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Filtration Glossary continued g-m

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Filtration Glossary continued g-m

Machine Coolant Filtration Glossary

Here is a glossary of Filtration Terms and their meanings.  Please refer to the Machine Coolant Filtration Index for articles and information on these topics.


A - C  |  D - FG  |  H  |  I  |  J  |  K  |  L  |  M  |  N - R  |  S - Z 


Galvanic Action,  A type of corrosion caused when two dissimilar metals are in contact and are wetted by a conductive liquid.  Galvanic action can cause rapid, severe loss of metal at a joint. 

Gas Scrubber:  A vessel designed to knock out liquid and solid contaminates by impingement on a series of baffles or demister pads.  Accomplished by drastic reduction of velocity as the gas enters the scrubber.  Recent advances made in entrainment separation would expand the general use of the term to include mechanical cartridge type separators. 

Gauge Pressure, The pressure indicated by a gauge connected to a system.  Gauge pressure instruments are set to read zero at conditions of normal atmospheric pressure.  See absolute pressure, differential pressure, head pressure, static pressure. 

Gel,  Soft, deformable solid.  Gel particles can cause problems in filters.  Gel particles may deform under pressure allowing them to squeeze through a filter.  Gel particles may spread under pressure, quickly binding off the surface of a filter.  Gel slugs can ruin coatings on photographic materials, paint finishes or other critical coatings. 

Giardia, Giardia lamblia is a protozoa that infects the intestinal tract of humans and water loving mammals such as beavers and muskrats.  Giardia survives in fresh water streams or lakes in the form of cysts.  The cysts are approximately 8um X 12um in size and can be removed from water by filtration.  Symptoms of giardiasis may take several weeks to appear after injection of cysts.  The infection causes considerable gastric discomfort and while not considered a fatal disease, it usually requires treatment by a physician. 

Glass Fiber:  The proper reference to a fibrous material made from glass that is commonly used as a filter and separator media.  Glass fibers may be used in blanket or tube form and, due to the random dispersal of the fibers; the material makes a good filter media.  Glass fibers are hydrophilic (water wettable) and as such, 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. 

Glass Textile:  Glass in a form suitable for spinning, weaving, etc.  It is manufactured in two common forms, continuous filaments or staple fibers of comparatively short but spinnable length. 

Glycol:  A general term for family a\of alcohols, clear, colorless, and soluble to varying degrees in water, alcohol, ether, benzene, etc.  Has a wide range of usage such a machine coolants, antifreeze, and processes.  Refer to specific type for further details. 

GMP,  Good Manufacturing Practice.  Documents published to guide manufacturers of materials, particularly in industries regulated by the FDA. 

GPD: Gallons per day. 

GPH:  Gallons per hour. 

GPM:  Gallons per minute. 

Gravity Filtration,  A filter system which relies on the head pressure of the liquid for the driving force to move the liquid through the filter. 

Gravity Separation:  Separation of immiscible phases resulting from a difference in specific gravity by coalescing. 

Grooved Coupling:  A clamp-like device with tongue-like edges which fit into grooves; forms a seal when secured. 

Guard Filter,  A filter placed in a system downstream of a primary filter.  Under normal operating conditions the particles are removed before the liquid gets to the guard filter.  The purpose of the guard filter is to trap particles that get through the primary filter during an upset or other non-routine conditions. 

Gurley,  A test used to measure the air permeability of materials with relatively low permeability, I.e. membrane materials.  The test measures the time necessary for a selected volume of air to pass through a fixed sample area at a fixed pressure.  Data is expressed as time with a volume reference. 



Head Gasket:  A seal by means of a gasket at the main closure of a pressure vessel.  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 vessel in order to permit access to interior of vessel. 

Head Pressure,  Pressure in a system caused by the height and density of fluid present in the system above the point of measurement.  Head pressure at the base of the tower is full of water and the tower is 100 feet tall, we would say that the head pressure at the base of the tower is 100 feet of water. 

Heat of Adsorbtion:  The heat released when a substance is adsorbed.  It is the heat equivalent to the energy which the adsorbate must give up in going from its normal energy state to lower energy state it has when adsorbed.  The heat depends on the adsorbate and the adsorbent. 

Heat Of Vaporization:  The heat which must be put into a liquid to vaporize it at its boiling point. 

