Boiler feed water temperature low

Low feed water temperature may be caused be malfunctioning or incorrect operation of the deaerating feed tank. A common cause of low feed temperature is excessive recirculation of condensate.

1. A decrease in feed water temperature results in lower boiler efficiency because less steam is generated by the burning of a given amount of fuel as more energy required for evaporating more cold water. In order to meet the demand for steam, the firing rate must be increased. Also, superheater outlet temperature goes high with same firing rate as the steam flow through the superheater is reduced and the superheater outlet temperature rises whenever the steam flow through the superheater is reduced.
2. Low temperature in the deaerating feed tank leads to reduced release of oxygen from the feed water and therefore must be avoided. Oxygen in the feed water causes internal corrosion.