Page 57 - Intro Predictive Maintenance

48 An Introduction to Predictive Maintenance

Advantages and Disadvantages

Overall, preventive maintenance has many advantages. It is beneficial, however, to
overview the advantages and disadvantages so that the positive may be increased
and the negative reduced. Note that in most cases the advantages and disadvantages
vary with the type of preventive maintenance tasks and techniques used. Use of on-
condition or condition-monitoring techniques is usually better than fixed intervals.

Advantages. There are distinct advantages to preventive maintenance management.
The predominant advantages include the following:

• Management control. Unlike repair maintenance, which must react to
failures, preventive maintenance can be planned. This means “pre-active”
instead of “reactive” management. Workloads may be scheduled so that
equipment is available for preventive activities at reasonable times.
• Overtime. Overtime can be reduced or eliminated. Surprises are reduced.
Work can be performed when convenient; however, proper distribution of
the time-driven preventive maintenance tasks is required to ensure that all
work is completed in a timely manner without excessive overtime.
• Parts inventories. Because the preventive maintenance approach permits
planning of which parts are going to be required and when, those material
requirements may be anticipated to be sure they are on hand for the event.
A smaller stock of parts is required in organizations that emphasize pre-
ventive tasks compared to the stocks necessary to cover breakdowns that
would occur when preventive maintenance is not emphasized.
• Standby equipment. With high demand for production and low equipment
availability, reserve, standby equipment is often required in case of break-
downs. Some backup may still be required with preventive maintenance, but
the need and investment will certainly be reduced.
• Safety and pollution. If no preventive inspections or built-in detection
devices are used, equipment can deteriorate to a point where it is unsafe or
may spew forth pollutants. Performance will generally follow a saw-tooth
pattern, as shown in Figure 3–2, which does well after maintenance and then
degrades until the failure is noticed and it is brought back up to a high level.
A good detection system catches degrading performance before it reaches
too low a level.
• Quality. For the same general reasons discussed previously, good preven-
tive maintenance helps ensure quality output. Tolerances are maintained
within control limits. Naturally, productivity is improved and the investment
in preventive maintenance pays off with increased revenues.
• Support to users. If properly publicized, preventive tasks help show equip-
ment operators, production managers, and other equipment users that the
maintenance function is striving to provide a high level of support. Note
here that an effective program must be published so that everyone involved
understands the value of performed tasks, the investment required, and their
own roles in the system.