3. INTRODUCTION
A boiler is a closed vessel in which water or other fluid is
heated. The heated or vaporized fluid exits the boiler for
use in various processes or heating applications.
Instrumentation and controls in a boiler plant encompass
an enormous range of equipment from simple industrial
plant to the complex in the large utility station.
The boiler control system is the means by which the
balance of energy & mass into and out of the boiler are
achieved. Inputs are fuel, combustion air, atomizing air or
steam &feed water. Of these, fuel is the major energy input.
Combustion air is the major mass input. Outputs are
steam, flue gas, blow down, radiation & soot blowing.
5. Fire tube boiler
Here, water partially fills a boiler barrel with a small volume
left above to accommodate the steam (steam space).
This is the type of boiler used in nearly all steam locomotives.
The heat source is inside a furnace or firebox that has to be kept
permanently surrounded by the water in order to maintain the
temperature of the heating surface just below boiling point.
7. Water tube boiler
In this type, the water tubes are arranged inside a furnace
in a number of possible configurations:
often the water tubes connect large drums, the lower ones
containing water and the upper ones, steam and water; in
other cases, such as a mono tube boiler, water is circulated
by a pump through a succession of coils.
10. - High temperature resistant optical system consists of quartz and
corundum, which can be normally operated in a certain amount of purging
air.
- Screen menu setting, remote control in central control room, for forward and
retract movement of camera.
- Horizontal mounting and large field angle probe
- System is equipped with automatic forward and backward protection
device, which can automatically withdraw from furnace when no pressure in
cooling air.
Furnace TV :
11. FLOW METER
The flow meter is designed to measure flow rate of a fluid.
Measurement is based on Faraday’s law of
induction, according to which a voltage is induced in an
electrically conductive body which passes through a
magnetic field.
The following expression is applicable to the voltage.
U = K * B * V * D
Where:
U = induced voltage
K = an instrument constant
B = magnetic field strength
V = mean velocity
D = pipe diameter
13. BLOCK DIAGRAM DESCRIPTION
The block diagram of boiler control is shown in above
figure the output from the boiler i.e, the steam outputs and
the level of water is given to transmitters.
The major loops in boiler control are
1) Combustion control
2) Feed water control
14. COMBUSTION CONTROL
A combustion control system is broken down into
(a) fuel control and
(b) combustion air control subsystems.
15. HARDWARES USED IN COMBUSTION CONTROL
ON/OFF controls
Positioning systems
Metering control system
16. FEED WATER CONTROL
Feed water control is the regulation of water to the boiler
drum. It provide a mass accounting system for steam
leading and feed water entering the boiler.
Proper boiler operation requires that the level of water in
the steam drum should be maintained within certain band.
A decrease in this level may uncover boiler tubes, allowing
them to become overheated.
17. Levelling Vessel Level Control by-
Feed Water Control
BCP
CV to 1st stage DSH water Drain CVs to
Condensor
From Separator-B
BCP Discharge
CV to Eco. I/L
Levelling Vessel
From Separator-A
Drain CVs to
OAC/Waste
18. ADVANTAGES
Multiple element feedwater control can help:
i. Faster response of systems.
ii. More accurate control.
iii. Maximum system stability.
Metering control system maintains combustion efficiency
over wide load changes and over long period of time.
19. DISADVANTAGES
Boilers require quick responding controls.
Level of the water in the boiler must be kept above 50% of
height.
20. CONCLUSION
The various goals of boiler control includes:
1. To minimize excess air
2. To minimize blow down
3. To minimize steam pressure
4. To measure efficiency
