04-06-2013, 11:23 AM
Steam Generator
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DEFINATION:
A steam boiler or generator may be defind as a closed vassel in which steam is produce from water by the combustion of fuel.
It is made up off steel.
The steam generator employed for the following purposes:
For generating power in steam engines, steam turbines.
The steam is used in Indiustries likes, sugar mills, textiles industries, chemical industries.
For heating the building in cold weather for producing hot water for hot water supplied.
CLASIFICATION OF STEAM GENERATOR OR BOILER:-
Through there are many classifications of steam boilers.
1. According to the contents in the tube.
2. According to the position of the furnance.
3. According to the any of the shell.
4. According to the number of tube.
5. According to the method of circulation of water and steam.
According to the Contents in the tube:
The steam generator is classified in to two types.
a. Fire tube boiler
b. Water tube boiler
a. Fire tube boiler: In the fire tube boiler the hot gases or fuel gases are inside the tube and the water surrounded the tubes.
Example:- Cochran boiler, Lancashire boiler, cornish boiler, Locomotive boiler etc.
b. Water tube boiler: In the water tube boiler the water is inside the bubes & the hot gases surrounded them.
Example:- Babcock & willcox boiler, stirling boiler, La-mont boiler, etc.
FIRE TUBE BOILER:
A fire tube boiler is so named because the products of combustion pass through its tubes which are surrounded by water.
This type of boiler are used in earlier days. How even they are steam used in small industrial plant to produes steam at the upper limits of about 18 bar pressure6.2Kg/Sec. steaming capacities.
Example:- Cocharam boiler
BOILER MOUNTING AND ACCESSORIES:-
Boiler Mounting:
These are different filling and devices which are mounted over boiler shell for its proper operation and safety of a boiler.
According to Indian boiler regulation follwowing mountiong should be fitted to boiler.
1. 2 safety valve
2. 2 water level indicators
3. A pressure gauge
4. A stem stp[ va;ve
5. A feed cjecl va;ve
6. A b;pw pf c;cl
7. Fusible plug
Safety Valve:
The function of safety valve is to release the excess steam when the pressure of steam inside the boiler exceeds the rated pressure. As soon as the pressure of steam inside the boiler exceeds the rated pressure, the safety valve automatically opened and excess steam escape in to the atmosphere, still the pressure down to the normal valve. It is mounted on the top of the shell.
The various types of safety valves are.
a. Lever type safety valve.
b. Dead weight safety valve.
c. High steam and low water safety valve.
d. Spring loaded safety valve.