Paper machine clothing traditionally has been evaluated by days life and cost per ton indices. Achievement of maximum clothing life and minimum cost per ton often results in significant reductions in paper machine operating performance. Sacrifices in machine performance to reduce clothing costs can reduce total mill profitability significantly. Clothing evaluation techniques based on impact on paper machine performance have been developed. These techniques relate key operating parameters to the clothing run. Techniques which have proven useful over a broad spectrum of machines are basically described. The examples focus on press fabrics, but the intention is for similar techniques to be applied to forming and dryer clothing, although the key parameters will be different.
With current technologies and much longer fabric periods, much effort goes into evaluating key parameters in real time to see what adjustments to make to keep the machine in a good operating window. For example, press fabric vacuum and water removal trends vs. days life can provide key information. Other information can also be learned from press moisture and water perm scans where they can be done safely.