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Resistors And Switches

Resistors, Switches, Runway Conductors and Extension Lamps

For the safety of crane operators and other personnel, this section, among other features, calls for crane design elements that prevent contact with runway conductors and facilitate shut-off of power to the conductors in various types of overhead cranes. To lower the risk of fires, this standard requires resistor enclosures that offer ample ventilation while providing enough protection to prevent dust and other combustible material from coming into contact with hot resistor parts.

Electric Equipment: Resistors

1.Enclosures for resistors shall have openings to provide adequate ventilation, and shall be installed to prevent the accumulation of combustible matter too near to hot parts.

2. Resistor units shall be supported so as to be as free as possible from vibration.

3.Provision shall be made to prevent broken parts or molten metal falling upon the operator or from the crane.

Switches

1. The power supply to the runway conductors shall be controlled by a switch or circuit breaker located on a fixed structure, accessible from the floor, and arranged to be locked in the open position.

2. On cab-operated cranes a switch or circuit breaker of the enclosed type, with provision for locking in the open position, shall be provided in the leads from the runway conductors. A means of opening this switch or circuit breaker shall be located within easy reach of the operator.

3. On floor-operated cranes, a switch or circuit breaker of the enclosed type, with provision for locking in the leads from the runway conductors. This disconnect shall be mounted on the bridge or footwalk near the runway collectors. One of the following types of floor-operated disconnects shall be provided:

4. Nonconductive rope attached to the main disconnect switch.

5. An undervoltage trip for the main circuit breaker operated by an emergency stop button in the pendant pushbutton in the pendant pushbutton station.

6. A main line contactor operated by a switch or pushbutton in the pendant pushbutton station.

7. The hoisting motion of all electric traveling cranes shall be provided with an overtravel limit switch in the hoisting direction.

8. All cranes using a lifting magnet shall have a magnet circuit switch of the enclosed type with provision for locking in the open position. Means for discharging the inductive load of the magnet shall be provided.

Runway conductors

1. Conductors of the open type mounted on the crane runway beams or overhead (usually in conductor box)shall be so located or so guarded that persons entering or leaving the cab or crane footwalk normally could not come into contact with them.

Extension lamps

1. Lighting is not the standard configuration for CLESCRANE. If a service receptacle is provided in the cab or on the bridge of cab-operated cranes, it shall be a grounded three-prong type permanent receptacle, not exceeding 300 volts.

Electrical hazards can lurk undetected until it’s too late.

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