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Electrical equipment for use in class 1 hazardous (classified) locations,
as defined in the National Electric Code, is tested with respect to
acceptability of the operation in the presence of flammable and explosive
mixtures of specific vapors and gases with air. For purposes of area
classification , such mixtures have been grouped on the basis of their
characteristics as follows: |
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Class
1, Group B - |
Atmospheres
such as acolein (inhibited), butadiene, ethylene oxide, hydrogen
(or gases or vapors equivalent in hazard to hydrogen gas), or propylene
oxide.
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The
National Fire Protection Association (NFPA) determine safe practices
and establish standards for all areas of commercial, industrial and
residential construction. They publish many documents including NFPA
code 70 - better known as the National Electric Code, and NFPA 496
- the document that outlines the practices for purging the motors
and controls that Dietz offers. |
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NATIONAL ELECTRIC CODE 501-8(b) MOTORS AND GENERATORS
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(a)
Class 1, Division 1. In Class 1 Division 1 locations, motors,
generators and other rotating electrical machinery shall be:
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(1)
Approved for Class 1, Division 1 locations. Note: (Approval
authorities such as Underwriters Laboratories, and Factory Mutual
Research do not offer standards on Class 1, Group B, Division
1, electric motors.
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(2)
Of the totally enclosed type motors supplied with positive pressure
ventilation from a source of clean air with discharge to a safe
area so arranged to prevent energizing of the machine until
ventilation has been established and the enclosure has been
purged with at least 10 volumes of air and also arranged to
automatically de-energize the equipment when the air supply
fails.
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Totally enclosed
motors of Type (2) shall have no external surface with an operating
temperature in degrees Celsius in excess of 80 percent of the ignition
temperature of the gas or vapor involved. Appropriate devices shall
be provided to detect and automatically increase in temperature
of the motor beyond designed limits. Auxiliary equipment shall be
of a type approved for the location in which it is installed. The
motors offered by DIETZ ELECTRIC Co., INC. are Type (2) motors constructed
to the requirements of Class 1, Group D, Division 1. They are then
modified to accept purge fittings, supplied as a complete assembly
with a purging system which complies with: NFPA Code 496 Type
“X” which reduces the classification within the enclosure from Division
1, to non-hazardous.
Acceptance of our system is subject to approval by
the authority having jurisdiction on the installation.
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Standards
& Certifying Bodies
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