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We have machines that cut slits in plastic pipe. The pipe is usually wet, and the lower spindles of the machine get wet. Originally the machine was made to use greaseable bearings (as evidenced by the grease nipples) but they have been replaced by sealed bearings because of the mortality rate from the water.
I'm looking for opinions whether the sealed bearings will last longer than a greaseable open bearing with a water-resistant grease.

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Sealed bearings have a great advantage of eliminating the trouble of relubricating, and doing a great job at keeping out contaminants.

The drawback (if it is one), is that you cannot relubricate the bearing. When the grease reaches its end of life, you will get bearing damage and have to replace the bearing. How long is that? SKF says a sealed bearing should last approx twice the relub interval, so you can figure at least that long (since SKF's recommendations are notoriously conservative IMO).

And of course the relub interval is given in many different forms, but generally depends on machine speed, bearing size, duty, perhaps ambient temperature and load etc.

So its' not such a big drawback if you have a bearings where the calculated relub interval will be long (maybe 3 years... expect 6+ year life of sealed bearings). For example small bearings ith relatively low D*N number particularly if the machine does not run 24-7. This makes sealed bearings ideal for many applications in household appliances.

For me, our outdoor crane motors (relatively small bearings with very limited run-times) are no-brainers for sealed bearings. Heinz Bloch recommends sealed bearings below 80,0000 D*N and possibly up to 108,000.

If you tell us the bearing size, machine speed, and run-time duty cycle, I'll give you my guess.. but just using the logic I expressed above.
RM
Last edited by Registered Member
quote:
Originally posted by JM Reliability Engineer:
I previously worked for a company that manufactured this type of equipment, but they are no longer in business. I will try to contact one of my former co-workers who works for another company that makes perforators to see what they are using.


Wow. I kept it vague because I didn't expect that anyone else here would have experience with perforators. I should have known better. Ours are old-school ones with those irritating wheels and knives, made by Valley Gear in Bent Drainpipe, Missouri or some such place. Hang on, I'll Google it. Oh, 'Bad Axe, Michigan'. That's it.
RM
Hello,

Our motor rebuild shop was sending us sealed bearings on all our rebuilds. But we were having vibration issues with some of our rebuilt motors. We specified an abech 3 (tighter tolerance) bearing non shielded and have gotten better performance. We were getting cheap shielded bearings in our rebuilds. The motors are 60 hp,1750 rpm. 3 phase running 125 hours a week on average in a wet enviorment.
RM
quote:
Originally posted by Don Jones:
Any chance that seals on the bearing housings could be used on this application.

That's a good question. There isn't 'room' for them right now, but if the housings were bored a little deeper I might be able to fit one in in each end. The bearings would be closer together, though, and these spindles are run off of angled shafts (with U-joints on each end of the shaft) so we have issues with the bearings taking a heavy radial load already, and moving the bearings together would add to the problem. I'd probably worry about having to replace seals a lot, too, and wear on the spindle shafts.
Still, it's something to consider.
RM
Metalworker Mike,

have you considered INPRO/SEAL Bearing Isolators ? These are labyrinth seals which keep in grease and keep out water and contaminants. I believe they can be retrofitted in most standard TEFC motor end bells. We had good experience with fitting them inboard of the drive end bearing of large 800 Hp / 300 rpm vertical pump motors. These motors have Open Drip-proof enclosures, and because they are installed outdoors, rain water found its way down the rotor shaft into the lower DE bearing causing housing corrosion and grease deterioration. The INPRO/SEALS mitigated the water ingress issue. Here is the URL
http://www.inpro-seal.com/
RM

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