Specifications

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15. MAINTENANCE OF ROTATING MACHINES
15.1 Introduction
The key to minimizing motor problems is scheduled routine inspection and maintenance.
The frequency of routine maintenance varies widely between applications. Including the motors
in the maintenance schedule for the driven machine or general plant equipment is usually
sufficient. A motor may require additional or more frequent attention if a breakdown would cause
health or safety problems, severe loss of production, damage to expensive equipment or other
serious losses.
Written records indicating date, items inspected, service performed and motor condition
are important to an effective routine maintenance program. From such records, specific problems
in each application can be identified and solved routinely to avoid breakdowns and production
losses. The routine inspection and servicing can generally be done without disconnecting or
disassembling the motor.
All types of rotating machinery require regular inspections so to maintain their integrity and
availability. The maintenance becomes simple and effective with the use of minor and major
inspections categorized into levels representing the life of the product, be it running hours or
years of installation. For each level, a defined number of inspection points are determined which
can be undertaken within a specified time. The aim is not to lengthen the outages but to provide
an effective solution that can be accommodated within planned maintenance periods and provide
expert support when returning the equipment back on line.
15.2 Types of Maintenance
Breakdown maintenance : Breakdown maintenance is basically the “run it till it breaks”
type of maintenance mode. No actions or efforts are taken to maintain the equipment till its
design life is reached. Advantages are, Low cost, Less staff. Disadvantages are: Increased
cost due to unplanned downtime of equipment. Increased labor cost, especially if overtime is
needed. Cost involved in repair or replacement of equipment. Possible secondary equipment or
process, damage from equipment failure, inefficient use of staff.
Preventive maintenance: It is a daily maintenance procedure (cleaning, inspection, oiling and
re-tightening), designed to retain the healthy condition of equipment and prevent failure through
the prevention of deterioration, periodic inspection or equipment condition diagnosis by measuring
deterioration. Just like human life is extended by preventive medicine, the equipment service life
can be prolonged by doing preventive maintenance.
It is further divided into Periodic maintenance and Predictive maintenance.
a) Periodic maintenance ( Time based maintenance - TBM) : Time based maintenance
consists of periodically (at pre-determined intervals) inspecting, servicing and cleaning equipment
and replacing parts to prevent sudden failure and process problems.
b) Predictive maintenance: This is a method in which the service life of important part is
predicted based on inspection or diagnosis, (for Ex., by testing the condition of the lubricating oil
in a vehicle for its actual condition and lubrication properties in a good testing centre instead of