Crushing

At the couch:
1. Sheet running wet too close to the couch.
— reduce amount of water in sheet or lower slice.
— increase flat box vacuum.
— put on any flat boxes that may be shut off.
2. Lump breaker roll should be centered on couch suction box.
— if adjustment is necessary, correct at first opportunity.
3. Reduce volume of water going to shower on lump breaker roll.
4. If suction box is skipping or missing, correct or shut off box.
5. Free up sheet to improve drainage on forming fabric.
6. Increase headbox temperature.
See Couch vacuum varying.
At the dandy:
1. Sheet too wet under dandy.
— reduce the amount of water in the sheet or lower the slice.
— put on additional wet boxes or increase vacuum on drainage elements if possible.
2. Ensure sufficient clearance between dandy and forming fabric.
3. If suction box skipping or missing, correct or shut off box.
4. Reduce refining or increase white water temperature to free up stock.
— slow stock contributes to crushing.
5. Check dandy speed.
6. Check that dandy roll is clean.
7. Check operation of dandy suction box.
See Crushing, dandy roll.
At the presses:
1. Dirty or filled felt.
— need to reduce press loading and wash felt at first opportunity.
2. Closed felt due to a crooked truing line that should be straightened.
3. Tighten the felt if it is too slack.
4. Insufficient suction press vacuum not removing enough water.
— need to determine the reason for below normal vacuum.
5. Determine the reason for excessive moisture in the sheet and correct, or slow down machine.
6. Check operation of felt conditioning equipment and rectify or report any malfunction immediately.
— clean or replace worn or dirty felts.
— increase Uhle box vacuums.
7. Reduce refining if stock conditions permit as slow stock contributes to crushing.
— increased stock temperatures helps drainage.
8. Plugged press pan causing water to drop on felts.
9. Improperly fitted press doctor blade or defective roll surface water wipe.
10. Press rolls not correctly couched or suction box not set properly.
11. Plugged or broken fog shower nozzles.
12. Check for proper water removal from grooved press rolls.
13. Check grooved press geometry, purging shower angle, shower water pressure, and nozzle cleanliness.
14. Check showering of the press rolls and shower water pressure.
15. Check dewatering elements on forming table.
16. Review felt design for application.
17. Check stock freeness and refining control.
18. Check basis weight and moisture profiles entering press.
19. Check press loading and hardness of covers.
— reduce press loading if necessary.
20. Check for ash variation.
21. Lower headbox consistencies ensure the break-up of any stock lumps and prevent flocculation.
See also Crushing, press.