All industrial baghouse systems are designed with various cleaning methods in order to ensure correct operation and longevity of the baghouse filter.
As the bag flexes, the dust cake (built up dust on surface) fractures falls into the hopper below.
Today, the most common cleaning method used in industrial dust collectors is pulse jet or reverse jet cleaning. These methods involve removing the dust from the bag filters using a blast of compressed air. The air blast creates a shock wave that causes the bag to flex or expand as the shock wave travels down the bag.
However for trouble and maintenance free operation, it is extremely important that the compressed air used in the system is clean, dry and at the correct pressure. In this article we will concentrate on the importance of dry and clean compressed air. A discussion on the importance of proper air pressure will be covered in a another article.
Clean, Dry and Oil Free Compressed Air
Dust collection filters completely covered in build-up from moisture
Dirt, rust, and scale can prevent diaphragm valves from operating properly. Moisture can cause valves to freeze in cold weather.
Moisture and oil can also cause deterioration of the valve diaphragms, and if the interior of the filter bags become coated with moisture and/or oil, eventual blinding of the filter media will occur. Blinding of the filter material occurs when the filters become so impregnated with dust in the depths of the fabric that you cannot clean them 100% anymore and the airflow through them will never go back down, resulting in premature failure of the baghouse filters.
How to ensure the Compressed Air is:
Clean
In order to trap small amounts of dirt, rust and scale, a small dirt leg is installed at the point where the air line connects to the compressed air header. In situations where large amounts of dirty rust and scale are present, and inline filter or a centrifugal separator is required.
Dry
A Liquid Moisture Trap (automatic moisture drain) must be installed on the compressed air receiver.
There are a number of solutions to ensure that the Compressed air remains dry. For example a Liquid Moisture Trap (automatic moisture drain) must be installed on the compressed air receiver. These automatic drains come in a variety of float, piston, and pilot operated types. When small amounts of moisture are present it can be handled by inline air filters with automatic drains. For large amounts of moisture, a centrifugal separator and chemical dryer may be required. For more specific situations, for example climate and indoor temperatures, other methods are used to ensure the compressed air remains dry.
Much of the above mentioned equipment used to remove moisture can also be used to remove oil and oil mist. For installations where oil and oil mist are the major problem, inline filters are available that use desiccant adsorptive elements or packed beds of an oil absorbing granular organic polymer.
Conclusion
During regular operation, Pulse Jet Industrial filtering systems do not stop the flow of dirty air into the baghouse and it is the only true “online cleaning” method.
Bag cleaning cycles are initiated to keep the overall pressure drop across the baghouse within the designed range. Therefore the importance of clean, dry, oil free compressed air cannot be over emphasized. However another important factor to take into consideration is the pressure of the compressed air. This will be discussed in an upcoming article.
