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Pleated Dust Collector Bag Filters

Pleated Media Bags

A pleated dust collector bag is a bag made of a length of filter media folded into numerous pleats and shaped like a cylinder. The pleats are made such that the outer diameter of the pleated bag matches the outer diameter of a regular cylinder filter bag. The filter media is then fitted to the bottom end cap and top sleeve arrangement and the bag cup is attached. The spacing of pleats is normally kept at 2-3 times the area of cylindrical bags which gives it that much extra filter media for the same space consumed. The inside diameter of pleated bag filters are less than that of the cylindrical bags owing to pleat depth reducing the inner diameter. However the small inner diameter is of no consequence for filtering and cleaning activities.

Pleated Bags Verses Fabric Bags

Pleated filters were designed for applications that could not be efficiently handled by traditional dust collector bags in fabric collectors. With their greater efficiency, they are now used in place of conventional cylinder dust collection bags.

Advantages of Using Pleated Bags in Collectors

• Pleated media filters can be installed over existing filter baghouses (and thereby improve efficiency without changing too many parts of the collector)
• Dust collector bag filter media increases by 2-3 times due to pleating.

• Cleaning air gets scattered due to the pleating. This loss of speed reduces dust penetration on adjacent bags and contributes to greater system efficiency (pulse cleaning can be done effectively at lesser pressure). However in systems where pleated bags are installed over existing baghouse designs, cleaning capacity pertains to the older design (which is much lower). This may not clean much of the pleated media and causes plugging.
• Operating pressure differential could be reduced provided existing cleaning air jet is sufficient to clean the extra filter media (pleats)
• Could reduce size of the collector itself due to increase in filter media area within a smaller space

Disadvantages of Using Pleated Bags in Collectors

• Cost of pleated bag is much higher when compare to standard baghouse media
• A pleated bag filter collector system cannot be reversed into standard bags because it is designed to handle larger filter media areas. If considered, the reduction could be ½ to 2/3 of pleated bag design.
• When replacing an existing baghouse, the original cleaning capacities do not efficiently clean extra filter media of the pleated bag. This could lead to plugging
• If pleated media has lower Frasier Permeability rating, then filter media may need to be added to restore equivalent fan air CFM at the given pressure rise in inches WG

Design Characteristics of Pleated Bags

Pleated bags are provided with an inner core that adds strength and rigidity. Bands are placed on the outside and they assist in maintaining the shape of the cylindrical bag during cleaning (prevents bulging). Pleat depths could vary from 0.6 inches to 1.875 inches, which is the equivalent of the outer bag diameters of 4 ½ inches to 8 inches. The bag height could vary from 24 inches to 90 inches and bags could have both top and bottom removal styles.
Bottom removal pleated bags are first placed in a compatible bag cup mounted on the tube sheet. A band clamp is left hanging limply over the urethane top of the pleated bag that is fastened after the bag is in place. Top removal bags do not require bag cup and the pleated bag is normally fastened to the tube sheet by a snap band.

Bags can be made of standard spun bonded polyester material or of specialized material to achieve higher efficiency and dust cake release. The specialized material that could be used are (i) hydro and oleophobic finish (water and oil proofing) (ii) static dispersion membranes and (iii) PTFE membranes.

Design Considerations for Pleated Bags

Pleated bags are designed to withstand chemical attack and high temperatures (upto 200° F). They are provided with positive sonic fused seaming and a positive interlocking seal with molded urethane at the top and bottom.

Pleated bags are ideally considered to replace baghouse air jet cleaning systems when filter media in the existing baghouse system loses it capability to prevent operating pressure from rising beyond acceptable levels. The efficiency of the replaced system increases when the existing cleaning system has additional cleaning capacity to clean the extra filter media that comes with pleated filter bags.