Pump motor shaft sheared off. Anyone seen this before?

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Jennifer_in_Clyde

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Apr 5, 2007
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San Francisco Bay Area
I'm trying to understand what caused this. The motor shaft on my Pentair Intelliflo VSF sheared off. Has anyone seen this before?

Motor housing.jpegImpeller with shaft.jpeg

The details: VSF pump installed in 2019. Everything was fine one day, the next day the pump stopped moving water. Pump would start normally, but after a few seconds would throw an alarm due to lack of water flow. Opened the pump to find the motor shaft had sheared off flush with the mechanical seal at the motor. The now-detached portion of the shaft remains firmly attached to the impeller and appears to have a slight bevel at the failure point.

The motor turns freely and did not make any unusual sounds while running. We never had major leaks, but based on the condition of the motor housing we apparently had some. The impeller was clean so there should not have been excessive drag. Could the seal have caused this?

If anyone has any thoughts, ideas conjecture, I would love to hear it.

Thanks-
 
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Okay wow. This must have been due to a variety of factors because the motor is not powerful enough to shear ~1/2 inch solid steel cylinder like that.
 
Thanks- I searched but did not find this issue in other threads.

Here is the seal plate. I thought it was unremarkable other than the amount of gunk on the dry side.
Motor Plate - Wet.jpegMotor Plate - Dry.jpeg

Can you explain "bell end"? (Sorry - pool amateur. This is my first pump disassembly) Is that the part of the motor that the seal plate attaches to, or the other end, below the fan (shown below)?
Fan end.jpeg

I'm happy to send additional photos and continue disassembly as I'm not going to break it any worse. The diffuser and impeller did not seem to have any unusual wear, and when assembled on the seal plate, the fractured shaft extends about a half-inch past the dry side of the seal plate.
 
Jennifer_in_Clyde said:
Thanks- I searched but did not find this issue in other threads.

Here is the seal plate. I thought it was unremarkable other than the amount of gunk on the dry side.
View attachment 551754View attachment 551755

Can you explain "bell end"? (Sorry - pool amateur. This is my first pump disassembly) Is that the part of the motor that the seal plate attaches to, or the other end, below the fan (shown below)?
View attachment 551756

I'm happy to send additional photos and continue disassembly as I'm not going to break it any worse. The diffuser and impeller did not seem to have any unusual wear, and when assembled on the seal plate, the fractured shaft extends about a half-inch past the dry side of the seal plate.
Click to expand...
The front end-bell is the part you see with the broken shaft. The other end-bell is behind the fan. The shaft seal has leaked for a long time and destroyed that pump.

You need, at the very least, a new sealplate, besides the motor. One of the brass inserts that holds the motor to the sealplate has pulled out, it is not a repairable item and the pump won't last long with only three bolts.. I've never seen one shear that cleanly, but you can see the extensive corrosion on the shaft from the leaking seal as well.

If the drive is still good, a new motor is available, along with a sealplate, PS-1000 seal (or the better PS-3865R Viton seal), a new body gasket.

Motors are in the $600.00 range. Val-Pak makes an excellent aftermarket sealplate for about $90.00. Seal and gaskets about $25.00.

The screw that is holding the impeller on to that broken part of the shaft is loosened/removed by turning to the right, it is a left-hand thread screw and must be replaced when a new motor is installed or the new motor will be damaged very quickly. There is also a small rubber cup that is in the hole where the screw sits. It, too, must be reused or replaced.
 
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Thanks- I knew the motor was trash, but I didn't catch the failing corner of the seal plate. I believe the drive and the wet end are both fine, so I am inclined to just replace the failing parts. I will probably have a pool pro do the work as I understand Pentair limits the warranty on replacement motors if installed by homeowners.

Here are some additional photos.

