Babcok Wilcox Boiler
This is one of the most important type of a water tube boiler generally employed in the power houses for power generation as shown in Figure.
- It consists of number of inclined water tubes (WT) connected between the uptake header (UH) and the downtake heater (DH). Headers are provided with hand holes in the front tubes and are covered with caps (C).
- Whole combustion chamber is divided into number of parts with the help of baffles (B) so that the hot gases first move from the furnace (F) upwards between the water tubes and then move downward and upwards between the baffles over the tubes and finally these are exhausted to the chimney through the damper (DP).
- The dampers regulate the amount of flue gases and thus the supply of air to the grate. Doors (D) are provided for a man to enter in the boiler for cleaning and repairing purposes.
- The feed water enters the front of the drum (DR) and travels to the back part of the drum and then descends through the vertical tube to the downtake header.
- From here the water enters into the water tubes to the uptake header and then again to the drum.
- The water tubes are near the uptake header are in contact with the hotter flue gases compared to the portion near the downtake header due to which the water in the uptake header rises due to decreased density and enters the drum which is replaced by the colder water from the downtake header. Water continues to circulate like this till it is evaporated.
- This type of circulation of water occurring due to density difference is called free circulation. The superheating of steam is done in the superheater (SH).
- It consists of large number of steel tubes. Wet steam from the boiler drum enters in the other tube (OT), then passes into the superheated tubes and during its passage it gets further heated up.
- Superheated steam now enters into the inner tubes (IT) and from here it is withdrawn through a stop valve (SV).
- The boiler also has its usual mountings like pressure gauge (PG), safety valve (SFV). water level indicators (WLI), feed valve (FV) etc.