Electric for Gasoline Station

514. GASOLINE DISPENSING AND SERVICE STATIONS

514-1. Definition. 514 to areas used for service of vehicles using diesel fuel and to dispensing pumps and areas for diesel fuel. Fuel with a flash point above 100 F may be ruled to be not “ a volatile flammable liquid” to which the regulations of Arts. 511 and 514 are addressed.
514-2. Class I Locations. General storage and handing of flammable and combustible liquids. The space within the dispenser enclosure is a class I, Division 1 up to 4 ft above the base. The space within 18 in, of the outside of the dispenser enclosure is a class I, Division 2 Location up to 4 ft above the enclosure base. The 18-in. space around the dispenser was Division 1 space in previous of the code.

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NEC. Code ,Article 500, Hazardous (Classified) Locations

Briefly, the hazards in the three classes of locations are due to the following
Causes:
Class I, highly flammable gases or vapors
Class II, combustible dust
Class III, combustible fibers or flyings
Article 501. Class I Locations
The more common Class I locations are those where some process is carried on involving the use of a highly volatile and flammable liquid, such as gasoline, petroleum naphtha, benzene, diethyl ether, or acetone or flammable gases.
The basic construction characteristics of equipment for Class I hazardous locations are detailed in various sections of this article and in standards of testing laboratories . Application of the products hinges on understanding those details:
An explosion-proof enclosure for Class I locations is capable of withstanding an explosion of a specified gas or vapor which may occur within it and of preventing the ignition of the specified gas or vapor surrounding the enclosure by sparks, flashes, or explosions of gas or vapor within. Explosion –proof equipment must provide three things 1. strength 2. joints which will not permit flame or hot gases to escape, and 3. cool operation, to prevent ignition of surrounding atmosphere.
There are two generally recognized joint designs intended to provide this control-threaded and flat:
1. Threaded construction of covers and of other removable parts that have five full threads engaged produces a safe, flame-arresting, pressure-relieving joint. When an explosion occurs within a threaded enclosure, the flame and hot gases create an internal pressure against the cover, thus locking threaded surfaces, When the gases reach the outside hazardous atmosphere, they have been cooled by the heat-sink effect of the mass of metal down to a point below the ignition temperature of the outside atmosphere.

2. A flat join is constructed by accurate grinding or machining of the mating surfaces of the cover and the body, This flat works in a manner similar to the threaded joint, The two surfaces are bolted closely together, and as flame and hot gases are forced through the narrow opening, they are cooled by the mass of the metal enclosure, so that only cool gas enters the hazardous atmosphere

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