668.1 Scope. The provisions of this article apply to the installation of the electrical components and accessory equipment of electrolytic cells, electrolytic cell lines, and process power supply for the production of aluminum, cadmium, chlorine, copper, fluorine, hydrogen peroxide, magnesium, sodium, sodium chlorate, and zinc.
Not covered by this article are cells used as a source of electric energy and for electroplating processes and cells used for the production of hydrogen.
FPN No. 1: In general, any cell line or group of cell lines operated as a unit for the production of a particular metal, gas, or chemical compound may differ from any other cell lines producing the same product because of variations in the particular raw materials used, output capacity, use of proprietary methods or process practices, or other modifying factors to the extent that detailed Code requirements become overly restrictive and do not accomplish the stated purpose of this Code.
FPN No. 2: For further information, see IEEE 463-1993, Standard for Electrical Safety Practices in Electrolytic Cell Line Working Zones.
668.2 Definitions.
Cell Line. An assembly of electrically interconnected electrolytic cells supplied by a source of direct-current power.
Cell Line Attachments and Auxiliary Equipment As ap- plied to this article, a term that includes, but is not limited to, auxiliary tanks; process piping; ductwork; structural supports; exposed cell line conductors; conduits and other raceways; pumps, positioning equipment, and cell cutout or bypass electrical devices. Auxiliary equipment includes tools, welding machines, crucibles, and other portable equipment used for operation and maintenance within the electrolytic cell line working zone.
In the cell line working zone, auxiliary equipment in- cludes the exposed conductive surfaces of ungrounded cranes and crane-mounted cell-servicing equipment.
Electrically Connected. A connection capable of carrying current as distinguished from connection through electromagnetic induction.
Electrolytic Cell. A tank or vat in which electrochemical reactions are caused by applying electric energy for the purpose of refining or producing usable materials.
Electrolytic Cell Line Working Zone. The space envelope wherein operation or maintenance is normally performed on or in the vicinity of exposed energized surfaces of electrolytic cell lines or their attachments.
668.3 Other Articles.
(A) Lighting, Ventilating, Material Handling. Chapters 1 through 4 shall apply to services, feeders, branch circuits, and apparatus for supplying lighting, ventilating, material handling, and the like that are outside the electrolytic cell line working zone.
(B) Systems Not Electrically Connected. Those elements of a cell line power-supply system that are not electrically connected to the cell supply system, such as the primary winding of a two-winding transformer, the motor of a motor-generator set, feeders, branch circuits, disconnecting means, motor controllers, and overload protective equipment, shall be required to comply with all applicable provisions of this Code.
(C) Electrolytic Cell Lines. Electrolytic cell lines shall comply with the provisions of Chapters 1 through 4 except as amended in 668.3(C)(1) through (C)(4).
(1) Conductors. The electrolytic cell line conductors shall not be required to comply with the provisions of Articles 110, 210, 215, 220, and 225. See 668.11.
(2) Overcurrent Protection. Overcurrent protection of electrolytic cell dc process power