ÿþ Glossary
 
 
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A Back to top
Abrasion A general wearing away of a surface by constant scratching, usually caused by the presence of foreign material like dirt, grit, or metallic particles in the lubricant. Can result in a break down of the material (such as the tooth surfaces of gears). Abrasion results from lack of lubrication.
Abrasive wear Also known as "cutting wear", results when hard surface asperities or hard particles that have embedded themselves into a soft surface grind grooves into the opposing harder surface, such as with a journal.
Absolute filtration rating The diameter of the largest hard, round particle that will pass through a filter under set testing parameters. Indicates the largest opening in the filter elements.
Absolute Pressure The total of atmospheric and gage pressure.
Absolute Viscosity A term used interchangeably with viscosity to distinguish it from either kinematic viscosity or commercial viscosity. Absolute viscosity results from the ratio of shear stress to shear rate. It means the fluid's internal resistance to flow and is expressed with the unit poise. Absolute viscosity divided by fluid density equals kinematic viscosity. It is sometimes referred to as dynamic viscosity. Absolute viscosity and kinematic viscosity are reported in fundamental units. Commercial viscosity such as Saybolt viscosity are expressed in various units of time, such as seconds.
Absorbent filter A filter medium which mechanically holds the contaminant.
Absorption The assimilation of one material into another; in petroleum refining, the use of an absorptive liquid to selectively remove elements from a process stream.
Accumulator A container in which fluid under pressure creates a source of fluid power.
ACEA Association des Constructeurs Européens d'Automobiles (Association of European Automotive Manufacturers)
Acid number The amount of base, represented in milligrams of potassium hydroxide, necessary to neutralize the acidic particles in a 1 g sample.
Acid sludge What remains after treating petroleum oil with sulfuric acid for the removal of impurities. It is a black, viscous substance consisting of the acid remnants and the impuries removed.
Acid treating A refining process whereby raw petroleum products, such as gasoline, kerosene, and lubricating oil stocks, are treated with sulfuric acid to enhance their color, odor, and other properties
Acidity In lubricants, acidity indicates the presence of acid-type components whose concentration is generally defined in terms of total acid number. The components vary and may or may not alter the behavior of the lubricant.
ACS American Chemical Society
Actuator A converter of fluid energy into mechanical motion.
Additive A chemical substance applied to a petroleum product to confer or enhance certain qualities. Common petroleum product additives are: antifoam agent, anti-wear additive, corrosion inhibitor, demulsifier, detergent, dispersant, emulsifier, EP additive, oiliness agent, oxidation inhibitor, pour point depressant, rust inhibitor, tackiness agent, viscosity index (VI.) improver.
Additive level Equal to the total percentage of all additives in an oil. (Expressed in % of mass (weight) or % of volume)
Additive stability The ability of additives in the fluid to maintain their performance at all times.
Adhesion Lubricant property which causes it to cling or attach to solid surfaces.
Adhesive wear Sometimes referred to as galling, scuffing, scoring, or seizing. Occurs when sliding surfaces make contact, causing particles to be detached from one surface and adhered to the other.
Adsorbent filter A filter medium designed to retain soluble and insoluble impurities through molecular adhesion
Adsorption Adhesion of gas, liquid, or dissolved substance molecules to a solid surface, leading to high concentrations of the molecules there; e.g. the plating out of an anti-wear additive on metal surfaces.
Adsorptive filtration The pull towards and holding of particles in, a filter medium by electrostatic forces, or by molecular attraction between the molecules and the medium.
Aeration The state of gas being suspended in a liquid such as a lubricant or hydraulic fluid.
AFNOR Association Francaise de Normalisation
AFTP Association Francaise des Techniciens du Pétrole
Agglomeration A system's potential for particle attraction and adhesion.
AGMA Abbreviation for "American Gear Manufacturers Associations," a group serving the gear business.
AGMA lubricant numbers AGMA specification relating to gear lubricants. The viscosity ranges of the AGMA numbers (or grades) comply to the International Standards Organization (ISO) viscosity classification system (see ISO viscosity classification system).
AHEM Association of Hydraulic Equipment Manufacturers (UK)
Air Bleeder A device used to remove air from a hydraulic fluid line.
Air Breather A device which permits air movement between atmosphere and the component
Air entrainment The applying of air in the form of bubbles as a dispersed phase in a bulk liquid. Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to environmental changes. The presence of entrained air is usually apparent by the appearance of the liquid (i.e., bubbly, opaque, etc.) while dissolved air can only be ascertained by analysts.
Air motor A device used to convert compressed gas into mechanical force and motion. Normally utilized to provide rotary mechanical motion.
Air, Compressed Air at a greater pressure than atmospheric pressure.
Air, free Air at current atmospheric temperature, pressure, relative humidity, and density.
Air/Oil Systems A lubrication system in which tiny measured quantities of oil are applied into an air/oil mixing device which is connected to a lube line ending at a bearing, or other lubrication point. The air velocity conveys the oil along the interior walls of the lube line to where it is applied. These systems provide positive air pressure within the bearing housing, thereby eliminating the contaminants from entering, providing a cooling air flow to the bearing, as well as performing the lubrication function by constantly applying oil.
Air-Gap solenoid A solenoid that is sealed to prevent leakage of the liquid into the plunger cavity
Alkali A substance having basic (as opposed to acidic) properties. Alkaline materials are utilized primarily to neutralize acids: preventing corrosive wear in devices like internal combustion engines.
Almen EP lubricant tester A journal bearing machine used to check the load-carrying capacity or Extreme Pressure properties (EP) of gear lubricants.
ALTOW Alternate Temperature Operating Window, defined by fluids ability to meet OEM start-up and minimum viscosity requirements, see NFPA recommended practice T2.13.13-2002.
AMA Automobiles Manufacturers Association; American Management Association
Ambient temperature Atmospheric temperature around a process, (not the operating temperature of the process itself).
amp Abbreviation for ampere
Analytical ferrography The magnetic removal and analysis of wear debris from a fluid sample. Provides excellent means for analysis of composite wear particulates.
Anhydrous Lacking water
Aniline point The minimum temperature required for complete miscibility of equal volumes of aniline and the sample under test ASTM Method D611. A product of high aniline point will be low in aromatics and naphthenes and, therefore, high in paraffins. Aniline point is often specified for spray oils, cleaning solvents, and thinners, where effectiveness depends upon aromatic content. In conjunction with API gravity, the aniline point may be used to calculate the net heat of combustion for aviation fuels.
ANSI American National Standards Institute
Anti-foam agent One of two types of additives used to decrease foaming in petroleum products. In this case, silicone oil is used to break up large surface bubbles while various other kinds of polymers lower the amount of small bubbles within the oil.
Anti-friction bearing A rolling contact type bearing whose movement is supported or guided by means of a ball or roller elements. This does not eliminate friction.
Anti-oxidants Designed to prolong the induction period of a base oil in the presence of oxidizing conditions and catalyst metals at high temperatures. The additive is consumed and degradation products increase not only with increasing and sustained temperature, but also with increases in mechanical agitation or turbulence and contamination
Antistatic additive An additive used to enhance the conductivity of a hydrocarbon fuel to speed up the dissipation of electrostatic charges during high-speed distribution, thereby lowering fire/explosion hazard.
Antiwear additives Used to improve the service life of tribological elements functioning in the boundary lubrication regime. Anti-wear compounds (for example, ZDDP and TCP) start breaking down at 90 degrees to 100 degrees C or even lower if water (25 to 50 ppm) is added.
AO Anti-Oxidant
APE Association of Petroleum Engineers (USA)
API (American Petroleum Institute) A trade organization of virtually all aspects of the petroleum industry, including the producers, refiners, marketers, and transporters, designed to maximize advancement of the petroleum industry by conducting research, gathering and disseminating information, and maintaining cooperation between government and the industry on all matters of mutual interest.
API engine service categories Also called SAE or API/SAE categories, set of gasoline and diesel engine oil quality levels established jointly by API, SAE, and ASTM. Formerly called API Engine Service Classifications.
API gravity A gravity scale established by the American Petroleum Institute and in general use in the petroleum industry. The unit used to represent this quantity is referred to as "the A.P.I. degree."
Apparent viscosity The ratio of shear stress to rate of shear of a non-Newtonian fluid such as lubricating grease, or a multi-grade oil, calculated from Poiseuille's equation and measured in poises. The apparent viscosity changes with changing rates of shear and temperature and must, therefore, be reported as the value at a given shear rate and temperature (ASTM Method D 1092).
APR Association of Petroleum Rerefiners (USA)
Aromatic Defined by the existence of a benzene ring.
ARP Aeronautical Recommended Practice
Ash Determined by burning the oil, it is the amount of inorganic material in lubricating oil. It is expressed as a percentage by weight
ASLE American Society of Lubrication Engineers. Now known as the Society of Tribologist and Lubrication Engineers (STLE).
ASME American Society of Mechanical Engineers
Asperities Microscopic projections on metal surfaces resulting from normal surface-finishing processes. Opposing asperities in sliding or rolling applications create friction, and can lead to metal welding and scoring. Ideally, the lubricating film between the two surfaces should be thicker than the combined height of the opposing asperities.
ASTM American Society for Testing Materials (USA), an organization for establishing standards for materials and test methods.
ATC Additives Technical Committee
ATF Automatic Transmission Fluid
ATIEL Association Technique de I'Industrie Européenne des Lubrifiants
atm Abbreviation for atmosphere.
Atomic absorption spectroscopy Measures the radiation absorbed by chemically unbound atoms by analyzing the transmitted energy relative to the incident energy at each frequency. The procedure consists of diluting the fluid sample with methyl isobutyl ketone (MIBK) and directly aspirating the solution. The actual process of atomization involves reducing the solution to a spray form, dissolving it, and finally vaporizing it. The vaporization of the metal elements depends upon their time in the flame, the flame temperature, and the make-up of the flame gas. The spectrum occurs because atoms in the vapor state can absorb radiation at certain well-defined characteristic wave lengths. The wave length bands absorbed are very narrow and differ for each element. Element concentration can be ascertained from this since the absorption of radiant energy by electronic transitions from ground to excited state is essentially an absolute measure of the number of atoms in the flame.
Atomization The conversion of a liquid into a spray form of very fine droplets.
ATSF Association Technique de la Sidérurgie Francaise
Automatic Transmission Fluid (ATF) Fluid used for automatic, hydraulic transmissions in motor vehicles.
Axial-load bearing A bearing whereby the load acts in the direction of the axis of rotation.
B Back to top
Babbitt A soft, white, non-ferrous alloy used in the construction of bearings. The material is composed primarily of copper, antimony, tin and lead.
Background contamination The sum of the non-essential elements that are introduced in the process of obtaining, storing, moving, transferring and analyzing a fluid sample.
Bacteria Quick-growing, microorganisms often the size of only a single cell.
Bactericide Additive applied to water-mixed cutting fluids to hinder the growth of bacteria in order to prevent the odors given off by them.
Baffle A device used to prevent the direct flow of a fluid or impingement on a surface.
BAM British Air Ministry
Barrel A unit of liquid volume applied to petroleum oils. A barrel is equal to 42 U.S. gallons or approximately 35 Imperial gallons.
Base A substance used to neutralize acids. Typically a basic oil additive containing colloidally dispersed metal carbonate is used to reduce corrosive wear.
Base number Quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide, necessary to neutralize all basic elements present in a 1 g of sample
Base Oil A base stock or blend of stocks utilized in an API-licensed engine oil.
Base stock The base fluid, generally a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce a desired finished lubricant.
bbl Barrel (usually 42 gallons)
Bearing A support or guide used to determine where a moving part such as a shaft or axle is positioned in relation to the other parts of a device.
Bellows seal A type of mechanical seal utilizing bellows to allow for secondary sealing and spring-type loading.
Bernouilli's theory Principle stating that if no work is done on or by a flowing, frictionless liquid, its energy, due to pressure and velocity, remains constant at all points along the streamline.
Beta Rating The process of comparing filter performance by efficiency. This is done using the Multi-Pass Test which counts the number of particles of a given size before and after fluid flows through a filter.
Beta-Ratio The ratio of the number of particles greater than a given size in the influent fluid to the number of particles greater than the same size in the effluent fluid, under specified test conditions (see "Multi-Pass Test").
Bevel Gear A straight-toothed gear with the teeth cut on sloping faces and the gear shafts at an angle (normally a right angle)
BF Brookfield, as in Brookfield Viscosity as measured by a Brookfield viscometer
BFO Bunker Fuel Oil
bhp Brake Horsepower
bhp-h Brake Horsepower Hours
BHRA British Hydromechanics Research Association
BIA Boating Industry Association, now National Marine Manufacturers Association (NMMA)
BICERI British Internal Combustion Engine Research Institute
Biocides Additive designed to prevent microorganism growth in liquids
Biodegradation The chemical breakdown of materials by living organisms in the environment. The process depends on certain microorganisms, such as bacteria, yeast, and fungi, which are able to break down certain molecules for sustenance.
