Crush

1. Maintain uniform stock freeness.
— tendency to crush increases as freeness decreases.
— reduce refining or change furnish to increase freeness.
See Freeness varying.
2. Check couch roll for crown and wear.
— couch should be in good operating condition and evenly loaded across the machine.
— proper couch vacuum must be maintained.
3. New roll covers or reground rolls should be checked for hardness across the face.
— aging or chemical reactions can affect hardness.
4. Slack felts cause sagging and too tight a felt will close the weave and reduce the dewatering rate.
— truing line should be run straight with distortion no greater than 10% of felt width.
— it is common practice to move seam forward and backward to improve felt conditioning.
5. Furnish proportions should be run constant.
— excessive broke or heavy white water recirculation into the system can abet crushing.
— check and correct any variation in stock or water flow to machine.
6. Felts must be kept clean and maintained in good operating condition.
— wash or replace dirty or plugged felts.
Refer to Felt cleaning.
7. Ensure the elimination of entrained air in the stock.
8. Adjust consistency and/or consistency regulators.
9. Check all shower nozzles and vacuum boxes for plugging.
— increase vacuum.
10. Check for water running under slice.
— headbox and slice should deliver uniform distribution of stock across full width of machine.
— check for water dropping on sheet from other sources.