BOILER THEORETICAL QUESTION 1 . Define a boiler and steam generated unit . y
y
A boiler is a container into which is fed, and by application of heat , water evaporators continuously into steam . A boiler also can define as a closed vessel where water or some other liquid is heated.
2 . State the use of steam produced by the boiler . y y y
Economizer used to heat water being fed to the vessel Super heaters used for heating steam Any pipes and fittings connected
3 . List the primary requirements of steam boiler . y
y y
For
generating power in steam turbines. In the textile industries for sizing and bleaching . For power plant .
4. How are boiler classified ? y y y y y y
Horizontal, Horizontal, vertical ve rtical or inclined Fire tube and water tube Externally fire and internally fire Forced calculation and natural calculation High preasure and low preasure boiler . Stationary and portable .
5 . Give the comparison between ¶fire tube· and ¶water tube· boiler .
1.
PARTICULARS
FIRE
TUBE BOILER
Position Positio n of water and hot gases.
Hot gases inside the tubes and water
WATER TUBE BOILER Water inside the tubes and hot gases
2.
Made of firing
3.
Operating pressure
4. 5.
Rate of steam production Suitability
6.
Risk on bursting
7.
Floor
8. 9. 10 . 11 . 12 . 13 .
Construction Transportation Shell diameter
outside the tubes.
outside the tubes.
Generally internally fired. Operating pressure limited to 16 bar.
Externally fired.
Lower
Can work under as high pressure as 100 bar. Higher
Chances of explasion
Not suitable for large power plants. Involves lesser risk on explosion due to lower pressure. For a given power it occupies more floor area. Difficult Difficult Large for same power. Less
Suitable for large power plants. Involves more risk on bursting due to high pressure. For given power it occupies less floor area. Simple Simple Small for same power. More
Treatment of water
Not so necessary
More necessary
Accessibility of various parts
Various parts not so easily accessible for cleaning,repair and inspection. Require less skill for efficient and economic working
Various parts are more accessible
area
14 Requirement of skill .
Require more skill and carefull attention
6 . State the differences between the following boilers . External Fire The boiler is known as externally fired if the fire outside the shell
Forced
Internal Fire Internally fired boilers , the furnace is located insides the boiler shell.
circulation In forced circulations type of boilers , the circulation of water is done by a pump .
Natural circulation In natural circulation type of boilers ,circulations of water in the boiler takes place due to natural convection currents produced by the applications of heat.
External Fire The boiler is known as externally fired if the fire outside the shell
Internal Fire Internally fired boilers , the furnace is located insides the boiler shell.
High Pressure The boiler which produce steam at pressure of 80 bar and above are called high preasure boiler .
Low pressure The boiler which produced steam at preasure below of 80 bar are called low preasure boilers .
7 .Enumerate the factor which should considered while selecting a boiler . The boiler should : y
y y
Realatively inexpensive Easy to clean Compact in size
y y
Easy to replace tube Well suited for industrial application
8 . Explain with the help of neat diagrams any two of the following boilers . y
Scotch boiler
y
Simple vertical boiler
9 . What is the function of the boiler mounting ? can a boiler work without mounting ? y
y
Are defined as devices that are attached directly to the boiler so that the boiler can be operated safely . Without mounting boiler cannot work because cannot operated safely.
10 . How do accessories differ from mounting ? y
y
Accessories ~boiler accessories are use to recover energy and mark boiler function more efficiently Mounting ~mounting defined as devices that are attached directly to the boiler can be operates safely .
11 . Enumerate the various accessories normally used in steam generating plant . y y y
Economizer Air-preheater Super heater
12 .What is the function of safety valve ? state the minimum number of safety valve to be used on a boiler ? y
y
Safety valves or pressure safety valves are pressure-release mechanisms used in pressure vessels, boilers and other systems. Two safety valve are fitted to each boiler.
13 . What is a fusible plug and state where it is located in a boiler ? y
y
To extinguish fire in the event of water level in the boiler shell falling below a certain specific limit . it·s protect fire tube from burning when the level of the water fall abnormally low . It is installes below water level.
14 . Describes with the help of sketch the construction and working of a simple vertical boiler ? The vertical boiler is a simple type which consists of a firebox at the bottom and a copper barrel with a smoke tube. It typically is used to drive stationary engines and boats. Firing is accomplished by alcohol or solid fuel pellets. More sophisticated versions of the vertical boiler contain many small tubes and are sometimes fired by coal or charcoal.
15 . Why are water tube kept inclined in Babcock and Wilcox boiler ? y
Babcock and Wilcox boiler with longitudinal drum . It consists of a drum connected to a series of front end and rear and header by short riser tubes . To these headers are connected a series of inclined water tube of solid drawn mild steel . The angle of inclination of the water tubes to the horizontal .
16 . Distinguish between the mounting and accessory fitted in a boiler .Explain with sketch any two type of the boiler accessories . y
y
Accessories ~boiler accessories are use to recover energy and mark boiler function more efficiently Mounting ~mounting defined as devices that are attached directly to the boiler can be operates safely .
~AIR-PREHEATER y
The function of the pre-heatr is to increase the temperature of air before it enter the furnace . It is generally placed after the economizer ; so the flue gases pases through the economizer and then to the air preheated .
~ECONOMIZERS y
An economizer is a device in which the waste heat of the flue gases is utilized for heating the feed water .
17 . Distinguish between the mounting and accessory fitted in a boiler .Explain with sketch any two type of the boiler accessories . 18 . Name all mounting and accessories of a steam boiler and describes an economizer . Mounting : y y y
y y
Gauge glass Safety and relief valve Pressure gauge Blow down valve Fusible plugs
y y
y y
Main steam stop valve Feed check valve Boiler feed water regulator Chemical dosing valve
Accessories : y y
y
Economizes Air ² preheater Super heater
Economizers : ~ An economizer is a device in which the waste heat of the flue gases is utilized for heating the feed water . 19 .What is the function of boiler mounting ? can a boiler work without mounting ? Explain the sketches any two boiler mounting . y
y
Are defined as devices that are attached directly to the boiler so that the boiler can be operated safely . Without mounting boiler cannot work because cannot operated safely.
SAFETY AND RELIEF VALVE ~ Is mounted to prevent the pressure in the boiler from exceeding its maximum allowable working pressure. ~Mechanical device use protecting the boiler against overpressure
FUSIBLE
PLUG
~To extinguish fire in the event of water level in the boiler shell falling below a certain specific limit . ~it·s protect fire tube from burning when the level of the water falls abnormally low.
20 . What do you mean by evaporative of a boiler ? How is it expressed ? Define and explain equivalent evaporation . y
The process by which any substance is converted from a liquid state into and carried off in vapour as the evaporation of water of eather of camphor . the transformation of a portion of a fluid into vapour in order to obtain the fixed matter contained in it in a state of greater consistence .
