Page 61 - Intro Predictive Maintenance

52 An Introduction to Predictive Maintenance

These parameters and their codes should be established to fit the needs of the specific
organization. For example, an organization with many pneumatic and optical instru-
ments would have sticky dials and dirty optics that would not concern an electroni-
cally oriented organization. Note also that the code letters are the same, whenever
possible, as the commonly used word’s first letters. Preventive maintenance activities
are recorded simply as PM/PM/PM. The cause codes, which may be more detailed,
can use numbers and subsets of major groups, such as all power will be 20s, with
external input power = 21, main power supply = 22, and so on.

It is possible, of course, to write out the complete words; however, analysis—whether
done by computer or manually—requires standard terms. Short letter and number
codes strike a balance that aids short reports and rapid data entry.

Use of the equipment at every failure should also be recorded. A key to condition-
monitoring preventive maintenance effectiveness is knowing how many hours, miles,
gallons, activations, or other kind of use have occurred before an item failed. This
requires hour meters and similar instrumentation on major equipment. Use on related
equipment may often be determined by its relationship to the parent. For example, it
may be determined that if a specific production line is operating for seven hours, then
the input feeder operates five hours (5/7), the mixer two hours (2/7), and the packag-
ing machine four hours (4/7).

It is also important to determine the valid relationship between the cause of the
problem and the recording measurement. For example, failures of an automotive
starter are directly related to the number of times the car engine is started and only
indirectly to odometer miles. If startup or a particular activity stresses the equipment
different from normal use, then those special activities should be recorded.

Figure 3–3 is a combination work order and completion form. This form is printed by
the computer on plain paper with the details of the work order on the top, space in the
center for labor and materials for work orders that take a day or less, and a completion
blank at the bottom to show when the work was started, when it was completed, the
problem/cause/action codes, and meter reading. Labor on work orders that take more
than one day is added daily from time reports and accumulated against the work order.
Figure 3–4 shows the computer input screen for a simple service call report form that
gathers the minimum information necessary for field reporting. Those forms may be
used as input for a computer system, when a direct-entry system is not available.

3.3.2 Improving Equipment Reliability
Total-plant performance management (TPPM) and similar quality programs promote
a holistic approach that includes equipment performance as a major enhancement to
productivity. To reinforce the five-fingered approach to effective maintenance outlined
previously, the fundamental thumb is elimination of failures. Uptime of equipment is
what counts. Maintainability and maintenance are most successful if we do not have
failures to fix.