In the past, when ultrasonic seam welding technology was not readily available, filter bags were mostly sewn, then turned inside out in order to minimise needle hole bypass effect. Then too, with stitching there is the added danger that loose fibres could migrate through the stitch holes so possibly contaminating filtrates.
The picture alongside shows a stitched bag on the left with a welded bag on the right. It is clearly evident that there is bypass through the stitch holes as the product squirts out to the left whereas the welded bag only allows the product to drain downwards.
Our ultrasonic seam welded bags are double welded, first induction welded and then ultrasonic welded making them twice as strong as sewn bags.
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