No of Pass 3-pass boiler Boiler Type Fire Tube Application Turbines Fuel Coal, Diesel Orientation Horizontal Material of Construction Metal A boiler is a closed vessel in which water or other fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including central heating, boiler-based power generation, cooking, and sanitation. Burner is a device which converts energy from fuel into heat energy which is transfeered to water through Boiler which results in Steam. Essential Features of Good Burners High combustion efficiency Part load performance Easy change over of fuels in case of dual fuel firing Ease of mounting Robust and compact design Noiseless operation Easy accessibility to all parts for inspection and maintenance Reliable components for continuous service Easy adjustment of air / fuel ratio. Suitability of components for specific fuel characteristics Low power consumption and preheating of air Provision for various safety interlocks Here, water partially fills a boiler barrel with a small volume left above to accommodate the steam (steam space). This is the type of boiler used in nearly all steam locomotives. The heat source is inside a furnace or firebox that has to be kept permanently surrounded by the water in order to maintain the temperature of the heating surface below the boiling point. The furnace can be situated at one end of a fire-tube which lengthens the path of the hot gases, thus augmenting the heating surface which can be further increased by making the gases reverse direction through a second parallel tube or a bundle of multiple tubes (two-pass or return flue boiler); alternatively the gases may be taken along the sides and then beneath the boiler through flues (3-pass boiler). In case of a locomotive-type boiler, a boiler barrel extends from the firebox and the hot gases pass through a bundle of fire tubes inside the barrel which greatly increases the heating surface compared to a single tube and further improves heat transfer. Fire-tube boilers usually have a comparatively low rate of steam production, but high steam storage capacity. Fire-tube boilers mostly burn solid fuels, but are readily adaptable to those of the liquid or gas variety.