Dear all, is it normal to limit deformation of piping to 5 mm in Sustained case? Because that whats my owner said on its design basis, but it doesnt mention in what direction. Unlike in Sus + occ case it mention to limit deformation of piping to 20 mm for vertical n horisontal. I usually set the limit for Sus case in 12 mm in vertical but for others as long as it doesn't interference with other piping or support it will be ok. I need an opinion here...

Please share your opinion....Mr. Ay? Shr? Mr. John breen...? Or anybody please...

I can't answer the question, it depends on "everything".

What is the pipe diameter? 5mm for a 1 inch line is much more of a relative deflection than if the pipe was 36 inches in diameter.

What is in the pipe, gas or liquid? If the pipe contains liquid, then too much deflection could lead to ponding if the system is shut down, followed by slug flow on a restart.

There are a host of other considerations.

Hi Dylan
Sustain deformation 5mm as indicated in your client specification is for vertical direction sagging.
In general for practice for process plant 12 mm sustain sagging accepted & for power plant it is much more stringent only 3 to 5 mm sagging allowed.
Limiting sustain sag 5 mm should not be so difficult for normal piping configuration. You may add to use more supports ( some times lift off support)

Regards

Habib

Thanks Shr, ive thinking about it too, but i'm still worry because in horisontal (axis of pipe) the deformation is 27 mm....

Hi LNG
Axial movement in operating case is not at all a issue.
You can accept 100 mm axial & 25 mm lateral movement ( check project specification) in operating case provided pipe don't clash with other items & system is safe in all stress respect.

Regards

Habib

Thanks Shr, but it is in Sustained Case.....for vertical it still below 12" but in axial it is 27 mm....is it matter for sustained case?

LNG,

If you have 27mm horizontal in the sustained case, it may suggest a problem. You should check out where the movements originate since normally it should be around zero due to weight alone. Maybe you have significant pressure elongation ?

Dear Moverz,
The displacement 27 mm in Sustained Case is at Expansion Joint Node.

So is that what you would expect ? It seems a big deflection for a sustained case. Without seeing the geometry I could not comment further.

Hi LNG

You are using untied simple/universal expansion bellow. Check vendor catalogue for permissible axial movement of bellow. For untied bellow there could have serious problem in your piping system due to pressure thrust. Follow the guidelines from EJMA ( Expansion joint manufacturing association) before using expansion bellow.
Good luck.

Habib