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What are the
hazards?
With the wide use of portable tools on construction sites, the use of flexible
cords often becomes necessary. Hazards are created when cords, cord connectors,
receptacles, and cord- and plug-connected equipment are improperly used and
maintained.
Generally, flexible cords are more vulnerable to damage than is fixed wiring.
Flexible cords must be connected to devices and to fittings so as to prevent
tension at joints and terminal screws. Because a cord is exposed, flexible, and
unsecured, joints and terminals become more vulnerable. Flexible cord conductors
are finely stranded for flexibility, but the strands of one conductor may loosen
from under terminal screws and touch another conductor, especially if the cord
is subjected to stress or strain.
A flexible cord may be damaged by activities on the job, by door or window
edges, by staples or fastenings, by abrasion from adjacent materials, or simply
by aging. If the electrical conductors become exposed, there is a danger of
shocks, burns, or fire. A frequent hazard on a construction site is a cord
assembly with improperly connected terminals.
When a cord connector is wet, hazardous leakage can occur to the equipment
grounding conductor and to humans who pick up that connector if they also
provide a path to ground. Such leakage is not limited to the face of the
connector but also develops at any wetted portion of it.
When the leakage current of tools is below 1 ampere, and the grounding conductor
has a low resistance, no shock should be perceived. However, should the
resistance of the equipment grounding conductor increase, the current through
the body also will increase. Thus, if the resistance of the equipment grounding
conductor is significantly greater than 1 ohm, tools with even small leakages
become hazardous.
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