Slip on Flange Placement Rules 2

beh188, you don't mention a code or standard you may be working to, but for Sec VIII, UW-21 applies.

My own personal practice is weld leg + 1/8" to help avoid damage to the raised face due to misdirected molten metal etc.

Regards,

Mike

I am working to ASME B31.3, which as far as I know does not provide guidance on this. I will check out VIII UW-21.

beh188,
Your question comes up often. below is the same question from a year or so back and my answer.I hope this helps.
Pennpiper

Slip-On Flange Set Back
The Question:
I am trying to find information on the set back dimensions when welding slip-on flanges to fittings (Ells, Tees, Reducers, etc.). Also are the dimensions for the set back dimension for slip on flanges supported by any standard (example in ASME guide)?

My answer:
I am sorry but I do not think you (or anyone else) will be able to find this issue in any of the existing Codes. So! How is it set?
A Slip-On Flange will come in different Flange Ratings. But the Flange Rating has nothing to do with the placement.

A Slip-On Flange can be put on most of the fittings that are commonly used in a piping system. But the fittings themselves have little to do with the placement. The only impact the fitting has is on Short Radius ELLs and some TEEs where O.D. of two Slip-On flanges might run into each other.

So, what is the Setback or Placement Criteria based on?

The set back dimension or placement criteria is based on the desire to avoid causing damage to the Gasket surface or contact face of the flange.

To do this the setback is constructed based on the wall thickness of the pipe (or fitting) the Slip-On flange is attached to. The weld that attaches a Slip-On Flange to another object is a Fillet weld. The Fillet weld size criteria in this case are equal to the wall thickness of the pipe or fitting. You then add 1/8" for additional clearance set-back to insure that weld spatter does not damage the Gasket Face.

So if you are attaching a Slip-On Flange to a pipe (or fitting) with a 3/8" wall you would add the 3/8" wall to the 1/8" clearance set-back and have the 1/2" placement dimension.

The Mega-Engineering companies of the world do not want every Tom, Dick, Mary or Larry wasting time doing these calculations every time a Slip-On flange is required. First it would be highly prone to error. Second, it is a waste of time. It also leads to conflict between the Designer who uses his own criteria and then a Checker who uses different criteria.

What they do is create a chart they double and triple check it and then finally issue it to all piping designers as the Company Practice. You used it (Designers and Checkers alike) or justified why you could not or would not use it. In most all cases the company won all the arguments or discussions.

Thanks for the good information.