Industrial Dust Collector Services since 1994
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Glossary of Dust Collector

Abrasion, flex: Wear on cloth in a creased area due to flexing, normally associated with cage contact.

Abrasion: Wear on the dirty side of the cloth.

Acrylic: Synthetic polymerized fiber with approximately 85% acrylonitrile.

Air Horsepower: Horsepower required to drive a fan at 100% efficiency

Air, Standard: Dry air at 70 F and 29.92 in (Hg) barometer. This is equivalent to 0.075 lb/cu ft.  Specific heat of dry air = 0.24 BTU/lb/F.

Air-to-cloth ratio: The amount of air or process gas entering the baghouse divided by the sq. ft of cloth in the baghouse.

Aspect Ratio: The ratio of the width to the length. AR = W/L

Aspect Ratio of an Elbow: The width (W) along the axis of the bend divided by depth (D) in plane of bend. AR = W/D

Blast Gate: Sliding damper

Bleed: Particles of dust or fumes that are able to migrate through the bag. (also leak)

Blinding: Closing of the filter medium pores resulting in reduced gas flow or an increased pressure drop across the medium. If medium cannot be cleaned easily and the pores opened, it is called as "permanent blinding" or plugging".

Brake Horsepower: Horsepower actually required to drive a fan. This includes the energy losses in the fan and can be determined only by actual test of the fan.

Bridging: Blockage of dust across an opening such as a hopper outlet or between bags.

Cake: The dust formation developed on the surface of the filter medium during the filtration process.

Can Velocity: The theoretical speed of dust laden air as it passes upward between the filter bags. The formula for calculating can velocity is as follows: The square area of the baghouse (length x width) minus the area occupied by the bottom of the bags (the sum of the areas of the number of bags) divided into the volume of air in ACFM given as velocity in fpm.

Capture Velocity: The air velocity at any point in front of the hood or at the hood opening necessary to overcome opposing air currents and to capture the contaminated air at that point by causing it to flow into the hood.

Coating: Dipping filter medium in a solution to provide the fibers with a coating that will lubricate and thereby reduce self-abrasion; in the case of woven-glass bags, the most common coatings have been Teflon and Siliconegraphite.

Cold Spot: The spot on an insulated baghouse where a continuous metallic heat transfer circuit through the insulation creates an uninsulated area.

Concentration: Amount of dust in the gas. Usually expressed in terms of grains/cu ft., pounds/hour.

Density: The ratio of the mass of a specimen of a substance to the volume of the specimen. The mass of a unit volume of a substance. When weight can be used without confusion, as synonymous with mass, density is the weight of a unit volume of a substance.

Density Factor: The ratio of actual air density to density of standard air. The product of the density factor and the density of standard air (0.075 lb/cu ft) will give the actual air density in lbs per cu ft. d x 0.075 = actual density of air, lbs per cu ft.

Diaphragm Valve: Compressed air operated valve used to pulse bags.

Dust: Small solid particles that are created by the breakdown of larger particles by processes such as crushing, grinding, drilling, explosions, etc. Dust particles are carried around into the environment through operations such as shoveling, conveying, screening, sweeping, etc.

Dust Collector: An air cleaning device to remove heavy dust particles from exhaust systems before discharge to outdoors. Usually in the range of 0.003 grains per cubic foot and above.

Dust Loading: The quantity of dust in the gas stream, usually expressed as grains of dust per cubic foot of air.

Entry Loss: Loss of pressure caused by air flowing into a duct or hood (inches H20).

Fabric: A term applied to cloth irrespective of construction and kind of fiber used. In common parlance, it refers to a woven cloth.

Felt: Fabric structures constructed by the interlocking action of the fibers themselves, without spinning, weaving, or knitting.

Felted Bag: Type of bag frequently used on pulse-jet dust collectors. Features a thick mat of fibers supported by woven backing or scrim.

Filter Cake: The dust accumulation on a bag. Often assists in the filtration process. Also see cake.

Filter Media: The permeable membrane employed in the filtration process to separate the particles from the fluid stream.

Filtration: A process by which particles are separated from a fluid stream by use of a permeable membrane.

