Question 649Steam Plants - Assistant Engineer
70% to passA sequential lift, nozzle valve control bar on a turbo-generator, utilizes which of the following operating principles?
AA servomotor, mechanically connected to nozzle valve hand wheels, opens or closes the valves in accordance with the type of electrical signal received.
BA lifting beam mechanism engages nozzle valve stems of varying lengths.
CA hydraulic piston raises or lowers individual valves according to pressure received from a governor.
DA hydraulic piston raises or lowers groups of valves according to pressure received from a governor.
AI Explanation
The correct answer is B) A lifting beam mechanism engages nozzle valve stems of varying lengths. The sequential lift, nozzle valve control bar on a turbo-generator utilizes a lifting beam mechanism to open and close the nozzle valves. This mechanism engages the nozzle valve stems, which are of varying lengths, to sequentially lift the valves. This allows for precise control of the steam flow to the turbine, which is a key operating principle for this type of system. The other answer choices describe different valve control mechanisms that are not applicable to the sequential lift, nozzle valve control bar system described in the question.
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