Most of us clean the coupler and even waste the first couple pumps of grease to push out any debris before using a grease gun for the first time. Until recently, I did not pay much attention to the inside of a new grease gun. I discovered that the barrel and rubber plunger can be contaminated with dust, metal filings and other debris from the factory. (Five out of five new grease guns from two different manufactures were dirty on the inside.) Now, I clean them all before putting them in service for the first time. (Jerry Baker, Lubrication Specialist, DuPont Tate & Lyle Bioproducts)

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From the book "Practical Plant Failure Analysis":

There have been many studies that have shown that water contamination reduces the fatigue life of rolling element bearings. From 1960 to date, we are aware of at least seven extensive analyses, none of which had the operating conditions duplicating other studies. Based on them, we feel that there can be consistent reduction in life at water concentrations as low as 0.01% (100ppm) and recommend that water levels be kept below half of that (50ppm).

One of the problems that water presents is that, as a polar molecule, when it is put under pressure it does not increase in viscosity like lubricant oils. When it contaminates the typical hydrocarbon lubricant and is put under pressure, it tends to vaporize, removing the cushioning layer in the Hertzian contact zone. A second problem is that when the bearing is shut down, the water leads to corrosion.

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"What is the correct oil level for a worm gear when the worm is on top?"

If the worm is on the top, the oil level should be such that the teeth at the bottom of the wheel are submerged in oil so that the oil will be carried up to the gear contact between the worm and the wheel.

Please ensure that the bearings on the shaft of the worm (on top) are either grease-lubricated or that there is enough splash from the wheel to get oil to those bearings. The OEM may have incorporated a flinger and oil channels to direct oil to these upper bearings.

If a gearbox that was designed with the worm to be on the bottom, is then mounted upside down, thus putting the worm on top, lubricating the shaft bearings may now be impossible.

If the worm is on the bottom (by design), the oil level should be halfway up the worm (the worm should be half submerged).

Bob Scott, Noria Corporation

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