Multiple choice question for engineering
1. What is the role of breaker house in coal feeding?
a) To break the coal into smaller pieces
b) To separate different sizes of coal
c) To separate the light dust from the coal
d) To powder the coal
Answer: c [Reason:] Because of the brittle nature of the coal, it is a common nature of coal to emit light dust/coal dust during transportation, mining and machine handling. This dust needs to be cleared out and it is performed by coal breaker.
2. When coal is being burnt how much % of ash is formed compared to the whole amount?
Answer: a [Reason:] The coal available in nature already contains some percent of ash and when it is burnt. Due to its brittle nature more amount of ash is produced. And coal is one of the largest types of industrial waste generated. For environmental benefits this coal ash is reused as a type of by-product in different types of industries.
3. Why is it important to prefer ash handling systems?
a) Coal ash produced destroys the machineries by entering into them
b) Coal ash produced annually accounts for thousands of tones
c) Coal ash can be reutilized for some other purpose
d) Coal ash affects the health of people working at plants
Answer: b [Reason:] Considering the large coal burning capacity plant of modern times, the amount of ash produced when the coal is burnt is in thousands of tones. It could have an effect on other subjects too, if the proper ash handling methods are not followed. And for different environmental, economical and product benefits the coal ash is reused by different types of industries in different ways of its necessity.
4. Large amount of coal is transported by________
b) sea or river ways
c) road transportation
d) by airlifting
Answer: a [Reason:] The railway is preferred since it is quite economical as well as loading and unloading of coal is easy. And at stretch tons of coal can be transported by goods train from one place to another place. Coal is considered as a bulk commodity value which falls in category of minerals and ores. If roadways are preferred only minimal amount of load can be transported. But by railway, long distances with huge amount of coal can transported to any region/part of the country.
5. The coal is fed to the furnace through _________
a) conveyor belt
b) wagon tipper
Answer: c [Reason:] Hopper is the conical shaped slow coal dispenser to the furnace. It is placed right above the furnace and a live feeder mechanism is set at end of hopper for a controlled flow. There is no requirement of any external power/force since this works on gravity force.
6. Which system consumes less power out of all ash handling systems?
a) Mechanical ash handling system
b) Pneumatic ash handling system
c) Hydraulic ash handling system
d) Steam jet ash handling system
Answer: a [Reason:] The mechanical ash handling system consumes less amount of power. Since the power is required by the conveyor belt to transfer the ash from boiler furnace to over head bunker which is located at end of the conveyor belt. And in case of pneumatic there is high power requirement to draw and blow the air at high velocities and high pressures.
7. What is the function of cyclone separators in pneumatic ash handling system?
a) To separate the lighter dust particles
b) To force up the movement of ash through pipes or tubes
c) To draw out the dust from furnace
d) To separate minute coal particles
Answer: a [Reason:] Cyclone separators use air to swirl around the ash that has been dispensed into them. Due to centrifugal action heavier ash settles down, where as lighter dust/ash particles is collected in hopper and dumped out. The air flows in helical pattern which makes easy for the heavier dust particle to settle down easily without interrupting the airflow.
8. Which medium is used to carry ash in the pneumatic ash handling system?
a) Conveyor belt
b) Water trough
d) Chain belt
Answer: c [Reason:] In pneumatic ash handling system, Air is used to carry ash to long distance at a capacity of 5 to 30 tonnes per hour. And the air used for this purpose is easily cleanable and can be exhausted back into atmosphere after the complete filtration processes.
9. Which system is noisy out of all the following ash handling systems?
a) Steam jet ash handling system
b) Mechanical ash handling system
c) Pneumatic ash handling system
d) Hydraulic ash handling system
Answer: c [Reason:] The air is made to pass at a very high pressure in order to carry out the ash for long distance. Since the air is moving at high speed at high velocity in the conveying pipes, it tends to create lot of noise by hitting the walls of pipe at swift turns and curves.
10. Which medium is used to carry ash in hydraulic system?
Answer: b [Reason:] Water is used as the medium to carry ash at high velocity. Depending on water pressure the system is divided as Low pressure system and High pressure system. In low pressure system, sloped sumps are used to move the ash at low velocity and in high pressure system nozzle sprays used to ram up the speed of ash flow.
