Intrinsically Safe and Nonincendive Systems
As a result of the efforts of ISA Comittee 8D-RP12 the 1956 edition of the National Electrical Code included for the first time a paragraph recognizing the concept of intrinsic safety. Paragraph 500–1 states, “Equipment and associated wiring approved as intrinsically safe may be installed in any hazardous location for which it is approved, and the provisions of Articles 500–517 need not apply to such installation. Intrinsically safe equipment and wiring is incapable of releasing sufficient electrical energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture. Abnormal conditions will include accidental damage to any part of the equipment or wiring, insulation or other failure of electrical components, application of over-voltage, adjustment and maintenance operations, and other similar conditions.”
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