The feed system completes the cycle between boiler and turbine toenable the exhausted steam to return to the boiler as feedwater. Thefeed system is made up of four basic items: the boiler, the turbine, thecondenser and the feed pump. The boiler produces steam which issupplied to the turbine and finally exhausted as low-energy steam to thecondenser. The condenser condenses the steam to water (condensate)which is then pumped into the boiler by the feed pump.
Other items are incorporated into all practical feed systems, such as adrain tank to collect the condensate from the condenser and provide asuction head for the feed pump. A make-up feed tank will provideadditional feedwater to supplement losses or store surplus feed from thedrain tank. In a system associated with an auxiliary boiler, as on a motorship, the drain tank or hotwell will be open to the atmosphere. Such afeed system is therefore referred to as 'open feed'. In high-pressurewatertube boiler installations no part of the feed system is open to the atmosphere and it is known as 'closed feed'.