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Jun 19, 2017

The principle of String Wound Cartridge Filters

1. In the process making string wound filters, the special roving with fluffy is coiled in the porous central core, and enwind layer-by-layer to the nominal diameter.Roving will cross enwind repeatly then form as a filter layer with thousands of rhombus holes. The rhombus holes in the filter layer will be smaller and smaller to central core, and it will be bigger and bigger to outermost layer .The outermost layer’s rhombus holes is the biggest, the rhombus holes pass through will formed as the passway.


In order to increase the liquid flow in the filter, the rhombus holes’s passway is curved and scattered,  but the layers of rhombus holes are still connected. Bending the diamond-shaped hole passway extension, increasing the thickness of filter layer can improve the filter effect. This is the principle how depth filtration works.The size of innermost layer’s rhombus holes is the key to determine the filter’s accuracy . The smaller of rhombus holes, the higher filter accuracy will be .The bigger of rhombus holes, the lower filter accuracy will be.
There is a filter accuracy comparison table which can refer to the specific rhombus holes in filter manufacture. The number of different passway is on behalf of different filter accuracy. In general, the 8-passway accuracy is 100 μm, the 15-passway accuracy is 20 μm, and the 19-passway accuracy is 10 μm.

               The schematic diagram of string wound filter

2.The filtration principle of string wound filter.
The filtration of string wound filter cartridge not only including the aperture grid block effect which formed by the filter’s roving overlapping, but also the hooking effect of the passway’s fiber and deposition effect of the particles in the passway.
A. The Fiber’s hooking effect in the passway
The liquid is pass through a narrow long and curved passway from the outer filter from the outer Filter layer to the inner layer.
The curly fiber’s fluff is bestrew in the Filter’s passway,
It can hook up the particles in the liquid and make it stay in the passway.
The schematic diagram of different passway ‘s profile.

       Eighth passway                Fifteen passway              Nineteen passway


B. The deposition effect of particle in the filter’s passway.
The passway is narrow and curved, the liquid will through and impact passway,
The particle in the liquid will deposited in the passway, just like the sludge deposited in the crook position when the water flows through the river.
3. Another feature of the string wound filter is passing through large flow,
There is a constant passway number which refer to filter accuracy D.
Once the filter accuracy is determined , the number of passway will increase or decrease according to the different length of the filter.
The formula of the passway number´╝Ü
The total number of passway = D × L × 2.