Tanker Familiarization Tanker Systems and Equipment 2 — Questions and Answers
Question 1: What is the primary purpose of a tanker's inert gas system (IGS)?
- To cool the cargo during transit
- To maintain a non-flammable atmosphere in cargo tanks (Correct answer)
- To pressurize cargo tanks for faster discharge
- To filter impurities from the cargo
Correct answer: To maintain a non-flammable atmosphere in cargo tanks
The IGS replaces oxygen in cargo tanks with inert gas (typically flue gas or nitrogen) to keep the atmosphere below the flammable range, preventing explosions.
Question 2: Which valve type is most commonly used as a master isolation valve on a tanker's cargo manifold?
- Globe valve
- Needle valve
- Gate valve (Correct answer)
- Ball valve
Correct answer: Gate valve
Gate valves are preferred at cargo manifolds because they provide full-bore flow with minimal pressure drop when fully open.
Question 3: On a product tanker, what does a 'deep-well pump' refer to?
- A pump located in the engine room bilges
- A submersible pump mounted inside the cargo tank (Correct answer)
- A pump that draws cargo from shore storage wells
- A high-pressure pump used for ballast stripping
Correct answer: A submersible pump mounted inside the cargo tank
A deep-well pump is a submersible electric pump installed inside the cargo tank, eliminating the need for a separate pump room.
Question 4: What is the function of a pressure/vacuum (P/V) valve on a cargo tank?
- To regulate pump discharge pressure
- To control ballast water flow
- To protect the tank from overpressure or excessive vacuum (Correct answer)
- To measure cargo quantity
Correct answer: To protect the tank from overpressure or excessive vacuum
P/V valves automatically open to vent excess pressure or admit air/gas when a vacuum develops, protecting tank structural integrity.
Question 5: What material is typically used for cargo hoses when transferring petroleum products to prevent static buildup?
- Standard rubber with no conductive lining
- Electrically bonded hoses with a conductive wire (Correct answer)
- Reinforced PVC hose
- Bare steel flexible pipe
Correct answer: Electrically bonded hoses with a conductive wire
Electrically bonded cargo hoses contain an embedded conductive wire to dissipate static electricity and prevent spark discharge during transfer.
Question 6: Which instrument is used to measure the oxygen content inside a cargo tank before entry?
- Hydrometer
- Colorimetric tube detector
- Catalytic bead combustible gas detector
- Electrochemical oxygen analyzer (Correct answer)
Correct answer: Electrochemical oxygen analyzer
An electrochemical oxygen analyzer measures the percentage of O₂ in a space; at least 20.8% O₂ is required for safe entry into an enclosed space.
Question 7: What is a 'Butterworth opening' on a tanker?
- An emergency escape hatch on the deck
- A fixed access port used to insert tank cleaning machines (Correct answer)
- A pressure relief fitting on the vapor line
- A sight glass for monitoring cargo level
Correct answer: A fixed access port used to insert tank cleaning machines
A Butterworth opening is a deck fitting through which portable or fixed tank cleaning machines (water-washing heads) are inserted during crude oil washing or water washing.
Tanker Familiarization Tanker Systems and Equipment 2
What is the primary purpose of a tanker's inert gas system (IGS)?