HOT SUSTAINED STRESSES

WHETHER IT IS ACTUALLY REQUIRED TO CHECK THE HOT SUSTAINED STRESSES IN PIPING SYSTEMS.IT IS VERY COMMON THAT PIPE SUPPORT LIFTS UP IN CERTAIN CASES BY SAY FRACTION OF MM TO SEVERAL MM.SUCH CASE IF IT IS REQUIRED TO GO FOR HOT SUSTAINED CHECKS (LOAD AS WELL AS SYSTEM STRESS) WE MAY END UP IN REPLACING REGID SUPPORT HAVING SMALL LIFTUP ALSO WITH SPRING.IS THIS IS ACTUALLY REQUIRED THIS MUCH CONSERVATIVE APPROACH? OR WE CAN USE
SELF LIMITING NATURE OF OPERATING STRESS WHICH MAY CHANGE TO NON ACTING SUPPORT TO ACTING SUPPORT AFTER SOME PERIOD OF OPERATION? IF SO HOW TO ARRIVE AT ACTUAL ALLOWED LIFT? WHICH WILLNOT DEFEAT STRESS.PLEASE THROW SOME LIGHT

This topic is discussed in detail in the CAESAR II Technical Reference Manual, see page 6-19.

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Regards,
Richard Ay (COADE, Inc.)

This is non-linear system. C2 manual explains this case as Mr.Rich say.

Another way is to take out the supports which are lift-off in your model. And you check the sustained stress and deflection. When the sustained stresses are whithin allowable limit, it is O.K, that is, leave the lift-off support in your system because those resting supports will be helpful for hydro-test or the other abnormal condition. When overstressed, you add springs in the lift-off point.
This is very simple and common way to check lift-off case's stress.

[This message has been edited by Soon Ryang, WEE (edited February 27, 2001).]

See my article in the last COADE MEN newsletter it is available online.

Best Regards,

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Best Regards,

John C. Luf