Section 2.24 Driving Machines and Sheaves
(a) They shall not be provided with counterweights.
(c) The travel of the elevator car shall not exceed 12.5m (40 ft).
(a) 40 times the diameter of steel wire rope where used for suspension ropes
(b) 40 times the cord diameter (see ASME A17.6, 126.96.36.199.1) of noncircular elastomeric-coated steel suspension members where used for suspension
(c) 16 times the functional diameter (see ASME A17.6, 188.8.131.52.2) of the load-carrying fibers of aramid ropes where used for suspension or compensation
(d) 32 times the diameter of steel wire ropes and the cord diameter of noncircular elastomeric-coated steel suspension members where used for compensation
(a) the suspension members shall slip on the drive sheave and not allow the car or counterweight to be raised
(b) the driving system shall stall and not allow the car or counterweight to be raised
- The percent counterweight overbalance is the percentage of an elevator's rated capacity that the counterweight is heavier than the car.
- The percent counterweight overbalance range refers to the upper and lower limits, expressed as a percentage of the elevator's rated capacity, that the counterweight is heavier than the car.
(a) 8 for metals having an elongation of at least 14% in a gauge length of 50 mm (2 in.) when tested in accordance with ASTM E8.
(b) 10 for cast iron or for metals having an elongation of less than 14% in a gauge length of 50 mm (2 in.) when tested in accordance with ASTM E8.
(c) 10 for sheaves of plastic, fiber-reinforced plastic, or combinations thereof. The material used shall ensure that the factor of safety is not less than 8 during the service life of the sheave.
The load to be used in determining the factor of safety shall be the resultant of the maximum tensions in the suspension means leading from the sheave or drum with the elevator at rest and with the rated load in the car.
Driving-machine components including bedplate, where used, subject to forces due to the application of the emergency brake (see 2.19.4) shall be designed to withstand the maximum forces developed during the retardation phase of emergency braking so that the factor of safety resulting from the emergency braking and all other loading acting simultaneously, if applicable, shall be not less than specified in 2.24.3(a) and 2.24.3(b).
Shafts that support drums, sheaves, gears, couplings, and other members, and that transmit torque, shall be provided with tight-fitting keys.
Friction gearing or a clutch mechanism shall not be used to connect a driving-machine drum or sheave to the main driving mechanism.
(b) holding the empty car at rest.
(c) decelerating the empty car traveling in the up direction from the speed at which the governor overspeed switch is set. Any deceleration not exceeding 9.8 m/s2 (32.2 ft/s2) is acceptable, provided that all factors such as, but not limited to, system heat dissipation and allowable buffer striking speeds are considered.