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Glossary of Filtration Terms

ABRASION – 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.

ACETOBACTER – 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 influenced corrosion.

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.

ACTIVATED ALUMINA – 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.

ADHESION – 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.

AEROBIC – 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, caustics, etc.

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 from water.

API – American Petroleum Institute

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:

Degrees 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.

AROMATIC COMPOUNDS – Compounds related to six-carbon membered rings as benzene or its derivatives.

ASPHALTINES – Asphalt like particles found in crude oil than form in refined fuel as a result of oxidization.

ASME – American Society of Mechanical Engineers. Published code which governs the design of pressure housings.

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 end product.

ASTM INTERNATIONAL (ASTM) – American Section of the International Association for Testing Materials

ATMOSPHERIC PRESSURE – 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 micrometers.

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.

BIODIESEL – 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 filter elements.

BURST PRESSURE – The maximum pressure a housing will safely withstand.

BURSTING STRENGTH – Force required to burst a housing. Example: burst pressure may be 100 psi, while bursting strength may be 175 psi.

BYPASS – 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.

BYPASS INDICATOR – 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.

CARTRIDGE – 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 cartridge.

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 smallest diameter.

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.

CLARIFICATION – Filtration of liquids containing small quantities of suspended solids; filtration takes out most of these solids and increases the clarity of the liquids.

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 monoxide.

COAGULANT – That which produces coagulation or agglomeration of suspended solids.

COAGULATION – 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.

COALESCER – 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.

COALESCING – 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 less.

COLLOIDAL PARTICLES – 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.

COMPATIBILITY – 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 fluid stream.

COMPOSITE MEDIA – Media made up of more than one material.

COMPRESSIBILITY – 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.

CONSTITUENTS – 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.

CONTAMINATE – 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.

CONTAMINATION MONITOR – A device designed to measure particle contamination in-line or out of a sample jar. The monitor measures contamination using ISO code. See ISO.

CONTINUOUS PHASE – Basic product flowing through a filter or filter separator which continues on through a system after being subjected to solids and/or other liquid separation.

CONVERSION – 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.

CONVOLUTION – 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.

CONVOLUTIONS – 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.

CORROSION – 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.

CORRUGATIONS – 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.

CRITICAL OPERATING PRESSURE – Pressure above which filtration or separation equipment may produce reduced efficiency or fail to function properly.

DEGRADATION – 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.

DEHYDRATION – 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 purification.

DELTA or ΔP – A commonly used symbol denoting the pressure drop across a filter.

DENSITY – 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.

DIFFERENTIAL PRESSURE (ΔP) – Difference in pressure between two given points of a filter, filter separator, etc.

DIFFERENTIAL PRESSURE INDICATOR – Indicator which signals the difference in pressure at two points.

DIFFERENTIAL PRESSURE SWITCH – Electrical switch operated by the difference between two pressures and often used to give warning of the end of a filtration cycle.

DIFFERENTIAL RATING – 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.

DIFFUSIONAL 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.

DIRECT READING 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.

DIRECT INTERCEPTION – 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 holding capacity.

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 housing.

DISCONTINUOUS PHASE – Separated phase or product from the continuous phase. Example: water may be the discontinuous phase when separated from a hydrocarbon, air or gas.

DISPOSABLE – Describes element which is to be discarded after use and replaced with an identical element. Same as replaceable. Opposite of reusable.

DISSOLVED SOLIDS – Any solid material that will dissolve in the liquid that is being filtered.

DISTILLATE – Condensed product of distillation, as certain petroleum products.

DISTILLATION – 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 chambers.

DOWNSTREAM – 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 liquids.

DUPLEX FILTER – Assembly of two filters with valving for selection of either or both filters.

E10 – gasoline enriched with 10% ethanol.

EFFICIENCY – Degree to which element will perform in removing solids and/ or liquids.

EFFICIENCY CURVE – 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 influent.

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.

EMULSIFICATION – Dispersion of one substance in the form of minute drops within another substance.

EMULSION – 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 impossible.

EMULSION SEPARATION – 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.

ENCAPSULATED – 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.

ENTRAINMENT – Mist, fog, or droplets of a liquid which is usually considered a contaminant when used in the filtration industry.

FACILITATIVE ANAEROBES – Microbes that can live in both oxygen and non-oxygen environments

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.

FIBER – 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.

FIBERGLASS – 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 fiber.

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.

FILTER COALESCER – 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 septum.

FILTER SEPARATOR – 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 process.

FILTERABILITY – 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 medium.

