During regular weekly and monthly oil sampling, we have been using a tube of "handy wipes" to keep our hands cleaner while handling sample equipment. This practice may not show directly in the cleanliness of the samples, but it feels cleaner, looks professional, and sends a message about the importance of contamination control. (Submitted by Charles Gurr, NorskeCanada.)

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Book Bits: Advice for Electric Motor Bearing Grease

From the book "Basic Handbook of Lubrication"

EP-type greases are used with roller bearings under heavy loads and normally provide no advantage with electric motor ball bearings. Rust and oxidation (R&O) greases are commonly used. Also, if an EP-type grease leaks into the windings, the typical EP additive may be corrosive to yellow metals, such as copper, at temperatures above 65 degrees C.

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"We have a large worm gear drive used in a coal pulverizer bowl mill gearbox. The bowl mill manufacturer recommends using a sulfur-phosphorous EP gear oil, however our lubricant supplier has sharply recommended against it. Also, there is a question with respect to which viscosity we should use: ISO VG 320 or VG 460?"

There are a variety of different views about the proper way to lubricate worm gears. You can find a couple articles on the subject in the Noria Learning Center, as well as an article by Arnold Shugarman on active sulfur EP additives.

In general, I consider recommendations to stay clear of sulfur- phosphorous EP additives in worm gears to be an over generalization.

The AGMA 9005-D94 statement on S-P additives is cautionary, stating that, with respect to double-enveloping worm gears, that S-P be used only when specifically recommended by the gear manufacturer (as in your case). Regarding viscosity, I suggest you refer to Tables 7 and 8 in this AGMA guideline which calls out specific viscosities for worm drives - based on such factors as pitchline velocity and temperature.

Back to the S-P EP question, I believe the high friction/heat commonly generated by worm gear drives requires EP or equivalent protection (FZG Stage >12). Indeed, the sulfur of some additives systems (such as a GL-5 gear oil used in automotive differentials) may be too aggressive toward bronze.

Bronze is commonly used in the large bull gear of the worm drive. However, unlike cutting fluids and GL-5 gear oils, the sulfur in most industrial EP gear oils should not be "active" and aggressive toward copper at temperatures below 100 degrees C.

For worm gears running at higher temperatures, test for copper tarnish at the highest expected temperature (three days) using the ASTM D130 copper strip procedure.

There are S-P EP gear oils formulated specifically for worm gears with a lower treat rate (lower additive concentration). These S-P additives are pacified and don't contain active sulfur. The two varieties are either absolute inactive sulfurized EP or a medium- active sulfur carrier. When used in combination with yellow metal deactivators (special corrosion/oxidation inhibitors), there should be minimal risk of corrosive attack of the bull gear even at moderately high temperatures.

Also, many users prefer polyglycols instead of mineral base oils. Polyglycols give comparable wear control without the use of EP additives - reducing the risk of bronze corrosion.

Jim Fitch, Noria Corporation

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