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. 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.

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Unfortunately, many organizations approach lubrication excellence like a program, similar to a capital project, with a defined beginning, middle and end. In other words, it is something that must be defined by a clear return on investment within a predetermined time period.

Lubrication excellence is not about one single activity or collection of activities over a specific time period, but rather a continual journey which should be aimed at changing the lifestyle of the plant. Lubrication excellence involves changing the process of lubrication, not just purchasing tangible products or services.

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"I've been told that surface tension plays a role in the performance of lubricating oils and hydraulic fluids. What is surface tension and what effect does it have?"

Surface tension relates to the skin-like film that a liquid develops at its surface. The fluid's resistance in allowing an object to rupture this skin is its surface tension. For instance, water has sufficient surface tension to permit a sewing needle to rest on its surface without sinking.

A new lubricating oil has relatively high surface tension, say 35 dynes/cm. However, as the oil ages and becomes contaminated, its surface tension will fall to 20 dynes/cm or lower. Researchers have found that this can have a dramatic effect on the lubricant's properties. Negative effects include: foaming problems, air release problems, demulsibility problems, loss of antirust performance, and increased leakage.

Oxidation and water contamination are perhaps the most common causes of loss of surface tension. Other contaminants that decrease surface tension include detergents, grease, floor soaps, some solvents, and retrofit additives. A standard tensiometer can be used to quickly measure the surface tension of most lubricants.

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