2.4.11.1
Hoist Upper Limit-Switches
Two limit-switches shall be provided for each hoist. A rotating-type
adjustable geared-control circuit interrupt limit-switch shall provide
hoist-up limiting. A secondary hoist-upper-limit shall be provided with a
weight-operated power circuit limit-switch to prevent the hoist from
raising beyond the safe limit. The secondary limit-switch shall operate to
interrupt power to all hoist motor conductors, set the hoist holding brakes
and directly open all "raise" power circuits. [A power bypass contactor
and operator button to permit backing out and resetting of power
limit-switch shall be provided for ac adjustable frequency control.] [A
power bypass contactor and operator button to permit backing out and
resetting of power limit-switch shall be provided for dc variable-voltage
control.]
2.4.11.2
Hoist Lower Limit-Switches
Hoists shall be provided with a rotating-type adjustable geared-control
circuit interrupt limit-switch for hoist-down travel limiting. The hook
downward vertical travel of the hook shall be field-adjustable to
approximately 150 mm 6 inches above working surface.
2.4.11.3
Bridge and Trolley Travel Limit-Switches
Runway (track-type) limit-switches shall be provided for crane bridge and
trolley motions to stop the bridge and trolley motions, respectively.
Limit-switch actuators shall be installed on building and trolley frame to
actuate the limit-switches and stop the crane bridge or trolley prior to
contacting the trolley frame bumpers. Trip mechanism for trolley motion
shall be located on crane runway to trip the switch before the bumper
contacts the stop. Trip mechanism for bridge motion shall be located on
crane runway to trip switch before bumper contacts the stop. When the
switch is tripped, the switch shall permit opposite travel in the direction
of stop and then automatically reset.
2.4.11.4
Rail Clamp Limit-Switches
**************************************************************************
NOTE: Include paragraph for outdoor cranes;
otherwise delete. Delete reference to micro-drive
when not applicable.
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When rail clamps are set, each rail clamp shall be furnished with a
limit-switch designed to interrupt the primary and micro-drive control
circuits to bridge drive. A red pilot light shall be provided at control
station to indicate the rail clamps are set.
2.4.12
Wiring
Wiring shall comply with Article 610 of NFPA 70. Wires shall be numbered
or tagged at connection points. Splices shall be made in boxes or panels
on terminals boards or standoff insulators. Motor loop, branch circuit and
brake conductor selection shall be based on NFPA 70 for 90 degree C
conductor rating on indoor cranes, and for 75 degree C conductor rating on
outdoor cranes. Conductors in the vicinity of resistors and conductors
connected to resistors shall be Type 5RML.
SECTION 14630A
Page 44
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