A steam drum is a standard feature of the boiler water pipes. It is a reservoir of water/steam at the upper end of the tube of water. Drums keep the steam produced in the water tubes and act as a phase separator for mixed steam/water. The density difference between hot and cold water helps in the accumulation of -water/and “hot” saturated steam into the steam drum.

Made of High Carbon Steel with a high tensile strength and work that involves a temperature of about 390oC and pressures well above 350 psi (2.4MPa). Separated vapor is pulled out from the top of the drum and distributed to the process. Further heating of the saturated vapor will make superheated steam is typically used to drive steam turbines. Saturated vapor is pulled from above the drum and re-enters the furnace through a superheater. The mixture of steam and water entering the steam drum through riser tubes, internal drum consisting of demister separates water droplets from steam to produce dry steam. Saturated water vapor at the bottom of the drum flows down through the downcomer pipe, usually heated, for the header and water drums. Accessories include a safety valve, water-level indicators, and level controllers. The feed water is also fed to the boiler drum through the steam feed pipe extending inside the drum, along with the steam drum.

A steam drum is used alone or in company mud-drum/feed water drum located on the lower level. A boiler with the steam drum and mud/water drum called a bi-drum boiler and steam drum boilers with an only so-called mono-drum boiler. Construction of bi-drum boiler normally intended for low-pressure boiler-rating while the mono-drum largely designed for high-pressure ratings.