Tanker Familiarization Tanker Systems and Equipment Questions and Answers 1 — Questions and Answers
Question 1: What is the primary safety function of the deck water seal in a tanker's inert gas (IG) system?
- To cool the inert gas to the required temperature before it enters the cargo tanks.
- To act as a non-return device, preventing flammable cargo vapours from flowing back to the machinery space. (Correct answer)
- To remove soot and sulfur oxides from the boiler flue gas using a series of sprays and baffles.
- To increase the pressure of the inert gas using a venturi effect before it is distributed on deck.
Correct answer: To act as a non-return device, preventing flammable cargo vapours from flowing back to the machinery space.
The deck water seal is a critical safety barrier that allows inert gas to flow from the IG plant to the cargo tanks but uses a column of water to physically block any reverse flow of hydrocarbon gases from the tanks back towards the engine room, where ignition sources are present.
Question 2: During the final stages of discharging a cargo tank, the main centrifugal cargo pump begins to lose suction and cavitate. Which system is specifically designed to efficiently remove the final quantities of cargo from the tank?
- The main ballast pump via a crossover connection.
- The stripping system. (Correct answer)
- A secondary high-capacity centrifugal pump.
- The inert gas system by over-pressurizing the tank.
Correct answer: The stripping system.
Centrifugal pumps are high-capacity but are not efficient at pumping when the suction level is very low or when pumping a mix of liquid and vapor. Stripping systems, which often use positive displacement pumps or eductors, are specifically designed to remove the final quantities of cargo ('the strip') from the bottom of the tank.
Question 3: Which of the following is the primary purpose of a Pressure/Vacuum (P/V) valve fitted on the vent line of a cargo tank?
- To provide the main connection point for the shore vapor recovery hose.
- To automatically relieve minor over-pressure or under-pressure, preventing structural damage to the tank. (Correct answer)
- To serve as the main emergency vent for releasing large volumes of gas during a fire.
- To allow for manual ullaging and sampling of the cargo tank's contents.
Correct answer: To automatically relieve minor over-pressure or under-pressure, preventing structural damage to the tank.
P/V valves are automatic safety devices that protect the tank from damage caused by small pressure fluctuations due to temperature changes or cargo movement. They open to release pressure when it exceeds a set point and open to admit air/gas when a vacuum develops, thus maintaining the tank's structural integrity under normal operating conditions.
Question 4: In a Crude Oil Washing (COW) system, what is used as the washing medium to clean the cargo tanks?
- The cargo of crude oil itself. (Correct answer)
- High-pressure steam mixed with chemical additives.
- Hot seawater heated to over 80°C.
- A special nitrogen-based cleaning solvent.
Correct answer: The cargo of crude oil itself.
Crude Oil Washing (COW) is a process where the crude oil cargo being discharged is itself used as the cleaning fluid. It is directed through fixed tank cleaning machines to dissolve and wash away waxy residues and sludge from the tank surfaces, which improves the cargo outturn.
Question 5: A tanker is loading cargo. An audible and visual alarm activates, indicating the tank level has reached 98% capacity. According to SOLAS requirements, this alarm must be triggered by a system that is what?
- Directly integrated with the main cargo pump's emergency stop.
- Calibrated and certified by the cargo surveyor before each operation.
- Independent of the primary tank level gauging system. (Correct answer)
- Manually armed by the Chief Officer at the start of loading.
Correct answer: Independent of the primary tank level gauging system.
To prevent cargo spills, regulations (like SOLAS and the IBC code) require at least two independent systems for level monitoring. The primary gauging system provides continuous readings. A separate, independent system provides a high-level alarm (at ~95%) and a high-high or overfill alarm (at ~98%), which serves as a final safety barrier.
Question 6: Which of the following valve types is designed specifically to prevent the backflow of cargo in a pipeline, operating automatically without external actuation?
- Gate valve
- Globe valve
- Butterfly valve
- Check valve (Correct answer)
Correct answer: Check valve
A check valve, also known as a non-return valve, is a safety device that allows fluid to flow in only one direction. The flow of cargo in the correct direction opens the valve, while any reversal of flow will automatically close it, preventing backflow. Gate, globe, and butterfly valves require manual or powered actuation to open or close.
Tanker Familiarization Tanker Systems and Equipment Questions and Answers 1
What is the primary safety function of the deck water seal in a tanker's inert gas (IG) system?