Classifications of Steam Boilers

Classifications of Steam Boilers:

Though there are many classifications of steam boiler, yet the following are the important from the subject point of view:

    ➦ According to the contents in the tube
        (i) Fire tube Boiler: A boiler in which the hot combustion gases pass through the boiler tubes, which are surrounded by water. e.g. Lancashire boiler, Cochran boiler, Locomotive boiler etc.

        (ii) Water tube Boiler: A boiler in which the water flows a number of small tubes which are surrounded by hot combustion gases. e.g. Babcock and Wilcox boiler, Stirling boiler, Bension boilers etc.
Steam Boiler

    ➦ According to the position of the furnace
        (i) Internally fired boiler: In internally fired steam boilers, the furnace is located inside the boiler shell. Most of the fire tube boilers are internally fired.
        (ii) Externally fired boiler: In externally fired steam boilers, the furnace is arranged underneath in a brick work setting. Water tube steam boilers are always externally fired.
    ➦ According to the axis of the shell
        (i) Vertical boilers: In vertical steam boilers, the axis of the shell is vertical. Simple vertical boiler and Cochran boiler are vertical boilers.
        (ii) Horizontal boilers: In horizontal steam boilers, the axis of the shell is horizontal. Lancashire boiler, Locomotive boiler and Babcock and Wilcox boiler are horizontal boilers.

    ➦ According to the number of tubes
        (i) Single tube boilers: In single tube steam boilers, there is only one fire tube or water tube. Simple vertical boiler and Cornish boiler are single tube boilers.

        (ii) Multitubular boilers: In multitubular steam boilers, there are two or more fire tubes or water tubes. Lancashire boiler, Locomotive boiler, Cochran boiler, Babcock and Wilcox boiler are multitubular boilers.

    ➦ According to the method of circulation of water and steam
        (i) Natural circulation boilers: the circulation of water is by natural convection currents, which are setup during the heating of water. In most of the steam boilers, there is a natural circulation of water.
        (ii) Forced circulation: there is a forced circulation of water by a centrifugal pump driven by some external power. Use of forced circulation is made in high pressure boilers such as La-Mont boiler, Bension boiler, Loeffler boiler and Velcon boiler.

    ➦ According to the use
        (i) Stationary boilers: The stationary boilers are used in power plants and in industrial process work.
        (ii) Mobile boilers: The mobile boilers are those which move from one place to another place. These boilers are Locomotive boilers.

    ➦ According to the source of heat
        (i) Solid fuel
        (ii) Liquid fuel
        (iii) Gaseous fuel
        (iv) Electrical energy
        (v) Nuclear energy


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