Switchgear pressurized

Since it is not practical to manufacture a llameproof enclosure due to its size and bulk and the number of knockouts and openings on the doors for switches, metering, indicators, and pushbuttons (PBs) etc., it is common practice to locate the.se assemblies some distance from the affected area in a separate well-ventilated room. Depending upon the location and intensity ol contamination, it may be permissible to meet the requirement by using a pressurized enclosure by maintaining a positive pressure inside the enclosure similar to that for motors (Section 7.1.3..3). When there arc many switchgear assemblies, the room itself can be pressurized, which is safer and easier. Small enclosures, however, such as a PB station, switch or a switch fuse unit or an individual starter unit etc., which can be easily made of MS plates or cast iron, as discussed in Section 7.13, can be mounted in the hazardous area while the main MCC can be installed in the control room, away from the contaminated area and from where the process can be monitored. 

COMPRESSOR WILL NOT START 1. Power supply failure. 2. Switchgear or starting panel. 3. Low oil pressure shut down switch. 4. Controi panel. NOISE IN CYLINDER 1. Loose piston. 2. Piston hitting outer head or frame end of cylinder. 3. Loose crosshead lock nut. 

Mercury is used in the manufacture of thermometers, barometers and switchgear, and in the production of amalgams with copper, tin, silver and gold, and of solders. A major use in the chemical industry is in the production of a host of mercury compounds and in mercury cells for the generation of chlorine. Mercury has a significant vapour pressure at ambient temperature and is a cumulative poison. 

Where ventilation is installed to effect a reduction in the area electrical classification, the rate should be no less than 12 air changes per hour for an adequately ventilated area in accordance with API RP 500. Areas containing ignition sources, such as control and switchgear buildings, gas turbine acoustical enclosures, and power generators, should be pressurized in accordance with NFPA 496, if located in an electrically classified area. 

Beryllium connections and contacts are employed for switchgear and relays. Beryllium oxide is used as substrata for electronic circuits. Cadmium is used in television and fluorescent light phosphors. Cadmium, nickel and mercury are employed in batteries such as "nicad" cells and mercury cells. Mercury is used in fluorescent lamps, electrical switches, and outdoor lamps, as well as instruments for measuring pressure, temperature, and density. Selenium is employed as a photoreceptor in copying machines, and as a semiconductor in rectifiers. Lead applications include lead add storage batteries, a component in color television glass, and, in its oxide form, use as a dielectric material. 

Figs 6.72 and 6.73). Sparking components (e.g. fuses, contactors, circuit breakers) inside or parts not complying with the temperature class of the assembly are individually protected by an independent type of protection (for the most part in a flameproof housing). More recently, attempts have been made to introduce pressurized switchgear assemblies onto the market (Fig. 6.19). In the USA, the classic solution has been a flameproof enclosure with the conduit technique, see Fig. 6.83. 

Figure 9.11 Interior view of a pressurized -p- power distribution unit control panels (foreground) and 1 kV switchgear (background).

Pressurization p EN 60079-2 The occurrence of an explosible atmosphere inside a casing is prevented by maintaining a protective gas overpressure with respect to the surrounding atmosphere. If necessary the interior of the casing is permanently supplied with a protective gas so that the flammable mixture is diluted. Switchgear and control cabinets, analysis equipment, big motors, slip ring and collector motors... 

Low-pressure feed heater, the deaerator and the high-pressure feed heaters Three main feedwater pumps Two start-up feedwater pumps Switchgear rooms Electrical equipment room Lube oil storage tanks Motor-driven fire pumps Air compressors... 

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