Free Thermal Analysis - How Used?

[KANN]

I've seen "Free Thermal Analysis" or "Free Thermal Expansion" referenced as a step in piping stress analysis and do not understand exactly what this means and how useful it is to perform.

Do analysts routinely use a free thermal analysis when designing a new system?

Or is it more useful in troubleshooting an existing system that is overly restrained?

Would someone describe how a free thermal analysis is performed or reference where the steps are described in some detail? What I understand is that all restraints other than supports for deadweight are removed, the operating case run. Then the thermal displacements are reviewed to aid in determining strategic locations for restraints.

 

[DSB123]

KANN,
A "Free thermal analysis" is basically the best you can achieve for a piping syste. What I mean is that the lowest thermal stresses will be established as all restraints other than anchors are removed. Basically if the piping system cannot meet the thermal stress range for this weightless thermal run (without restraints) then it cannot be made to be compliant with restraints. Years ago a free thermal analysis was the first step to check if a system had sufficient flexibility BUT with the sophisticated computers of today not many stress analysts do this calc.

Hope this helps to clarify.

 

[KANN]

DSB123,

Thank you, yes that does clarify. What I did not understand was that the dead weight supports were removed too and the piping was made weightless. I thought just the supports that were not in place for deadweight were removed.

The fact that it was a proceedure of a past era also explains why I have not been able to find much explaination of this approach in current literature and don't find it talked about much in current piping analysis discussions.

I am grateful for some feedback on this.

- Ken