We have this Hot Oil line (Temp = 410 C) which has a support that strangely lifted. We already checked all possible reasons for this support to lift but we cant find the real reason. Hopefully some of you have encountered this kind of pipe behavior.

1. Support is not lifting in our calculation.
2. No thermal bowing since this is hot line
3. As per process engr, line is not subjected to AIV, FIV, Surge, Slug.

Nice. maybe some welds on the supports....

Looks like your supports in your model do not match the field, or your model is buckling, or both. CAESAR does not have any basis with which to gauge a pipe's tendency to buckle.

Rule out the former by adding artificial forces, moments, and restraints until you get something that approximates the shape. Eliminate the forces and restraints with field verification until you find the problem.

Rule out the latter by calculating the length of the deflected shape versus the length of the pipe with thermal growth.

I would want to know more about those two horizontal lines to the right. Perhaps they are creating a couple and this bending moment is driving your line up. Chances are, the elbow flexibility (the right end of your lifting line) is overly high - due to insufficient straight run into the tee below. Try a square corner here and see what happens.
Is this a new line? If so, perhaps it will be resting later in life - after shakedown.
Another diagnostic - turn your +Y in the middle of the line to a full Y and see what load magnitude is required to hold it down. It may not be that big. (Again, this support change is not to eliminate the condition but to better-understand what's going on here.)

As danb noted, it appears to be CONSTRAINED BOWING/BULKING. The pipe run is not being allowed to expand at this high temperature of 410 C/ 770 F.

WHoa! we'll check this on the site. I'll share my findings