11. What would be the amount of distance that a low pressure system could carry the ash?
Answer: b [Reason:] Low pressure system moves the ash mixed in water at a distance of 3 to 5 m/s in a sloped pump made of reinforced constituents and this movement is continuous. So, it has ability to carry the ash for such long distance. There is no requirement any auxiliary source to move the ash mixed with water.
12. What is the capacity of low pressure hydraulic ash handling system?
a) 80 tonnes/hour
b) 22 tonnes/hour
c) 50 tonnes/hour
d) 10 tonnes/hour
Answer: c [Reason:] The capacity of low pressure hydraulic ash handling system is 50tonnes/hour at a speed of 3m/s. Since the ash produced is mixed in water and dumped, the water has ability to dissolve and intake more amount of ash. And this mixture is spread throughout the sump.
1. Open cooling system is also called as ____________
a) parallel system
b) once through system
c) air based system
d) non-reversible system
Answer: b [Reason:] Open system is also called as once through system , in this system the water is drawn directly from the upstream side of the river pumped through the condenser and discharged to the downstream side of the river at temperature 5 to 10oC in excess of inlet temperature.
2. How many number of spray nozzle does each module on spray pond cooling system contains?
Answer: 4 [Reason:] Modules in spray pond cooling system contain 4 spray nozzles. The surface area of contact of water is increased when it is sprayed in air. Cooling occurs due to the evaporation of water vapours as the spray propels upwards and falls down to the surface.
3. Which of the following is the simplest method of cooling the condenser water?
a) Spray cooling pond
b) Cooling tower
c) Indirect air cooling
d) Hyperbolic cooling tower
Answer: a [Reason:] Spray cooling pond is the simplest method of all. The hot water coming out of the condenser is sprayed through the nozzles to expose maximum surface area of water to air for effective cooling. The spray ponds are surrounded with wooden walls to prevent the wind from carrying the water particles.
4. In which type of cooling pond system are nozzles arranged on same elevation?
a) Single deck system
b) Double deck system
c) Natural Flow system
d) Direct flow system
Answer: a [Reason:] In a single deck system spray nozzles are arranged at the same elevation. Its effective cooling effect is less than double deck system. Hot water is sprayed through the spray nozzle in air. Cooling occurs due to the evaporation of water vapors at the spray propels and falls down the surface.
5. In which type of cooling system are nozzles arranged on different elevation?
a) Single deck system
b) Double deck system
c) Natural Flow system
d) Direct flow system
Answer: b [Reason:] In double system of cooling ponds the spray nozzles are arranged at different elevations. Cooling effect is more than single deck cooling system as water comes in contact with air at lower temperatures.
6. What are used in the direct flow system to transverse the pond before uniting at intake?
c) Baffle walls
d) Porous pipes
Answer: c [Reason:] In direct flow system the hot water coming out of the condenser enters the middle channel. On reaching the far end it is divided into two currents being directed by the baffle walls so as to transverse the pond several times before uniting at intake point.
7. Select the disadvantage of cooling pond out of the given?
a) The area required of cooling in a cooling pond is small
b) Spray losses due to evaporation and windage run high
c) There is no control over the temperature of cooled water
d) The cooling efficiency is low compared with cooling water
Answer: c [Reason:] The cooling effect is reduced with the decrease in wind velocity and if the load on the plant increases, the pond does not respond to the requirement. When the maximum cooling is required during increased load, it provides minimum cooling in absence of wind flow.
8. What type of cooling system is used in the large power plants?
a) Cooling ponds
b) Natural flow system
c) Cooling towers
d) Single deck system
Answer: c [Reason:] In large power plants cooling towers are used in the place of cooling ponds. A cooling tower is a wooden or metallic rectangular structure, with packed baffling devices. The hot water is delivered to the top of tower and is made to fall down the tower and is broken into small particles while passing over the baffling devices.
9. How does outside air enter into the wet cooling system?
a) Air vents
Answer: b [Reason:] Air and water are thoroughly mixed by fill as water splashes down from one fill level to the next due to gravity outside air enters the tower through louvers from the side of the tower. The heat and mass transfer between water and air is enhanced due to intimate mixing.
