Equipment Description:Cleaning & Conditioning
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Paper stock contains fines, which are small particles, that can get trapped inside the complex matrix of the Fourdrinier wire fabric. Cleaning the wires is essential to maintain consistent drainage characteristics and machine performance. Cleaning is done using high pressure sprays which may also carry intermittent doses of conditioner to maintain the fabric weave. |
Headbox: This is the unit which controls the delivery of dilute stock going onto the Fourdrinier wire. Formation: This is the term used to describe how the fibres are laid down to make a sheet of paper. Consistency:This is the percentage figure of dry fibres in the water, for example, 2% consistency means 2 grams of dry fibre for every 98 grams of water. Vacuum Boxes: These units are used for forced dewatering, initially at low vacuum after the Hydrofoil units. Wire: This is the continuous mesh belt on which the sheet of paper is formed. |
 Typical Shower locations for a Wire section |
The above diagram shows the layout for a Crescent Former as used in Tissue manufacture. There are four showers, three for cleaning and one for conditioning, labelled ‘Chemikal’. The cleaning showers are needle jets which oscillate back and forth across the machine. The period of oscillation is carefully chosen to avoid marking the fabric or wire. The needle jet sprays operate at high pressure, requiring a high pressure supply pump. The liquid is water, either fresh water, or, filtered, recovered, white water. Using white water can prevent pH shock onto the wire, reducing the risk of chemical deposits. The conditioners are typically solvents to disperse pitch deposits. Many synthetic wires are not alkali resistant, so caustic cannot be used. The needle jet cleaning sprays blast the wire from the inside of the wire loop to the outside. This is to push the dirt out rather than forcing it further into the wire matrix. The angle of the sprays can be set to produce different effects. Depending on the application the jet will have either a tangential or a perpendicular force. |
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