SandeepTiwana,

Based on what you say, the previous analyis or site work(installing) has not been properly done, or piping has been damaged due to primary or secondary stresses.

Owner or operator may have "hanger record sheet"(or whatever it called), and it's good to track how spring supports changed.

My opinion was if you were not have authority to change pre-installed spring, you should not fool with pre-defined spring load. In your case you should do on your own analysis.

For what you say 'CAESAR-II gives 2 different sizes.' if the line expand like a bow or the support point has rotation, that could happen. Place guide or stopper near there and for the spring please follow what Micheal suggested.(whatch for the spring travel range and variability though)