Maddocks Group

Industrial Filter Division


(905) 549-9626

663 Woodward Avenue
Hamilton, Ontario, Canada L8H 6P3

Glossary of Terms and Abbreviations

Abrasion, flex: Cloth wear in a creased area caused by excessive bending, usually associated with cage contact.

Abrasion, surface: More or less uniform wear on the dirty side of the cloth.

Acrylic: A synthetic polymerized fiber that contains at least 85% acrylonitrile.

Air Horsepower: The theoretical horsepower required to drive a fan if there were no losses in the fan, that is, if it’s efficiency were 100%.

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

Agglomerative Dusts: Dusts that, when compressed, stay in the form they are compressed into. These dusts tend to be porous and light.

Air-to-cloth Ratio: The amount of air or process gas entering the bag house divided by the square foot of cloth in the bag house.

Ambient Air: The surrounding air of the environment, a.k.a, the air one would normally breathe.

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

B-Binder SnapBand: A stainless steel band covered with material with a groove in the center in the shape of the letter B that fits into a tube sheet with a tight seal.

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

Blinding: Closing of the filter medium pores which results in either a reduced gas flow or an increased pressure drop across the medium. If the medium cannot be cleaned readily and the pores reopened, this condition is often referred to as "permanent blinding" or plugging".

CFM: Cubic feet of air flowing past a fixed location in 1 minute.

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

Calandaring: A process in which fabric passes between cold or heated rollers under high pressure; this pushes the surface fibers down onto the body of the filter medium.

Cloth Weight: Usually expressed in oz./sq. yard.

Coating: Immersing the 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 Silicone graphite.

Dust: Solid particles, usually small and light enough to be conveyed or carried in an air stream.

Dust Collector: A device used to separate dust from a stream of air or gas.

Epitropic: An impregnation treatment covering the fibers with an anti-static resin system neutralizing electrical charges that could build up during filtration.

FR: Abbreviation for Flame Retardant

Fabric: A collective term applied to cloth no matter how constructed and regardless of the kind of fiber used. In the commonest sense, 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: A type of bag frequently used on pulse-jet dust collectors. It features a thick mat of fibers supported by woven backing or scrim.

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

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

Filtration: The mechanical action of separating matter out of suspension, using a filter medium such as a cartridge or a bag.

Flat SnapBand: A stainless steel band covered with media that fits in a flat tube sheet with no groove in center.

Flame Retardant: An impregnation treatment which prevents ignition of the media by hot incandescent particles in the dust stream.

Fully Supported: The pleated media is assisted in place by means other than itself, whereas un-supported would not incorporate assistance as it would support itself.

Fumes: More often noxious suspension of minutely small solid particles in a gas or air stream, formed by the condensation of vapors with solid particles, or any smoke, vapor or gas especially when irritating.

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

Leak Through: Dust or fume that leaks through a bad bag seal or a hole or crack in the tube sheet.

Humidity: Ratio of the actual partial pressure of the water vapor in a space to the saturation pressure of pure water at the same temperature.

Manometer: An instrument for measuring pressure; essentially a U-tube partially filled with a liquid, usually water, mercury or a light oil, so constructed that the amount of displacement of the liquid indicates the pressure being exerted on the instrument.

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

Media: The porous article or mass through which a gas or liquid is passed to separate out the matter in suspension. In the case of dust collector cartridges, this is the primary component or tool in which the separation is completed.

Multifilament: Yarn composed of several filaments, which are continuous strands of fiber to indefinite length.

Napping: A scraping of the filter medium surface that raises the surface fibers, rupturing of the filling yarns to produce a fleecy surface on woven fabrics

Needled Felt: A felt constructed with 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.

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 bag house 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 burst or collapse the pipe).

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

Pulse Jet: Generic name given to all pulsing collectors.

Replacement Air: A ventilation term used to indicate the volume of controlled outdoor air supplied to a building to replace air being exhausted.

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

Scrim: A very loosely woven fabric onto which felt is needled.

Seeding: Is the application of a relatively coarse, dry dust to a bag before startup. The process provides an initial filter cake for immediate high efficiency and to protect bags from blinding. (see; Pre-coat).

Shaker Bag house: 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.

Smoke: An air suspension (aerosol) of particles, usually but not necessarily solid, often originating in a solid nucleus, formed from combustion or sublimation.

Spunbonded: A non woven fabric formed by producing, laying and self-bonding a web of filamentous material in one continuous set of processing steps, usually made of polyester, polyamides or olefins.

Tube Sheet: The steel plate that bags are suspended from in a bag house.

Twill Weave: Warp yarns floating over or under at least two consecutive picks from lower left to upper right, with the points of intersection moving one yarn outward and upward or downward on succeeding picks, causing diagonal lines in the cloth.

Wovens: Filter media fabrics constructed solely by weaving the interlacing yarns more or less at right angles into a uniform structure.

Vapor: Gaseous form of substances. Vapors diffuse and can be changed to a solid or liquid state by an increase in pressure or decrease in temperature.