The typical flow characteristics curves are given in Fig. ( VII.11) .

Fig. VII.11: Flow capacity characteristics of various pneumatic valves

VII.4.2 Hydraulic actuator

Hydraulic actuators employ hydraulic pressure to move a target device. These are used where high speed and large forces are required. Pressure applied to a confined incompressible fluid at any point is transmitted throughout the fluid in all directions and acts upon every part of the confining vessel at its interior surfaces. Fig. VII.12 represents the schematic of a hydraulic actuator.