Electrical Supply Systems

DOE-HDBK-1092-98

3. Suitable NEMA rated enclosures shall be provided in those locations where water/ explosives

mixtures may contact electrical equipment and wiring.

4. Areas where explosives are processed and sublimation may occur or where flammable gases

or vapor may be present in quantities sufficient to produce explosive or ignitable mixtures

shall be regarded as Class I Division 1 and Class II Division 1 hazardous locations.

5. To ensure a location is assigned to the proper hazardous location class and division, it is

necessary to know the properties of the explosives involved there, including, at a minimum,

sensitivity to heat and spark and thermal stability. If the properties of an explosive area are

such that Class II Group G equipment provides inadequate surface temperature limits, special

protection shall be provided or the equipment excluded from the hazardous location. This

equipment shall not have a surface temperature exceeding the lowest onset of the exotherm

of the explosive as determined by the differential thermal analysis test or the differential

scanning calorimetry test. When NEC Class I or II equipment is not available, the substitute

equipment shall be purged (in accordance with NFPA 496) or sealed to prevent explosives

contamination, shall be determined intrinsically safe by facility management, or shall be

administratively controlled. If the equipment is purged, it shall be monitored for flow.

6. Areas that contain explosives that are not defined as hazardous locations (areas containing no

dust, vapor, gas hazards, or exposed explosives; for example, storage magazines), shall be

evaluated and documented by facility management to ensure that electrical ignition sources

are minimized or shall be regarded as NEC Class II.

7. Procedures shall be established by each DOE facility to control the use and modification of

electrical equipment in explosives areas and ensure that uniform standards are adhered to

throughout the facility.

5.1.5.3 ELECTRICAL SUPPLY SYSTEMS

There may be multiple hazards where explosives facilities are located near electrical supply lines.

To protect against these hazards, the NESC (ANSI/IEEE C2) and the following requirements apply

to all new construction or major modification and should be considered for existing facilities:

1. Electric lines serving explosive facilities shall be installed underground from a point not less

than 50 ft from such facilities. This also applies to communications and instrumentation lines

and security alarm systems.

2. Electric service lines required to be close to an explosives facility shall be no closer to that

facility than the length of the lines between the poles or towers supporting the lines, unless

an effective means is provided to ensure that broken, energized lines cannot come into contact

with and present a hazard to the facility or its appurtenances.

3. Unmanned electrical substations shall be no closer to explosives facilities than public traffic

route distances.

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