Bitumen Also known as tar or asphalt, bitumen is the by-product of the vacuum distillation of crude petroleum.
Black oils Lubricants containing asphaltic elements. This affects the lubricant's properties by allowing it extra adhesiveness, making it more applicable for lubricating open gears and steel cables.
BLAP British Lubricants Advisory Panel (See LETAP)
BLC Bulk Liquid Container
Bleeding Isolating some of the liquid phase from a grease
Blending The method of mixing lubricants or components to obtain a desired physical and/or chemical characteristic (see compounding)
BLF British Lubricant Federation
blowby Leakage of combustion gases between a piston and the cylinder wall into the crankcase in an automobile
Blow-by Term used when unburned fuel and combustion gases pass the piston rings of internal combustion engines, consequently diluting the fuel and contaminating the crankcase oil.
bmep Brake Mean Effective Pressure
BN Base Number (ASTM D 2896)
BNP Bureau de Normalisation des Pétroles
BOFT Bearing Oil Film Thickness
Boiling point The temperature at which a substance begins being converted from liquid to vapor by bubbles forming within. It varies with pressure.
Boiling range Used for mixtures of substances, represents the temperature interval between the initial and final boiling points.
Bomb Oxidation A test for oxidation stability of a product achieved by sealing it in a closed container with oxygen under pressure. By monitoring the drop in pressure of the oxygen, the amount of oxidation can be ascertained.
Boundary lubrication A form of lubrication between two rubbing surfaces without development of a full-fluid lubricating film. Additives which provide for a stronger oil film increase the effectiveness of boundary lubrication by preventing excessive friction. There are varying degrees of boundary lubrication, depending on the harshness of the service.
Boyle's law States that, at constant temperature, the absolute pressure of a fixed mass of gas varies inversely as the volume.
BPICA Bureau Permanent International des Constructeurs Automobiles
BPT Borderline Pumping Temperature
Breakdown maintenance Maintenance necessary after a machine has failed to resume operating.
Bridging A condition of filter element loading in whereby a contaminant spans the space between adjacent sections of a filter element, thus inhibiting a portion of the useful filtration.
Bright stock A heavy residual lubricant stock with a low pour point, used in finished blends to achieve good bearing film strength, prevent scuffing, and reduce oil consumption. It is distinguished by its viscosity, SUS at 210°F or cSt at 100°C.
Brinelling Permanent disfigurement of the bearing surfaces where the rollers (or balls) make contact with the races. Results from excessive load or impact on stationary bearings. It is a form of mechanical damage in which metal is displaced or upset without attrition.
Brookfield viscosity Viscosity in cP determined by Brookfield viscometer, which measures the torque necessary to rotate a spindle at constant speed in oil of a given temperature. Basis for ASTM Method D 2983; utilized when measuring low temperature viscosity of lubricants.
BS Bright Stock
BSFC Brake Specific Fuel Consumption
BSI British Standards Institution
BTC British Technical Council of the Motor and Petroleum Industries
BTU British Thermal Unit. The amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit.
Bubble point The differential gas pressure at which the first steady stream of gas bubbles is emitted from a wetted filter element under specified test conditions.
Built-in-dirt Elements passed into the effluent stream made up of foreign material that is incorporated into the filter medium.
Bulk modulus (of elasticity) A ratio comparing the amount of normal stress needed to change the volume. A value used to determine the compressibility of a fluid. Data for petroleum products can be found in the International Critical Tables.
Burst pressure rating The maximum inside-out differential pressure that can be exercised on a filter element before outward structural damage or filter-medium failure occurs.
Bushing A short, connector, threaded externally, with a smaller sized internal thread.
BWL Bearing Weight Loss
Bypass Filtration A system of filtration in which only part of the total flow of a circulating fluid system travels through a filter at any time or in which a filter having its own circulating pump functions in parallel to the primary flow.
Bypass valve (Relief valve) A valve mechanism that maintains fluid system flow when a certain differential pressure across the filter element is transcended; the valve allows all or part of the flow to bypass the filter element.
C Back to top
C or cent. Centigrade, standard international unit of temperature measurement
CAFE Corporate Average Fuel Economy
Cams Eccentric shafts common in most internal combustion engines and utilized when opening and closing valves.
Capacity The maximum amount of contaminants a filter will hold before an excessive pressure drop occurs. Filters generally have a bypass valve in case this happens.
Capillarity Property of a solid-liquid system exhibited by the tendency of the liquid, when in contact with the solid, to rise above or fall below the level of the surrounding liquid. This phenomenon can be witnessed in a smallbore (capillary) tube.
Capillary Viscometer A type of viscometer in which the oil flows through a capillary tube.
CARB California Air Resources Board
Carbon A non-metallic element - No. 6 in the periodic table. Diamonds and graphite are pure forms of carbon. Carbon is a basic component of all organic compounds. It also combines well; forming many different inorganic substances; i.e., carbon dioxide, limestone, etc.
Carbon (deposit) Solid black residue that occurs in piston grooves. Can potentially interfere with piston ring movement causing wear and/or loss of power.
Carbon residue Coked material leftover when an oil has been subjected to high temperatures under controlled conditions.
Carbon Type The distinction between paraffinic, naphthenic, and aromatic molecules. In the case of lubricant base stocks, the predominant type present.
Carcinogen A cancer-causing substance. Some petroleum products are considered potential carcinogens by OSHA criteria. Suppliers are required to note this fact on package labels and Material Safety Data Sheets.
Cartridge seal A totally self-contained assembly containing seal, gland, sleeve, mating ring, etc., usually needing no installation measurement.
Case drain filter A filter located in a line conveying fluid from a pump or motor housing to reservoir.
Case drain line A line transferring fluid from a component housing to the reservoir.
CAS-Nr Chemical Abstracts Number
CAT Caterpillar (Tractor Company)
Catalyst A substance that originates or speeds up the rate of a chemical reaction, without being itself consumed.
Catalytic converter An essential part of vehicle emission control systems since 1975. Oxidizing converters remove hydrocarbons and carbon monoxide (CO) from exhaust gases, while reducing converters control nitrogen oxide (NOx) emissions. Both use noble metal (platinum, palladium or rhodium) catalysts that can be "poisoned" by lead compounds in the fuel or lubricant.
Catastrophic failure Abrupt and unexpected failure of a machine resulting in substantial cost and downtime.
Caustic An extremely alkaline material such as sodium hydroxide.
Cavitation The formation of an air or vapor pocket (or bubble) caused by lowering of pressure in a liquid, often resulting from a solid body, such as a propeller or piston, traveling through the liquid; also, the pitting or wearing away of a solid surface as a result of the collapse of a vapor bubble. Cavitation may occur in a hydraulic system as a result of low fluid levels that bring air into the system, creating tiny bubbles that expand explosively at the pump outlet, causing metal erosion and eventual pump destruction.
Cavitation erosion Name given to a material-damaging process which occurs as a result of vaporous cavitation. "Cavitation" pertains to the occurrence or formation of gas- or vapor- filled pockets in flowing liquids caused by the hydrodynamic generation of low pressure (below atmospheric pressure). This damage results from the hammering action when cavitation bubbles implode in the flow stream. Ultra-high pressures resulting from the collapse of the vapor bubbles produce deformation, material failure and, in the end, erosion of the surfaces.
CCS Cold Cranking Simulator
CEC Coordinating European Council
CEC/SB Conseil Européen de Coordination/Société Belge (member CEC)
CEE Conseil Européen Economique
CEFIC European Chemical Industry Council
Cellulose Media A filter material created from plant fibers. Because cellulose is a natural material, its fibers are rough in texture and vary in size and shape. In contrast to synthetic media, these characteristics result in a higher restriction to the flow of fluids.
CEN Conseil Européen de Normalisation
Centipoise (cp) A unit used to measure absolute viscosity. 1 centipoise = 0.01 poise.
Centistoke (cst) A unit used to measure kinematic viscosity. 1 centistoke = 0.01 stoke.
Centralized lubrication A system of lubrication in which a measured amount of lubricant or lubricants for the bearing surfaces of a machine or group of machines all come from a central location.
Centrifugal separator A separator that removes immiscible fluid and solid contaminants that have a different specific gravity than the fluid being purified by speeding up the fluid mechanically in a circular path and using the radial acceleration component to isolate contaminants.
CETIM Centre Technique ds Industries Mécaniques (France)
CETOP Comité Européen des Transmission Oléohydrauliques et Pneumatiques
CFPP Cold Filter Plugging Point
Channeling The phenomenon observed among gear lubricants and greases when they thicken due to cold weather or other causes, to such an extreme that a groove forms through which the part to be lubricated moves, no longer coming in full contact with the lubricant. A term used in percolation filtration; may be defined as: a preponderance of flow through certain portions of the clay bed.
Chemical stability The tendency of a substance or mixture to resist chemical change.
Chip control (grit control, last-chance) filter A filter intended to stop only large particles from entering a component directly downstream.
Chlorinated wax Specific solid hydrocarbons treated with chlorine gas to form straight-chain hydrocarbons with a relatively high chlorine component. Chlorinated waxes are used mainly as polyvinyl chloride plasticizers, extreme-pressure additives for lubricants, and formulation components for many cutting fluids
Chromatography An analytical technique whereby a complex substance is adsorbed on a solid or liquid substrate and progressively eluted by a flow of a substance (the eluant) in which the elements of the substance under investigation are differentially soluble. The eluant can be a liquid or a gas. When the substrate is filter paper and the eluant a liquid, a chromatogram of colored bands is developed by use of indicators. For gas chromatography, electronic detectors are normally used to represent passage of the several components from the system.
CIA Chemical Industries Association (part of CEFIC)
CIGRE Conference Internationale des Grands Réseaux Electriques à Haute Tension
CIMAC International Council on Combustion Engines
Circulating Header System A lubrication system which has isolated lube zones wherein the lube pump runs nonstop circulating oil through the header, a return filter and back to tank during the idle period. When lubrication is necessary, a normal open solenoid valve in the return loop is actuated, causing pump pressure to build. The zone valves are then sequentially opened to distribute lubricant to the individual zones. Oil dispensed to the friction points is not reused, therefore, the system eventually terminates.
Circulating lubrication System of lubrication in which the lubricant, after having passed through a bearing or group of bearings, is recirculated by means of a pump.
Circulating oil A lubrication system wherein the oil pump runs continuously and circulates oil to the friction points on a continuous basis. The oil is drained back to tank, filtered, cooled as required and reused.
Circulating System Lubricating system where oil is recirculated from a central sump to the parts where lubrication is necessary and then returned to the sump.
Clay filtration A refining process using fuller's earth (activated clay), bauxite or other mineral to remove minute solids from lubricating oil, as well as take out traces of water, acids, and polar compounds.
CLCA Comité de Liaison de la Construction de l'Automobile
Clean room A facility or enclosure in which air content and other conditions (such as temperature, humidity, and pressure) are controlled and maintained at a specific level.
Cleanable A filter element which, when loaded, can be returned again to an acceptable percentage of its original level of dirt capacity.
Cleanliness level (CL) A measure of a substance's relative lack of contaminants.
Clearance bearing A type of journal bearing in which the radius of the bearing surface is larger than the radius of the journal surface.
Cleveland Open Cup (COC) A flash point test in which the surface of the sample is completely open to the atmosphere, therefore making it relatively insensitive to small traces of volatile contaminants.
Cloud point The temperature at which waxy crystals in an oil or fuel form a cloudy appearance.
CLR Committee on Lubricant Research (USA)
CMA Chemical Manufacturers Association (USA)
Coalescor A separator that divides a mixture or emulsion of two immiscible liquids using the interfacial tension between the two liquids and the difference in wetting of the two liquids on a particular porous medium.
COC Cleveland Open Cup - Flash Point
Coefficient of friction Number achieved by dividing the friction force resisting motion between two bodies by the normal force pushing the two together.
Cohesion Property of a substance that allows it to withstand being pulled apart mechanically.
Coking The undesirable accumulation of carbon deposits in the internal combustion engine or in a refinery plant. Also, the process of distilling a petroleum product to dryness
Cold cranking simulator (CCS) Intermediate shear rate viscometer that predicts the ability of an oil to permit a satisfactory cranking speed to be created in a cold engine.
Collapse An inward structural failure of a filter element which can occur due to abnormally high pressure drop (differential pressure) or flow resistance.
Collapse pressure The minimum differential pressure that an element is designed to withstand without permanently being deformed.
Compound (1) Chemically speaking, a unique substance formed by the combination of two or more elements in definite proportions by weight and possessing physical and chemical properties different from those of the lone elements. (2) In petroleum processing, generally refers to fatty oils and other materials foreign to petroleum applied to lubricants to impart special properties.
