Piston valve

An ejector is a simplified type of vacuum pump or compressor which has no pistons, valves, rotors, or other moving parts. Figure 10-98 illustrates a steam-jet ejector. It consists essentially of a nozzle which discharges a high-velocity jet across a suction chamber that is con-... 

Lift Check Valves These valves (Figs. 10-160 through 10-162) are made in three styles. Vertical lift check valves are for installation in vertical lines with flow normally upward. Globe (or piston) valves with a 90° bonnet (Fig. 10-161) are for installation in horizontal lines, although inclined bonnet versions (approximately 45°) with spring... 

The eventual supplementary balancing piston is actually fitted as a backup device if the bellows fail in service this device will ensure that the valve still relieves at the correct set pressure. Balancing piston valves are uncommon and expensive, but without the balancing piston fitted, the variable backpressure has an adverse effect on the set point of the SRV. This may result in the valve not relieving at its hill capacity or not achieving hill lift within 10% overpressure... 

The difference between a balanced bellows valve and a balanced piston valve is that additional assurance for safe operation is built into the latter by adding a balanced piston on top of the guide (Figure 5.29). 

Valves Among the different possible valves (rotary multiposition with one or several inlets associated to several outlets, or two-way valves), we recommend the use of two-way piston valves because of a possibly enhanced reliability and the easiness of troubleshooting if it becomes necessary. 

The residue was ejected intermittently by a double lock discharge system illustrated in Figure 20. It featured two piston valves ( ram valves ) and an intermediate chamber. With the first ram valve open and the second ram valve closed, the chamber was filled with both solids and product vapor at the operating pressure of the reactor. Then the first ram valve was closed and the second ram valve was opened, thus leading to an ejection of the chamber content into a cyclone, where the solids were separated from the vapor. 

The second area of application is as a potential material for inclusion in reciprocating internal combustion engines, principally diesel engines. The goals here are to insulate components such as pistons, valves, intake manifolds and exhaust ports, and to protect the moving parts from wear and corrosion. 

Piston engine components. Pistons, Valves SiC, Si3N4, composites 900-1400 Combustion gases McLean (1986)... 

When human strength is no longer sufficient to adjust the cradle, a servo-motor with piston-valve h and slide-valve i is used. The servomotor is driven by a small gear pump which produces a pilot pressure of about 20 atmospheres and is rated for 2 to 3 H.P. 

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. 

Figure 14 A piston valve EFD applies here automatically a bead of white glue of medium viscosity — beads of glue do not sag. (Source EFD USA/Dosage 2000 France).

Fig. 14 shows a piston valve application of a medium viscosity glue (20,000 mPa sec) at high speed,... 

These pumps are often used for processing highly viscous adhesives. The design of a twin piston pump is schematically shown in Fig. 38.4. The special feature of a twin piston pump is that it transports materials in both movement directions. This is achieved due to the fact that the two chambers, which are separated by the piston, are kept in phase with each other by a nonreturn valve, and the cross section of the lower chamber is twice as large as the cross section of the upper chamber. When the pump is at the bottom dead center, both nonreturn valves close (= piston valve and foot valve). If the piston now moves upward, the foot valve opens and the lower chamber is filled. Simultaneously, the adhesive in the upper chamber is transported via the outlet into the connected pipe system. After reaching the top dead center and reversal of movement of the piston, the piston valve opens and the foot valve closes. The upward movement of the piston forces the volume of adhesive from the lower chamber... 

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