PERMEABILITY / OPENNESS

All paper makers will have had to deal with 1 or more of the following problems:

  • insufficient nip or Uhle box dewatering, too long startup or break-in times
  • sheet crushing by too dense felts, due to contamination, plugging or compaction
  • sheet rewetting as felts are too open or worn
  • felt base marking or suction roll shadow marking in the sheet
  • fiber bleeding, contaminating the stretcher roll

The press felt permeability or openness is usually a delicate compromise. When the felt enters the press nip, water must flow easily through the felt – the felt must be open. Milliseconds later, exiting the press, the water inside the felt may not rewet the sheet – the felt must be as closed as possible.

 

 

Feltest products to check the openness of press felts

Feltest AirSpeed/2 – the Uhle (or vacuum) box sucks air through the press felt. The AirSpeed/2 measures that airflow accurately and reliably.

Feltest RealVac – measure the vacuum where it matters: in the Uhle box (and not at the pump).

 

 

LINKEDIN GROUP FOR PMC PROS

Join the Paper Machine Clothing Professionals group on LinkedIn. Anyone dealing with Paper Machine Clothing is invited to join this group. PMC Sales & Service Engineers, paper mill Production Managers, anyone with questions or knowledge on wires, fabrics, felts and canvas is welcome to join!

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REFERENCES

albany
andritz
asten johnson
cmpc
heimbach
international paper
kimberley clark
sca
smurfit kappa
storaenso
valmet
voith
xerium