Compounded oil Petroleum oil containing other added chemical substances.
Compounding The adding of fatty oils and similar substances to lubricants to impart distinct properties. Lubricating oils with added compounds are known as compounded oils.
Compressibility A compound that enhances some property of, or bestows some new property to, the base fluid. In some hydraulic fluid formulations, the additive volume may be as much as 20 percent of the final composition. The more important types of additives include anti-oxidants, anti-wear additives, corrosion inhibitors, viscosity index improvers, and foam suppressants.
Compression ratio In an internal combustion engine, the ratio of the volume of combustion space at bottom dead center to that at top dead center.
Compressor Name given to a device which converts mechanical force and motion into pneumatic fluid power.
CONCAWE Conservation of Clean Air and Water (Europe)
Contaminant Any foreign or unwanted substance that can negatively effect system operation, life or reliability.
Contaminant (Dirt, ACFTD) capacity The weight of a specific artificial contaminant that must be applied to the influent to create a given differential pressure across a filter at specified conditions. Used as an indicator of relative service life.
Contaminant Failure Any loss of performance due to the presence of contamination.
Contaminant lock A particle or fiber-induced jam caused by solid contaminants.
Contamination control A broad subject which applies to all types of material systems (including both biological and engineering). It is concerned with planning, organizing, managing, and implementing all activities required to determine, achieve and maintain a specified contamination level.
Coolant A fluid used to remove heat. See Cutting fluid.
Copper strip corrosion The gradual eating away of copper surfaces as the result of oxidation or other chemical action. Caused by acids or other corrosive agents.
CORC Co-operative Octane Requirement Committee (USA)
Corrosion The decay and loss of a metal caused by a chemical reaction between the metal and its environment. It is a transformation process in which the metal passes from its elemental form to a combined (or compound) state.
Corrosion inhibitor Additive used to protect lubricated metal surfaces from chemical changes by water or other contaminants. There are several types of corrosion inhibitors. Polar compounds wet the metal surface preferentially, protecting it with a film of oil. Other compounds may absorb water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Another type of corrosion inhibitor combines chemically with the metal to present a non-reactive surface.
COSHH Control of Substances Hazardous to Health Regulations
Coupling A straight connector for fluid lines.
Coupling, quick disconnect A coupling which can rapidly join or separate lines.
Cracking The process whereby large molecules are broken down by applying heat and pressure, forming smaller molecules.
Crankcase oil Lubricant used in internal combustion engine crankcases.
CRC Coordinating Research Council (USA)
Cryogenics Branch of physics relating to the production and effects of very low temperatures.
CSB Chemischer Sauerstoffbedarf
CSMA Chemical Specialties Manufacturing Association (USA)
CTLM Comité Technique Lubrifiant Moteurs (of the GFC)
CUNA Commissione Tecnica di Unificazione nel l'Autoveicolo (Italian member CEC)
CVT Continuously Variable Transmission
Cylinder A device which converts fluid power into linear mechanical force and motion. Generally consists of a moveable element such as a piston and piston rod, plunger rod, plunger, or ram, that operates within a cylindrical bore.
D Back to top
DASMIN German Quality Accreditation Institution
dB Decibel
DDI Detergent-Dispersant-Inhibitor
Deaerator Separator that removes air from the system fluid by the use of bubble dynamics.
DEF Procurement executive Ministry of Defence
Degas Removing air from a liquid, generally by ultrasonic and/or vacuum methods.
Degradation Increasing failure of a machine or lubricant.
Dehydrator A separator that removes water from the system fluid.
Delamination wear A complex wear process whereby a machine's surface is peeled away or otherwise removed by forces of another surface acting upon it in a sliding motion.
Demulsibility Ability of a fluid that is insoluble in water to separate from water with which it may be combined in the form of an emulsion.
Demulsifier An additive used to promote oil-water separation in lubricants that are subject to water or steam
Density The mass of a unit volume of a substance. Its numerical value depends on the units used.
Deposits Name given to oil-insoluble materials that result from oxidation and breakdown of lube oil and contamination from outside sources and engine blow-by. Examples are sludge, varnish, lacquer and carbon.
Depth filter A filter medium that restrains contaminants mainly within tortuous passages.
Dermatitis Inflammation of the skin. Can be caused by repeated contact with petroleum products.
Desorption Opposite of absorption or adsorption. In filtration, it has to do with the downstream release of particles previously retained by the filter.
Detergent In lubrication, either an additive or a compounded lubricant having the ability to keep insoluble matter in suspension, thereby prohibiting deposition where it would be harmful. Also may be used to redisperse deposits already formed.
Detergent oil Lubricating oil possessing special sludge-dispersing properties usually conferred on the oil by the addition of additives. Detergent oils retain sludge particles in suspension and thus promote cleanliness especially in internal-combustion engines. However detergent oils do not contain “detergents” such as those used for cleaning of laundry or dishes. Also detergent oils do not clean already “dirty” engines, but rather keep in suspension the sludge that petroleum oil forms so that the engine remains cleaner for longer period. The formed sludge particles are either filtered out by Oil Filters or drained out when oil is changed.
Dewaxing Removal of wax from a base oil to reduce the pour point.
DGMK Deutsche Gesellschaft für Mineralölwissenschaft und Kohlechemie
DI Detergent-Inhibitor
Dielectric Strength A measure of an insulating material's ability to endure electric stress (voltage) without failure. Fluids with high dielectric strength (usually expressed in volts or kilovolts) are good electrical insulators. (ASTM Designation D 877.)
Differential pressure indicator An indicator used to indicate the difference in pressure between any two points of a system or a component.
DIN Deutsches Institut für Normung (German Standards)
Dirt capacity (dust capacity) (contaminant capacity) The weight of a specified artificial contaminant which must be added to the influent to create a given differential pressure across a filter at specified conditions. Used to indicate of relative service life.
Dispersant Used interchangeably with detergent, denotes an additive, usually nonmetallic ("ashless"), which keeps fine particles of insoluble materials in a homogeneous solution. Hence, particles are not permitted to settle out and accumulate.
Disposable A filter element expected to be discarded and replaced after one service cycle.
Dissolved air Air which is dispersed in a fluid creating a mixture.
Dissolved gases Gases that enter into solution with a fluid and are neither free nor entrained gases.
Dissolved water Water which is dispersed in the fluid to form a mixture.
Distillation method (ASTM D-95) Method involving distilling the fluid sample in the presence of a solvent that is miscible in the sample but immiscible in water. The water distilled from the fluid is condensed and segregated in a specially-designed receiving tube or tray graduated to directly indicate the volume of water distilled.
DKA Deutscher Koordinierungsausschuss im Coordinating European Council (member CEC)
DNA Deutscher Normenausschuß
DOCP Dispersant Olefin Copolymer (VI Improver)
Double seal Two mechanical seals designed to allow a liquid or gas barrier fluid between the seals mounted back-to-back or face-to-face.
DPMA Dispersant Polymethacrylate (VI Improver)
Drag Resistance to movement due to oil viscosity.
Drum Container with a capacity of 55 U.S. gallons.
Dry lubrication Occurs when moving surfaces have no liquid lubricant between them.
Dry sump An engine design where oil is not retained in a pan below the crankshaft thus permitting splash lubrication. There may be a remote sump from which oil is recirculated, or there may be a total loss system.
Dual-Line system A positive displacement terminating (oil, or grease) lubrication system that employs two main lines supplied from a pump connected to a 4-way (reverser) valve. Pressure in one main line (while the other is open to tank) causes the measuring piston(s) in the dual-line valve(s) to stroke in one direction providing lubricant to one group of lube points. Switching the 4-way (reverser) valve directs pump flow to the second main line and opens the first main line to tank. This allows pressure to build in the second main line causing the dual-line valve(s) measuring piston(s) to stroke back to their original position applying lubricant to a second group of lube points. The system is a parallel type and each dual-line valves operates independently of another system.
Duplex filter Assembly of two filters with valving for selection of one or both filters.
Dynamic seal A seal that moves due to axial or radial movement of the device.
Dynamic viscosity Viscosity measured under force induced flow. Represented by the centipoise, cP.
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ECE Economic Commission for Europe
ECE-TD Economic Commission For Europe-Transport Division
ECETOC European Chemical Industry Ecology and Toxicology Centre
ECO Energy Conserving Oil
EEB European Environmental Bureau
EEC (CEE) European Economic Community (Conseil Européen Economique)
Effluent The fluid exiting a component.
EFTC Engine Fuels Technical Committee (of CEC)
EHD Elastohydrodynamic (lubrication)
ehp Effective Horsepower
EINECS European Inventory of Existing Chemical Substances
Elastohydrodynamic lubrication In rolling element bearings, the elastic deformation of the bearing (flattening) as it rolls, under load, in the bearing race. This momentary flattening enhances the hydrodynamic lubrication properties by changing point or line contact to surface-to-surface contact.
Elastomer A rubber or rubber-like material, both natural and synthetic, used to make a wide variety of products, such as seals and hoses. In oil seals, an elastomer's chemical composition factors into discovering its compatibility with a lubricant.
Electrical insulating oil A high-quality oxidation-resistant oil refined to give long service as a dielectric and coolant for electrical equipment, most commonly transformers. Must withstand the effects of extreme temperatures, electrical stress, air contact, which can lead to sludge formation and loss of insulation features. It must be kept dry, as water is detrimental to dielectric strength – the minimum voltage required to produce an electric arc through an oil sample, as measured by test method ASTM D 877.
Electrostatic separator A separator that removes contaminant from dielectric fluids by applying an electrical charge to the contaminant that is then drawn to a collection device of different electrical charge.
Element (Cartridge) Porous device that performs the actual process of filtration.
Emission spectrometer Functions on the premise that atoms of metallic and other elements emit light at specific wavelengths when they are excited in a flame, arc, or spark. Excited light is directed through an entrance slit in the spectrometer. This light penetrates the slit, falls on a grate, and is dispersed and reflected. The spectrometer is calibrated by a series of standard samples containing known amounts of the elements of interest. By exciting these standard samples, an analytical curve can be established which gives the relationship between the light intensity and its concentration in the fluid.
EMPA Eidgenössische Materialsprüfungs und Versuchsanstalt für Industrie
Emulsibility Property of a non-water-soluble fluid to develop an emulsion with water.
Emulsifier Additive used to promote formation of stable mixtures or emulsions, of oil and water. Common emulsifiers are: metallic soaps, certain animal and vegetable oils, and various polar compounds.
Emulsion Mixture of oil and water. Emulsions may be of two types: oil-in water (where water is the continuous phase) and water-in-oil (where water is the discontinuous phase).
End cap Ported or closed cover for the end of a filter element.
Engine deposits Hard or persistent buildup of sludge, varnish and carbonaceous residues due to blow-by of unburned and partially burned fuel, or the partial breakdown of the crankcase lubricant. Water from the condensation of combustion products, carbon, residues from fuel or lubricating oil additives, dust and metal particles also add to deposition.
Entrained air A mechanical mixture of air bubbles which tend to separate from the liquid phase.
Environmental contaminant Total of material and energy present in and around an operating system. This includes dust, air moisture, chemicals, and thermal energy.
EOLCS Engine Oil Licensing and Certification System (of API)
EOVC Engine Oil Viscosity Classification (of SAE)
EP Extreme Pressure (Additives)
EP (Extreme Pressure) lubricants Lubricants that bestow to rubbing surfaces the ability to carry greater loads than would be possible with ordinary lubricants without excessive wear or damage.
EP oil Lubricating oil designed to withstand extreme pressure (EP) operating conditions.
EPA Environmental Protection Agency (USA)
ERA Energy Regulatory Administration (USA)
Erosion The gradual removal of a machine surface by cavitation or by particle impingement at high velocities.
EUROPIA European Petroleum Industry Association
Externally pressurized seal A seal that has pressure acting on the seal parts from an external independent source.
Extreme pressure (EP) additive Lubricant additive that stops sliding metal surfaces from seizing under extreme pressure conditions. At the high local temperatures associated with metal-to-metal contact, an EP additive combines chemically with the metal to form a surface film that prevents the welding of opposing asperities, and the scoring that results which is destructive to sliding surfaces under high loads. Reactive compounds like sulfur, chlorine, or phosphorus are used to form these inorganic films.
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Face seal Device used to prevent leakage of fluids along rotating shafts. Sealing is accomplished by a stationary primary seal ring bearing against the face of a mating ring mounted on a shaft. Axial pressure maintains the contact between the seal ring and the mating ring.
False brinelling Although it is similar in appearance to brinelling, false brinelling is defined by attrition of the steel, and the load on the bearing is less than that necessary to produce the resulting impression. It is the result of a combination of mechanical and chemical action that is not completely understood: occurring when a small relative motion or vibration is accompanied by some loading, in the presence of oxygen.
