Mounted in a transverse hole of turbine shaft 1 is weight 2 whose centre of gravity does not coincide with the turbine shaft axis. Weight 2 is subject to centrifugal force and to the action of spring 3 which holds it against stop a. If the speed of the turbine exceeds the preset value, centrifugal force overcomes the resistance of spring 3 and weight 2 extends from shaft 1 so that it strikes lever 4, turning it about fixed axis A, which releases lever 5, turning about fixed axis B. Lever 5 is turned clockwise by spring 6 so that latch 7 releases sleeve 8. Spring 9 moves sleeve 8, together with valve member 10, to the left, closing the valve and shutting off the steam supply to the turbine.
$3981$LHP,FD$