USCG General Engineering 4 — Questions and Answers
Question 1: What is indicated by a rising exhaust temperature on one cylinder of a diesel engine?
- The cylinder is producing less power than normal
- The cylinder may have a faulty injector or restriction in air flow (Correct answer)
- The fuel pump for that cylinder is delivering too little fuel
- The cooling water flow to that cylinder is excessive
Correct answer: The cylinder may have a faulty injector or restriction in air flow
A rising exhaust temperature on one cylinder typically indicates over-fueling due to a faulty injector or restricted air intake causing incomplete combustion.
Question 2: Which type of corrosion occurs when two dissimilar metals are in electrical contact in an electrolyte?
- Crevice corrosion
- Galvanic corrosion (Correct answer)
- Stress corrosion
- Erosion corrosion
Correct answer: Galvanic corrosion
Galvanic corrosion occurs when two dissimilar metals are in electrical contact in an electrolyte (such as seawater), causing the less noble metal to corrode preferentially.
Question 3: What is the purpose of 'megger testing' of electrical equipment onboard?
- To measure electrical frequency of the generator output
- To measure insulation resistance to detect degradation or faults (Correct answer)
- To test circuit breaker trip response time
- To calibrate power factor correction equipment
Correct answer: To measure insulation resistance to detect degradation or faults
A megger test applies a high DC voltage to measure insulation resistance, detecting degraded or faulty insulation before it causes faults or hazards.
Question 4: In a four-stroke diesel engine, what occurs during the compression stroke?
- Fuel is injected and burned
- The piston moves up with all valves closed, compressing the air charge (Correct answer)
- The piston moves down drawing in fresh air
- Exhaust gases are expelled from the cylinder
Correct answer: The piston moves up with all valves closed, compressing the air charge
During the compression stroke, the piston moves upward with both valves closed, compressing the air charge to a high temperature sufficient to ignite injected fuel.
Question 5: What is the function of a 'sounding tube' on a vessel?
- To measure noise levels in the engine room
- To allow measurement of liquid levels in tanks (Correct answer)
- To test for gas accumulation in enclosed spaces
- To check pressure in compressed air systems
Correct answer: To allow measurement of liquid levels in tanks
Sounding tubes are pipes that extend to the bottom of tanks, allowing crew members to lower a sounding rod or tape to measure the liquid level.
Question 6: What safety device prevents a boiler from operating with low water level?
- Pressure relief valve
- Low-water fuel cutoff (low-level alarm and trip) (Correct answer)
- Water hammer arrestor
- Superheater safety valve
Correct answer: Low-water fuel cutoff (low-level alarm and trip)
A low-water fuel cutoff senses dangerously low water level in the boiler and shuts off the fuel supply to prevent overheating and potential explosion.
Question 7: What does the abbreviation 'RPM' measure on a vessel's propulsion system?
- Radiated Power Measurement
- Revolutions Per Minute of the shaft or engine (Correct answer)
- Resistance Per Mile of the hull
- Rated Power Margin of the engine
Correct answer: Revolutions Per Minute of the shaft or engine
RPM (Revolutions Per Minute) measures how many complete rotations the engine crankshaft or propeller shaft makes per minute, indicating engine speed.
USCG General Engineering 4
What is indicated by a rising exhaust temperature on one cylinder of a diesel engine?