Lubrication and Oil Analysis Dictionary
The field of lubrication and oil analysis is filled with technical terms, jargon, acronyms, and definitions. Use the dictionary as a resource to gain a clearer understanding of concepts and definitions:!
2-BODY ABRASIVE WEAR
Is caused by rubbing of a softer surface by a hard rough surface.
3-BODY ABRASIVE WEAR
Is caused by hard particles entrapped between two sliding surfaces.
ABRASION
A general wearing away of a surface by constant scratching, usually due to the presence of foreign matter such as dirt, grit, or metallic particles in the lubricant. It may also cause a breakdown of the material (such as the tooth surfaces of gears). Lack of proper lubrication may result in abrasion.
ABRASIVE WEAR
(or cutting wear) Comes about when hard surface asperities or hard particles that have embedded themselves into a soft surface and plough grooves into the opposing harder surface, e.g., a journal.
ABSOLUTE FILTRATION RATING
The diameter of the largest hard spherical particle that will pass through a filter under specified test conditions. This is an indication of the largest opening in the filter elements.
ABSOLUTE PRESSURE
The sum of atmospheric and gauge pressure.
ABSOLUTE VISCOSITY
A term used interchangeably with viscosity to distinguish it from either kinematic viscosity or commercial viscosity. Absolute viscosity is the ratio of shear stress to shear rate. It is a fluid’s internal resistance to flow. The common unit of absolute viscosity is the poise. Absolute viscosity divided by fluid density equals kinematic viscosity. It is occasionally referred to as dynamic viscosity. Absolute viscosity and kinematic viscosity are expressed in fundamental units. Commercial viscosity such as Saybolt viscosity is expressed in arbitrary units of time, usually seconds.
ABSORBENT FILTER
A filter medium that holds contaminant by mechanical means.
ABSORPTION
The assimilation of one material into another; in petroleum refining, the use of an absorptive liquid to selectively remove components from a process stream.
AC FINE TEST DUST (ACFTD)
A test contaminant used to assess both filters and the contaminant sensitivity of all types of tribological mechanisms.
ACCUMULATOR
A container in which fluid is stored under pressure as a source of fluid power.
ACID
In a restricted sense, any substance containing hydrogen in combination with a nonmetal or nonmetallic radical and capable of producing hydrogen ions in solution.
ACIDITY
In lubricants, acidity denotes the presence of acid-type constituents whose concentration is usually defined in terms of total acid number. The constituents vary in nature and may or may not markedly influence the behavior of the lubricant.
ACID NUMBER
The quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize the acidic constituents in 1 gram of sample.
ADDITIVE
A compound that enhances some property of, or imparts some new property to, the base fluid. In some hydraulic fluid formulations, the additive volume may constitute 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. Additive stability — the ability of additives in the fluid to resist changes in their performance during storage or use.
ADDITIVE LEVEL
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 resist changes in their performance during storage or use.
ADHESION
The property of a lubricant that causes it to cling or adhere to a solid surface.
ADHESIVE WEAR
Is often referred to as galling, scuffing, scoring, or seizing. It happens when sliding surfaces contact one another, causing fragments to be pulled from one surface and to adhere to the other.
ADSORBENT FILTER
A filter medium primarily intended to hold soluble and insoluble contaminants on its surface by molecular adhesion.
ADSORPTION
Adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact; e.g. the plating out of an anti-wear additive on metal surfaces.
ADSORPTIVE FILTRATION
The attraction to, and retention of particles in, a filter medium by electrostatic forces, or by molecular attraction between the particles and the medium.
AERATION
The state of air being suspended in a liquid such as a lubricant or hydraulic fluid.
A.G.M.A
Abbreviation for “American Gear Manufacturers Associations,” an organization serving the gear industry. A voluntary association of companies, consultants, and academicians with a direct interest in the design, manufacture, and application of gears, couplings and related power transmissions components and equipment.
AGGLOMERATION
The potential of the system for particle attraction and adhesion.
AIR, COMPRESSED
Air at any pressure greater than atmospheric pressure.
AIR BREATHER
A device permitting air movement between atmosphere and the component in/on which it is installed.
AIR ENTRAINMENT
The incorporation of air in the form of bubbles as a dispersed phase in the bulk liquid. Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to a sudden change in environment.
AIR MOTOR
A device which converts compressed gas into mechanical force and motion. It usually provides rotary mechanical motion.
ALKALI
Any substance having basic properties (as contrasted with acidic properties). In a restricted sense it is applied to the hydroxides of ammonium, lithium, potassium, and sodium. Alkaline materials in lubricating oils neutralize acids to prevent acidic (corrosive) wear in internal combustion engines. Examples are lime, soda ash, milk of magnesia, and baking soda.
