Page 275 - Intro Predictive Maintenance

266 An Introduction to Predictive Maintenance

When the filter is operating efficiently, air pushing on the entry side will be only
slightly impeded and will have about the same pressure on the exit side. A small
colored ball that fits inside the clear manometer tube will rest in the bottom when the
airflow is balanced. As the filter becomes restricted, pressure on the entry will be
greater than on the exit and the ball will be pushed to the exit side of the tube. Colored
bands around the tube can indicate the threshold of safety versus a need to replace the
filter.

Because it will normally take at least several days and probably weeks for the filter
to become clogged, the manometer can be checked on a routine inspection schedule
and then maintenance can be performed as conditions require. This schedule is cer-
tainly less expensive for both labor and materials than either routinely replacing the
filter, whether it needs it or not, or letting it build up until equipment fails and both
temperatures and tempers rise. More sophisticated sensors are certainly required where
humans cannot or will not notice them, as well as remote communications and alarm
systems.

The decision to put or not to put a filter in the airflow is a good example of initial
investment in preventive maintenance that will pay off over the equipment life. Equip-
ment would operate just fine initially without any filter and would, of course, cost less
without those components; however, when contaminants build up on an electronic
circuit board, coil, or fan, extensive and expensive cleaning will have to be done to
prevent the equipment from failing. Changing the filter is much easier than major
equipment refurbishing, and the initial cost and replacement filters pay off through
improved performance. As the automotive oil-filter advertising campaign said: “You
can pay a little now, or a lot later.”