Rotary Shaft Seals

realitybias

I am using the motor from Jameco... http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=174692&pa=174692PS

in a centrifugal pump. Our biggest problem has been sealing the mechanical shaft. I can't use an O-ring, because they are not efficient enough and grind down rather quickly. I have heard about rotary shaft seals and lip seals, but they do not seem to be suited for such a small shaft diameter (.08 inches). If any of you could please help me with comming up with a good solution for this, I would be very grateful.

Thank you.

stamptrol

The normal seal for your application is either a double lip rubber/neoprene/butyl seal or a ceramic face mechanical seal.

However, there are two problems to overcome: You're working with very small sizes, shaft-wise and, secondly, the seals will use up a large part of the power the motor can generate.

There are two common solutions: buy a motor/pump combination that has the seal built-in ( small bilge pump, laboratory pump, garden fountain pump, windshield washer pump,etc) or, do away with the need for a seal by coupling the motor to the pump with a magnetic coupling or by extending the motor shaft so its above the liquid level.

Cheers

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Tom Sisk

http://www.siskconsult.com
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realitybias

You are very knowledgeable about pumps, it seems. Thank you so much for your answer. It may help, depending on what I can find. Can you recommend any sites that sell pumps with built in seals, as you suggested? We took apart a winshield washer pump, and that is EXACTLY what we need... but we still need students to be able to build the impeller and pump housing themselves, so all we need is the motor. If you can forward me to a good supplier, I would be thankful.

stamptrol

Reality,

If you're committed to the motor-with-seal direction, have a look at http://www.balseal.com/products/rotary.php. They have seals down to the size you will need.

You didn't say what the application was, but to get students to learn about centrifugal pumps, the long-shaft design noted above will let them design the pump without getting bogged down in finding a suitable seal.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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John R.

In the past I've used a "Quad Ring" for a small shaft seal. They are not as efficient as a "lip seal" but do better than an o-ring, both in terms of friction and longevity. They are made by Minnesota Rubber www.quadion.com/ and sold by Small Parts, Inc. www.smallparts.com/products/descriptions/81q.cfm among others.

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John R.
Click here to see my Nomad Build Log