Industrial Boilers

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Industrial Boilers

• Steam generators
• Closed vessels
• made of steel and
• used for generation of steam
• vaporizing water
• combustion of fuels
• eg. coal,coke,oil,wood,saw dust and begesse etc.
• Steam used for producing power,for industrial
  process work or for heating proposes.

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Requirements of a Perfect Steam Boilers

• 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.
• Simple constructions
• Quick starting from cold
• Strong enough against temp. stress strains
• Well design combustion chamber
• Less floor area, space light weight
• Best gauges,safety valves and other mountings
• Easily accessible for inspection,cleaning and
  repairs

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Classification of Steam Boilers

• Vertical or Horizontal
• Stationary(Power plant,industrial,central heating
  and combined power and heating boilers.),Portable,
  Locomotive or Marine
• Internally Fired or Externally Fired (Lancashire
  and Locomotive Boilers)
• Solid,Liquid or Gas Fired
• Fire(Smoke)TubeWater 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.eg.Babcock and Wilcox, Stirling and High
  pressure Boilers etc.)

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Vertical Boilers

• 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.
• Required minimum floor space,not required
  elaborate foundations,and is portable.
• Cheap,easy to start but inefficient due to large
  wastage of fuel and less heating surface.
• Vertical Boilers areSimple(having one to three
  cross tubes), fire tubes and water tubes types.

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Simple Cross tube vertical boiler

• consists of a cylindrical shell surrounding a
  cylindrical fire box.
• heating surface is about 8-10 times the grate
  area.
• 50 efficiency

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Cochran Boiler

• It is well design of a Vertical multitubular fire
  tube boiler
• Improvement over the simple vertical boiler as it
  provides greater heating surface.
• Total heating surface area is about 10-25 times
  the grate area
• Efficiency 70-75
• Ranges from 1m dia.X2m high,evaporation 20kg/hr
  to 3m dia X6m high,evaporation 3000kg/hr.

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Cochran Boiler contd.
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Lancashire Boiler

• Is horizontal smoke tube boiler size range from a
  shell 2m diaX6m long to 3m diaX10m long
• Working pressure range are up to 20kgf/cm2
• Ratio of heating surface to grate area is 24-30
• Efficiency is about 56 without economizer and
  75 with economizer.
• Similar to Cornish boiler,in Lancashire Boiler
  two flue tubes but in Cornish boiler only one
  flue tubes are there.

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Lancashire Boiler contd
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Lancashire Boiler contd
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Locomotive Boiler

• Is an internally fired multitubular fire tube
  boiler

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Babcock and Wilcox water tube Boiler

• Water tube boiler having lager pressure ranges
  and larger sizes.
• Three main parts, steam and water drum,water
  tubes and furnace.

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Stirling Boiler

• Example of water tube boiler where bent tube are
  used instead of straight tube which are used in
  Babcock and Wilcox boiler

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High Pressure Boilers

• Two types- Natural circulation Forced
  circulation Boilers

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High Pressure Boilers contd

• La-Mont Boiler( Forced circulation Boiler)

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Once-Through Forced Circulation Boiler

• Does not required a steam and water drum,saving
  in weight
• Supercritical Pressure Boiler
• Two types- Benson and Ramzin

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Ramzin Boiler
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Loeffler Boiler

• Indirect heating is combined with forced
  circulation

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Velox boiler

• Fire tube forced circulation Boiler

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Fire tubes Vs water tubes Boilers

• Fire tubes boilers has a large volume of
  water,therefore more flexible and can meet the
  sudden demand of steam without much drop of
  pressure.
• Fire tubes boiler is rigid and of simple
  mechanical construction,so greater reliability
  and low in first cost.
• Fire tube boilers can be made in smallest sizes
  therefore simple to fabricate and transport,
  occupies less floor space but more height.
• Due to mostly externally fired water tubes boiler
  so furnace can be altered considerably to meet
  the fuel requirements.
• Water tubes boilers are more readily accessible
  for cleaning,inspection and repairs,compared to
  the fire tube boilers.
• Modern trend is in the favors of water tube
  boiler due to continuous increase in capacities
  and steam pressures.

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Boiler Mountings and Accessories

• Fitting and devices which are necessary for the
  safety and control are knows as boiler mountings
• Fitting or devices which are provided to increase
  the efficiency of the boiler and help in the
  smooth working of the plant are knows as boiler
  accessories.
• Fittings which are essential from the safety
  point of view are as follows,
• Water level indicators
• Safety valves
• Combined high steam and low water safety valve
• Fusible plug

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Boiler Mountings and Accessories contd.

• Fittings which are essential from the control
  point of view are as follows,
• Pressure gauge
• Junction or stop valve
• Feed check valve
• Blow-off cock
• Man hole and Mud Box
• The important accessories are
• Superheater
• Economiser
• Air-preheater
• Feed pump or injector