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ANSI and CMAA standards should be carefully reviewed to ensure that all applicable safety
requirements are covered in the specifications.
The designer should specify the following requirements:
1.
Available system voltage
2. Control voltage
3. The motor is constructed for the specific application
4. Motor horsepower, service factor, insulation class, and time ratings are sufficient to meet the
load requirements
5. Working clearances and space requirements
6. Disconnecting means and other NEC requirements.
6.2 CRANES AND HOISTS
The most significant factor in crane and hoist safety, after structural integrity, is electrical safety. All
the referenced standards support this fact either directly or indirectly by the amount of definition and
space provided for electrical systems' controls, operations, and maintenance.
6.2.1 NEC GENERAL REQUIREMENTS
Basic installation and wiring safety requirements for cranes and hoists are given in NEC Article 6101.
Electrical designers and maintenance personnel should thoroughly understand these requirements
and their intent. Some of the more significant requirements are the following:
1. Cranes and hoists operated in hazardous (classified) locations shall conform to NEC Article
500.
2. When the crane is operated above readily combustible materials, the resistors must be located
in a well-ventilated cabinet constructed of noncombustible material and constructed so that
they will not emit flames or molten metal. See the exception (and requirements) that applies
to certain cabinets made of noncombustible materials.
3. Cranes and hoists operating on electrolytic cell lines have special requirements, as given in
NEC Section 668-32.
a. Grounding is not required for conductive surfaces of cranes and hoists that enter the
working zone of a cell line, and the parts that come in contact with an energized cell or
attachments shall be insulated from ground.
1
See Appendix D, Reference Matrix.
6-3
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