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Home Online tests CBT Oil tanker MASTER / Ch-Officer Test Online for Seamen about Flue Gas Plant (CBT 0008) (CBT)
Online testing: Test Online for Seamen about Flue Gas Plant (CBT 0008) (CBT)
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According to the Fire Safety Systems Code what is the maximum oxygen content permitted in the cargo tanks of an oil tanker?
8 % by volume.
11 % by volume.
3 % by volume.
21 % by volume.
According to the Fire Safety Systems Code which one of the following would be considered a safe amount of oxygen in the output from an inert gas plant?
Less than 16 % oxygen.
Less than 5 % oxygen.
Less than 11 % oxygen.
Less than 21 % oxygen.
According to the instructions in this module, which of these options would be carried out first when starting up a flue gas plant?
Start the blower.
Open the blower discharge valve.
Open the boiler uptake valve.
Open the gas regulating valve.
If the inert gas at the blower outlet gets too hot a high temperature alarm is given. What will happen if the temperature of the gas continues to rise?
The backup scrubber water pump will be started automatically.
The inert gas will be vented to air until the temperature drops.
The temperature of the inert gas in the cargo tanks should be monitored every 15 minutes.
The inert gas blowers will stop and the gas regulating valve closes.
In an oil cargo tank in which there is a mixture of hydrocarbon gas and air, which of the following is the best definition of the “Lower flammable limit” (LFL)?
It is the point where the oxygen content becomes too high to support combustion.
It is the concentration of hydrocarbon vapour below which there is insufficient gas in the mixture to support combustion.
It is the point where the concentration of inert gas becomes too low to prevent combustion.
It is the point where the concentration of inert gas becomes too high to support combustion.
In an oil cargo tank in which there is a mixture of hydrocarbon gas and air, which of the following is the best definition of the “upper flammable limit” (UFL)?
It is the concentration of a hydrocarbon gas which is just enough to support combustion.
It is the concentration of hydrocarbon gas above which there is insufficient oxygen to support and propagate combustion.
It is the point where the concentration of inert gas becomes high enough to prevent combustion.
It is the point where the oxygen content becomes too high to support combustion.
In relation to oil tanker cargo spaces which one of the following is the best definition of the expression “purging”?
To replace the inert gas in a tank with fresh air.
To replace the inert gas in a cargo tank with hydrocarbon gas.
To blow inert gas into a tank to reduce the oxygen or hydrocarbon gas level.
To replace the inert gas in a cargo tank with oil cargo or ballast.
In some types of inert gas plants using flue gas, air is supplied to the boiler uptake valves. What is the reason for this?
To prevent condensation in the inert gas plant when it is shut down.
To cool the scrubber tower when the plant is shut down.
To ensure no flue gas leaks pass the uptake valves when the plant is shut down.
To prevent inert gas passing into the boiler uptake when the plant is running.
In which one of the following IMO publications would you find the requirements for the design of a new inert gas system?
SOLAS Chapter IV.
International Code for Fire Safety Systems (FSS Code).
MARPOL Annex I.
ISM Code.
Many oil tankers are fitted with an inert gas system supplying their cargo tanks. What is the main purpose of introducing inert gas into a cargo tank?
To create a non-explosive atmosphere in the tank.
To prevent evaporation of the cargo.
To reduce the generation of static electricity in the tank.
To make the tank safe for entry.
On an oil tanker how long must the deck water seal supply be left on after the inert gas system is shut down?
It must be left running continuously to maintain an adequate seal.
It is left running for two hours after shut down of the inert gas plant.
It is left running for 30 minutes after the inert gas plant is shut down.
It can be stopped as soon as the inert gas plant has been shut down.
On inert gas plants when the scrubber water flow drops below a certain rate an alarm is given. What will happen if the flow rate drops further?
The boiler uptake valve will close.
The deck seal sea water pump will automatically switch to supply the scrubber.
The pressure control system will reduce the plant output.
The inert gas blowers will stop and the gas regulating valve closes.
On some inert gas plants using flue gas the speed of the blowers is variable. Which of the following is the best explanation for fitting variable speed blowers?
The pressure of the gas delivered to deck can be controlled.
The speed can be reduced during blower washing.
The speed can be varied to prevent bearing damage.
The electrical power used by the blowers can be reduced.
Some oil tankers are fitted with one large inert gas blower and one smaller blower. Which of the following is the best explanation for fitting a small blower?
It can be used when topping up the gas pressure at sea.
The total blower capacity can be reduced.
It keeps electrical loads lower during discharges.
It is for use when gas freeing.
The power supply to a flue gas type inert gas plant is normally left on, even when the plant is shut down. Which of the following best describes the reason for this?
Some alarm functions must be operational even when the plant is not.
The oxygen level must be continuously monitored.
I don’t know.
The blowers will automatically be turned every 6 hours.
What is the Fire Safety Systems Code requirement regarding non return devices in the inert gas main for inert gas systems on oil tankers?
There must be at least two devices one of which should be a water seal type.
There must be at least two water seal type devices fitted.
There must be at least two neither of which should be a water seal type.
As long as there is a water seal no other devices are required.
What is the main risk associated with dilution of a normally inerted cargo oil tank atmosphere with fresh air?
During the process the oxygen content may exceed the maximum limit for a flammable mixture.
During the process the atmosphere may be within the flammable range for some of the time.
During the process the atmosphere may become too lean for some of the time.
During the process the atmosphere may become over rich for some of the time.
What is the purpose of the deck water seal fitted to an oil tanker’s inert gas system?
To prevent backflow of hazardous vapours into the gas safe areas.
To clean the inert gas before it enters the cargo tanks.
To prevent inert gas entering the tanks during loading operations.
To cool the inert gas before it enters the cargo tanks.
