In This Issue:

• Up Front: Low Viscosity Results Puzzling

• Book Bits: The Operator’s Job in Preventive Maintenance

• Today's Tip: Preventive Measures Make Sense

• Q & A: Filters Grab More Than Particles

Up Front

Low Viscosity Results Puzzling

We started receiving engine oil analysis results from our lab alerting us to a situation of low oil viscosity but with a negative test for fuel in the oil. After some investigation, it was determined that only the field service equipment exhibited this trait.

We took samples from the lube service truck bulk tanks to determine if a lighter grade oil, such as hydraulic, had been loaded into the engine oil tank. The samples came back showing significantly lower viscosity of the bulk engine oil.

We drained the oil from the tank and replaced it with fresh engine oil. The samples continued showing low-viscosity engine oil in the field service equipment. We tested the lube service truck again, and the bulk oil was again diluted.

Suspicious that a crack had developed between the hydraulic and engine oil bulk tanks on the service truck, we drained both tanks and refilled only the engine tank. After an hour, the engine oil transferred to the hydraulic tank and we had two half-full tanks!

Our latest specifications for lube service trucks call for completely isolated and modular tanks for each bulk fluid. (Submitted by Michael Houlden, Reliability Engineer, Finning. Thanks Michael!)

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Book Bits

The Operator’s Job in Preventive Maintenance

From "Fluid Power Maintenance and Troubleshooting".

Spell out just what the operator should do for proper equipment care, such as routine checks and records, or checking oil level and condition, removing excess dirt from the equipment, turning in equipment for oil changes and maintenance, and reporting any loose, damaged, or deteriorating parts. Keep operators conscious of the need for continuing inspection including: reporting worn or damaged tubing and hose, foaming or turbulence in the oil reservoir, signs of overheating, oil leaks, loose joints, worn seals, and any unusual noises that might mean cavitation, trapped air, or worn bearings and seals. Encourage the operator to note and report any slow down of machine operating time that might be an early warning of future problems.

More information about "Fluid Power Maintenance and Troubleshooting".

Today's Tip

• Catastrophic pump failure on circulating and hydraulic systems can damage more than just the pump. Consider using oil strainers or filters upstream of all equipment components to prevent pump failure debris from damaging these machines. This is also important for kidney-loop systems with expensive heaters and oil/water separators. (Submitted by Rodger Shaffer, Senior Manufacturing Engineer, Timken Latrobe Steel. Thanks Rodger!)

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Q & A

Filters Grab More Than Particles

"What are electrostatic separators? Are they different from regular filters?"

Electrostatic separators remove insoluble by-products of thermal and oxidative oil degradation (varnish particles) and submicron hard dirt or wear particles that are too small to be removed by conventional mechanical filters.

Submicron hard particles are usually polar, or attracted to other polar surfaces by nature. Varnish particles are usually polar as a result of the thermal or oxidative process that produced them. As a result, when a polar particle is passed through a high potential (high voltage, no current) electrostatic field, it is attracted to the negative or positive pole in the field, whichever is opposite the particle's charge. It is similar to a magnet being attracted to the opposite pole of another magnet.

There is evidence that these devices work quite well assuming the conditions for their use are good, the devices are sized properly (they operate on a low-flow multipass principle), no water is present (water compromises the electrostatic field by carrying current) and the oil doesn't contain detergents and dispersants that hold the contaminants in suspension.

When conditions are right, electrostatic separators make an excellent addition to an overall contamination control strategy, bringing into balance the focus upon large particles and water with the elimination of varnish particles and silt.

Drew Troyer, Noria Corporation

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