Hi I have been requested to determine if we should sample oil from a bearing housing that contains 2 thrust bearings on a vertical mounted Pump. It contains only 8 litres in volume and lubricatnt is Shell tellus 46. To access the housing is difficult. My thoughts are not to sample but just replace the oil at a fixed frequency - based on run hrs. We conduct Vibe analysis on the bearings and they also have temp probes. Does anyone have a selection guide that incorporates the size / volume of housing etc? Thanks

Your vibe analysis should detect any bearing failure modes developing with enough lead time to act, but it may be worth doing your fixed frequency oil change and analyse a sample of the old oil for metal content. That combined with your vibe analysis may make you slightly less blind to what is going on indside. You would have to figure out if it was worth doing and this would depend upon the criticality of this machine.

Next oil change I would modify he upper reservoir fill or drain to allow you to get a sample when running. For a couple hundred $$$ you would be setup to do any analysis you need. I've had vertical pumps go 8 or more years between oil changes and that doesn't happen without the proper sampling hardware installed and good analysis trends. Oil analysis will show you degradation sooner than vibration on most vertical motor thrust bearings IMHO.

For the quantity as small as 8 litres, I would suggest going for the periodical oil replacement every 4000 hrs of operation or 6 monthly. However, keeping a PROACTIVE approach, I would be focussing on keeping contaminants out of my oil by using proper tools for lube handling, storage and dispensing (plus exclusion), like Oil Safe / I-Cans, using portable filtration carts for fresh oil top up, Descase descicant breathers, Esco Oil sight and level glass etc. Additionally keeping eye on the Vibration trend, and analyzing spectrum periodically might be the right strategy to follow.

Depending on the criticality of the operation, you may install proper sampling points and analyze the lube periodically to monitor the bearing / oil degradation.

Regards
Mohammad