Page 382 - Intro Predictive Maintenance

A Total-Plant Predictive Maintenance Program 373

So far, there has been no consideration of the angular positions of the usual two points
of imbalance relative to each other or the distance between the two correction planes.
For example, if the residual imbalances in each of the two planes were in-phase, they
would add to each other to create more static imbalance.

Most balancing standards are based on a residual imbalance and do not include mul-
tiplane imbalance. If they are approximately 180 degrees to each other, they form a
couple. If the distance between the planes is small, the resulting couple is small; if
the distance is large, the couple is large. A couple creates considerably more vibration
than when the two residual imbalances are in-phase. Unfortunately, nothing in the
balancing standards considers this point.

Another problem could also result in excessive imbalance-related vibration even
though the ISO standards were met. The ISO standards call for a balancing grade of
G6.3 for components such as pump impellers, normal electric armatures, and parts of
process plant machines. This results in an operating speed vibration velocity of 6.3
mm/sec. (0.25in./sec.) vibration avelocity; however, practice has shown that an
acceptable vibration velocity is 0.1in./sec. and the ISO standard of G2.5 is required.
Because of these discrepancies, changes in the recommended balancing grade are
expected in the future.

16.2.3 Motivation
Staff motivation to perform preventive maintenance properly is a critical issue. A little
extra effort in the beginning to establish an effective preventive maintenance program
will pay large dividends, but finding those additional resources when so many “fires”
need to be put out is a challenge. Like with most things we do, if we want to do it, we
can. Herzberg’s two levels of motivation, as outlined in Figure 16–5, help us under-
stand the factors that cause people to want to do some things and not be so strongly
stimulated to do others. Paying extra money, for example, is not nearly as motivating
as are demonstrated results that show equipment running better because of the preven-
tive maintenance and a good “pat on the back” from management for a job well done.

A results orientation is helpful because, as shown in Figure 16–6, an unfilled need is
the best motivator. That need, in reference to effective maintenance management,
is equipment availability and reliability, desire to avoid breakdowns, and opportunity
to achieve improvement. The converse is failures and downtime, with resulting low
production and angry customer users.

Production/Maintenance Cooperation
Some organizations, such as General Motors’ Fisher Body Plant, have established the
position of Production/Maintenance Coordinator. This person’s function is to ensure
that equipment is made available for inspections and preventive maintenance at the
best possible time for both organizations. This person is a salesman for maintenance.
This is an excellent developmental position for a foreman or supervisor. One year in