When the pressure becomes great enough to overcome the force of the spring, the piston moves and
causes the pivot lever to rotate. The movement of the lever is transmitted through the linkage to the
microswitch button. This closes the electrical circuit.
Hydraulic systems have devices to protect against excessive pressure. These are called pressure relief
valves. The valves are adjustable and are set to open at a point slightly above maximum system
pressure. When this occurs, the fluid is returned to the system reservoir.
Pressure reducers are used to deliver the correct pressure to each component in a hydraulic system. This
makes it possible to use one hydraulic pump, delivering one set pressure in a system that requires several
Pressure switches are physical combinations of a hydraulic device (pressure port, piston, and sprint) and
an electrical device (microswitch and wiring). Pressure switches are used to sense hydraulic pressure.
Depending on the switch, if the pressure is too high or too low, the microswitch closes and energizes a
valve, stops or starts a pump, or illuminates a warning light.