Impeller rubbing against diffuser

[Steve Bennett]

I've got a 2HP Pac Fab Challenger. Pump stopped working yesterday. When I was troubleshooting it, it was making loud humming sound but not moving. Opened it up and discovered that the impeller is rubbing against the metal ring inside the diffuser. I replaced the diffuser, impeller and shaft seal two years ago and have had no problems with pump until yesterday. When diffuser and mounting plate are removed, the shaft spins easily in either direction. Put diffuser back on and impeller spins half rotation then rubs against diffuser and stops. In the pics you can see the grooves on the impeller.

Any ideas on likely cause for this? Damaged/warped impeller and/or bent motor shaft are my guesses. When I spin the impeller, I can't really see a wobble.

Is there a way to tell if the shaft is definitely bent, and if it is, do I have to get a new motor?

Thanks!

 

[mas985]

If the motor shaft was bent, you would probably see that. Are the rub marks on the impeller on one side only? Is that the same with the diffuser?

What caused you to replace all those parts in the first place?

 

[Steve Bennett]

Yes rub marks are only on one side. Diffuser doesn't really have any marks. It's got a metal ring on the inside of the opening. There's some scaling or corrosion on the metal but doesn't appear to have raised the surface at all. Can add a photo of that in morning.

I probably didn't need to replace those parts when I did. It was the first time I replaced shaft seal myself and the parts looked a little beat up so figured what the heck, might as well do it while pump is opened up. The diffuser I replaced had similar corrosion on the metal piece. I think that's partly what prompted me to put on a new one.

 

[JamesW]

Maybe a mounting plate that is not fully seated. Are all of the bolts secure?

 

[Steve Bennett]

mounting plate was seated and all three screws were secure. Nothing visibly that seemed out of order and there was no debris stuck in the impeller.

I added a pic of the current diffuser showing the corrosion on the metal ring that goes around the end of the impeller and also a stock pic of the same model diffuser showing the metal before any usage. Maybe the corrosion build up was enough to finally impede the impeller?

 

[mas985]

The fact that the impeller has scratches on only one side would imply that there is a wobble in the impeller. Could be due to bent shaft or the impeller itself.