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Moisture profile problem
 
Problem:
The problem was the askew moisture profile of the paper web, which caused – in addition to a quality
problem – e.g. runnability problems in the paper machine.
The customer determined from their own studies that the problem originated in the press section.
 
Causes of the problem:
In order to tackle the problem, the functioning, mechanical condition and real nip loads of the loading
system of the press section’s nips were examined. The results indicated that the original reason for the
askew moisture profile was the nip load differences between the front and back sides of the 3rd press.

 case71
The moisture profile of the 3rd press felt also supported the askew nip loads of the 3rd press.
The back side of the 3rd press felt was significantly drier than the front side..

case72
case73
Solution:
The mass distribution of the 3rd press roll was uneven between the front and back sides. The back side of the roll was much heavier due to roll gear and drive shaft.
The machine supplier had not taken this into account for this mass distribution difference in determining loading curves. This caused the nip load (kN/m) on the back side to be much higher than the front, when the loading pressure (MPa) was the same at both sides of the nip roll.
The problem was solved after the new loading curves were brought into use.

case74
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