Fat An animal or vegetable oil which will combine with an alkali to saponify to create a soap.
Fatigue chunks Relatively large three-dimensional particles exceeding 50 microns indicating severe wear of gear teeth.
Fatigue life Theoretical number of revolutions (or hours of operation) a bearing will last under a given constant load and speed before the first evidence of fatigue develops on one or more of the components.
Fatigue platelets Normal particles between 20 and 40 microns found in gear box and rolling element bearing oil samples observed by analytical ferrography. An increase in the size and quantity of these particles is a good indicator of excessive wear.
Fatigued A structural failure of the filter medium due to flexing caused by cyclic differential pressure.
Ferrography An analytical method of evaluating machine health by counting and examining ferrous wear particles suspended in the lubricant or hydraulic fluid.
Film strength Property of a lubricant that works to stop scuffing or scoring of metal parts.
Filter Any device or porous substance used as a strainer that cleans fluids by removing suspended particles
Filter Efficiency Way of expressing a filter's ability to trap and retain contaminants of a specified size.
Filter element The porous device which actually performs filtration.
Filter head End closure for the filter case or bowl that includes one or more ports.
Filter housing Ported enclosure that directs the flow of fluid through the filter element.
Filter life test Type of filter capacity test in which a clogging contaminant is added to the influent of a filter, under specified test conditions, to produce a given rise in pressure drop across the filter or until a specified reduction of flow is reached. Filter life can be expressed as test time needed to reach terminal conditions at a set contaminant addition rate.
Filter media, depth Porous materials which primarily retain contaminants within a tortuous path, performing the actual act of filtration.
Filter media, surface Porous materials which primarily retain contaminants on the influent face, performing the actual act of filtration.
Filtration Physical or mechanical process of removing insoluble particulate matter from a fluid, such as air or liquid, by passing it through a filter medium that will restrict the particulates.
Filtration (Beta) ratio Ratio of the number of particles greater than a given size in the influent fluid to the number of particles greater than the same size in the effluent fluid.
Fire point (Clevelend Open Cup) Temperature to which a combustible liquid must be heated so that the released vapor will burn continuously when ignited under specified conditions.
Fire-resistant fluid Lubricant designed to perform in high-temperature or hazardous hydraulic applications. Three common types of fire-resistant fluids are: (1) water-petroleum oil emulsions, in which the water prevents burning of the petroleum constituent; (2) water-glycol fluids; and (3) non-aqueous fluids with low heat of combustion, such as polyol esters, phosphate esters, silicones, and halogenated hydrocarbon-type fluids.
FISITA Fédération Internationale des Sociétés d'Ingenieurs et de Techniciens
FISST Fuel Injector Shear Stability Test
Flash point (Cleveland Open Cup) Temperature to which a combustible liquid must be heated to release sufficient vapor to form momentarily a flammable mixture with air when a small flame is applied under specified conditions. (ASTM Designation D 92.)
Floc Point The temperature at which wax or solids separate in an oil
Flow fatigue rating The ability of a filter element to withstand a structural failure of the filter medium due to flexing caused by cyclic differential pressure.
Flow rate The volume, mass, or weight of a fluid passing through any conductor per unit of time.
Flow, laminar A type of flow in which fluid moves in parallel lamina or layers.
Flow, turbulent A type of flow situation in which the fluid particles move randomly.
Flowmeter A device which displays either flow rate, total flow, or a combination.
Fluid compatibility The suitability of filtration medium and seal materials for use with the fluid involved.
Fluid opacity Concerns a fluid's ability to pass light.
Fluid power Energy manipulated through use of a pressurized fluid.
Flushing A fluid circulation technique used to remove contamination from the wetted surfaces of a fluid system.
FM Friction Modifier
Foam An agglomeration of gas bubbles separated from each other by a thin liquid film This phenomenon is observed persistently on the surface of liquids.
Foam inhibitor A substance introduced in to prevent the formation of foam and to accelerate the dissipation of any foam that may form.
Foaming A mixture of air and a petroleum product (e.g., lubricant, fuel oil) which can lower a product's effectiveness and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. It can be a result of excessive agitation, improper fluid levels, air leaks, cavitation, or contamination with water or other foreign materials. Foaming can be inhibited with an antifoam agent. The foaming characteristics of a lubricating oil can be determined by blowing air through a sample at a specified temperature and measuring the volume of foam, as described in test method ASTM D 892.
Force feed lubrication A type of lubrication whereby the lubricant is applied to the bearing surface under pressure.
Four Ball Tester This name is often used to describe either of two similar laboratory machines, the Four-Ball Wear Tester and the Four-Ball EP Tester. These machines are used to test a lubricant's anti-wear properties, frictional characteristics or load carrying capabilities. It derives its name from the four 1/2 inch steel balls used as test objects. Three of the balls are held together in a cup filled with lubricant while the fourth ball is rotated against them.
Free Water Water droplets or globules in the system fluid that collect at the bottom or top of the system fluid depending on the fluid's specific gravity.
Fretting Wear phenomena occurring between two surfaces with oscillatory relative motion of small amplitude.
Fretting corrosion Type of corrosion which can take place when two metals are held in contact and subjected to repeated small sliding, relative motions. Other names for this type of corrosion include wear oxidation, friction oxidation, chafing, and brinelling.
Friction Name given to the resisting force encountered at the common boundary between two bodies when, because of an external force, one body moves or tends to move relatively to the surface of the other.
FTC Federal Trade Commission (USA)
FTIR = Fourier Transform Infrared Spectroscopy A test which uses infrared light absorption to assess levels of soot, sulfates, oxidation, nitro-oxidation, glycol, fuel, and water contaminants in a substance.
ft-lbf Foot-pound-force (Use for Work)
FTM U.S. Federal Test Method
FTP U.S. Federal Test Procedure
Full flow filter A filter that can filter all influent flow.
Full-flow filtration Filtration system in which the total flow of a circulating fluid system moves through a filter.
Full-fluid-film lubrication When a continuous lubricating film sufficient to completely separate two surfaces is present, as distinct from boundary lubrication. Full-fluid-film lubrication is normally hydrodynamic lubrication, whereby the oil adheres to the moving part and is drawn into the area between the sliding surfaces, where it forms pressure.
FZG test A German gear wear test for evaluating EP properties (Forschungsstelle für Zahnräder und Getriebebau).
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Gage An instrument or device for measuring, indicating or comparing a physical characteristic.
Gal Gallon(s)
Galling A form of wear in which seizing or tearing of the gear or bearing surface results.
Gear A machine part designed to transmit motion and force by means of successively engaging projections, called teeth. The smaller gear of a pair is called the pinion; the larger, the gear. When the pinion is on the driving shaft, the gear set acts as a speed reducer; when the gear drives, the set acts as a speed multiplier. The basic gear type is the spur gear, or straight-tooth gear, with teeth cut parallel to the gear axis. Spur gears transmit power in applications utilizing parallel shafts. In this type of gear, the teeth mesh along their full length, creating a sudden shift in load from one tooth to the next, with consequent noise and vibration. This problem is overcome by the helical gear, which has teeth cut at an angle to the center of rotation, so that the load is transferred progressively along the length of the tooth from one edge of the gear to the other. When the shafts are not parallel, the most common gear type used is the bevel gear, with teeth cut on a sloping gear face, rather than parallel to the shaft. The spiral bevel gear has teeth cut at an angle to the plane of rotation, which, like the helical gear, reduces vibration and noise. A hypoid gear resembles a spiral bevel gear, except that the pinion is offset so that its axis does not intersect the gear axis; it is widely used in automobiles between the engine driveshaft and the rear axle. Offset of the axes of hypoid gears introduces additional sliding between the teeth, which, when combined with high loads, requires a high-quality EP oil. A worm gear consists of a spirally grooved screw moving against a tooth wheel; in this type of gear, where the load is transmitted across sliding, rather than rolling surfaces, compounded oils or EP oils are usually necessary to maintain effective lubrication.
Gear oil A high-quality oil noted for good oxidation stability, load-carrying capacity, rust protection, and resistance to foaming, for service in gear housings and enclosed chain drives. Specially formulated industrial EP gear oils are used where highly loaded gear sets or excessive sliding action (as in worm gears) is encountered.
Gearbox (gear housing) A container for gear sets that transmit power from one rotating shaft to another. A gear box is designed to precisely control gear and shaft alignment, provide a container for the gear oil, and to protect the gears and lubricant from water, dust, and other environmental contaminants. Gear boxes are utilized in a wide range of industrial, automotive, and home machinery. Not all gears are enclosed in gear boxes however: some gears are open to the environment and are lubricated by highly adhesive greases.
GO Gear Oil
GOST Gosudarstvyeny Standart (USSR) - Russian Standard
GPM Gallons per minute
Graphite A crystalline form of carbon having a laminar structure commonly used as a lubricant. It may be natural or artificially made.
Gravimetric analysis A method of examination whereby the dry weight of contaminant per unit volume of fluid can be ascertained, indicating the degree of contamination in terms of milligrams per liter.
Gravity See Specific Gravity; API Gravity.
Grease A lubricant consisting of an oil or oils thickened with a soap, several soaps, or other thickener to a semisolid or solid consistency.
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Hardness The ability of a substance to resist surface abrasion
HC Hydrocracked Oil
HD Heavy Duty
HDEOCP Heavy Duty Engine Oil Classification Panel
Heat exchanger A device used to transfer heat through a conducting wall between one fluid to another.
HF-0 Parker Denison Hydraulic Oil Specification
HG HM grade oils with improved stick/slip performance, ISO 11158 standard only, not included in ASTM 6158, ISO viscosity grade HM + low speed stick/slip performance.
HH Hydraulic fluid classification according to ASTM D 6158, mineral oil with no additives for very light duty
HL Hydraulic fluid classification according to ASTM D 6158, mineral oil with additives for improved rust protection and oxidation stability
HM Hydraulic fluid classification according to ASTM D 6158, mineral oil with additives for improved rust protection, oxidation stability, and antiwear.
Housing A ported enclosure which regulates flow of fluid through the filter element.
HR HL grade with high VI for wide temp. operating range, ISO 11158 standard only, not included in ASTM 6158, ISO viscosity grade HL + VI>130, shear stability.
HTHS High Temperature High Shear (viscosity)
HV Hydraulic fluid classification according to ASTM D 6158, mineral oil with additives for improved rust protection, oxidation stability, antiwear, and viscosity index. VI must be greater than 140.
HVI High Viscosity Index
Hydraulic Fluid Fluid serving as the power transmission medium in a hydraulic system. The most commonly used are petroleum oils, synthetic Lubricants, oil-water emulsions, and water-glycol mixtures. The essential functions of a premium hydraulic fluid are proper viscosity, high viscosity index, anti-wear protection (if needed), good oxidation stability, adequate pour point, good demulsibility, rust inhibition, resistance to foaming, and compatibility with seal materials. Anti-wear oils are commonly used in compact, high-pressure, and capacity pumps that require extra lubrication protection.
Hydraulic motor A device used to convert hydraulic fluid power into mechanical force and motion by the transference of flow under pressure. Frequently provides rotary mechanical motion.
Hydraulic Oil An oil specially designed to serve as either the specific gravity or the API gravity of a liquid.
Hydraulic pump A device which transforms mechanical force and motion into hydraulic fluid power by means of producing flow.
Hydraulic system A system designed to convey power through a liquid medium, allowing multiplication of force according to Pascal's law, which stated that “a pressure exerted on a confined liquid is transmitted undiminished in all directions and acts with equal force on all equal areas.” Hydraulic systems have six basic components: (1) a reservoir to contain the fluid supply; (2) a fluid to transmit the power; (3) a pump to move the fluid; (4) a valve to regulate pressure; (5) a directional valve to control the flow, and (6) a working component – such as a cylinder and piston or a shaft rotated by pressurized fluid – to turn hydraulic power into mechanical motion. Hydraulic systems offer several advantages over mechanical systems: They eliminate complicated mechanisms such as cams, gears, and levers; are less subject to wear; are usually more easily adjusted for control of speed and force; are easily adaptable to both rotary and liner transmission of power; and can transmit power over long distances and in any direction with small losses.
Hydraulics An Engineering science concerned with liquid pressure and flow.
Hydrocarbons Compounds consisting only of carbon and hydrogen. Petroleum for example consists chiefly of hydrocarbons.
Hydrodynamic lubrication A method of lubrication in which the shape and relative motion of the sliding surfaces causes the formation of a fluid film having sufficient pressure to separate the surfaces.
Hydrolysis Breakdown process that occurs in anhydrous hydraulic as a result of heat, water, and metal catalysts (iron, steel, copper, etc.)
