In This Issue:

• Readers Challenge: Transitioning to a New Lube Supplier

• Book Bits: Fatigue in Babbitted Bearings

• Today's Tip: Particle Settling Affects Sampling Results

• Q & A: Keep Air Clean Because . . .

Readers Challenge

Transitioning to a New Lube Supplier

Your company has switched to a new lubricant supplier (Supplier B). You are no longer able to buy lubricants from the previous supplier (Supplier A). All of your machines currently use lubricants from Supplier A. Some of these machines are small oil compartments (gears, bearings, etc.) that need occasional top-ups and annual oil changes.

Other machines are large circulating oil systems for which oil is changed "on condition", based on oil analysis. Many motor and fan bearings are grease lubricated. The lube storage room has containers of the Supplier A products but now Supplier B products are beginning to arrive.

People are asking questions about compatibility and other reliability impacts the transition might cause. What would you do?

Submit your answer at http://www.noria.com/challenge.asp before Tuesday, April 29, 2003. Lube-Tips editors will choose the best answer and the $100 recipient will be announced next week.

Book Bits

Fatigue in Babbitted Bearings

This Book Bit is from the paper "Damage Analysis of Babbitted Bearings" in the Lubrication Excellence 2003 Conference Proceedings:

As a material, babbitt has a temperature-dependent fatigue strength. During operation, dynamic stress on the surface of the babbitt arises from dynamic forces (shaft or housing vibrations), thermal cycling or process impacts.

Cracks generally initiate at the surface and propagate toward the intermetallic layer. Being stronger than the base babbitt, the crack will generally not propagate into the intermetallic layer, but will turn parallel to this layer. Small sections of babbitt may become dislodged, leaving the intermetallic layer uncovered.

More information about the "Lubrication Excellence 2003 Conference Proceedings"

Today's Tip

• The time when an oil sample is taken is an important factor in obtaining representative and trendable oil analysis data. The optimal time to take the sample is during the machine's normal operation because, after the shutdown, all the particles begin to settle. The rate of settling is defined by Stoke's Law.

  Here is an example of how quickly some particles can settle four inches (assuming spherical-shaped particles):

  50-micron silica particle: 12 minutes
  50-micron steel particle: 2.1 minutes
  50-micron copper particle: 0.8 minutes
  50-micron chromium particle: 2.5 minutes

  (Submitted by Lino Montoro Moreno, CMT - Motores Termicos)

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

Q & A

Keep Air Clean Because . . .

"I run a fleet of heavy-duty trucks and have learned much about the importance of keeping engine oil clean. My question is, how relevant is intake air cleanliness?"

On a volume basis, diesel engines can use more than twenty thousand times more air than fuel. Airborne dirt is abrasive to engine components and therefore efficient air filtration is vital in avoiding premature engine wear.

In particular, turbocharger compressor blades are eroded by airborne dirt. This results in reduced efficiency causing engine power loss, increased fuel consumption and higher exhaust emissions.

Quality air filtration systems are designed to trap most harmful dirt, but regular attention is required to assure efficient filtration without causing air restriction and intake system leaks.

Periodic oil sample analysis is a useful tool for determining if your air filtration maintenance practice is doing the job because it will identify silicon, iron and other elements common to airborne dirt and wear debris in the oil.

Hugh Lundin, Technical Consultant, Noria UK Ltd.

Submit your question here.

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