Hi dears
would you please advise me about "HOT SUSTAIN" load case in below items:
1-when should be used this load case?
2-what items should be checked in this load case(stress/load/displacement)?
3-for stress checking in this case(if needed),what ratio is acceptable?

Hi,
'Operating - Thermal' will account for the incremental change in the sustained stress (or really, the longitudinal stress due to sustained loads) as the load from thermal strain is incrementally added to the system (that is, as the system heats up).

Check out this earlier post.