Barring

1. Common causes include:
— poor felt design.
— press frame vibrations.
— doctors vibrating.
— roll wipes vibrating.
— excessive cooling water inside press rolls.
2. Pulses in the stock approach flow from can cause barring:
— fan pump pulses
— selectifier screen pulses
— piping vibration at natural or harmonic frequencies
3. Barring may also be caused by slice being set too low.
— check and adjust as needed.
4. On high speed machines (3000+ fpm), any source of vibration in the press section can lead to flat spots on the roll surfaces and subsequent barring.
5. Check for vibrating dryer doctors and correct
6. Calender roll vibration.
— use wedge to stop chattering of calender roll.
— have calender roll and/or bearing changed.
See Calender barring.