DME-II_Thermal Engineering-II_Boiler-III

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The boiler mountings and accessories that are installed on the steam boiler are as follows

q Boiler Mountings
1. Water level indicator ( Water level gauge)
2. Pressure gauge
3. Safety valves
4. Stop valve
5. Blow off Valve
6. Feed check valve
q Boiler Accessories
1. Air pre-heater
2. Super heater
3. Economiser
4. Feed pump

The function of various boiler mountings and accessories are:

Boiler Mounting: 

Boiler mountings are the safety devices which are fitted on the boiler for its safe and efficient working.

1. Water Level Indicator

   •It is fitted in front of the boiler and generally present two in number.
   •It is used to indicate the water level inside the boiler. It shows the instantaneous level of water that is present inside the steam boiler which is necessary for its proper working.

2. Pressure gauge

   •It is also present in front of the boiler.
   •It is used to measure the pressure of the steam inside the boiler.
   •The pressure gauges generally used are of Bourden type
3. Safety Valves
    •Safety valves are attached to the steam boiler chest.
    •It is used to prevent explosion due to excessive internal pressure. When the internal pressure inside the boiler exceeds its working pressures than the safety valves blow off the steam and maintains the internal pressure.
     •Generally two safety valves are present on a boiler.
4. Stop Valve (steam stop valve)
It is usually fitted on the highest part of the boiler with the help of a flange.
•The main function of the stop valve is
•To control the flow of steam from the boiler to the main steam pipe.
•To completely shut off the steam supply when required.

5. Blow Off Valve

    •It is fitted at the bottom of the boiler drum.
    •The functions of blow-off Valve is
        a)To empty the boiler whenever required.
        b)To discharge the scale, mud and sediments which gets collected at the bottom of the boiler.

6. Feed Check Valve

    •It is non-return valve and fitted to a screwed spindle to regulate the lift.
    •It is fitted to the shell slightly below the normal water level of the boiler. A boiler must have its spindle lifted before the pump is started.
    •It regulates the supply of water which is pumped into the boiler by feed pump.
7. Fusible Plug
     •It is fitted to the crown plate of the furnace or firebox.
     •Its function is to extinguish fire in the furnace when the water level in the boiler falls to an unsafe limit. This avoids the explosion that may take place because of the overheating of the furnace plate.

Boiler accessories: 

The boiler accessories are the integral parts of the boiler. They are used in the boiler to improve its efficiency.

   q1. Air preheater

•It is used to recover heat from the exhaust gases.
•It is installed between the economiser and the chimney.

q2. Superheater

•It is placed in the path of hot flue gases from the furnace.
•A superheater is an important accessory used in the boiler. Its main function is to increase the temperature of saturated steam without raising its pressure.

q3. Economiser

•It is used to heat the feed water by the utilization of heat from the hot fuel gases before it leaves the chimney.
•A economiser improves the economy of the steam boilers.

q4. Feed pump

•It is used to deliver water to the boiler

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