Glossary of Filtration Terms
Migration of foreign material which enters the ﬂuid stream from system
components that wear from close tolerances, vibration, or shock.
ABSOLUTE – An
arbitrary term used to describe or deﬁne a degree of ﬁltration. The ﬁltration
industry uses various methods of determining absolute ratings that are not
necessarily interchangeable. Generally, absolute references 100% removal of
solids above a speciﬁed micron rating on a single pass basis. See nominal.
ABSOLUTE FILTER –
In liquid ﬁltration, absolute is frequently used to imply the size above which
no particles will be found in the ﬁltrate, e.g., a one-micron absolute ﬁlter.
ABSOLUTE RATING –
The diameter of the largest hard spherical particle that will pass through a
ﬁlter under speciﬁed test conditions. This is an indication of the largest
opening in the ﬁlter element.
ABSORB – To
intercept, or drink in. To suck in, as a sponge sucks in water.
ABSORPTION – A
physio-chemical process in which a substance associates with another to form a
homogeneous mixture presenting the characteristics of a solution.
Acetic acid bacteria characterized by the ability to turn ethanol into acetic
acid in the presence of oxygen. This is the most prevalent microbial
contaminate found in fuel. Thought to be a major contributor of microbial
ACID – A large
class of compounds which contain the element hydrogen (H+) in its formula which
may be replaced by metallic salts. Of primary concern is the deleterious effect
most acids may have on ﬁlter medium and housings.
ACIDITY – The
quality, state or degree of being acid. In lubricating oils, acidity denotes
the presence of constituents whose concentration is usually deﬁned in terms of
a neutralization number. The constituents vary in nature and may or may not
markedly inﬂuence the behavior of the ﬂuid.
– A highly porous and granular form of aluminum oxide having preferential
adsorptive capacity for moisture from gases, vapors, and some liquids. May be
regenerated for extended use under speciﬁed conditions.
ACTIVATED CLAY –
An adsorbent clay that removes color, odor, tree fatty acids and surfactants,
etc. from oils and hydrocarbons, e.g., Fuller’s Clay.
ADDITIVE – A
material, usually chemical, added to a product to impart new or unusual
characteristics or to improve existing characteristics.
Intermolecular forces which hold matter together. Also applied to the sticking
together of a particle to a surface, a ﬁber or another particle. The main
factors affecting adhesion of particles are 1) London-van der Waals forces
which are electrical in origin, 2) electrostatic forces and 3) surface tension
due to ﬁlms of moisture on particles or on the surface. Other factors
inﬂuencing adhesion are the nature of the surfaces, surface contaminants,
particle size, shape and roughness and time of contact.
ADHESIVES – Used
in the essential bonding process between cylinders of pleated ﬁlter paper and
end caps in paper ﬁlter element production. Types used include air drying
synthetic rubber/solvent/resin mixtures, two part epoxide and/or polyurethanes
and heat curing adherent plastisols.
ADSORB – The
physio-chemical phenomenon involved to attract and hold a gas, vapor, or liquid
on the surface of a solid, particularly on a ﬁnely divided material.
ADSORBATE – The
material which is adsorbed; i.e., the gas, vapor, or liquid which adheres, or
is chemically attracted to, the surface of the solid.
ADSORBENT – The
material which adsorbs; i.e., the solid which attracts and holds on its surface
the gas, vapor or liquid. Also materials added to liquors to decolorize or
purify by adsorbing the color or impurity. Fuller’s earth, activated carbon,
activated alumina, etc., are all adsorbents.
ADSORPTION – The
natural phenomenon of a gas, vapor, or liquid being attracted to, and held on,
the surface of a solid. To some extent, adsorption takes place on any solid
surface, but certain materials have sufﬁcient adsorbent capacity because of the
ﬁnely divided material to make them useful in such industrial applications as
the puriﬁcation and separation of gases and liquids.
Requiring oxygen to live and grow.
AEROSOL – A
liquid or solid particle suspended in air, gas, or vapor.
AFFLUENT – Fluid
entering the ﬁlter or ﬁlter separator. More commonly described as inﬂuent.
Opposite of efﬂuent.
AGGREGATE – Fluid
mixture of concentrated solids to be ﬁltered.
AIR ELIMINATOR –
Float-operated valve to evacuate air or gas from a housing or chamber.
ALKALI – A term
that applies to the type of compounds which have basic properties and which
will neutralize acids. Some alkaline materials are hydroxides, carbonates,
ALKYLATION – A
petroleum reﬁning process.
AMBIENT – Surrounding.
Example: ambient operating temperature of a housing is temperature essentially
the same as that surrounding the housing.
ANAEROBIC – Not
requiring oxygen to live and grow.
ANHYDROUS – Free
API – American
API GRAVITY – An
arbitrary scale expressing the gravity or density of liquid petroleum products.
The relation between API scale and speciﬁc gravity of petroleum oil is
expressed by the formula:
API = 141.5/Specific Gravity – 131.5
AREA – The available
apparent surface exposed to the ﬂow of a ﬂuid for maximum utilization. Function
of area in ﬁltration is related to initial pressure drop, rate of ﬂow, and
solids retention capacity. In many applications, proper utilization of area of
medium produces greater efﬁciency and solids retention. This is accomplished by
pleating of material into an accordion form to produce increased surface area
much greater than in a cylindrical form.
– Compounds related to six-carbon membered rings as benzene or its derivatives.
Asphalt like particles found in crude oil than form in refined fuel as a result
ASME – American
Society of Mechanical Engineers. Published code which governs the design of
ASSEMBLY – A
general term to describe the combination of a number of items used to make up a
whole. Example: a cartridge mounting assembly for a ﬁlter would include the
cartridges and all items needed to install the assembly in the ﬁlter housing.
Final assembly would be used to name the action of assembling all items into an
(ASTM) – American Section of the International Association for Testing
– The pressure of approximately 14.7 pounds per square inch exerted at sea
level in all directions by the atmosphere.
ATTAPULGUS – A
vein of mineral clay mined primarily in Georgia and Florida; the active
ingredient in most fuller’s earth. Activated by speciﬁc thermal treatment and
ground to ﬁne particle size.
ATTRITION – Wear
caused by rubbing or friction. Produces ﬁne particles that usually contaminate
liquids which surround the point of attrition. Sometimes referred to as
scouring or scoring.
AV GAS – Abbreviation
for aviation gasoline used for piston engines.
BACK PRESSURE – In
an air ﬂow, the resistance at any point of the remainder of the downstream
circuit or of any nominated sections of the circuit. In liquid ﬁltration the
back pressure can be due to a hydrostatic head, e.g., pumping from a ﬁlter to a
tank at a higher level.
BACON BOMB – A
fuel sampler used for taking samples at different levels in a tank.
BAFFLE – A plate
to protect ﬁlter elements from the velocity of ﬂow into a housing.
BAG FILTER – A
fabric filter designed to remove particulate from a liquid. They come in
various sizes and are usually non-rigid, disposable and easily
replaceable. Bag filters are used
predominately as pre-filtration.
BASKET – Element
for a basket strainer. A device normally using a screen as its medium for
removal of coarse bulk solids.
BASKET STRAINER –
Housing for the removal of coarse bulk solids from liquid, air, or gas; element
is a basket covered with a screen of a given mesh.
BETA (ß) – is
calculated by dividing the number of particles entering the ﬁlter by number of
particles exiting the ﬁlter. ß10 represents the ﬁltration ratio at 10
micrometers of the ratio of the upstream to downstream particles larger than 10
BETA EQUALS 75 –
Multi-pass testing has shown that this is beta ratio which corresponds to hard
spherical particle deﬁnition of the absolute ﬁlter rating.
BETA FACTORS – A
system for measuring ﬁlters effectiveness by particle size.
