INDUSTRIAL BOILERS and its TYPES…..!!!
Requirements of Perfect Steam Boilers:
n Should
be absolutely reliable, capable of producing maximum steam at required pressure
for minimum of fuel consumption, with minimum attention and minimum initial cost
and operating cost.
n Simple
constructions
n Quick
starting from cold
n Strong
enough against temp. stress & strains
n Well
design combustion chamber
n Less
floor area, space & light weight
n Best gauges,
safety valves and other mountings
n Easily
accessible for inspection, cleaning and repairs
Classification of Steam Boilers
n Vertical
or Horizontal
n Stationary(Power
plant, industrial, central heating and combined power and heating
boilers.),Portable, Locomotive or Marine
n Internally
Fired or Externally Fired (Lancashire and Locomotive Boilers)
n Solid,
Liquid or Gas Fired
n Fire
(Smoke) Tube: Water is outside the tubes while the hot gases are inside the
tubes eg. Vertical, Cochran, Lancashire, Cornish, Locomotives, etc) or Water
Tube: Contain a large number of small tubes through which water circulates, the
fire and hot gases being outside of the tubes .e.g. Babcock and Wilcox, Sterling
and High pressure Boilers etc.)
Vertical Boilers
n Used
in small factories, small water supply plants, cranes, excavators, winch
engines in mines and on sites of temporary nature such as construction work
etc.
n Required
minimum floor space, not required elaborate foundations, and is portable.
n Cheap,
easy to start but inefficient due to large wastage of fuel and less heating surface.
n Vertical
Boilers are: Simple (having one to three cross tubes), fire tubes and water
tubes types.
Simple
Cross tube vertical boiler
n Consists
of a cylindrical shell surrounding a cylindrical fire box.
n Heating
surface is about 8-10 times the grate area.
n 50%
efficiency
Cochran Boiler
n It is
well design of a Vertical multi tubular fire tube boiler
n Improvement
over the simple vertical boiler as it provides greater heating surface.
n Total
heating surface area is about 10-25 times the grate area
n Efficiency
70-75%
n Ranges
from 1m dia.X2m high, evaporation 20kg/hr to 3m diameter X6m high, evaporation
3000kg/hr.
Lancashire Boiler
n Is
horizontal smoke tube boiler size range from a shell 2m diaX6m long to 3m
diaX10m long
n Working
pressure range are up to 20kgf/cm2
n Ratio
of heating surface to grate area is 24-30
n Efficiency
is about 56% without economizer and 75% with economizer.
n Similar
to Cornish boiler, in Lancashire Boiler two flue tubes but in Cornish boiler
only one flue tubes are there.
Babcock and Wilcox water tube Boiler
n Water
tube boiler having lager pressure ranges and larger sizes.
n Three
main parts, steam and water drum, water tubes and furnace.
High Pressure Boilers
n Two
types- Natural circulation & Forced circulation Boilers
Once-Through Forced Circulation Boiler
n Does
not required a steam and water drum, saving in weight
n Supercritical
Pressure Boiler
n Two
types- Benson and Ramzin
Fire tubes Vs water tubes Boilers
n Fire tubes boilers have
a large volume of water, therefore more flexible and can meet the sudden demand
of steam without much drop of pressure.
n Fire tubes boiler is
rigid and of simple mechanical construction, so greater reliability and low in
first cost.
n Fire tube boilers can
be made in smallest sizes therefore simple to fabricate and transport, occupies
less floor space but more height.
n Due to mostly
externally fired water tubes boiler so furnace can be altered considerably to
meet the fuel requirements.
n Water tubes boilers are
more readily accessible for cleaning, inspection and repairs, compared to the
fire tube boilers.
n Modern trend is in the
favors of water tube boiler due to continuous increase in capacities and steam
pressures.
pls also post some pics...
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