Three dimensional visualization and characterization of paper machine fabrics and their relationship to their properties and dewatering performance

X ray computed tomography is a reasonable method for accurately visualizing the three-dimensional structure of press felts. Using the 3D images and the structural characteristics of felts cane be studied: porosity, yarn-pore interfacial area, inter fiber 3D pore size distribution and 3D yarn size distribution Z-directional (thickness) distribution of structural characteristics. In majority of the cases, for the same felt, the top layers of the felt have a relatively lower porosity compared to the bottom layers. Weighted mean porosity, mean pore size and pore size distribution tend to directly correlate well with the experimental air permeability measurements higher porosity and larger pore size corresponding to higher air permeability. Felt design: a more compact structure contributes to lower porosity and lower permeability; the middle layer contributes to majority of the sample volume. Sheet rewetting influenced by: top (cap) layer porosity, mean fiber(yarn) size, mean pore size and pore size distribution; narrow pore size distribution (pore size over a small range) - lower rewetting.