Dummy spool fabrication

[isg1968]

Can somebody direct me how the minimum lenght of small pup should be to fabricate a dummy spool?
Some experienced piping engineer said 1,5XD is a minimum lenght. Which code stats that?

Thanks for your help and answers.

 

[pennpiper]

Maybe I don't fully understand your problem/question.
However i will offer the following:
A- The "Dummy Spool Piece" by definition is intended to replace something else and therefore should have the same length as that other item.
or
B- The minimum length of a "Dummy Spool Piece" needs to allow for bolt/stud removal and wrench clearence.
or
C- The minimum length of a "Dummy Spool Piece" needs to be fabricated with 1" minimum between welds.
or
D. Other factors

Which one best fits your situation?

 

[Cockroach]

I don't think there is a minimum length by code, perhaps this 1.5D thing is simply a rule of thumb.

When I have designed spools, the bolted type with either a RTJ or RF profile, obviously you need the distance in the saddle long enough to accept the bolting, wrenches for make-up and clearance. I have typically added the length of a socket head plus an inch times two, one for each flange bolting. I believe this works out "roughly" less than 1.5D, but not by much.

Approach the design by using practical sense. What is needed to get the spool into position, then secured?

Hope this helps.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[rconner]

I guess I must admit (like another responder) I don't know exactly what your needs are here from the description provided. However, one would think minimum lengths for various configurations of flanged by flanged end pipes (your "spool"?) could be obtained from prospective manufacturers/fabricators (e.g. if the material is ductile iron piping Table 8-5 at

http://www.acipco.com/adip/pipe/flanged/specs.cfm,

or for large diameter static castings at

http://www.acipco.com/adip/pipe/flanged/shortlengths.cfm).

That being said, it may be possible, if some space can somehow be created between flanges/gaskets etc. or with various proprietary field-adaptable flanges or flanged adapters to disassemble/reassemble even very short axial length (wafer-type) items in some cases, such as various thickness "flange fillers" (see Table 6-18 at

http://www.acipco.com/adip/products/Sect6.pdf)

or "flanged dutchmen". I would note the shortest length available may or may not be the most economical to manufacture or easiest to assemble/deal with in the field. I agree with the responder who also said it is a good idea to think about such practical things as field bolt or stud insertion, and/or tightening etc. when designing systems/ordering very small length items to be assembled and/or disassembled etc.

 

[StephenA]

If this is a welded pup, then 1.5D is a good rule of thumb. Smaller than that and the built in rolling stresses / strains can distort the shape.

 

[isg1968]

I apologiise for comming back to make my question understandable.
In fact in many cases, during fabrication shop we need to extand spool by means of adding a small pup, whatever the reason. So it seems that this pup does not come over 1.5D in length . My concern is to know the code requieres that or that is just an agreement between client and the contractor .