AMBIENT TEMPERATURE
Temperature of the area or atmosphere around a process, not the operating temperature of the process itself.
AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)
An organization intended to establish terminologies, improve methods of testing, rating, and analysis, and represent US interests in internationals standards work.
AMERICAN PETROLEUM INSTITUTE (API)
Organization to enhance the interests of the petroleum industry, including to clear information, conduct research, and develop and maintain the API Service Classifications for crankcase oils.
AMERICAN PETROLEUM INSTITUTE CERTIFICATION
Engine service classification for gasoline and diesel engine oil quality levels, established jointly by API, SAE, and ASTM. Sometimes called SAE or API/SAE categories; formerly called API Engine Service Classifications.
AMERICAN PETROLEUM INSTITUTE GRAVITY
A gravity scale established by the American Petroleum Institute and in general use in the petroleum industry.
ANALYTICAL FERROGRAPHY
the magnetic precipitation and subsequent analysis of wear debris from a fluid sample This approach involves passing a volume of fluid over a chemically treated microscope slide which is supported over a magnetic field. Permanent magnets are arranged in such a way as to create a varying field strength over the length of the substrate. This varying strength causes wear debris to precipitate in a distribution with respect to size and mass over the Ferrogram. Once rinsed and fixed to the substrate, this debris deposit serves as an excellent media for optical analysis of the composite wear particulates.
ANHYDROUS
Devoid of water.
ANILINE POINT
The minimum temperature for complete miscibility of equal volumes of aniline and the sample under test ASTM Method D 611. 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.
ANTI-FOAM AGENT
One of two types of additives used to reduce foaming in petroleum products: silicone oil to break up large surface bubbles, and various kinds of polymers that decrease the amount of small bubbles entrained in the oils.
ANTI-FRICTION (AF) BEARING
A rolling contact type bearing in which the rotating or moving member is supported or guided by means of ball or roller elements. Does not mean without friction.
ANTI-OXIDANTS (OXIDATION INHIBITORS)
Prolong the induction period of a base oil in the presence of oxidizing conditions and catalyst metals at elevated 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 — air, water, metallic particles, and dust.
ANTISTATIC ADDITIVE
An additive that increases the conductivity of a hydrocarbon fuel to hasten the dissipation of electrostatic charges during high-speed dispensing, thereby reducing the fire/explosion hazard.
ANTIWEAR ADDITIVES
Improve the service life of tribological elements operating in the boundary lubrication regime. Antiwear compounds (for example, ZDDP and TCP) start decomposing at 90° to 100°C and even at a lower temperature if water (25 to 50 ppm) is present.
API ENGINE SERVICE CATEGORIES
Gasoline and diesel engine oil quality levels established jointly by API, SAE, and ASTM, and sometimes called SAE or API/SAE categories; 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 being called “the A.P.I. degree.” This unit is defined in terms of specific gravity as follows:
API °
(141.5 ÷ specific gravity at 60/60°F) ? 131.5
The notation 60/60°F specifies a density measured at 60°F and referenced to water at 60°F. The density of water at one atmosphere and 60°F is 62.368 lbm/ft3 or 999.04 kg/m3.
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).
AQUEOUS TOXICITY
Pass/Fail measure of a hydrocarbon’s toxicity. Rainbow trout test at 100 PPM lubricant. If more than 50% of the fish die, then the lubricant is toxic.
AROMATIC
Hydrocarbon containing a Benzene ring formation found in lubricant base stocks. Generally, this hydrocarbon is undesirable and is removed to the maximum extent possible. Unsaturated hydrocarbon, aromatics are usually more reactive and have higher solvency than paraffins or naphthenes.
ARRHENIUS RULE
Law of thermal physics that describes how the oxidation rate of oil doubles for every 18°F temperature increase (generally starting at 140°F for mineral oils and 170°F for synthetics.)
ASH
A measure of the amount of inorganic material in lubricating oil. Determined by burning the oil and weighing the residue. Results expressed as percent by weight.
ASPERITIES
Microscopic projections on metal surfaces resulting from normal surface-finishing processes. Interference between opposing asperities in sliding or rolling applications is a source of friction, and can lead to metal welding and scoring. Ideally, the lubricating film between two moving surfaces should be thicker than the combined height of the opposing asperities.
A.S.T.M.
American Society for Testing and Materials. A society for developing standards for materials and test methods.
ATMOSPHERIC PRESSURE
Pressure exerted by the atmosphere at any specific location. (Sea level pressure is approximately 14.7 pounds per square inch absolute).
ATMOIC 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 fine spray, dissolving it, and finally vaporizing it with a flame. The vaporization of the metal particles depends upon their time in the flame, the flame temperature, and the composition 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. In addition, the absorption of radiant energy by electronic transitions from ground to excited state is essentially and absolute measure of the number of atoms in the flame and is, therefore, the concentration of the element in a sample.
