Normally that section of the line is a long flat section. The line is very difficult to control. Hysteresis of the hangers, poor selection, poor drainage etc result in this sagging. Our approach is normally to do level surveys, hanger readings, engineers walk throughs, NDT, replication, rerun stress analysis, take some of the hangers for testing and evaluate. Normal solutions include total realignment of the line, rotation of the pipes, replaement of hangers, recalibration of hangers, addition of drains, stabilization of the system by adding rigids and variable springs. Control hangers have been tried also. Expensive and requires maintenance. With a quick thinking I cannot remember a case where we would have added hangers.

These P22 thick lines are much more difficult to get right than X20 (of that time). Your hangers are most probably high hysteresis type. Possibly in wrong setting in addition. Do you know the actual wall thicknesses? I doubt.

My bet is:
- you have some creep damage
- your drainage is poor to non existing
- hanger hysteresis is over 10% (New should have 2% used 4% or better)
- some of the hangers may have failed if no maintenance has been done, broken springs, seased bearings, broken straps, relaxed springs, rusty sliding surfaces, ash etc on cams...
- stress calc says that long flat section should move down and up (which it doesn't do)
- you pipes are deformed
- if hangers were added then loads may be out. Just check if ancillary masses were added. In situ adjustment without load cells doesn't work.

You do not do random metallurgical evaluation. Locations are selected very carefully or you have to have plenty time and money.

If your system has no rigid hanger between the boiler and the turbine then as far as I am concerned the system is wrongly designed and will never work.

We have done this type of work some 25 years. Orders accepted.