10. How is water circulated throughout the dry cooling tower system?
a) Finned tubes
b) Metal pipes
c) Porous tubes
d) Swirling tubes
Answer: a [Reason:] In dry cooling tower circulating water is passed through finned tubes over which cooling air is passed. Heat is rejected to air in the form of sensible heat. A dry cooling tower may be either natural draft type or forced draft type. These types are cheap than wet types of cooling tower.
11. Why is exhaust steam coming out of turbine is admitted to a steam header?
a) To increase the pressure
b) To decrease the velocity
c) To decrease the pressure drop
d) To control the pollution
Answer: c [Reason:] Exhaust steam from turbine is admitted to a steam header in order to minimize the pressure drop. Steam gets condensed as it passes down through the finned tubes arranged in parallel rows.
12. In which system is Cooling of hot water is done on tray as step by?
a) Mechanical draught cooling system
b) Hyperbolic cooling tower
c) Atmospheric cooling tower
d) Wet cooling tower
Answer: c [Reason:] In atmospheric cooling tower, the hot water is delivered at the top most trays and it falls down from one tray to another until it reaches the tank below the tower. The water is cooled by air flowing across the tower.
13. How does the flow of air occur in natural draught cooling towers?
a) Natural pressure head density between cold outside air and humid inside air
b) Variation in pressure of both cold outside air and humid inside air
c) Due to the given air vents and vacuum ports
d) Because of difference in the volume of both the of airs
Answer: a [Reason:] In natural draught cooling tower, the flow of air occurs due to the natural pressure head caused by density difference between the cold outside air and hot humid air inside. The disadvantage of natural draught cooling system is that, to produce to produce large draught the tower should be very high.
14. How is air produced in mechanical draught cooling tower?
a) Air Tuyeres
b) Propeller fans
c) Air blowers
Answer: b [Reason:] In mechanical draught cooling tower the draught of air id produced mechanically by means of propeller fans. This increases the cooling rate by increasing the air velocity over the wet surfaces and through the tower. These two towers give higher efficiency; reduce spray and windage losses and less ground area.
15. Why is induced draught considered better than the forced draught?
a) Because power requirement is high for forced draught
b) Maintenance of induced draught fan is costlier
c) Forced draught is less efficient
d) Forced draught produces less amount of speed of air
Answer: a [Reason:] Induced draught is considered to be better than forced draught because, the power requirement is high for forced draught and the maintenance of fan is costlier. The induced draught occupies less space ass the fan drives are placed at the top of the tower, the cooling effect is distributed across the entire cross section of the tower.
1. What type of draught fan is used to draw air from air heater?
a) Balanced draught fan
b) Induced draught fan
c) Forced draught fan
d) Artificial draught fan
Answer: c [Reason:] Forced draught fan is used to draw the air. This is installed near the base of boiler and air is forced to pass through the furnace, economizer and to the air stack. This is also called as positive draught system because pressure and air is forced to flow through the system.
2. In what form are the products of combustion in steam powered plant?
a) Air products
b) Flue gas
d) Hot water
Answer: b [Reason:] The products of combustion are in form of flue gas. Flue gas is the gas which is exiting to the atmosphere via a flue, which is channel for releasing exhaust gas from steam power plant. The flue gas is high in the contamination of nitrogen, oxygen and carbon dioxide. And also it contains a small amount of pollutants, such as soot and other types of oxides.
3. How flue gas is made use of in steam power plant?
a) To maintain the constant pressure inside boiler
b) To heat the water in the tubes of boiler
c) To increase or decrease the pressure inside the boiler
d) To remove all unnecessary chemical constituents
Answer: b [Reason:] The flue gases are circulated in the furnace to heat the water in tubes. First it is passed over economizer and then to the pre-heater. And the finally after making maximum utilization of the flue gas they are exhausted through chimneys.
