Page 365 - Intro Predictive Maintenance

356 An Introduction to Predictive Maintenance

directly monitor, using a current loop tester, the electrical condition of motors. By
acquiring data directly from the power cable or an electric motor and monitoring the
motor’s slip frequency, defects such as loose or broken rotor bars can be detected.

Few of the commercially available vibration-based predictive maintenance systems
provide all of the required capabilities, but they do exist. Caution should be exercised
in this selection process. A mistake can guarantee failure of any predictive mainte-
nance program.

16.2 PREDICTIVE IS NOT ENOUGH
As a subset of preventive maintenance, predictive maintenance alone cannot improve
plant performance. Because the only output of an effective predictive maintenance
program is information, the capability to directly change performance levels is nil.
Until the information is used to correct anomalies identified by using predictive
technologies, nothing will change. Therefore, an effective preventive maintenance
program must also exist. At a minimum, the overall maintenance management
methods must include effective planning and scheduling, preventive maintenance
tasks, motivations, and record keeping.

16.2.1 Effective Planning and Scheduling
The plant or facility must have an effective maintenance planning and schedul-
ing function that incorporates the information provided by the predictive main-
tenance activity into a global plan that will provide effective maintenance for all
critical plant equipment and systems. The purposes of the maintenance planning func-
tion are to:

• Create an area of improved management planning coupled with greater flex-
ibility of the in-facility workforce in conjunction with other departments.
• Obtain the maintenance and equipment efficiency and profitability neces-
sary to operate the enterprise, and simultaneously achieve the workers’
desire for security.

Planning is not a natural function to most people because it is contemplative and non-
action-oriented. The person determined to start a job, complete it on time, and estab-
lish a good record for him or herself will probably not plan unless he or she is
particularly experienced or astute, or unless some discipline is imposed. Without a
work plan, however, good maintenance is impossible. Because the natural inclination
of most people is not to plan at all, or to spend as little time planning as possible, it
is difficult to plan excessively.

The major planning failure is to plan at the beginning of a job and then neglect to
update the plan as work progresses, so that a major portion of control is lost. Some
facilities spend about 6 percent of their sales dollars on maintenance and repair. As