BIOCIDE – A
chemical substance that destroys or inhibits the growth of living organisms.
Biocides are used to control microbial growth in fuel. Dixon sells and
recommends Biobor JF to eliminate microbes in fuel systems.
vegetable or animal fat based diesel fuel generally consisting of alkyl esters.
See also FAME.
BLIND SPOTS –
Places in medium where no ﬁltering occurs. Also referred to as dead areas.
Opposite of effective area.
BLINDING – Where
ﬁltered-out particles ﬁll the openings in the medium to the extent of shutting
off the ﬂow of product; the loading up of the medium so as to reduce capacity.
Also referred to as blocking or plugging.
BUNA-N – Gasket
material. A synthetic rubber frequently used for housing closures, ﬂanges, and
BURST PRESSURE –
The maximum pressure a housing will safely withstand.
– Force required to burst a housing. Example: burst pressure may be 100 psi,
while bursting strength may be 175 psi.
Condition resulting from the product ﬂowing through a housing without ﬂowing
through the medium. Also a ﬁltering system which ﬁlters only part of the
stream, on a continuous basis. Opposite of full ﬂow.
– Indicator which signals alternate ﬂow.
BYPASS VALVE –
Valve to pass the ﬂow around the media or the housing, usually activated at a
given differential pressure setting.
CAKE – Solids
deposited on the ﬁlter medium during ﬁltration in sufﬁcient thickness to be
removed in sheets or sizable pieces. In many cases, cake may provide its own
ﬁlter medium by adding to the surface of medium. Also referred to as discharged
solids or residue.
CAP, ELEMENT –
Component which covers one end of an element and holds the element in place in
the housing. Sometimes called a yoke.
CAP, END – The
end of many types of ﬁlter cartridges. In particular, the shallow annular dish
into which the ends of a pleated paper ﬁlter cylinder are adhesively bonded to
form a pleated paper cartridge.
CAPACITY – Volume
of product which a housing will accommodate expressed in gallons or similar
units. Also amount which will ﬁlter at a given efﬁciency and ﬂow rate,
expressed in gallons per minute or similar units.
Medium used in a housing to perform the function of coalescing, ﬁltering, or
separating. Also referred to as element, media, repack, etc. Made in a speciﬁed
physical shape, to be mounted by use of hardware designed for that purpose.
CATALYST – A
substance which accelerates a chemical reaction without itself taking part in
the reaction. Example: alkylation will not take place unless some substance
such as sulfuric acid is present; such a substance is called a catalyst.
CAUSTIC – A class
or a name given to a group of chemicals, usually caustic soda or sodium
hydroxide. A substance which has the power to burn, corrode, or eat away. Used
in chemical manufacture, petroleum reﬁning, pulp and paper, detergents, soap,
textiles and vegetable oil reﬁning.
CELLULOSE – The
preponderant and essential constituent of all vegetable tissues and ﬁbers.
Basic in the textile and paper making industries. Three types exist in
alpha-cellulose, beta-cellulose and gamma-cellulose. Material used in ﬁlter
medium is bound by impregnation, usually a phenolic resin. Process of
manufacture controls the basic weight and pore size to speciﬁcation. Filter
paper, when impregnated with other properties, produces an excellent
hydrophobic membrane which is non-water wetting and is used in the second stage
of two stage ﬁltration separation equipment. Ideal cellulose material provides
for a variety of ﬁltration efﬁciencies, low initial pressure drop, high wet
strength and solids retention.
CENTER CORE –
Material formed into a tube or cylinder for structural purposes to permit a
cartridge to retain its original physical form. May also be the basic medium,
formed with sufﬁcient strength so as to serve the purpose of a center tube.
Example: a tube of glass ﬁbers may be formed and cured to such a degree that a
center core is not required. Sometimes referred to as a center tube.
CENTER PIPE –
Component of a housing which is used as a mount for cartridges. Made with
perforated effect to accommodate ﬂow. A center rod is used for the same purpose
but is not perforated and does not accommodate ﬂow.
CENTER ROD –
Component of a housing used for mounting cartridges in the housing. Usually
made of a round bar material. A center pipe may also be used for the same
purpose but is made with perforated effect and directs ﬂow through the
CENTER SEAL –
Part which forms seal between two elements when one element is one the top of
another element. May also be called an adaptor.
CENTER TUBE –
Component of an element or cartridge which supports the medium at the center of
CENTISTOKE – One
one-hundredth of a stoke. A stoke is equal to the viscosity in poises times the
density of the ﬂuid in grams per cubic centimeter.
CETANE – A
colorless liquid hydrocarbon of the alkane series used as a solvent.
CETANE NUMBER –
an indicator of combustion in a diesel engine.
Similar to octane rating in gasoline.
Filtration of liquids containing small quantities of suspended solids;
ﬁltration takes out most of these solids and increases the clarity of the
CLARITY – Amount
of contaminates left in a ﬁltered liquid; the absence generally indicates the
liquids to be free of contamination to an unspeciﬁed degree.
CLAY – Medium
used in some elements; usually a blend of attapulgas and montmorillonite clays.
CLEAN PRESSURE DROP
– Differential pressure (drop) across a housing, measured in pounds per square
inch at rated ﬂow on new elements with clean product.
CO – Carbon
COAGULANT – That
which produces coagulation or agglomeration of suspended solids.
Growing together of minute particles to form larger ones, which are called ﬂocs
and are easier to ﬁlter. Also referred to as ﬂocculation.
COALESCE – To
consolidate or join up together.
Mechanical device which unites discrete droplets of one phase prior to being
separated from a second phase. Can be accomplished only when both phases are
immiscible. Requires a tight medium which is preferentially wettable and, by
its nature of being tight, is also a good ﬁltering material. Good coalescing permits
gravity separation of the discontinuous phase. Coalescing may be accomplished
by only a coalescer cartridge when the speciﬁc gravities of the two phases are
widely separated. As the gravities’ difference becomes less, the two stage
principle is generally required where ﬁnely coalesced discontinuous droplets
are repelled by the second stage separator cartridges.
Action of uniting of small droplets of one liquid preparatory to its being
separated from another liquid.
COLLOID – Very
small, insoluble non-diffusible solid or liquid particles that remain in
suspension in a surrounding liquid. Solids usually on the order of 0.2 µ or
– Gelatinous substance of minute particles which remain in suspension.
COLOR BODIES –
Form of deposit which may appear as producing colors. Term frequently used in
the petroleum industry is hydrocarbon color bodies.
Capability of two or more materials or substances to be used together without
ill effect. Must be considered when choosing the medium to be used with any
COMPOSITE MEDIA –
Media made up of more than one material.
Degree of physical change in ﬁlter cake particles when subjected to normal
pressures. Also a factor when selecting gasket material.
CONDENSATION – Process
of cooling a vapor below its boiling point in order for it to be liqueﬁed.
Component parts of something.
CONTACT TIME –
The length of time an absorbent is in contact with a liquid prior to being
removed by the ﬁlter.
Foreign matter in a ﬂuid which is accumulated from various sources such as
system dirt, residue from wear of moving parts, atmospheric solids which settle
in an open system. Contaminates tend to discolor a liquid, cause additional
wear on moving parts, cause system upsets in process streams, or reduce the
efﬁciency of a ﬂuid. Water, as well a solid, may be considered a contaminate
when the presence of water causes adverse results. The presence of
contaminates, whether liquid or solid, is the basis on which the use of ﬁlters
or ﬁlter separators are sought.
– A device designed to measure particle contamination in-line or out of a
sample jar. The monitor measures contamination using ISO code. See ISO.
