The basic design of the white-water system of the FEX paper machine is demonstrated below. The system is closed material wise, by recovering material from the excess white water using a disc filter, and mixing it into the thick stock. This is still today unique for a pilot paper machine. All volumes involved are minimized, to reduce the time to equilibrium, which after start-up of a water filled system is within the range 60-90 minutes.

The cleaned excess white water flow is utilized to dilute the web in the press broke chest.  This broke is not recirculated, instead fresh furnish is fed during the entire trial period.

The two short circulations (designed for maximum flow rates of 5000 and 10000 l/min respectively) each includes wire pit, thick stock addition, mix pump, trash separator and deaerator. The flow from the two deaerators can be distributed to three headbox pumps.

Extensive measurements of white water flow rates at different positions combined with off-line analysis of concentration of different material components make it possible to evaluate material flow balances in some detail.

Schematic of the white-water system of the FEX paper machine (click on the image for a high resolution version).