USCG General Engineering 3 — Questions and Answers
Question 1: What is the primary purpose of a ship's oily water separator (OWS)?
- To remove water from fuel oil before combustion
- To separate oil from bilge water before discharge overboard (Correct answer)
- To filter seawater for the freshwater generator
- To remove impurities from lubricating oil
Correct answer: To separate oil from bilge water before discharge overboard
An OWS removes oil from bilge water so the effluent meets the 15 ppm standard required by MARPOL Annex I before discharge.
Question 2: What is the correct procedure when a relief valve on a high-pressure system lifts unexpectedly?
- Immediately increase system pressure to reseat the valve
- Shut down the system and investigate the cause before restarting (Correct answer)
- Bypass the relief valve and continue operation
- Replace the relief valve at the next port stop without investigating
Correct answer: Shut down the system and investigate the cause before restarting
An unexpected relief valve lift signals an overpressure condition; the system must be shut down and the root cause identified to prevent equipment damage or injury.
Question 3: Which bearing type is most commonly used for a ship's main propulsion shaft?
- Deep groove ball bearing
- Tapered roller bearing
- White metal (babbitt) journal bearing (Correct answer)
- Needle roller bearing
Correct answer: White metal (babbitt) journal bearing
White metal (babbitt) journal bearings are used for main propulsion shafts because they can carry large radial loads and are self-lubricating with oil or water.
Question 4: What does a 'load cell' measure in marine engineering applications?
- Electrical load on generators
- Force or weight applied to a structural member (Correct answer)
- Cooling water flow rate
- Fuel oil viscosity
Correct answer: Force or weight applied to a structural member
A load cell is a transducer that converts mechanical force or weight into an electrical signal, used in applications like mooring line tension monitoring.
Question 5: What is the function of a 'stern tube' on a vessel?
- Houses the propeller shaft where it passes through the hull (Correct answer)
- Provides emergency propulsion astern
- Contains the rudder post and steering gear
- Exhausts engine gases through the hull
Correct answer: Houses the propeller shaft where it passes through the hull
The stern tube is a watertight housing that supports and seals the propeller shaft as it passes through the vessel's hull.
Question 6: In a refrigeration system, what is the role of the expansion valve?
- Compresses the refrigerant to raise its pressure
- Reduces refrigerant pressure to cause it to cool and absorb heat (Correct answer)
- Condenses refrigerant vapor into liquid
- Circulates refrigerant throughout the system
Correct answer: Reduces refrigerant pressure to cause it to cool and absorb heat
The expansion valve reduces refrigerant pressure, causing it to expand and evaporate in the evaporator, absorbing heat from the refrigerated space.
Question 7: What is the purpose of a 'deaerator' in a marine steam system?
- To remove dissolved oxygen and other gases from feedwater (Correct answer)
- To separate steam from condensate
- To reduce steam pressure before the boiler
- To measure steam quality and dryness
Correct answer: To remove dissolved oxygen and other gases from feedwater
A deaerator removes dissolved oxygen and carbon dioxide from boiler feedwater, preventing corrosion of the boiler and steam piping.
USCG General Engineering 3
What is the primary purpose of a ship's oily water separator (OWS)?