Which of the following statements describes how the main propulsion turbine over speed relay initiates closing of the throttle valve?

Correct Answer: Option C — Excessive speed causes an oil pump to develop sufficient pressure to open a spring loaded relay valve which tends to close the steam control valve.

Main propulsion turbine governing and overspeed systems commonly use an attached pump supplying governor oil pressure. At overspeed, the pump output overcomes a spring-loaded relay valve, dumping oil pressure or shifting oil flow to close the steam control valves.