Boilers are used to produce either steam or hot water for production purposes. Providing hot water to processing vessels such as jacketed tanks and kettles and steam to heat tunnels are just two examples. Steam boilers use the pressure created by the heating process to move heat throughout the system while hot water boilers use pumps to achieve the same result. The condensed steam or cooled water is returned through a series of pipes back to the boilers so that the heating process can be repeated again.