Working of boiler:

Water is filled in boiler shell through the feed valve up to 2/3^rd of shell. Water flows down through the down take header by means of descending water tubes and rises upwards through the uptake header and ascending tubes. Inclined tubes help in setting up the water circulation currents.   The hot flue gasses coming from the combustion chamber are made to pass over tubes, under side of drum and super heater tubes. The baffle plates ensure longer contact time of flue gasses with the tubes.  When water in tubes is heated, it begins to move upwards through the ascending tubes and cold water takes its place through the descending tubes. In this manner convection currents are set up.

The hottest gases being raised from the grate come in with that portion of water tube which is located on the highest side near the upper header. Water starts evaporating and mixture of water and steam thus formed reaches into boiler drum. Steam is collected in space above the water. This steam is lead to super heater then tubes for superheating. Superheated steam produced flows out through the stop valve.