In Lancashire boilers, the feed water tube is Perforated.

Lancashire Boiler

The locomotive boiler is a horizontal drum axis, multi-tubular, natural circulation, Jartificial draft, forced circulation, mobile, medium pressure, and internally fired boiler. It has a high steam generation rate. In locomotive boiler, maximum steam pressure 1.8 M N/m².

• The Lancashire boiler consists of a cylindrical shell inside which two large tubes are placed.
• The flue gases flow through the fire tube, situated inside the boiler shell, so it is a fire tube boiler. This boiler generates low-pressure steam.
• It is an internally fired boiler because the furnace is placed inside the boiler.
• It is a horizontal drum axis, natural circulation draft, medium pressure, fire tube boiler with a perforated feed water tube.
• It is basically a shell and tube type heat exchanger in which the flue gases flow through the tubes and the water flows through the shell. The heat is the transfer from flue gases to the water through convection. It is a natural circulation boiler that uses natural current to flow the water inside the boiler.
• Three spaces create between the drum and the bricks, one is at the bottom and two are insides. Flue gases pass through the fire tubes and side and bottom space.
• The fuel is charged at the grate which produces flue gases. These flue gases first pass through the fire tube from one end to another. These fire tubes transfer 80 – 90 % of total heat to the water. The backward flue gases pass from the bottom passage where they transfer 8 – 10 % heat to water. The remaining flue gases pass from the side passage where it transfers 6 – 8 % of the heat to water. The brick is the lower conductor of heat, so works as a heat insulator.