Question 250General Subjects - Assistant Engineer

70% to pass

Suppose the illustrated self-contained, internal-pilot, piston-operated temperature control valve is part of the temperature control system for a steam-heated heavy fuel oil service heater for a steam boiler. If there was a decrease in demand for fuel by the boiler, what statement correctly represents how the valve would initially respond? Illustration GS-0045

Diagram for USCG General Subjects Assistant: Suppose the illustrated self-contained, internal-pilot, piston-operated...
AThe fuel oil heater fuel outlet temperature would decrease, causing the remote bulb pressure to decrease and the control diaphragm to flex upward and through lever action, further open the pilot valve.
BThe fuel oil heater fuel outlet temperature would increase, causing the remote bulb pressure to increase and the control diaphragm to flex upward and through lever action, further open the pilot valve.
CThe fuel oil heater fuel outlet temperature would decrease, causing the remote bulb pressure to decrease and the control diaphragm to flex downward and through lever action, further close the pilot valve.
DThe fuel oil heater fuel outlet temperature would increase, causing the remote bulb pressure to increase and the control diaphragm to flex downward and through lever action, further close the pilot valve.
AI Explanation

The correct answer is D. If there is a decrease in demand for fuel by the boiler, the fuel oil heater fuel outlet temperature would increase. This increase in temperature would cause the remote bulb pressure to increase, and the control diaphragm would flex downward. Through lever action, this would further close the pilot valve, reducing the flow of fuel to the heater and maintaining the desired temperature. The other options are incorrect because they do not correctly describe the response of the valve to a decrease in fuel demand. Specifically, options A and B describe the valve opening further, which would be the opposite of the correct response, and option C describes the diaphragm flexing downward, which is also incorrect.

Related Questions
Q@q.QuestionNumber:As shown in the illustrated block diagram for a distributed automation system, w... Q@q.QuestionNumber:In a low-pressure air compressor, the loss of volumetric efficiency normally res... Q@q.QuestionNumber:When repacking a stuffing box fitted with a lantern ring, which of the following... Q@q.QuestionNumber:Air leakage between the shaft and stuffing box packing in a centrifugal pump is ... Q@q.QuestionNumber:In order to distribute the side pressures over a wide area of the cylinder walls...

Ready to test your knowledge?

Take a General Subjects - Assistant Engineer Practice Exam
Official Resources
46 CFR Machinery & Electrical 46 CFR Engineering USCG National Maritime Center
← Previous All Questions Next →

Want to practice with timed exams?

Download Coast Guard Exams for the full exam experience.

Get the App