Press optimization: longer felt service life – less felt barring

Insufficient felt service life, increased vibrations or felt barring often appear with presses. If rolls with grooved steel covers are used, then improvements can be achieved by attaching a polyurethane cover to the grooved steel cover.

It is softer, which leads to a wider nip (lower Hertzian contact pressure) and a lower maximum hydraulic pressure in the press gap. The mechanical stress on the felt (compression) is thus noticeably reduced. The damping characteristics with PU lower the sensitivity to vibrations and can clearly reduce felt barring. The amount of heat generated in the PU cover by the damping is calculated and must be discharged by means of suitable cooling, if applicable.

The steel grooves are closed with epoxy resin before rubberization. Then the polyurethane layer is attached and subsequently grooved and polished.

The rubberization of the grooved steel cover with PU is current best practise in the paper industry. The alternative of removing the grooved steel cover would involve clearly higher costs. The form deviations to be expected in the roll pipe would cause additional technical risks.

The effects of the roll’s modified geometry on the entire press are investigated by a Voith specialist in pre-engineering. Doctoring, lubrication and cleaning must be adapted to the requirements of the PU cover. All required changes are compiled in a catalogue of measures.


Customer benefits
• PU cover instead of grooved steel cover due to rubberization
  – without expensive and technically risky removal of the grooved
  steel cover
• Extension of felt service life
• Reduction of sensitivity to vibrations (felt barring)
• Increase in production speed possible

Related products, services & rebuild solutions
Paper machine process optimization.