The boiler is filled with water to the specified level using a feed pump.The feed check valve permits the feed water to entire into the boiler ,but does not allow water to flow back.Coal is fed into the grate through the fire hole and burnt.Ash formed is collected in the provided below the grate and is removed.The hot gases from the firebox pass through the flue pipe to the combustion chamber.From the combustion chamber the hot gases pass through the horizontal flue tubes to smoke box.The gases from the smoke box are discharged to the atmosphere through the chimney.Smoke box is provided with a door for cleaning the flue tubes and smoke box.The hot gases while passing through the flue tubes transfer heat to the water which is already heated by the fire box.The water gets converted into steam and accumulates in the steam space at the top of the shell.This steam is taken to the steam supply pipe through the steam stop valve.
Cochran boiler
It is one of the best types of vertical multi-tubular boiler, and has a number of horizontal fire tubes it also a Low Pressure Boiler.
Construction: Cochran boiler consists of a cylindrical shell with a dome shaped top where the space is provided for steam. The furnace is one piece construction and is seamless. Its crown has a hemispherical shape and thus provides maximum volume of space.
Working: The fuel is burnt on the grate and ash is collected and disposed of from ash pit. The gases of combustion produced by burning of fuel enter the combustion chamber