Typically, hydraulic pressure switches are designed for handling of the majority of hydraulic fluids, although there are some that are specifically designed to handle a certain type. Although hydraulic pressure switches may be used in many diverse applications, the most common usage is in the automotive industry.
Within the automotive industry, hydraulic pressure switches are often used for applications such as a means of alerting the driver if the fluid levels are low, to activate a warning light if the engine oil pressure drops below a safe pressure and to automatically switch on the brake lights if there is a pressure rise in the hydraulic brake pipes.
However, there are several other industries that utilize hydraulic pressure switches including: aerospace, for rocket propulsion and monitoring hydraulic fluids within airplanes; industrial, for boilers and chemical processing applications; wastewater, to prevent overflow through careful monitoring of pressures; and marine, for regulation of transmission fluid flow.
Hydraulic pressure switches typically operate within the range of 300 – 2600 pounds per square inch (PSI); however, higher pressure levels, up to 4000 or even 12000 PSI can be achieved. In addition, hydraulic pressure switches normally operate within a temperature range of -20 and 160º Fahrenheit (F).
Hydraulic pressures are actuated by either a drop or a rise in pressure, depending on the requirements of the application. The two main methods of actuation for hydraulic pressure switches are contact and non-contact. Actuation by contact involves physical placement of the pressure switch within the system being regulated, while non-contact actuation does not require physical placement, but utilizes more advanced technologies to allow for regulation while remaining outside of the system.
It is much more common for a hydraulic pressure switch to be actuated through contact versus non-contact. Hydraulic pressure switches are comprised of two main parts: a transducer and a switch. The transducer functions to measure the pressure of the system as well as to sense pressure fluctuation. When the transducer senses a change, it will send a signal to the switch.
The switch will then convert that signal into electrical energy, and use that energy to turn on or off, thus signaling through means of a warning light or sound that there is a problem with the pressure. Hydraulic pressure switches can be differential or vacuum switches: differential switches are used to measure or regulate between two points of differing pressure and are actuated based on the set points, while vacuum switches help regulate the pressure between two closed cavities through conversion of a negative pressure signal to an electrical output.