ATOMIZATION
The conversion of a liquid into a spray of very fine droplets.
AUTOMATIC TRANSMISSION FLUID (ATF)
Fluid for automatic, hydraulic transmissions in motor vehicles.
AXIAL-LOAD BEARING
A bearing in which the load acts in the direction of the axis of rotation. See Thrust Load.
BABBITT
A soft, white, non-ferrous alloy bearing material composed principally of copper, antimony, tin and lead.
BACK PRESSURE
The pressure encountered on the return side of a system.
BACTERIA
Microorganisms often composed of a single cell.
BACTERIACIDE
Additive included in the formulations of water-mixed cutting fluids to inhibit the growth of bacteria promoted by the presence of water, thus preventing odors that can result from bacterial action.
BAFFLE
A device to prevent direct fluid flow or impingement on a surface.
BALL BEARING
An antifriction rolling type bearing containing rolling elements in the form of balls.
BARREL
A unit of liquid volume of petroleum oils equal to 42 U.S. gallons or approximately 35 Imperial gallons.
BASE
A material which neutralizes acids. An oil additive containing colloidally dispersed metal carbonate, used to reduce corrosive wear.
BASE STOCK
The base fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants.
BEARING
Support or guide by means of which a moving part such as a shaft or axle is positioned with respect to the other parts of a mechanism.
BETA RATING
The method of comparing filter performance based on efficiency. This is done using the Multi-Pass Test which counts the number of particles of a given size before and after fluid passes through a filter.
BETA RATIO (ß-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 at a right angle).
BIOCIDES
Additive designed to inhibit the growth of microorganisms in liquids.
BIODEGRADABILITY
Measure of a lubricants ability to readily degrade under the force of naturally occurring micro-organisms.
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 breakdown molecules for sustenance. Certain chemical structures are more susceptible to microbial breakdown than others; vegetable oils, for example, will biodegrade more rapidly than petroleum oils.
BITUMEN
Also called asphalt or tar, bitumen is the brown or black viscous residue from the vacuum distillation of crude petroleum. It also occurs in nature as asphalt “lakes” and “tar sands.” It consists of high molecular weight hydrocarbons and minor amounts of sulfur and nitrogen compounds.
BLACK OILS
Lubricants containing asphaltic materials, which impart extra adhesiveness, that are used for open gears and steel cables.
BLEEDING / BLEED RATE
Separation of oil from grease structure. A certain amount of bleeding is desirable in greases since it tends to provide continuous oil lubrication to bearings.
BLOCKED PENETRATION
Is the penetration of a grease block (hard enough to hold its shape without a container).
BLOWBY
Passage of unburned fuel and combustion gases past the piston rings of internal combustion engines, resulting in fuel dilution and contamination of the crankcase oil.
BOILING POINT
The temperature at which a substance boils or is converted into vapor by bubbles forming within the liquid; it varies with pressure.
BOILING RANGE
For a mixture of substances, such as a petroleum fraction, the temperature interval between the initial and final boiling points.
BOMB OXIDATION
A test for the oxidation stability of a product obtained by sealing it in a closed container (Bomb) with pressurized oxygen.
BOUNDARY LUBRICATION
A form of lubrication between two rubbing surfaces without development of a full-fluid lubricating film. Boundary lubrication can be made more effective by including additives in the lubricating oil that provide a stronger oil film, thus preventing excessive friction and possible scoring. There are varying degrees of boundary lubrication, depending on the severity of service. For mild conditions, oiliness agents may be used; by plating out on metal surfaces in a thin but durable film, oiliness agents prevent scoring under some conditions that are too severe for a straight mineral oil. Compounded oils, which are formulated with polar fatty oils, are sometimes used for this purpose. Anti-wear additives are commonly used in more severe boundary lubrication applications. The more severe cases of boundary lubrication are defined as extreme pressure conditions; they are met with lubricants containing EP additives that prevent sliding surfaces from fusing together at high local temperatures and pressures.
BOYLE’S LAW
The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system. Mathematically, Boyle’s law can be stated as:
or
where P is the pressure of the gas, V is the volume of the gas, and k is a constant.
Boyle’s law states that when the temperature of a given mass of confined gas is constant, the product of its pressure and volume is also constant. When comparing the same substance under two different sets of conditions, the law can be expressed as:
showing that as volume increases, the pressure of a gas decreases proportionally, and vice versa.
BRANCHED PARAFFIN
Common molecule form for a mineral oil base stock.
BREAKDOWN MAINTENANCE
Maintenance performed after a machine has failed to return it to an operating state.
BRIDGING
A condition of filter element loading in which contaminant spans the space between adjacent sections of a filter element, thus blocking a portion of the useful filtration.