4. How is flue gas discharged through the chimneys?
a) By using induced draught fan
b) By using balanced draught fan
c) By using forced draught fan
d) By using mechanical draught fan
Answer: a [Reason:] After extracting maximum possible heat by circulating the flue gas in furnace. Induce draught fan is used to remove the left over gas via chimney. This is located near the base of the chimney. The air is sucked in by reducing the pressure below atmosphere. The draught produced is independent of temperature of hot gases.
5. What is the purpose of chimney?
a) To provide air ventilation
b) To eliminate noise produced in the system
c) To exhaust flue gases those is induced
d) To help in to suck the air required for system
Answer: c [Reason:] Chimneys are actually used to remove exhaust gases or products of combustion by using induced draught system. Almost all chimneys are constructed by bricks vertically and at a certain height in order easily release flue gases into atmosphere. The height of the chimneys shows its ability to transfer flue gases. The deposits of flue gas contaminations are made on the inner walls of the chimney.
6. What is the advantage of using flue gas inside a boiler?
a) Heats up boiler water tube quickly
b) Reduces the amount of amount of exhaust
c) Speeds of the process of boiler
d) Reduces the green house of effect
Answer: d [Reason:] Using flue gas to heat up the water tubes reduces the greenhouse effect indirectly by making use of its heat to turn the water in water tubes into steam. This will be used in steam power plant to rotate the turbine and to produce electricity. And also plant operators can operate at best heat rate efficiency.
7. How is water pumped into condenser tubes in the steam power plant?
a) Water clarifier plant
b) Draught systems
c) Hydraulic capacity electric motor pump
d) Drawing through water
Answer: a [Reason:] The water is pumped into condenser tubes through water clarifier plant. Clarifier helps in suspending solids from water in order to avoid damages to condenser tubes. Clarifiers are available in wide varieties of capacities of capacities and shapes depending on the steam plant.
8. When is cooling tower preferred?
a) When there is plenty of water available
b) When there is scarcity of water
c) When the plant is of large capacity
d) When the amount of flue gas produced is very high
Answer: b [Reason:] Cooling tower is preferred when there is scarcity of water. Instead of circulating the water directly, it is sprinkled in the cooling tower to condense the exhausted steam coming from the turbine. The loss of water due to evaporation is compensated by supplying water directly from the river.
9. What type of system is it, when the water is directly is used to condense the steam?
a) Closed system
b) Open system
c) Closed loop system
d) Open loop system
Answer: b [Reason:] Water is pumped through the water clarifier plant and is used to circulate through the condenser in order to condense the steam coming out from the turbine. Water leaving the condenser is discharged to the downward side of the river. The amount of water in taken from river, the same amount of water is discharged back to river with the minimal temperature difference. And this following system is called open system.
10. How is the amount of cooling required by steam power plant determined?
a) By the capacity of plant
b) By the amount of exhausted gas
c) By its thermal efficiency
d) By the type of fuel used (coal or uranium)
Answer: c [Reason:] The amount of cooling required by the steam power plant is determined by its thermal efficiency. It has nothing to do whether it is fueled by coal or uranium; neither has it depended on the type of power plant (nuclear, thermal or hydel). Nuclear power plants have lower thermal efficiency than the thermal plants. Higher the thermal plants lower the water usage for cooling.
11. How much amount of water does typical 1GWe plant uses for cooling per day?
a) 30 mega litre
b) 45 mega litre
c) 55 mega litre
d) 75 mega litre
Answer: d [Reason:] Water is used in a plant to convert it into steam and utilize it for developing mechanical energy as well as it is used for the cooling of the steam produced. This water is supplied by the large water bodies like river or big lakes. The amount of utilized from water body is all discharged back at the end.
12. What type of system is it when the cooling tower is preferred?
a) Closed system
b) Open system
c) Closed loop system
d) Open loop system
Answer: a [Reason:] When there is scarcity of water a cooling tower is installed, such system is known as the closed system. In this system the condensed water is cooled by passing it through the cooling tower and water is sprinkled over steam. The loss of water due to evaporation is compensated by supply of water directly from the river.
