Possible pump motor bearing failure?

[kballard72]

Start up pump all is well 19 pounds PSI

20 minutes later drops to 5 and impeller gets really loud.

The thing of note since it runs 20 minutes it does not sound like a leak. My suspicion is perhaps the shaft of the impeller is loose or something or heat related causing a slowdown... Perhaps the bearings themselves but it is not really a bearing sound.

Interestingly prime is never lost no air bubbles, etc...

Dumfounded. Nothing is in the impeller but did not know at the time how to keep the shaft from moving to check its movement.

It is a hayward tristar and I noticed the white impeller ring (looks like a white bearing race) has numerous etchings as well as the neck of the impeller that it slides over....)

Its like the impeller is losing speed to maintain 20 but not its suction to maintain prime...

Go easy, this is just what I am seeing.

[PoolDoc]

Sorry for the delay in replying; I'm not sure why, but we've been hammered with traffic over the last 2 weeks and to put it simply, we cannot keep up.

It does sound like you have a bearing failure in the motor -- they are what would determine shaft alignment and movement. But I don't know how to tell you to check for that. I'll see if Mark (mas985) has any ideas.

[mas985]

Is the noise more of a screech or rattle/vibration?

Does the motor shut down when this happens (i.e. trips the thermal overload)?

If not, then the motor is probably not binding and it may be just the brass nut in the impeller has come loose/broken so it is slipping on the shaft of the motor. This would cause wobble and tear up the impeller ring plus make a lot of noise. When you turn the impeller, the motor shaft should turn too.

If the motor is shutting down, then it probably is a bearing although other things can bind the motor shaft including the impeller and/or impeller ring.

[kballard72]

replaced impeller, shaft seal, and the white wear ring that goes between the impeller and diffuser. let it all run before putting strainer half back on to make sure no odd noises in the reassembly. All good....
Put all back together... kicked on the hi speed and all was good for about 15 minutes as usual.. then the pressure drops from 18-20 down to 5 and a boatload of racket again. Not really a bearing sound though more like a clatter.

Observation #2, if I cut the valve half closed on the return side to force the pressure to build back up the racket stops. I think the racket is just cavitation do to whatever is causing the pump to not be able to maintain pressure.

Just bizarre, prime side stays full... pressure side drops... due to the time is still sounds like a heat thing with the motor, perhaps not bearings, maybe the motor itself is just doing something odd... it is a two speed emerson/hayward tristar. The motor was replaced once for previous bearing issues, which was a much different noise.

Are they clutched or anything where it would run on high but something slows the shaft... just stabbing in the dark...

[mas985]

There is a centrifugal switch in the back and if that is not operating properly, it could cause some issues so you might want to inspect that.

Are there any problems operating at low speed?

[kballard72]

Low speed seems to operate at as much pressure as high after it freaks out. So after high takes its split second nose dive from 19 to around 4 or 5... I simply kick it to low... the noise stops (which seems to come from the impeller area) and low speed is quiet like it should be. Once it is done running for the day I will let it sit... High seems fin on a cold start...

Kick it on and video what it is doing... a picture is worth a thousand words but youtube is priceless.....

[kballard72]

http://youtu.be/6zskny8Osfo

So at the beginning is normal pressure, never loses prime. I can close the return valve which will force pressure to go back up, but once the motor gets in this state it continues to run visibly rough.

At this point the motor seal, impeller and wear ring have been replaced... no change I suspect something internal to the motor itself.

[PoolDoc]

I don't know -- sound quality in the video is not good, and is very hard to listen to, but if the blue tubing in the screen cap below is passing air into the volute (chamber behind the pump strainer pot chamber) you'd get just that sort of effect. And, it's very, very common for tubing connected to pumps via the drain ports to cause that sort of problem:

[kballard72]

That tubes job has been to pass air, its from the ozone generator and has passed some "air" since install 3 years ago.. But it is turned off while chasing this problem

And for the unit to run fine for the first 15-20 minutes repeatedly seems improbable to be related to the basket (suction) side. But that 15-20 minutes does have to occur after overnight cold.

[mas985]

It doesn't mater if the ozone line is off, you need to remove the line and put back the drain plug otherwise, you can't eliminate that as the cause. It definitely sounds like air is getting into the pump and if it is injected at the bottom, you may not see it in the pump basket.