FILTRATION (SINGLE PASS) – The process of passing liquid through a filter or system one time for the purpose for cleaning and achieving a specific cleanliness standard.

FILTRATION (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).

FLASH DISTILLATION – Operation wherein the liquid is vaporized immediately on entrance to the housing.

FLASH POINT – Lowest temperature at which a combustible liquid will give off a flammable vapor that will burn momentarily.

FLOCCULATION – 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.

FRACTIONAL 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 plugging.

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 Fiberglas.

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 day.

GPH – Gallons per hour.

GPM – Gallons per minute.

GRAVITY – 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.

GRAVITY SEPARATION – 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.

HOLDING CAPACITY – 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 liquid.

HOMOGENEITY – Uniformity of particle size and distribution of a solid in the product.

HUMBUGS – 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.

HYDRODESULPHURIZATION (HDS) – Process of removing sulfur from refined petroleum products in order to reduce SO2.

HYDROPHILIC – 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.

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.

HYDROSTATIC TEST – 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.

HYGROSCOPIC – Water absorbing, e.g. ethanol is easily absorbed into water.

ID – Inside diameter

IFT – Interfacial tension

IMMISCIBLE – incapable of being mixed; insoluble; opposite of miscible.

IN SITU – In its original place.

INERT – Inactive chemically or physically.

INFLUENT – Stream of fluid at the inlet of a filter or filter separator. Same as affluent. Opposite of effluent.

INHIBITOR – 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 location.

INORGANIC – Not formed from living substance; substances which do not contain carbon as a major constituent.

INSIDE-OUT – Flow of product from inside to outside of element.

INSOLUBLE – 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.

INTERCHANGEABLE – 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 applications.

INTERFACE – Surface over which continuous phase and discontinuous phase are in contact.

INTERFACIAL TENSION – Measure of miscibility or solubility of the continuous and discontinuous phases. Increases as miscibility or solubility decreases. See inhibitors for effect on coalescing.

INTERPLEAT – Pleating of two or more filter media into an element, such as glass fibers and cellulose.

INTERSTICES – 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.

INTERSTITIAL – Pertaining to the openings in a medium.

INERTIAL IMPACTION – 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.

ION – Electrically charged atom or group of atoms, formed by the gain or loss of electrons.

ION EXCHANGE – Reversible chemical reaction, usually between a solid and a liquid, in which ions may be interchanged.

I.P. – The Institute of Petroleum.

ISO – International Standards Organization.

ISO CONTAMINATION CODE – ISO code for measuring contamination. A standard of measurement used internationally.

JET FUEL – Petroleum product used as fuel for jet engines.

KARL FISHER – Analytical method of determining amount of water present in a sample by titration.

KEROSENE – 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 explosion limits.

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 gauge.

LIQUOR – Material to be filtered.

LITER – 1.057 quarts. Used as a volumetric standard to analyze liquids for water or solids content.

LOW INTERFACIAL 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.

MAXIMUM ALLOWABLE PRESSURE DROP – Maximum pressure differential of a housing under specified product and flow condition.

MAXIMUM DIFFERENTIAL PRESSURE – Highest pressure differential which an element is required to withstand without structural failure or collapse.

MAXIMUM OPERATING PRESSURE – Maximum pressure allowed in the system.

MEAN EFFICIENCY 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 quantitative.

MEDIUM – 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 dialysis.

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 waste.

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.

MIGRATION – 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.

MISCIBLE – Capable of being dissolved, soluble. Opposite of immiscible.

MIST – Visible water or hydrocarbon vapor; floating or failing in fine drops.

MOTIVATING FORCE – That which causes the coalescing, filtering or separating action to take place.

MS – Military Standard. Prefix to government-assigned numbers indicating standardized items to military specifications.

NAPHTHENIC ACID – Acid compounds commonly found in crude oil.

NOX – Nitrogen oxide.

NOMINAL – 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 diameter.

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.

ON-STREAM – 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.

OPERATING PRESSURE – Normal pressure at which a system operates.

OPERATING PRESSURE, CRITICAL – Pressure above the normal or design limits which may cause damage or rupture.

OPERATING PRESSURE, MAXIMUM – Maximum pressure allowed in the system.

ORGANIC – Describes the vast number of chemical substances containing carbon, hydrogen and oxygen.

ORGANIC SOLVENTS – 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 (FILTRATE 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.

OXYGENATES – 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.

PARTICLE SIZE 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 displacement pump.

PERMEABILITY – 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.

PERMEABLE – Material that has openings through which liquid will pass in filtering. Also referred to as porous or pervious.

PERVIOUS – See permeable.

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 separate.

PHASE SEPARATION – 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.

