When the pressure of the fluid in port 1 exceeds the preset value, controlled by the force exerted by helical spring 5, plunger 2 is pushed to the right, allowing the fluid to flow through port 3 to the tank. Axial orifice 4 serves to damp oscillations of plunger 2, the degree of damping depending upon the size of the orifice.
$3608$SHP,Va$