in rotating mc nozzle alignment, cold pull or plastic deform

In rotating mc nozzle alignment, cold pull or plastic deformation - which is prefarable ?

Say, we have 20 mm lateral misalignment at turbine inlet nozzle - can we just pull and join the flange and take the cold pull in analysis. It is desirable for pipe stress viewpoint.

If we bow pipe by heating one side and deform laterally in plastic deflection or pull and bend the pipe in plastic deformation, will it be a desirable practice! How to know its impact on equipment reliability ?

reg,
sam

Hello,

20mm will impose a big load in the turbine nozzle if it will be forced to be aligned depending on pipe size and thickness. Nozzle Load might be excessive. What I can suggest is to add some green length in the three planes of pipe and put field fit weld so that this type of misalignment can be avoided and field adjustment can be done. Maybe the final welding can be done after the equipment has been installed.

Glad to hear some more opinion of other stressers who have experience this type of situation in the field and what has been done.

Cheers!!

Many young entusiasts do not understand what is really the cold pull!

After you have alignment with springs locked, if you unlock the springs and then try to achive alignment by cutting pipe in any direction, you are adding cold pull in the piping to achive rotating m/c flange alignment with springs unlocked.

Any adjustment in field weld before spring unlocking can be allowed, as it i is not cold pull; not after!

reg,
sam

Hello Sam,

Thanks for that enlightenment.

Regards,

Hello all!!

If the nozzle and piping is aligned properly before unlocking the spring then after releasing the lock of the spring, it can be simulated in the analysis where the spring is active and the pipe is empty (where some extra force will be induced in case the fluid is liquid) then comparing the nozzle loads to the equipment allowables.

Any other opinion is greatly appreciated.

Regards,