– Basic product ﬂowing through a ﬁlter or ﬁlter separator which continues on
through a system after being subjected to solids and/or other liquid
Change of type of elements in a housing to vary the efﬁciency. May also refer
to the adaptor hardware to provide for use of elements in competitive
equipment, sometimes called retroﬁt. In general, refers to the changing of one
type of medium to another type for a speciﬁc purpose.
CONVERSION KIT –
Materials required to convert a housing to the use of another type of element
or to perform a different function. Example: convert bag ﬁlter to a canister
filter housing. May also be referred to as an adapter kit.
Used to describe one pleat of a pleated surface type element, usually in the
shape of a V. Also refers to the twisting or coiling of a cotton material as
well as the irregular spiral or screw like condition of mature cotton.
Twistings or coilings used to describe one complete pleat of an element.
CORE – Material
used for the center of an element, generally of the wound design. May also be
called a center tube when used in the coalescer, separator, or other type ﬁlter
element. May also be a tube of ﬁbers formed into an element which has sufﬁcient
strength to provide its own center core.
Conversion of metals into oxides, hydrated oxides, carbonates, or other
compounds due to the action of air or water, or both. Salts and Sulphur are
also important sources of corrosion. Removal of solids and water reduces the
effect or speed of corrosion in many cases; and in other cases, corrosion
inhibitors are used to reduce the effect or corrosion.
Fine ribbing sometimes applied to ﬁlter paper following resin impregnation and
before pleating to form a pleated paper ﬁlter element. Corrugations which run
at right angles to the main pleats help to hold the pleats apart against the
action of differential pressure encountered in use. Discontinuous corrugation
or dimples are sometimes alternately employed.
PRESSURE – Pressure above which ﬁltration or separation equipment may
produce reduced efﬁciency or fail to function properly.
Wearing down, or reduction in the efﬁciency of medium.
DEGREE OF FILTRATION
– Level of cleanliness of a ﬂuid, usually measured in milligrams in a given
volume such as quart, liter, gallon, etc.
Removal of water or hydrocarbon in vapor form from an air or gas; also water
from another immiscible liquid. Differs from entrainment removal in that the
dew point of a gas stream will be lowered by vapor removal. A form of
DELTA or ΔP – A
commonly used symbol denoting the pressure drop across a ﬁlter.
Compactness or thickness; ratio of weight of medium to the weight of an equal
volume of ﬁber. In general, mass per unit volume, usually expressed in grams
per cubic centimeter or pounds per cubic foot, or gallons.
DEPTH FILTER MEDIUM
– Filter medium which primarily retains contaminant within tortuous passages,
e.g., ﬁbrous or granular. Retention efﬁciency is achieved by means of a series
of low efﬁciency particle captures.
DEPTH TYPE FILTRATION
– Filtration accomplished by ﬂowing a ﬂuid through a mass ﬁlter medium
providing a tortuous path with many entrapments to stop contaminates. Flow may
be cross ﬂow such as from the outside to inside and then down the center of an
element, or from end to end. Certain types of solids, or combinations of
solids, do not lend to surface ﬁltration where depth type ﬁltration is found to
be more suitable.
DESICCANT – Drying
agent or medium used in dehydration of air, gas, or liquids. Examples: silica
gel, activated alumina, molecular sieve, etc.
DIAPHRAGM – As
used on valves, a diaphragm is a ﬂexible material which permits the movement of
internal parts without the loss or redistribution of pressure in the chamber.
DIESEL FUEL –
Petroleum product used as fuel for diesel engines.
(ΔP) – Difference in pressure
between two given points of a ﬁlter, ﬁlter separator, etc.
INDICATOR – Indicator which signals the difference in pressure at two
SWITCH – Electrical switch operated by the difference between two pressures
and often used to give warning of the end of a ﬁltration cycle.
– Differential pressure speciﬁed as the maximum an element will withstand
without structural failure.
DIFFUSION – In
cake washing, removing the original liquor around the individual particles by
mixing with the wash liquor.
INTERCEPTION – while filtering, the smallest particles collide frequently
with liquid molecules, moving in a random manner until they collide with the
fiber and are collected.
DIFFERENTIAL PRESSURE GAUGE – Type of pressure gauge which automatically
shows the differential pressure reading between two points.
DIRECTION OF FLOW
– Direction in which product ﬂows through element; may be from inside to
outside, from outside to inside, or end to end, depending on the design of the element.
– When midsized particles are too large to pass through the fibers of a filter
and become logged in the media. This
happens most commonly in fuel filtration.
DIRT HOLDING CAPACITY
– Volume of contaminate an element can hold before reaching the maximum
allowable pressure drop. Volume will vary depending on the size and design of
the element and the density of the solid particles. Usually reported by weight
such as grams or pounds per element. Also called solids retention or solids
DISCHARGE – Liquid
that leaves the housing after passing through the medium.
DISCHARGE VALVE –
Valve to allow the efﬂuent stream to ﬂow out of the housing; may be closed by
the operation of a pilot valve, in which case product would not leave the
– Separated phase or product from the continuous phase. Example: water may be
the discontinuous phase when separated from a hydrocarbon, air or gas.
Describes element which is to be discarded after use and replaced with an
identical element. Same as replaceable. Opposite of reusable.
– Any solid material that will dissolve in the liquid that is being ﬁltered.
Condensed product of distillation, as certain petroleum products.
Process of vaporizing a liquid and collecting the vapor, which is then usually
condensed to a liquid. In industry, this process is widely used to separate the
components in a liquid solution. Since every pure compound boils at a speciﬁc
temperature, it is often possible to boil off one liquid while most of the
higher boiling point material remains in its liquid state. It is extremely
difﬁcult and sometimes impossible to separate materials in this way when they
boil at the same, or near the same, temperature.
DIVIDER – Component
of a housing: metal plate used to create chambers such as inlet and outlet
Portion of the product stream which has already passed through the system;
portion of a system located after a ﬁlter, ﬁlter separator, etc.
DRAIN VALVE –
Valve for draining off material which has been separated from a ﬂuid stream.
Also a diaphragm type valve that operates as part of a system to evacuate a
discontinuous phase automatically.
DROPLET – Minute
drop which mates to form larger drops capable of falling by gravity.
DUAL GRAVITY VALVE
– Float operated valve which operates on the interface of two immiscible
liquids of different speciﬁc gravities and which operates to release one of the
DUPLEX FILTER –
Assembly of two ﬁlters with valving for selection of either or both ﬁlters.
E10 – gasoline
enriched with 10% ethanol.
Degree to which element will perform in removing solids and/ or liquids.
– Graph showing the performance of a ﬁlter when challenged by speciﬁed
artiﬁcial or natural contaminants under controlled conditions. Penetration or
efﬁciency may be plotted against particle size at constant face velocity.
EFFLUENT – Stream
of ﬂuid at the outlet of a ﬁlter or ﬁlter separator. Opposite of afﬂuent or
ELEMENT – Medium
used in a housing to perform the function of coalescing, ﬁltering or
separating. Also referred to as cartridge, repack, etc.
ELEMENT CAP –
Component which covers one end of an element and holds the element in place in
the housing. Sometimes called a yoke.
Dispersion of one substance in the form of minute drops within another
Dispersion of ﬁne liquid particles in a liquid stream which do not necessarily
dissolve in each other but are held in suspension. Many emulsions may be broken
by coalescing if the liquids are immiscible. Emulsion stabilizers modify the
surface tension of the droplets which makes coalescing difﬁcult, if not
– Chemical methods of emulsion separation are regularly employed to remove the
oil phase from spent emulsion cutting oils, prior to disposal. Typical
treatment is by dosing with a solute of a divalent or trivalent metal. Thermal,
electrical and physical methods are also used. See coalescence.
Process in which a material is coated or covered with a plastic ﬁlm or sheath.