BRIGHT STOCK
A heavy residual lubricant stock with low pour point, used in finished blends to provide good bearing film strength, prevent scuffing, and reduce oil consumption. Usually identified by its viscosity, SUS at 210°F or cSt at 100°C.
BRINELLING
Permanent deformation of the bearing surfaces where the rollers (or balls) contact the races. Brinelling 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
Apparent viscosity in cP determined by Brookfield viscometer, which measures the torque required to rotate a spindle at constant speed in oil of a given temperature. Basis for ASTM Method D 2983; used for measuring low temperature viscosity of lubricants.
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
Material passed into the effluent stream composed of foreign materials incorporated into the filter medium.
BULK MODULUS (of elasticity)
A ratio of normal stress to a change in volume, also a term used in determining the compressibility of a fluid. Data for petroleum products can be found in the International Critical Tables.
BUNA-N
Buna-N is a copolymer of butadiene and acetonitrile.
BURST PRESSURE RATING
The maximum specified inside-out differential pressure that can be applied to a filter element without outward structural or filter-medium failure.
BUSHING
A short, extremely threaded connector with a smaller size internal thread.
BYPASS FILTRATION
A system of filtration in which only a portion of the total flow of a circulating fluid system passes through a filter at any instant or in which a filter having its own circulating pump operates in parallel to the main flow.
BYPASS VALVE (RELIEF VALVE)
A valve mechanism that assures system fluid flow when a preselected differential pressure across the filter element is exceeded; the valve allows all or part of the flow to bypass the filter element.
CAFE
Corporate Average Fuel Economy
CAMS
Eccentric shafts are used in most internal combustion engines to open and close valves.
CAPACITY
The amount of contaminants a filter will hold before an excessive pressure drop is caused. Most filters have bypass valves which open when a filter reaches its rated capacity.
CAPILLARITY
A property of a solid-liquid system manifested by the tendency of the liquid in contact with the solid to rise above or fall below the level of the surrounding liquid; this phenomenon is seen in a smallbore (capillary) tube.
CAPILLARY VISCOMETER
A viscometer in which the oil flows through a capillary tube.
CARBON
A non-metallic element – No. 6 in the periodic table. Diamonds and graphite are pure forms of carbon. Carbon is a constituent of all organic compounds. It also occurs in combined form in many inorganic substances; i.e., carbon dioxide, limestone, etc.
CARBON (DEPOSIT)
Solid black residue in piston grooves which can interfere with piton ring movement leading to wear and/or loss of power.
CARBON RESIDUE
Coked material remaining after an oil has been exposed to high temperatures under controlled conditions.
CARBONYL IRON POWDER
A contaminant which consists of up to 99.5% pure iron spheres.
CASE DRAIN FILTER
A filter located in a line conducting fluid from a pump or motor housing to reservoir.
CASE DRAIN LINE
A line conducting fluid from a component housing to the reservoir.
CARTRIDGE SEAL
A completely self-contained assembly including seal, gland, sleeve, mating ring, etc., usually needing no installation measurement.
CATALYST
A substance which speeds a chemical action without undergoing a chemical change itself during the process. Now used in catalytic converters to control amount of unburned hydrocarbons and CO in automobile exhaust.
CATALYTIC CONVERTER
An integral 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 — sudden, unexpected failure of a machine resulting in considerable cost and downtime.
CATALYTIC HYDROGENATION
Refining station where hydrogen atoms are fixed to molecules through a combination of pressure, temperature, and a catalyst bed (chemical accelerator).
CAVITATION
Formation of an air or vapor pocket (or bubble) due to lowering of pressure in a liquid, often as a result of a solid body, such as a propeller or piston, moving through the liquid; also, the pitting or wearing away of a solid surface as a result of the collapse of a vapor bubble. Cavitation can occur in a hydraulic system as a result of low fluid levels that draw air into the system, producing tiny bubbles that expand explosively at the pump outlet, causing metal erosion and eventual pump destruction.
CAVITATION EROSION
A material-damaging process which occurs as a result of vaporous cavitation. “Cavitation” refers to the occurrence or formation of gas- or vapor- filled pockets in flowing liquids due to 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 caused by the collapse of the vapor bubbles produce deformation, material failure and, finally, erosion of the surfaces.
CELLULOSE MEDIA
A filter material made from plant fibers. Because cellulose is a natural material, its fibers are rough in texture and vary in size and shape. Compared to synthetic media, these characteristics create a higher restriction to the flow of fluids.
CENTIPOISE (CP)
A unit of absolute viscosity. 1 centipoise = 0.01 poise.
CENTISTOKE (CST)
A unit of kinematic viscosity. 1 centistoke = 0.01 stoke.