Hemp:  A soft fiber obtained from the inner bark of the hemp plant (Cannabis sativa; grown in Kentucky, Wisconsin, Italy, or Russia.  The fibers are steel gray to creamy white in color, usually occurring in narrow, flat ribbons of three to eight feet in length.  The fibers are obtained by retting, similar to flax.  Hemp is quite strong and pliable; it withstands the rotting action of water, and consequently is a very valuable cordage fiber.  Its principal uses are in the manufacture of twines and ropes, although some finer grades are used in weaving.  The term “hemp” is indiscriminately applied to a great many fibers such as Manila hemp, sisal hemp, etc. 

Holding Capacity:  In general usage 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. 

Honeycomb Weave:  Pattern of these fabrics resembles the cellular comb of the honey bee; is used for drainage cloths beneath the regular filter cloth.  Also called waffle weave. 

Hook:  Device to aid in the mounting of the elements held in position by the extension spring. 

Hydrocarbon:  Any one of a large number of compounds composed primarily of elements carbon and hydrogen.  As they increase in molecular weight and boiling point they may be respectively gases, liquids, or solids. 

Hydrophilic:  Water accepting or water wetting.  Having an affinity for water.  Capable of uniting with or dissolving in water.  Effective coalescing requires a media to have hydrophilic characteristics which cause 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:  A test conducted with either air, water, or other fluids at a given value over design pressure, to prove the structural integrity of a pressure vessel.  



I.D.:  Inside diameter. 

IFT:  Interfacial tension. 

Immiscible:  Incapable of being mixed; insoluble; opposite of miscible. 

Impingement:  Process of removing liquid or solid contaminate from a stream of compressed air or gas by causing the flow to impinge on a baffle plate at a high velocity.  This causes the contaminate to fall off by gravity into a large quiescent sump area to prevent the contaminates from being picked up a second time by the velocity of the stream.  May also be used on liquid streams to separate solid contaminates. 

Inert:  Inactive chemically or physically. 

Influent:  Stream of fluid at the inlet of a filter or separator/filter.  Same as affluent. Opposite of effluent. 

Inhibitor:  A general term for 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 changes the interfacial tension of a petroleum product, which may reduce the coalescing efficiency of some media.  Reduced interfacial tension between two liquids causes a tighter emulsion which is more difficult to break up by coalescing. 

Initial Pressure Drop:  Loss in differential pressure between two points upon the start of flow through a vessel using new elements. 

In-Line:  Describes inlet and outlet connections which are positioned at the same height on opposite sides of a vessel so that an imaginary straight line could be drawn connecting one to the other.  Also describes a small filtration unit that fits into a line and forms a similar image to the line, as in the case of a hose. 

Inorganic:  Not formed from living substance; those 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, liquid, mud, prefilt, pulp, slimes, or sludge. 

Interchangeable:  General use describes one particular element which may be used in place of another particular element.  Dimensions of both must be equal.  The element being substituted frequently has more desirable characteristics than the element which it replaces.  Refers primarily to dimensional interchangeability and must be for the same general application. 

Intercrimp (Wire Cloth):  Extra crimps in warp and fill wires between intersections.  Generally used in wide mesh, light wire combinations to stiffen fabric and assure accurate mesh.

 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.  Interfacial tension increases as miscibility or solubility decreases.  See inhibitors for effect on coalescing. 

Interpleat:  The pleat of two or more filter media into an element, such as glass fibers and cellulose. 

Interstitial:  Pertaining to the openings in the medium. 

Ion:  An electrically charged atom or group of atoms, formed by the gain or loss of electrons. 

Ion Exchange:  A reversible chemical reaction, usually between a solid and a liquid in which ions may be interchanged.  This process is used to advantage in many industries; water softening, iron removal from wines and beer, recovery of chromate from plating solutions, etc. 

Ion Exchange,  A process commonly used to remove undesirable ions from water, resulting in deionized water.  A strong acid ion exchange resin will release hydroxyl groups in exchange for metal cations in solution.  A strong base resin will release hydroxyl groups in exchange for anions in solution.  Over a period of time the ion exchange resins are exhausted and need to be regenerated. 

Inverted Emulsion,  An emulsion with oil droplets that have water trapped inside the oil. 

Isokinetic Sampling,  An isokinetic sample probe draws fluid into the probe at the same velocity as the velocity of the fluid flowing past the probe in the duct or pipe.  Non-isokinetic sampling may result in a sample with a particle concentration and size distribution that is not the same as what is present in the bulk flow. 

Isotherm:  A constant temperature curve. 

Isotropic:  Having same properties in all directions. 



