Welding 2" Pipe into 3"x4" A234 WPB Reducer

[jives]

I'm in the process of designing some piping modifications for a replacement pump. I'm somewhat limited, in the vertical dimension, for my discharge pipe and fittings. Is it possible to weld a 2" pipe into the side of a A234 WPB 4" x 3" reducer without sacrificing the integrity of the reducer? Essentially what I would like to do is turn my 4" x 3" reducer into a 4" x 3" reducgin tee with a 2" side outlet. The reducer length is standard at 4".

Otherwise, I will install a 4" x 2" outlet reducing tee downstream of the 4" x 3" reducer.

Jonathan Ives
Project Engineer
Transalta, Alberta Thermal Plants
Duffield, Alberta

 

[jives]

What I am asking, is would it be possible to "stub-in" to a 4" x 3" reducer with a 2" pipe ?

The application is water at up to 180 F and 170 psi on Standard Weight A234 fitting

Jonathan Ives
Project Engineer
Transalta, Alberta Thermal Plants
Duffield, Alberta

 

[jte]

Jonathan-

Possible, yes, but difficult to justify. You didn't state whether you are dealing with a concentric or eccentric reducer. Clearly the problem is a bit simpler if you are considering the "straight" side of an eccentric reducer. I've seen it done many times, but have never signed off on paperwork authorizing this type of design myself (not for lack of opportunities…). Simply put, how do you calculate the required reinforcement? Most fittings are proprietary designs based not on calc's but on proof testing. See John Breen's post in thread378-181777. So, since you are not the fitting manufacturer's engineer, how can you prove that cutting a hole in the side of the fitting will not change its pressure rating? Even with all the reinforcement in the world. You could put an 'olet type of integrally reinforced branch connection on… But those designs are proof tested as well. They may well meet area reinforcing requirements, but let me know if you find a document stating how much area is being replaced, and in what plane.

So, bottom line is that it can be done and is done fairly commonly. But I would like to see the engineering calc's which back up the design…

jt

 

[XELR8]

I would need to know much more information about your design condidtions to make a lengthy design invetsigation:

Here is some quick advice:
1) The structural integrity of the reducer will be fine for your pressure and temperture. Pipe fitting wall thickness' are over designed primarily for welding and mechanical loads.
2) It's going to look bad in the field. Do you want your name on this design?
3) You won't save yourself any welding if your reducer is not already installed. Move your reducer as you suggest.
4) For the pipe stress problems I would be more concerned about, thermal conditions in Alberta, weld stress from the heat affected zone, get yourself a good welder and do a hydrotest.
5) Make sure the OD of the 2" pipe will not exceed your 3x4 reducer cross sectional area. This weld outline will be very unusual.

Good Luck.