In This Issue:

• Up Front: Bearing Installation Blunder

• Book Bits: If it Ain’t Broke…Don’t Fix It

• Today's Tip: Filter Change Procedure Caution

• Q & A: A Single Test for Diesel Engine Oil?
  

Up Front

Bearing Installation Blunder

In 1991 to 1992, while working as a service manager at an automotive dealership, I investigated a galling problem on the frontwheel spindles of several rear-wheel drive vehicles.

When the front hub/rotor assemblies were removed, it was obvious that the inner races had rotated on the spindle, which in turn caused the galling. I reviewed the work order histories on the vehicles and noticed that all the vehicles in question had been serviced by two mechanics.

One of the mechanics was still employed at the dealership, so I asked what his procedure was for front-wheel bearing packing/ installation. I immediately discovered the problem. He had the bad habit of applying a thin film of grease to the spindle before installing the hub/rotor assembly which contained freshly packed tapered roller bearings.

The grease in the freshly packed bearing had so much initial resistance (high unworked consistency) that when the vehicle was pulled out of the shop, the bore of the inner bearing race was actually turning on the shaft, rather than the tapered rollers going through their normal rotation inside the bearing races. This probably galled the shaft until the grease warmed up enough to allow the rollers to turn.

His concern was that if he didn't lubricate the shaft, the inner race bore surfaces may seize to the spindle. I assured him that I had never experienced this type of seizing problem.

Bottom line: When installing bearings on any applications with a slip fit between the bearings and the spindle/shaft - DO NOT APPLY GREASE TO THE SPINDLE/SHAFT. (Submitted by Greg Neuenfeldt, Technical Information Center, Dow Corning Corporation. Thanks Greg!)

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Book Bits

If it Ain’t Broke…Don’t Fix It

From Jim Fitch's article "Optimizing Oil Change Intervals to Reduce Lubricant Consumption" from the "Practicing Oil Analysis 2002 Conference Proceedings":

Often a lubricant remains serviceable for long periods of time without a drain and new lubricant charge (influenced by makeup rates, operating temperature, fluid volume, cleanliness, etc.). Draining an oil and adding new lubricants into a system presents risks such as:

1. Introduction of a wrong oil.

2. Introduction of a contaminated oil.

3. Introduction of an incompatible oil (with residual oil remaining in the machine).

4. Resuspension of settled contaminants in tank/sump floors and inactive zones.

5. Human agency failures (dead-heading pumps on restart, cleaning solvents not removed, introduction of contaminants, loosening of machine parts, etc.).

When compiled with real cost and associated risk of an oil change factored in, it is often wise to let the conditions of the oil drive the decision.

More information about "Practicing Oil Analysis 2002 Conference Proceedings".

Today's Tip

• In a recent issue of Lube-Tips, it was stated: "When replacing top-suspended spin-on or threaded canister-type filters, fill them with fresh oil before installation. This will reduce the amount of time that the engine or machinery undergoes dry start-up by having that extra available amount of oil available. In some cases, it could also prevent filter damage when a gush of high-pressure fluid hits a dry element."

  For many heavy mobile equipment manufacturers, the above mentioned is not an approved practice. Many of the newer Caterpillar models are equipped with prelubrication systems making this a step that can greatly increase the risk of contaminants entering the new lubricating oil.

  After an oil change (unless the system has been flushed) there will be enough residual lubricant that an "at idle - no load" startup will not cause any damage, and there is much less chance of contaminants entering the system.

  All oil changes should be done with the oil warm. This assures that the contaminants in the system to be drained are already in suspension in the old oil, and that the system has a good film of oil on all the moving parts to protect them during the new filter fill and start up. Automatic pressure prelube systems are still the best answer. (Submitted by Richard Driver, Equipment Contract Engineer, Finning Chile S.A. Thanks Richard!)

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Q & A

A Single Test for Diesel Engine Oil?

"I am considering a diesel engine oil analysis program. I am interested in analyzing the oil onsite. Would a viscometer (falling ball type) be an acceptable means to determine the condition of engine oil and the engine oil change interval onsite?"

Despite the fact that so many lubricant health and contamination problems may be revealed by viscosity measurement, I can't endorse a strategy that relies solely on viscosity measurement to base oil drain decisions in a diesel engine application.

Here are a few reasons why:

1. While it is true that VI improver shear down may be revealed by viscosity measurement, oxidation of the base oil and/or soot accumulation can offset the viscosity change.

2. While fuel dilution results in a drop in viscosity, soot and oxidation increase it. Soot and fuel often enter at the same time because they share many of the same causes (rich mixture, poor atomization of fuel, worn rings, malfunctioning fuel injectors, excessive idling, lugging, etc.). If soot and fuel enter the oil simultaneously, you have the risk of a viscosity measurement offset.

3. Viscosity measurement fails to reveal the oil's dispersancy performance, detergency/reserve alkalinity, antiwear additive life, etc. - all critical properties.

4. When you use oil analysis just to decide when to drain the oil, you forego the most valuable aspect of oil analysis, which is its ability to reveal the health of the machine and/or identify unhealthy contaminant conditions.

If your engines are valuable and used in mission-critical or important applications, I advise you to employ an oil analysis testing program that truly reveals the important information you need to make smart lubrication and machinery maintenance
decisions.

Drew Troyer, Noria Corporation

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