Feed Tank Design
A well designed feed tank should be designed to minimise the oxygen within the feed system. This is especially important with open feed systems.
The following are taken as parameters for a well designed tank
- Adequate ventilation with on or more vent pies determined by the volume of water
- Condensate enters as low as possible via a slotted sparge pipe
- Cold water make up enters at highest point
- Sufficient tank volume to cope with transient flows from normal operations without necessitating spilling back to feed tanks or overflows.
- Tank to have sufficient volume of water at normal working level to allow for 1 hours operation at maximum demand.
- Take off to feed pumps to be at least 75mm from tank bottom
- Tank to be located to provide head requirements at normal working level for feed pumps
As a rule of thumb chemical reaction rates double for evey 10'C rise in temperature. For feed system this remains true upto about 80'C for open system. After this due to reducing solubility of oxygen the rate of corrosion reduces. Thus steam heating on the open feed tanks have thermostats set at 85'C or higher