Dear Techy06,
The forces acting on the nozzle shouldn't exceed the allowable in any condition, either hot or cold. The allowable values for API 610 pumps can be obtained from the code itself where as most of the other pumps you might have to contact the pump vendors to get the allowable.

In you're case I would suggest that you 1st check the forces on the nozzle in sustained condition. this is to make sure that you're initial supports are good enough to cater for the dead loads and there are no "see-saw" effects. if loads are OK, then you're piping routing maybe doesn't have enough flexibility and the hot portion of the system is effecting the cold portion of the system. so, you have to either re-route the system or try to isolate it by using restraints.

try attaching a picture of you're system in this thread. that'll make us beter understand you're predicament.

just my 2 cents.