PHASE SEPARATION (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 contamination.

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 wire-cloth.

PLEATED – Physical form of cartridge made into a convoluted form to resemble the folds in an accordion.

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.

POLYMERIZATION – 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.

POLYURETHANES – 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.

PORE SIZE 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 various standpoints.

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.

POSITIVE DISPLACEMENT 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.

PRECOATING – Operation of depositing an inert material (filter aid) prior to beginning filtration.

PREFILT – Material to be filtered. Also referred to as concentrate, feed, influent, intake, liquor, mud, pulp, slimes or sludge.

PREFILTER – Filter for removing gross contaminate before the product stream enters a filter separator. Used to remove gross solids.

PREFILTER COALESCER – Two-stage, horizontal housing for efficient solids and water removal at high flow rates. Used on light gravity streams.

PREFILTER COALESCER 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.

PRESSURE ABSOLUTE – Gauge pressure plus 14.7 psi.

PRESSURE, ATMOSPHERIC – Force exerted by the atmosphere at sea level; equivalent to 14.7 psi.

PRESSURE, EXPRESSED IN ATMOSPHERES – Total gauge pressure divided by 14.7 and expressed in atmospheres.

PRESSURE, PARTIAL – 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.

PRESSURE DIFFERENTIAL – 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 of mercury.

PRESSURE DROP, CLEAN – Differential pressure (drop) across a housing measured in pounds per square inch at rated flow on new elements with clean product.

PRESSURE DROP, 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.

PRETREATMENT – 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 square inch.

PSIA – Pounds per square inch absolute.

PSID – Pounds per square inch differential.

PSIG – Pounds per square inch gauge.

RELATIVE HUMIDITY (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 that temperature.

REPELLENCY – Quality of repelling water, or being hydrophobic; opposite of water wettable.

REPLACEABLE – 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 discharged solids.

RESIN IMPREGNATED – 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.

RESIN IMPREGNATION – 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.

RESISTANCE – 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.

RETENTION – Ability of filter medium to retain particles of a given size.

RETROFIT – Term used for the conversion of a filter or filter separator.

RETROFITTING – Modifying equipment to make changes of added features that have been an improvement to product.

REUSABLE – Element which may be cleaned and used again. Opposite of disposable or replaceable.

RFS – Renewal Fuel Standard.

RH – Relative humidity.

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 of liquid.

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.

SAMPLE (COMPOSITE) – 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 cartridge adaptor.

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.

SEDIMENTATION – Action of the settling of the suspended solids.

SEPARATION – 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.

SO2 – Sulfur dioxide.

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 filtration.

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.

SOLUTION – Single-phase combination of liquid and non-liquid substances, or two or more liquids.

SOLVENT – 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.

SPECIFIC GRAVITY – 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 gases.

SPIN-ON-FILTER – 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 unit.

SPORE FORMING BACTERIA – Bacteria which forms a resting cell, difficult to destroy.

SS – Abbreviation for stainless steel without reference to type or material specification.

STATIC GENERATION – Result of friction between two non-conductors such as filter or filter separator elements and hydrocarbons; retained in the liquid dielectric.

STP – Submerged turbine pump.

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.

SURFACTANTS – 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.

SUSPENDED SOLIDS – 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.

SWITCH-LOADING – The practice of transporting different fuels back-to-back in the same tank. This results in the majority of cross-contamination issues.

TEFLON® -- 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, ABSOLUTE – 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.

TERMINAL PRESSURE – Pressure drop across the unit at the time system is shut down, or when the maximum allowable pressure drop is reached.

TERMINAL VELOCITY – 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.

TITRATION – 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 particulate matter.

TOXIC – Having a poisonous effect.

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.

TWO-STAGE FILTER 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 liquids.

ULLAGE – The volume of available space in a tank unoccupied by contents. Also referred to as outage.

ULSD – Ultra Low Sulfur Diesel with a sulfur content of no more than 15 ppm in the USA and 10 ppm in the Europe.

UNLOADING – Release downstream of trapped contaminate. Due to change in flow rate, mechanical shock, vibration, excessive pressure build-up or medium failure.

UPSTREAM – Portion of the product stream which has not yet entered the system.

VISCOSITY – 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.

VOID RESTRICTION – 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.

WATER (EMULSIFIED) – Tiny droplets of water suspended in fuel. Makes fuel look cloudy.

WATER (DISSOLVED) – 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 (ENTRAINED) – Water suspended in petroleum. Includes emulsions, but does not include dissolved.

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 hydrophobic.

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.

WORLDWIDE FUEL 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.