This set of Thermal Engineering Interview Questions and Answers focuses on “Steam Generators – Fire Tube Boilers – 2”.
1. Which of the following is the correct range of the diameter of shell for a Lancashire boiler?
a) 1 to 2 m
b) 2 to 3 m
c) 3 to 4 m
d) 4 to 5 m
Explanation: The diameter of shell for a Lancashire boiler is 2 to 3 m. The length of shell lies in the range of 7 to 9 m. The shell of Lancashire boiler is placed horizontally over a brickwork. The shell is created using a number of rings of cylindrical form.
2. Which of the following statements is TRUE about Lancashire boiler?
a) The length of its shell is about 10 m
b) It has a steam capacity of 12000 kg/hr
c) It is a water tube boiler
d) Its efficiency is about 50 to 70%
Explanation: The efficiency of Lancashire boiler lies in the range of 50 to 70%. The length of the boiler shell is 7 to 9 m and its diameter ranges from 2 to 3 m. Lancashire boiler has a steam capacity of 9000 kg/hr. It is a fire tube boiler.
3. What is the maximum working pressure of a Lancashire boiler?
a) 10 bar
b) 12 bar
c) 14 bar
d) 16 bar
Explanation: The maximum working pressure of a Lancashire boiler is 16 bar. Its steam capacity is 9000 kg/hr and has an efficiency of 50 to 70%. Lancashire boiler is easy to operate and has low maintenance cost.
4. In Lancashire boiler, an arrangement is made so that burning coal and ashes do not enter the furnace tubes. What is that arrangement called?
a) Low brickwork fire bridge
c) Filtering mesh
d) Furnace separator
Explanation: Furnace is placed at the front end of the furnace tubes. The burning coal and ashes can get in the furnace tubes, hence a low brickwork fire bridge is placed at the back of the gate avert the entry of ashes and burning coal.
5. How many fire tubes (Furnace tubes) does a Lancashire boiler has?
Explanation: Lancashire boiler has two tubes also called as furnace tubes inside the cylindrical shell. These tubes are constructed with several rings of cylindrical form. They are covered all around with water and carry hot gases coming from the furnace.
6. What is the function of dampers in Lancashire boiler?
a) They control the flow of hot gases to the chimney
b) They regulate the fire in the furnace
c) They control the flow water to the boiler
d) They control the steam going out of the boiler
Explanation: In case of Lancashire boilers, the flow of hot gases is controlled by dampers. The flow of water to the boiler is controlled by feed check valve. Steam stop valve controls the flow of steam leaving the boiler.
7. The efficiency of Locomotive boiler is around _____
Explanation: The efficiency of Locomotive boiler is 70%. The presence of superheater in the Locomotive boiler increases the efficiency. The placement of superheater tubes is done in the fire tubes with larger diameter.
8. What is the steam capacity of a Locomotive boiler?
a) 3000 kg/hr
b) 5000 kg/hr
c) 7000 kg/hr
d) 9000 kg/hr
Explanation: The steam capacity of a Locomotive boiler is 9000 kg/hr. It has an efficiency of 70%. The coal burning rate is 1600 kg/hr. It is a type of fire-tube boiler.
9. What is the working pressure of a Locomotive boiler?
a) 12 bar
b) 14 bar
c) 16 bar
d) 18 bar
Explanation: The working pressure of a locomotive boiler is 14 bar. Locomotive boilers are generally used in locomotives but may be used as stationary boilers also. Locomotive boilers are small in size but they have high steam generation capacity.
10. In locomotive boiler, why natural draught cannot be obtained?
a) The chimney height required is too low
b) The boiler keeps moving, cannot maintain a constant pressure difference
c) The chimney height required is too high
d) The diameter of chimney required is impractical
Explanation: Natural draught in locomotive boilers cannot be maintained because the chimney height required is too high and it is difficult to make provision of such a high chimney since the boiler has to run on rails.
11. Which of the following statements is FALSE about a Locomotive boiler?
a) It has high steam capacity
b) It is portable
c) Scale formation and corrosion could take place
d) Water spaces can be cleaned easily
Explanation: There are some water spaces that cannot be cleaned properly. A Locomotive boiler has high steam capacity, portable, compact and has low installation cost. It is not bestowed with high overloads due to overheating damage.
12. In case of Locomotive boilers, what purpose the dampers serve?
a) They control the flow of air to grate
b) They control the flow of hot gases
c) They control the flow of steam leaving the boiler
d) They reduce the intensity of fire, if needed
Explanation: In case of Locomotive boilers, dampers are used to control air flow to the grate. Hot gases produced in the fire-box pass though the tubes and reach the smoke box where they are released to the atmosphere through the chimney. In Lancashire boiler, dampers are used to control the flow of hot gases.
13. In Locomotive boilers, the superheater tubes are placed inside the fire tubes.
Explanation: Presence of superheater increases the efficiency of the Locomotive boiler. The superheater tubes are placed inside fire tubes having larger diameter. The efficiency of a Locomotive boiler is 70%.
14. Which of the following statements is FALSE about steam dome in Locomotive boilers?
a) It is located at the upper part of the barrel
b) It has a regulator to regulate the steam flow
c) It is the chamber to collect the steam produced
d) From steam dome, the steam flows into the chamber through a steam pipe
Explanation: Steam dome is located at the upper portion of the barrel. It has a dome shape, hence its name. From steam dome the steam is passes through a steam pipe and it ultimately reaches the chamber. There is a regulator to regulate the steam flow from the steam dome.
15. When the locomotive is at rest, there is no exhaust steam available. So, fresh steam from the boiler is used as exhaust steam.
Explanation: Fresh steam is used as exhaust steam when the locomotive is at rest. The locomotive boiler has a high steam capacity. Natural draught cannot be obtained in these boilers because the chimney height required is too high and the boiler has to be kept mobile.
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