END CAPS – Components
adhered to ends of an element with adhesive or by other means to contain medium
in the form designed for the element.
END SEAL – Bond
between the end cap and the ﬁlter medium. In cartridges of pleated paper
construction this is frequently an epoxide, polyurethane or nitrile-phenolic
adhesive. Also refers to the sealing device which seals the end cap of a cartridge
to its housing.
ENTRAINED WATER –
Discrete water droplets carried by a continuous liquid or gas phase when water
is immiscible with the liquid. May be separated from the continuous phase by
coalescing and gravity separation. Usually picked up in a system by
condensation or a water washing used in process.
Mist, fog, or droplets of a liquid which is usually considered a contaminant
when used in the ﬁltration industry.
ANAEROBES – Microbes that can live in both oxygen and non-oxygen
FAME – Fatty acid
methyl ester are derived from the fats of methanol. The molecules within
biodiesel are predominately FAME and usually made from vegetable oils.
FEEDSTOCK – a raw
material used as a fuel or converted to another fuel.
FELT – Fabric
built up of the interlocking of ﬁbers by a combination of mechanical work,
chemical action, moisture and heat. Frequently used as ﬁlter medium, some types
of which have been adapted to high temperature applications for air or gas. Bag
filters are often made of felt.
Fundamental unit comprising a textile raw material such as cotton, wool, etc.
FIBER MIGRATION –
Carry-over of ﬁbers from the media used in coalescer, separator, or ﬁlter
cartridges into the efﬂuent. More deﬁnitive than media migration since ﬁber
migration is qualitative.
Trade name for a variety of products made of, or with, glass ﬁbers. Term used
to describe a variety of products made of, or with, glass ﬁbers, See glass
FILTER – Term
generally applied to a device used to remove solid contaminate from a liquid or
gas. A ﬁlter, as referred to in the industry today, is limited to a device
which removes solid contaminates only. If a device is used to remove solid and
liquid contaminates, it is referred to in general terms as a separator, ﬁlter
separator, or entrainment separator. The term ﬁlter is sometimes erroneously
used to describe the medium used inside the housing or ﬁlter case, but the
correct use should be ﬁlter element, cartridge, etc.
FILTER AID –
Substance of low speciﬁc gravity which remains in suspension when mixed with
the liquid to be ﬁltered. It should be porous and must be chemically inert to
the liquid being ﬁltered. Increases ﬁltering efﬁciency and maintains cake porosity.
– Single stage, horizontal housing for coalescing and separating one immiscible
ﬂuid from another and the removal of solids. Generally recommended for use
where continuous phase has a light gravity. Available with various efﬁciencies.
FILTER HOUSING –
filtration vessel that holds filter media, cartridge or bag.
FILTER MEDIUM –
The porous material mounted on a plate or frame which separates the solids from
the liquids in ﬁltering. Also referred to as ﬁlter cloth, ﬁlter plate or septum.
FILTER MONITOR –
Water absorbent ﬁlter element which will continuously remove dirt and water
from aviation fuel.
FILTER PAPER – A
permeable web of randomly oriented ﬁbers, generally cellulose (i.e., wood pulp,
cotton) or glass ﬁber is formed from water draining from a carefully prepared
suspension of these ﬁbers fed to a continuously traveling, endless belt of wire
mesh—a paper making machine. The preparation and type of ﬁber controls the
permeability within any one thickness and weight per unit area of grade.
Various grades are available with these variations and also with resin addition
to give strength to the paper when wet. A further variation arises with a crepe
ﬁnish whereby the effective area of paper for a given weight is considerably
increased. A wide range of ﬁlter papers is available commercially for the
removal of particles from liquids and gases.
FILTER PLATE –
The porous material mounted on a plate or frame which separates the solids from
the liquids in ﬁltering. Also referred to as ﬁlter cloth, ﬁlter medium or
– Housing which removes solids and entrained liquid from another liquid or gas.
Uses some combination of a bafﬂe and/or coalescer, ﬁlter, or separator element.
May be single-stage, two-stage, or single or two-stage with preﬁlter section
for gross solids removal. Common application is the removal of water from gas
or another immiscible liquid. General reference to term implies the equipment
is capable of both ﬁltration and separation to speciﬁc degrees of efﬁciencies.
FILTER SYSTEM –
The combination of a ﬁlter and associated hardware required for the ﬁltration
Ease or difﬁculty of ﬁltering.
FILTRATE – Liquid
which has passed through the ﬁlter; ﬂuid that has been separated from the
solids in the slurry being ﬁltered. Also referred to as discharge liquor,
efﬂuent, mother liquor, solute, or strong liquor.
FILTRATION – Process
of removing solid particles from liquid or gas by forcing them through a porous
PASS) – The process of passing liquid through a filter or system one time
for the purpose for cleaning and achieving a specific cleanliness standard.
(MULTI-PASS) – The process of passing liquid through a filter or system
multiple times for the purpose of cleaning and achieving a specific cleanliness
standard as an end result. Also known as kidney loop filtration.
FILTRATION BETA RATIO
– The ratio of number of particles greater than a given size (n) in the inﬂuent
ﬂuid to the number of particles greater than size (n) in efﬂuent ﬂuid.
FILTRATION RATE –
The volume of liquid that passes through a given area of ﬁlter in a speciﬁc
time. Usually expressed as gallons per square foot per minute (or hour).
– Operation wherein the liquid is vaporized immediately on entrance to the
FLASH POINT –
Lowest temperature at which a combustible liquid will give off a ﬂammable vapor
that will burn momentarily.
Growing together of minute particles to form larger ones, which are called ﬂocs
and are easier to ﬁlter. Also referred to as coagulation.
FLOW – Viscous
ﬂow (also known as streamline or laminar) is characterized by the viscosity of
the ﬂuid controlling the relationship between pressure and its velocity; with
turbulent ﬂow the relationship is controlled by inertial factors. For viscous
ﬂow in ducts Reynolds number is less than 2,000 and for turbulent ﬂow greater
than 4,000. See laminar flow.
FLOW RATE – Rate
at which product is passed through a housing or system; generally expressed as
gallons per minute, barrels per hour, barrels per day, actual or standard cubic
feet per minute, hour, day, etc. Same as rate of flow.
FLOW RESISTANCE –
Resistance offered by ﬁlter medium to ﬂuid ﬂow; the pressure difference
required to give unit ﬂow of a ﬂuid of unit viscosity through a unit cube of
ﬁlter medium. See also resistance ventilation filter.
FLUID – Term used
in ﬁltration and separation to include liquids, air or gas as a general term.
DISTILLATION – Separation of a liquid mixture into components differing in
boiling point using a fractional column
FREEZING POINT – For
a pure substance the freezing point or melting point is the temperature at
which the liquid and solid are in equilibrium with one another; i.e., at a
higher temperature the solid will melt and at a lower temperature the liquid
will solidify. Varies with the composition of the liquid.
FRICTION – Resistance
created by the surface of one object moving over the surface of another due to
the interlocking of minute projections from the surfaces; this is called solid
friction. If a lubricant is introduced between the two moving surfaces ﬂuid
friction replaces solid friction.
FULLER’S EARTH – Medium
used in some elements, usually a blend of attapulgus and montmorillonite clay.
A ﬁnely divided hydrous aluminum silicate. See attapulgus.
GASKET – Material
inserted between contact surfaces of a joint to ensure a ﬂuid-tight seal.
Although invariably softer than surfaces with which it is in contact it should
not form a permanent bond. Constructional material is dependent on the
temperature, pressure and chemical nature of the conﬁned ﬂuid.
