Study of fire and water Boilers

INTORDUCTION

Boilers may be defined as closed pressure vessels, which are used to generate steam at the pressure much higher than the atmospheric pressure by transfer of heat produced by burning of fuel to water.

The construction and appearance of steam generators depends on the arrangement made for burning the fuel and for transfer of heat to water. The steam produced by steam generator is used in following applications:

(1) For operating steam turbine of power plants for power generation.

(2) Locomotive Steam engines for traction.

(3) As process steam in industries.

(4) For heating applications.

(5) For running large steam propelled ships.

SPECIFICATIONS

•    The boilers are specified as per following parameters:
•        Steam Generation Rate: for example 50 000 kg /hr.
•       Max. Pressure: for example 150 kg/ sq.cm
•        Dimensions of steam drum
•        Horizontal / Vertical
•        Water / Fire Tube
•        Natural / Forced Circulation
•       Type of Fuel Used: Coal / Oil / Gas etc.

 ESSENTIALS OF A GOOD BOILER

•       Must be capable of producing the required Steam at the required pressure for minimum fuel required.
•            Should be capable of withstanding load variations.
•            Must not take a long time for starting
•            Easy maintenance and must be accessible.
•           Tubes must be strong enough
•           Must comply all safety regulations.

FACTORS AFFECTING BOILER SELECTION

•          Working Pressure and amount of steam required.
•          Floor area required.
•          Operating and Maintenance Required & Inspection facilities.
•          Fuel required.
•          Water requirements.

BOILER CLASSIFICATION

According to Tube Contents:

Boilers may be water tube or fire tube type. In water tube boilers the water flows in the tubes and in Fire Tube Boilers hot flue gasses circulate through the tube. Babcox & Wilcox Boiler is water tube boiler where as Locomotive and Lancashire Boiler are examples of Fire tube Boiler.

According to the Axis of Boiler:

The Boiler may be Horizontal axis or Vertical Axis type. Babcox & Wilcox, Locomotive and Lancashire Boilers are all examples of Horizontal axis boilers.

According to Number of Boiler tubes:

May be single or multiple tubes boilers, Cornish Boiler is a single tube boiler whereas other boilers are multi-tube boilers.

 According to Position of Furnace:

Externally / internally fired boilers, in externally fired boiler the furnace are external to the boiler shell.

On the Basis of Mobility:

Stationary / Moving Boilers

On the Basis of Water Circulation:

Natural / Forced Circulation

On the Basis of Draught:

Forced / induced draught.

On the Basis of utility of steam:

Example: Power Plant, Marine and Locomotive boilers etc.