Hydrolytic stability The ability of additives and certain synthetic lubricants to withstand chemical decomposition (hydrolysis) when water is present.
Hydrometer An instrument used to ascertain either the specific gravity of a liquid or the API gravity.
Hydrophilic Compounds with an affinity for water.
Hydrophobic Compounds that repel water.
Hydrostatic lubrication A system of lubrication whereby the lubricant is supplied under adequate external pressure to separate the opposing surfaces by a fluid film.
Hypoid gear lubricant A gear lubricant possessing extreme pressure characteristics for use with hypoid type gears as in the differential of an automobile.
Hypoid Gears Gears in which the pinion axis comes in contact with the plane of the ring gear at a point below the ring-gear axle but above the outer edge of the ring gear, or above the ring-gear axle and below the outer edge of the ring gear.
Hz Hertz, Cycles per Second
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I Mech E Institute of Mechanical Engineers (UK)
ICOMIA International Council for Marine Industry Associations
IEA International Energy Agency
IFP Institut Françcais du Petrole
ILMA The Independent Lubricant Manufacturers Association (ILMA) is a trade association of businesses taking part in many aspects of the lubricant business, including compounding, blending, formulating, packaging, marketing, and distributing lubricants (See also IOCA).
ILSAC The International Lubricant Standardization and Approval Committee (ILSAC) is a joint committee of AAMA and JAMA members that assists with the creation of new safety standards for the industry.
Image analyzer An advanced system of magnification involving a microscope, a television camera, a dedicated computer, and a viewing monitor.
Immiscible Unsuited for mixing without separation of phases. For example, water and petroleum oil are immiscible under most conditions, although they can be made miscible by adding an emulsifier.
Incompatible fluids Fluids which when mixed in a system, will have a damaging effect on that system, its components or its operation.
Indicator A device which yields external evidence of perceived phenomena.
Indicator, differential pressure An indicator which signals differences in pressure between two points, generally between the upstream and downstream sides of a filter element.
Indicator, pressure An indicator for pressure conditions.
Industrial Lubricant Any petroleum or synthetic-base fluid or grease commonly used in lubricating industrial equipment.
Influent Name given to the fluid coming into a component.
Infrared (IR) analysis A type of absorption spectroscopy used to identify organic functional groups present in a used oil sample by measuring their light absorption at specific infrared wavelengths This is helpful because absorbance is proportional to concentration. The test can show additive depletion, the presence of water, hydrocarbon contamination of a synthetic lubricant, oxidation, nitration, and glycol contamination from coolant. Fourier Transform Infrared (FTIR) allows for the generation of complex curves from digital data.
Infrared spectra A graph of infrared energy absorbed at various frequencies in the additive region of the infrared spectrum. It is helpful in comparing the current sample, the reference oil and the previous samples.
Infrared spectroscopy An analytical method which uses infrared absorption to ascertain the properties of used oil and specific contaminants suspended within it. See FTIR.
Ingested contaminants An environmental contaminant that enters due to the action of the system or machine.
Ingression level Particles added per unit of circulating fluid volume.
Inhibitor Name given to any substance that slows or prevents such harmful chemical reactions as corrosion or oxidation.
In-line filter A filter assembly whereby the inlet, outlet and filter element axes are all in a straight line.
Inside-mounted seal A mechanical seal located inside the seal chamber listing the pumped product's pressure at its O.D.
Insolubles Particles of carbon or compounds of carbon and other substances. Indicator of deposition or dispersant drop-out in an engine.
INTA Instituto Nacional de Tecnica Aerospacial (Spain)
Intensifier A device used to convert low pressure fluid power into higher pressure fluid power.
Intercooler A device which cools a gas between the different compressive steps of a multiple stage compressor.
Interfacial tension (IFT) The energy per unit area located at the boundary of two immiscible liquids. It is generally expressed in dynes/cm (ASTM Designation D 971.)
IOCA Independent Oil Compounders Association (See ILMA)
IP Institute of Petroleum (UK)
IR Infrared
ISO International Standards Organization, sets viscosity reference scales.
ISO Solid Contaminant Code (ISO 4406) A code appointed on the basis of the number of particles per unit volume greater than 5 and 15 micrometers in size. Range numbers identify each increment in the particle population throughout the spectrum of levels.
ISO viscosity grade A number indicating the viscosity of an industrial fluid lubricant at 40 degrees C (104 degrees F) as defined by ASTM Standard Viscosity System for Industrial Fluid Lubricants D 2422. Essentially identical to ISO Standard 3448.
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JAMA Japan Automobile Manufacturers Association Inc.
JARI Japan Automobile Research Institute
JASIC Japan Automobile Standards Internationalisation Centre
JASO Japan Automobile Standards Organization
JAST Japan Society of Tribologists
JATA Japan Automobile Transport Technology Association
JISC Japan Industrial Standards Committee
Joule A unit of work, energy, or heat. 1J (joule)=1 Nm) (Newton meter).
Journal Part of a shaft or axle that rotates or angularly oscillates in or against a bearing or about which a bearing rotates or angularly oscillates.
Journal bearing A sliding type of bearing having rotating or oscillatory motion and in conjunction with which a journal functions. In a full or sleeve type journal bearing, the bearing surface is 360° in extent. In a partial bearing, the bearing surface is less than 360° in extent, i.e., 150°, 120°, etc.
JPI Japan Petroleum Institute
JSAE Society of Automotive Engineers (Japan)
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Karl Fischer Reagent Method (ASTM D-1744-64) Standard laboratory for measuring water content of mineral base fluids. Under this process, water reacts quantitatively with the Karl Fischer reagent. This reagent is a mixture of iodine, sulfur dioxide, pyridine, and methanol. When excess iodine exists, electric current can pass between two platinum electrodes or plates. The water in the sample reacts with the iodine. When the water is no longer free to react with iodine, an excess of iodine depolarizes the electrodes, signaling the end of the test.
kg Kilograms
kHz One thousand Hertz (cycles per second)
kilo Thousand
Kinematic viscosity The time necessary for a fixed amount of an oil to pass through a capillary tube under just the force of gravity. The unit of kinematic viscosity is the stoke or centistoke (1/100 of a stoke). Kinematic viscosity may be defined as the quotient of the absolute viscosity in centipoises divided by the specific gravity of a fluid, when temperature remains constant.
kL Kiloliters
KRL Kugelrollenlager (= TRB: Taper Roller Bearing), Often used as a fluid shear stability test.
KV Kinematic Viscosity
kW Kilowatts
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L Liter (Use upper case)
Lacquer A deposit emerging from the oxidation and polymerization of fuels and lubricants when subjected to high temperatures. Similar to, but harder, than varnish.
Laminar particles Particles created in rolling element bearings which have been flattened out by a rolling contact.
lb Pound(s) (Never lbs)
lb-bhp-h Pounds of emissions per bhp-h
lbf-ft Pound-force-foot (Use for Torque)
Light obscuration The degree of light blockage as reflected in the transmitted light affecting the photodiode.
Lip seal An elastomeric or metallic seal that prohibits leakage in dynamic and static uses by a scraping or wiping action at a controlled interference between itself and the mating surface.
LNG Liquid Natural Gas
LOA Lube Oil Additive
Load-carrying capacity Property of a lubricant to form a film on the lubricated surface, which resists rupture under given load conditions. Expressed as maximum load the lubricated system can support without failing or incurring excessive wear.
Load-wear index (LWI) Measure of the relative ability of a lubricant to prevent wear under applied loads; it is calculated from data obtained from the Four Ball EP Method. Formerly called mean Hertz load.
Log Logarithm (common)
LPG Liquified Petroleum Gas
Lubricant Name for any substance interposed between two surfaces in relative motion for the purpose of lowering friction and/or wear between them.
Lubrication Controlling friction and wear by introducing a friction-reducing film between moving surfaces in contact. The lubricant used can be a fluid, solid, or plastic substance.
Lubricator A device which administers controlled or metered amounts of lubricant into a pneumatic system.
Lubricity The ability of an oil or grease to lubricate; also known as film strength.
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m-% Mass Percent (Also Mass-%)
Magnetic filter A filter element that, in addition to its filter medium, has a magnet or magnets incorporated into its design to attract and hold ferromagnetic particles.
Magnetic plug Device which is strategically positioned in the flow stream to collect a representative sample of wear debris circulating in the system. The rate of buildup of wear debris reflects degradation of critical surfaces.
Magnetic seal A seal that uses magnetic force to keep the seal faces together.
Manifold A filter assembly containing multiple ports and integral relating devices which sustains more than one fluid circuit.
Manifold filter A filter in which the inlet and outlet port axes are at right angles, and the filter element axis is parallel to either port axis.
Material Safety Data Sheet (MSDS) A publication containing health and safety information on a hazardous product (including petroleum). The OSHA Hazard Communication Standard requires that an MSDS be provided by manufacturers to distributors or purchasers prior to or at the time of product shipment. An MSDS must include the chemical and common names of all ingredients that have been determined to be health hazards if they constitute 1% or greater of the product's composition (0.1% for carcinogens). An MSDS also includes precautionary guidelines and emergency procedures.
Media migration Material passed into the effluent stream made of elements of the filter medium.
Medium the porous material that actually performs the act of filtration. Media (pl.).
Mega Million
Metal oxides Oxidized ferrous particles which are very old or have been recently created by lack of lubrication. Trend is important.
MG Multigrade
Micron A unit of length. One Micron = 39 millionths of an inch (.000039"). Contaminant size is generally reported in microns. Relatively speaking, a grain of salt is about 60 microns and the eye can see particles to about 40 microns. Many hydraulic filters are required to be efficient enough to restrain a substantial percentage of contaminant particles as small as 5 microns. A micron is also known as a micrometre, and exhibited as µm
MIL Prefix for U.S. Military Specification
milli Thousandth
Mineral oil Oil derived from a mineral source, such as petroleum, as opposed to oils originating from plants and animals.
Mineral seal oil A distillation fraction between kerosene and gas oil, heavily used as a solvent oil in gas adsorption processes, as a lubricant for the rolling of metal foil, and as a base oil in many specialty formulations. Derives its name not from function, but from the fact that it originally replaced oil originating from seal blubber for use as an illuminant for signal lamps and lighthouses.
MIRA Motor Industry Research Association (UK)
Miscible Capable of mixing under any concentration without phase separation; e.g., water and ethyl alcohol are miscible.
MITI Ministry of International Trade and Industry (Japan)
MM 1,000,000
MoD Ministry of Defence (UK)
Moly Molybdenum disulfide, a solid lubricant and friction reducer, colloidally distributed in some oils and greases.
Molybdenum disulfide A black, lustrous powder (MoS2) that serves as a dry-film lubricant in some high-temperature and high-vacuum applications. It is also used in the form of pastes to prevent scoring when assembling press-fit parts, and as an additive for imparting residual lubrication properties to oils and greases. Also known as moly or molysulfide.
Motor A device which converts fluid power into mechanical force and motion, usually provided by rotary mechanical motion.
mpg Miles per Gallon
mph Miles per Hour
MQAD Materials Quality Assurance Directorate (UK)
MRV Mini Rotary Viscometer (For Borderline Pumping Temperature)
MSDS Material Safety Data Sheet
MT Metric Ton
MTBF An abbreviation for Mean Time Between Failures.
Multigrade oil An oil meeting the requirements of more than one SAE viscosity grade classification, and may therefore be applicable over a wider temperature range than a single-grade oil.
Multipass or recirculation test Filter performance tests whereby the contaminated fluid is allowed to recirculate through the filter for the length of the test. Contaminant is usually added to the test fluid during the test. The test is used for determining the Beta-Ratio (q.v.) of an element.
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Naphthenic Type of petroleum fluid originating from naphthenic crude oil, containing a high percentage of closed-ring methylene groups.
NAS National Aerospace Standard
NASA National Aeronautics and Space Administration
NBS National Bureau of Standards (U.S.A)
NCM National Comite Motorproeven (Netherlands) (member CEC)
nd Non-dispersant (e.g.: nd OCP )
NDOCP Nondispersant Olefin Copolymer (VI Improver)
NDPMA Nondispersant Polymethacrylate
Needle bearing A rolling type of bearing containing rolling elements that are long when compared to their diameter.
Neutralization number A measure of the total acidity or basicity of an oil; this includes both organic or inorganic or a combination thereof (ASTM Designation D974-58T)
Newtonian fluid A fluid whose viscosity remains constant at a given temperature despite the rate of shear. Single-grade oils are Newtonian fluids. Multigrade oils are Non-Newtonian fluids because viscosity does vary with shear rate.
NFPA National Fluid Power Association
Nitration Nitration products are formed as a result of the fuel combustion process in internal combustion engines. Most nitration products are formed when an abundance of oxygen is present. These products are highly acidic, form deposits in combustion areas and rapidly accelerate oxidation.
