the fixed mechanical cage is a cage nested inside the fixed cage that can be actuated to impact the inside of the filter bag. This beating action accomplishes the same desired effect of creating a force that dislodges the particulates as the cage moves. Cleaning sequences Two main sequence types are used to clean baghouses: Intermittent (periodic) cleaning Continuous cleaning Intermittently cleaned baghouses are composed of many compartments or sections. Each compartment is periodically closed off from the incoming dirty gas stream, cleaned, and then brought back online. While the individual compartment is out of place, the gas stream is diverted from the compartment’s area. This makes shutting down the production process unnecessary during cleaning cycles. Continuously cleaned baghouse compartments always filtering. A blast of compressed air momentarily interrupts the collection process to clean the bag. This is known as pulse jet cleaning. Pulse jet cleaning does not require taking compartments offline. Continuously cleaned baghouses are designed to prevent complete shutdown during bag maintenance and failures to the primary system. Performance Baghouse performance is dependent upon inlet and outlet gas temperature, pressure drop, opacity, and gas velocity. The chemical composition, moisture, acid dew point, and particle loading and size distribution of the gas stream are essential factors as well. Gas temperature – Fabrics are designed to operate within a certain temperature range. Fluctuation outside of these limits, even for a small period of time, can weaken, damage, or ruin the bags. Pressure drop – Baghouses operate most effectively within a certain pressure drop range. This spectrum is based on a specific gas volumetric flow rate. Opacity – Opacity measures the quantity of light scattering that occurs as a result of the particles in a gas stream. Opacity is not an exact measurement of the concentration of particles; however, it is a good indicator of the amount of dust leaving the baghouse. Gas volumetric flow rate – Baghouses are created to accommodate a range of gas flows. An increase in gas flow rates causes an increase in operating pressure drop and air-to-cloth ratio. These increases put more mechanical strain on the baghouses, resulting in more frequent cleanings and high particle velocity, two factors that shorten bag life. Design variables Pressure drop, filter drag, air-to-cloth ratio, and collection efficiency are essential factors in the design of a baghouse. Pressure drop (ΔP) is the resistance to air flow across the baghouse. A high