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In This Issue:

• Today's Tip: Regreasing During Operation

• Book Bits: Selecting Bearing Lubricants

• Lube-Trivia: Important Hydraulic Fluid Properties

• Q & A: Coolant in Oil Analysis

Today's Tip

Regreasing During Operation

• When adding grease to bearings through grease fittings or other ports, it is usually best to add grease while machinery is in operation if safety permits. Depending on the application, this allows excessive grease, with the aid of the moving bearing elements, to be pushed out of the bearing track to an adjacent cavity, vent port or other exit pathway. (Submitted by Geoffrey Bidlack, Engineering Supervisor, NTN Bearing Corporation of America. Thanks Geoffrey!)

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Book Bits

Selecting Bearing Lubricants

From "Rolling Bearings Handbook and Troubleshooting Guide"

When bearings have to operate in a wide range of temperatures, use an oil that has the least viscosity change with changes in temperature - i.e., an oil with a high Viscosity Index (VI). In many applications, pure mineral oils are most satisfactory. They should be free from contamination, and they should resist oxidation, gumming and deterioration by evaporation of the light distillates. Finally, they must not cause corrosion of any parts of the bearing during standing or operation.

More information about the book "Rolling Bearings Handbook and Troubleshooting Guide"

Lube-Trivia

Important Hydraulic Fluid Properties

Test your knowledge and prepare for ICML lubrication and oil analysis certification with Lube-Trivia.

QUESTION: Besides viscosity, what are other important properties of hydraulic fluids?

For the answer, visit: http://www.lube-tips.com/trivia/20031112asp

Q & A

Coolant in Oil Analysis

"We recently received an oil sample report from our lab indicating a coolant leak, even though the results for the FTIR test for glycol came back negative. Is the lab wrong or is there something I'm not understanding here?"

Laboratory tests for glycol, which include both FTIR and Schiff's reagent, are designed to measure the presence of glycol molecules in an oil sample. However, depending on where and how the glycol is entering the engine, it may burn before it even reaches the oil. Because combustion will destroy the glycol, any chemical test for its presence will be negative, even though a serious coolant leak may be present.

Most labs are aware of this problem and do not rely solely on the presence (or absence) of glycol to warn of potential coolant leaks. Instead, they take advantage of the characteristic "elemental fingerprint" of common inhibitors that are used in engine coolant. These inhibitors typically include sodium-, potassium- or boron-containing molecules. Because most crankcase engine oils do not contain sodium or potassium (though many do contain boron), the presence of either of these in an oil sample may indicate a coolant leak.

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