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 manual. Required weekly, monthly, and semiannual tests and required recordkeeping are contained in ANSI B-30 and CMAA documents.

The basic references for safe operation and maintenance of cranes and hoists are contained in the following sections of 29 CFR 1910 and 1926.

1. 29 CFR 1910.179, Overhead and Gantry Cranes, which addresses operations and maintenance requirements

2. 29 CFR 1910.306, Specific Purpose Equipment and Installations, which address electrical installation requirements

3. 29 CFR 1926.550 and 29 CFR 1926.554, which address construction site operations.

6.2.8 DOCUMENTED MAINTENANCE

Maintenance checklists and schedules in compliance with OSHA, the owner's manuals, and the manufacturer's requirements for the specific equipment shall be provided as required. Weekly, monthly, and semiannual inspections shall be conducted, and comments and condition of the inspected part shall be documented and certified as required by 29 CFR 1910.179.

The recommended frequencies of inspections vary in accordance with application, usage, and authority. Frequent inspection and periodic inspection are defined by OSHA as daily to monthly and 1 to 12 months, respectively. Typical inspection frequencies for electrical equipment of cranes and hoists are as follows:

The inspection records shall provide an ongoing safety assessment of the equipment and be used to predict repair-part replacement. All inspections shall be dated and initialed by the inspector.