Pressure-loaded diaphragm actuators

Fig. 9 Pressure-loaded diaphragm actuators, (a) Planar diaphragm. Positive piessme causes bulge in active region. Foam can replace fluid pressure, (b) Diaphragm actuator showing large out-of-plane motion in response to an applied voltage. Diaphragm actuators can be used for loudspeakers or pumps, (c) Array of diaphragm actuators (each 5.5 mm in diameter) made from a single elastomer...

Figure 9 provides diagrams and examples of pressure-loaded diaphragm actuators. 

Compute the maximum flow for the diaphragm-actuated valve. For best results in service, pressure-reducing valves are selected so that they operate 60 to 70 percent open at normal load. To obtain a valve sized for this opening, divide the desired delivery, in lb/h, by 0.7 to obtain the maximum flow expected. For this valve, then, the maximum flow is 350/0.7 = 500 lb/h. 

Pressure is commonly controlled in systems using diaphragm or piston pumps by adjusting the proportion of the output flow from the pump that is diverted into a return line back to tank. This can be actuated by a simple butterfly valve, an adjustable spring-loaded ball valve, or a valve based on the use of air pressure to control the line pressure. Measurements of the response characteristics of commercially available valve systems have shown that most are able to achieve within 10% of a set value in less than 10 s (Rietz el a/., 1997), and this then has formed the basis of environmental performance standards for agricultural crop sprayers that have recently been agreed within the European Community. 

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