I have 2 Elbows and a pup piece inbetween. Whats the minimun length that it can be what governs it. In this case its 12" Sch20 C.S.
Evertone i asked seems to have a different answer.

The length of pups’ rule of thumb was 1.5dia or min 6" (152 frog dimensions) the length is based on fabrication .Anything less then 6" of 4" pipe is hard to do field end preps and field welds.
Did you skip the piping course?

I agree with ollie on the 6" / 1 1/2 D rule for pups ...

Having said that, I've seen make-up spools that were pretty short. 2" / 50 mm pipe between weld necks.

I'm no welding expert, but I think the trick used was to make the first weld to a longer piece of pipe, then cut the pipe to length, then weld the second flange on. That way you get a "normal" heat pattern in both welds as there's more material to carry the heat away.


One other question though, can anyone tell me where the name PUP piece originated from?

Is it an abbreviation, an achronynm or a made up word??

WWIU

Ollie,

I asked the question because I have always believed it to be 50mm. ie. the min the shop could fabricate. I am being told otherwise and i disagree. i just wanted other views on it to make my case. There are no field welds on the job so thats not an issue.

Minimum spacing between circumferential welds joints shall be 2" or 6 times the wall thickness of the pipe, whichever is greater

Going back to whichwayisup's question. What does PUP stand for? If it is for a Make-Up Piece, why isnt it called a MUP?

[b]thehat ,It is not a glib answer. What you should realize that companies have standards. One company may request a 100mm min length pup, they may ask for a certain arrangement for their utility station a minimum with draw length on an exchanger .You get the idea?
I am not saying that this web page is the wrong place to ask question, but be aware your lead piper is the one that sets the company standards for his drawing office team. I would never allow one of my pipers to search the web for a question that is stated in the client or company specs. Ask questions within your team; remember the guy that signs your timesheet normally knows the right answers.[/b]

isn't pup piece short for Dutchmen?

@Ollie. If the answer lay in the specs then I wouldnt have to ask the question or if there were underlying circumstances like a withdrawl length etc.. i wouldnt need to either. The reason I asked is because I need to make a turn in a short space, ie. a 60mm PUP piece would suit me perfectly, if not then i got ot look at an alternative. The specs dont give the answer, so i turned to 2 senior pipers one of the my lead and posed the question, 2 different answers i got, none of them wrong but none of them right for my situation. The decision has been basicaly left to me.
As for as i am concerned the ultimate governing factor is the welds and the minimum distance between the welds, while taking into the consideration the shops ability to fabricate it. I believed this length to be 50mm. So I tried to find something to back it up. So i pose the question here to find info. Im not going to turn around when asked why I made it 60mm and say i read it on piping designers.com, give me some credit.
If on this forum I get similar answers that seem to agree with my thinkling then i will investigate some thing that backs my decision.
The point I am making is, you have to respect peoples questions, you have to assume they looked in the specs, assume they have asked a lead or a more senior designer(unless the question screams novice or they are known to be a novice), were not stupid and lets face it no designer knows evertything there is to know about piping off the top of there head. So comments like did you skip the piping course are not helpful. So unless your comment is helpful or genuinely funny keep them to your self.

Thehat
I never said the answer of pup length is in the Specs . Have you checked can you substitute the LR for SR El? What did the engineer say that ultimately will take responsibility for the project.
Side bar
If you take feelings into a design office someone is sure to hurt them

I don't claim to be an expert in minimum "pup" length between small steel weld fittings nor codes related to same, 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")? If the resulting centerline-to-centerline distance between the outer ell ends with standard ells was too short, could the ends of one or two longer radii ells be cut and beveled as necessary, again to be joined with only one weld to effect a little longer needed centerline distance?
While I likewise don't know origin of term, I've always wondered whether "pup" was sort of a shortening of "plain end by plain end" (pipe or nipple etc.).

If you are looking for a solution to your problem I suggest the following:

you have: 2x 12" 90 ell. + 60mm pup = 974mm between centres.

If you want to kick over the line hor or vert then use 2 x 45 ell + 593mm pup

if you are changing direction then use a rolled 90 ell + 45 + 326mm pup

However, if you are looking for a stick to beat your senior pipers with then I'm afraid that I can't help you there.

Gentlemen (and ladies)

These rules of thumb are fine but space constraints do not always permit this luxury.

The bare minimum you can make a pup can be determined through a simple calculation.

L = 4xt

where....

L = the length of pipe between the edge of welds
t = the pipe wall thickness

Note - as this formula gives you the distance from the edge of the welds, you'll have to do a little trigonometry to determine the edge of weld to center of weld dimension.

Disclaimer - the above was from a company I worked for years ago. Check your company's standards for their specific rules and requirements.

We always called them spools, "pup" is a bit too cutesy-sounding.

The ultimate answer is in the ASME codes (heat-affected zones), surely everyone here is familiar with these.

http://www.asme.org/Communities/History ... istory.cfm

Hey guys,
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.