[warren cox]

I am adding supports to a 3″ drain line. Is there a minimum distance for hangers to allow movement?
The line is 85 degress process drains. But height restiction is limited. I am adding a full restraint at certain intervals in the line but hangers in between.

[James Pennock]

Warren203,
Your post leaves us with some questions:
1- What temperature scale is the 85 degrees, F or C?
2- What is the material and construction of the 3″ line?
3- What is the commodity in the line?
4- What kind of structure or building is this?
5- Is this onshore or off shore?

FYI, this is my post # 1000 on pipingdesigners.com/wp/ but there is no prize, sorry.

[warren cox]

Hi
The temp is in degree C (85)
The pipe is Stainless 316L fully weleded
The commodity is Process Drains
The building is Steel construction – Pharmaceutical plant
On shore

Thanks

[James Pennock]

We are handicapped by not being able to see the complete routing (configuration) and all the potential hanger points.
Based on the information I would only have lateral restrictions at the origin and the terminus points all other supports would be free to move and flex with the fluxing temperature. It is a simple drain and you do not need to make it complicated.

[Mark Layport]

In “General” I agree with Mr JOP, but there are 2 more issues to look at. S.Stl., at the temp.s you state, grows about 1.2″ per 100 ft.- 32% more then regular C. Stl. piping at that temp.The other issue, that seems to be skimmed over, “Process Drain” …is this just waste water, OR something that is REAL hazardous? IF hazardous then I’d look at doing a stress check on the whole system! SO as stated the system configuration and support points would be VERY important. …Without knowing more I’d have to assume the more restrictive design effort. …My $0.02

[warren cox]

The drains are Process Drains – Non Hazadous.
The question is maybe misunderstood. The question was regarding the length of the hanger rods themselves.
Is there a minimum length of hanager rod distance? My stress engineer believes that there is a percentage formula for minimum lengths.

Any ideas?

[James Pennock]

The true minimum length of any Hanger is governed by the Hardware selection.
This would include:
Element A – the top attachment element (there are many choices)
Element B – the intermediate element (normally plain or fully threaded rod)
Element C – the lower pipe attachment element (there are many choices)

If the Element C is an under pipe roller support then the pipe will allow required movement during the temperature swings. (example: ardware&biw=1024&bih=609&tbm=isch&tbo=u&source=univ&sa=X&ved=0CFUQsARqFQoTCLfg2Oe678cCFYgdHgodl2UAxA#imgrc=2kIeYDHpwx431M%3A

Go here for other examples:
https://www.google.com/search?q=pipe+hanger+hardware&biw=1024&bih=609&tbm=isch&tbo=u&source=univ&sa=X&ved=0CFUQsARqFQoTCLfg2Oe678cCFYgdHgodl2UAxA#imgrc=qRlTkbPDY7Mr-M%3A

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