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In This Issue:

• Up Front: Are You Keeping Your Line In The Oil?

• Book Bits: Low Oil Level Invites Condensation

• Today's Tip: Sight Glass Inspections
  

• Q & A: How Sulfur Is Used In Lubrication
  

Up Front

Are You Keeping Your Line In The Oil?

I did some fishing this past weekend. It was the rare trip where all of my equipment worked flawlessly, the weather was perfect, and the largemouth bass were biting. Truly a fisherman's paradise.

You've probably heard the old saying "You can't catch a fish if your line isn't in the water." This adage worked for me and is particularly true in oil analysis. When oil analysis is used to reduce maintenance costs and increase machine reliability, frequent and timely reporting of data is crucial.

I often hear people say "we sample that machine quarterly". In reality the machine is so critical to their operation that weekly oil analysis is easily justified.

When setting sampling frequencies, determine the mission criticality of each machine. Will its failure disrupt other processes or cause collateral damage? Is there redundancy or standby equipment?

To learn more about the factors to consider for timing your oil analysis sampling, check out the article "Establishing Effective Sampling Frequencies".

Mike Ramsey
mramsey@noria.com

Book Bits

From "Fluid Power Maintenance Basics and Troubleshooting":

Low Oil Level Invites Condensation

Low oil level is a serious cause of contamination in the hydraulic system. When the oil level is low, more air gets into the tank and this often leads to destructive cavitation in the pump and to condensation on the tank walls which generates sludge. Sludge decreases the lubricity of the oil, producing scoring and friction on surfaces with close tolerances.

Cavitation is the result of implosion - breakdown - of air or oil-vapor bubbles in the hydraulic system. It can be prevented by making certain that suction screens (if used) are clean and the oil reservoir is always full; this is another good reason for preventing leakage anywhere in the system. A clean reservoir with good return line filtration may eliminate the need for suction screens. Suction screens can be difficult to clean and as a result they may not be cleaned and pumps may be lost as the screens plug.

Click here for more information about "Fluid Power Maintenance Basics and Troubleshooting".

Today's Tip

• If there is a sight glass for the reservoir of the bearing lubricant, make sure there is a line that marks the level of the lubricant when the bearing is running and a line that marks the level of the lubricant when the bearing is stationary. (Tip submitted by Don Carrell, Fiske Brothers Refining Co.)

Each tip published will earn the sender $25. Click here to submit your tip.

Q & A

How Sulfur Is Used In Lubrication

"What is the difference between total sulfur and active sulfur contents in extreme pressure additives? How does sulfur (both forms) increase extreme pressure (EP) characteristics?"

Sulfur is used in many EP oils and metal working fluids as an EP additive. The basic way this works is for the sulfur to react at elevated temperatures, such as those experienced by meshing gears to form a sulfide layer. For example for steel gears, an iron sulfide layer is forms on the gear tooth surface. This ductile layer improves sliding contact, preventing scuffing or galling.

There are two types of sulfur compounds used, active and inactive sulfur. The main difference is that for active additives, the sulfur containing additive reacts with the surface at much lower temperatures, whereas, inactive compounds react only at much higher temperatures. While active additives have advantages of greater reactivity and hence may offer better anti-scuff protection, particularly at lower temperatures, they are also mildly corrosive particularly to yellow metals (brass, bronze etc.) and should be avoided where these alloys are present. In fact, active sulfur additive may cause the oil to fail the copper strip corrosion test (ASTM D130), while inactive sulfur will not be corrosive under these conditions.

The amount of active sulfur additive can be measured by first determining the total sulfur content using an appropriate ASTM test method (ASTM D129 or D4294), then reacting the active sulfur with copper powder and removing the copper sulfate by filtration, and again measuring the remaining total sulfur. This procedure is outlined in ASTM D1662.

Mark Barnes, Ph.D., Senior Technical Consultant, Noria Corporation

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