This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of High Pressure Boilers – 1”.
1. What type of boiler is a Lamont boiler?
a) Forced circulation
b) Natural circulation
d) Positive forced circulation
Explanation: A Lamont boiler is a forced circulation water tube boiler. In which the boiler water is circulated through an external pump through long closely spaced tubes of small diameters. The mechanical pump is employed to get an adequate and positive circulation in steam and hot water boilers.
2. What is called as the heart of the Lamont boiler?
a) Water drum
b) Centrifugal pump
Explanation: A centrifugal pump which forms the heart of the Lamont boiler is responsible to circulate water within the boiler system. It receives water from the drum and delivers it to the distribution header. The numbers of headers may differ in numbers and depends on the size and design of each boiler.
3. Through what is feed water from hot-well is passed through, before entering steam and water drum in Lamont boiler?
a) Evaporator tubes
c) Distributer header
d) Circulating pump
Explanation: Feed water from the hot well is passed through the economizer tubes before entering the steam and water drum. During its flow through the economizer tubes, water gains maximum sensible heat from the flue gases escaping to the exhaust.
4. In what form are the boiler’s tube arrange in Lamont boiler?
a) parallel in Vertical
b) Inclined vertically
c) parallel in horizontal
d) Horizontally inclined
Explanation: The boiler heating surface includes a number of tubes arranged in a parallel form and the inlet ends are welded to the distributors or the headers. A circulation pressure is to be provided during the installation of the pump as per the boiler design and it should be sufficient to overcome the resistance offered by the tubes.
5. Through which does the even circulation of feed water is possible in Lamont boiler?
b) Water trough
c) Feed pump
Explanation: An even circulation of feed water in Lamont boiler takes place with the help of nozzles provided at the inlet of the tubes which create the differential pressure adequate to cover the variations occurring at fluctuating loads or uneven firing conditions.
6. What is the pressure range between which Lamont boilers operates?
Explanation: The Lamont boiler operates between the pressure range of 120-160bar, due to this natural circulation is limited because of density difference between the liquid and vapor. Hence the external centrifugal pump is used to assist the circulation.
7. In which year was Lamont boiler invented?
Explanation: The Lamont boiler was invented by Walter Douglas Lamont in year 1925; He bought the idea from papers to existence. He also introduced the concept of forced circulation boiler. The initial design of Lamont for this boiler confirmed lighter, safer and higher rates of heat transfer.
8. What type of steam is generated by evaporator tube of Lamont boiler?
a) Saturated steam
b) Unsaturated steam
c) Superheated steam
d) Flash steam
Explanation: The steam generated by the evaporator tube of the Lamont boiler is saturated steam. If it is directly used in steam turbine, it can cause the corrosion. So the saturated steam sends to the super heater where it increases the temperature of steam.
9. Where is water steam separator drum located in Lamont boiler?
a) Inside of the boiler
b) Right above the furnace
c) Before the feed water pump
d) Outside of boiler
Explanation: The steam separator is situated outside of the boiler. In this the mixture of water and steam from the evaporator tube is sent, where it separates the steam and sends it to the super heater. The remaining water is again sent to the economizer.
10. What is the main disadvantage of Lamont boiler?
a) Less flexible in design
b) Low heat transfer rate
c) Formation of bubbles
d) Low steam generation capacity
Explanation: The main disadvantage of Lamont boiler is the formation of bubbles. These bubbles come in contact with the inner surface of the heating tubes and subsequently are attached to it. The bubbles attached to the tube surface have higher thermal resistance and consequently reduce the heat flow and steam generation.
11. In which year was Benson boiler was invented?
Explanation: Benson boiler is high pressure, drum less, water tube boiler with forced circulation. This was invented by Mark Benson in year 1922. It was Mark Benson who first proposed the idea to compress the water eat supercritical pressure before heating in boiler.
12. What type of boiler is a Benson boiler?
a) Super critical boiler
b) Fire tube boiler
c) Natural circulation boiler
d) Over-through boiler
Explanation: Benson boiler is a super critical boiler with pressure range of 225bar to 500bar in which the feed water is compressed to a supercritical pressure and this eliminates the formation of bubbles completely, bubbles do not form because at supercritical pressure the density of water and steam becomes same.
13. What is the capacity of Benson boiler?
a) 180 tonnes/hr & above
b) 150 tonnes/hr & above
c) 250 tonnes/hr & above
d) 300 tonnes/hr & above
Explanation: Feed water from the hot-well is forced through the economizer tubes. The hot water enters the radiant section of the evaporator tubs and then passes through convective section of the evaporator tubes. Since the boiler has no drum, thee steam generated in the evaporator enters the super heater tube where it is heated above the critical pressure. So the Steam rising capacity of the boiler is 150 tonnes/hr & above.
14. What is the major disadvantage of the Benson boilers?
a) Boiler is big in size
b) Has large storage capacity
c) Deposition of salts
d) Bubble formation
Explanation: The major disadvantage of the Benson boiler is that when water transforms into steam in the convective section of the evaporator, salts are deposited in the transformation zone. Hence periodic flashing of evaporator tubes in the convective section is necessary.
15. Why starting valve is closed and valve 2 is opened while taking boiler on range in Benson boiler?
a) Avoid excessive heating of tube
b) To maintain the constant flow of water
c) To avoid pressure built up in tubes
d) To avoid pipe leakages at joints
Explanation: The boiler is started from cold by circulating the feed water from the hot well by operating the starting valve. While taking the boiler on range, starting valve is closed and valve 2 is opened. This method avoids excessive heating of tubes.
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