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Oleg Systems Co. designs industrial dust collection systems. Dust collecting equipment is available in numerous designs utilizing a number of principles and featuring wide variation in effectiveness, initial cost, operating and maintenance expense, space, arrangements and material of construction. One of the most widely used type of dust collector is Fabric Dust Collector. Fabric arresters are high efficiency, medium cost collectors. The effectiveness of passing air or gas through a fabric at low velocity has been recognized and used for many years in air cleaning devices. Fabric is arranged in envelope or tubular (stocking) shapes. While removal appears to take place by a staining action of the media, in reality dust collection is obtained by building up a mat of the material on the dirty side of the media. This mat provides the actual filtering or straining bed. By means of this bed a high degree of removal is obtained even on sub-micron size particles. The dust collectors are used extensively in industry for a wide range of applications. They require more space than most other types of air cleaning devices, necessiating outdoor installation in most cases. The usual fabric is a specially wooven cotton, altough wool, paper , glass cloth and synthetic fabrics may be used in certain applications. In recent years glass cloth has come into wide use because of silicone treatment of the glass fibers and employment of reverse flow techniques for cleaning. Silicone treatment provides a lubricant between fibers and increases fabric life. Fabric collectors are limited to air conditions dry enough to prevent condensation or free moisture deposition on the fabric. With hygroscoping materials, there will be a bonding tendency between particles and fabric under high relative humidity even though no condensation takes place. Maximum recommended temperature for cotton fabric is 180 F, for wool 200 F. Higher temperatures can be handled by using synthetic materials including nylon or orlon fabrics as well as glass cloth and, occasionally, fine metallic mesh. The synthetic fabrics mau be used up to 300 F while glass cloth is acceptable to 550 F. As dust is collected on the fabric, resistance to air flow increases. Periodically the fabric must be reconditioned by shaking, vibrating, reverse jet or reverse-flow collapse which agitates suffitiently to remove the bulk of adhering material allowing it to drop into the dust hopper. In most collectors air flow must be stopped during reconditioning, otherwise released material will be re-entrained and redeposited on the fabric. Sufficient dust must adhere to the fabric to maintain the dust mat needed for maximum efficiency; therfore, after reconditioning the pressure drop will be considerably higher than loss through new fabric. Rate of flow through the media varies with dust collector type, application and dust concentration. Ratings are usually selected so pressure drop will not exceed 5" WG. The smaller the particle, the more rapid the resistance rise for a given loading. For the same air flow rate and dust loading, resistance rise increases directly in proportion to time. Some spesific types of Fabric Dust Collectors manufactured by Oleg Systems Co. are: - Intermittent-Duty Fabric Collectors These types may use either envelope or stocking arrangement of the fabric but will generally employ shaking or vibrating as a means of reconditioning. Periodically Uusually at 4 to 6 hour intervals0 the air flow must be stopped to effect reconditioning - thus the classification "intermittent". - Multiple-Section, Continuous-Duty, Automatic Fabric Collectors The disadvanteges of stopping the air flow to permit vibration and variations in the airflow can be overcomed by using of sectional arresters allowing continuous operation of the exhaust system as automatic dampers periodically take one section out of service for reconditioning the fabric while the remaining sections take the entire gas volume. - Reverse-Jet Fabric Collectors The reverse-jet type differs from the conventional arrsters in its use of high pressure air to clean the fabric. One type uses high pressure air (30" - 40" WG) from a travelling "blow ring" to dislodge the collected cake from inside the fabric tube. Another type uses high pressure compressed air (100 PSI) to break the dust cake from the exterior of the fabric tube or envelope by the intermittent application of reverse-jet compressed air. - Reverse-Flow Collapse, Continuous-Duty Collectors Reverse-flow collapse cleaning is generally used with glass media which is fragile and requires a gentle cleaning technique. Reversing the glass flow provides a gentle collapse of the fabric usually in a "four point star" braking the dust cake which falls by gravity into the hopper. For additional information please refer to http://olegsystems.com/scrubber/Index.html. Oleg Chetchel Canadian Air Systems Designer Oleg Systems Co. http://olegsystems.com/dustcollector/Index.html http://olegsystems.com/airknife/Index.html
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