The Design Of A Novel Instrument Of Pore Size Of Filter Cloth And The Research Of Filtering Precision

The equivalent pore size is an important indicator during manufacturing and using woven filter cloth. At present, there is not a complete standard on woven filter cloth in China, which results in manufacturing and marketing by experience, not in accordance with standards. The definition of filtering precision varies worldwide. Furthermore, the experiment on measurement of filtration precision via particle transmission is expensive and time-consuming without a unified standard. Therefore, the present situation necessitates the design of an equipment to measure the equivalent pore size easily and precisely and the further discussion on pore size of filter cloth. Moreover, the relationship between the equivalent pore size and filtering precision is established, and the relevance between the equivalent pore size and weaving process is explored, which gives a basis for selection and design of filter cloth.In this article a novel measurement method for equivalent pore size of filter fabric through a stable bubbling phenomenon is given on a principle that liquid pressure increases with increment of liquid depth and bubble point theory. The sample is placed vertically for the first time with liquid and gas on each side. Meanwhile, the distribution of liquid pressure on the sample is different, but the distribution of liquid pressure is the same. The bubbles are forced through pores into liquid by gas pressure, and the number of the bubbles decrease and even disappear with increment of liquid depth. Random pore size can be measured by this method, and then the mean value of the pore size is regarded as equivalent pore size of the sample. Scatter range of measurement value is evaluated by type A uncertainty. Through measuring five different filter fabrics, the uncertainty values less than3.00validate the stability and reproducibility of this novel method for the measurement of pore size.Filtering precision is described using maximal particle size in filtration, D98and half-content diameter D50and the effect of warp density and weft density on pore size is discussed in this study.3/3twill-weave filter cloths with different warp density and weft density are employed. The suspension with certain concentration of clay powers with widely distributed diameters is prepared. After the filtration experiment with filter fabric, D98and D50are obtained by Laser Particle Size Analyzer (LPSA).The equivalent pore sizes of the samples are measured using the designed instrument. The functional relationships between equivalent pore size and D98, between equivalent pore size and D50are described, respectively. Moreover, the regression equations of pore size and warp density, pore size and weft density, and of all three are established. These regression equations quantitatively demonstrate the influences of warp density and weft density on pore size of filter cloth.Discussing the equivalent pore size, D98, D50, warp and weft density, the reference for design of the filter cloth are provided, resulting in more accurate and handy selection of filter cloth. The designed equivalent pore size measuring equipment could bring convenience and economic benefit to many filter cloth manufacturers. Furthermore, our research could be helpful to establishment of filter cloth industry standard of China.