Need help sealing my 775DC 30,000 rpm motor shaft

In summary, the seal for a pump with air and water in it that will be running for up to 5 minutes may need less leakage than a labyrinth seal. However, heat and vibration may be a problem.
  • #1
ausmar1218
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2
TL;DR Summary
30,000 rpm 775DC motor seal.
Hi,
I need help finding a way to seal my 775DC 30,000 rpm 5mm motor shaft going into my pump housing I built. This motor will run once a week for up to 5 minutes. The pump with have air and water in it. I will rarely ever be completely filled with water. So, the pump will mainly be pushing air with some water through it. I have used a dishwasher diverter seal which works, but gets way too hot due to the friction between the seal and shaft. The dishwasher diverted seal’s dimensions are 5.5x16x8mm. I am also playing with the idea of using grease like Bentone grease to try and seal the shaft from the water leaking out of the pump housing. Any suggestions and ideas are welcome! Thanks in advance!
Mark
 
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  • #2
Welcome, Mark!

Research or look up "pump labyrinth seal 5 mm".
 
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  • #3
Lnewqban said:
Welcome, Mark!

Research or look up "pump labyrinth seal 5 mm".
Great, thank you very much!
 
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  • #4
ausmar1218 said:
Great, thank you very much!
Have you used these seals?
 
  • #5
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  • #6
Baluncore said:
If less leakage than a labyrinth seal is required, consider a polished Ceramic flat face seal as used in water pumps. Small diameters will run continuously at 20,000 RPM.
https://www.aliexpress.com/item/1005005121659359.html
Great, thank you! Have you used these seals before with 20,000rpms?
 
  • #7
ausmar1218 said:
Great, thank you! Have you used these seals before with 20,000rpms?
Not that small. I have used much larger seals of the same type on water pumps, with similar contact surface speeds.

Clean water lubricates and helps seal the flat, polished surface contact.
The static, ceramic part of the seal is usually spring-loaded, while the rotating part is fixed to, and balanced on, the rotating shaft.
 
  • #8
ausmar1218 said:
Have you used these seals?
Yes, in centrifugal pumps, blowers and steam turbines, but not at those rpm's.

Vibration and heat may be a problem in your application.
Turbochargers for combustion engines spin very fast and need to be very carefully balanced.

I don't believe that grease will help in your case.
The above suggestion from @Baluncore is excellent.
 
  • #9
Baluncore said:
Not that small. I have used much larger seals of the same type on water pumps, with similar contact surface speeds.

Clean water lubricates and helps seal the flat, polished surface contact.
The static, ceramic part of the seal is usually spring-loaded, while the rotating part is fixed to, and balanced on, the rotating shaft.
Yes, I’m just worried with the high rpms and not having water in the pump chamber all the time even when the pump is running for up to 5 minutes that heat from friction will be a problem.
 
  • #10
Does your use require the motor to be actually submerged?

If not, a magnetic coupling is a possibility so the motor can be kept in the atmosphere.

Depending on the design details, note that a magnetic coupling may require a slow start of the motor to gradually bring the pump up to speed.

Cheers,
Tom
 
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  • #11
Tom.G said:
Does your use require the motor to be actually submerged?

If not, a magnetic coupling is a possibility so the motor can be kept in the atmosphere.

Depending on the design details, note that a magnetic coupling may require a slow start of the motor to gradually bring the pump up to speed.

Cheers,
Tom
Hi Tom,
Thank you very much for the input! No, my motor is not submerged. My motor doesn’t have a slow start and I’m not sure how the magnetic coupling would affect the torque or if something is clogging the impeller. I will look into it. Thank you very much!
 

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