ABSTRACT
This chapter focuses on the features and operation of solenoid valves. Pressure control valves are used in fluid power systems. There are three main groups: pressure regulating valves, pressure limiting valves and pressure sequence valves. The pressure regulating valve controls the operating pressure in a control circuit and keeps the pressure constant irrespective of any pressure fluctuations in the system. The pressure limiting valves are used on the upstream side of an air compressor to ensure the receiver pressure is limited and that the supply pressure to the system is set to the correct pressure. The sequence valve senses the pressure of any external line and compares the pressure of the line against a preset adjustable value, creating a signal when the preset limit is reached. Solenoid coils are available in a variety of AC and DC voltages, but are often rated in watts or VA because the current flow is dependent upon the voltage and impedance of the coil.
