The turbine safety cutoff consists of weight 1 which, during normal operation of the turbine, is held by spring 2 and nut 3 against stop 4. These components are arranged in a transverse hole in the main shaft of the turbine. At a speed in excess of the maximum permissible value, the weight is extended by centrifugal force so that it strikes lever 5 which turns about fixed axis A. This releases pawl a and spring 10 turns lever 6 clockwise about fixed axis B. At this, valve spool 7 is shifted downward. In the position shown, corresponding to normal operation, fluid is delivered under pressure by the valve into the control system through pipeline 8. When valve member 7 shifts downward, fluid from the control system drains through the valve back to the tank along pipeline 9. This leads to a drop in pressure in the control system, the shutoff valve rapidly closes and ceases to admit steam into the turbine. Fluid under pressure is discharged through pipeline 11.
$3982$LHP,FD$