We received a new 55-gallon drum of oil for some large gearboxes. These gearboxes cost about $50,000 each. A week after this oil was received, a gearbox was replaced due to some vibration readings I had taken with my analyzer. When the new box was filled with oil, the technician thought it would be better to open the new drum of oil and use it instead of the drum that was nearly empty. He failed to mention this to anyone.

I had not verified that the oil in the new drum was what it said on the label. It turns out the viscosity of the new oil was not correct and the new gearbox failed within two weeks. Valuable lesson learned here. (Lane McGuffin, Predictive Maintenance Technician, Cryovac)

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Book Bits: How to Keep Contamination Out of Motor Bearings

From the book "Industry Practices for Electric Motor Bearing Lubrication"

Particle contamination can drastically shorten bearing life. There are a number of practices available to control contamination from getting into the bearings. During this survey, when asked to give all the types of measures used, the top two methods were (1) to leave a small amount of grease on the fitting and wipe away later and (2) use of a plastic grease cap.

Many said that no practices were applied to control contamination. Those who selected "other" had similar responses: The grease fitting and grease gun are wiped before regreasing. However, these options do not keep contamination from getting to the bearing from other entry points.

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"What are the possible sources of silicon in oil?"

Silicon is measured by oil analysis labs to determine dirt ingression. More often than not, high silicon readings indicate dirt; however, there are several other possible sources. The four most common are:

1. Defoamant additive - Many oils contain defoamants based on polymeric methyl silicone. Because silicone contains the element silicon, the presence of this kind of additive will show a positive silicon reading in spectrometric analysis. The typical levels of Si seen under these conditions are around 1 to 10 ppm.

2. Silicone-based sealant - Many sealants used for industrial and mobile applications are silicone-based. The level of silicon observed will of course be directly related to the amount of sealant leaching into the lube system.

3. Casting sand - Some components are made by casting in sand (silicon oxide). Although new components are cleaned thoroughly prior to installation, it is not uncommon to see 50 to 100 ppm of silicon from new equipment. This level should drop as the component breaks-in and regular oil changes take place.

4. Coolant contamination - Many engine coolants contain inhibitors which contain silicon. In an engine application, high Si readings in conjunction with other elements such as Na, K and B may indicate a coolant leak.

Without other evidence, it is difficult to differentiate between additives, silicone and casting material as the source of silicon. However, dirt ingression can be determined by tracking both silicon and aluminum. For most common dirt which contains the minerals silica and alumina, tracking Si and Al, which should show up in lock step trend in the ratio 3.4:1, can be used to confirm dirt ingression.

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