Rotating-disc valve

Figure 19. Rotating-disc valve (Everlasting Valve Co.).

These valves are relatively inexpensive, quarter-turn valves. The seal is made by a rotating disc that remains in the flowstream subject to erosion while in the open position (Figure 15-4). Except in low-pressure service, they should not be used to provide a leak-tight seaL but they can be u.sed to throttle where a tight shut-off is not required. 

In general, active valving permits execution of complex, multistep assays on disc far beyond the capabilities of passive, rotationally controlled valves. This enhanced process control comes at the expense of more complex instmmentation and manufacturing. Additionally, the heat exposure and direct contact of liquid reagents with the valves (in both a solid and melted state) may present a significant limitation of externally actuated active valves for specific applications. 

The URPSA equipment (Figure 6) consists of a piston, a cylinder, valves and an adsorption bed. The piston is moved by an arm connected to a rotating disc driven by an electric motor. The basic operational steps are suction, adsorption and production, desorption, and exhaust step, as shown in Figure 7. The operation in each step is as follows. 

The apparatus is shown in Fig. 4.1. The body of the extraction vessel is made from Pyrex. Separation is effected by absorption of a batch containing both phases into a porous 2 cm diameter nickel-chrome alloy disc (A), the upper surface of which is domed. The disc is mounted on the end of a stainless-steel shaft (B) turned by a geared high-torque electric motor. The disc-shaft-motor assembly can he transported along its axis of rotation to any of three stations. The assembly is shown at its bottom station, with the porous disc within the inner vessel (C), around which is a collar (D) forming the first annular pocket (E). The collar itself forms the inner wall of the second annular pocket (F), the outer wall of which extends upwards to support a Perspex Hd (G) on which the rotor (H) is situated. The inner vessel and both annular pockets are fitted with drain valves. A stiff piece of platinum wire is passed through the Hd into the glassware as far as the level of the first annular pocket. 

There are two classes of rotary valve butterfly and rotating ball. A disc is rotated to vary the flow area... 

Fig. 11. The design consists of an 8-in. diameter rotary valve (Unidev) on which the upper part is fixed (the stator) and the lower part rotates (the rotor). Both rotor and stator are provided with pairs of radial holes. Between the two valve faces is fixed a disc of graphite-loaded PTFE (the progranme disc). The complete valve assembly is compressed together using disc springs with a maximum force of 2 tons. Interconnections between various ports on the stator are used to provide a fixed flow sequence. The lower part of the valve is formed to accommodate twenty coluim loops, retained by cbnipression couplings. The lower mechanism can be rotated in steps equivalent to the distance between each pair of column loops using a reduction gear drive.

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