Page 26 - An Introduction To Predictive Maintenance

16 An Introduction to Predictive Maintenance

Predictive Maintenance Is More Than Maintenance

Traditionally, predictive maintenance is used solely as a maintenance management
tool. In most cases, this use is limited to preventing unscheduled downtime and/or
catastrophic failures. Although this function is important, predictive maintenance can
provide substantially more benefits by expanding the scope or mission of the program.
As a maintenance management tool, predictive maintenance can and should be used
as a maintenance optimization tool. The program’s focus should be on eliminating
unnecessary downtime, both scheduled and unscheduled; eliminating unnecessary pre-
ventive and corrective maintenance tasks; extending the useful life of critical systems;
and reducing the total life-cycle cost of these systems.

Plant Optimization Tool. Predictive maintenance technologies can provide even more
benefit when used as a plant optimization tool. For example, these technologies can
be used to establish the best production procedures and practices for all critical pro-
duction systems within a plant. Few of today’s plants are operating within the origi-
nal design limits of their production systems. Over time, the products that these lines
produce have changed. Competitive and market pressure have demanded increasingly
higher production rates. As a result, the operating procedures that were appropriate
for the as-designed systems are no longer valid. Predictive technologies can be used
to map the actual operating conditions of these critical systems and to provide the data
needed to establish valid procedures that will meet the demand for higher production
rates without a corresponding increase in maintenance cost and reduced useful life.
Simply stated, these technologies permit plant personnel to quantify the cause-and-
effect relationship of various modes of operation. This ability to actually measure the
effect of different operating modes on the reliability and resultant maintenance costs
should provide the means to make sound business decisions.

Reliability Improvement Tool. As a reliability improvement tool, predictive mainte-
nance technologies cannot be beat. The ability to measure even slight deviations from
normal operating parameters permits appropriate plant personnel (e.g., reliability engi-
neers, maintenance planners) to plan and schedule minor adjustments that will prevent
degradation of the machine or system, thereby eliminating the need for major rebuilds
and associated downtime.

Predictive maintenance technologies are not limited to simple electromechanical
machines. These technologies can be used effectively on almost every critical system
or component within a typical plant. For example, time-domain vibration can be used
to quantify the response characteristics of valves, cylinders, linear-motion machines,
and complex systems, such as oscillators on continuous casters. In effect, this type of
predictive maintenance can be used on any machine where timing is critical.

The same is true for thermography. In addition to its traditional use as a tool to survey
roofs and building structures for leaks or heat loss, this tool can be used for a variety
of reliability-related applications. It is ideal for any system where surface temperature
indicates the system’s operating condition. The applications are almost endless, but
few plants even attempt to use infrared as a reliability tool.