This set of Energy Engineering Multiple Choice Questions & Answers focuses on “Boiler Mounting Accessories – 2”.
1. Which of the following is an example of reciprocating pump?
a) Lobe pump
b) Barrel pump
c) Vane pump
d) Hand pump
Explanation: Hand pump is the example of a reciprocating pump. Reciprocating pumps when made use inside a boiler. They are continuously run by steam from the same boiler to which the water is fed. Water is pumped by reciprocating action.
2. When is it difficult to maintain the pressure inside the boiler?
a) When steam demand is fluctuating
b) When steam demand is high
c) When steam demand is low
d) When steam demand is constant
Explanation: Whenever the steam demand is fluctuating, it becomes very difficult to maintain uniform pressure. In such of these cases pressure reducing valve is made utilized by connecting to steam supply line. Function of the pressure reducing valve is to maintain constant pressure on the delivery side of the valve with the fluctuating boiler pressure.
3. How many types of steam traps are generally used in the boiler?
Explanation: Two types of steam traps are generally used in the boiler. The function of steam trap is to drain off water resulting from the partial condensation of steam in the steam pipe lines and jackets without allowing the steam to escape through it.
4. Where is steam separator installed in the boiler?
a) Close to the engine
b) Close to the economizer
c) Close air preheater
d) Near to the superheater
Explanation: Function of the steam separator is to separate the water particles in suspension that are carried by the steam coming from the boiler. It is always installed as close to the engine or turbine as possible on the main pipeline.
5. Which materials are used for Super heater tubes?
a) Nickel chromium
c) Chromium Molybdenum
Explanation: Superheater is made of coils of tubes forming parallel tube circuits connected between heaters. The superheater tubes are made of high temperature strengths special alloy steels such of chromium molybdenum. The coils are heated by the heat of combustion gas during their passage from furnace to the chimney.
6. Super heaters are commonly classified into how many types?
Explanation: Super heaters are commonly classified into two types: Radiant superheater and convective superheater. If superheater absorbs heat from the burning fuel through radiation than it is known as Radiant Superheater. If the superheater that receives its heat entirely from the gases through convective heat transfer is called Convective superheater.
7. How many methods of superheater temperature control are there?
Explanation: There are eight methods of superheater temperature control. They are:
8. In the method of ‘Tilting burners in the furnace’ at what degree are the burners tilted?
Explanation: In this following method of a superheater temperature control burners in the furnace are tilted up or down through a range of 30o. When burners are tilted downwards much of heat is given to the water walls by the gas and the gas entering the super heater region is relatively cool.
9. What is the function of Re-heater in the boiler?
a) To get excess amount of heat
b) To make utilize of the left over water in the tubes
c) Re-super heat partly expanded steam
d) Better heating efficiency in winters
Explanation: The function of Re-heater is to re-superheat the partly expanded steam from the turbine so that the steam remains dry as far as possible through the last stage of turbine. Modern plants have reheaters as well as super heaters in the same gas passage of the boiler.
10. How many types of economizers are there?
Explanation: There are six types of economizers:
11. Which is the most common type of economizer used in the thermal plants?
Explanation: The most common type of economizer used in thermal power plant is the Non-condensing thermal power plant. They are Heat exchanger tubes with fins around the in the form of spiral and they are located inside the duct at the exit region of the boiler.
12. Which type of economizer is used in Natural gas fired thermal plant?
Explanation: Condensing economizers are used in natural gas fired thermal power plant. They reduced the flue gas temperature below condensation temperature as low as 25oC. They increase the boiler efficiency by 10-15%. While using the condenser the fuel should not contain sulfur.
13. Select the benefit of preheating the air?
a) Increased thermal efficiency
b) Improved oxidation
c) Controlled steam capacity
d) Decreased power consumption
Explanation: Increased thermal efficiency is one of the benefits and also other benefits are
i) Improved combustion
ii) Efficient use of low grade fuel
iii) Saving in fuel consumption
iv) Increased steam generation capacity.
14. Which type of air heater consists of a bunch of hollow leaves of sheet metal?
a) Plate air heater
b) Tubular air preheater
Explanation: The plate type air heater consist a bunch of hollow leaves of sheet metal electrically welded and assembled in housing. The spacing between the adjustment leaves and the width of the opening of leaves are such that air and gas passages are of different widths.
15. Which type of air preheater is often preferred at thermal stations?
a) Regenerative heater
b) Tubular air heater
c) Plate air heater
d) Integral heater
Explanation: In the regenerative heater same surface is alternately heated and cooled by the air and gas steams through respective operating cycles. These are often preferred in thermal station due to its compactness, accessibility and reduced weight.
Sanfoundry Global Education & Learning Series – Energy Engineering.
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