What is the purpose of the pressure/vacuum breaker fitted to an oil tanker’s inert gas system?
To control the pressure of inert gas supplied to the cargo tanks.
To relieve excess pressure or vacuum in the inert gas main.
To improve cargo pump performance in case the inert gas blower cannot keep up with the cargo discharge rate.
To prevent backflow of cargo vapours into the inert gas scrubber.
When an oil tanker has a flue gas type inert gas plant which is also used for gas freeing of cargo tanks where is the air normally drawn from?
A gas free tank.
The deck seal vent.
The blower fresh air inlet.
The flue of a shut down boiler.
When entering any part of the inert gas system to carry out maintenance or inspections, which of the following is the main danger to personnel?
Acidic attack.
Bacterial infection.
Gas flammability.
Oxygen deficiency.
When opened up the scrubber unit of a flue gas type inert gas plant is found to contain a mattress of polypropylene mesh. Which of the following is the best explanation for this mesh being there?
It acts as a wet filter inside the scrubber.
It is fitted to the scrubber to dry the gas.
It has fallen from the blower inlet into the scrubber.
The lining of the scrubber has come off.
When the inert gas plant on an oil tanker suffers an automatic shutdown which one of the options below is true of the seawater pumps and blowers?
Only the seawater pumps are left running.
All pumps and blowers are shut down.
All pumps and blowers are left running.
All pumps and blowers are left running, the boiler uptake valve shuts the gas off.
Which of the following best describes the action to be taken by the watchkeeper as soon as the blower in a flue gas type inert gas plant is stopped during shut down of the plant?
The scrubber water should be turned off.
The blower washing water should be turned on.
The blower washing water should be turned off.
The blower drains should be shut.
Which of the following best describes the most likely cause of low deck main pressure while a flue gas type inert gas plant is running?
Cargo discharge rate in excess of the blower output.
Deck seal empty.
P/V valve seized shut.
Low boiler load.
Which of the following best describes the most likely cause of the boiler soot blowers failing to work while a flue gas type inert gas plant is running?
The exhaust gas pressure will be too low for effective soot blowing.
The exhaust gas is diverted away from the tubes during inert gas production.
The interlock is operating to prevent excessive soot entering the inert gas.
The cargo pump turbines will reduce steam pressure too far.
Which of the following best describes the most likely initial consequence of low boiler load when a flue gas type inert gas plant is running?
A high oxygen level.
A low deck main pressure.
High gas temperature at the blower outlet.
Increased inert gas recirculation.
Which of the following best describes the reason for the fixed oxygen meter being fitted close to its sampling point?
The oxygen level rises as it passes along the sample line.
The oxygen level falls as it passes along the sample line.
To reduce the time between the sample being taken and analysed.
To protect it from heat.
Which of the following is the best definition for “inert gas”, as used to protect the cargo spaces of oil tankers?
It is any gas containing less than 21 % by volume of oxygen.
It is a gas containing insufficient oxygen to support the combustion of hydrocarbons.
It is a gas containing too much hydrocarbon vapour to support combustion.
It is a gas containing no oxygen.
Which of the following is the best explanation of the purpose of the scrubber unit in a flue gas type inert gas plant?
To prevent flue gas entering the plant while it is shut down.
To cool the gas while removing soot particles and sulphur dioxide.
To cool the gas.
To remove moisture from the flue gas before being sent to the tanks.
Which of the following is the main purpose of filling the free space above the oil cargo onboard a tanker with inert gas?
To keep the tank atmosphere outside the flammable range.
To prevent contamination of the cargo.
To cool the tank.
To reduce evaporation of the cargo.
Which of the following is the typical oxygen level in the exhaust gas that can be achieved from good combustion in a ship’s boiler?
7 to 8 %.
0,1 to 0,5 %.
4 to 5 %.
9 to 10 %.
Which of the following operations is carried out last when shutting down a typical flue gas plant?
Shut down the scrubber water pump.
Close the boiler uptake valve.
Close the gas regulating valve.
Open the ventilation valve to atmosphere.
Which one of the following is a maintenance problem that can be seen during an external examination of the blower of an inert gas plant?
Epoxy coating damage.
Soot build up.
Impeller corrosion.
Cracking.
Which one of the following is likely to happen if the oxygen content of the inert gas being supplied to the cargo spaces of an oil tanker rises above 8 percent and the “high-high” oxygen alarm sounds?
The boiler burners will shut down.
The gas regulating valve will automatically close, and the vent or recirculation valve will open.
The inert gas blowers will stop and the plant is shut down.
The gas regulating valve and the boiler uptake valves will automatically close.
Which one of the following is the generally agreed reason for the rise in explosions experienced in the 1960s and 1970s, as oil tankers became larger?
Static electricity.
Low sulphur crude.
High sulphur crude.
High voltage electrical systems.
Which one of the following is the minimum required capacity of the blowers fitted to an oil tanker’s inert gas plant, as a proportion of the ship’s maximum cargo discharge rate?
100 % in total.
110 % in total.
100 % per blower.
125 % in total.
Which one of the following would be the best gas to use to zero the fixed oxygen analyser monitoring an inert gas plant?
Butane.
50/50 Methane/Butane mix.
Methane.
Nitrogen.
Which one of the following would you expect to happen on an oil tanker if the pressure in the inert gas main falls to about 50 mm Water Gauge during cargo discharge operations?
The cargo pumps shutdown automatically.
The inert gas blowers shutdown automatically.
The inert gas recirculating valve automatically opens fully.
The P/V valve will open fully.
Which term is used to identify the operation whereby inert gas is introduced into a cargo tank in order to reduce the oxygen content throughout the atmosphere of the tank to 8 % or less by volume?
Topping up.
Purging.
Gas freeing.
Inerting.
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