Holes in the sheet

1. Determine if there is a pattern to the holes.
— e.g., a frequency consistent with a single revolution of a roll or item of machine clothing.
2. Check for plugged headbox shower nozzles.
— check L/b ratio.
3. Ensure there is no mechanical damage or corrosion m headbox.
4. Plugged water lines to rectifier roll bearings permit side-of-box build-ups, which will break loose.
5. Check for scratches on surface of headbox sidewalls and floor below liquid level where fiber and fines can build up.
6. Check for fines accumulation in wet end approach system.
7. Holes may result from moving wet line.
8. Check clarified white water used on wire return roll showers.
9. Check for build-up under forming table and headbox apron.
10. Check that low vacuum in suction box area of press nip may not remove enough water.
11. Review nature, age, and hardness of roll covers.
12. Check for presence of stickies, free size, grease, or pitch deposits on wires and felts.
13. Check all shower positions for proper application and blocked nozzles.
14. Check for speed differences between pickup felt and wire.
15. Determine if sheet is “spitting over”.
16. Check for coating build-up on dryer surfaces.
— check dryer doctors and oscillation.
17. Make certain there is no water dripping on surface of sheet.
18. Check for slime spots.
19. Check for poor wire/felt transfer (pick-up).