Pup Spool maximum length 1

[Lizardus]

Hi,

I am trying to find out if there is a regulation in regards to the maximum length of a pup spool. I have tried looking through ASME B31.3 and found nothing. Is there an "official" name for a pup?

Thank you.

 

[LittleInch]

Yes, it's called a piece of pipe. There is no maximum lenght. There is a generally recognised minimum length of 1D between flange welds, but this is a workmanship limit and not defined in 31.3 as far as I know.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[pennpiper]

Try Here:

http://pipingdesigners.com/phpBB3/viewtopic.php?f=1&t=1793&hilit=Pup

http://pipingdesigners.com/phpBB3/viewtopic.php?f=14&t=1849&hilit=Pup

http://www.eng-tips.com/viewthread.cfm?qid=166436

http://www.eng-tips.com/viewthread.cfm?qid=220579

http://www.eng-tips.com/viewthread.cfm?qid=242240

http://www.eng-tips.com/viewthread.cfm?qid=238880

There is lots more if you use "Search" at the top of the screen.


prognosis: Lead or Lag

 

[LittleInch]

Just to clarify, I didn't mean to say that a pipe was required between fittings and indeed you can go fitting to fitting, but if you need a pipe between fittings (flanges) due to other dimensions, then the minimum size of the pipe should be 1D.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[pennpiper]

Littleinch,
You appear to be taking a very rigid position on the minimum distance between two Circumferential (Butt) Welds.
One diameter may be what you or your Company prefers to use but there is nothing in the ASME Code or API Standard to support that.
The 1D Rule starts to lose it's validity when you get much over 2"(DN50). It really gets ridiculous when you get to 24"(DN600) or above.

Some people (me included) prefer to use something that is more logical and practical. This is based on the wall thickness of the material (pipe) and has nothing to do with the Diameter of the pipe.

Most of the time I set 5t (five times the wall thickness of the pipe) as the working minimum distance between welds. With approval I have sometimes allowed 3t as a bare minimum. The 3t situation may result in an overlap of the Heat affected Zone and require PWHT. If the Piping is going to require PWHT anyway then there is no added charge.

prognosis: Lead or Lag

 

[LittleInch]

I fully accept there is no specified min distance and you can make a decent case for much less but IMHO you should start at 1D and work back from there. Any way the op actually asked for max length, which IMO is unlimited.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[RandomAxe]

There is no max length that I have heard of. Generally linepipe comes in lengths of approx 12m so I suppose that might limit you, thats a fairly long pup piece though...

With regards to minimum length, as mentioned above any general rules of thumb will only apply over a certain range of ODs. Another rule of thumb I have heard is 2xWT toe-to-toe. The main requirement is to ensure that there is no interaction between the HAZ's.