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Home >> Fabric Filters >> Glossary

Fabric Filters Terminology        

Glossary

The following is a glossary of terminology used in fabric filters. It may be of assistance when discussing your issues with our technicians and engineers.

Fabric Filter, Bag Filter, Baghouse A box containing fabric material as a filtration medium
Reverse Air or Reverse Flow A fabric filter where a compartment is isolated and low pressure air passes through the fabric in the reverse direction to normal air flow.
Reverse Jet or Reverse Pulse A fabric filter where a shot of high pressure compressed air passes through the fabric of one row of bags in the reverse direction to normal air flow.
Shaker A fabric filter where a compartment is isolated and the bags of that compartment are shaken by mechanical means.
Particulate Dust particles
Fume Very fine particulate.
Tube Sheet Metal sheet to which bags or other collection media are attached.
Bag Material formed into a shape usually cylindrical, open at one end and capped at the other end.
Cage Structure for support of the bag to prevent collapse under normal air flow conditions.
Diaphragm Valve Pneumatically operated valve connected between the filter air header and the blow pipe.
Pilot or Solenoid Valve Small electrically operated unloading valve to operate the diaphragm valve.
Blow Pipe or Blow Tube Pipe running over the top of a row of bags with outlet holes over the centre of each open bag top.
Air Header Manifold for connection of all the diaphragm valves serving the filter.
Snap Cuff Metal band at the open end of a bag for snap fitting into the tube sheet.
Cell Isolatable section of a filter system.
Module Transportable filter box.  May be an isolatable section of a filter system.
Filtration Velocity Commonly expressed in terms of m/min (=(m3/min)/m2) or ft/min (=cfm/ft2) of air through the filter medium.
Air to Cloth Ratio As for Filtration Velocity.  Commonly used in imperial system e.g. ratio = 5:1, based on acfm/sq ft.
Can Velocity In an updraught pulse jet unit only. This is the velocity of the gas as it passes by the base of the bags. If this velocity is too high it will inhibit the dust movement from the bags to the hopper.
Demand Cleaning Cleaning cycle is initiated upon pressure differential across filter medium.
Timed Cleaning Cleaning by set time periods only
Forward Pressure Pressure differential across the filter medium as a result of normal air flow.
Reverse Pulse Pressure Pressure generated by reverse thrust of air.
Hygroscopic Particulate Particulate that readily absorbs moisture.
Incandescent Particulate Particulate that is still alight or readily flames upon contact with oxygen, e.g. fly ash from wood fired boilers.
Ceramic Element Filter medium manufactured from ceramic based materials.
Metallic Element Filter medium manufactured from metallic fibres or powders.

Parameters

gas Formless state of matter completely occupying any space.  Air is a gas.
Gas volume or
Volumetric flow rate
Usually expressed as quantity of gas per unit of time.
A Prefix meaning the Actual gas conditions within the duct or vessel (including moisture content).
N Prefix meaning the"Normal" gas conditions which is the actual gas volume recalculated at 0°C and 101.325kPa.
dry (d) Flue gas volume expressed as a hypothetical value, where the water vapour in the gas is removed.
wet Flue gas volume including moisture.  Assume gas is wet unless stated otherwise.
Am3/hr or m3/hr Actual cubic metres of gas per hour.
Am3/s or m3/s Actual cubic metres of gas per second.
Nm3/h Flue gas volume expressed at "N" conditions.
Nm3/h dry Flue gas volume expressed at "N" conditions with water vapour removed.
acfm Actual cubic feet per minute.
scfm Standard cubic feet per minute is the volumetric flow rate of a gas corrected to "standardized" conditions of temperature and pressure. However, great care must be taken, as the "standard" conditions vary between definitions and should therefore always be checked. Worldwide, the "standard" condition for pressure is variously defined as an absolute pressure of 101.325 pascals, but the "standard" temperature is varies between definitions: 68°F, 60°F, 0°C, 15°C, 20°C or 25°C.
Pressure Pressure is the ratio of force to the area over which that force is distributed.
Pa Pascal - standard international (SI) unit of pressure equal to one Newton per square metre.  Can be followed by (a) = absolute pressure, or (g) = gauge pressure (pressure relative to atmosphere).
1 Pa = 10-3 kPa = 10-5 bar = 9.869210−6 atmospheres (atm) = 1.45037710−4 psi
kPa 1 Kilopascal = 1,000 Pa.  Note, in most calculations pressure is expressed in absolute terms i.e. kPa + 101.325.
WC (water column)
WG (water gauge)
Unit of pressure, usually related to mm or inches.  In calculations WC + 760mm for metric or WC in inches Hg + 29.92 for imperial.
Temperature Degrees Celsius.  Note, in most calculations temperature is expressed in absolute terms (Kelvin), i.e. °K = °C + 273.15
°C Degrees Celsius.  Note, in most calculations temperature is expressed in absolute terms (Kelvin), i.e. °K = °C + 273.15
Density The ratio of the mass of a specimen of a substance to the volume of the specimen.
kg/m3 The standard measure of density.  Also expressed as g/L and lb/ft3
Dust Concentration The weight of dust contained in a unit of gas.  The temperature and pressure of the gas must be specified, examples below.
g/Nm3 (mg/Nm3) Weight of dust in a cubic metre of gas at "N" conditions.
mg/Nm3 (dry) Weight of dust in a cubic metre of gas at "N" conditions expressed as a dry condition.  Commonly used by EPA for outlet emission values.
particulate Dust particles.
fume Very fine particulate.
collection efficiency The weight of dust collected per unit time divided by the weight of dust entering the dust collector during the same unit time expressed in percentage.
hygroscopic particulate Particulate that readily absorbs moisture.
incandescent particulate Particulate that is still alight or readily flames upon contact with oxygen, e.g. fly ash from wood fired boilers.
 


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