Pressure seal valves

Pressure seal valves get their name from the fact that the higher the cylinder pressure the greater the... 

A manually operated pressure seal valve is illustrated in Fig. 5-7. Externally these t>pe valves cannot be distinguished from an O-ring seal vaJve one type is shown in Fig. 5-8. These valves are made in a wide variety of materials— brass, stainless steel, aluminum, etc. 

Extracted from Face-to-Face and End-to-End Dimensions of Ferrous Valves, ANSI B16.10—1973, with permission of the publisher, the American Society of Mechanical Engineers, New York. To convert inches to millimeters, multiply by 25.4. tNot shown in ANSI B16.10 but commercially available. jTliese dimensions apply to pressure-seal or flangeless bonnet valves only. 

Conventional Flare System - The majority of pressure relief valve discharges which must be routed to a closed system are manifolded into a conventional blowdown drum and flare system. The blowdown drum serves to separate liquid and vapor so that the vapor portion can be safely flared, and the separated liquid is pumped to appropriate disposal facilities. The blowdown drum may be of the condensible or noncondensible type, according to the characteristics of the streams entering the system. Selection criteria, as well as the design basis for each type of blowdown drum, are detailed later in this volume. The design of flares, including seal drums and other means of flashback protection, is described later. 

K , = liquid flow factor for variable back pressures for balanced seal valves only (see Figure 7-28). For atmos., K,, = 1.0. 

K, = vapor or gas flow factor for variable back pressures from Figure 7-27.4 or 27B. Applies to Balanced Seal valves only. 

On double seal installations, be sure the sealing liquid lines are connected, the pressure control valves are properly adjusted, and the sealing liquid system is operating before starting the equipment. 

Liquid xenon, used as a solvent, will burst sealed apparatus if allowed to warm up. Pressure relief valves are recommended. 

After weighing, the munitions are released to a four-unit vacuum purge station. Automatic vacuum/purge nozzles make a vacuum/pressure seal on top of the empty munitions, and a three-way automatic valve... 

B. 1,4-Cyclohexanedione. The purified 2,5-dicarbethoxy-l,4-cyclohexanedione (170 g., 0.66 mole) (Note 5) and 170 ml. of water are placed in a glass liner (vented) of a steel pressure vessel of 1.5-1. capacity (fitted with a pressure-release valve). The vessel is sealed, heated as rapidly as possible to 185-195°, and kept at this temperature for 10-15 minutes (Note 6). The reaction vessel is immediately removed from the heater, placed in a large tub of ice water, and cooled to room temperature. The gas pressure then is carefully released. The resulting yellow to orange liquid is transferred to a distillation flask with the aid of a minimum volume of ethanol, and most of the water and ethanol is removed under reduced pressure by means of a rotary evaporator. The flask is attached to a short heated column fitted with a short air condenser. The remainder of the water and ethanol is removed under reduced pressure, and the 1,4-cyclohexanedione is distilled, b.p, 130-133° (20 mm.). The product solidifies to a white to pale-yellow solid, m.p. 77-79°, deld 60-66 g. (81-89% yield from 2,5-dicarbethoxy-l,4-cyclohexanedione). The compound may be conveniently recrystallized from carbon tetrachloride (7 ml. per gram of dione) the purified product is obtained as white plates, m.p. 77-79° (90% recovery). 

In addition, the practice of adding acid to water with constant stirring should be observed. When acid mixtures are prepared, only the quantity to be used should be prepared, as these may not be safe to store. Finally, pressure relief valves should be provided to any sealed container in which a digestion is to take place. One should be aware, however, that some analyte can be lost as droplets when these valves vent. This is one of the advantages of the pressure-monitored microwave digestion system. In this, the pressure is controlled by modulating the input power, so venting is avoided. 

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