I wanted to bring this up just because it amazed me. I was called to the basement on a HP Shower pump 3600 RPM 50 HP motor with a vibration problem. I was showing high axial vibration on the motor, .48 in/sec at 1X and severe impacting in the Goulds Pump 30 Gs. I suggested changing out the pump because the bearings were bad. I received a called about 2:00 PM yesterday saying they were going to change out the pump but were not going to align it. Albeit it has an atraflex coupling but 3600 RPM? I said I would not do this. They done it anyway and the highest vibration I had after changing the pump was .08 in/sec. No Gs greater than .5 so I told them a job well done and went home. I ask you, what are the odds? I guess the only thing they had going for them is they did not move the motor and the pump was held in place by the bowl and piping. But I still don't understand it running so good without aligning it.

Thanks,
Ronnie

Dumb Luck? Even a blind squirrel finds a nut once in awhile.

On a serious note, they may be OK on this pump, but this strategy is going to bite them somewhere else.

My opinion is that absence of vibration does not prove absence of shaft misalignment and associated static forces:

http://maintenanceforums.com/eve/forums/a/tpc/f/3751089011/m/4571054772

Pete,
Good point. I just assumed this type coupling was absorbing the vibration. Which probably means they will be changing the insert more often.
Steve, I could not agree with you more. Luck only gets you so far and then the odds go against you. Besides, I am contracted in house so I can keep an eye on this one.

If you want to know what the alignment is you measure alignment and not vibration. Not performing alignment can lead to failures or worse.

A luxury boat owner once had me do analysis of the propellor shaft that had a viscoelastic coupling but still suffered from severe vibration. (Nobody told the owner of this boat with zebra-skin covered couches and golden faucets that you can not use a universal joint at a 17 degree angle) A few days later he called me at about midnight from his boat saying all of a sudden he no longer had vibrations or sound coming from the shaft. I told him to stay close to the coast and immediately call the Coast Guard as he would very soon be without any power as his coupling was probably tearing. He did exactly that and was lucky to be towed to safety.

I hope your customer don't call you in the middle of the night, like mine did.

Regards
Ibrahim

I agree with you William but in this case the customer did not want an alignment check, just a vibration check. I recommended aligning it but they did not seem to have time to do it right. I think they are fortunate that the vibration levels were as low as they were. But I rechecked it yesterday and the vibration has increased in the axial plane on the pump. I think you could be right, William. Not aligning it may lead to failure sooner than expected. I will keep a close eye on this one and try to talk them into aligning it during an upcoming outage on this paper machine in December. Thanks guys for your sharing your experience.

How is it that people can find the time to do something twice or more when they can't find time to do it right the first time?