When the pressure of the fluid at port 1 exceeds the preset value, controlled by the setting of helical spring 5, piston 2 is pushed to the right, allowing the fluid to pass out through port 3. As the pressure drops, the spring returns piston 2 to its initial position. Spring 5 is regulated by screw 6. Axial orifice 4 serves to damp the oscillations of piston 2.
$3605$SHP,Va$