Jute:  A soft long multicellular fiber, obtained from the bast or inner bark of two closely related plants, round-pod jute (Corchorus capsularis) and long-pod (Corhosus olitorius).  Jute is grown extensively in India and practically all of it is water retted.  The fibers are from three to fifteen feet long and creamy white to brown in color.  Because of its cheapness, availability, and ease of manufacture, jute is used in tremendous quantities, especially for cotton bale covering, burlap bags of all kinds, coarse yarns and twine.  Jute is not a particularly strong fiber and it is lacking in elasticity and durability.




Keiselguhr,  A German word for a filter aid that is similar to diatomaceous earth. 

Knife Edge Pleats:  The sharply defined creases at the outer edge of a pleated element. 

Knife Edge Seal:  A narrow pointed ridge on the sealing surface of an end cap, center seal, or cartridge adaptor which provides a seal by “biting” into the cartridge gaskets.



Lacquer:  A 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. 

Laid Fabric:  A material made without the use of a filling yarn, the parallel warp yarns being held together with rubber latex or other binding substance. 

Laminar Flow,  Streamline flow, parallel to the duct or pipe.  Absence of turbulence, eddys or other localized disturbances.  See turbulent flow, Reynold’s number. 

Latex,  Latex particles are available in monodisperse ( single size) suspensions.  These suspensions consist of uniform, white latex spheres of very uniform size.  The suspensions are useful for calibrating size measuring instruments and for challenging filters with a known particle size. 

Leaf:  A filter component used for supporting the filter medium.  Also an arrangement of flat materials to function as a filter. 

Life:  The useful time of use for a filter before it plugs. 

Life Expectancy:  The amount of use which may be expected from en element before it must be replaced; it will vary according to the element’s characteristics, the operating conditions, and the condition of the influent.  See article on When Machine Coolant becomes unusable. 

Line Size:  The size of line used to carry the product in a system such as six-inch line. 

Liquid:  The product stream in liquid filtration and liquid separation/filtration.  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 vessel after separation.  In the case of air or gas, it would operate off the surface of the liquid. 

Liquid Level Gauge:  A gauge by which the interface of two immiscible liquids can be viewed. 

Liter:  1.057 quarts.  Used as volumetric standard to analyze liquids for water or solids content. 

Loading Capacity,  The amount of contamination a filter has collected when it reaches the end of it’s useful life.  Loading capacity is usually expressed as a weight of contaminant present in the filter when the filter reaches a designated differential pressure at a designated flow rate.  Along with efficiency, loading capacity is a primary measure of the value of a filter. 

Lock Crimp (Wire Cloth):  Deep crimps in wires at points of intersection that lock wires securely in place.  Usually used for heavy duty wire screening. 

Lock Up:  A device that will lock either a column or elements or the body of a vessel in place. 

Log Reduction Value,  The logarithm of the filtration ratio for a filter or a filtration process.  For example, a filtration ratio of 100,000 would have a log reduction value of 5.  Log reduction values are commonly used to describe a reduction of bacteria concentration.  See filtration ratio, beta ratio, penetration, efficiency.

Long Staple Cotton:  Cotton having a staple length of 1-1/8” or more. 



Main Closure:  When there is more than one opening into a vessel, the closure through which vessel is serviced. 

Makeup, The introduction of fresh liquid to replace that which was lost from the system. 

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. 

Manometer,  An instrument used for measuring gas pressure.  A manometer is a U shaped tube with a liquid in the bottom part of the U.  When one leg of the U is connected to a source of unknown pressure, the pressure challenges are useful for precise measurement of filter particle removal characteristics.  See heterodisperse. 

Mass:  The matter contained by a body, regardless of its location. 

Mass Transfer:  Movement of matter. 

Mass Transfer Rate:  Measurement of movement of matter as a function of atoms, etc. 

Matter:  The material substance of which an element, elements, or mass is composed.  The word “element” in this use does not refer to cartridge elements.

Maximum Allowable Pressure Drop:  The maximum pressure differential of a vessel under specified product and flow conditions. 

Maximum Differential Pressure:  The highest pressure differential which an element is required to withstand structural failure or collapse. 

Maximum Operating Pressure:  The maximum pressure allowed in the system. 

Media:  Plural of medium.  Materials of which elements are made. 

Media Migration:  Carryover of fibers from filter, separator elements, or other filter material into the effluent.  Less definitive than fiber migration and is quantitative. 

