Pickup problems

1. On Yankee tissue machines, the felt needs a uniform water film to provide the necessary surface tension to pick up and hold the sheet.
— new felts must go through a break-in period before they reach optimum running conditions.
— during the break-in period, pickup problems are more prevalent.
2. Felts must initially be open enough so that pickup roll vacuum can effectively lift sheet from the wire, but closed and smooth enough to provide adhesive force to hold the sheet.
3. It is essential that the pickup felt be kept clean and open enough to perform its design function.
— too coarse a press fabric surface or a felt that is too open can cause problems.
4. Check to ensure the proper speed relationship between the pickup felt and the forming fabric.
— too great a speed differential will result in pickup problems.
5. For free wire pick-up, check to ensure the pick-up roll, bar or shoe provides the proper penetration into the wire run.
6. For pick-up bar or shoe, check that the felt/wire separation is about 3.5 to 5.0
7. Poor formation on the forming table produces sheet that are difficult to pick up.
— eliminate non-uniform basis weight and streaks.
8. Watch drainage rate and degree of fiber stapling in forming fabric; both influence the release of the sheet to the pickup felt.