20-10-2012, 06:05 PM
Industrial Boilers
ppt boilers 1.pptx (Size: 1.04 MB / Downloads: 59)
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
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)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.eg.Babcock and Wilcox, Stirling and High pressure Boilers etc.)
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 are:Simple(having one to three cross tubes), fire tubes and water tubes types.
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.
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.