NLGI (National Lubricating Grease Institute) National Lubricating Grease Institute (USA). Trade association whose main interest is grease and the technology associated with it. NLGI is best known for its system of rating greases based on penetration.
NLGI Automotive Grease Classifications Automotive lubricating grease quality levels created jointly by SAE, ASTM and NLGI. There are several categories in two classifications: Chassis Lubricants and Wheel bearing Lubricants. Quality or performance levels within each category are established by ASTM tests.
NLGI consistency grades Simplified system created by the National Lubricating Grease Institute (NLGI) for rating grease consistency.
Nominal filtration rating An arbitrary micrometer value indicated by a filter manufacturer. Because of a lack of reproducibility this rating is deprecated.
Non-Newtonian fluid Fluid, such as a grease or a polymer-containing oil (e.g., multi-grade oil), whereby shear stress is not proportional to shear rate. Viscosity is altered with applied shear stress.
Nonwoven medium A filter medium consisting of a mat of fibers.
Normal paraffin A hydrocarbon consisting of molecules in which no single carbon atom is attached to more than 2 other carbon atoms. This is also referred to as straight chain paraffin and linear paraffin.
NOx Nitrogen Oxides
NPRA National Petroleum Refinery Association (USA)
NTC Net Treating Cost
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Obliteration A synergistic phenomenon having to do with both particle silting and polar adhesion. When water and silt particles co-exist in a fluid containing long-chain molecules, the tendency for valves to undergo obliteration is greater.
OCP Olefin Copolymer (VI Improver)
OECD Organization for Economy Corporation and Development
OEM Original Equipment Manufacturer
OENORM Österreichisches Normungs - Institut
Oil Consumption Ratio Annual oil purchases divided by machine charge volume. For example, if you bought 10,000 gallons of oil in one year and the total amount of oil that all of your machine holds is 5,000 gallons, your consumption ratio is 2.0.
Oil ring A loose ring, the inside surface of which rides a shaft or journal and dips into a reservoir of lubricant from which it transports the lubricant to the top of a bearing by its rotation with the shaft.
Oiler A device for once-through lubrication. Three common types of oilers are: drop-feed, wick-feed, and bottle-feed; all rely on gravity to create a metered flow of oil to the bearing. The drop-feed oiler distributes oil from the bottom of a reservoir to a bearing one drop at a time; flow rate control is monitored by a needle valve at the top of the reservoir. In a wick-feed oiler, the oil flows through a wick and drips from the end of the wick into the bearing; feed is regulated by chaining the number of strands, by raising or lowering the oil level, or by applying pressure to the wick. In a bottle-feed oiler, a vacuum at the top of the jar keeps the fluid from running out; as tiny bubbles of air enter, the vacuum is lowered and a small amount of oil enters the bearing or is added to a reservoir from wick the bearing is lubricated.
Oiliness That property of a lubricant that produces low friction under conditions of boundary lubrication. The lower the friction, the greater the oiliness.
Oiliness Agent An additive, generally polar in nature, used to increase the lubricity of a mineral oil. Usually referred to as a boundary lubrication additive.
OPEC Organisation of Petroleum Exporting Companies
Open bubble point (boil point) The differential gas pressure at which gas bubbles are abundantly emitted from the entire surface of a wetted filter element under specific test parameters.
Open gear A gear that is exposed to the environment, as opposed to being housed in a protective gear box. Open gears are generally large, heavily loaded, and slow moving. They are utilized in such applications as mining and construction machinery, punch presses, plastic and rubber mills, tube mills, and rotary kilns. Open gears require viscous, adhesive lubricants that bond to the metal surfaces and resist run-off. Such lubricants are often called gear shields. Top-quality lubricants for such applications are specially designed to protect the gears against the effects of water and other contaminants.
OSHA Occupational Safety and Health Administration (of the US Dept of Labor)
Outside-mounted seal A mechanical seal with its seal head located outside the seal chamber that holds the fluid to be sealed. Outside seals have the pumped fluid's pressure at their I.D.
Oxidation Takes place when oxygen attacks petroleum fluids. The process is accelerated by heat, light, metal catalysts or the presence of water, acids, or solid contaminants. It leads to increased viscosity and as well as the formation of deposits.
Oxidation inhibitor Substance applied in small amounts to a petroleum product to raise its oxidation resistance, thereby increasing its service or storage life; also called anti-oxidant. An oxidation inhibitor may work in one of these ways: (1) by combining with and modifying peroxides (initial oxidation products) to render them harmless, (2) by decomposing the peroxides, or (3) by rendering an oxidation catalyst inert.
Oxidation stability The ability of a lubricant to withstand natural degradation when in contact with oxygen.
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P Poise
Pa Pascal
PAG Poly alkene glycols
PAJ Petroleum Association of Japan
PAMA Poly Alkyl Methacrylate, Widely used viscosity index improver and pour point depressant.
PAO Poly alpha-Olefin
Paper chromatography A process which involves placing a drop of fluid on a permeable piece of paper and observing the development and nature of the halos, or rings, around the drop through time. The roots of this test can be traced to the 1940s, when railroads used the "blotter spot" tests.
Paraffin Any hydrocarbon defined by saturated straight (normal) or branched (iso) carbon chains; also called an alkane. The generalized paraffinic molecule can be symbolized by the formula CnH2n+2. Paraffins are relatively non-reactive and have excellent oxidation stability. In contrast to naphthenic oils, paraffinic lubricating oils have relatively high wax content and pour point, and generally have a high viscosity index (VI.). Paraffinic solvents are generally lower in solvency than naphthenic or aromatic solvents.
Paraffinic A type of petroleum fluid derived from paraffinic crude oil and containing a high proportion of straight chain saturated hydrocarbons. Often vulnerable to cold flow problems.
Parallel Systems Lubrication systems where the dispensing devices are attached to the main line in parallel. Each dispensing device operates independently from other systems.
Particle count The number of particles concerned greater than a particular micron size per unit volume of fluid. Often consists of particles greater than10 microns per milliliter.
Particle density An important parameter for establishing an entrained particle's potential to impinge on control surfaces, causing erosion.
Particle erosion Occurs when fluid-entrained particles traveling at high velocities pass through orifices or impinge on metering surfaces or sharp angle turns.
Particle impingement erosion A particulate wear process where high velocity, fluid-entrained particles are sent at target surfaces.
Particulates Particles combined of natural materials and manmade pollutants which, in sufficient concentrations, can be respiratory irritants.
Pascal Unit of pressure in the metric (SI) system.
Pascal?s Law A pressure applied to a confined fluid at rest is distributed with equal intensity throughout the entirety and that pressure is considered to act at right angles to each surface contacted by the fluid.
Patch test A method by which a specified volume of fluid is filtered through a membrane filter of known pore structure. All particulate matter in excess of an "average size," established by the membrane characteristics, is restrained on its surface. Thus, the membrane is discolored by an amount proportional to the particulate level of the fluid sample. Visually comparing the test filter with standard patches of known contamination levels determines acceptability for a given fluid.
PCB Polychlorinated biphenyl, a class of synthetic chemicals constructed from a homologous series of compounds beginning with monochlorobiphenyl and ending with decachlorobiphenyl. PCBs do not occur naturally in petroleum, but have been found as contaminants in used oil. PCBs have been legally established as a health hazard, and any oil so contaminated must observe strict state and federal regulations when being handled.
PCDO Passenger Car Diesel Oil
PCEOCP Passenger Car Engine Oil Classification Panel
PCMO Passenger Car Motor Oil
Permeability The relationship of flow per unit area to differential pressure across a filter medium.
Petrochemical Any chemical substance obtained from crude oil or its products, or from natural gas. Some petrochemical products may be identical to others produced from other raw materials such as coal and producer gas.
pH Measure of alkalinity or acidity in water and water-containing fluids. pH is utilized to determine the corrosion-inhibiting characteristics in water-based fluids. Typically, pH > 8.0 is required to inhibit corrosion of iron and ferrous alloys in water-based fluids.
Phenol A white, crystalline compound (C6H5OH) derived from benzene, used in the construction of phenolic resins, weed killers, plastics, and disinfectants. Also used in solvent extraction: a technique used in the petroleum refining process. Phenol is a toxic material and direct contact should be avoided.
Phosphate ester Any of a group of synthetic lubricants possessing superior fire resistance. A phosphate ester generally has poor hydrolytic stability, poor compatibility with mineral oil, and a relatively low viscosity index (VI). It is used as a fire-resistant hydraulic fluid in high temperature environments
PIB Polyisobutane
Pinion The smaller of two mating or interlocking gears; can be either the driving or the driven gear.
Pitting A form of highly localized attack indicated by holes in the metal. Pitting is one of the most destructive and insidious forms of corrosion. Depending on the environment and the medium, a pit may take months, or even years, to become noticeable.
Pleated filter A filter element whose medium is formed from of a series of uniform folds and has takes the geometric form of a cylinder, cone, disc, plate, etc. Synonymous with "convoluted" and "corrugated".
PM Pensky - Martens (Flash Point)
PMA Polymethacrylate (VI Improver)
PMAA Petroleum Marketer Association of America
PMCC Pensky-Martens Closed Cup (Flash Point Test)
PNA (polynuclear aromatic) Any of several complex hydrocarbon compounds constructed of three or more benzene rings in a compact molecular alignment. Some types of PNA's are formed in fossil fuel combustion and other heat processes, such as catalytic cracking.
Pneumatics Engineering science concerned with gaseous pressure and flow.
PNEUROP Comité Européen des Constructeurs de Compresseurs et d'Outillage Pneumatique
Poise (absolute viscosity) A measure of viscosity equal to the force necessary to move a plane surface of one square centimeter per second when the surfaces are set apart by a layer of fluid one centimeter in thickness. It is the ratio of the shearing stress to the shear rate of a fluid and is expressed with the units dyne seconds per square centimeter (DYNE SEC/CM2); 1 centipoise equals .01 poise.
Polar compound A chemical compound whose molecules exhibit electrically positive features at one extremity and negative characteristics at the other. Polar compounds are used as additives in many petroleum products. Polarity gives certain molecules a strong affinity for solid surfaces; as lubricant additives (oiliness agents), such molecules plate out to form a tenacious, friction-reducing film. Some polar molecules are oil-soluble at one end and water-soluble at the other end; making them excellent emulsifiers, helping to form stable oil-water emulsions. Such lubricants are said to have good metal-wetting properties. Polar compounds with a strong attraction for solid contaminants act as detergents in engine oils by keeping contaminants finely dispersed.
Polishing (bore) Excessive smoothing of the surface finish of the cylinder bore or cylinder liner in an engine to a mirror-like condition, resulting in depreciation of ring sealing and oil consumption performance.
Polyglycols Polymers of ethylene or propylene oxides used as a synthetic lubricant base. These compounds exhibit very good hydrolytic stability, high viscosity index (VI), and low volatility. Used primarily in water emulsion fluids.
Polymer A substance formed by linking (polymerization) of two or more simple molecules, called monomers, to create a larger one. A polymer may be liquid or solid; solid polymers may consist of millions of repeated linked units. A polymer made from two or more similar monomers is called a copolymer; a copolymer composed of three different types of monomers is a terpolymer. Natural rubber and synthetic rubbers are examples of polymers. Polymers are commonly used as viscosity index improvers in multi-grade oils and tackifiers in lubricating greases.
Polymerization The chemical combination of similar-type molecules to create larger molecules.
Polyol ester A synthetic lubricant base, created by reacting fatty acids with a polyol (such as a glycol) or petroleum derivative. Properties include good oxidation stability at high temperatures and low volatility. Used in formulating lubricants for turbines, compressors, jet engines, and automotive engines.
Polyolefin A polymer derived by polymerization of simple olefins. Polyethylene and polyisoprene are important examples of polyolefins.
Pore A small channel or opening in a filter medium which permits movement of fluid.
Pore size distribution The ratio of the number of effective holes of a given size to the total number of effective holes per unit area expressed as a percentage and as a function of hole size.
Porosity The ratio of pore volume to total volume of a filter medium expressed as a percent.
Positive crankcase ventilation (PCV) System for removing blow-by gases from the crankcase and returning them by way of the carburetor intake manifold to the combustion chamber where the recirculated hydrocarbons are burned. A PC valve controls the flow of gases from the crankcase to lower hydrocarbon emissions.
Pour point Lowest temperature at which an oil or distillate fuel has the ability to flow, when cooled under conditions prescribed by test method ASTM D 97. The pour point is 3°C (37.4°F) above the temperature at which the oil in a test vessel has no movement when the container is held horizontally for five seconds.
Pour point depressant An additive designed to hinder the adverse effects of wax crystallization, and lowers the pour point.
Pour stability The ability of a pour depressed oil to preserve its original ASTM pour point when exposed to long-term storage at low temperature similar to winter conditions.
