CHARACTERIZING THE DEWATERING RATE IN ROLL GAP FORMERS

A physical model is presented to predict the dewatering rate in twin-w ire roll formers. We do so by considering a series of force and mass b alances applied to the forming web. We derive expressions for both the web thickness and its apparent solidity based upon both fibre and pro cess conditions. From this, and information about the applied pressure , which we have measured experimentally, we can estimate the dewaterin g rate using Darcy's law. The validity of the model was tested at STFI on an experimental paper machine (FEX) configured for twin-wire roll forming. Good agreement was found between the experimental measurement s and the predicted inward and outward flow rates; the predictions wer e in error by about 10%.