In This Issue:

• Up Front: Too Much Lubrication!

• Book Bits: When Oil Analysis Warrants Cautious Action

• Today's Tip: Timing of Filling Automatic Grease Systems Critical

• Q & A: Detecting and Solving Wrong Oil Problems
  

Up Front

Too Much Lubrication!

This happened in the early 1990s but is still relevant today. One of our power plants in Wyoming had two boiler-induced draft fans that were constantly leaking oil out of the bearing shaft seals. This had been going on for more than 10 years. During annual shut down of the plant, the seals were replaced, only to start leaking again after a few weeks.

The bearings had a forced lubrication system where oil was pumped up to the bearings and gravity flowed back to the sump.

As a new person transferred into that plant, I was able to look at the problem from a different perspective. I found the manual for the bearings and reviewed the operating instructions. The manual recommended the oil level in the sight glass should be between 1/3 and 1/2, never more than 1/2 the sight glass.

All four bearings on the two fans were between 5/8 and 3/4 full when oil flows were high enough to keep the bearing temperatures in normal operating ranges. This high level caused a hydraulic effect that pumped the oil right past the seals.

The operators did not suspect a problem because they could see an acceptable level of oil in the sight glass. The maintenance people replaced the seals periodically as instructed.

The oil level in the bearings was controlled by the height of a fixed steel plate dam in a four-inch vertical pipe on the outlet side of the bearing. The oil flowed over the top of the dam and went back to the reservoir. A plant mechanic cut some V-notches out of the top of the dam until the oil level in the sight glasses decreased to the proper level. The oil leaks stopped and have not reappeared.

The lube oil piping systems were probably fabricated onsite during construction and the dams were built just a little too high. When all else fails, read the directions again.

(Submitted by Loren Sievila, Production Consultant, Pacificorp. Thanks Loren!)

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Book Bits

When Oil Analysis Warrants Cautious Action

From a paper entitled "How to Read an Oil Analysis Report" in the "Practicing Oil Analysis 2000 Conference Proceedings.:

No matter what the level of wear, NEVER TEAR DOWN A MACHINE on the basis of one oil analysis report alone. Rush a follow-up sample to the lab to confirm the results and/or use other diagnostic tools at your disposal to further investigate the problem.

Click here for more information about "Practicing Oil Analysis 2000 Conference Proceedings".

Today's Tip

• Fill the grease reservoir in an automatic grease system only if it is 75 percent empty. Obviously, you never want the reservoir to run out of grease because this can cavitate the pump and let air into the system. However, if you fill them too frequently, the grease in the top half of the reservoir never leaves the reservoir.

  Grease reservoirs fill from the bottom because a follower plate above the grease pushes the grease into the pump cavity. Filling the reservoir too frequently keeps fresh grease in the bottom half of the reservoir while the older grease remains in the top half of the reservoir. The older grease travels up and down with the follower plate but never leaves the reservoir. Because grease is designed to release oil from the thickener when it is under pressure, the continual pressure from the spring above the follower plate can allow the stagnant grease to slowly bleed its oil over long periods. The stagnant grease then becomes stiffer as the oil-to-grease ratio is reduced.

  Eventually, the stagnant grease becomes too stiff to pump through the system if the reservoir is allowed to become empty enough for this stiffer grease to enter the pump. Coloration differences in the grease reservoir are signs of this condition.

  Annual cleaning of the grease reservoir will show you if this is happening and ensures that grease consistency is homogenous throughout the reservoir. (Submitted by Lee Montgomery, Castrol Industrial. Thanks Lee!)

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Q & A

Detecting and Solving Wrong Oil Problems

"Is there any way to tell if an improper lubricant is being used without performing an oil analysis, or without a part or system failure? We currently have an oil analysis program in place, but, I still find that wrong oils and fluids are being used from time to time, inbetween the oil analysis." - Tony Phillips, Georgia Pacific

The most effective way to determine if wrong oil has been used is by oil analysis, by looking at either a change in viscosity and/or a change in additive concentration etc. Unless there is a significant difference in oil type (viscosity, base oil type, additives etc.) or any dye that may be used in the oil or grease, it is unlikely that a sensory inspection is sufficient.

However, your problem in my opinion has little do to with oil analysis, but is more a procedural issue. Bottom line, we need to make those who are empowered with adding/changing oil understand why adding the wrong oil is bad.

The first stage is understanding through education, whether it be formal training or simply internal training sessions. Secondy, we need to make the process of adding oil as foolproof as possible. The best way to achieve this is to practice lube tagging. In this approach, new oils are tagged with a designated color and shape. For example, ISO VG 220 gear oil is given a red circle, AW 46 hydraulic fluid a green square, etc.

The next step is to similarly label dedicated oil transfer equipment such as oil top-off containers, funnels, filter carts, etc.

Finally, label the gearboxes etc., with the same red circle, green square etc. The strategy is simple: red-circle oil gets added to red-circle components using red-circle hardware. This can be applied to all components and hardware, including greases, grease guns, etc.

For more info on lube tagging, refer to the following article: GM Invests in Lube Program Updates

Mark Barnes, Senior Technical Consultant, Noria Corporation

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