Type 8 enclosures are designed for indoor or outdoor use in locations classified as Class I Groups A, B, C, or D as defined in the NEC.

5.8.1 DESCRIPTION AND APPLICATION

Type 8 enclosures and enclosed devices are arranged such that all arcing contacts, connections, and any parts that could cause arcing are immersed in oil. Arcing is confined under the oil such that it will not ignite an explosive mixture of the specified gases in internal spaces above the oil or in the atmosphere surrounding the enclosure. Enclosed heat-generating devices shall not cause external surfaces to reach temperatures capable of igniting explosive gas-air mixtures in the surrounding atmosphere. Enclosures shall meet operation and temperature-design tests. Enclosures intended for outdoor use shall also meet the rain test (See #4 in Section 5.8.2).

5.8.2 FEATURES AND TEST CRITERIA

When completely and properly installed, Type 8 enclosures:

1. Provide, by oil immersion, a degree of protection to a hazardous gas environment from operation of internal equipment

2. Do not develop surface temperatures that exceed prescribed limits for the specific gas corresponding to the atmospheres for which the enclosure is intended when internal equipment is at rated load

3. Withstand a series of operation design tests with oil levels arbitrarily reduced and with flammable gas-air mixtures introduced above the oil

4. When intended for installation outdoors, exclude water when subjected to a water spray design test simulating a beating rain

5. Are marked with the appropriate class and groups for which they have been qualified.

5.9 TYPE 9 ENCLOSURES

Type 9 enclosures are designed for indoor use in locations classified as Class 11 Groups E or G as defined in the NEC.

5.9.1 DESCRIPTION AND APPLICATION

Type 9 enclosures shall prevent the entrance of dust. Enclosed heat-generating devices shall not cause external surfaces to reach temperatures capable of igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmosphere. Enclosures shall meet dust-penetration and temperature-design tests and prevent aging of gaskets (if used).

5.9.2 FEATURES AND TEST CRITERIA

When completely and properly installed, Type 9 enclosures:

1. Provide a degree of protection to a hazardous dust environment from operation of internal equipment

2. Do not develop surface temperatures that exceed prescribed limits for the group corresponding to the atmospheres for which the enclosure is intended when internal equipment is operated at rated load

3. Withstand a series of operation design tests while exposed to a circulating dust-air mixture to verify that dust does not enter the enclosure and that operation of devices does not cause ignition of surrounding atmosphere

4. Are marked with the appropriate class and groups for which they have been qualified.

5.10 UNDERGROUND FACILITIES

Underground facilities consist of electrical equipment and wiring installed in underground locations. Working conditions underground can present to electrical workers hazards different from those presented above ground. This section aids in dealing with such problems.

Electrical work in support of construction of mines, shafts, and underground utilities shall be performed by qualified workers who must meet the requirements in Section 2.8, 30 CFR 75.153 and 77.103. Only those workers shall install equipment and conductors within the construction activity.

Note: DOE does not engage in "mining" as mining is the extraction of minerals for profit. However, the codes related to mining (30 CFR 57, 75, and 77) should be followed, where applicable, along with the OSHA regulations set forth in 29 CFR 1910 and 1926.

Once construction of the underground facilities is completed, all wiring used for construction activities shall be removed and permanent wiring installed in accordance with 29 CFR 1910, Subpart S, and the NEC as applicable. When the work is not covered by these codes as referenced, the applicable paragraphs of 30 CFR 57, 75, and 77 shall prevail.

Electrical equipment and conductors must be used in a manner that prevents shocks and burns to people. Should electrical equipment and conductors present a hazard to people because of improper installation, maintenance, misuse, or damage, the equipment and conductors must be tagged out or locked out as a hazard until fixed. All electrical equipment and conductors shall be chosen and situated in environments conducive to their design and intended use or as tested by an NRTL for the purpose intended.

The voltage of bare conductors, other than trolley conductors, that are accessible to contact by people shall not exceed 50 V. Electrical equipment and conductors, other than trailing cables, shall be protected against overloads and short circuits by fuses or automatic interrupting devices used in accordance with 29 CFR 1910.304.

Adequate clearance between equipment and bare overhead conductors must be maintained in accordance with 29 CFR 1910.303. Conductors not being used to supply power to electrical equipment shall be deenergized and removed from their power supply or have their power supply locked out and tagged out in accordance with 29 CFR 1910.147 and 29 CFR 1910.333. All exposed ends shall be insulated.

Access doors and cover plates shall be closed at all times, except for installation, testing, and repair. Visible signs warning of danger shall be posted at all substations, switch centers, and control centers to warn people against entry unless they have been authorized to enter and perform duties in these locations.

5.10.1 WORK ON ELECTRICAL EQUIPMENT AND CIRCUITS

Before any work is performed on electrical equipment or circuits, the power source or sources shall be deenergized unless power is a required part of the work procedure. Lockout procedures in 29 CFR 1910.147 and 29 CFR 1910.333 shall be followed. In addition, the following rules apply for energized work:

1. Power-cable plugs and receptacles for circuits greater than 150 V potential to ground shall not be connected or disconnected under load unless they are of the load-break type. Energized power cables in excess of 150 V potential to ground shall be handled in accordance with 29 CFR 1910.331. Care shall be taken to prevent damage or shock and burn from the energized cable.

2. Proper tools shall be used to remove or install fuses to protect people from shock or burns.

3. All safety-related electrical work practices covered by the provisions in 29 CFR 1910.331 through .335 shall be followed.

4. Exposed electric connections or resistor grids not protected by location shall be insulated unless impractical. In this case, guarding shall be installed to prevent accidental contact by people or equipment.

5. Communication conductors shall be installed in accordance with 30 CFR 57.12010 and 75.516-2.

6. Lights and lamps shall be properly guarded if they pose a hazard and shall be kept away from combustible material.