Fumes: Small solid particles formed by the condensation of vapors of solid materials.

Gas-to-Cloth-Ratio: The amount of process gas entering the fabric filter dust collector divided by the amount of cloth area filtering the dust from the air. Normally the gas flow is given in CFM and the cloth in square feet.

Gases: Formless fluids which tend to occupy an entire space uniformly at ordinary temperatures and pressures.

Glazing: High-pressure pressing of the filter medium at elevated temperatures; fuses surface fibers to the body of the filter medium.

Grain: A dust-weight unit commonly used in air pollution control. Equal to 1/7000 lb.

Grain Loading: Grains of dust per CFM.

Gravity, Specific: The ratio of the mass of a unit volume of a substance to the mass of the same volume of a standard substance at a standard temperature. Water at 39.2 F is the standard substance usually referred to. For gases, dry air, at the same temperature and pressure as the gas, is often taken as the standard substance.

Header: A pressurized pipe that contains the compressed air supply for a pulse type baghouse.

Hood: An inlet designed to catch contaminated air and conduct it into the exhaust dust system.

Humidity, Absolute: The weight of water vapor per unit volume, pounds per cubic foot or grams per cubic centimeter.

Humidity, Relative: The ratio of the actual partial pressure of the water vapor in a space to the saturation pressure of pure water at the same temperature.

Hydrophobic Fibers: Fibers that do not absorb water easily.

Hydrophilic Fibers: Fibers that easily absorb water.

Inch of Water: A unit of pressure equal to the pressure exerted by a column of liquid water an inch high at a standard temperature.

Interstices: Openings between the fibers in a woven or felted filter bag.

Manometer: An instrument for measuring pressure.

Micron: A unit of length, the thousandth part of I mm or the millionth of a meter (approximately 1/25,000 of an inch).

Minimum Design Duct Velocity: Minimum air velocity required to move the particulates in the air stream, fpm.

Mists: Small droplets of materials that are ordinarily liquid at normal temperature and pressure.

Needled Felt: A felt constructed by the use of barbed needles moving up and down, pushing and pulling the fibers to form an interlocking of adjacent fibers.

Permeability: A measure of fabric porosity or openness, usually expressed in cfm at a 0.5" H20 pressure differential.

Plenum: Pressure equalizing chamber.

Pre-coat: Material added to air stream on initial process startup to aid in establishing filter cake on bags.

Pressure Drop: Resistance to air flow; may refer to pressure differential across the cloth, across the baghouse or the pressure drop across the entire system.

Pressure, Static: The potential pressure exerted in all directions by a fluid at rest. For a fluid in motion it is measured in a direction normal to the direction of flow. Usually expressed in inches water gauge when dealing with air. (The tendency to either burst or collapse the pipe).

Pressure, Total: The algebraic sum of the velocity pressure and the static pressure

Pressure, Velocity: The kinetic pressure in the direction of flow necessary to cause a fluid at rest to flow at a given velocity. Usually expressed in inches water gauge.

Pulse Cycle: The interval of time between one pulsing of a row of bags and the next pulsing of the same row.

Pulse Interval: Time between pulsing one row of bags and pulsing the next row.

Pulse Jet: Generic name given to all pulsing collectors.

Re-entrainment: The re-depositing of dust on the filter bag surface after it has been pulsed off. Re-entrainment is usually caused by turbulence in the hopper or dirty air plenum.

Reverse-Air Baghouse: A unit employing reverse flow flushing air to clean the dust from the bags.

Shaker Baghouse: A unit wherein cleaning is accomplished by shaking the bags.
Singeing: Passing of the filter medium over an open flame, thereby removing the protruding surface fibers.

Slot Velocity: Linear flow rate of contaminated air through cloth, fpm.

Temperature, Effective: An index which combines into a single value the effect of temperature, humidity and air movement on the sensation of warmth or cold felt by the human body. The numerical value is that of the temperature of still, saturated air that would induce an identical sensation.

Vapor: The gaseous form of substances which are normally in the solids or liquid state and which can be changed to these states either by increasing the pressure or decreasing the temperature.