To improve the reliability of grease-lubricated couplings, use only greases formulated for that purpose. General-purpose greases often have thickeners that are heavier than the oil. When subjected to the continuous and extreme forces of a spinning coupling, the thickeners in general-purpose greases can centrifuge to the outside, leaving the oil on the inside.

Unfortunately, the outside is where the oil is needed. Regarding the weight, the thickeners in coupling greases are equal in weight to or lighter than the oil, ensuring that the wearing parts in the coupling are well-lubricated. (Doug Branham, Lubrication Systems Company)

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Book Bits: Low Bidder Takes All?

From "The Practical Handbook of Machinery Lubrication"

Let's face it, lubricants, replacement filters, bearings, seals, oil analysis programs and other maintenance materials and services are purchased by North American purchasing departments on an annual quotation basis with a "low bidder take all" philosophy. This obscene practice often ignores whether lubricants, filters or replacement bearings are being specified correctly; even more importantly, it ignores whether the best products are being specified for the right reasons.

It's a sad fact that many purchasing and maintenance departments are still practicing this most blatant example of the false economy which much of North America's industrial and public sector management applies to equipment maintenance.

The very best maintenance products must be specified to ensure that premature failures are kept to a minimum and capital equipment has a chance to reach its expected life cycle. In addition, it will allow the organization the time and opportunity to establish sound and close working relationships with its suppliers.

More information about the book "The Practical Handbook of Machinery Lubrication"

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QUESTION: What are the main factors that promote chemical degradation of lubricants?

Get the answer.

"We are experiencing pump bearing housings that are contaminated with either water, sludge or wear metals. I've been reading about some in-depth flushing procedures on your Web site. Is there a simpler standard procedure that could be used (recognizing that all contaminants will not be removed) to remove some, if not a good portion of the contaminants?"

The chosen path will depend on the nature of the contaminants.

If your primary problem is an adherent contaminant (varnish), then forceful action or chemical action is likely required. You may remove some portion through normal oil changes, but this is a long-term proposition. High-velocity flush with a detergent or petroleum solvents may be useful, but as I understand, you are not in a position to go this route. There is always some risk to introducing solvents and detergents into lubricant compartments.

If your contaminant is in the bulk fluid (particulate or chemical contaminant) then a drain and fill, repeated a handful of times with short run periods between, may be sufficient. With some systems I would be comfortable conducting a running drain and literally flushing out the old material with a large quantity of new lubricant metered in while the system is running (also known as bleed and feed). You must pay special attention to oil levels if you choose this route.

It is not difficult to install fluid quick-connect couplings on most existing sumps, even with the machines running. Again, attention to the oil level is important. I would prefer to install fluid quick-connect fittings and use a filter cart well above the other alternatives. Even with heavily varnished surfaces, the right type of filtration equipment can resolve the problem.

Mike Johnson, Noria Corporation

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