CENTRALIZED LUBRICATION
A system of lubrication in which a metered amount of lubricant or lubricants for the bearing surfaces of a machine or group of machines are supplied 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 accelerating the fluid mechanically in a circular path and using the radial acceleration component to isolate these contaminants.
CERTIFIED LUBRICATION SPECIALIST (CLS)
Certification as set forth by STLE. CMRP- Certified Maintenance and Reliability Professional as set forth by SMRP.
CHANNELING
The phenomenon observed among gear lubricants and greases when they thicken due to cold weather or other causes, to such an extent that a groove is formed through which the part to be lubricated moves without actually coming in full contact with the lubricant.
CHEMICAL STABILITY
The tendency of a substance or mixture to resist chemical change.
CHELATING AGENT
Class of chemicals that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale.
CHIP CONTROL (Grit control, Last-chance) FILTER
A filter intended to prevent only large particles from entering a component immediately downstream.
CIRCULATING LUBRICATION
A 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 SYSTEM
A lubricating system in which oil is recirculated from a central sump to the parts requiring lubrication and then returned to the sump.
CLAY FILTRATION
A refining process using Fuller’s Earth (activated clay), bauxite or other minerals to absorb minute solids from lubricating oil, as well as remove traces of water, acids, and polar compounds.
CLEANABLE
A filter element which, when loaded, can be restored by a suitable process, to an acceptable percentage of its original dirt capacity.
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 by special facilities and operating processes and by trained personnel.
CLEANABLE FILTER
A filter element which, when loaded, can be restored by a suitable process, to an acceptable percentage of its original dirt capacity.
CLEANLINESS LEVEL (CL)
A measure of relative freedom from contaminants.
CLEARANCE BEARING
A journal bearing in which the radius of the bearing surface is greater than the radius of the journal surface.
CLOUD POINT
The temperature at which waxy crystals in an oil or fuel form a cloudy appearance.
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.
COEFFICIENT OF FRICTION
The number obtained by dividing the friction force resisting motion between two bodies by the normal force pressing the bodies together.
COHESION
That property of a substance that causes it to resist being pulled apart by mechanical means.
COKING
The undesirable accumulation of carbon (coke) deposits in the internal combustion engine or in a refinery plant.
COLD CRANKING SIMULATOR (CCS)
An intermediate shear rate viscometer that predicts the ability of an oil to permit a satisfactory cranking speed to be developed 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 resistance to flow.
COLLAPSE PRESSURE
The minimum differential pressure that an element is designed to withstand without permanent deformation.
COLORIMETRIC METHOD for ACID MEASUREMENT
Under the colorimetric method for determining neut number (ASTM D 974), end point is identified by the change of a color indicator. This indicator exhibits one color above a specified pH value, another below. By this means, a total acid or strong base number can be determined with a p-naphtholbenzene indicator, while a strong acid number can be determined with a methyl orange indicator. Obviously, however, this method is not suitable for the investigation of dark-colored liquids.
COMPATIBILITY
Measure of the degree that two or more lubricants can be mixed without the loss of performance or acceleration of harmful chemical reactions, leading to the destruction of the lubricant.
COMPLEX GREASE
A lubricating grease thickened by a complex soap. Complex soaps are created through the use of two organic acids (instead of one) and a metallic hydroxide. Complex greases typically have 500°F + dropping points.
COMPOUND
(1) Chemically speaking, a distinct 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 combining elements. (2) In petroleum processing, generally connotes fatty oils and similar materials foreign to petroleum added to lubricants to impart special properties.
COMPOUNDED OIL
A petroleum oil to which has been added other chemical substances.
COMPOUNDING
The addition of fatty oils and similar materials to lubricants to impart special properties. Lubricating oils to which such materials have been added are known as compounded oils.
COMPRESSED AIR
Air at any pressure greater than atmospheric pressure.
COMPRESSOR
A device which converts mechanical force and motion into pneumatic fluid power.
CONSISTENCY
The degree to which lubricating grease resists deformation under the application of force. (See ASTM D 217) Sometimes used to qualitatively to denote viscosity of liquids. (See NLGI and worked penetration).
CONDITION BASED MAINTENANCE
Maintenance strategy where maintenance activities are planned around changing equipment health conditions.
CONTAMINANT
Any foreign or unwanted substance that can have a negative effect on system operation, life or reliability.
CONTAMINANT FAILURE
Any loss of performance due to the presence of contamination. Three basic types of contamination failure are: Degradation, Transient, and Catastrophic.
CONTAMINANT LOCK
A particle or fiber-induced jam caused by solid contaminants.
CONTAMINATION
Any substance in the oil that does not belong there. The most common contaminates include particles, water, air, fuel, soot, and even the incorrect lubricant.
CONTAMINATION CONTROL
Proactive condition management activity wherein all contaminants (liquid, solid, and gaseous) are prohibited from interaction with the targeted system. 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.
