Free Tanker Familiarization Tanker Safety Systems Questions and Answers 1 — Questions and Answers
Question 1: What is the primary function of an Inert Gas System (IGS) on board an oil tanker?
- To provide a breathable atmosphere for tank entry and inspection.
- To pressurize cargo for faster discharge operations.
- To prevent tank corrosion by removing moisture.
- To render the cargo tank atmosphere non-flammable by reducing the oxygen content. (Correct answer)
Correct answer: To render the cargo tank atmosphere non-flammable by reducing the oxygen content.
The Inert Gas System (IGS) is a critical safety feature that introduces flue gas or nitrogen into cargo tanks. This process displaces the air, reducing the oxygen level to below 8%, which is insufficient to support combustion, thereby preventing fire and explosion.
Question 2: During cargo discharge, the liquid level in a tank drops, which can create a vacuum. Which safety device automatically allows air or inert gas to enter the tank to prevent structural damage from under-pressure?
- High-velocity vent valve
- Pressure/Vacuum (P/V) valve (Correct answer)
- Emergency Shutdown (ESD) push-button
- Overfill alarm sensor
Correct answer: Pressure/Vacuum (P/V) valve
A Pressure/Vacuum (P/V) valve is designed to protect the tank from both overpressure and vacuum conditions. During discharge, as the liquid level falls, the vacuum side of the valve opens automatically to let air or inert gas in, equalizing the pressure and preventing the tank from collapsing.
Question 3: Which of the following best describes the distinction between a high-level alarm and an overfill alarm on a chemical tanker?
- The high-level alarm is audible, while the overfill alarm is only a visual warning.
- The high-level alarm activates at 98% capacity and the overfill alarm at 95%.
- The high-level alarm is a pre-warning (e.g., at 95% full), while the overfill alarm is a final warning (e.g., at 98% full) that may trigger a shutdown. (Correct answer)
- They are two terms for the same alarm system, which is activated when the tank is completely full.
Correct answer: The high-level alarm is a pre-warning (e.g., at 95% full), while the overfill alarm is a final warning (e.g., at 98% full) that may trigger a shutdown.
High-level and overfill alarms are independent systems. The high-level alarm typically activates at 95% of tank capacity to warn operators to reduce the loading rate. The overfill alarm, a critical safety device, activates at a higher level, typically 98%, and is designed to give a final warning and often initiates an automatic shutdown of the loading operation to prevent a spill.
Question 4: A cofferdam on a tanker is a specific type of void space. What is its main safety purpose?
- To provide additional cargo carrying capacity in an emergency.
- To serve as a primary location for storing firefighting equipment.
- To act as a soundproofing barrier between the engine room and accommodation.
- To isolate tanks containing incompatible substances or to separate cargo tanks from non-cargo areas. (Correct answer)
Correct answer: To isolate tanks containing incompatible substances or to separate cargo tanks from non-cargo areas.
A cofferdam is an empty compartment designed to provide a physical separation between two adjacent spaces. Its purpose is to prevent the leakage and intermixing of liquids from adjoining tanks (e.g., cargo and fuel oil, or two different reactive cargoes) or to separate hazardous cargo areas from machinery or accommodation spaces.
Question 5: In the event of a major cargo hose failure or fire at the manifold during transfer operations, which system is designed to quickly stop the flow of cargo in a controlled manner?
- The Inert Gas System (IGS)
- The main engine trip
- The Emergency Shutdown (ESD) system (Correct answer)
- The tank venting system
Correct answer: The Emergency Shutdown (ESD) system
The Emergency Shutdown (ESD) system is designed for exactly this type of emergency. When activated, it quickly and safely stops the cargo transfer by closing valves and stopping pumps in a predetermined sequence to minimize the consequences of a hazardous event like a hose burst or fire.
Question 6: On a chemical tanker, the cargo tank high-level alarm (95%) and overfill alarm (98%) are required to be two separate and independent systems. Why is this independence crucial for safety?
- To reduce the overall cost of the alarm installation.
- To ensure that a single component failure cannot disable both the primary warning and the final protection against a tank overflow. (Correct answer)
- To allow one system to be taken offline for maintenance during cargo operations.
- To comply with regulations that require different alarm sounds for each level.
Correct answer: To ensure that a single component failure cannot disable both the primary warning and the final protection against a tank overflow.
The independence of the high-level and overfill alarm systems is a fundamental safety principle. It ensures redundancy. If the primary high-level alarm (95%) fails due to a faulty sensor or electrical issue, the separate overfill alarm (98%) will still function, providing a final, critical layer of protection against a cargo spill.
Free Tanker Familiarization Tanker Safety Systems Questions and Answers 1
What is the primary function of an Inert Gas System (IGS) on board an oil tanker?