GELATINOUS – Used
to describe suspended solids that are slimy and deformable, causing rapid ﬁlter
GLASS FIBER –
Proper reference to a ﬁbrous material made from glass that is commonly used as
a ﬁlter and separator medium. May be used in blanket or tube form and, due to
the random dispersal of the ﬁbers, makes good ﬁlter medium. Are hydrophilic
(water wettable) and perform the function of coalescing immiscible liquids for
separation. May be used effectively on compressed air, gas, or liquids which
are acidic but only slightly caustic. Also referred to as ﬁberglass or
GLYCOL – General
term for a family of alcohols; clear, colorless, and soluble to varying degrees
in water, alcohol, ether, benzene, etc. Has a wide range of usage such as
coolants, antifreeze and processes.
GPD – Gallons per
GPH – Gallons per
GPM – Gallons per
Relationship between the weight of a material and the weight of an equal volume
of water. In the United States this relationship is expressed in terms of API
gravity, Baumé gravity or speciﬁc gravity.
GRAVITY FILTER –
Filter in which the driving force for ﬁltration is provided solely by the head
of liquor above the ﬁlter medium (i.e., not employing pressure or vacuum to
give a high differential pressure). Gravity ﬁlters often handle compressible
materials or materials in the form of ﬂakes which would pack down and become
impervious under high differential pressure.
– Separation of immiscible phases resulting from a difference in speciﬁc
gravity by coalescing.
HAZE – An
opalescent or a very ﬁne suspension in a liquid.
HEAD GASKET –
Gasket seal at the main closure of a pressure housing. Usually the seal used
between two ﬂanges. Generally, either a ﬂat gasket or o-ring.
HEAD LIFT –
Device for raising head of a vertical pressure housing to permit access to
interior of housing.
– Refers to the amount of solids, particulate or foreign material one or more
elements is capable of retaining up to the terminal or maximum differential
pressure. Also can refer to volumetric holding capacity of either a solid or a
Uniformity of particle size and distribution of a solid in the product.
Hydrocarbon utilizing microorganisms – BUGS. Microbes that eat hydrocarbons,
usually produce an acidic byproduct associated with MIC.
HYDROCARBON – Any
one of a large number of compounds composed primarily of the elements carbon
and hydrogen. As they increase in molecular weight and boiling point, they may
be individually gases, liquids or solids.
(HDS) – Process of removing sulfur from refined petroleum products in order
to reduce SO2.
Water accepting or water wetting. Having an afﬁnity for water. Capable of
uniting with, or dissolving in, water. Effective coalescing requires medium to
have hydrophilic characteristics causing free or entrained water to commingle
into droplets which, when mated with other droplets, form into drops which
separate by gravity. Opposite of hydrophobic.
Non-water wetting. Having an antagonism for water. Not capable of uniting or
mixing with water. Hydrophobic features are induced in the process of cellulose
manufacture. Opposite of hydrophilic.
– Test conducted with either air, water or other ﬂuids at a given value over
design pressure, to prove the structural integrity of a pressure housing.
Water absorbing, e.g. ethanol is easily absorbed into water.
ID – Inside
IFT – Interfacial
IMMISCIBLE – incapable
of being mixed; insoluble; opposite of miscible.
IN SITU – In its
INERT – Inactive
chemically or physically.
INFLUENT – Stream
of ﬂuid at the inlet of a ﬁlter or ﬁlter separator. Same as afﬂuent. Opposite
Compounds or materials that have the effect of slowing down or stopping an
undesired chemical change such as corrosion, oxidation, or polymerization.
Addition of certain types of inhibitors change the interfacial tension of a
petroleum product, which may reduce the coalescing efﬁciency of some medium.
Reduced interfacial tension between two liquids causes a tighter emulsion more
difﬁcult to break up by coalescing.
INITIAL PRESSURE DROP
– Loss in differential pressure between two points upon the start of ﬂow
through a housing using new elements.
IN-LINE – Applied
to mixing and conditioning, in-line means the mixing of liquids with liquids or
solids with liquids, or suspensions of solids in liquids with liquids, within a
pipework system using metering units and automated control, which eliminates
the requirement for separate storage tanks and mixing compartments.
IN-LINE FILTER –
Filter or strainer arranged as a continuous ﬂow unit in a pipeline or similar
INORGANIC – Not
formed from living substance; substances which do not contain carbon as a major
INSIDE-OUT – Flow
of product from inside to outside of element.
Incapable of being dissolved in a ﬂuid; opposite of soluble.
INTAKE – Material
to be ﬁltered. Also referred to as concentrate, feed, inﬂuent, liquor, mud,
preﬁlt, pulp, slimes, or sludge.
One particular element which may be used in place of another particular
element. Dimensions of both must be equal. Element being substituted frequently
has more desirable characteristics than Element which it replaces. Refers
primarily to dimensional interchangeability and must be for the same general
Surface over which continuous phase and discontinuous phase are in contact.
– Measure of miscibility or solubility of the continuous and discontinuous
phases. Increases as miscibility or solubility decreases. See inhibitors for
effect on coalescing.
Pleating of two or more ﬁlter media into an element, such as glass ﬁbers and
Spaces or openings in a medium. Also referred to as pores or voids. Usually
refers to those voids contained in adsorptive media such as carbon, Fuller’s
Earth, etc. Available area for adsorption on or within a particle then must
take into account not only the surface area but also that area within the particle
due to the interstices or voids.
Pertaining to the openings in a medium.
– When filter media captures large particles flowing in a fluid stream and
impacts the media in a straight line, becoming entrapped while the fluid moves
around the fiber and flows through.
Electrically charged atom or group of atoms, formed by the gain or loss of
ION EXCHANGE –
Reversible chemical reaction, usually between a solid and a liquid, in which
ions may be interchanged.
I.P. – The
Institute of Petroleum.
International Standards Organization.
CODE – ISO code for measuring contamination. A standard of measurement used
JET FUEL – Petroleum
product used as fuel for jet engines.
KARL FISHER –
Analytical method of determining amount of water present in a sample by
Petroleum liquid used as fuel, or for heating purposes.
LACQUER – Natural
or synthetic resin which is dissolved in a suitable solvent such as hydrocarbon
oil rich in aromatics. When applied, the oil solvent evaporates, leaving behind
a lacquer ﬁlm.
LEL – Lower
LIFE EXPECTANCY –
Amount of use which may be expected from an element before it must be replaced;
will vary according to element’s characteristics, operating conditions, and
condition of inﬂuent.
LINE SIZE – Size
of line used to carry the product in a system, such as a two-inch line.
LIQUID – Product
stream in liquid ﬁltration and liquid ﬁltration separation. Also may be the
material to be removed by a liquid or gas entrainment separator.
LIQUID LEVEL CONTROL
– Generally a ﬂoat-operated control operating off the interface of two liquids
for the purpose of evacuating one of the liquids from the housing after
separation. In air or gas, it would operate off the surface of the liquid.
LIQUID LEVEL GAUGE
– Gauge by which the interface of two immiscible liquids can be viewed,
generally in an accumulator sump. May also be called a level gauge or interface
LIQUOR – Material
to be ﬁltered.
LITER – 1.057
quarts. Used as a volumetric standard to analyze liquids for water or solids
TENSION – Where the interfacial tension of one liquid over another liquid
would be less than 25 dynes/cm at 70°F. See inhibitor for effect on coalescing.
MAIN CLOSURE –
Closure through which the housing is serviced when there is more than one
opening into a housing.
MALE MOUNTING CAP
– Device which allows elements to be mounted through an opening in a tube
sheet. Normally removed with the cartridge. Used primarily in conversion kits.
MANIFOLD – A pipe
or assembly into which the ﬁlter elements are connected to form one common
discharge for the ﬁltered product. Also a piping system to connect two or more
housings in serial or parallel.
