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# Questions and answers to Crew Evaluation System Test about Flue Gas Plant

This page contains answers to Seagull CES test about Flue Gas Plant, and serve as a database of questions and answers, using which seafarer can prepare to exams for getting certificate of competence, or just to challenge yourself knowledge in this theme.

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Amount of questions: 58.

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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.
3 % by volume.
11 % 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 5 % oxygen.
Less than 16 % 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?
Open the boiler uptake valve.
Start the blower.
Open the blower discharge valve.
Open the gas regulation valve.
How often must the scrubber be flushed with water?
Every hour.
Every time it is used.
Once a year/18 months.
Daily.
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 inert gas will be vented to air until the temperature drops.
The inert gas blowers will stop and the gas regulating valve closes.
The backup scrubber water pump will be started automatically.
The temperature of the inert gas in the cargo tanks should be monitored every 15 minutes.
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 concentration of inert gas becomes too high 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 oxygen content becomes too high to support combustion.
It is the concentration of hydrocarbon vapor below which there is insufficient gas in the mixture 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 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.
It is the concentration of hydrocarbon gas above which there is insufficient oxygen to support and propagate combustion.
In relation to oil tanker cargo spaces which one of the following is the best definition of the expression “gas freeing”?
To reduce the oxygen levels in a tank.
To remove all gases from a tank.
To increase the amount of inert gas in a tank.
To introduce fresh air into a tank.
In relation to oil tanker cargo spaces which one of the following is the best definition of the expression “purging”?
To blow inert gas into a tank to reduce the oxygen or hydrocarbon gas level.
To replace the inert gas in a tank with fresh air.
To replace the inert gas in a cargo tank with hydrocarbon gas.
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 ensure no flue gas leaks pass the uptake valves when the plant is shut down.
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 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?
MARPOL Annex I.
International Code for Fire Safety Systems (FSS Code).
SOLAS Chapter IV.
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 make the tank safe for entry.
To create a non-explosive atmosphere in the tank.
To reduce the generation of static electricity in the tank.
To prevent evaporation of the cargo.
On an oil tanker how long must the deck water seal supply be left on after the inert gas system is shut down?
It is left running for two hours after shut-down of the inert gas plant.
It must be left running continuously to maintain an adequate seal.
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 pressure control system will reduce the plant output.
The inert gas blowers will stop and the gas regulating valve closes.
The deck seal sea water pump will automatically switch to supply the scrubber.
In 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 speed can be varied to prevent bearing damage.
The speed can be reduced during blower washing.
The pressure of the gas delivered to the deck can be controlled.
The electrical power used by the blowers can be reduced.
Select the best option from those given to complete the following statement in relation to protection against excessive vacuum as fitted to the inert gas deck main. The correct operation of the pressure/vacuum breaker is dependent on:
The correct specific gravity of the liquid and the liquid column height.
The correct operation of the mechanical non-return device in the deck main.
The correct operation of the automatic vent to the atmosphere valve.
The correct operation of the deck water seal.
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.
It keeps electrical loads lower during discharges.
The total blower capacity can be reduced.
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 blowers will automatically be turned every 6 hours.
The oxygen level must be continuously monitored.
These diagrams below represent different types of deck seals. Which one is the wet type deck seal?
A.
B.
C.
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 atmosphere may be within the flammable range for some of the time.
During the process the atmosphere may become over rich for some of the time.
During the process the atmosphere may become too lean for some of the time.
During the process the oxygen content may exceed the maximum limit for a flammable mixture.
What is the purpose of the deck water seal fitted to an oil tanker’s inert gas system?
To prevent backflow of hazardous vapors into the gas safe areas.
To cool the inert gas before it enters the cargo tanks.
To clean the inert gas before it enters the cargo tanks.
To prevent inert gas entering the tanks during loading operations.
What is the purpose of the pressure/vacuum breaker fitted to an oil tanker’s inert gas system?
To relieve excess pressure or vacuum in the inert gas main.
To control the pressure of inert gas supplied to the cargo tanks.
To improve cargo pump performance in case the inert gas blower cannot keep up with the cargo discharge rate.
To prevent backflow of cargo vapors into the inert gas scrubber.
What is the recommended period for opening up the non-return valve on deck for internal inspection?
During every ballast voyage.
After use.
Every week.
Once a year.
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 flue of a shut-down boiler.
The blower fresh air inlet.
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?
Bacterial infection.
Acidic attack.
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.
The lining of the scrubber has come off.
It has fallen from the blower inlet into the scrubber.
It is fitted to the scrubber to dry the gas.
When the inert gas plant on an oil tanker suffers an automatic shut-down, 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.
When working inside parts of the inert gas system, such as the scrubber or deck water seal, which procedure must be followed?
