Hydraulic Relief Valve
Hydraulic relief valves are used to limit the pressure in a hydraulic system. They achieve this result by allowing the pressurized hydraulic fluid to flow out of the system into an auxiliary passage. These valves protect hydraulic systems from being exposed to high pressures that exceed the mechanism's specified limits. If the pressure in a hydraulic pump exceeds its designed pressure limit, internal leakage or damage to the pump components can occur.
In hydraulic control systems, the relief valve acts as a check valve, with a ball and an adjustable spring. When the fluid is diverted into the auxiliary passage, the pressure inside the hydraulic cylinder drops, allowing the valve to close again.
A hydraulic system will often employ several types of valves, although the hydraulic relief valve is usually the first encountered in the circuit. Hydraulic relief valves can be found in almost any mechanism that runs on hydraulic power, such as automobile transmissions, brakes, power steering, aviation, and in industrial and construction machinery.