When the emergency system is switched in, fluid flows in through port 1 and pushes plunger 2 to the left, overcoming the resistance of helical spring 5 and shutting off inlet port 4 of the main hydraulic system. The fluid then flows through an axial hole in plunger 2 and out through port 3. Spring 5 is adjusted by threaded member 6.
$3611$SHP,Va$