Reverse Air Baghouses
These are also called “low air to cloth ratio filters”.
The Reverse Air Baghouse is one of modular construction. As occurs in most inside/outside filtering modes, dust enters the hopper and the dust that is not deflected down into the hopper, rises up to the filter media.
In reverse air cleaned installations the bags are supported by and tensioned to a structural framework at the top (end cap and spring tensioner) and clamped to a thimble that is welded to the tube plate/sheet at the bottom.
The thimble assembly function is twofold:
- Allows the filter bag to firmly attach and seal to the bottom cell plate;
- It works as a straightening collar for dust-laden air to correct the path of the off-centre flow to prevent abrasion on the lower portion of the filter bag.
As in most systems, the dust is allowed to cake on to the surface of the filter media until such time as air flow is sufficiently impeded to warrant the dust cake removal. This is done by taking the compartment offline from the positive pressure fan and putting the compartment under negative pressure via draft from the other compartments connected via a common dust or by a separate reverse air fan duct work assembly.
This causes the filter bag to collapse which releases the filter cake from the filter bag. Evenly spaced anti-collapse rings hold the filter bags open enough to prevent the dust cake from impinging and causing a blockage to the free flow of the dust cake from the filter bag.