Glossary of Filtration Terms
Glossary of Filtration Terms
DEFINITIONS
This section presents definitions for some key words and
phrases that are generally associated with filtration
processes.
Absolute Rating: Particle size in micrometers removed at a given efficiency
under a manufacturer’s defined test condition. Also an
arbitrary term assigned by a manufacturer. Implied is
100%, but more often defined as 98.67%, 99%, 99.9% and
99.99%, according to the manufacturer. Parker Process
Filtration Division defines absolute as 99.98% removal
(Beta = 5000) as determined by particle counting methods.
Absorb/Absorption: The process of a fluid being taken into the pores of a solid.
Adsorb/Adsorption:
To collect and hold a fluid on the surface of a solid.
ASTM Test Procedure (F795-88): Procedure upon which Parker tests and rates its filter
media; generally a single pass test in water at 2.5 gpm per
10-in length.
Beta Ratio: The ratio of the number of particles of a given size and
larger upstream of a filter to the number of particles of the
same size and larger downstream.
Beta Ratio and Efficiency Relationship
| Beta Ratio % Efficiency | |
| 1 | 0 |
| 2 | 50 |
| 4 | 75 |
| 5 | 80 |
| 10 | 90 |
| 20 | 95 |
| 50 | 98 |
| 75 | 98.67 |
| 100 | 99 |
| 1,000 | 99.9 |
| 5,000 | 99.98 |
| 10,000 | 99.99 |
| oo | 100 |
Bridging: Condition of filter loading where contaminants span the
open space between adjacent sections of a filter medium,
thus blocking a portion of the useful filtration area.
Bubble Point: Pressure drop in inches of water required to expel the first
steady (continuous) stream of bubbles (fizz point) from a
horizontal disc of wetted filter medium or a filter cartridge
immersed in a liquid (usually alcohol). Parker Process
Filtration Division uses alcohol in its test.
Bubble Point Test: A common, nondestructive method used to test the
integrity of cartridge construction to compare relative
porosities of filter media or to monitor product consistency
as a quality control method.
Bypass: Fluid flowing through a passage other than the filter
medium and/or leakage around filter media seals.
“C” Style Bag: Parker Process Filtration Division style bag which incorporates
a spring band bag seal configuration. Designed to fit
Parker Process Filtration Division style housings only.
Cartridge/Bag Design Flow Rate: Flow rate at which cartridge/bag published performance
was generated in laboratory tests. Flow rates above those
listed below will adversely affect the efficiency and dirtholding
capacity of cartridge or bag.
| Cartridge/Bag Design Flow | ||
| Wound | 3.5 gpm/10 in long | |
| Pleated | 2.5 gpm/10 in long | |
| ProBond™ | 3.5 gpm/10 in long | |
| Mega Bond | Plus 2.5 gpm/10 in long | |
| Standard Bag | 80 gpm/single length | |
| XLH Bag | 8 gpm/double length | |
Channeling: Tendency for contaminant to pass through a low-density
area of an inconsistent filter medium or around cartridge
seal points.
Clarification: Filtration of liquids containing small quantities of solids.
Classification: Arrangement or separation of particles by size.
Collapse Pressure: Pressure across a filter cartridge or bag great enough to
cause it to collapse.
Colloids: Suspension of submicron
particles in a continuous fluid medium that will not settle out
of the medium.
Contaminant: Undesirable insoluble
solid or gelatinous particles present in a fluid.
Cycle Length/Filter Life: The
duration, measured in time or volume, that a filter can operate
effectively between replacement and/or cleaning.
Density:
Mass per unit volume of a substance under specified
conditions of temperature and pressure.
Depth Media: Generally filter
media that are thick and provide graded density construction.
Wound, resin-bonded and melt blown cartridges fall into this
category. Typically, these cartridges result in lower flow rates,
higher initial pressure drops and lower dirt holding capacities
than surface media (pleated).
Differential Pressure/Pressure Drop: Difference
in pressure between two points in a system. In filters, this
is usually measured between the inlet and outlet of the filter
housing (is a determining factor of filter service life).
Dirt Holding Capacity: The weight
of a contaminant fed to the filter during a test to reach a predefined
terminal pressure drop.
Double Open End (DOE): A filter cartridge configuration
such that both ends are open and require housings with knife
edge sealing devices.
Efficiency: The ability of the
filter medium to remove particles from the fluid stream.
Effluent/Filtrate: The fluid that has
passed through the filter.
Emulsion: A suspension of small
liquid droplets within a second liquid that will not mix.
Extractables: Inorganic or organic
elements or compounds in the filter medium that have leached
into the filtrate. Usually reported by weight or percent.
FDA: To be used for filtration
of foods, beverages, drugs or cosmetics. All filter construction
materials must comply with regulations established by the Food
and Drug Administration (FDA) as listed in CFR Title 21.
