaster

I was thinking the same thing about the hoop stress, but our pressure systems guru here sometimes can be over-conservative and make us jump through alot of hoops before he is satisfied. I just wanted to put a number to it so he cant ask for it later

@MJcronin

B31.3 is what the base system was originally designed to meet. I think the 328 paragraph in 31.3 allows the same, but as I am sure you are aware, the code rarely just comes out and says things and my interpretations may differ from what our pressure systems engineer reads into it