Solenoid-operated slide valve

This equipment being very expensive, preference is now given to a servo-motor - similar to that employed wnth the pump in Fig. 174-the piston of which is pilot controlled by a solenoid operated slide-valve. The servo-motor is driven by a small gear pump w hich delivers the pressure oil for a 30 to 40 atm control circuit. 

In oil-hydraulic presses which are controlled by balanced piston-valves, there is only a small force required and therefore a solenoid in conjunction with a spring may be used. As a rule, the solenoid is deenergized in the return position of the main piston. Large control slide-valves are moved by a piston, when the solenoid operated piston-valve serves as a pilot control. 

The slide is located in the compressor casting below the rotors, allowing internal gas recirculation without compression. Slide valve is operated by a piston located in a hydraulic cylinder and actuated by high-pressure oil from both sides. When the compressor is started, the slide valve is fuUy open and the compressor is unloaded. To increase capacity, a solenoid valve on the hydraulic hne opens, moving the piston in the direction of increasing capacity. In order to increase partload efficiency, the slide valve is designed to consist of two parts, one traditional shde valve for capacity regulation and other for built-in volume adjustment. 

The reactor was a tube of 446 stainless steel with an internal diameter of % in. and of 20 in. total length. The catalyst bed was the central 2 in., and a furnace surrounding the tube controlled the temperature to 1°. A sliding thermocouple in a central well of 3 -in. o.d. measured the bed temperature. The catalyst bed volume was 10 cc., and the rest of the reactor was filled with stainless steel spacers to reduce the dead space. Steam was heated to 650° in a preheater and mixed with the reacting gas or air at the top of the reactor, which was operated at atmospheric pressure. The supply of gas and steam was measured by flow meters and controlled by solenoid valves activated by a timer so that the catalyst could be fed on hourly or half-hourly cycles with steam and hydrocarbon or steam and air. In this way, any carbon laydown could be measured by analyzing for carbon dioxide in the air from the second (regeneration) cycle. 

---