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In This Issue:

• Up Front: Check Your PMs for Problems

• Book Bits: Keeping Stored Lubricants Clean

• Today's Tip: What Causes Viscosity to Rise?

• Q & A: Pump Bearing Life

Up Front

Check Your PMs for Problems

Lately we have had problems with one of our many 5-ton overhead cranes, which are integral in our material handling process. The hoists are 20 feet above ground and carry massive rolls of film. Critical maintenance downtime pushed us to a long-overdue reliability check.

We found that one of the gearboxes retained sludge deposits in its casing, while the other was noisy. It turns out that one gearbox was to be greased, while the other one was to use oil.

Preventive maintenance was performed on both gearboxes with the same OIL, which wasn't even the correct viscosity oil! Not only were we lubricating this hoist incorrectly, but we also employ eight others which were lubed in the same manner! This also created a serious safety hazard in addition to lost production.

Bottom line: Double check the validity and accuracy of all PMs. Just because it's there doesn't mean it is correct. (Submitted by Adam Ligda, Reliability Engineer, AET Films. Thanks Adam!)

Each Up Front story published will earn the sender $100. Submit a case study, experience or lesson learned. Or e-mail lubetips@noria.com.

Book Bits

Keeping Stored Lubricants Clean

From "Lubrication Fundamentals"

If simple precautions are not observed, contamination of lubricants with subsequent damage to machines can occur during storage or during transfer of oil or grease from the original container to the dispensing equipment, or to the equipment being lubricated. Pumps, oil cans, grease guns, measures, funnels, and other dispensing equipment must be kept clean at all times and covered when not in use. Where operating conditions justify them, centralized dispensing or lubrication systems that keep the lubricants in closed systems and, therefore, protected against contamination, are highly recommended.

More information about the book "Lubrication Fundamentals"

Today's Tip

• Assuming that no water is emulsified in the system, some reasons for an increase in viscosity of a circulating oil might include:

  • The oil may have oxidized.

  • Pressure could have increased.

  • Temperature might have decreased.

  • Possible contamination with a higher viscosity fluid.

  • Evaporative losses of light oil fractions from high temperatures

  • Glycol contamination

  • Soot contamination

Each tip published will earn the sender $50. Submit your tip.

Q & A

Pump Bearing Life

"Can operational factors affect bearing life in centrifugal pumps?"

Certainly. There is substantial theoretical and field research that indicates that a variety of operational factors influence pump life. The most sensitive components, and therefore the ones to show damage first, are mechanical shaft sealing devices and rolling element bearings.

Operating well off the best efficiency (or design) point of the pump's curve creates higher-than-normal-thrust loads in the bearing housing. These pumps are designed to cancel out much of these loads at their expected design point.

Load is a fundamental parameter in calculating L10 life, and therefore any increase in loading (especially the combined radial-thrust loading found here) has a harmful effect on life.

Adam Davis, Technical Consultant, Noria Corporation

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