The black thing around the shaft is a piece of rubber that slid right off. In the last picture, the right side was closest to the motor housing.
Rubber seal 1 (1).jpegRubber seal 2.jpegRubber seal 3.jpegRubber seal 4.jpeg
Here is the broken end of the shaft without the black rubber piece. It looks like there was a step-down machined into the shaft (the shaft gets narrower) at the approximate point of failure.
Motor without rubber.jpegShaft shear point.jpeg
Here is the back side of the end bell. There was a little corrosion in the bottom of the motor housing, but not much. The motor bearings seem ok. I could not remove the end bell from the shaft because I do not have snap ring pliers available.
End Bell 2 (2).jpegEnd Bell removed.jpeg

Thanks again for your thoughts and assistance. Much appreciated!
 

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I have only seen the shaft shear off like that once or maybe twice.

There is a thread within the last year, but I cannot find it.

I think that I would replace the whole pump.
 
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The IntelliFlo motor comes from Lafert S.p.A in Italy.

S.p.A. means “Società per azioni” and it is a form of corporation in Italy, meaning "company with shares", “Joint stock company” or “Public Limited Companies by Shares.

Maybe contact Lafert to see what they say.

Electric motors - Lafert Group - Electric motor

Lafert Group s.p.a. designs and manufactures electric motors in AC and DC power for all types of applications: industrial, servo, automotive, etc ...
www.lafert.com www.lafert.com

Lafert North America | Contact

www.lafertna.com www.lafertna.com

1706402058958.png
 
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Impeller with shaft (1).jpeg


pump shaft.jpg


Pentair VCF Pump does not turn impeller, then trips on "Priming Dry" (B70022)

Help!! My pump is not running. What should I try next? I noticed that my pump was not running, and upon investigation, the pump shows the alarm "Priming Dry" (B70022). The pump is full of water. I am not sure what measurement makes it believe it is dry. [With the breaker shut off] I can...
www.troublefreepool.com www.troublefreepool.com


JoelsPoolHouston said:
Sure enough, the shaft was broken.....it is crazy how cleanly the break happened, the two ends almost look like machined surfaces. Replaced under warranty!
Click to expand...
 
David- Wow that is super clean. Is that new out of the box?

James- Excellent find. I should have searched the "priming dry" alarm code. Everything in that thread sounds familiar except the part about the pump being under warranty.

I appreciate the advice and I may well just replace the whole pump. When I woke up this morning I thought the impeller had broken off the shaft and that I would be fixing this myself with ~$100 in parts and a couple hours of work. I will need to warm up to the idea of replacing the whole thing.

Thanks all-
 
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Jennifer_in_Clyde said:
David- Wow that is super clean. Is that new out of the box?

James- Excellent find. I should have searched the "priming dry" alarm code. Everything in that thread sounds familiar except the part about the pump being under warranty.

I appreciate the advice and I may well just replace the whole pump. When I woke up this morning I thought the impeller had broken off the shaft and that I would be fixing this myself with ~$100 in parts and a couple hours of work. I will need to warm up to the idea of replacing the whole thing.

Thanks all-
Click to expand...
Haha thank you! This photo was taken during a shaft seal and impeller replacement of my Intelliflo pump a few weeks ago. It is a 15 month old pump, runs 24 hours. I caught the shaft seal leak early so no damage was done to the motor itself!
Here is the thread if you’re interested.
 
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Hello all- Thanks again for your thoughts and assistance. A brief update: I contacted Pentair's warranty support. They told me they did not know why the pump failed this way but because the pump is out of warranty they will not do anything for me.

I know many of you have had great success with Pentair products. That has not been my experience. Looks like I am shopping for a new Jandy pump...
 
I work with steel all day every day and this was a defective piece of steel from the get go. I zoomed in on one of the pictures where you clearly see a clean and dirty portion of the break. The outer circumference is a lighter shade whereas the center is darkened which means the last part of the broken shaft was just the outer part because that's the new break. The dark area was fractured long ago somehow most likely in the manufacturing process that is why it's darkened. This motor doesn't nearly have any kind of torque to cause this. The link @JamesW sent you may be very interested to get this into their hands .......
 

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