accounting for thermal expansion in this shape 2

[MartinLe]

There's decent formulas and rules of the thumb about for using 90° bends to absorb thermal expansion in pipelines.

How to account for this shape:

The pipeline follows the parapet on the top of a series of vessels.

the pipe is stainless steel, DN 250, to the left it's ~7m to a fixed point (pipe runs through hole in ground) to the right it's ~16m to the next semicircle like the one in the picture. there are four more similar arches long the pipeline

I need to account for 1mm/m of thermal expansion.

I want to avoid expansion joints.

Surely at these obtuse angels these arches are not as good at absorbing expansion as a 90° bend with a long enough leg would be.

My first idea is to fix the middle of the arches and middle of the long segments, using 2D gliding supports in between (stainless steel supports on PTFE). what would be the peak stress in the pipeline due to thermal expansion?

 

[LittleInch]

The other thing to think about here is whether you need to anchor the pipes somewhere between each run or prevent axial movement from the mid point, but allow horizontal movement.

If you have four of these in a row as you state then they might end up finding the weakest link and concentrating all the expansion into one location.

But for sure I would only be looking at 30 degrees of expansion or contraction, not 60.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

If there are 4 then each should be anchored individually to ensure uniform distribution of displacements.

 

[MartinLe]

There are five in a row, in all except the first the left corner of the arch is somewhat fixed (because of branching pipes entering drilled holes in the building)

The pipe is redundant, 90+% of the time it will just sit and be filled with water. In addition to the control of the trace heating, each segment of pipe gets it's own temperature guard TA L.

My thinking right now is to
- only consider +20 to +40° in elongation,
- +20 to 0 as contraction
- make clear to the client that there is a risk of damage to the pipe if the trace heating fails in severe winter while the pipe is not in operation

As for the pipe supports, 1 fixed between to tanks arches (in the middle if possible, near where I'm constrained if not), other supports as gliders.

Thanks for the many helpful pointers!