Boiler Water Steam Line

Many times we confused about boiler flow path especially at the parts of wall and roof. Picture beside completely can be described flow path from economizer to super heater and re-heater.

Feedwater on its way to the boiler circulation loop enters the economizer through the feedwater stop and check valves, and passes through the economizer tubes, the economizer stringer support tubes, and on to the outlet headers.

From the economizer outlet header, feedwater is piped into both ends of the steam drum and is distributed along the drum length by means of a perforated feedpipe. Here the feedwater mixes with the hot water in the drum.


This water mixture, called boiler water, then flows down the downcomers located outside the boiler. Water from the downcomer is distributed to the furnace wall tubes via the inlet supply tubes and headers.

Then, the boiler water flows up the furnace tubes to the steam drum. Heat applied to the furnace tubes causes boiling of the fluid in the tubes. The water/steam mixture rises through the boiler tubes due to natural circulation. This occurs when a hot, less dense, fluid flows up and the cold, denser, fluid flows down. Natural circulation will be discussed in more detail later.

In the steam drum, the steam is separated from the steam/water mixture by way of cyclone separators and scrubbers. The dry steam passes through multiple connections to the headers supplying the furnace roof tubes and convection pass wall tubes and then to the primary superheater inlet header.

The steam flows through the primary superheater and discharges through its outlet header and through connecting piping equipped with two spray attemperators. The steam then enters the wide spaced platen superheater located at the top of the furnace.


A second stage of superheater attemperation is provided between the platen superheater and the secondary superheater. The steam then enters the secondary superheater inlet headers and flows through the secondary superheater sections to the outlet header nozzle that connects to the main steam line.

Steam returning from the High Pressure turbine passes through the reheat attemperator located in the inlet piping to the reheater. It then flows through one end of the reheater inlet header through the horizontal and pendant reheater sections to the outlet header. Hot reheat steam then passes from one end of the outlet header to the turbine



Details flow path can check at picture above.