Page 219 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Maintenance record
Maintaining a system of inspection records is a must in preventive maintenance schedule. This system uses
a register as stated above or cards as shown below which are kept in the master file. By referring to these
maintenance cards, the foreman can schedule the planned maintenance.
Maintenance card: The 1st page gives initial test results etc pertaining to the machine.
A careful study of the maintenance card helps the foreman to plan the shut-down date to facilitate early overhauling
or planned maintenance schedule to prevent a major breakdown.
Method of maintenance: During the routine maintenance inspection, the investigations and adjustment to be
carried out for the parts and accessories of the motors/generators are given below to improve the efficiency of
preventive maintenance.
• Clean daily the motor/generator, switch gear and associated cables free from dirt, dust and grease. Use dry
compressed air to drive away the dust from the machines.
• Check the bearing daily for excessive noise and temperature. If required, re-grease or re-oil the bearing with
the same grade of grease/oil as in original. Do not mix different grades of grease together as it may result in
forming sludge or acids, and spoil the bearings.
• Check the machine daily against strains of water or oil or grease which may leak from the surroundings. Take
the necessary protective steps to prevent the leakage.
• Check daily the belts, gears and coupling for looseness, vibration and noise. Adjust/replace the parts, if found
defective.
• Check weekly the brushes and the commutator for sparking and wear.
• Check weekly the bearing for proper lubrication.
• Check weekly the terminals and switch contacts.

• Inspect the brushes and the commutator once in a month for excessive wear, chatter and sparking. Worn-out
brushes need to be replaced with the same grade brushes. Check spring tension on the brushes, and adjust,
if necessary. Badly worn-out commutators need to be turned in a lathe or be replaced.
• Check monthly the brushes for proper seating. If necessary, reshape the brushes to proper curvature to suit
the commutator surface.

• Check monthly the end plates and the shaft for excessive end play.
• Check monthly the main and auxiliary contact points of the switch gear for wear, pitting and burns. Badly worn
out contact point needs replacement. Check the connection terminals for loose connection and scales or
burning. Rectify the defects.
• Test monthly once the field windings and armature for insulation and ground faults. Low reading of insulation
below 1 megohm indicates weak insulation. Dry out the winding, and re-varnish, if necessary.
• Check monthly once the foundation bolt and other fasteners for tightness.
• Once a year undercut the mica in between the commutator bars. Test the commutator and armature for shorts,
open and ground faults.

206

CITS : Power - Electrician & Wireman - Lesson 30-37