Crushing, press

1. Crushing results from extreme hydraulic pressure in the press nip, causing excessive water flow that disrupts the sheet structure.
2. Check felt tension and alignment.
3. Wash or replace dirty or filled felts.
— replace any worn felt.
— check felt design and wear.
See Felt cleaning.
4. Check seals on felt suction boxes and/or increase vacuum.
5. Check freeness and reduce refining or adjust fiber blend to raise freeness.
6. Reduce nip loading at press to avoid rewetting between presses.
— check showers and clear any plugged nozzles.
7. Consider change of felt design or running slower to permit more dwell time at presses.
8. Clean or change suction press roll; check seal on suction box for leaks.
— check for stock lumps on face of press which may cause crushing.
9. Check crown and curvature on press rolls and change if required.
— too hard a roll cover contributes to crushing.
— also, check vacuum in press roll.
10. Check and adjust presses for even loading front to back.
11. Check that stock temperature is not too low.
12. Check condition of felt showering and for excess showering; reduce pressure if needed.
13. Crushing may also result from poor control of refining, erratic basis weight, or variable ash retention.