Medium:  The principal component of an element.  A 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. 

Melamine Resins:  Synthetic resins of the thermosetting type, made from melamine and formaldehyde.  Certain types are used as binders in felt media. 

Membrane:  In filtration the term membrane is used to describe the media through which the liquid stream is to be passed or exchanged.  Membranes are normally associated with ion exchange media such as dialysis, osmosis, diffusion, etc., although filter paper itself could be classed as a membrane. 

Mercerization:  A finishing process extensively used on cotton yarn and cloth consisting essentially of impregnating the material with a cold, strong sodium hydroxide solution.  The treatment increases the strength and affinity for the dyes and, if done under tension, the luster is remarkably increased.  The latter phase is now regarded as the heart of the process although not a part of the John Mercer’s original patents.  Mercerization is done in the skein; the warp or the piece, either entirely or in printed effects.  The best results are obtained on combed yarns. 

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.  The term “mesh” should not be confused with clear openings or space. 

Meter Proving Tank:  A tank for calibrating capacity to provide volumetric proof of the delivery of liquids by positive displacement meters.  Also referred to as calibrating tank. 

Micron:  A short unit of length in the metric system.  One millionth of a meter, 10 centimeter, 10 millimeter, or 0.00039 of one inch.  Used as a criterion to evaluate the performance of efficiency of a filter media 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 a specific media or medium.  Absolute micron rating is generally taken to mean that all particles over a given micron value have been removed.  The naked eye can see a particle 40 microns or larger. 

Microorganisms:  Living bodies that can be seen only through a microscope. 

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 falling in fine drops. 

Mixing:  The process of intermingling fibers from different bales or lots to produce a uniform mixture of all.  Mixing usually implies the use of only one kind of fiber, while the term blending is usually used for combinations of different fibers, colors, etc. 

MMSCFD:  Million standard cubic feet per day. 

MMSCFH:  Million standard cubic feet per hour. 

MMSCFM:  Million standard cubic feet per minute. 

Mole:  A unit quantity in chemistry.  An amount of a substance in grains (gram mole) or pounds (pound mole) which corresponds to the sum of the atomic weights of all the atoms appearing in the molecule.  Sometimes referred to as a mol. 

Molecular Sieve:  Zeolite, natural or synthetic, or similar materials whose atoms are arranged in a crystal lattice in such a way that there are a large number of small cavities interconnected by smaller openings or pores of precisely uniform size.  Used as drying agents for some liquids or gases as well as for other absorptive applications.  May be regenerated for extended use under specified conditions. 

Molecular Weight:  The sum of the atomic weights of all the atoms in a molecule.  Sometimes referred to as mole weight or mol weight. 

Monofilament,  A single, continuous filament of fiber.  Some mesh products and filter materials are woven from monofilament fibers.  Monofilament fibers have relatively smooth surfaces and uniform round cross sections.  See multifilament. 

Montejus:  A closed pressure tank partially filled with a fluid mixture which is forced out by gas pressure on its surface. 

Mother Liquor:  The liquid which has passed through the filter.  Also referred to as discharge liquor, or strong liquor. 

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. 

MSCFD:  Thousand standard cubic feet per day. 

MSCFH:  Thousand standard cubic feet per hour. 

MSCFM:  Thousand standard cubic feet per minute. 

Mud Sump:  Area of a horizontal vessel, located upstream of the media, for the collection of solids falling out by gravity prior to going through the coalescing media, where gross solids are present in the stream. 

Mullen Burst Test:  A measurement of the force needed to burst a given area of paper or cloth, under fluid flow conditions, and usually expressed as the pressure in inches of water that will burst a 2” diameter test specimen. 

Multifilament,  A yarn having two or more continuous monofilaments twisted together.  Some filter materials are woven from multifilament yarns.  See monofilament. 

Multipass Test,  A filter test using a recirculating fluid as opposed to a single pass test.  Multipass testing is commonly used to evaluate performance of hydraulic filters.  Beta ratios are commonly measured using a multipass test.  In some systems small particles that pass through the filter are allowed to recourse of a test.  In other systems small particles are continuously removed by a cleanup filter downstream of the filter being tested.  Much of the original work on standard multipass testing was done at Oklahoma State University.  This test is sometimes called OSU multipass test.  ISO 4572 is a published standard for multipass testing.  Also listed as ANSI / B93.31. 

Multiple Cartridges:  Two or more cartridges fastened together end to end, to make up one element, or a vessel containing more than one cartridge.