COPPER STRIP CORROSION
The gradual eating away of copper surfaces as the result of oxidation caused by acids or other corrosive agents.
CORRECTIVE MAINTENANCE (CM)
see Reactive Maintenance.
CORROSION
The decay and loss of a metal due to 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 combines (or compound) form.
CORROSION INHIBITORS
Additive for protecting lubricated metal surfaces against chemical attack 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.
CORROSIVE WEAR
Removal of materials by degradation due to chemical reaction. CP- Centipoise.
CRACKLE TEST
A method for detecting water in oils. A few drops of oil are put on a hot plate set to 425°F. If the drops pop or crackle, then water is deemed present. Generally, this indicates water somewhere near 200ppm or greater.
CRANKCASE OIL
Lubricant used in the crankcase of the internal combustion engine.
CRUDE OIL
The basic (primary) raw material used in the manufacturing of hydrocarbon compounds.
CST
Centistoke
CYCLIC FATIGUE
Fatigue caused by repetitive loading-unloading stresses to a metal surface.
CYLINDER
A device which converts fluid power into linear mechanical force and motion. It usually consists of a moveable element such as a piston and piston rod, plunger, or ram, operating within a cylindrical bore.
CYLINDER OIL
A lubricant for independently lubricated cylinders, such as those of steam engines and air compressors; also, for lubrication of valves and other elements in the cylinder area. Steam cylinder oils are available in a range of grades with high viscosities to compensate for the thinning effect of high temperatures; of these, the heavier grades are formulated for super-heated and high-pressure steam, and the less heavy grades for wet, saturated, or low-pressure steam. Some grades are compounded for service in excessive moisture; see compounded oil. Cylinder oils lubricate on a once-through basis.
DEAERATOR
A separator that removes air from the system fluid through the application of bubble dynamics.
DEFECT ELIMINATION
A systematic process of eliminating the underlying factors (root causes) that lead to system failure.
DEFOAMANT
An additive (typically silicone based) used to help separate entrained air (bubbles) from bulk oil.
DEGAS
Removing air from a liquid, usually by ultrasonic and/or vacuum methods.
DEGRADATION
Gradual decay. Associated with slow but persistent failure of machine or lubricant health.
DEHYDRATOR
A separator that removes water from the system fluid.
DELAMINATION WEAR
A complex wear process where a machine surface is peeled away or otherwise removed by forces of another surface acting on it in a sliding motion.
DEMULSIBILITY
The ability of an oil to separate from water after it has been thoroughly mixed. Typically quantified by ASTM D 1401 or D 2711.
DEMULSIFIER
An additive that promotes oil-water separation in lubricants that are exposed to water or steam.
DEPTH FILTER
A filter medium that retains contaminants primarily within tortious passages.
DESORPTION
Opposite of absorption or adsorption. In filtration, it relates to the downstream release of particles previously retained by the filter.
DETECTION FREQUENCY
Cycle or frequency for which a condition-based measurement method is executed for a given machine or component.
DETERGENT
In lubrication, either an additive or a compounded lubricant having the property of keeping insoluble matter in suspension thus preventing its depositing where it could be harmful. A detergent may also re-disperse deposits already formed.
DETERGENT OIL
Characteristic of either an additive or a compounded lubricant (having the property of) keeping insoluble matter in suspension thus preventing its depositing where it would be harmful. A detergent may also re-disperse deposits already formed.
DEWAXING
Removal of paraffin wax from lubricating oils to improve the low temperature characteristics.
DIESTERS
A type of synthetic lubricant base stock made from a reaction between an acid and an alcohol. This base stock is made from non-petroleum materials.
DIFFERENTAIL PRESSURE INDICATOR
An indicator which signals the difference in pressure between two points, typically between the upstream and downstream sides of a filter element.
DIFFERENTIAL PRESSURE RELIEF VALVE
A valve whose primary function is to limit differential pressure.
DIRECTIONAL CONTROL VALVE
A valve whose primary function is to direct or prevent flow through selected passages.
DIRECTIONAL CONTROL VALVE (SERVO)
A directional control valve which modulates flow or pressure as a function of its input signal.
DISPERSANTS
In lubrication, a term usually used interchangeably with detergents, an additive, usually nonmetallic (“ashless”), which keeps fine particles of insoluble materials in a homogenous solution, which prevents particles from settling out and accumulating.
DISSOLVED AIR
Air dispersed in oil to form a mixture and not readily drawn out of solution. Petroleum oils contain as much as 12% dissolved air.
DISSOLVED GASES
Those gases that enter into solution with a fluid and are neither free nor entrained gases.
DISSOLVED WATER
Water dispersed throughout the oil by individual water molecules, unrecognizable visually. Most oils can hold 200-600 ppm in dissolved state, depending on type, temperature, and age of the oil.
