Stud bolt of impeller

[Hesam267]

Hi guys
I have a question about stud bolt of high speed impeller rotor.
Actually we have high speed compressor (about 40000rpm) in our plant. After some year we change impeller due high erosion, with new one.
We know amount of impeller torque of stud and because of high defection, it's tight and uptight many time (about 3 or 4 time). Is this stud bolt design just for one time use or we had to replace it each time with change of impeller?
Thanks

 

[JJPellin]

The torque should not have exceeded 50 percent of yield for this stud. I see no need to replace it.

Johnny Pellin

 

[Hesam267]

Thank you Johnny for your reply.
please apologize me. Actually first we use special tool for tension stud according document value then tight nut normally. so we dont know any thing about elastic or plastic elongation.
is it necessary to change stud in this state or not?
thanks again

 

[JJPellin]

What size is the stud? What lubricant was used? What torque was applied? You can estimate the stress applied. No tightening procedure should exceed yield. No. You do not need to replace the stud.

Johnny Pellin

 

[Hesam267]

dear Johnny
if I'm not mistaken, stud is M16 and pressure of jack is 375 bar.

 

[JJPellin]

Take the "jack" pressure and calculate the force applied to the stud. Take the force and the cross-sectional area of the stud to estimate the stress in the stud. Compare that stress to the yield strength of the stud. You have not provided enough information for me to do those calculations. And, I wouldn't do it anyway. Do the work yourself.

Johnny Pellin

 

[Michael-Lu]

You can estimate the pressure applied. The tightening step must not exceed the throughput. Do not. You do not need to replace the studs.

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