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(a) Type of Driving Machines.
Driving machines shall be powered by electric or hydraulic motors. Hydraulic units, where used shall be electrically driven. The hydraulic drive shall consist of an oil storage tank, a hydraulic pump and a hydraulic motor brake and shall conform to the following requirements:
(1) Valves, piping and fittings shall not be subjected to working pressures exceeding those recommended by the manufacturer for the type of service for which they are used.
(2) Piping shall be so supported as to eliminate undue stresses at joints and fittings, particularly at any section of the line subject to vibration.
(3) Flexible connections shall--where installed in high pressure lines--have a bursting strength of not less than three times the working pressure. Flexible joints may be used in hydraulic lines connecting control or check valves to the motor provided the failure of the flexible sealing element shall not permit separation of the parts connected.
(4) Each pump or group of pumps shall be equipped with a relief valve conforming to the following requirements:
(A) The relief valve shall be located between the pump and the check valve and shall be of such a type and so installed in a bypass connection that the valve cannot be shutoff from the hydraulic system.
(B) The relief valve shall be preset to open at a pressure not greater than 125 percent of the working pressure at the pump.
(C) The size of the relief valve and bypass shall be sufficient to pass the maximum rated capacity of the pump without raising the pressure more than 20 percent above that at which the valve opens. Two or more relief valves may be used to obtain the required capacity.
(D) Relief valves having exposed pressure adjustments, if used, shall have their means of adjustment sealed after being set to the correct pressure.
(5) An electric interlock shall be provided to prevent the start or the movement of the hoist car unless the pump operates at the normal operating speed and pressure.
(6) The brake shall remain in applied position until the pump operates at the normal operating speed and pressure and the movement of the hoist car is initiated.
(7) All components of the hydraulic system shall be shielded.
(b) Winding Drums.
Winding-drum machines may be used irrespective of car travel provided that the drums are grooved for hoisting wire rope. Grooves shall be machine-finished and shall be of the helical or parallel type.
If drums are equipped with helical grooving, only one layer of rope shall be permitted on the drum. If drums are equipped with parallel grooving, (LeBus System, or the equivalent) more than one, but not more than four, layers of rope shall be permitted on the drum.
(c) Car Speed.
The car speed for all drives shall not exceed 600 feet per minute.
(d) Diameter of Drums and Sheaves.
Driving sheaves and drums shall have a pitch diameter of not less than forty times the diameter of the hoisting wire rope. Overhead and deflector sheaves shall have a diameter of not less than thirty times the rope diameter.
EXCEPTION: Where 8 x 19 wire hoist rope is used on machines existing at the time of the effective date of these Orders, sheaves and drums may have a diameter of not less than 32 times the rope diameter.
(e) Worms and Worm Gears.
Worms and worm gears, where used in the drive machine, shall be of steel and bronze, respectively.
(1) Helical or parallel drives must run in oil.
(f) Friction Gearing and Clutches.
Friction gearing or clutch mechanisms shall be prohibited.
The driving machine shall be equipped with a friction brake applied by a spring or by gravity and released electrically or hydraulically. The brake shall be designed to have a capacity sufficient to stop and hold the car at rest at 125% of its rated load.
(h) Rack and Pinion Drive.
The rack and pinion drive shall consist of one or more power-driven rotating pinions mounted on the car and arranged to travel on a stationary vertical rack mounted on the hoist structure. The drive shall have at least one pinion, one rack, and two backup rollers. The pinions and rack shall be of steel and shall comply with the following standards of the American Gear Manufacturing Association: AGMA 210.22, AGMA 220.02, and AGMA 240.01. Driving machines located within the car shall be fully enclosed with solid or open metal and if in a cabinet, the cabinet shall be locked.
(i) Factors of Safety.
The factor of safety to be used in the design of driving machines and in the design of sheaves used with hoisting and compensating ropes shall be not less than the following:
(1) Eight for steel, bronze, or for other metals having an elongation of at least 14% in a length of 2 inches.
(2) Ten for cast iron, or for other metals having an elongation of less than 14% in a length of 2 inches.
The load to be used in determining the factor of safety shall be the resultant of the maximum tensions in the ropes leading from the sheave or drum with car at rest and with rated load in the car.