DISTILLATE
Cut or fraction taken from a distillation tower having a viscosity suitable for lubricant manufacturer.
DISTILLATION
The primary refining step, in which the crude is separated into various boiling range fractions in a distillation tower.
DN FACTOR
Also known as speed factor. Determined by multiplying the bore of a rolling element bearing by the RPM of the journal. DN can be used, in conjunction with operating temperature, to help determine the appropriate viscosity or the NLGI grade to be applied.
DOUBLE SEAL
Two mechanical seals designed to permit a liquid or gas barrier fluid between the seals mounted back-to-back or face-to-face.
DRIP FEED OILER
Also called Drop Feed Oiler. Device for once through lubrication, whereby the drip feed oiler delivers oil from the bottom of a reservoir to an application one drop at a time, with flow rate controlled by a needle valve at the top of the reservoir.
DROP TUBE SAMPLING
Method of pulling an oil sample by inserting a tube into a fill port or dipstick port and lowering the tube into the oil below. A small manual vacuum pump is used to extract the oil. While several issues make this not the best practice, it is very common especially in less sophisticated programs.
DROPPING POINT
The temperature at which a drop of material falls from the orifice of the test apparatus under the conditions of ASTM D 566-42. Not to be confused with “melting point”. Grease softens gradually over a wide temperature range; there is no abrupt melting. Dropping point is useful in determining a general operating temperature limit. Rule of thumb apply to 70°F below dropping point.
DRY SUMP
A machine design in which oil is retained in a vessel below the lubricated components. The lubricant is re-supplied under force by a pump system to maintain effective oil supply.
DUAL-LINE SYSTEM
A positive displacement terminating (oil or grease) lubrication system that employs two main lines supplied from a pump connected to a 2-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 dispensing lubricant to one group of lube points. Switching the 2-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 dispensing lubricant to a second group of lube points. The system is also called a parallel system. Each dual-line valve operates independently of any other in the system.
DUPLEX FILTER
An assembly of two filters with valving for selection of both filters.
DYNAMIC SEAL
A seal that moves due to axial or radial movement of the unit.
ELASTIC DEFORMATION
aka; Plastic Deformation. A phenomenon whereby the surfaces of rotating elements in contact, such as rolling element bearings and gear teeth, tend to deform slightly. As the metal surfaces deform somewhat, sub surface fatigue cracks may develop.
ELASTOHYDRODYNAMIC (EHD) LUBRICATION
Lubrication phenomenon occurring during elastic deformation of two non-conforming surfaces under high load. A high load carried by a small area causes a temporary (but significant) increase in lubricant viscosity as the lubricant is momentarily trapped between the slightly deformed opposing surface.
ELASTOMER
A rubber or rubber-like material, both natural and synthetic, used in making a wide variety of products, such as seals and hoses. In oil seals, an elastomer’s chemical composition is a factor in determining its compatibility with a lubricant.
ELECTROSTATIC SEPARATOR
A separator that removes contaminant from fluids by applying an electrical charge to the contaminant that is then attracted to a collection device of different electrical charge.
ELEMENT (CARTRIDGE)
The porous device that performs the actual process of filtration.
EMULIFIED WATER
Water suspended in oil in microscopic droplets after the saturation point has been reached. Often seen as cloudy or milky appearing oil.
EMULSION
An intimate mixture of oil and water – generally milky appearance. Can be desirable or undesirable depending on the application. 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).
ENTRAINED AIR
Minute bubbles in oil in a colloidal-like suspension giving the oil a cloudy or hazy appearance. Entrained air can disrupt or weaken the lubricating film and lead to excessive wear. The compressibility of the entrained air may also cause erratic and inefficient hydraulic operations.
ENVIRONMENTAL CONTAMINANT
All material and energy present in and around an operating system, such as dust, air moisture, chemicals, and thermal energy.
EROSIVE WEAR
Wear caused by particle impingement at high velocities or by cavitation, progressively removing machine surface.
EROSION
The progressive removal of a machine surface by cavitation or by particle impingement at high velocities.
ETHYLENE OXIDE
A raw material component used to manufacture Polyethylene Glycol (PAG) synthetic base stock.
EVAPORATION
Loss of liquid through conversion to gas phase. Light hydrocarbons tend to evaporate from the surfaces of hot lubricant sumps, eventually leading to viscosity thickening.
EXTREME PRESSURE (EP)
Lubricants that impart to rubbing surfaces the ability to carry appreciably greater loads than would be possible with ordinary lubricants without excessive wear or damage.
EXTREME PRESSURE (EP) ADDITIVE
Additive that reduces adhesive wear under extreme pressures situations. EP additives react with the metal and localized high temperatures to form a sacrificial surface film to prevent the welding of asperities. Many of the reactive compounds (primarily sulfur or phosphorus) used may react too strongly to be used with yellow metals.
