A good pup length rule of thumb is to not use less than than the size of the pipe. Example: If you have a 2" dia. pipe than your pup should not be less than 2". If you have a 10" pipe than your pup should not be less than 10" This is not a dead set rule but, its a good simple design standard. It gets really hard to weld small pieces of pipe.
Hmmm...interesting some of the thoughts
12 years 11 months ago #3813
Thank you received: 5
Hmmm...interesting some of the thoughts here. I myself used the 3" min. this was dictated to me years ago by a major construction company. Then later I was talking to a welding engineer about the same subject and he agreed, BUT said "if" I was fighting 1/16th of an inch in a tight configuration I could go to 2" min. Basically what your trying to watch out for is not overlapping the heat affected zone ...which can cause brittleness in the weld. On a gravity drain, probably not a big deal. High pressure steam is another story!
My point here is you have to be flexible! Know when you can "fudge" abit and when you can't. Seem to me that what makes a good designer.
...AND whether you call it a pup or a spool pc. ...again you need to be flexible. I basically try to "know" who I'm talking with and try to talk "to him" ...whether it's the engineer or the welder in the field. My $0.02 anyway. ...Mark
....but I was just curious if a welder could get an electrode in there to make one good weld why couldn't one ell simply be welded to another, with one weld and without any "pup" at all (in effect a minimum "pup" length of about nothing, and which scheme if possible would appear to minimize at least any issues of two close together welds on a very short "pup")? .....
Fitting to fitting is perfectly acceptable, but not always possible, ie when coming off a rack to a defined height, may require the use of a pup.
Other reasons for "pup" pieces, would be to allow for field fit up, such that only a small section of the design would require modification should field conditions change, due to equipment being set at incorrect height.
The field fit up reason is very important to keep in mind, as many "fast track" jobs require that piping construction isometerics are issued prior to final certified drawings being issued.
A search on Google takes
12 years 8 months ago #3893
A search on Google takes me here.
In pipeline, welded in line valves are used. Each valve comes with transition pieces or pup pieces for two reasons (as far as I know):
- Transition between different thicknesses and materials
- Preventing damages to seal and seat during welding and heat treatment.
Does anyone have a rule of thump for the length of these pup pieces ?