I am currently evaluating an existing 20" 304 ss steam line that appears to have yielded. A vertical loop is supported at the top center by a dual type F can setup with a pre-insulated slide support(the pipe is not guided). Upon a recent shutdown the pipe drifted approximately 12" laterally to one side of the support creating unequal spring loading. Other info that I have been given leads me to believe that support friction elswhere in the piping system may have contributed to the problem. I was told that the crew at the facility was unable to fully center the pipe on the support due to pipe stress. This is a test facility that has been operating for about 5 years at approximately 40 cycles per year with a max operating temp of 750 F.

Is it possible for a poorly supported system to induce yielding or is it likely that the problem lies elsewhere? The stress analysis of the system predicts a max stress ratio of 80% of the b31.1 allowable.