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26 Aug 2014

Cornish Boiler



Cornish boiler is a simple horizontal boiler which belong to the shell and tube class of boilers. Cornish boiler is much like the Lancashire boiler. Cornish boiler has the ability to produce steam at the rate of 1350 kg/hr and can take the maximum pressure of about 12 bar. Dimensions of the Cornish boiler shell is 4 m to 7 m in length and 1.2 m to 1.8 m in diameter. Cornish boiler is a fire tube type of boiler that is hot gases flow in tubes and water surround these tubes in shell.



Parts of Cornish boiler


Tubes
These are present inside the shell and hot gases flow through them.

Shell
A big shell which contain water inside it as well as tubes. Heat transfer between hot gases and water is take place here

Side flue
Flue are the tubes which take hot gases after they passes out from the fire tubes. Flue present at side of the horizontal shell are called side flues.

Bottom flue
Flue present at the bottom of the shell is called bottom flue. Bottom flue take the smoke toward the chimney.

Grate
Grate is the place where fuel is added for burning.

Ash pit
Ash pit the one which contain the ashes of fuel aster they are completely burn.

Chimney
Chimney take smoke from the bottom flue and take it out to the atmosphere.

Stop valve
It is used to regulate the flow of steam from boiler

Safety valve
Purpose of this valve is to stop the steam pressure from exceeding the maximum limit

Blow of cock
Blow of cock is used to clean boiler by discharging the water and sediments from bottom of boiler


Working of the Cornish boiler

Fuel is added in the grate area where it burn to produce hot gases. There hot gases move into the fire tube which take it inside the shell where it exchange its heat with surrounding water. Water take heat and after some time it start boiling to produce steam. Hot gases upon reaching at the end of the fire tube, divided into two section and each move into the one of two side flue which take them once again at the front section of the boiler where they are move into the bottom flue and bottom flue take them toward the chimney. Chimney throw these gases out of the boiler into the atmosphere. In this process hot gases travels complete length of boiler thrice that is once in fire tube then in side flue and at last bottom flue.  Maximum heat transfer is taken place at fire tube and shell section then taken place at side flue and at last at bottom flue.


Application of Cornish boiler

  • Cornish boiler are used in many industries like textile, sugar, paper, tyre, chemical etc
  • They are also used to produce steam to run steam turbine
  • They are also used in many marines

Advantages of Cornish boiler

  • Cornish boiler have simple design and easy construction
  • One of its main advantages is its Compactness and Portability
  • Low construction and maintenance cost
  • It has ability to overcome load fluctuation

 Disadvantages of Cornish boiler

  • Low steam production rate = 1350 kg/hr
  • Low maximum steam pressure range 12 bar
  • Need more ground because of horizontal structure

23 Aug 2014

LANCASHIRE BOILER


LANCASHIRE BOILER is a simple horizontal boiler and belong from the shell and tube types of boilers. It has a circular shell connected to end plates supported by gusset plates.  It has a circular shell connected to end plates supported by gusset plates. Lancashire boiler have two fire tubes whose length is equal to length of the boiler and diameter of the fire tube is less than half of the diameter of the shell. 






Parts of LANCASHIRE BOILER


Grate


Grate contain the fuel for combustion

Feed valve


Feed valve is used to enter fuel material inside the grate

Fire hole


Fire hole is used to introduce the initiating fire spark 

Safety valve


Safety valve is used to release the pressure when it crosses the safety limits of the boiler

Bottom flue


Flue present at the bottom of the shell and take the hot gases from the front to back of the boiler

Side flue


Flue present at both sides of the shell and take hot gases from the back to the main outlet of the boiler

Low water alarm


Alarm which inform us when water level is low than safety line


Dampers


Flow of gases from side flues to the chimney is controlled by the sliding doors located at the end of side flue

Blow-off clock


For the removal of mud and sediments and blow off clock is provided at the bottom of front section of boiler.

Fusible plug


Fusible plug is used to prevent the coil tubes of the boiler are overheating, extinguishing the fire when water level is lower than a particular level and



Working of LANCASHIRE BOILER


In Lancashire boiler fuel is added into the grate of the boiler and burning of this make gases hot. These hot gases start their motion from grate section and enter the fire tube of the boiler. Hot gases enter at the front section of the boiler and leave the boiler from the back and enter the bottom fuel and start moving toward the front section of the boiler. At front section hot gases leave the bottom flue and enter in side flue and move again toward the back of the boiler and enter the main outlet there. There is 85% heat transfer when hot gases are in fire tube and 15% when they are in bottom and side flue. Pressure range of the boiler is about 0.7 MPa to 2 MPa and efficiency is 65 to 70%. Dimension of the boiler depends on the dimension of the shell which is 2 to 3 m is diameter and 6 to 10 m in length.



Application of Lancashire Boiler


Lancashire Boilers are used to drive


  • Steam turbines 
  • Marines  
  • Locomotives

Lancashire Boilers are used in industries as processing agent 

  • textile industry 
  • paper industry 
  • sugar industry 
  • tire industry 
  • chemical industry 
  • breweries industry
 

    Advantages of Lancashire Boiler


    • Lancashire Boiler is an Economical boiler 
    • It can be easily operated 
    • Compactness 
    • Portability 
    • Simple design  
    • Easy construction 
    • Have low maintenance cost 
    • High overall efficiency (80% to 85%) 
    • Steam produce have excellent quality 
    • Due to the large quantity of water available, it can easily overcome the load fluctuation



    Disadvantages Lancashire Boiler


    • Corrosion in water legs 
    • It is difficult to clean inside 
    • Low steam production rate (9000kg/hr) 
    • Horizontal structure cover more ground space 
    • Maintenance of brick work is tedious. 
    • Have limited grate area because the fire tubes have small diameter. 
    • It’s a low pressure Boiler maximum limit is only 20 bars

     Working and construction video