Ineffective cleaning in generic baghouses
In a typical “generic” baghouse application, the cleaning is accomplished by back-flushing the filter with compressed air that travels through an orifice hole in a purge tube (blow pipe) and through a venturi. A typical generic cleaning system allows dust to be filtered at an air-to-cloth ratio of 5:1. That means for every 5 CFM of airflow, there is 1 square foot of media used to filter the air. This has been the industry standard for over 50 years. This standard cleaning system is not perfect and it has several inherent problems. First, due to the proximity between the orifice and throat of the venturi, not enough clean air is induced during the cleaning cycle, and a vacuum is created. Second, due to the energy contained within the compressed air and the close proximity to the orifice, as the jet expands and passes through the venturi at high velocity, it overwhelms the surrounding media with air and can create a “puffing” effect as it drives dust from one bag to another. Lastly, due to the high velocity of air after the venturi, the induced air is forced out of the bag creating another vacuum further down the bag. As a result, there is a large section of the top of the bag that is unusable for repetitive cleaning of the dust.