In This Issue:

• Up Front: Lube Audit Worth the Investment

• Book Bits: Maintaining Hydraulic Fluid

• Today's Tip: An Abrasive Reaction

• Q & A: Why Does Grease Harden?

Up Front

Lube Audit Worth the Investment

We contracted an independent agent to do a lube site audit. It was an expensive proposition; however, the resulting report was condensed into a five-year plan and the model was applied across the entire maintenance operation.

A review shows we are presently at about 80 percent compliance with the recommendations. More importantly, the attention to lubrication excellence resulting from the practices has carried over to the maintenance personnel.

Proper lube practices have resulted in phenomenal saving in maintenance costs and reduced downtime percentages as well.

Some highlights include handling, conditioning, analysis and environment. The lube site audit provides a game plan and a unified strategy in the same package. I strongly recommend this practice to any operation looking to improve its overall performance.

(Submitted by Howie Nore, industrial mechanic/millwright, Gerdau Ameristeel. Thanks Howie!)

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Book Bits

Maintaining Hydraulic Fluid

The Practical Handbook of Machinery Lubrication is packed with useful information. Here are recommendations from the book on maintaining hydraulic fluid and equipment:

• Keep hydraulic fluids cool. (The bulk oil temperature at the exterior of the reservoir should never exceed 60 degrees C (140 degrees F)).

• Keep hydraulic fluids clean. (There is general agreement among hydraulic experts that 75% - 80% of hydraulic failures are caused by fluid contaminated with dirt, wear particles and other foreign material. In today's high-pressure systems, clearances between wear surfaces are very small, making contamination control critical).

• Keep hydraulic fluids dry. (Water and condensation content should never exceed a maximum of 1000 PPM, depending on the system design).

• Immediately repair fluid leaks. If oil can escape, dirt and dust can re-enter the system. (A fluid leak of one drop per second is equal to 400 gallons in a 12-month period.)

More information about the book "The Practical Handbook of Machinery Lubrication"

Today's Tip

• Abrasive wear can cause a chain reaction in lubricated machinery. The typical chain reaction is:

  • Abrasive particles become work hardened.

  • Work hardened particles produce more particles.

  • New particles become work hardened.

  • Chain reaction continues until the particles are removed by filtration or the machine fails.

   

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Q & A

Why Does Grease Harden?

"What causes the hardened cake-like material to form in grease- lubricated bearings?"

This is generally due to oil separating from the thickener. While it is normal for small amounts of oil to blend from the thickener over time, a grease with excessive bleed characteristics may harden in the bearing prematurely.

In some cases, too much time has passed between relubrication. The solution would be to shorten the interval, say from one year to six months. It is generally a good rule of thumb to schedule relubrication when half of the original oil-in-soap content is lost.

High temperatures caused by overlubrication can often lead to the caking condition. There are also other causes of high heat.

Whatever the source, the heat can either boil the oil out of the thickener, promote premature bleed, or induce oxidation (thickening) of the base oil. All can cause a hardened residue left in the bearing.

High centrifugal forces in large high-speed bearings can cause oil to separate from the thickener prematurely as well.

Jim Fitch, Noria Corporation

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Lube-Tips is published by Noria Corporation. Oil Analysis and Lubrication Experts