Plug-cock

Sodium fluoride is normally manufactured by the reaction of hydrofluoric acid and soda ash (sodium carbonate), or caustic soda (sodium hydroxide). Control of pH is essential and proper agitation necessary to obtain the desired crystal size. The crystals are centrifuged, dried, sized, and packaged. Reactors are usually constmcted of carbon brick and lead-lined steel, with process lines of stainless, plastic or plastic-lined steel diaphragm, plug cock, or butterfly valves are preferred. 

Plug Cocks These valves (Fig. 10-152) are limited to temperatures below 260°C (500°F) since differential expansion between the plug and the body results in seizure. The size and shape of the port divide these valves into different types. In order of increasing cost they are short venturi, reduced rectangular port long venturi, reduced rec taugular port full rectangular port and full round port. 

For lubricated plug cocks, the lubricant must have limited viscosity change over the range of operating temperature, must have low solubility in the fluid handled, and must be applied regularly. There must be no chemical reaction between the luBricant and the fluid which... 

Lever-sealed plug cocks are used for throttling service. Because of the large contact area between plug and body, if a plug cock is operable, there is little likelihood of leakage when closed, and the handle position is a clearly visible indication of the valve position. 

For the larger sizes in high-pressure service, the fixed-ball type with O-ring seat seals requires less operating effort. However, these require two different plastic materi s with resistance to the fluid and its temperature. Like plug cocks, ball valves may be either restricted-port or full-port, but the ports are always round and pressure drop is low. 

Welding lee thru branch Butterfly valve, open Submerged discharge 3-Way plug cock, st. thru, open 90° slondard screwed or 60°single-miter elbow... 

Added by author 1-76 3-Way plug cock opening Is 80% of pipe size. 

Plug Cock Plug Valve Check Valve... 

Plug cock, full port, open-. Screwed or fobricoled I lee or lolerol Ihru run submerged entrance ... 

Toluene is to be pumped between two vessels using a centrifugal pump with a flowrate of 30t h 1. The pipe diameter is 80 mm (internal diameter 77.93 mm). The pipeline is 35 m long, with 4 isolation valves (plug cock), a check valve and 5 bends. The discharge tank is 3 m in elevation above the feed tank. The density of toluene is 778 kgrn 3 and viscosity of 0.251 x 10 3 N-s-rn 2. 

This kind of valve is essential when tight shutoff is needed, particularly of gas flow. Multipass plug cocks, butterfly valves, slide valves, check valves, various quick-opening arrangements, etc. have limited and often indispensable applications, but will not be described here. 

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