13. What is the alternative cooling method for the thermal plant?
a) Wet cooling
b) Evaporation cooling
c) Dry cooling
d) Central air damping
Answer: c [Reason:] The alternative way of cooling method is dry cooling. Where in this method the heat is directly transferred to air via high flow forced drafts [industrial sized fans]. This is less efficient compared to wet cooling method since it uses very high amount of power to rotate the fans. Dry cooling method is very useful in the desert areas, where water scarcity is a huge problem.
14. How can we achieve high thermal efficiency in a power plant?
a) Drawing high output with limited input
b) Decreasing the working temperature
c) Increasing the working temperature
d) Maintain large temperature differential
Answer: d [Reason:] The amount of heat discharged to environment depends on the plants thermal efficiency. High efficiency is achieved by having a large temperature differential. Irrespective of whether it comes from high internal heat or low temperature external environment, or both. The thermal efficiency of today’s nuclear power plant is around 35% whereas hotter coal burners can reach 40% or more. At last higher thermal efficiency is required to lower the water usage.
1. What is the major problem in nuclear plants?
a) Drawing out energy
b) Fusion of particles
c) Disposal of nuclear waste
d) Handling of fuel
Answer: c [Reason:] One of the major problems in the nuclear power plant is the disposal of waste products which are highly radioactive. They emit large quantities of γrays and these high energy γ rays destroy all living matter through which pass.
2. A 400 MW nuclear power station would produce a equivalent radium of _____________
a) 100 tons daily
b) 1000 tons daily
c) 500 tons daily
d) 10 tons daily
Answer: a [Reason:] The radio-active products of a 400MW power station would be equivalent to 100 tons of radium daily and the radioactive effect of this plant product if exposed to atmosphere would kill all the living organisms within the area of about 100 sq miles.
3. How are moderate active solid wastes disposed?
a) Buried underground
b) Buried under sea
c) Sent to outer space
d) Left out in streams or rivers
Answer: a [Reason:] In a nuclear fuel cycle, the solid, liquid and gaseous radioactive wastes are produced at different stages. These radioactive wastes must be disposed off in such a manner that there is no hazard to the human and plant life. Moderate active solid wastes are buried in the ground.
4. Moderate liquid nuclear wastes are disposed into ___________
a) Deep pits
b) Buried underground
c) Left into rivers
d) Left into deep oceans
Answer: a [Reason:] Moderate liquid wastes after preliminary treatments are discharged in deep pits or day well from which they sweep out into the surrounding. Certainly liquid wastes are mixed with some kind of other chemical in order to lower their radioactivity.
5. Which type of disposal of nuclear waste is cheapest and easiest method of all?
Answer: a [Reason:] This is one of the easy and cheapest methods of disposal because soil absorbs radioactive material easily. This disposal is suitable mostly in areas of low rainfall at points which are high above the ground water level.
6. How are active liquids of nuclear waste disposed?
a) Stored in concrete tanks and buried underground
b) Stored in concrete tanks and buried in sea
c) Mixed with other chemicals and left into free atmosphere
d) They are reused and burnt away in gaseous fumes
Answer: a [Reason:] Active liquids are kept in concrete tanks and these tanks are buried in the ground till their decay of radio activity. Many times the radio activity increases the temperature of the liquid waste or sometimes these liquids boil and the activity decreases with time.
7. What are the ways in which most of radio activeness is removed?
a) Infusing them with other metal
b) Neutralizing them by diluting in chemical solutions
c) Storing them
d) Segregating them into small packs
Answer: c [Reason:] Most of the radio activeness of waste is removed just by storage. The storage problem is simplified by separating cersium and strontium which are extremely radioactive. These are generally stored in tanks which are buried in ground and then disposed in to the sea after 13 years of storage.
8. Can vacated coal mines be used for waste disposal?
Answer: a [Reason:] Yes, vacated coal mines can be used for waste disposal. The wastes are disposed in the salt heaps provided in the mines, because salt is a powerful absorber of radioactive emissions. It will be easy and more economical method to dispose of liquid waste by freezing.
9. How is High Level solidified nuclear wastes (HLW) stored?
a) Concrete tanks
c) Packed rock salt
d) Soil bins
Answer: b [Reason:] The solidified waste is placed in canisters that are stored in holes formation for thousands of years. The solidified waste is placed in canisters that are stored in holes drilled in rock salt with a spacing of 10 m to allow efficient dissipation of energy without exceeding temperature limits of either canister or salt. Each canister requires 100 m2
of salt for cooling.
