Tanker Familiarization Tanker Systems and Equipment 3 — Questions and Answers
Question 1: What is the purpose of a crude oil washing (COW) system on a tanker?
- To clean crew accommodations using crude oil solvents
- To use cargo crude oil as a solvent to clean tank residues during discharge (Correct answer)
- To wash crude oil with seawater before delivery
- To neutralize corrosive crude before loading
Correct answer: To use cargo crude oil as a solvent to clean tank residues during discharge
COW systems spray crude oil at high pressure inside tanks during discharge, dissolving wax and sediment to maximize cargo recovery and reduce manual cleaning.
Question 2: A tanker's slop tank is used primarily to:
- Store fresh water for crew use
- Collect tank washing water and oily residues (Correct answer)
- Hold emergency bunker fuel
- Balance the ship during loading
Correct answer: Collect tank washing water and oily residues
The slop tank collects dirty wash water and oily residues from cargo tank cleaning, allowing oil and water to separate before controlled disposal.
Question 3: Which component of the cargo pump system prevents reverse flow when the pump stops?
- Strainer
- Non-return (check) valve (Correct answer)
- Pressure gauge
- Flow meter
Correct answer: Non-return (check) valve
A non-return (check) valve automatically closes to prevent backflow of cargo when the pump loses pressure or shuts down.
Question 4: What does the term 'ullage' refer to in cargo measurement?
- The total volume of cargo loaded
- The distance from the liquid surface to the top of the tank (Correct answer)
- The weight of cargo per cubic meter
- The temperature of cargo at the time of measurement
Correct answer: The distance from the liquid surface to the top of the tank
Ullage is the empty space above the liquid in a tank, measured from the reference point at the top; cargo volume is calculated from ullage tables.
Question 5: On a tanker, what is the function of a 'vapor recovery system'?
- To recover hydraulic fluid lost during pump operation
- To capture cargo vapors during loading for safe disposal or return to shore (Correct answer)
- To recycle engine exhaust gases into the inert gas system
- To separate water vapor from the ballast system
Correct answer: To capture cargo vapors during loading for safe disposal or return to shore
Vapor recovery systems collect hydrocarbon vapors displaced from tanks during loading and return them to shore facilities, reducing emissions and explosion risk.
Question 6: What is the main hazard of a 'sloshing' cargo in a partially filled tank during rough weather?
- Increased cargo temperature causing vaporization
- Dynamic loads that can damage tank structure and affect vessel stability (Correct answer)
- Contamination of cargo by seawater ingress
- Accelerated corrosion of the tank coating
Correct answer: Dynamic loads that can damage tank structure and affect vessel stability
Sloshing generates large dynamic pressure loads on tank bulkheads and can severely compromise structural integrity and vessel stability.
Question 7: Which type of pump is most commonly used for stripping (removing the last traces of cargo from a tank)?
- Centrifugal pump
- Reciprocating positive displacement pump
- Jet pump (eductor) (Correct answer)
- Axial flow pump
Correct answer: Jet pump (eductor)
Eductors (jet pumps) use a high-pressure motive fluid to create suction and are ideal for stripping because they can handle very small volumes and air without damage.
Tanker Familiarization Tanker Systems and Equipment 3
What is the purpose of a crude oil washing (COW) system on a tanker?