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Book Bits

From the book "Reliability-Centered Maintenance II":

Care should be taken not to confuse causes and effects when listing failure modes. This is a subtle mistake most often made by people who are new to the RCM process.

For example, one plant had some 200 gearboxes, all of the same design and all performing more or less the same function on the same type of equipment. Initially, the following failure modes were recorded for one of these gearboxes:

• Gearbox bearings seize

• Gear teeth stripped

These failure modes were listed to begin with because the people carrying out the review recalled that each failure had happened in the past to their knowledge (some of the gearboxes were twenty years old). The failures did not affect safety but they did affect production. So the implication was that it might be worth doing preventive tasks like ‘check gear teeth for wear’ or ‘check gearbox for backlash’, and ‘check gearbox bearings for vibration’. However, further discussion revealed that both failures had occurred because the oil level had not been checked when it should have been, so the gearboxes had actually failed due to lack of oil. What is more, no-one could recall that any of the gearboxes had failed if they had been properly lubricated. As a result, the failure mode was eventually recorded as:

• Gearbox fails due to lack of oil.

This underlined the importance of the obvious proactive task, which was to check the oil level periodically. (This is not to suggest that all gearboxes should be analyzed in this way. Some are much more complex or much more heavily loaded, and so are subject to a wider variety of failure modes. In other cases, the failure consequences may be much more severe, which would call for a more defensive view of failure possibilities.)

Click here for more information about Reliability-Centered Maintenance II.

Today's Tip

• For the do-it-yourself auto enthusiast, when changing any filters on the vehicle, always write the mileage and date on the filter casing with a permanent marker, also record it on the vehicle’s service history docket. For the minor cost of an oil, fuel and air filter, frequent replacement will ensure a reliable and clean-running engine with added improvement in fuel economy.

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Q & A

"I've heard the term 'proactive maintenance' used in relation to maintaining lubricants. Can you explain how to implement a proactive maintenance program for lubricants?"

When this approach is applied diligently, proactive maintenance offers the biggest "bang for the buck" when trying to extend lubricant and machine life. We explain this strategy in greater detail in our training courses, but here's a basic explanation:

Proactive maintenance can be accomplished in three steps. The first step is to set a target, or standard, associated with each root cause of failure. These targets help ensure an environment is maintained that is conducive to prolonged lubricant and machine life.

In lubrication, root causes of greatest importance relate to fluid contamination (particles, moisture, heat, glycol, etc.) and additive degradation. However, the process of defining precise and challenging targets (high cleanliness) is only the first step. Control of the fluid's conditions within these targets must be achieved and sustained. This is the second step and often includes an audit of how fluids become contaminated and then systematically eliminating these entry points.

The third step is equally vital and is the action element of an oil analysis program. Specifically, control over these root causes within the targets is ensured only when constant feedback is supplied. Monitoring the oil with an oil analysis program provides this feedback.

Diligent application of proactive maintenance can extend oil and machine life by up to 10X. Click here to read a great article with more information about proactive maintenance.

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