Pressure Control Valve- Types , Symbol ,Application

Introduction to Pressure Control Valve:
Hydraulic energy is produced as long as the prime mover (usually an electric motor) drives the pump, and hydraulic pressure develops by resistance to pump flow.Hence, the hydraulic system suffers damage if the pump flow is not stopped or off loaded (recirculate) back to the tank during non-action periods of the circuit.Non-action periods arise from stalling an actuator, or by reaching the end of the stroke or the circuit sequence, or during the time-delay periods of the circuit sequence.

In order to avoid hydraulic system damage, power wastage and overheating of the hydraulic fluid, circuit designers use a variety of cleverly designed systems to control maximum system pressure and pump flow during non-action periods.

Pressure-control valves are used in hydraulic systems to control actuator force (force = pressure × area) and to determine and select pressure levels at which certain machine operations must occur.

Pressure controls are mainly used to perform the following system functions:

Limiting maximum system pressure at a safe level.
Regulating/reducing pressure in certain portions of the circuit.
Unloading system pressure.
Assisting sequential operation of actuators in a circuit with pressure control.
Reducing or stepping down pressure levels from the main circuit to a lower pressure in a sub-circuit.

Types of Pressure Control Valve:

Pressure-control valves are often difficult to identify mainly because of the many descriptive names given to them. The function of the valve in the circuit usually becomes the basis for its name. The valves used for accomplishing the above-mentioned system functions are therefore given the following names: