What I would do, without affecting the structural integrity of the pipe and flanges (or at least, affecting them as little as possible), is to weld a piece of plate 0,25 inches thick and three inches wider than the flange thickness, over the outer surface of the pipe end. In this manner, you'll have an OD which is 0,5 inches larger than the original one. Then, weld the flange on the plate. The details on how to fix and weld the piece of plate on the pipe you can figure them out.
From the size of the pipe, I guess that it belongs to a low pressure and temperature piping system, so it shouldn't be major problems in doing that way.
Does anybody have a better idea?
Giovanni S. Crisi
Sao Paulo - Brazil
I don't know if this is a better idea, but it is what I have done when welding slip on flanges (SOF) in the past:
1.) There is always a gap when using SOF's. The gap is "split" to give you a 1/8" gap all around by inserting welding wire, SMAW electrodes, etc., or whatever it takes to provide a uniform gap, then the flange is tack welded (after alignment). There are numerous ways to align the flange, but that is another issue.
2.) The SOF's are typicaly fillet welded although PJP/CJP groove welds are not uncommon were higher pressures are encountered. Preheating was never required unless we were at temperatures below 50 degrees.
3.) The structural integrity of the pipe has never been an issue in all the years I welded these things. It depends on what the alloy of the pipe is, we commonly joined most of the standard pipe materials without any problems and MT/PT was often performed to verify the welds integrity.
You are correct in stating that there is a 1/8" gap, as the 42" SO flange has an ID of 42.25" +- 1/8" tolerance- -
My question really is, if you think that having a 1/4" gap (instead of 1/8") will create any problems other than having to use more material and time by additional runs. In other words, will the line be affected unfavorably.
This line is for water, 60º - 80º F. - 150 psi
I don't think the extra space will be problamatic, some SOF's came with ID's that were close to the ID tolerances you mentioned, although this was rare. Additional passes were applied was all. For that pressure, with a service for water, I do not see any problems.
Is the SOF being offset (eccentric in lieu of concentric) in relation to the OD of the pipe for some reason?
Thanks to all that replied - We thought it would be ok, but is nice to have another opinion.
That large of a gap won't hurt anything, except weld time. It will take longer to fill it out, that's all. Put two passes on the inside & weld the outside to spec & go with it.
Hi
I believe that in your proposed service, most things will hold, but there are a number of issues that you should think of.
1) The greatest stresses in most flanged joints (raised face) are applied by the bolt torques tending to "bend" the flanges. Under this type of loading, the flange with the larger ID will tend to experience greater "tearing" forces on the weld away from the flange face. This will probably be a minor issue.
2) If you have substantial stresses induced through the pipe, as may be the case with a "cold set" pipe, or poorly installed pipe, the forces on the welds will tend to have a larger tensile component, rather than a shear force component as would be the case with a closer fitting flange. Again, I believe that this will be a minor effect.
3) Close quality control will have to be used on measuring of the weld sizes afterwards because a weld that appears adequate may only have a very small effective throat thickness. This will especially be the case in the weld away from the flange face. I believe that this is the biggest issue.
Regards
Niekie Jooste
Hi Niekie,
Your post raised a question for me.
Is there a general rule of thumb pertaining to gap and fillet size, such as increasing the fillet size by the amount of the gap?
Dale Simonds
D1.1:2000 Section 5.22.1 Allows for maximum root openings in fillet welds 3/16 for materials up to 3" T. If the separtaion is greated than 1/16" the leg of the fillet weld shall be increased by the amount of the root opening.
Also Annex I explains the measurement of Effective Throat Fillet welds in Skewed T-Joints.
Hope this helps
As stated by the other post, the bottom line is to have the correct throat thickness. You can generally get this by increasing the leg length by the amount of the gap.
Regards
Niekie Jooste
I noticed some of you are quoting from the D1.1 again.
Please refer to AWS D1.1:2000, 1.1.1 (3).
Sorry for not being clear, reference to the D1.1 was only with regards to the post on fillet weld throat.
Hi There old pal,
AWS D1.1 deals with structural components. You are welding a slip on flange on a pipe I understand this is either an SA 53B or a SA 106B
P1 Group 1 pipe grades.I suspect you are welding a 150# slip on flange
correct?
If all above are correct than the next question is what type of commodity is the line coing to transport? & at what pressures?
Usually your work packages will include LDT tables (line designation tables)& ISO's for field installation or cut sheets for shop fab.
In you case considering new piping field installation you are operating under ASME B 31.3 codes for refinery or powerplant piping you could also operate under B31.1 for high pressure steam piping.And for pipe line piping you need to refer to API 1104 (4 hour course offered by AWS in conjuction with CWI seminar).
Once you determine what applications your project falls under take the next step(in our case lets assume we oprate under B31.3).150# flanges are hydroed at 450 PSIG .The max gap tolerances w fit up for slip on flanges is 1/8" ,in your caseyou can set the gap with welding rods as suggested by others.
It isn't advisable to add excessive weld deposit for the following reasons:
1) Distortion 2) exessive heat input affect HAZ and fusion zones caused by chemical changes called add mixture
Max weld size is ( B 31.3 and API 1104) either 1.4xpipe thickness or 1X flange thickness and in addition ( when operating turbulent flow) !/4 bead on the inner circumferance of pipe and flange mating surface.
Remember more weld deposit can be even worse than too little deposit.
Good Luck
Joe Valdez
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