Actuation triggering

Solenoid actuators are always used with a secondary acmator to provide positive control of the main valve. Because of heat buildup, solenoid actuators must be limited to short-duration activation. A brief burst of electrical energy is transmitted to the solenoid s coil, and the actuation triggers a movement of the main valve s control mechanism. As soon as the main valve s position is changed, the energy to the solenoid coil is shut off. 

Actuators often provide a failsafe function. In the event of an interruption in the powder source, the actuator will place the valve in a predetermined safe position, iisiiallv either full open or full closed. Safety systems are often designed to trigger local failsafe action at specific valves to cause a needed action to occur, vv4uch rnav not be a complete process or plant shutdown. 

Figure 26. An electric (ionic) pulse arrives from the brain through a nerve to the muscle, where it triggers conformational changes in proteins and chemical reactions. All the processes are three-dimensional. The generator (brain) is at the same time an ionic conductor. (Reprinted from T. F. Otero in Polymer Sensors and Actuators, Y. Osada and D. De Rossi, eds., Fig. 1, p., 19. Copyright 19XX. Reprinted with permission of Springer-Verlag.)...

The air is fed to the actuator through a solenoid which is controlled by a pressure switch measuring the pressure at which the actuator is triggered or in this case simply by a push button for the manual test of the valve. 

At least one accident is known where liquid NC13 could separate in a waste-water treatment where bleach was used to oxidize cyanide ions. After an agitation failure, the actuation of a bottom valve triggered the detonation. Direct chlorination would lead to the same dangerous situation. 

---