Sealed electrical equipment

Evacuating ft sealing equipment for refrigeration units, electric light bulbs, rodio tubes, and vacuum tubes for radar equipment, television sets, and other types of electronic equipment d reseorch apparatus... 

Acceptable protection techniques for electrical and electronic valve accessories used in specific class and division locations include explosion-proof enclosures intrinsically safe circuits nonincendive circuits, equipment, and components dust-ignition-proof enclosures dusttight enclosures purged and pressurized enclosures oil immersion for current-interrupting contacts and hermetically sealed equipment. Details of these techniques can be found in the National Electrical Code Handbook, available from the National Fire Protection Association. 

When electrically driven equipment is to be operated in an XP and/or an electrically classified area (meaning flammable vapors are, or could be, present), it must be rated to operate in that environment. This means that the ignition source associated with the electricity used to power the equipment must be sealed to prevent the flammable vapors from infiltrating the housing (usually done by the manufacturer). The robustness and the integrity of these seals dictate whether the equipment can be operated in an environment where flammable vapors are always present [National Electric Code (NEC) Class 1 Division 1 area] or where flammable vapors could be present (NEC Class 1 Division 2). 

The principal uses of PCTFE plastics remain in the areas of aeronautical and space, electrical/electronics, cryogenic, chemical, and medical instmmentation industries. AppHcations include chemically resistant electrical insulation and components cryogenic seals, gaskets, valve seats (56,57) and liners instmment parts for medical and chemical equipment (58), and medical packaging fiber optic appHcations (see Fiber optics) seals for the petrochemical /oil industry and electrodes, sample containers, and column packing in analytical chemistry and equipment (59). 

Electrical Hazards. Because carbon fibers are conductive, the airborne filaments can create serious problems shorting out electrical equipment. The best option is to locate sensitive equipment in clean rooms outside of areas where carbon fiber is being processed. If this is not possible, electrical cabinets must be effectively sealed to prevent contact with carbon fibers. A filtered air-positive purge provides additional protection for sensitive equipment. 

In areas where electrical equipment is exposed to contaminants, the selection of equipment whose contacts are oil-immersed or hermetically sealed can increase reliability and equipment life. Similarly, providing environmentally-controlled equipment rooms can greatly increase equipment life at locations where contaminants are prevalent. In offshore and other areas exposed to salt, type 316 stainless steel is often preferred over types 303 and 304, which will pit with time. Likewise, in similar locations, equipment fabricated from galvanized steel will corrode much more rapidly than equipment hot-dip galvanized after fabrication. 

Although microwave-heated organic reactions can be smoothly conducted in open vessels, it is often of interest to work with closed systems, especially if superheating and high-pressure conditions are desired. When working under pressure it is strongly recommended to use reactors equipped with efficient temperature feedback coupled to the power control and/or to use pressure-relief devices in the reaction vessels to avoid vessel rupture. Another potential hazard is the formation of electric arcs in the cavity [2], Closed vessels can be sealed under an inert gas atmosphere to reduce the risk of explosions. 

Specifically designated electrical equipment can be manufactured so that its internal components are completely sealed. This eliminates the possibility electrical arcing components or circuits can contact combustible vapors or gases. 

Living on less than five hundred dollars a month from Social Security income, Susan recently became the owner of a small home built to meet her environmental needs. The kitchen, living and work areas are all part of one open room. Electrical equipment is limited to a computer and television, both carefully sealed and shielded to minimize EMF exposures. 

---