HOISTS & CRANES
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Brakes for trolleys and bridges—a key to safe overhead crane operation—require specific design features to promote effective, reliable operation. This section lays out the function and performance requirements for crane brakes, as well as acceptable options for brake application.
This section also covers ergonomic considerations to help assure proper operation of equipment; for instance, a limit on the force required to apply a foot-operated brake.
Control braking means
1．A power control braking means such as regenerative, dynamic or counter-torque braking, or a mechanically controlled braking means shall be capable of maintaining safe lowering speeds of rated loads. frequency of operating required by service.
Brakes for trolleys and bridges
1. Foot-operated brakes shall not require an applied force of more than 70 pounds to develop manufacturer's rated brake torque.
2. Brakes may be applied by mechanical, electrical, pneumatic, hydraulic, or gravity means.
3. Where necessary brakes shall be provided with adjustment means to compensate for wear.
4. The wearing surface of all brake drums or discs shall be smooth.
5. All foot-brake pedals shall be constructed so that the operator's foot will not easily slip off the pedal.
6. Foot-operated brakes shall be equipped with automatic means for positive release when pressure is released from the pedal.
7. Brakes for stopping the motion of the trolley or bridge shall be of sufficient size to stop the trolley or bridge within a distance in feet equal to 10 percent of full load speed in feet per minute when traveling at full speed with full load.
8. If holding brakes are provided on the bridge or trolleys, they shall not prohibit the use of a drift point in the control circuit.
9. Brakes on trolleys and bridges shall have ample thermal capacity for the frequency of operation required by the service to prevent impairment of functions from overheating.
Application for trolley brakes
1. On cab-operated crane with cab on trolley, a trolley brake shall be required as specified
2. A drag brake may be applied to hold the trolley in a desired position on the bridge and to eliminate creep with the power off.
Application of bridge brakes
1. On cab-operated cranes with cab on bridge, a bridge brake is required as specified.
2. On cab-operated cranes with cab on trolley, a bridge brake of the holding type shall be required.
3. On all floor, remote and pulpit-operated crane bridge drives, a brake of noncoasting mechanical drive shall be provided.