Book Bits
From "Filtration Technology":

Water absorption filters usually have an element that combines a particle removal media with water absorption material. The water absorption material may be something as simple as cornstarch, or as complex as a polyacrylate material. The latter is the type of material used in babies' diapers to absorb water. Typically, these filters are used to remove small amounts (less than 1% by volume) of free water from hydrocarbon fluids in circulating systems.

Most water absorption media are sensitive to flow rate, and their efficiency improves as flow velocity is lowered. It is common for these filters to be used on off-line circuits where the flow rate can be controlled by pump selection.

Today's Tip
Monitor your filter change interval. Premature plugging is usually a sign of a problem that merits further investigation. This may be caused by airborne dust coming from nearby construction or a prolonged dry spell raising atmospheric dust levels. Whatever the source of dirt, the root cause needs to be investigated and perhaps the seals or breathers need to be serviced or upgraded accordingly. In certain cases the problem may be associated with a change in the performance of the filter from your supplier. Extremely long filter life is as much a concern as too short.

Q & A
"To what extent does the presence of microbial growth affect the quality of lube oil, and how can this be controlled?" -- Nomava Marala, Arnot Power Station

Microbial contamination is a pro-oxidant and forms acid products in the oil. Additives are also adversely affected. Over time insoluble suspensions can lead to sludge, deposits, and viscosity change.

Filters will plug and oilways will obliterate. Usually the best strategy for controlling micro-organisms is to control water contamination. Without water the bacteria can't survive. For water-based lubricants there are biocides available as well.

Jim Fitch, Noria Corporation

Book Bits
From "The Lubrication Engineers Manual":

Consumption Reports

Some companies monitor gal of oil lost per operating hr to more closely gauge their loss reduction efforts. Where this method is used, changes in productivity will not distort loss- reduction efforts. A higher than normal consumption on a monthly report usually generates the maintenance action required to maintain the loss within reasonable limits.

Today's Tip
To ensure that the proper lubricant is used in a bearing, use a thin colored washer at the fitting and paint the grease gun the same color as the washer. To install the washer, unscrew the grease fitting - find a washer with an inner diameter a little larger than the outer diameter of the threaded shaft of the fitting. Insert the fitting into the washer and screw in the washer/fitting assembly. (Tip submitted by Don Carrell, Fiske Brothers Refining Co. Thanks Don!)

Q & A
"What is the best material to use when flushing out a large circulating system prior to a new fill?" -- Rodger Shaffer

The ideal answer is to use the same type of product that you will use as a final lubricant. Short of that, the next choice would be a lighter viscosity product of the same brand name category. If neither option is viable then contact the manufacturer of the product for direction on the use of a flushing oil that is compatible with the final product choice.

It is important to test the lubricant after the final fill is completed and the oil has circulated thoroughly (seven times through the pump for a circulation system) to confirm that the viscosity is in the correct range. Viscosities can be adjusted by blending heavier components to bring up a low viscosity or vice-versa.

Mike Johnson, Noria Senior Technical Consultant

Book Bits
From "Proactive Maintenance for Mechanical Systems" by Dr. E.C. Fitch:

A slight discoloration of the oil is nearly always present during the initial stages of oxidation. This discoloration increases as the process continues and the decoloration is accompanied by a drop in interfacial surface tension and a rise in viscosity, specific gravity and the neutralization number. The rise in viscosity and acidity are not necessarily inter- dependent.

Primary oxidation will cause a rise in acidity which will ultimately level off, at which point the viscosity may rise at an extremely rapid rate. Such increases in viscosity rate usually occur due to the generation of oxidation products of high molecular weight, held in fluid suspension. Paraffinic base oils are less apt to produce sludge at an earlier stage as those of a polynaphthenic base.

Today's Tip
Excessive bearing vibration can have the same effect as irregular regreasing of bearing contact surfaces. It typically causes the grease to be broken down into the oil and the thickener, that is, the oil separates from the thickener.

It is good practice to select greases which are suitable for vibratory conditions (your local lubricant supplier can advise you of suitable products) and to lubricate the bearings at short intervals--perhaps as frequently as weekly depending on bearing size, speed and operating conditions.

Q & A
"We are experiencing sleeve bearing failures on a piece of equipment. The main cause of failure is bearing wear due to mechanical misapplication of the equipment. We are not in a position to change the bearing type yet because we have to meet current production demands. Would a simple magnetic plug help to remove 'free' particles of entrained bearing material and slow down the rate of wear until we can correct the root cause?" -- Jim Morcom

Unfortunately, magnetic plugs trap only large ferromagnetic wear debris (typically larger than 100 microns). Nonferrous particles associated with babbitt used in sleeve bearings would not be removed, nor would ferrous particles (shaft metal for instance) smaller than 100 microns.

Therefore, wear metal is unlikely to be trapped by a magnetic plug. I would suggest the following:

Fitting a couple of quick connects to the bearing housing top and bottom would allow a small portable filtering unit to clean up the oil very rapidly. On the assumption that you would need to turn over the volume seven times, then a 5L/min pump would take less than 10 minutes to clean up the oil to a very clean level. In conjunction with the new breather unit, this would minimize the main cause of wear.

Upgrade the breather/vent units if these are fitted. Bear in mind that a 10 micron particle entering through a vent plug is like a snooker/pool ball rolling through a doorway (there is little chance of stopping it.) A good breather will help ensure that no additional contamination is entering.

If the machine is being stressed, oil temperatures are probably higher. The OEM specified oil may be too thin at the higher temperatures. Consider a change of lubricant viscosity specification, perhaps even to a multigrade or synthetic.

Martin Williamson, Noria Senior Technical Consultant