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#37920 - 09/14/10 10:02 AM expansion loop sizing
NISHIT86 Offline

Registered: 08/13/10
Posts: 20
Hello to every one,

I have certain queries regarding pipings which are of long run and subjected to 600 Deg C.
1)what is the maximum expansion value that the loop must be designed to absob?
2) During change in the direction of piping, what is the limit for maximum allowable expansion in axial direction of pipe?
3) Provide me tips or relevant link which would inform me on sizing of expansion loops.

Thanks in advance for your guidance

#37922 - 09/14/10 11:43 AM Re: expansion loop sizing [Re: NISHIT86]
Jozm Offline

Registered: 05/19/07
Posts: 101
Loc: Canada
Hi Nishit86
1) l2=l1*alpha*(t2-t1)
2) supports should be stay on the structural beams after sliding.
3) download pipedata for 30 days free....

#37933 - 09/15/10 10:08 AM Re: expansion loop sizing [Re: Jozm]
NISHIT86 Offline

Registered: 08/13/10
Posts: 20

Hi Jozm,

I understand your point to claculate expansion value based on metal temp. & corrosponding coefficient of thermal expansion. But my query is that whether is there any rule suggesting maximum expansion value that the loop can aborb.

Also I found in flour pipe stress design guide that in cahnge in direction of pipe the maximium allowed thermal expansion is 5 inch. It also suggested that for expansion loop, the thermal expansion going into the loop shoud be limited to 12 inch.

Wheter have you come across such articles or facts?

Thanks mate.

#37936 - 09/15/10 10:28 AM Re: expansion loop sizing [Re: NISHIT86]
Dave Diehl Offline


Registered: 12/14/99
Posts: 2382
Loc: Houston, TX, USA
I, too, have "heard" of that 12 inch limit. That's 6 inches on either side of a full loop. This is close to the 5 inch limit you mention. Long rack runs will have anchors along the way to stablize the line. The spacing of these anchors will break the long run into shorter runs, each which grow no more than 12 inches. The point of 5 or 6 inch growth is to keep the support (and pipe) from clashing or falling.
Again, that's what I've heard.
Dave Diehl

#37954 - 09/16/10 11:33 AM Re: expansion loop sizing [Re: Dave Diehl]
Bob Zimmerman Offline

Registered: 12/29/99
Posts: 188
Loc: Houston,TX,USA
The numbers you mentions are just "rules of thumb" so shoes commonly shown in the generic pipe supprt standands can be used. In addition companies set generic clearance limits so loops, etc. will not bump into anything when the piping expands.

There is no limit other than practical shoe lengths, clearance to freely expand, shoes/supports stay on the structure, and stresses are within allowables.

I have designed non-symmetric loops to accomodate 34" (860mm) of expansion from one side. And I am sure many other stress engineers have "fish stories" that could easily exceed this benchmark.

Edited by Bob Zimmerman (09/16/10 11:36 AM)
Bob Zimmerman, P.E.
Vice President of The Piping Stress International Association (The PSI)

#39757 - 12/26/10 09:47 AM Re: expansion loop sizing [Re: Bob Zimmerman]
sillyman Offline

Registered: 06/06/09
Posts: 128
Loc: Australia
Dear Members,

So from the above discussion, it seems that the parameters that limits the piping expansion is allowable stress limit and pipe clashing. (i.e.) the pipe expansion shall be allowed till it reaches a maximum stress value or clash with the adjacent pipe..

Please clarify...
Knowledge is nothing unless it is shared

#39760 - 12/27/10 12:07 AM Re: expansion loop sizing [Re: sillyman]
Rajinder Singh Offline

Registered: 07/25/06
Posts: 55
Loc: New Delhi
....and availability of required shoe length.


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