Question 308Steam Plants - 1st Asst/Chief

The correct answer is A) A lifting beam mechanism engages nozzle valve stems of varying lengths. This is the correct answer because a sequential lift, nozzle valve control bar on a turbo-generator utilizes a lifting beam mechanism to engage the nozzle valve stems. The varying lengths of the valve stems allow the lifting beam to open or close the valves in a specific sequence as the beam is raised or lowered. The other answer choices are incorrect because they describe different mechanisms that are not specific to a sequential lift, nozzle valve control bar. Option B describes a servomotor mechanism, option C describes a hydraulic piston that raises or lowers groups of valves, and option D describes a hydraulic piston that raises or lowers individual valves, none of which are characteristic of a sequential lift, nozzle valve control bar.