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In This Issue:

• Up Front: Lubricant Specifications Can Change

• Book Bits: Analyzing Oil With Your Fingers

• Today's Tip: An Unusual Breather Treatment

• Q & A: Engines With No Oil Sump?

Up Front

Lubricant Specifications Can Change

A gearbox used in an extruder application had a data plate clearly specifying an AGMA 4 lubricant as the appropriate product. The proper product is installed and within two years the gears become severely pitted.

The unit is rebuilt, put online, and again the AGMA 4 product is installed. The lubricant vendor is not notified of the failure as the maintenance staff saw no need to contact them since the unit has a history of being problematic.

The unit fails again after three years and this time the lubricant vendor is called in to provide assistance. The investigation reveals the following:

• The gearbox data plate states the unit is rated for a 150 HP input.

• The unit has been connected to a 200 HP motor since the initial installation.

• The input shaft speed has been reduced substantially from the initial design.

• The gears installed were not hardened, due to the need to get the unit back online as soon as possible after the first failure.

Due to the severe loading and reduced input speed experienced by this unit, the lubricant vendor decided to change the lubricant recommendation to an AGMA # 6EP product.

The lesson: look at all parameters and ask appropriate questions regarding problematic unit history to determine if the manufacturer's lubricant recommendations are still appropriate for the application as it is being used presently. Do not assume that because the data plate states a specific lubricant grade is recommended that it is the optimum product today. (Submitted by David Piangerelli, Lubrication Technologies, Inc. Thanks David!)

Each Up Front story published will earn the sender $100. Submit a case study, experience or lesson learned. Or e-mail lubetips@noria.com.

Book Bits

Analyzing Oil With Your Fingers

From "The Lubrication Field Test and Inspection Guide"

Our sense of touch is not a good oil analysis instrument. In fact, it is difficult to detect even highly contaminated oils with your fingers. Most particles that are large enough to be felt have very short life in the oil. They become filtered, crushed, or simply settle to the bottom of tanks and sumps.

Therefore, in order to feel these contaminants, to get a sense of the consistency, hardness and size, it is best to go to the places where they accumulate. These places include the bottom of the sample bottle, a tank/sump BS&W (bottom sediment and water) sample, sediment from centrifugal separators, and debris on the surface of a used filter.

Download this e-book here or get the printed version here.

Today's Tip

• Washing down machinery with water often results in desiccant breathers becoming saturated with water. One solution we have is to put panty hose over the breather. Though it may look silly, it repels the water yet allows air to move through it and is easier than training personnel over time. (Submitted by Coby Norrid, Lead Tech, Intel Corp. Thanks Coby!)

   

Each tip published will earn the sender $50. Submit your tip.

Lubrication Excellence 2003 Proceeding Now Available

If you missed the Lubrication Excellence 2003 Conference, get the next best thing - the Official Conference Proceedings. Go to our online bookstore or call 1-800-597-5460 to purchase.

Q & A

Engines With No Oil Sump?

"In a small two-stroke engine, the oil is mixed with fuel in the ratio 1:50. This is the same oil which lubricates the engine. How can it provide adequate lubrication of bearings etc. if it is so heavily mixed with fuel and hence has such a low viscosity?"

Most of the small marine two-cycle engines are air-scavenging type. On the upstroke they pull air through the bottom of the cylinder and trap the air in a cavity designed for this function. When the piston passes a valve (upon downstroke), the air passes into the combustion chamber, pushes out the exhaust gas and begins to compress on the following upstroke.

The fuel mixture is sprayed into the chamber when the gas is compressed, and then ignited. Two-cycle engines are lubricated either by oil from the crankcase or by oil mixed with the fuel and fed into the chamber during routine operation. Both designs are widely used. For instance, an outboard boat engine is a premix (oil and gas) fuel, where my two-cycle riding mower engine has a crankcase that requires service.

For the premix design, some portion of the lubricant is burned with the fuel. It is hoped that the mixture is just heavy enough to promote oil condensation on mechanical parts. But not so much that deposits accumulate excessively. Remember that the oil films that we depend on are in the neighborhood of a few microns (millionths of a meter) thick.

The amount of oil in the fuel mixture is calculated to provide just enough coverage to get the job done, with very little excess vented to atmosphere. However, depending on the age of the engine, perhaps as much as 30 percent of the fuel/oil mixture is vented without being burned. This is a concern to environmentalists, and may explain some concern over weed eaters, blowers and lawn mowers.

Mike Johnson, Senior Technical Consultant, Noria Corporation

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