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An OSV's turbocharged main diesel develops black exhaust at a shaft load it previously carried cleanly. Boost pressure has fallen, and exhaust temperatures have risen across all cylinders. Fuel-supply pressure is normal, but the pressure drop across the turbocharger inlet filter has increased sharply. Where should the engineer concentrate the initial fault investigation?
Correct answer: C - Restriction of the combustion-air inlet filter
Two identical 600 kW diesel generators are paralleled on an isolated shipboard bus in manual load-sharing mode. No. 1 carries 420 kW and No. 2 carries 180 kW; frequency is steady at 60 Hz, reactive load is shared equally, and neither machine is in alarm. The watch engineer wants to balance real power without changing bus frequency. Which paired adjustment accomplishes this?
Correct answer: A - Raise No. 2 governor reference while lowering No. 1 governor reference.
A provision-room refrigeration plant has poor cooling. At the expansion-valve sensing bulb, the R-134a saturation temperature corresponding to the local suction pressure is -12°C, and the measured suction-line temperature is -4°C. Adequately subcooled liquid reaches the filter-drier inlet, but a large pressure drop and an abrupt temperature fall occur across that component. Evaporator airflow is normal. Select the superheat and fault diagnosis supported by these findings.
Correct answer: D - 8 K superheat; restricted liquid-line filter-drier
A machinery-space fuel fire is beyond portable-extinguisher control. The master orders preparation of the fixed total-flooding CO2 system. Fuel has been isolated, everyone is accounted for outside the space, and the release warning has been given. All other openings are secured, but one exhaust fan is still running with its damper open. What must be completed before CO2 discharge?
Correct answer: C - Stop the fan and close its damper to complete enclosure isolation.
A double-acting hatch cylinder must retract against a load. Its full piston area is 50 cm², and its rod cross-sectional area is 20 cm². Pressure at the rod-end port is 100 bar gauge, while the cap end returns freely to the tank. Ignoring friction and return-line backpressure, how much retraction force is available?
Correct answer: B - 30 kN
While underway, the main engine lube-oil duplex filter reaches a differential pressure of 0.9 bar; the maker specifies changeover at 0.7 bar. Bearing-gallery pressure and oil temperature remain normal. The clean chamber is filled and vented, and the assembly is designed for changeover with the engine running. Choose the response that preserves both lubrication and propulsion.
Correct answer: B - Change to the clean chamber while monitoring bearing-gallery pressure.
After replacement of a pressure display, an engineer checks a transmitter whose specified calibration is 4-20 mA over 2-10 bar. The transmitter sends 12 mA, and a calibrated reference gauge at the same tapping reads 6 bar, but the new display reads 5 bar. Which correction addresses the discrepancy without disturbing the valid pressure measurement?
Correct answer: A - Set the display input range to 2-10 bar for 4-20 mA.
During routine treated-bilge discharge in U.S. navigable waters, the oil-content monitor reads 8 ppm. A watchstander sees a visible oil sheen spreading directly from the vessel's discharge. There is adequate bilge holding capacity and no flooding emergency. How should the engineer respond to the conflict between the monitor and the observation?
Correct answer: D - Stop discharge, retain the bilge water, and arrange immediate National Response Center notification.
Two distillate fuels meet a diesel engine's specification and have comparable viscosity and heating value. With injection timing and starting temperature unchanged, switching to the fuel with the higher cetane number should primarily produce:
Correct answer: D - A shorter interval between injection and ignition.
A jacket-water cooler has a pinhole connecting its freshwater and seawater passages. While the engine runs, pressures at the hole are 3 bar gauge on the freshwater side and 1 bar gauge on the seawater side. After shutdown, freshwater pressure falls to 0 bar gauge while seawater pressure remains at 1 bar gauge. Which leakage pattern follows from these pressures?
Correct answer: C - Freshwater enters seawater while running; seawater enters freshwater after shutdown.
The National Assistant Engineer (OSV) (National Assistant Engineer (OSV)) exam is organized into 1 knowledge domains. These free practice questions are drawn from across them so you can see where you're strong and where to study:
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