Drainage and Forming Studies Using Dynamic Simulation Techniques, 1998 Engineering Conference Proceedings

In this paper we describe two forms of dynamic drainage tester based on the pressure former concept. They provide a more detailed understanding of the relationship between drainage rate, sheet grammage and formation. They are being used to provide information for the development of a mini paper machine concept based on the combination of pressure forming with hot pressing but have much wider applications.

We show how the grammage of the sheet laid down in a pressure former is limited by the permeability of the fibre layer with a ‘wet’ stock. Conversely, the grammage of a free draining stock can be limited by the bulk of the fibre layer that can be accommodated in the forming zone. These observations are the basis for understanding the relationship between drainage, sheet grammage and speed and this knowledge cannot be obtained from traditional freeness testers.

The dynamic drainage testers we describe here also have applications in the study of drainage problems both for board furnishes and for ‘white’ grades. We suggest they may be used more widely for evaluations of wet end chemistry and forming fabrics.