Dirty felts

1. Usually due to poor cleaning.
— unblock shower nozzles.
— check shower water pressure and temperature.
2. Check suction box condition and vacuum level.
3. Check chemical usage levels.
— if alum, retention aid or wet strength are not correct, materials can collect in felts.
4. Check felt tensions.
— adjust felt truing line if needed.
5. Check press crown roll versus loading.
— check crown and crown curve.
6. Ensure even press loading front and back.
7. Take nip impressions and determine need for new crown combination based on operating results.
8. Check for grease on felts and clean up.
— caustic and detergent for synthetics, kerosene for others.
Note: Contaminants typically include:
— sizing agents (rosin, ASA size, AKD size, wet strength agents)
— coating materials in dryer felts (SBR, latexes, PVAc)
— organics (plastics, hot melts, stickies, oil grease, asphalt, wax, pitch)
— fiber and filler (cellulose, fines, talc, TiO2, alum, clay)
— wet strength chemicals
For more information, see Felt cleaning.