PRESSURE DROP – Maximum pressure differential of a housing under speciﬁed
product and ﬂow condition.
PRESSURE – Highest pressure differential which an element is required to
withstand without structural failure or collapse.
PRESSURE – Maximum pressure allowed in the system.
RATING – A measurement of the average efﬁciency of a ﬁlter medium using the
Multi-Pass Test where the average ﬁltration (BETA) ratio = 2.0.
MEDIA – The
material that performs the actual separation of solids from liquids. Sometimes
erroneously used to mean septum.
MEDIA MIGRATION –
Carry-over of ﬁbers from ﬁlter and/or separator elements, or other ﬁlter
material into the efﬂuent. Less deﬁnitive than ﬁber migration and is
Principal component of an element. Material of controlled pore size or mass
through which a product is passed to remove foreign particles held in
suspension or to repel droplets of coalesced water; or a material without
controlled pore size such as glass ﬁber mats which contribute to ﬁltration,
coalescence, or separation of two immiscible liquids.
MEMBRANE – Medium
through which the liquid streams are to be passed or exchanged. Normally
associated with ion exchange media such as dialysis, osmosis, diffusion, etc.,
although ﬁlter paper itself could be classed as a membrane.
MEMBRANE FILTER –
Thin permeable ﬁlm of inert polymeric material cast in such a way from a
mixture of solvents so that the size, number and shape (tortuosity) of the
pores is controlled. Widely used in bacterial ﬁltration—solution sterilizing—in
the medical ﬁeld. In multiple units they are used industrially in beverage
ﬁltration and preparation of very pure water, etc. Can be in cylindrical
cartridge form. Fine grades used in ultraﬁltration, reverse osmosis and
MESH (WIRE CLOTH)
– Number of openings, or fractions of openings, in a lineal inch of wire cloth.
Where the fractional part of an inch is speciﬁed, for example 1/2 mesh or 1/2”
mesh, the term is understood to mean the measurement from the center of one
wire to the center of the adjacent wire. Term should not be confused with clear
openings or space.
MIC – Microbial
Influenced Corrosion is corrosion caused by microorganisms and their microbial
MICROMETER – One
millionth part of a meter. A standard SI unit.
MICRON (µm) – Short unit of length in the
metric system. One millionth of a meter, 10-4 centimeter, 10-3 millimeter, or
0.000039 of one inch. Used as a criterion to evaluate the performance or
efﬁciency of ﬁlter medium or to describe the condition of either the inﬂuent or
efﬂuent. Usually stated in terms of being either absolute or nominal. Nominal
micron rating is generally taken to mean that 98% of all particles over a given
micron value have been removed by speciﬁc medium. Absolute micron rating is
generally taken to mean that all particles over a given micron value have been
removed. Naked eye can see a particle 40 microns or larger.
MICROORGANISMS – Living
bodies that can be seen only through a microscope.
Contaminant released downstream of a ﬁlter. Built-in dirt migration-migration
composed of foreign materials introduced during handling, storage and
manufacture; Contaminant migration—migration due to unloading. Media
migration—migration composed of the materials making up the ﬁlter media.
MILLILITER – One
thousandth of a liter, equal to approximately one cubic centimeter.
Capable of being dissolved, soluble. Opposite of immiscible.
MIST – Visible
water or hydrocarbon vapor; ﬂoating or failing in ﬁne drops.
– That which causes the coalescing, ﬁltering or separating action to take
MS – Military
Standard. Preﬁx to government-assigned numbers indicating standardized items to
NAPHTHENIC ACID –
Acid compounds commonly found in crude oil.
Arbitrary term used to describe or deﬁne a degree of ﬁltration. The ﬁltration
industry uses various methods of determining nominal ratings which are not
necessarily interchangeable. Generally nominal references 98% removal of solids
above a speciﬁed micron rating on a single pass basis. See absolute.
NOMINAL RATING –
An arbitrary micrometer value indicated by ﬁlter manufacturer. Due to lack of
reproducibility, this rating is deprecated.
NONWOVEN – A
ﬁlter cloth or paper that is formed of synthetic ﬁbers that are randomly
oriented in the media. Usually held together with a binder.
NPT – National
pipe thread standard.
OCCLUDED – Taken
in and retained, absorbed.
OCTANE – A
hydrocarbon or the alkane type. A component of gasoline.
OCTANE RATING – A
standard measurement of the performance of an engine.
OD – Outside
OMEGA SPRING –
Dixon’s bag filter retainer device designed to hold the bag filter or mesh
basket in place during filtration, keeping contaminates from going downstream.
Describes when a ﬁlter system is producing a ﬁltered product.
OPEN AREA – Pore
area of ﬁlter medium, often expressed as a percentage of the total area.
– Normal pressure at which a system operates.
CRITICAL – Pressure above the normal or design limits which may cause
damage or rupture.
MAXIMUM – Maximum pressure allowed in the system.
Describes the vast number of chemical substances containing carbon, hydrogen
– Substances in which an organic material will dissolve.
OUTER SHELL –
Outer covering of an element, usually perforated or screen.
OUTER WRAP –
Outside covering of an element.
OUTLET) – Ports integrally formed in a ﬁlter plate through which ﬁltrate
can escape from the ﬁlter chambers.
OUTSIDE-IN – Flow
of product from outside to inside of element.
OXIDATION – Chemical
combination of any substance in which the oxidation state (positive valence) of
an element is increased.
Compounds that contain oxygen, e.g. ethanol.
PAPER – Medium
used in many elements. A very general term applied to resin impregnated
cellulose. Many types of paper or cellulose, made to speciﬁcation, are used as
a ﬁlter medium.
PARTICLE – Single
piece of solid material which is small in relation to its environment. Normally
characterized by its size and shape.
PARTICLE COUNT –
Practice of counting particles of solid matter in groups based on relative
size. Frequently used in engineering a ﬁlter to a speciﬁc task or to evaluate
the performance of a ﬁlter under speciﬁc operating conditions. When used as
data to engineer a ﬁlter, proper consideration can be given the type of medium
to be used, expectant life of the medium, and the true cost of operation.
DISTRIBUTION – Tabulation resulting from a particle count of solids grouped
by speciﬁed micron sizes to determine the condition of either the inﬂuent or
efﬂuent stream. Usually expressed in percentage of total solids to the speciﬁc
group. Example: 31% in the 6 to 10 micron group. See particle count.
PARTICULATE – Relating
to minute, separate particles.
PD – Positive
Ability of a cake or medium to pass liquids; or the rate of ﬂow of ﬂuid under a
differential pressure through a material. Air permeability measurement provides
a convenient comparison for various media and indicates the construction
requirements for speciﬁc particle size retention. As a rule of thumb, lower
permeability values indicate ﬁner particle retentivity.
Material that has openings through which liquid will pass in ﬁltering. Also
referred to as porous or pervious.
PERVIOUS – See
pH RANGE –
Arbitrary scale of numbers from 0 to 14 indicating acidity or alkalinity of a
solution. A neutral solution has a pH of 7; below 7 represents acidity, and
above 7 represents alkalinity.
PHASE – May be
continuous, as the basic product ﬂowing through a housing; or discontinuous, as
the material to be removed from the basic product. Both are distinct and
– The demixing of a two-phase solution. In the case of ethanol and water, when
water reaches saturation – 100% RH – it will drop out of the ethanol enriched
fuel creating a phase layer on the bottom of the tank.
(PARTIAL) – When water remains suspended in ethanol enriched fuel prior to
phase separation. This happens with less than full saturation and is usually
visible resulting in hazy fuel.
PHENOLIC RESINS –
Synthetic thermosetting resins obtained by the condensation of phenol or
substituted phenols with aldehydes. Used as a binder in cellulose and glass
ﬁbers to form ﬁlter media.
