Mechanical shakers In mechanical-shaker bag filters, tubular filter bags are fastened onto a cell plate at the bottom of the bag filter and suspended from horizontal beams at the top. Dirty gas enters the bottom of the bag filter and passes through the filter, and the dust collects on the inside surface of the bags. Cleaning a mechanical-shaker bag filter is accomplished by shaking the top horizontal bar from which the filter bags are suspended. Vibration produced by a motor-driven shaft and cam creates waves in the bags to shake off the dust cake. Shaker bag filter range in size from small, hand-shaker devices to large, compartmentalized units. They can operate intermittently or continuously. Intermittent units can be used when processes operate on a batch basis; when a batch is completed, the bag filter can be cleaned. Continuous processes use compartmentalized dust collector; when one compartment is being cleaned, the airflow can be diverted to other compartments. In shaker baghouses, there must be no positive pressure inside the bags during the shake cycle. Pressures as low as 5 pascals (0.00073 psi) can interfere with cleaning. The air-to-cloth ratio for shaker bag filters is relatively low, hence the space requirements are quite high. However, because of the simplicity of design, they are popular in the minerals processing industry.
