Grounding - hdbk10920118

DOE-HDBK-1092-98

6.2.3 GROUNDING

NEC grounding requirements consider the crane or hoist with all its associated equipment, including

electrical equipment, as a single piece of equipment; therefore, all the conductive component parts

shall be bonded together so that the entire crane or hoist is grounded in compliance with NEC Article

250, Part G, and NEC Section 610-61. Metal-to-metal contact is required between all surfaces

including the trolley wheels and bridge. If any such surfaces are painted or otherwise insulated, a

separate bonding conductor is required.

The bonding of all conductive surfaces by metal-to-metal contact is not to be considered as the

equipment grounding conductor for the electrical equipment (motors, motor controllers, lighting

fixtures, transformers, etc.)on the crane or hoist. The equipment ground conductors that are run with

the circuit conductors shall comply with NEC Section 250-91(b).

6.2.4 CONTROL

A limit switch is required to prevent the load block from passing the safe upper travel limit on all

hoisting mechanisms per NEC Section 610-55.

6.2.5 CLEARANCES

In the direction of live parts, the working space clearance is 2-1/2 ft, and doors enclosing live parts

that may require service or maintenance shall open at least 90 degrees or be removable per NEC

Section 610-57.

6.2.6 OSHA AND NEC REQUIREMENTS

29 CFR 1910.179 and NEC Article 610, Part F, provide additional electrical requirements derived

from ANSI and other standards. Significant requirements are the following:

1. Control circuit voltage shall not exceed 600 Vac or dc. Pendant pushbutton voltage shall not

exceed 150 Vac or 300 Vdc.

2. Support shall be provided for pendant multiconductor cables.

3. Electrical systems for cranes and hoists shall provide failsafe operation. When power fails, all

motors shall be automatically disconnected so that they will not resume operation when the

power comes back on. Automatic cranes shall not commence motion automatically when the

power comes on after an outage. Pendant pushbuttons shall be returned to the off position

when pressure is released. When the signal from a remote controller fails, all motion shall stop.

6.2.7 MAINTENANCE AND OPERATIONS

It is important to have a comprehensive electrical maintenance program for cranes and hoists. Every

electrical part and circuit plays a critical operational safety role and must be checked and serviced

at the frequency and in the manner specified by OSHA, CMAA, ANSI, and the manufacturer's

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