Include tests that can detect impending failures and prevent them from happening.
Maintenance manuals for various kinds of production equipment typically contain a section with recommended preventive maintenance procedures and another with a troubleshooting guide. The recommendations usually call for taking voltage measurements, and for simplicity these are typically basic measurements.
From this, we can’t logically conclude that our testing needs are limited to basic voltage measurements. And, of course, we don’t conclude this. The typical maintenance shop has sophisticated digital multimeters (DMMs), rotation testers, insulation resistance testers, vibration testers, and other test equipment to support “standard” tests.
That is all good, but do you want to perform standard tests or do you want to detect impending failures and prevent them from happening? Do you also want the ability to troubleshoot with precision?
Let’s look at an example of this second item. An Ohio process plant used long runs of low-voltage signal cables. Sometimes, because of thermal stress or some other problem, a cable will fail. The operators usually can spot this because a given process variable would go from normal to zero on their console. Sometimes the problem was one of several connections in the run.
The initial response from maintenance was to pull entirely new cables from point to point. This was time-consuming. To address the specific problem, the plant bought a time domain reflectometer (TDR). This enabled maintenance workers to know exactly where the cable fault or other problem was. They could usually perform a quick repair rather than pull new cable.
Then someone at the plant had a light bulb come on in his head. And that brings us back to that first item. His idea was to conduct predictive TDR testing on the signal cables as part of the normal maintenance program. Do you see the principle here?
When assessing your test equipment needs, one of the things to consider is your known failure modes. You have these from your maintenance and repair data. You may also obtain from most manufacturers information on failure modes. Once you know what kinds of failures are more likely, you want to determine what tests you can perform to see that failure coming and to identify it if it does come.
Don’t make the mistake of limiting your test equipment arsenal to some idea of generalized testing. Knock those downtime numbers down by making sure you have the test equipment to determine the condition of the equipment in your facility and to quickly troubleshoot that equipment should a failure occur.