Bales of dry pulp are normally used. The bales are slushed in heated tap water to a concentration of approximately 4%. Ready-made stock can also be transported in tank trucks from mills to the FEX system.
The stock preparation can be carried out in either the low consistency refining laboratory or the fractionation system. Stock can be prepared in a batch or a continuous process. If a batch process is used, the refined stock is mixed in storage tanks before being pumped into the paper machine. This procedure guarantees stable stock properties during a complete run. A continuous process prevents the stock from possible ageing phenomena.
After the addition of two large tanks, the stock storage system includes seven tanks, with a total capacity of 540 m³, allowing a maximum of 20 tonnes of stock. This makes it possible to perform a full day's trial with e.g. liner at high production rates, without the need to recirculate pulp. Stock in the storage tanks can be heated by the direct addition of steam.
Paper produced in the FEX paper machine, with the exception of paper samples for testing and analysis, ends up in the press broke chest where it is diluted and pumped to screw presses and finally collected in a container. A waste-paper company delivers all paper from FEX to a paper mill for recycling.