Quantcast Normal Terminal Stopping Switches

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4.3.9 Slack-Rope Device
Slack-rope devices are required only for winding-drum machines. The device is arranged to
monitor the loss of tension in the hoistway ropes. Most are located at the hoist rope termination,
(See Figure 4-14) however, some devices are located at the hoist machine. Electric switches
used with slack-rope devices should be of the enclosed, manually reset type and should be tested
by tripping the device by hand with the machine running. This should stop the car. Where the
slack-rope device cannot be operated by hand, test at intervals of not longer than 12 months by
lowering the car onto a suitable support or supports placed in the pit. Determine that the tension
in the hoisting ropes decreases sufficiently to operate the device and stop the machine.
Determine that there is no interference with the free and complete movement of the slack-rope
device for the hoisting ropes and the detector bars are set as close as possible to the
driving-machine drum in order to open the switch with a minimum of slack rope.
4.3.10 Normal Terminal Stopping Switches
In some cases, the normal terminal stopping switches are located in the machine room and
operated by a rope, tape, or chain attached to the car. These switches should be examined as
previously outlined.
4.3.11 Gears And Bearings
4.3.11.1 Inspection Made with Power On. Close the mainline switch and proceed. Have the
dumbwaiter operated in each direction, making frequent stops. observe if there is any excessive
play or 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 sound and/or heat. Examine all bearings and gears for excessive lost motion or wear.
Determine whether bearings and gears are lubricated and that oil rings, chains, or other methods
of feeding, operate freely. The level of oil in the reservoirs should be checked -and any leakage
of oil noted.
4.3.11.2 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 break down 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.
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