THE INFLUENCE OF FORMING FABRICS ON THE RETENTION AND DRAINAGE ON GAPFORMERS

This study is based on trials on FEX pilot paper machine ant STFI in S tockholm, Sweden. The FEX machine is a roll blade type gap former: The purpose of the study was to find out the influence of two different f orming fabric designs on drainage and retention on the former at incre asing speeds up to 2000 m/min. Observations of runnability of the fabr ics were mainly made as a tendency of carrying water. Changes in the t wo-sidedness of a sheet of paper show up in the fines distributions. A ll trials were run on newsprint grade. Basically. both sets of fabrics were able to handle the increased amount of water brought into the fo rmer with higher speeds. Retention decreased with increasing speed, bu t remained on a acceptable level. The set of double layer fabrics drai ned faster and at lower retention level than the set of triple layer f abrics. However, no significant differences can be reported. The chang es in fines distributions were small. As far as fabric runnability goe s, the importance of less water carrying and uniform drainage structur e became evident.