Filter Media: Plural of filter medium.
Filter Medium: The permeable material used
for a filter that separates particles from a fluid passing
through it.
Filtration: Separation of particulate matter
from a fluid by passing the fluid through a permeable medium
that will trap a percentage of the particulates.
Filtration Efficiency: That fraction of suspended
particles retained by the filter.
Flux: A relationship of flow to surface area;
expressed as gallons per minute per square foot.
“G” Style Bag: Filter bag provided by Parker Process Filtration Division to
fit
many competitive vessels (FSI, AF&F, GAF, ISP, etc.),
which is referred to as a snap ring seal configuration
Gauge Pressure: Pressure greater than atmospheric pressure.
Gels: Compressible or semisolid materials that can pass through
filter media at an undefined and inconsistent degree. Best
removed by depth medium.
Graded Density: Variation in a cartridge that results in the filter medium
being more dense toward the core and less dense toward
the outside surface. This is useful where a wide range of
particle sizes exists because it allows larger particles to
be trapped toward the surface and smaller particles toward
the core.
Gravimetric Efficiency: Amount of contaminant removed by weight as determined
by suspended solids analysis (ppm, mg/l).
Hydrophilic: The tendency of a surface to wet with water (water loving).
Hydrophobic: The tendency of a surface not to wet with water (water
hating).
Immiscible: Incapable of blending or mixing into a single homogeneous
phase.
Impingement: Direct impact of particle or liquid upon the filter media.
Influent: Fluid entering the inlet of a filter.
Laminar Flow: Flow rate at which liquid is in a nonturbulent state (10 ft/
sec) and should not be exceeded to maintain filtration
integrity and consistency.
Mean Filtration Rating: Average size of the pores of the filter medium.
Media (Medium): Material in a filter element that separates solids from fluid.
Media Migration: Contamination of the effluent by fibers or other material of
which the filter is constructed.
Micron: A unit of length. Correct term is micrometer (μm), which
is .000039 inch. Human eye can see a 40-micrometer
diameter particle.
Multipass Process: A process or system in which fluid is circulated indefinitely
through a filter medium, e.g., engines, compressors,
hydraulic equipment.
Nominal Rating: Micron size removed at a given efficiency under a
manufacturer’s defined test condition. An arbitrary term
assigned by a manufacturer. Varies from 50%-98%
depending on manufacturer and product.
Particle Removal Efficiency: Removal of particles as a function of size as determined by
counting individual particles.
Permeability: The property of a filter medium that permits a fluid to pass
through under a pressure differential (such as gpm/psi).
Porosity: A measure of the open area of a filter medium. Sometimes
expressed as a void volume.
Single Open End (SOE): A filter cartridge configuration such that one end is sealed
off by a closed end cap and the opposite end has a 222 Oring,
226 O-ring or other seal device. Used in housings that
are designed to accept 222 O-ring, 226 O-ring or other
SOE cartridges.
Single Pass Process: A process in which a fluid passes through the filter medium
only once before further processing. Parker Process
Filtration products are tested and rated for these types of
processes.
Specific Gravity: Ratio of mass of a solid or liquid to the mass of an equal
volume of distilled water, or of a gas to an equal volume of
air under prescribed temperature and pressure.
Surface Media: Filter media that are thin, cellulosic, microfiber or membrane
material and, due to their construction, generally
provide high flow rate, low pressure drop, high efficiency,
high surface area and high dirt-holding capacity.
Suspended Solids: Mixture of solids suspended in a fluid. Expressed in weight
or volume.
Thixotropic Flow: A fluid system where a range of viscosities can be measured
at any given shear rate. The longer the material is
sheared, the lower the viscosity until a lower limiting value
is reached.
Throughput: Total volume of a fluid that passes through a filter before it
must be replaced.
Turbidity: Measure of the amount of haze or cloudiness caused by
fine particles in a fluid.
Turbidimetric Efficiency: Percentage reduction of haze or cloudiness in a fluid.
Turbulent Flow: Flow rate at which laminar flow (10 ft/sec) is exceeded and
filtration performance is adversely affected.
Uniform Density: Having the same weight per unit volume of filter media from
the upstream (influent) to the downstream (effluent) side of
the filter.
Unloading: Tendency for previously collected contaminant to be forced
through the filter medium as pressure is increased.
Vessel: Container for filter cartridges or bags.
Viscosity: A measure of the resistance to flow of a liquid. Viscosity of
a liquid varies appreciably with changes in temperature.
Typically expressed in centipoise, centistoke or SSU
values.
Water Hammer: Pressure surge
produced when the linear flow of a noncompressible fluid is
rapidly interrupted by devices
such as fast-acting valves.
Glossary
of Filtration Terminology - PDF Download