Hello,

Shivaprakash has made many excellent comments. The first thing that I would like to suggest reinforces what Shivaprakash essentially has already said: DO NOT TRY TO SOLVE THIS PROBLEM WITH COLD SPRINGING.

As Shivaprakash has said, there are no absolute limits on thermal deflection. The design of this piping for expansion will be driven by the primary and secondary stresses. Presumably, the damaged ("sagged") piping will be repaired and the badly distorted bits will be replaced with new pipe. You probably would be best served by a complete analysis of the entire system (as modified). To limit the axial expansion displacement in any local area consider intermediate anchors (as close as practical to six degrees of fixity) and expansion loops AND GUIDES. Accommodating the expansion between the intermediate anchors with loops may mean installing some new piping in the existing system but it provides a "real" solution to the problem - cold spring is only a theoretical answer. Please read a previous thread regarding cold spring in an existing system.

I think it would be wise to do the design / analysis in steps. Try to manage the axial displacement (e.g., put in some expansion loops and guides)and then address the hanger design. Also consider that the system has a fair amount of "self springing" in it now as it has "relaxed" due to creep in local components. When you cut the piping to modify it you will release the residual cold stresses and you will be left with a system that is no longer cold sprung. PLEASE REMEMBER TO WARN THE TRADESMEN TO PLACE THE TRAVEL STOPS IN THE HANGERS BEFORE THE PIPE IS CUT - there is a lot of stored energy in those compressed springs and it can be dangerous. Also, restrain the pipe for safety while it is being worked on.

Good luck with your project.

Regards, John.