Question 654Steam Plants - Assistant Engineer

The correct answer is B) centrifugal force. The over speed tripping device installed on an auxiliary turbine is automatically actuated by centrifugal force. As the turbine rotates at increasing speeds, the centrifugal force acting on the tripping mechanism increases. When the turbine reaches a pre-determined overspeed condition, the centrifugal force overcomes the spring tension or other restraining forces, causing the tripping mechanism to activate and shut down the turbine to prevent damage. The other options are incorrect because hydraulic pressure (A), pneumatic force (C), and high back pressure (D) are not the primary actuation mechanisms for an over speed tripping device on an auxiliary turbine. These forces may be involved in the overall turbine control system, but they do not directly trigger the over speed trip.