We see many vessels with rings for vacuum support. I think the "code" reqirement is a gray area because it is under the +/-15 psi cutoff. We review the vessel based on the operating conditions, and if the calcs. say X vacuum is acceptable, that is what we allow.
Anyone have experience with a vessel (ca 1980) that has a U-1 indicating full vacuum not even being close under the current code? Still has original thickness, looks good, and is sufficiently thick for the pressure rating. BUT, the vacuum is the issue. Evaluating to origianl code is not an...
