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 backlash in the bearings or gearing unusual noise or play is usually an indication of gear or thrust
trouble, or damage to bearing liners, rollers, or balls. Bearing problems are also detected by
operate freely. The level of oil in the reservoirs should be checked and any leakage of oil noted.
9.6.12.2 Inspection Made with Power Off. Open the mainline switch and proceed. Examine the
oil in the gear case to determine whether it is free of metallic particles or other foreign
substances. Check the oil level. Visually check the gear for excessive wear. Gear problems are
detected by examining the wear pattern on the gear. This will show that the gear is not properly
aligned with the worm, causing the point of contact to be not in the proper position or that the
gear is bottoming or contacting the worm shaft. Excessive heat damage, most likely caused by
low oil or breakdown of oil, can also be detected. It is indicated by pock marks in the face of the
gear tooth or teeth. They resemble casting defect marks.
9.6.13 Driving-Machine Motor
9.6.13.1 Inspection Made with Power on. Close the mainline switch and proceed. Have the
hoist operated in each direction, making frequent stops, and observe the operation of the motor
and brake. Commutators or slip rings, where provided, should be observed for excessive
sparking or brush chatter. Inspect bearings as previously described. Inspect all motor fastening
bolts to determine whether they are in place and tight.
9.6.13.2 Inspection Made with Power Off. Open the mainline switch and examine brush
holders, commutators or slip rings. Determine the condition of the brush holders and brushes
and whether any brush is stuck in its holder or is worn to the extent that either brush holder or the
metal connector on the brush could touch the commutator or slip ring. If sparking or chattering
was noticed when the machine was running, check the brush spring pressure. Examine the
commutator or slip rings to determine if they are burned, pitted, grooved, or scored, and are clean
and free from oil. Also check the commutators for high mica conditions. Become very familiar
with these signs and be constantly on the lookout for them. Hoist performance is directly related
to good electrical continuity through the commutator or slip rings. Check the slots of the
commutator for any accumulation of carbon, copper dust, oil, or other substances. Check
exposed armature and field terminal connection to see that they are tight. Special attention
should be given to the shunt field connections of DC motors. Loose connections here could
result in a runaway condition. Connections not properly made may result in poor electrical
conduction and points of resistance. This condition creates heat. Examine the leads to be sure
they are not broken or their insulation is not cracked or broken. Improper adjustments can force
motor winding to carry more current, which produces heat, which will cause insulation to
deteriorate. Check to see that the motor windings are free of oil, dust, or lint deposits.
Accumulations restrict cooling air circulation, causing heat build-ups, which result in poor
performance, insulation damage, and possibly fire.
9-13
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