In This Issue:

• Up Front: Oil Sampling Reveals Air-In-Oil

• Book Bits: Responding Proactively to Seal Failures

• Today's Tip: Sump Cleaning Caution

• Q & A: Remaining Useful Life Testing

Up Front

Oil Sampling Reveals Air-In-Oil

While pulling a sample from a 100-gallon reservoir, an exceptional amount of air was found entrained in the polyol- ester hydraulic fluid. Using a low viscosity mineral oil in a trigger spray bottle, the suction-side components were sprayed in an attempt to locate where the air was being ingested.

The input shaft seal of the pump was sprayed and the pump became noticeably more quiet. The sprayed oil was seen being drawn into the pump.

A check of the pump revealed a worn bearing and shaft seal - both attributed to contamination in the oil. The pump was replaced and the source of contamination entry was located.

Bottom line: Your oil is talking to you. It pays to listen. (Submitted by Mike Deal, Maintenance Analyst, Alcan Aluminum, Sebree, KY. Thanks Mike!)

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Book Bits

Responding Proactively to Seal Failures

From "The Practical Handbook of Machinery Lubrication".

When a seal fails, don't just replace it. Determine the real cause of failure. Some causes for failures, which are often ignored, are listed below.

1. Misalignment of components.
2. Poor bearing lubrication.
3. Vibration of rotating components.
4. Contaminated fluid (water, acids or particulate).
5. Twisting condition due to "soft foot" at mounting pads.
6. Poor component base plate grouting or mounting.
7. Rotor imbalance or shaft whip.
8. Inadequate flushing procedures during commissioning or start-up after repairs.
9. Poor, or careless seal or bearing installation.
10. Piping strains, due to misalignment or temperature variations.
11. Looseness of bolts and brackets.
12. Addition of incompatible fluid.
13. An increase in temperature (or a dramatic change in temperature).
14. Unclean operating conditions (causing dirt ingression).
15. A change in filtration practices.

"Selecting the correct seal is only the beginning of sound equipment operation. Ongoing predictive condition monitoring using vibration and fluid analysis, a regular review of equipment operating logs and the implementation of a sound preventive maintenance program, will ensure the long life of seals, eliminating leaks and environmental damage and will add millions of dollars to the bottom line.

More information about "The Practical Handbook of Machinery Lubrication".

Today's Tip

• While cleaning out your sump that contains EP gear oils, do not use any form of degreasers or detergents. These items will most likely cause foaming problems and reduce the overall characteristics of the gear oil properties.

  For the best results, try using an alkaline cleaner that will effectively remove oily residues along with grit and dirt from the interior of your tank. This product is recommended for general maintenance applications along with coolant system cleanouts. (Submitted by Stan, regional account representative, Allegheny Petroleum Products, Wilmerding, PA. Thanks Stan!)

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Q & A

Remaining Useful Life Testing

We recently had a number of our lubricants tested for oxidation stability (RPVOT - ASTM D2272). The results indicate that the mineral-based turbine oils are all within limits, all greater than 50 percent remaining life. However, the mineral-based hydraulic fluids are in the caution zone (between 25 and 50 percent remaining life). All other oil analysis parameters for these oils are within specification.

My question: is the oxidation stability test (ASTM D2272) applicable to mineral-based hydraulic fluids or is it limited to turbine oils? - Tony Cattaert, ESKOM, Tutuka Power Station, South Africa.

You are right; the rotating pressure vessel oxidation test (RPVOT) was originally developed for turbine oils. However, the stressing conditions used to determine oxidation stability are suitable for many other similar lubricants including mineral-based hydraulic fluids, R&O oils, compressor lubricants and many gear oils.

Passenger car and heavy-duty diesel motor oils can best be tested using the thin film oxidation uptake test (TFOUT) (ASTM D4742) which employs stressing conditions and catalysts more typical of those found in engine crankcases.

In general, the need for oxidation stability testing of lubricants relates to the need to extend oil drain intervals or simply to perform condition-based oil changes. Oxidation stability is one of several important conditions that help define end of useful life. Other similar tests for oxidation stability include cyclic voltametry, differential scanning calorimetry, and interfacial tension.

Jim Fitch, Noria Corporation

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