10. What is the approx cost of disposing nuclear waste into sea per cubic meter?
a) 50 rs
b) 300 rs
c) 500 rs
d) 1000 rs
Answer: b [Reason:] In many places the liquid waste is disposed off to the sea through the pipes carried from the plant to the point of disposal. While disposing into the sea it should be seen that the activity level should not affect the marine life. The approximate cost of disposal by this method is 300 rs per cubic meter.
11. Absorption of radioactive element by human, affects their offspring’s.
Answer: a [Reason:] Absorption of neutron or radioactive element by a tissue nucleus leads to radioactive nucleus which results change in chemical nature, mal-functioning of cell. Due to this, cell damages leading to genetic modification. Inhale of radioactive material through air, food and water result radiation hazard.
12. For how many days is radioactive solid waste kept is kept under water at 6m deep for initial cooling?
a) 15 days
b) 50 days
c) 30 days
d) 100 days
Answer: d [Reason:] It is necessary to keep the radioactive solid waste first in the water of 6m depth nearly for 100 days. It was found that after 100 days cooling of radioactive waste of 28MW plant in water still has a radioactivity equal to million grams of radium. About 50% radioactive elements disappear during cooling.
13. What are released into biosphere from nuclear power plants?
a) Gaseous effluents
b) Waste Product
d) The obtained product
Answer: a [Reason:] Under normal operation, gaseous effluents are released slowly from the power plants into the biosphere and become diluted and dispersed harmlessly. Releasing at slow rates gives it time to blow of slowly.
14. Tailings forms are the residues from ____________
Answer: a [Reason:] Tailings are residues from uranium mining and milling operations. They contain low concentration of naturally occurring radioactive materials. They are generated in large volumes and are stored at the mine or mill sites.
15. LLW stands for ____________
a) Low Level Water
b) Low Laser width
c) Low Level Waste
d) Loss of Levels in water
Answer: c [Reason:] Low Level Waste contains less than 10 nCi per gram of transuranium contaminants containing low but potentially hazardous concentrations of radioactive materials. These are generated in almost all activities involving radioactive materials, require little or no shielding.
1. Why boiler draught is most essential part of the thermal plants?
a) Serves combustion by supplying ample amount of air
b) Helps in maintaining air ventilation
c) Required to maintain constant air flow
d) Stabilizes the boiler system
Answer: c [Reason:] Boiler draught is the difference of pressure required to maintain constant flow of air into the furnace and to discharge the flue gases to the atmosphere through a chimney. Thus boiler draught is one of the most essential systems of thermal plant. Boiler draught is generated by using chimney, fan, steam jet or air jet or combination of them.
2. Which is the correct formula of total draught loss?
a) Ht = Hv + Hb + Hc + Hcd
b) Ht = Hv + Hb – Hc + Hcd
c) Ht = Hv – Hb + Hc + Hcd
d) Ht = Hv – Hb – Hc – Hcd
Answer: a [Reason:] The total draught required to produce the current of the air and to expel the flue gases is given as follows.
Total draught loss = Velocity head loss at the chimney exit + fuel bed resistance + head loss in
Equipments like economizer, air heater etc. + head loss in chimney and ducts
i.e., Ht = Hv + Hb + Hc + Hcd
3. By what is natural draught produced?
a) Air duct
c) Locomotive exhaust
d) Air blower
Answer: b [Reason:] Natural draught is produced by using a chimney. A chimney is a vertical tubular structure made up of brick, steel or reinforced concrete. The draught produced by the chimney is due to the difference in temperature of hot flue gases inside the chimney and the atmospheric air.
4. Which of the following given below as the affect on amount natural draught?
a) Boiler operation
b) Size of the furnace
c) Grade of the fuel
d) Dust content in the fuel is used
Answer: a [Reason:] The draught produced in the chimney is due to the temperature difference of the hot flue gases. In addition to this, height of the above the furnaces grate, whether conditions and boiler operations also have considerable effect on the amount of natural draught.
