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Bearing Submerged in Water

Bearing Submerged in Water

Bearing Submerged in Water

(OP)
Dear all,

I am looking for some advice on using bearings submerged in water.

We are currently working on a submerged (slurry) pump that pumps water with plastic beads. Pump construction is very simple and schematics is shown below. Motor is 1500 RPM, 4kW, Shaft Dia is rouhly 22mm (1 inch). Pump pressure 2bar

Pump impeller is directly connected to prolonged motor shaft (all static and dynamic forces are taken by heavy duty motor bearing) There is no additional guiding of shaft. We however decided to prologue the shaft and prologue pumps reach. I am looking for some simple way to hold opposite end of shaft in radial direction. Since the pump volute is directly connected to motor I thought about fixing the shaft in volute casting with help of a bearing. The problem here is that as I mentioned before the pump is submerged in water (not clean by any means). Does anyone have any advice on what might work? I considered bronze or plastic sliding bearing but I dont know how they behave in water. Has anyone skilled in pump design ever encountered such problem and has any suggestions on some simple solution to my problem? (There is no way we can incorporate proper sealed bearing solution)

Thank you
Jack




RE: Bearing Submerged in Water

JacobGog-

This might work. Need to check your shaft radial load and shaft angular/radial displacements vs the bearing's capabilities. Also looks like you will need to allow for a continuous flow of water thru the bearing to provide cooling and flush debris.
http://www.duramaxmarine.com/bearingLine.htm

RE: Bearing Submerged in Water

The Duramax / Cutlass bearings are a good suggestion, provided that no abrasive particles are present. If there are any abrasives, they can get embedded into the rubber liner and grind away the shaft surface. Fancy hardening processes will help, but abrasives have a tendency to not care.

There are other plain bearing options, even sintered diamond technologies that will run in anything for practically forever. Depends on your budget, radial load, PV, process abrasives, and life expectations. You probably only need the bearing to last as long as the impeller.

RE: Bearing Submerged in Water

I have made a modification like this to a pump with good success. My pump looks much different than your, but the issues are the same. Our pump is a two stage, overhung, horizontal design running in concentrated caustic solution. We extended the impeller nut to serve as a stub shaft on the opposite end and added a tail bushing which runs in the pumped product. Any support there is better than nothing. We made our bushing from Graphalloy and our stub shaft from 4140 carbon steel. We modified the casing and added a separate housing to hold the new tail busing. The reliability of the pump improved drastically. It now runs for 3 or 4 years between failures. Before it was failing every few months.

For your application, I think Graphalloy would work well. Vespel might be better, at much higher cost. Carbon graphite or even solid Teflon would work. As I said before, anything is better than nothing.

Johnny Pellin

RE: Bearing Submerged in Water

OP apparently got all the info he needed on or about Dec 4.

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