Power unit A combination of pump, pump drive, reservoir, controls and conditioning components which may be required for its operation.
PP Pour Point
ppb Parts per billion (1E+9)
PPC Petroleum Packaging Council
PPD Pour Point Depressant
ppm Parts per million (1/ppm = 0.000001). Generally by weight. 100 ppm = 0.01%; 10.000 ppm = 1%; 1 ppm = 1.000 ppb
ppma Parts per Million Active
Predictive maintenance A type of condition-based maintenance focusing on early prediction of failure using non-destructive methods such as vibration analysis, thermography, and wear debris analysis.
Pressure Force per unit area, generally stated in pounds per square inch.
Pressure Drop Resistance to flow caused by the element (media) in a filter. Defined as the difference in pressure upstream (inlet side of the filter) and downstream (outlet side of the filter).
Pressure gage Pressure difference above or below atmospheric pressure.
Pressure line filter A filter located in a line transporting working fluid to a device or devices in need.
Pressure, absolute The sum of atmospheric and gage pressures.
Pressure, atmospheric Pressure exercised by the atmosphere on a specific location. (Sea level pressure is approximately 14.7 pounds per square inch absolute.)
Pressure, back The pressure observed on the return side of a system.
Pressure, cracking Necessary pressure for a pressure operated valve to begin to pass fluid.
Pressure, rated The suitable operating pressure which is recommended for a component or a system by the manufacturer.
Pressure, system The pressure needed to overcome the total resistance in a system. It includes all losses as well as useful work.
Preventive maintenance Maintenance performed on a fixed schedule concerning the routine repair and replacement of machine parts and components.
Proactive maintenance A type of condition-based maintenance focusing on the routine discovery and correction of root cause conditions that would otherwise lead to failure. Such root causes as high lubricant contaminant, alignment and balance are among the most critical.
Process oil An oil that serves as a temporary or permanent component of a manufactured product. Aromatic process oils possess good solvency characteristics; their applications include proprietary chemical formulations, ink oils, and extenders in synthetic rubbers. Naphthenic process oils are defined by low pour points and good solvency properties. Paraffinic process oils are characterized by low aromatic content and light color.
psi Pounds per square inch
psia Pounds per square inch absolute
PSIA Pounds per square inch absolute. (PSIG + 14.696)
PSID Pounds per square inch differential.
PSIG Pounds per square inch gauge (PSIA - 14.696)
PSSI Permanent Shear Stability Index
PTFE Poly tetra fluoro ethylene
Pump A device which utilizes mechanical force and motion to create hydraulic fluid power.
Pump, fixed displacement A pump in which the displacement per cycle cannot be varied.
Pump, variable displacement A pump in which the displacement per cycle can be varied.
Pumpability The low temperature, low shear stress-shear rate viscosity characteristics of an oil that allow for sufficient flow to and from the engine oil pump and subsequent lubrication of moving components.
Pusher seal A mechanical seal in which the secondary seal is pushed along the shaft or sleeve to neutralize misalignment and face wear.
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Q Flow rate - GPM
Quick Disconnect A coupling which can quickly join or separate a fluid line without need for tools or special devices.
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R & O - Rust-and-oxidation inhibited A term applied to extremely refined industrial lubricating oils formulated for long service in circulating lubrication systems, compressors, hydraulic systems, bearing housing, gear boxes, etc. The finest R&O oils are often referred to as turbine oils.
R&O Rust and Oxidation (Inhibited)
Rate of shear The difference between the velocities along the parallel faces of a fluid element divided by the distance between the faces.
Rated Flow The maximum flow that the power supply system is able to maintain at an indicated operating pressure.
Reducer A connector having a smaller line size at one end than the other.
Refining A series of processes necessary to convert crude oil and its fractions into finished petroleum products. Following distillation, a petroleum fraction may undergo one or more additional steps to purify or modify it. These refining steps include; thermal cracking, catalytic cracking, polymerization, alkylation, reforming, hydrocracking, hydroforming, hydrogenation, hydrogen treating, hydrofining, solvent extraction, dewaxing, deoiling, acid treating, clay filtration, and deasphalting. Refined lubricating oils may be blended with other lube stocks, and additives may be incorporated, to endow specific properties.
Refraction The change of direction or speed of light as it moves from one medium to another.
Refrigerator oil The lubricant applied to the working fluid in an expansion-type cooling unit which acts to lubricate the pump mechanism.
Rerefining A process of reclaiming used lubricant oils and returning them to a condition similar to that of virgin stocks by filtration, clay adsorption or more elaborate methods.
Reservoir A container for storage of liquid in a fluid power system.
Reservoir (sump) filter A filter installed in a reservoir in series with a suction or return line.
Residual dirt capacity The dirt capacity left behind in a service loaded filter element after use, but before cleaning, measured under the same conditions as the dirt capacity of a new filter element.
Return line Position in a line conducting fluid from working device to reservoir.
Return Line Filtration Filters located upstream of the reservoir but after fluid has proceeded through the system's output components (cylinders, motors, etc.).
Reynold's number A numerical ratio of the dynamic forces of mass flow to the shear stress due to viscosity. Flow generally changes from laminar to turbulent between Reynold's Number 2,000 and 4,000.
Rheology The study of the degradation and flow of matter in terms of stress, strain, temperature, and time. The rheological properties of a grease are usually recorded by penetration and apparent viscosity.
RI Rush Inhibitor
Ring lubrication A system of lubrication in which the lubricant is supplied to the bearing by an oil ring.
Ring sticking The freezing of a piston ring in its groove in a piston engine or reciprocating compressor due to large deposits in the piston ring zone.
Rings Circular metallic elements that ride in the grooves of a piston providing compression sealing during combustion. Also used to distribute oil for lubrication.
Roller bearing An antifriction bearing made of rolling elements in the form of rollers.
Rotary seal A mechanical seal which rotates with a shaft and is used with a stationary mating ring.
rpm Revolutions per Minute
Rust inhibitor A type of corrosion inhibitor used in lubricants to help them to resist rusting
Rust prevention test (turbine oils) A test for determining the an oil's ability to assist in preventing the rusting of ferrous parts in water.
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SAE Society of Automotive Engineers (USA), an organization serving the automotive industry.
SAE port A straight thread port utilized to attach tube and hose fittings. It employs an  O ring compressed in a wedge-shaped cavity. A standard of the Society of Automotive Engineers J514 and ANSI/B116.1.
SAE viscosity The viscosity classification of a motor oil according to the system developed by the Society of Automotive Engineers and now in general use.  Winter grades are defined by viscosity measurements at low temperatures and have  W as a suffix, while  Summer grades are defined by viscosity at 100 °C and have no suffix. Multigrade oils meet both a winter and a summer definition and have designations such as SAE 10W-30, etc.
SAN Strong Acid Number
Saponification number The number of milligrams of potassium hydroxide (KOH) that combine with one gram of oil under conditions indicated by test method ASTM D 94. Saponification number is an indicator of the amount of fatty saponifiable substances in compounded oil. Caution must be taken in interpreting test results if certain substances - such as sulfur compounds or halogens - are present in the oil, since these also react with KOH, thereby raising the apparent Saponification number.
Saturation level Total amount of water that can dissolve in a fluid.
Saybolt Universal Viscosity (SUV) or Saybolt Universal Seconds, (SUS) The time in seconds necessary for 60 cubic centimeters of a fluid to flow through the orifice of the Standard Saybolt Universal Viscometer at a given temperature under specified conditions. (ASTM Designation D 88.)
SBT Scanning Brookfield Temperature
Scoring Stress marks on sliding metallic surfaces in the form of long, distinct scratches in the direction of motion. Scoring is an advanced stage of scuffing.
Scuffing Abnormal engine wear attributed to localized welding and fracture. It can be prevented through the use of antiwear, extreme-pressure and friction modifier additives.
Scuffing particles Large twisted and discolored metallic particles caused from adhesive wear due to total lubricant film breakdown.
Seal A device designed to stop the flow of fluid from one area to another, or to eliminate contaminants.
Seal assembly A group of parts, or an assembly, that includes sealing surfaces, provisions for initial loading, and a secondary sealing mechanism that accommodates the radial and axial movement needed for installation and operation.
Seal chamber The area between the seal chamber bore and a shaft in which a mechanical seal is installed.
Seal face Either of the two lapped surfaces in a mechanical seal assembly making up the primary seal.
Seal face width The radial distance from the inside edge to the outside edge of the sealing face.
Seal Swell (rubber swell) The swelling of rubber (or other elastomers) gaskets, or seals when in contact with petroleum, synthetic lubricants, or hydraulic fluids. Seal materials vary widely in their defense against the effects of such fluids. Some seals are designed so that a small amount of swelling increases sealing action.
Semisolid Any substance having the characteristics of both a solid and a liquid. Similar to semiliquid but being more of a solid than a liquid. More generally, any material in which the force necessary to produce a deformation depends both on the magnitude and on the rate of the deformation.
Servovalve A valve which regulates output as a function of an input command.
Severe sliding Large ferrous particles which are created by sliding contacts. It is used to determine if abnormal wear is taking place.
Shear rate Rate at which adjacent layers of fluid move in relation to each other, usually stated as reciprocal seconds.
Shear stability The ability of a polymer additized fluid to resist mechanical degradation. A low shear stability index (SSI) is a measure of good shear stability.
Shear stress Frictional force overcome in sliding one "layer" of fluid along another, as in any fluid flow. The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with shear rate (velocity). The ratio between shear stress and shear rate remains constant; this ratio is termed viscosity of a Newtonian fluid, the greater the shear stress as a function of rate of shear. In a non-Newtonian fluid.
SI International System of Units (Système International d'Unités)
SIA Société des Ingenieurs de l'Automobile (France)
Silt Particles of contaminant 5 µm or less in size.
Silting A failure usually associated with a valve which movements are limited due to small particles that have wedged in between important clearances (e.g., the spool and bore.)
Single-pass test Filter performance tests in which contaminant which passes through a test filter is not allowed to recirculate back to the test filter.
Sintered medium A metallic or nonmetallic filter medium processed to cause diffusion bonds at all contacting points.
Sleeve bearing A journal bearing, usually a full journal bearing.
Sloughing off The discharge of contaminant from the upstream side of a filter element to the upstream side of the filter enclosure.
Sludge Insoluble material created as a result either of deterioration reactions in or contamination of an oil, or both.
SME Society of Manufacturing Engineers
SMR Svenska Mekanisters Riksforenig (member CEC)
SN Solvent Neutral Oil (Also SNO)
SNV Schweizerische Normenvereiniung (member CEC)
Solvency The ability of a fluid to dissolve inorganic materials and polymers: a function of aromaticity.
Solvent A material with a strong ability to dissolve a given substance. The most common petroleum solvents are mineral spirits, xylene, toluene, hexane, heptane, and naphthas. Aromatic-type solvents have the highest solvency for organic chemical materials, followed by naphthenes and paraffins. Generally, the solvent disappears, usually by evaporation, after it has served its purpose. The evaporation rate of a solvent is very crucial in manufacture.
Solvent Extraction A refining process used to separate components (unsaturated hydrocarbons) from lube distillates in order to enhance the oil's oxidation stability, viscosity index, and response to additives. The oil and the solvent extraction media are mixed in an extraction tower, concluding in the formation of two phases: a heavy phase consisting of the undesirable unsaturates dissolved in the solvent, and a lighter phase made of a high quality oil with some solvent dissolved in it. The phases are separated and the solvent regained from each through distillation.
Specific gravity The ratio of the weight of a given volume of material to the weight of an equal volume of water.
Specific gravity (liquid) The ratio of the weight of a given volume of liquid to the weight of an equal volume of water.
Spectrographic analysis Used to determine element concentration present in the entrained fluid contaminant.
Spectrographic Oil Analysis Program (SOAP) Procedures used to extract fluid samples from operating systems for analysis through spectrography to indicate the presence of key elements.
Spin-on filter A disposable type bowl and element assembly that mates with a permanently installed head.
Splash lubrication A system of lubrication in which parts of a mechanism dip into and splash the lubricant onto themselves and/or other parts of the mechanism.
SPP Stable Pour Point
SRB Styrene Butadiene Polymer
SSI Shear Stability Index
SSU Saybolt Universal Seconds (or SUS), a unit of measure used to indicate viscosity, e.g., SSU @ 100 °F
Static friction The force just sufficient enough to initiate relative motion between two bodies under load. The value of the static friction at the instant relative motion starts is defined as break-away friction.
Static seal A seal between two surfaces with no relative motion.
Stationary seal A mechanical seal in which the flexible members do not rotate with the shaft.
