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Headbox pressure pulsation
 
Problem:
The production speed of the paper machine was limited due to the unstable releasing of a paper web from the press
section’s center roll.
Causes of the problem:
The primary problem was caused by too-powerful pressure pulsation in the headbox’s slice chamber.

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Pressure pulsations were caused by three factors;
 

 1. Unstable air pressure in the headbox air cushion, which resulted from the fact that the air cushion’s pressure discharged
     through the overflow pipe to the wire pit.

 2. The supply pressure valve, which takes care of the headbox’s level, was broken
 3. The roll-rate control of the headbox supply pump amplified the pressure pulsation of the headbox due to a synchronization
     of the pressure pulsation frequency and the frequency of the roll-rate control.
Solution;
 

 •  The supply pressure valve was replaced with a new one
 •  The headbox level was corrected
 •  The roll-rate control of the headbox supply pump was
     reparameterized

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