PIGGING – The
practice of using a device call a pig to perform maintenance on a pipeline,
e.g. cleaning and inspecting. Pigging is often performed without disrupting
product flow. It is associated with fuel
PLASTISOL – Suspension
of a thermosetting plastic which can be molded into any desired shape. Used as
a combination end cap and gasket on element.
PLEAT, PINCHED –
Pleat in a pleated ﬁlter element, closed off by excessive differential pressure
or crowding, thus reducing the effective area of the ﬁlter element.
PLEAT, SPACERS –
Used to prevent the collapse of pleats in a pleated paper cartridge, under the
action of differential pressure. Examples are individual spacers of expanded
metal or plastic and continuous spacers of plastics or woven materials, usually
Physical form of cartridge made into a convoluted form to resemble the folds in
PLEATING – In
ﬁlters with paper medium or other sheet material, pleating means the folding
processes which provide a large surface area within a given volume of ﬁlter.
PLUGGING – Filtered
out particles ﬁlling the openings in a medium to the extent of shutting off the
ﬂow of product; loading up of the medium so as to reduce capacity. Also
referred to as blinding or blocking.
Union of monomers or molecules to form a polymer consisting of giant molecules.
Bonding of two or more monomers to produce a polymer. Any chemical reaction
that produces such a bonding.
Synthetic plastics formed by action of di-isocyanates on dihydric alcohols,
polyesters or polyethers.
PORES – Openings
in a medium. Also referred to as interstices. Size and shape of openings in
cellulose are closely controlled in manufacture.
DISTRIBUTION – Exclusive to permeable medium; describes the number of pores
in various groups of sizes in a way similar to that discussed under particle
size distribution. Data are valuable in assessing ﬁltration performance from
POROSITY – Ratio
of void volume to total cake volume. Also ﬁlter medium which may have larger
pores than any other media.
POROUS – Material
that has openings through which liquid will pass in ﬁltering. Also referred to
as permeable or pervious.
PUMP OR PD PUMP – known as a constant volume pump because they maintain a
constant speed and flow even under pressure variations. Significantly more
efficient than centrifugal pumps when handling viscous fluids. Dixon’s PD
design is self-priming and is known for its dry-lift and dry-run capability,
unmatched by its competitors.
POUR POINT –
Lowest temperature at which a liquid will pour or ﬂow when chilled without
disturbance under speciﬁed conditions.
PPM – Parts per
million. A unit of concentration; e.g., 3 ppm would be 3 pounds of solids in
1,000,000 pounds of water.
Operation of depositing an inert material (ﬁlter aid) prior to beginning
PREFILT – Material
to be ﬁltered. Also referred to as concentrate, feed, inﬂuent, intake, liquor,
mud, pulp, slimes or sludge.
Filter for removing gross contaminate before the product stream enters a ﬁlter
separator. Used to remove gross solids.
– Two-stage, horizontal housing for efﬁcient solids and water removal at high
ﬂow rates. Used on light gravity streams.
SEPARATOR SYSTEMS – Three-stage systems for use where stream carries an
unusually high amount of solids; preﬁlter elements in ﬁrst stage remove bulk of
solids and permit coalescer and separator elements in next two stages to
function more effectively for phase separation.
– Gauge pressure plus 14.7 psi.
– Force exerted by the atmosphere at sea level; equivalent to 14.7 psi.
IN ATMOSPHERES – Total gauge pressure divided by 14.7 and expressed in
– In a mixture of gases, each gas exerts a pressure equal to the total pressure
multiplied by the move fraction (or volume fraction) of the individual gas. The
sum of the partial pressures equals the total pressure.
PRESSURE, PROOF –
A test pressure above normal operating pressure to assure that part will
withstand the norm without damage or leakage.
– Difference in pressure between two points.
PRESSURE DROP –
Difference in pressure between two points, generally at the inlet and outlet of
a ﬁlter or a ﬁlter separator. Measured in pounds per square inch gauge, or inches
PRESSURE DROP, CLEAN
– Differential pressure (drop) across a housing measured in pounds per square
inch at rated ﬂow on new elements with clean product.
MAXIMUM ALLOWABLE – Maximum pressure differential of a housing under speciﬁed
product and ﬂow conditions.
PRESSURE RELIEF –
Valve which permits enough liquid or gas to escape from the housing to prevent
extreme pressure buildup within a housing.
Changing the properties of a liquid-solid mixture by physical or chemical means
to improve its ﬁlterability. Chemical means include coagulation, ﬂocculation
and conditioning; physical means include size classiﬁcation, preaeration,
mechanical agitation, freezing and thawing, heating, ultrasonic and mechanical
vibrations, electronic and magnetic treatment and ionizing radiation. Filter
aids are also used for pretreatment.
PSI – Pounds per
PSIA – Pounds per
square inch absolute.
PSID – Pounds per
square inch differential.
PSIG – Pounds per
square inch gauge.
(RH) – Percentage relation that the actual amount of water vapor present in
the given volume of air at a deﬁnite temperature bears to the maximum amount of
water vapor that would be present if the air were saturated with water vapor at
Quality of repelling water, or being hydrophobic; opposite of water wettable.
Element which is to be discarded after use and replaced with an identical
element. Same as disposable. Opposite of reusable.
RESIDUE – Solids
deposited upon the ﬁlter medium during ﬁltration in sufﬁcient thickness to be
removed in sheets or sizable pieces. Sometimes referred to as cake or
– Treatment of ﬁber used in ﬁlter elements. Impregnation is carefully
controlled in the manufacture of cellulose and provides a binder for the ﬁbers
which must be cured to speciﬁcation during cartridge manufacture to preserve
all the properties of the original speciﬁcation for the cellulose.
– Filter papers used to construct pleated paper cartridges in order to give
high mechanical strength. Typically 30% by weight of phenol formaldehyde,
polyurethane or epoxide resins are added.
Ventilation filter. Pressure drop across a ﬁlter at a stated ﬂow and under
given conditions; generally expressed in millimeters water gauge, or in SI
units as N/m2 or Pascals. See also flow resistance.
RETAINER – Any
device which holds a component in place.
Ability of ﬁlter medium to retain particles of a given size.
RETROFIT – Term
used for the conversion of a ﬁlter or ﬁlter separator.
Modifying equipment to make changes of added features that have been an
improvement to product.
Element which may be cleaned and used again. Opposite of disposable or
RFS – Renewal
RH – Relative
SAMPLE – A
portion extracted from a total volume that may or may not contain constituents
in the same proportions that are present in that total volume.
SAMPLE (BOTTOM) –
A spot sample collected from the bottom of the tank. Exact sampling location
should always be noted when collection is made. Also referred to as the dead
bottom sample – taken from the lowest accessible point in the tank.
SAMPLE (LOWER) –
Sample collected from the middle of the bottom one-third of the tank’s contents.
SAMPLE (MIDDLE) –
Sample collected from the middle of the tank’s contents, one-half of the depth
SAMPLE (UPPER) – Sample
collected from the middle of the upper one-third of the tank’s contents.
SAMPLE (TOP) –
Sample collected 6 inches below the top surface of the liquid.
– Blend of samples collected from each layer in the tank combining upper, middle
and lower samples. Sometimes referred to as a consolidated sample.
SAMPLE (DRAIN) –
Sample collected from the water drain on a storage tank or filter housing.
SAMPLING – All of
the steps required to obtain a sample that is representative of the contents in
a tank and to place that sample in a container for analysis.
SATURATION – When
water in fuel reaches 100% RH.
SCREEN – Covering
for element for physical protection; also used as a basic material for a
separator element or the basket in a basket strainer. May have special coating
such as Teﬂon®*.