Statistical process control (SPC) The use of control charts to track and eliminate variables in repetitive manufacturing processes in order to guarantee that the product is of uniform, predictable quality. If a chart reveals only chance variations that are expected in the system, the process is said to be in a state of  statistical control . If the chart shows variations traceable to changes in equipment, procedures or workers, the process is said to be ? out of control?. Statistical process control differs from statistical quality control in that the former monitors manufacturing process parameters and the latter monitors product quality parameters.
Stick-slip motion Erratic, noisy motion indicative of some machine ways, due to the starting friction encountered by a machine part at each end of its back-and-form reciprocal movement. This undesirable effect can be overcome by applying a way lubricant to reduce starting friction.
STLE Society of Tribologists and Lubrication Engineers, formerly ASLE, American Society of Lubrication Engineers.
Stoke (St) Kinematic measurement of a fluid's resistance to flow indicated by the ratio of the fluid's dynamic viscosity to its density.
STOU Super Tractor Oil Universal
Straight mineral oil Petroleum oil containing no additives. Straight mineral oils include such diverse products as low-cost once-through lubricants and intensely refined white oils. Most high-quality lubricants do contain additives.
Straight oil A mineral oil containing no additives.
Strainer A coarse filter element (pore size over approximately 40 µm)
STUO Super Tractor Universal Oil
Suction filter A pump intake-line filter in which the fluid is lower than atmospheric pressure.
Sulfated ash The ash content of fresh, compounded lubricating oil as established by ASTM Method D 874. Used to indicate the level of metallic additives in the oil.
Sulfonate A hydrocarbon in which a hydrogen atom has been replaced with the highly polar (SO2OX) group, where X is a metallic ion or alkyl radical. Petroleum sulfonates are refinery by-products of the sulfuric acid treatment of white oils. Sulfonates have important applications as emulsifiers and chemical intermediates in petrochemical manufacture, and substituted sulfonates are widely used to stop corrosion. Synthetic sulfonates can be made from special feedstocks rather than from white oil base stocks.
Sulfur A common natural constituent of petroleum products. While certain sulfur compounds are commonly used to improve the EP, or load-carrying, properties of an oil, high sulfur content in a petroleum product may be undesirable as it can be corrosive and is environmentally hazardous when burned. For these reasons, sulfur restrictions are specified in the quality control of fuels, solvents, etc.
Sulfurized oil Oil to which sulfur or sulfur compounds are added.
Superclean 10 particles >10 micron per milliliter
Surface fatigue wear The formation of surface or subsurface cracks and fatigue crack propagation. It results from cyclic loading of a surface.
Surface filtration Filtration which essentially retains contaminant on the influent surface.
Surface tension The contractile surface force of a liquid by which it tends to attain a spherical form and to exhibit the least possible surface. It is represented in dynes/cm or ergs/cm2.
Surfactant Surface-active agent that lowers interfacial tension of a liquid. A surfactant used in a petroleum oil may raise the oil's affinity for metals and other materials.
Surge A temporary rise of pressure in a circuit.
SUS (SSU) Saybolt Universal Seconds. A measure indicating lubricating oil viscosity in the oil industry. The measuring device is filled with a specific quantity of oil or other fluid and its flow time through standardized orifice is measured in seconds. Fast-flowing fluids (low viscosity) will have low value; Slow-flowing fluids (high viscosity) will have high value.
Switch, pressure An electric switch controlled by fluid pressure.
Synthetic hydrocarbon Oil molecule with superior oxidation properties designed primarily out of paraffinic materials.
Synthetic lubricant A lubricant created by chemical synthesis rather than by extraction or refinement of petroleum to produce a compound with planned and predictable properties.
Synthetic oils Oils created by synthesis (chemical reaction) rather than by extraction or refinement. Many (but not all) synthetic oils offer immense superiority in terms of high temperature stability and low temperature fluidity, but because of this are much more costly than mineral oils. Major advantage of all synthetic oils is their chemical uniformity.
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Tacky A descriptive term pertaining to lubricating oils and greases which appear especially sticky or adhesive.
TAN Total Acid Number (ASTM D 664)
TBA Tertiary Butyl Alcohol
TBN Total Base Number (ASTM D 2896 preferred, or D 664)
TBO Time Between Overhauls
TBS Tapered Bearing Simulator (CCS)
TC Turbocharged
TC Two Cycle Oils
TCC Tag Closed Cup (Flash Point Test)
TE Thickening Efficiency
TGF Top Groove Fill
THCT Turbo Hydramatic Cycling Test
Thermal conductivity Measure of a solid or liquid's ability to transfer heat.
Thermal stability Ability of a fuel or lubricant to withstand oxidation at high temperature operating conditions.
Thermography The use of infrared thermography so that temperatures of a wide variety of targets can be observed remotely and without contact. This is accomplished by measuring the infrared energy radiating from the surface of the target and converting this measurement to an equivalent surface temperature.
THF Tractor Hydraulic Fluid
Thin film lubrication A condition of lubrication in which the film thickness of the lubricant is such that the friction between the surfaces is ascertained by the properties of the surfaces as well as by the lubricant's viscosity.
Thixotropy That property of a lubricating grease which is exhibited by a softening in consistency as a result of shearing followed by a hardening in consistency starting directly after the shearing is stopped.
THOT Turbo Hydramatic Oxidation Test
Three-body abrasion A particulate wear process whereby particles are pressed between two sliding surfaces.
Thrust Bearing An axial-load bearing.
Timken EP Test Measure of the extreme-pressure properties of a lubricating oil. The test uses a Timken machine, which consists of a stationary block pushed upward, by means of a lever arm system, against the rotating outer race of a roller bearing, which is lubricated by the product under test. The test continues under increasing load (pressure) until a measurable wear scar develops on the block.
Timken OK Load The heaviest load that a test lubricant will bear without scoring the test block in the Timken Test procedures, ASTM Methods D 2509 (greases) and D 2782 (oils).
TISI Thailand Industrial Standards Institute
TOC Tag Open Cup (Flash Point Test)
TORT Turbine Oil Rust Test
TOST Turbine Oil Stability Test
Total Acid Number (TAN) The quantity of base, expressed in milligrams of potassium hydroxide, necessary to neutralize all acidic constituents present in 1 gram of sample. (ASTM Designation D 974.)
Total Base Number (TBN) The quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is necessary to neutralize all basic constituents located in 1 gram of sample. (ASTM Designation D 974.)
TOU Tractor Oil Universal
TOW Temperature Operating Window, defined by a fluid's ability to meet OEM start-up and minimum viscosity requirements, see NFPA recommended practice T2.13.13-2002
TRB Taper Roller Bearing
Tribology The science and technology of interacting surfaces in relative motion, including the study of lubrication, friction and wear. Tribological wear is wear that occurs as a result of relative motion on the surface.
TRIPARTITE Co-operation: API - ASTM - SAE
TSCA Toxic Substances Control Act
Turbidity The degree of opacity of a fluid.
Turbine oil A top-quality rust-and-oxidation-inhibited (R&O) oil that achieves the rigid requirements often imposed on steam-turbine lubrication. Quality turbine oils are also defined by good demulsibility, a requisite of effective oil-water separation. Turbine oils are widely utilized in other exacting applications for which long service life and dependable lubrication are required. Such compressors, hydraulic systems, gear drives, and other equipment. Turbine oils can also be used as heat transfer fluids in open systems, where oxidation stability is of primary concern.
Turbulent flow sampler A sampler that contains a flow path in which turbulence is introduced in the main stream by quickly changing the fluid's direction.
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UBA Umweltbundesamt (Germany)
UBS Unconventional Base Stocks
UEIL European Union of Independent Lubricant Manufacturers
UIC Union des Industries Chimiques (France)
Ultraclean 1 particle >10 micron per milliliter
Unbalanced seal A mechanical seal arrangement wherein the full hydraulic pressure of the seal chamber works to close the seal faces.
Unloading The release of contaminant that the filter medium initially captured.
UTAC Union Technique de l'Automobile et du Cycle (France)
UTTO Universal Tractor Transmission Oil
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V Total volume (gals)
Vacuum separator A separator that uses subatmospheric pressure to remove certain gases and liquids from another liquid because of differences in vapor pressure.
Valve A device used to control fluid flow direction, pressure, or flow rate.
Valve lifter Sometimes called a "cam follower," a component in engine designs that use a linkage system between a cam and the valve it controls. The lifter typically translates the rotational motion of the cam to a reciprocating linear motion in the linkage system.
Valve, by-pass A valve primarily used to provide an alternate flow path.
Valve, directional control A valve primarily utilized to direct or prevent flow through specific passages.
Valve, directional control, servo A directional control valve used to modulate flow or pressure as a function of its input signal.
Valve, flow control A valve primarily used to control flow rate.
Valve, pressure control, relief A pressure control valve used to limit system pressure.
Valve, relief, differential pressure A valve designed to limit differential pressure.
Vapor pressure Pressure of a confined vapor in equilibrium with its liquid at indicated temperature: thus a measure of a liquid's volatility.
Vapor Pressure-Reid (RVP) Measure of the pressure of vapor condensed above a sample of gasoline or other volatile fuel in a standard bomb at 100 °F (37.8 °C). Utilized to predict the vapor locking properties of the fuel in a vehicle's fuel system. Controlled by law in some areas to help prevent air pollution caused by hydrocarbon evaporation.
Varnish When applied to lubrication, a thin, insoluble, nonwipeable film deposit occurring on interior parts, caused by the oxidation and polymerization of fuels and lubricants. May cause sticking and malfunction of close-clearance moving parts. Similar to, but softer, than lacquer.
VI Viscosity Index
VII Viscosity Index Improver
Viscometer or Viscosimeter An apparatus for determining a fluid's viscosity
Viscosity Measurement of a fluid's resistance to flow. The common metric unit of absolute viscosity is the poise, which by definition is the force in dynes necessary to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. In addition to kinematic viscosity, there are other methods for determining viscosity, including Saybolt Universal Viscosity (SUV), Saybolt Furol viscosity, Engier viscosity, and Redwood viscosity. Since viscosity varies inversely with temperature, its value is meaningless until the temperature at which it is determined is known.
Viscosity grade Any of a number of systems which define lubricants depending on viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils.
Viscosity index (VI) Frequently used measure of a fluid's change of viscosity with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature.
Viscosity index improvers Additives that increase a fluid's viscosity throughout its useful temperature range. Examples of these are polymers that possess thickening power as a result of their high molecular weight and are necessary for formulating multi-grade oils.
Viscosity modifier Lubricant additive, generally a high molecular weight polymer, that lowers the tendency of an oil's viscosity to be altered with temperature.
Viscosity, absolute The ratio of the shearing stress to the shear rate of a fluid. It is usually expressed in centipoise.
Viscosity, dynamic Viscosity measured under force induced flow. The common unit is centipoise, cP.
Viscosity, kinematic Viscosity measured under gravity induced flow. The common unit is centistokes, cSt. Also determined as the absolute viscosity divided by the fluid's density.
Viscosity, SUS Saybolt Universal Seconds (SUS), which is the time in seconds for 60 milliliters of oil to flow through a standard orifice at a specific temperature. (ASTM Designation D88-56.)
Viscosity-temperature relationship Term for the manner in which the viscosity of a given fluid varies inversely with temperature. Because of the mathematical relationship that exists between these two variables, it is possible to graphically predict a fluid's viscosity at any temperature. If the viscosities at two other temperatures are known, interpretation is possible over a set range. The charts used for this purpose are the ASTM Standard Viscosity-Temperature Charts for liquid Petroleum Products, available in 6 ranges. If two known viscosity-temperature points of a fluid are located on the chart and a straight line drawn through them, other viscosity-temperature values of the fluid will fall on this line; however, values near or below the cloud point of the oil may deviate from the straight-line relationship.
Volatility Property which describes the degree and rate at which a liquid will vaporize under set conditions of temperature and pressure. When a liquid's stability changes, this property is often reduced in value.
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Water-Glycol fluid A fluid composed mainly of water and one or more glycols or polyglycols.
Wear The attrition or rubbing away of a material's surface as a result of mechanical action.
Wear debris Particles that are removed from machine surfaces as a result of wear and corrosion. Also known as wear particles.
Wear inhibitor An additive which protects the rubbing surfaces against wear, particularly from scuffing, in the event that the hydrodynamic film is ruptured.
Weld point The lowest applied load in kilograms at which the rotating ball in the Four Ball EP test either seizes and attaches to the three stationary balls, or at which extreme scoring of the three balls occurs.
WGK Wassergefährdungsklassen
WHO World Health Organisation
Wicking The vertical absorption of a liquid into a porous material by capillary forces.
WIF Wax Interaction Factor
WPC World Petroleum Congress
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ZDDP An antiwear additive located in various types of hydraulic and lubricating fluids. Zinc dialkyldithiophosphate.
ZDTP Zinc Dithiophosphate, see also ZDDP.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


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