The bag’s role in a jet filter
In a mill’s aspiration and pneumatic conveying systems, air cannot be released to atmosphere until the flour dust is removed. Pulse-jet filters do this. Dusty air passes from the outside to the inside of the filter bags; dust stays on the outer surface and clean air leaves up through the bag. At intervals a pulse of compressed air is fired into the bags, shaking the dust cake off into the hopper.
Choosing the fabric
Mill filters usually use needle-felt (polyester) bags. Fabric weight, air permeability and surface finish set dust capture efficiency and how well the bag cleans. Calendered or specially treated surfaces help sticky dusts such as flour release more easily.
Differential pressure: the bag’s health indicator
The pressure difference across the filter is the best guide to bag condition:
- Steadily rising differential pressure: bags are blinding; check cleaning air, moisture and bag age.
- Sudden drop: a bag may be torn or dislodged; dust may also be visible at the outlet.
Replacement and fitting
A torn bag causes dust emission and faster wear of neighbouring bags. When fitting, make sure the cage (filter wire) is straight and burr-free and that the bag mouth seals properly in the plate. Send us the bag diameter, length and mouth type and we will prepare the right bags.
