IQS Newsroom Articles on Baghouses
Baghouses
Baghouses are
dust collection fabric filters that minimize air particle contamination in workshops, plants and manufacturing facilities through the use of air flow through filter bags to capture particulate matter. The most common type of dust collector, a baghouse is also one of the most cost-effective and efficient types with a typical rate of fine particle capture of more than 99%. Any process which emits smoke, dust or particles into the air is held by industry-specific state OSHA regulations to filter facility air. As a result, baghouses are vital equipment for coal handling, cement fabrication, metal fabrication, pharmaceutical, chemical processing, woodworking, recycling and agricultural industries, among many others. Typical baghouse dust collector applications include dust capturing, separating and filtering explosive media, metalworking chips or fluid, toxic media, welding fumes and coolant or oil mist.
Baghouses draw contaminated air in through ducts to a hopper-shaped baghouse containing fabric filters. The air is pulled through the fabric bags by a vacuum-creating fan, leaving behind dust, smoke and particles; clean air exits through the fan at the outlet at the top of the baghouse, while dust particles settle into an airlock at the bottom of the hopper, which is routinely emptied. During the process, the baghouse filters accumulate a layer of dust called filter or filtering cake. Filter cakes create a barrier capable of capturing fine dust particles through four mechanisms: intertial collection, interception, Brownian moment and electrostatic forces. Facilities usually incorporate bag houses into large dust collecting systems, with overhead ductwork and capture arms (suction hoods) which hang over the workspaces where dust is formed. In large facility applications, the baghouse is often located outside, connected to the interior through ductwork. Common materials used to make bag houses include cotton, glass-fiber and synthetic materials. Typical baghouse and baghouse filter designs include envelope or tube shapes.
There are three main types of baghouses: mechanical shakers, reverse-air and reverse-jet. Mechanical shaker baghouses clean their filter bags through vibrations caused by a motor-driven shaft and cam. These vibrations cause waves in the bag that shakes the dust cake off the inside surface of the bag and into the hopper. Reverse-air baghouses are compartmentalized and allow for continuous operation during their cleaning cycle. In order to begin cleaning, filtration is halted in the compartment about to be cleaned. Clean air is then injected into the dust collector in a reverse direction, which pressurizes the compartment and causes the filter bags to partially collapse. This results in the filter cake cracking and falling into the hopper below. Reverse-jet baghouses also allow for continuous operation during their cleaning cycle, but are typically not compartmentalized. Instead, the filter bags are cleaned by short bursts of compressed air injected through a compressed air manifold over a row of filter bags supported by a metal cage. Compartmentalization is not necessary because the burst of compressed air is so small compared to the much larger volume of dusty air in the collector.