Thread + torque + high temp + creep = seize?

[USAeng]

Just wondering if you have threads that are in a continuous service temperature of 1500-2000F environment that are either made of 1144 steel or 304 stainless with 1 1/4-12 threads with an applied torque of about 50-60ftlbs if after time the threads of both materials will deform/creep from the axial load created from the torque

We are having trouble with threads seizing in the field under those temperatures. I am wondering how threads will handle temps like these... what are your experiences?

I also am looking for some way to calculate the stress in ksi in the pieces made by applying the torque... can someone help me?

The pieces are actually the outside of a tube threaded with the 1 1/4-12 threads (class 1) and the inside of a cap nut that screws on top also class 1 threads...

Thanks a lot for any advice...

 

[USAeng]

oh and the torque is applied during assembly... not continuous