5. When is artificial draught preferred?
a) When quick evacuation of flue gases is required
b) When we choose large power plant systems
c) When draught produced by chimney is not sufficient
d) When there are many components inside the boiler
Answer: c [Reason:] This type of draught is preferred when draught produced by the chimney is not sufficient or when a certain draught is to be maintained irrespective of atmospheric temperature. Artificial draught as no flexibility, as poor efficiency and requires tall chimney.
6. Artificial draught is also called as _______
a) Force draught
b) Induced draught
c) Balanced draught
d) Mechanical draught
Answer: d [Reason:] In modern high pressure boilers, use of economizers, super heaters, air pre heaters reduces the exit flue gas temperature considerably. This results in increased chimney height, whose cost is not justified. By using mechanical draught chimney height is considerably reduced.
7. What is installed to transfer air into furnace in forced draught system?
a) Air blower
c) Draft gauges
d) Cyclone separator
Answer: a [Reason:] In force draught system an air blower is installed near the boiler which blows into the furnace. The pressure of air throughout its path is above atmospheric pressure. This system also uses chimney to discharge hot flue gases into the atmosphere.
8. Where is blower installed in induced draught system?
a) Near the boiler
b) Base of the chimney
c) Above the boiler
d) Between economizer and air preheater
Answer: b [Reason:] In induced draught system the blower is installed near the base of the chimney so as to facilitate sucking of flue gas from the furnace. Thus pressure inside the furnace is reduced below atmospheric pressure inducing outside air into the furnace.
9. How can exhaust gas be recovered in the induced draught?
a) By installing the forced draught fan at the starting point
b) By extending the chimney’s height
c) By inletting high amount of air from multiple air ducts
d) By installing air preheater and economizer along the gas path
Answer: d [Reason:] The heat in exhaust gases can be recovered as much as possible by installing an air preheater and economizer along the gas flow path. As the draught produced in this system is independent of flue gas temperature care should be taken such that the fan handles gas at its lowest possible temperature.
10. Which is most preferred type of draught system?
a) Chimney draught
b) Fan draught
c) Force draught
d) Balanced draught
Answer: d [Reason:] A balanced draught system combines the features of forced draught and induced draught. In case of forced draught, when the furnace doors are opened high pressure air rushes outside and even blow out the fire entirely. In case of induced draught, when the furnace doors are opened to atmosphere air enters the furnace and causes imbalance in the draught. This difficulty is overcome by using balanced draught.
11. How pressure in the furnace is maintained below atmospheric pressure in balanced draught system?
a) By forced draught fan
b) By induced fan
c) Depends on the height of chimney
d) By installing Natural draught
Answer: b [Reason:] In balanced draught system, a forced draught fan is installed near the boiler which helps in overcoming the resistance of fuel bed by supplying sufficient air for combustion. An induced draught fan is installed near the chimney base removes the flue gases coming from the furnace and maintains pressure in the furnace slightly below the atmospheric pressure.
12. Which type of draught system is used in the locomotives?
a) Natural draught system
b) Balanced draught system
c) Forced draught system
d) Induced Steam draught system
Answer: d [Reason:] Induced steam draught system is used in a boiler for a locomotive. When the locomotive is stationary steam generated in the boiler is fed to the smoke box through the nozzle to create the draught. When locomotive is moving air enters through the dampers and makes its way through grate and smoke box.
13. Which draught system is also known as turbine draught?
a) Forced steam draught
b) Induced steam draught
c) Natural draught
d) Fan draught
Answer: a [Reason:] Forced steam draught system is also is known as turbine draught. In this case, steam from the boiler is throttled to a pressure of 1.5 to 2 bar and passed through a series of nozzles fitted to a diffuser pipe.
14. Which draught system is used as conjunction with chimney draught?
a) Forced steam draught
b) Forced draught
c) Induced draught
d) Balanced draught
Answer: a [Reason:] The high velocity steam coming out from the nozzle drags the air column along with it creating suction. The kinetic energy of air and steam mixture is converted into pressure energy forcing air through the coal bed to the furnace. So, Forced steam draught is used as a booster in conjunction with chimney draught.