Enclosed space entry.
Working aloft.
Working with self-contained breathing apparatus (SCBA).
Electrical work permit.
Which of the following are hazards that may exist within a tanker’s inert gas plant if vapors are allowed back from the oil cargo tanks? Select all that apply:
Toxicity.
Flammable.
Oxygen deficiency.
Soot deposits.
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 blower washing water should be turned off.
The blower washing water should be turned on.
The scrubber 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?
Low boiled load.
Cargo discharge rate in excess of the blower output.
P/V valve seized shut.
Deck seal empty.
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 interlock is operating to prevent excessive soot entering the inert gas.
The cargo pump turbines will reduce steam pressure too far.
The exhaust gas is diverted away from the tubes during inert gas production.
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 low deck main pressure.
A high oxygen level.
Increased inert gas recirculation.
High gas temperature at the blower outlet.
Which of the following best describes the reason for the fixed oxygen meter being fitted close to its sampling point?
To protect it from heat.
To reduce the time between the sample being taken and analyzed.
The oxygen level rises as it passes along the sample line.
The oxygen level falls as it passes along the sample line.
Which of the following is the best definition for “inert gas”, as used to protect the cargo spaces of oil tankers?
It is a gas containing insufficient oxygen to support the combustion of hydrocarbons.
It is a gas containing no oxygen.
It is any gas containing less than 21 % by volume of oxygen.
It is a gas containing too much hydrocarbon vapor to support combustion.
Which of the following is the best explanation of the purpose of the scrubber unit in a flue gas type inert gas plant?
To cool the gas while removing soot particles and sulphur dioxide.
To prevent flue gas entering the plant while it is shut-down.
To cool the gas.
To remove moisture from the flue gas before being sent to the tanks.
Which of the following is the location that the gas regulating valve is required to be fitted to in inert gas systems on oil tankers?
The bulkhead, where the inert gas main passes from the gas safe area into the cargo area.
In the inert gas main forward of the deck seal.
Between the deck seal and the P/V valve.
At each of the blower outlets.
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 reduce evaporation of the cargo.
To cool the tank.
To prevent contamination 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?
4 to 5 %.
7 to 8 %.
9 to 10 %.
0,1 to 0,5 %.
Which of the following operations is carried out last when shutting down a typical flue gas plant?
Shut-down the scrubber water pump.
Open the ventilation valve to the atmosphere.
Close the gas regulation valve.
Close the boiler uptake valve.
Which one of the following automatically prevents excessive overpressure or vacuum in the inert gas main?
P/V Breaker.
Vent to the atmosphere valve.
Inert gas blower discharge valve.
Boiler uptake valve.
Which one of the following is a check that should be carried out on a P/V valve fitted to an inert gas deck main?
Check the liquid level when the system is at atmospheric pressure.
Check the liquid level when the system is running at full capacity.
Lubricate all linkages.
Open and close the valve every week.
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?
Soot build up.
Cracking.
Impeller corrosion.
Epoxy coating damage.
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 % and the “high-high” oxygen alarm sounds?
The inert gas blowers will stop and the plant is shut-down.
The gas regulating valve will automatically close, and the vent or recirculation valve will open.
The gas regulating valve and the boiler uptake valves will automatically close.
The boiler burners will shut-down.
Which one of the following is likely to occur if the flue gas temperature is too high at the blower outlet?
A fire might be started in the cargo tank.
The coating in the blower may be damaged.
The pressure control valves may stick.
The deck seal may empty.
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?
Low sulphur crude.
Static electricity.
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?
125 % in total.
110 % in total.
100 % in total.
100 % per blower.
Which one of the following should be done before starting up the flue gas plant?
Calibrate the fixed oxygen analyser.
Wash the blowers.
Close the uptake valves.
Turn off the deck seal pump.
Which one of the following would be the best gas to use to zero the fixed oxygen analyser monitoring an inert gas plant?
Nitrogen.
Methane.
Butane.
50/50 Methane/Butane mix.
Which one of the following would expect to happen if the blower on a flue gas plant tripped out overload?
The inert gas system will shut-down.
The other blower will start automatically.
The boiler will be tripped.
The blower’s inlet and outlet valves will automatically close.
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 shut-down automatically.
The inert gas recirculation valve automatically opens fully.
The inert gas blowers shut-down automatically.
The P/V valve will open fully.
Which one of the oxygen levels given in the options is the minimum level for the oxygen content in the output from a flue gas plant that you should take action to investigate why the oxygen content is not lower?
5 %.
1 %.
8 %.
11 %.
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?
Inerting.
Gas freeing.
Purging.
Topping up.
Which three of the given options are likely causes of high oxygen content indication on the oxygen analyser fitted to a flue gas plant?
Poor combustion control of the boiler.
Incorrect calibration of the oxygen analyser.
Drawing air down the boiler uptake during low load operation.
Low water flow in the scrubber.
Which two of the following are alarms that are normally found on a flue gas scrubber?
High water level.
Low water flow.
High gas inlet temperature.
High vibration.
Which two of the following are alarms that are normally found on an inert gas deck main?
High pressure.
Low pressure.
Low gas flow.
Low water flow.
Which two of the following are items that should be checked during the internal inspection of a flue gas scrubber?
Corrosion of shell.
Corrosion of sensors.
Corrosion of demister pads.
Blockage of overboard valve.

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Январь, 11, 2022 183 0
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