Tanker Familiarization Cargo Handling and Operations 2 — Questions and Answers
Question 1: What is the primary purpose of an inert gas system on a tanker?
- To cool the cargo during transit
- To prevent explosive mixtures from forming in cargo tanks (Correct answer)
- To increase cargo pumping speed
- To reduce cargo viscosity
Correct answer: To prevent explosive mixtures from forming in cargo tanks
Inert gas systems replace oxygen in cargo tanks with inert gas (typically flue gas or nitrogen) to keep oxygen levels below 8% and prevent flammable or explosive mixtures.
Question 2: When loading a tanker, what does the term 'ullage' refer to?
- The total cargo volume loaded
- The distance from the top of the tank to the liquid surface (Correct answer)
- The temperature of the cargo
- The pressure inside the cargo tank
Correct answer: The distance from the top of the tank to the liquid surface
Ullage is the unfilled space in a cargo tank, measured as the distance from the tank top or reference point down to the surface of the liquid.
Question 3: Which valve type is typically used as the primary isolation valve on a tanker's cargo manifold?
- Globe valve
- Ball valve
- Butterfly valve (Correct answer)
- Gate valve
Correct answer: Butterfly valve
Butterfly valves are commonly used on cargo manifolds because they are compact, quick-acting, and provide reliable shut-off with low pressure drop.
Question 4: During cargo discharge, what is 'stripping' on a tanker?
- Removing protective coatings from tank walls
- Pumping out the last remaining cargo using a stripping system (Correct answer)
- Cleaning the cargo lines after discharge
- Venting excess vapors from the tanks
Correct answer: Pumping out the last remaining cargo using a stripping system
Stripping is the process of removing the last quantities of cargo that the main cargo pump cannot handle, using a separate smaller stripping pump or eductor.
Question 5: What is the significance of the 'closed gauging' method on a tanker?
- It allows gauging without opening the tank, preventing vapor release (Correct answer)
- It provides more accurate readings than open gauging
- It can only be used for non-flammable cargoes
- It requires removing the tank top cover to insert a gauge
Correct answer: It allows gauging without opening the tank, preventing vapor release
Closed gauging uses fixed gauging devices that allow tank contents to be measured without opening the tank, which prevents release of hazardous vapors and maintains the inert condition.
Question 6: What is a 'cargo loading plan' primarily used for on a tanker?
- Recording the names of cargo handlers
- Ensuring structural integrity and stability throughout the loading sequence (Correct answer)
- Scheduling crew meal breaks during cargo operations
- Documenting the cargo's commercial value
Correct answer: Ensuring structural integrity and stability throughout the loading sequence
A cargo loading plan is developed to ensure the vessel maintains adequate stability, trim, and structural strength (avoiding excessive bending moments and shear forces) during all stages of loading.
Question 7: What is the purpose of a 'vapor recovery system' during cargo loading?
- To recover spilled cargo from the sea
- To capture displaced cargo vapors and return them to the shore facility (Correct answer)
- To measure the vapor pressure of the cargo
- To supply inert gas to the cargo tanks
Correct answer: To capture displaced cargo vapors and return them to the shore facility
Vapor recovery systems collect hydrocarbon vapors displaced from cargo tanks during loading and transfer them back to shore, reducing atmospheric pollution and improving safety.
Tanker Familiarization Cargo Handling and Operations 2
What is the primary purpose of an inert gas system on a tanker?