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Dust Collectors General Information

General Information

Fabric Collectors

Fabric collectors remove particulate by straining, impingement, interception. The "fabric" may be constructed of any fibrous material, either natural or man-made, and may be spun into yarn and woven or felted by needling, impacting or bonding. Woven fabrics are identified by thread count and weight of fabric per unit area. Non-woven (felts) are identified by thickness and weight per unit area. Regardless of construction, the fabric represents a porous mass through which the gas is passed unidirectionally such that the dust particles are retained on the dirty side and the cleaned gas passed on through.

The ability of the fabric to pass air is stated as "permeability" and is defined as the cubic feet of air that is passed through one square foot of fabric each minute at a pressure drop of 0.5" water gage.

Dry Centrifugal Collectors

Dry centrifugal collectors (Cyclones) separate entrained particulate from an gas stream by the use of combination of centrifugal, inertial, and gravitational force. Collection efficiency is influenced by:

1. Particle size, weight and shape. Performance is improved as size and weight become larger and as the shape become more spherical.
2. Collector size and design. The collection of fine dust with mechanical device requires equipment designed to best utilize mechanical forces and fit specific application needs.
3. Velocity. Pressure drop through a cyclone collector increases approximately as the square of the inlet velocity. There is, however, an optimum velocity that is a function of collector design, dust characteristics, gas temperature and density.
4. Dust Concentration. Generally, the performance of a mechanical collector increases as the concentration of dust becomes greater.

Bag Type Collectors

Pulse Type

Reverse-Jet, Continuous-Duty, collectors generally use compressed air at a range of 80 to 100 pounds per square inch to clean the fabric. The filter elements are "pulsed" in small groups so that the whole collector is not shut down.

Shaker Type

Shaker type envelope or bag collectors need periodically cleaning (usually at 3 to 6 hour intervals), in which the air must be shut down to recondition the fabric. These types of collectors are less expensive than there continuous cleaning counter parts.

Cartridge Type Collector

Pulse Type

EPA sponsored research has shown that the superior performance results from downward flow of the dirty air stream, as shown by the diagram to the left. This is a Continuous-Duty unit that used in a verity of applications.

Shaker Type

This shaker type has specific uses were the unit can be shut down to recondition the filter elements.

Cyclones

Low Pressure Cyclone

This cyclone collector is commonly used for removal of coarse dust from an air stream, as a pre-cleaner to more efficient dust collectors and/or as a product separator in air conveying systems. 

Principal advantages are low cost, low maintenance, and relatively low pressure drops (in the 0.75 to 1.5" water gage range). It is not suitable for collection of fine particles.

High Efficiency

High efficiency cyclones exert higher centrifugal forces on the dust particles in a gas stream. Because centrifugal force is a function of peripheral velocity and angular acceleration, improved dust separation efficiency has been obtained by:

Making the cyclone body and cone longer

Using a number of small diameter cyclones in parallel

Placing units in series.

While high efficiency cyclones are not as efficient on small particles as fabric or other collectors, their effective collection range is appreciably extended beyond that of other mechanical devices. Pressure losses of collectors in this group range from 3 to 8" water gage.

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Copyright © 2002 RPS Associates of New England Inc.
Last modified: April 21, 2003