Lumped-Parameter Model of the Delay Solenoid Valve with Integral Thermistor

In the past, many applications have been found for delay solenoid valves using an integral thermistor for delay action. These applications include oil and gas flow control in hydraulic and pneumatic systems used in a wide variety of situations, ranging from the residential heating furnace to large industrial controllers. Because of the large number of parameters involved in the design of these valves, no known analytical method exists to accurately predict time delay and power consumption. This has resulted in a trial-and-error approach to design and thermistor selection involving expensive prototypes for testing purposes. In this paper the author has developed an accurate lumped-parameter model. This model clearly illustrates those parameters which govern the terminal variables such as power consumption and also allows thermistor selection for a given delay based on manufacturers' specifications. The scope of applications of delay valves should be increased as a result of greater predictability in valve performance and greater flexibility and reduced cost in thermistor selection. The principle of geometric similarity is also established, which leads to scaled-down prototypes of larger valves for testing purposes.