Types Of Boilers

Following are the different types of Boilers:

Simple Vertical boiler :

Simple vertical boiler is one whose axis of orientation is vertical with respect to the ground. It is a fire tube or a water tube boiler.A simple vertical boiler produces steam at a low pressure and in a small quantity. It is, therefore, used for low power generation or at places where space is limited. This boiler has a cylindrical shell surrounding a nearly cylindrical fire box. The fire box is slightly tapered towards the top to allow the ready passage of the steam to the surface. The fire box is fitted with two or more inclined cross tubes, to increase the heating surface as well as to improve the circulation of water.

Parts of simple vertical boiler:

1. Fire hole
2. Fire box
3. Cross box
4. Hand hole
5. Fire box
6. Fusible plug
7. Water gauge
8. Cylindrical shell
9. Steam space
10. Manhole
11. Pressure gauge
12. Steam stop valve
13. Safety valve
14. Uptake
15. Chimney
16. Ash pit
17. Grate
18. Feed check valve

Cochran Boiler or Vertical Multitubular Boiler :

It is a multi-tubular vertical fire tube boiler having a number of horizontal fire tubes. It is an improved type of simple vertical boiler where the heating surface has been increased by means of a number of fire tubes.There are various designs of vertical multi tubular boiler. A Cochran boiler is considered to be one of the most efficient type of such boilers. This boiler consists of an external cylindrical shell and a fire box. The shell and fire box are both hemispherical. The hemispherical crown of the boiler shell gives maximum space and strength to withstand the pressure of steam inside the boiler. The hemispherical crown of the fire box is also advantageous for resisting intense heat. The fire box and the combustion chamber is connected through a short pipe. The fuel gases from the combustion chamber flow to the smoke box through a number of smoke tubes. These tubes generally have 62.5mm external diameter and are 165 in number. The gases from the smoke box pass to the atmosphere through a chimney. The combustion chamber is lined with firebricks on the shell side. A manhole the top of the crown on the shell is provided for cleaning.

Parts of Cochran Boiler:

2. Crate
3. Fire box
4. Flue pipe
5. Fire tubes
6. Combustion chamber
7. Chimney
8. Man-hole

Scotch Marine Boiler :

The marine steam boilers of the scotch or tank type are used for marine work, particularly, due to their compactness, efficiency in operation and their ability to use any type of water. It does not require brick work setting and external flues. It has a drum of diameter from 2.5 to 3.5 meter place horizontally. These steam boilers may be single ended or double ended. The length of a single ends steam boiler may be upon 3.5 meter while for double ended upon 6.5 meters. A single ended boiler has one to four furnaces which enter from front end of boiler. A double ended boiler has furnaces on both ends, and may have furnaces from two to four in each end.

It is of two types:

1. Single Ended
2. Double Ended

Single Ended Scotch Marine Boiler:

The length of the single ended steam boiler may be upto 3.5 m
The single ended steam boiler contains one to four furnaces and these furnaces enter from the front end of the boiler.

Double Ended Scotch Marine Boiler:

The length of double ended steam boiler is upto 6.5 m.
In double ended scotch marine boiler, the furnaces are present on both of its ends. And the number of furnaces varies from 2 to 4 in each end.

Parts of Scotch Marine Boiler:

1. Furnace
2. Combustion chamber
3. Smoke box
4. Chimney
5. Boiler shell

Lancashire Boiler :

It is a stationary fire tube type, internally fired, horizontal and natural circulation boiler. It is used where working pressure and power required are moderate. These boilers have a cylindrical shell of 1.75m to 2.75m diameter. Its length varies from 7.25m to 9m. It has two internal flue tubes having diameter about 0.4 times that of shell. This type of boiler is set in brick work forming external flue so that part of the heating surface is on the external shell.

Parts of Lancashire Boiler:

1. Cylindrical shell
2. Furnace tubes, bottom flue and side flues
3. Grate
4. Fire bridge

Cornish Boiler :

It is similar to Lancashire boiler in all respects, except there is only one flue tube in Cornish boiler instead of two Lancashire boiler, The Cornish boiler is generally 1m to 2m and its length varies from 5m to 7m. The diameter of flue tube may be about 0.6 times that of shell. The capacity and working pressure of Cornish boiler is low as compared to Lancashire boiler.

Parts of Cornish boiler:

1. Tubes
2. Shell
3. Side flue
4. Bottom flue
5. Grate
6. Stop valve
7. Chimney
8. Ash pit
9. Blow of cock
10. Stop valve
11. Safety valve

Locomotive Boiler :

It is multi-tubular horizontal, internally fired mobile boiler. Locomotives boiler are divided into three main parts :

1.smoke box, box and box.

The principle feature of this boiler is to produce steam at a very high rate. It consists of a shell or barrel having 1.5 meter diameter and 4 meters in length. The coal is fed into the fires box through the fire door and burns on grate. The flue gases from the grate are deflected by brick arch, and thus whole of the fire box is properly heated. There are about 157 thin tubes or fire tubes(47.5 mm diameter) and 24 thick or super heated tubes(130 mm diameter). The flue gases after passing through these tubes enter a smoke box. The gases are then lead to atmosphere through a chimney. The barrel contains water around the tubes, which is heated up by the flue gases and gets converted into steam.

Parts of Locomotive Boiler:

1. Grate
2. Damper
3. Ash pit
4. Fire box
5. Fire hole
6. Fire brick arch
7. Fusible plug
8. Operating rod
9. Steam whistle
10. Safety valve
11. Regulator
13.Super heating tube
14. Steam pipe
15. Steam header
16. Smoke box
17. Blast pipe
18. Super heated steam out let
19. Chimney
20. Door

Babcock and Wilcox Boiler :

It is a water tube boiler used in steam power plants. In this, water is circulated inside the tubes and hot gases flow over the tubes. It is a straight tube, stationary type water tube boiler. In this boiler, the water tubes are inclined to the horizontal and connects the uptakes to the down takes header. Each row of the tubes is connected with two headers and there are plenty of such rows.

Parts of Babcock and Wilcox Boiler:

1. Steam and water drum (boiler shell)
2. Water tubes
3. Uptake-header and down corner
4.  Grate
5. Furnace
6. Baffles
7. Super heater
8. Mud box
9. Inspection door

La-Mont Boiler :

A forced circulation boiler was first introduced by La-Mont in the year 1925 which is used in Europe and America. This is a Modern High Pressure Boiler (water tube type steam boilers) working on forced circulation system.This is a modern high pressure water tube type steam boiler working on a forced circulation. The circulation is maintained by a centrifugal pump, driven by a steam turbine, using steam from the boiler. The forced circulation causes the feed water to circulate through the water walls and drums equal to ten times the mass of steam evaporated. This prevents the tube from being overheated.

Parts Of La-Mont Boiler:

1. Steam separator drum
2. Circulating pump
3. Distributing header
4. Evaporator
5. Convection superheater
6. Steam outlet
7. Economizer
8. Air preheater
9. Capacity

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