Question 146Steam Plants - Assistant Engineer

The correct answer is C) proportional plus reset action. A pneumatic dual element, main propulsion, boiler feed water regulating system commonly used aboard ship utilizes proportional plus reset action. This control system combines proportional action, which provides a response proportional to the error, with reset action, which eliminates steady-state error over time. This combination of control actions allows for precise regulation of the boiler feed water level, ensuring stable and efficient operation of the main propulsion boiler. The other options are incorrect because: A) two-position differential action only provides on/off control without the proportional and reset features, B) on off reset action lacks the proportional component, and D) proportional action alone cannot eliminate steady-state error like the proportional plus reset action can.