SCREW BASE –
Element base which is threaded to mounting by screwing the cartridge onto the
SEAL – Any device
which serves the purpose of sealing. Examples: center seal, gaskets, O-Rings,
and mounting caps. May also include two precision machined surfaces that seal,
referred to as a metal to metal seal.
SEAL NUT –
Gasketed nut which holds element cap in place.
Action of the settling of the suspended solids.
Action of separating solids or liquids from ﬂuids. May be accomplished by
impingement, ﬁltration, or by coalescing. Term “separation” is used by some to
refer to separation of liquids; also used to describe the action in the second
stage of two-stage separation. Teﬂon is a registered trademark of E.l. DuPont
de Nemours Co., (Inc.)
SHELL – Outer
wall of a housing. Also referred to as a body or housing.
SIEVING – Occurs
when filtering through pores with identical dimension such as a screen or mesh.
SKID-MOUNTED – One
or more housings with pump and motor, all mounted on a portable platform.
SOLIDS – Mass or
matter contained in a stream, considered undesirable and should be removed;
that part of the discontinuous phase removed from liquid or gas through
SOLUBLE – Capable
of being dissolved in a ﬂuid. Opposite of insoluble.
SOLUTE – Liquid
which has passed through the ﬁlter. Also referred to as discharge liquor,
efﬂuent, ﬁltrate, mother liquor, or strong liquor.
Single-phase combination of liquid and non-liquid substances, or two or more
Substance, usually a liquid, in which another substance becomes dissolved;
solvent will generally comprise the greater part of the solution.
SP. G. – Speciﬁes
gravity. The weight of any substance relative to the weight of water (water Sp.
G. = 1.0).
SPACE – Area
available to install a ﬁlter, ﬁlter separator, or entrainment separator.
– Ratio of Weight of any volume of a substance to the weight of an equal volume
of another substance. Water for solids and liquids, and air or hydrogen for
Cartridge ﬁlter in which the ﬁlter body and the ﬁlter element have been
constructed as an integral disposable item. Filter change is quick by spinning
off the used unit from a ﬁxed ﬁlter head and quickly spinning on a replacement
BACTERIA – Bacteria which forms a resting cell, difﬁcult to destroy.
SS – Abbreviation
for stainless steel without reference to type or material speciﬁcation.
– Result of friction between two non-conductors such as ﬁlter or ﬁlter
separator elements and hydrocarbons; retained in the liquid dielectric.
STP – Submerged
SURFACE TENSION –
That property of liquids which tends to contract the exposed surface to the
smallest possible area; i.e., cohesion between like molecules.
SURFACE TENSITY –
State or quality of the exposed surface of liquids.
Coined expression for surface active agents which are sometimes called
emulsiﬁers or wetting agents. First appeared in hydrocarbons with the advent of
the catalytic cracking process in reﬁning. Caused by the forming of sodium
sulfonate and sodium napthanate molecules. Affects liquid/liquid separation by
reducing interfacial tension and forming into a slime which blinds off the
ﬁbers used in coalescing media.
– Solids that do not dissolve in liquid; those that remain suspended and can be
removed by ﬁltration.
SUSPENSION – Any
liquid containing undissolved solids.
SWING BOLT – Type
of housing head closure which reduces service time. Opposite of thru-bolt ﬂange
where studs and nuts are used, such as with ASA type ﬂanges.
The practice of transporting different fuels back-to-back in the same tank.
This results in the majority of cross-contamination issues.
Registered trade name of E.I. DuPont de Nemours Co., (Inc.) for a material
having non-stick characteristics. Facet’s screen separator cartridges are made
of Teﬂon coated mesh and are hydrophobic (repel water). Sometimes a Teﬂon
material is used for gaskets.
– Temperature measured from absolute zero which is minus 273°C, or minus 460°F;
e.g., 70°F is 460 plus 70 or 530°R. (R stands for degrees Rankin), and 70°C is
273 plus 70 or 343° Kelvin.
– Pressure drop across the unit at the time system is shut down, or when the
maximum allowable pressure drop is reached.
– Steady velocity achieved by a falling particle when gravitational forces are
balanced by viscous forces. See Stokes’ Law.
THRU-BOLT – Type
of housing closure using studs and nuts, such as in ASA type ﬂanges.
Method of analyzing a solution by adding another solution until a given
reaction is produced.
TORTUOUS PATH –
Crooked, twisting, or winding path which tends to trap or stop solid
TOXIC – Having a
TURBIDITY – Any
insoluble particle that imparts opacity to a liquid. TURBULENT FLOW—Flow regime
in which the ﬂow characteristics are governed mainly by the inertia of the
ﬂuid. Turbulent ﬂow in ducts is associated with high Reynolds Number (Re). It
also gives rise to high drag forces.
SEPARATOR – Liquid ﬁlter separators and preﬁlter coalescers containing two
kinds or types of replaceable elements. Air/gas ﬁlter separators containing one
kind or type of replaceable element in addition to a ﬁrst-stage bafﬂe. As
opposed to single-stage, three-stage, or four-stage ﬁlter separators. Two-stage
ﬁlter separators are considered the most efﬁcient device to separate immiscible
ULLAGE – The
volume of available space in a tank unoccupied by contents. Also referred to as
ULSD – Ultra Low
Sulfur Diesel with a sulfur content of no more than 15 ppm in the USA and 10
ppm in the Europe.
Release downstream of trapped contaminate. Due to change in ﬂow rate,
mechanical shock, vibration, excessive pressure build-up or medium failure.
Portion of the product stream which has not yet entered the system.
Degree of ﬂuidity; property of ﬂuids’ molecular structure by virtue of which
they resist ﬂow. Resistance to ﬂow exhibited by a liquid resulting from the combined
effects of cohesion and adhesion. Units of measurement are poise and stoke. A
liquid has a viscosity of one poise if a force of one dyne per square
centimeter causes two parallel liquid surfaces one square centimeter in area
and one centimeter apart to move past one another at a rate of one centimeter
per second. There are a great many crude and empirical methods for measuring
viscosity which generally involve measurement of the time of ﬂow or movement of
a ball, ring, or other object in a specially shaped or sized apparatus.
VISCOSITY INDEX –
Numerical value assigned to a lubricating oil which indicates to what degree
the oil changes in viscosity with change in temperature. Higher (VI) viscosity
index oils show the least amount of change.
VITON A – Trade
name for material used in gaskets and 0-rings.
VOID CHANNELS –
Open passages of the medium through which the liquid travels.
– Obstructions in the void openings which interfere with ﬂow.
VOIDS – Openings
in the medium. Also referred to as interstices or pores.
WASTE – Material
removed, rejected, or otherwise lost in various manufacturing processes.
WATER (FREE) –
Water not bound to an inorganic surface that can flow freely and existing in a
separate phase. Forms in the bottom of fuel tanks once saturation is reached.
– Tiny droplets of water suspended in fuel. Makes fuel look cloudy.
– Water in solution in petroleum. Dissolved water is often finds its way into
fuel in the form of condensation. Surfactants help to suspend and bond the
water to the fuel by reducing IFT.
– Water suspended in petroleum. Includes emulsions, but does not include
WATER LEG – Area
of housing for collection of water. Also called the sump.
WATER WETTABLE –
Capable of accepting water, or being hydrophilic; opposite of repellency or
WAX – Crystals
that form in diesel fuel as a result of low temperatures. Causes cloudy fuel and clogged filters.
WEIGHT OF SOLIDS
– Measure of solid particulate matter contained in a ﬂuid sample. May be
reported in various units such as milligrams per liter, weight percent, pounds
per barrel, etc.
CHARTER (WWFC) – Organization established in 1998 by engine manufacturers
to help set the standards for fuel quality and cleanliness.
YOKE – End cap
used to hold a cartridge in place.