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In This Issue:

• Readers Challenge: What Does Hot Really Mean?

• Book Bits: The Operator's Job in Preventive Maintenance

• Today's Tip: Solution for Cracked Grease Lines

• Q & A: Trending Water Contamination

Readers Challenge

What Does Hot Really Mean?

Last week we asked: Shortly after regreasing a rolling element bearing in a horizontally mounted indoor motor under light load, the bearing is found to be running hot. It is an 1800 rpm application in continuous service, greased every three months (nominally). What steps do you take to diagnose the overheating problem?

Winning answer: 1. Collect data to determine what hot means. (Compare with similar equipment, look at maintenance records and take actual temperature reading.)

2. Contact lubrication technician to see what he or she observed at the time of lubrication. (What and how much grease was used at the time.) Steps 1 and 2 will help to ensure that you are defining the problem correctly. In this case, the bearing is running too hot, after lubrication.

3. As approximately 60 percent of bearings fail due to improper lubrication, we should take a sample of the grease and have a tribology lab determine: a) Was the proper grease applied? b) Was too much grease applied? Ultrasonic testing will also tell if too much grease has been applied. c) Were contaminants introduced at the time of lubrication?

4. If none of the above is applicable; what else changed, if anything, at or around the time of lubrication?

5. Perform vibration analysis if possible, to ensure that the equipment is aligned correctly.

6. Perform root cause analysis (RCA).

(Submitted by Patrick McCaffery, RCM/RCA Coordinator, Eastman Kodak Company. Thanks Patrick!)

Book Bits

The Operator's Job in Preventive Maintenance

From "Wear Debris Analysis"

The whole concept of Wear Debris Analysis (WDA) is based on the idea that debris released from a system conveys the condition of that system. Take a simple example: if a hose is being flexed and no debris is being generated from it, then the hose is probably in excellent condition and likely to last a long time; however, if bits of hose are coming off the surface (either within the hose or on the outside), then the likelihood is that fracture will occur soon.

More information about the "Wear Debris Analysis"

Today's Tip

Solution for Cracked Grease Lines

• If remote steel or plastic grease lines leak due to cracking from joints and assembly points caused by vibration or UV, replace them with fire-resistant heavy-duty hydraulic hose. We replaced all our stainless-steel fin fan remote grease lines with rubber hosing, which are more resistant to ambient vibration and UV. Prior to this, repair of broken steel and plastic grease lines was a big maintenance task. Of course, when these lines break and do not get reported on time, costly consequential fin fan bearing failures were also common. Now bearing suppliers complain that they do not sell the same volume of fin fan bearings and housing to the refinery anymore. (Submitted by Noyan Ercan, Reliability Engineer, Shell Clyde Refinery. Thanks Noyan!)

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Q & A

Trending Water Contamination

"Our monthly oil analysis reports have shown that a few of our systems have between 400 and 500 ppm of water consistently. The OEM of the equipment has told us that water levels under 500 ppm are OK for this system and we shouldn't worry about it. What level of water is acceptable for hydraulic systems and hydraulic fluid?"

The short answer to this question is that there is no acceptable level of water in a hydraulic system or hydraulic fluid. Any amount of water will have an effect on the chemical properties of the lubricant and the metal surfaces of the components and reservoir. Simply stated, the degree of damage to the oil and to the machine depends upon how much water is present and for how long.

The long answer is more complex. Additives used in some hydraulic fluids, in particular antiwear (AW) additives, can interfere with the instrument most commonly employed to test for water contamination, making the results appear higher than they actually are.

So, you need to trend the lab data that you have received to first determine if the moisture concentration has been increasing, decreasing or has remained stable over a given period of time. If you find that the levels on your lab reports have either decreased or remained stable over a significant period of time, you should remove the water using a vacuum dehydrator, centrifuge, water absorbing filters or some other form of dehydrating separator (several good ones can be found in the marketplace).

And, you should undertake root cause analysis (RCA) to determine the nature of the water ingress and make any changes necessary to prevent recurrence. Common sources of water include lubricant top-ups, faulty or ineffective breathers, poorly sealed hatch covers, leaky oil coolers, aggressive wash down practices, etc.

Jason Kopschinsky, Technical Consultant, Noria Corporation

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