Sheet sealing

1. High headbox consistencies will lead to:
— slower drainage.
— higher vacuums in suction boxes.
— wetter sheet off couch.
— increases in machine drive loads.
— more rapid fabric wear.
2. Poor sheet release will lead to:
— greater fiber penetration in wire/fabric.
— more force needed to remove web from forming fabric.
— increased wet draws.
— more frequent breaks.
— wire marking aggravated by sheet sealing.
3. To eliminate sheet sealing:
— breast roll discharge should be kept to an absolute minimum.
— stock jet should be directed to strike at leading edge of forming board.
— forming boards should have no foil angle.
— initial foils should be well spaced with low foil angles to control rate of drainage.
4. Check for correct fabric design.
— finer mesh with sheet side support reduces fiber penetration and tendency for sheet sealing.
5. Excessive water removal within first two meters after slice will increase fiber penetration.
6. If sealing is occurring at the forming board, it is probably due to pressure forming.
— ensure that head is slightly below wire speed in a drag mode.
7. If sealing is occurring at the vacuum foils, it is probably due to excess vacuum that seals sheet on bottom side.