In This Issue:

• Up Front: Quick Fix Simplifies Bearing Monitoring

• Book Bits: Hidden Cost Reduction Opportunity - Seals

• Today's Tip: An Inexpensive Breather Filter Alternative

• Q & A: Scheduling Engine Oil Changes
  

Up Front

Quick Fix Simplifies Bearing Monitoring

Some time ago we lost a bearing on a forced draft fan. This was puzzling because the oil sample from the bearing case drain port didn't show any indication that the bearing was failing.

While the mechanics were replacing the bearing I looked at the case. I found that the sample port was above the bottom of the case and about 46 cubic inches of oil was below the sample port. Because it is a non-circulating system (slinger ring lubrication), the bearing could completely wipe out, and I'd never get an indication of it from the normal sample port. The sample port was too high to collect the wear debris that sank to the bottom.

We had a new drain port installed at the bottom of the case and attached a minimess sample port. If a sample from this port doesn't show babbitt or too much water, we know we are OK. If too much of either shows up, we can schedule downtime. This solution has worked well for us.

Submitted by Les Harrington and Jaime Viramontes, El Paso Electric.

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Book Bits

Hidden Cost Reduction Opportunity - Seals

From "The Practical Handbook of Machinery Lubrication":

Cost cutting by machine design engineers, incomplete commissioning and plant start up procedures and inadequate equipment condition monitoring and maintenance practices, are the major reasons for initial seal failure and fluid leakage.

Once a seal has failed and fluid leakage results, the problem is perpetuated by bad purchasing department policies of purchasing and restocking low quality (read less expensive), or incorrect seals, or by careless installation practices used during replacement procedures.

The subsequent leaks, while not considered excessive, go on and on and soon, plant operating and maintenance personnel accept the leakage as normal.

The lack of attention to a few basic details cost millions of dollars annually in external fluid wastage, unnecessary maintenance downtime and environmental damage.

Click here for more information about "The Practical Handbook of Machinery Lubrication".

Today's Tip

• Good low-cost, dirt-removing breathers are spin-on-type oil filters. They have common thread fittings, the breathing holes are at the bottom, deep filter elements, low cost and common at most companies. (Submitted by Byron Martin, Condition Monitoring Engineer, MechTest)

Each tip published will earn the sender $25. Click here to submit your tip.

Q & A

Scheduling Engine Oil Changes

"My laboratory provides feedback on kinematic viscosity at 100°C for our engine lubes. At what level of viscosity change should we drain the engine oil?"

Because viscosity changes can be an indication of a number of problems whether the change is an increase or decrease (or both, therefore negating any perceivable change), then monitoring viscosity alone as an indicator of engine oil change is insufficient, especially on engines.

Engines can suffer fuel dilution resulting in a decrease in viscosity, as well as glycol or soot loading resulting in an increase in viscosity. Changing the oil will not cure the root cause of these problems. In addition, if a multi-grade engine oil is used, then a decrease in viscosity is possible because the viscosity index improvers shear in service. Further inspection or a more detailed confirmation analysis will be necessary to determine the cause if the viscosity has changed before the end of the anticipated service life.

However, on engines, setting both upper and lower caution and critical limits will be an alert to oil life and contamination issues. The recommended lower limits are -5 percent and -10 percent, while the upper limits are +10 percent and +20 percent. These kinematic values are based on changes in cSt at 100°C.

Martin Williamson, Senior Technical Consultant, Noria UK Ltd.