COMPONENT OPERATION / Control Valve

Main Relief Valve

The main relief valve prevents pressure inside the main circuit from increasing over the set pressure during the cylinder operation. This function prevents oil leakage from the hoses and piping fittings as well as cylinder breakage.

Relief Operation

1. Pressure in port HP (main circuit) acts on the pilot poppet through orifice A in the main poppet and orifice B in the seat.

2. When pressure in port HP reaches the set force of spring B, the pilot poppet is opened, pressure oil from passage A flows to port LP (hydraulic oil tank) through the outer circumference of the sleeve.

3. At this time, a pressure difference occurs between port HP and the spring chamber due to orifice A.

4. When this pressure difference reaches the set force of spring A, the main poppet is opened and pressure oil from port HP flows to port LP.

5. Consequently, pressure in Port HP (main circuit) decreases.

6. When pressure in Port HP (main circuit) decreases to the specified level, the main poppet is closed by the force of spring A.

COMPONENT OPERATION / Control Valve

During Normal Operation:

During Relief Operation:

T3-2-16