boiler

A boiler is a closed vessel in which water or another working fluid is heated to produce steam or hot water. Boilers supply heat for space heating, industrial processes, and electricity generation. They are designed for saturated or superheated steam, depending on operating pressure and temperature.

A typical boiler includes a pressure vessel, a heat source (burner or electric element), a feedwater system, and a means to remove the steam or heated water. Heat is transferred from combustion gases or electrical heating to the fluid inside, while controls monitor pressure, temperature, and water level to maintain safe operation.

Boilers are commonly classified as fire-tube or water-tube. Fire-tube boilers heat water surrounding tubes through which hot gases pass. Water-tube boilers run water inside tubes heated by surrounding flames and are suited to high pressures and large outputs. Additional types include hot-water (hydronic) boilers and electric boilers.

Safety and maintenance are essential. Boilers must meet pressure-vessel codes, such as the ASME Boiler and Pressure Vessel Code, and include safety devices like relief valves, low-water cutoffs, and flame safeguards. Regular water treatment, inspections, and blowdown procedures help prevent corrosion, fouling, and catastrophic failure.

Efficiency improvements include condensing designs that recover latent heat, modulating burners, and advanced controls. In many settings, boilers are integrated with other energy systems to optimize fuel use and emissions.