EXTREME PRESSURE AGENT
Lubricant additive that prevents sliding metal surfaces from seizing under conditions of extreme pressure. 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 consequent scoring that is destructive to sliding surfaces under high loads. Reactive compounds of sulfur, phosphorus, inorganic metals, and chlorine are used to form these inorganic films.
EXTREME PRESSURE (EP) LUBRICANTS
Oils or greases to which EP agents have been added to impart load carrying or anti-weld qualities. Normally, an EP lubricant has a Timken O.K. Load of 35 lbs. or higher. Equipment manuals will often specify the use of EP grease, EP gear oil, or EP Industrial Oil.
FACE SEAL
A device that prevents 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.
FAILURE MODES EFFECTS ANALYSIS (FMEA)
Analytical process designed to show the relationship between failure states (failure mode) and their manifested final conditions. Also known as FMEA.
FALEX EP TEST
Test designed to measure the EP characteristics of a lubricant under sliding frictional conditions. Consists of a rotating pin held in a V-block while submerged in oil. The load is gradually increased on the pin until the pin breaks or seizes.
FATIGUE WEAR
Wear caused by repetitive stress. Often this wear starts as sub-surface micro-pitting.
FERROPGRAPHY
Particle analysis using magnetism to separate ferrous material to evaluate. Direct reading ferrography and Analytical ferrography are two common types.
FIBER GREASE
A grease with a distinctly fibrous structure, which is noticeable when portions of the grease are pulled apart.
FILM STRENGTH
The ability of a film of lubricant to resist rupture due to load, speed, and temperature.
FILTER
Any device or porous substance used as a strainer for cleaning fluids by removing suspended matter.
FILTERABILITY
Measure of filter-clogging tendency caused by resident particles or precipitates within a new, clean lubricant.
FILTER HEAD
An end closure for the filter case or bowl that contains one or more ports.
FILTER HOUSING
A ported enclosure that directs the flow of fluid through the filter element.
FILTER LIFE TEST
A 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 may be expressed as test time required to reach terminal conditions at a specified contaminant addition rate.
FILTER MEDIA (DEPTH)
Porous materials which retain contaminants within a tortuous path, performing the actual process of filtration.
FILTER MEDIA (SURFACE)
Porous materials which retain contaminants on the influent face, performing the actual process of filtration.
FILTRATION
The physical or mechanical process of separating insoluble particulate matter from a fluid, such as air liquid, by passing the fluid through a filter medium that will not allow the particulates to pass through it.
FIRE POINT (CLEVELAND OPEN CUP)
The temperature at which a combustible liquid must be heated so that the released vapor will burn continuously when ignited under specified conditions. (See ASTM D 92).
FIRE-RESISTANT FLUID
Lubricant used especially 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 of low volatility, such as phosphate esters, silicones, and halogenated hydrocarbon-type fluids.
FIXED DISPLACEMENT PUMP
A pump in which the displacement per cycle cannot be varied.
FLASH POINT (CLEVELAND OPEN CUP)
The temperature to which a combustible liquid must be heated to give off sufficient vapor to form momentarily a flammable mixture with air when a small flame is applied under specified conditions. (ASTM D 92 – Cleveland Open Cup)
FLOW CONTROL VALVE
A valve whose primary function is to control flow rate.
FLUID FRICTION
Friction due to the viscosity of the fluid – internal friction. Molecular resistance to motion of fluids. The higher the viscosity, the more fluid friction. Also called viscous drag.
FLUID POWER
Energy transmitted and controlled through use of pressurized fluid.
FLUOROCARBONS
a class of refrigerant gases used in closed circuit refrigeration system. Also known as CFC’s were banned by the 1996 Montreal Protocol, with production to cease in 2030. Are divided into 3 classes, based on miscibility with mineral oils and other performance requirements.
FLUSHING
A fluid circulation process designed to remove contamination from the wetted surfaces of a fluid system.
FOAM INHIBITOR
A substance introduced in a very small proportion to a lubricant or a coolant to prevent the formation of foam due to aeration of the liquid, and to accelerate the dissipation of any foam that may form.
FOAMING
A frothy mixture of air and a petroleum product (e.g., lubricant, fuel oil, etc.) that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. Foaming can result from excessive agitation, improper fluid levels, air leaks, cavitation, or contamination with water or other foreign materials. 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, based on ASTM D 892 test method.
FOUR-BALL EP TEST
A test designed to measure the EP performance of a lubricant under extremely high loading conditions.
FOUR-BALL WEAR TEST
The name is frequently used to describe either of two similar laboratory machines, The Four-Ball Wear Tester. These machines are used to evaluate a lubricant’s anti-wear qualities, frictional characteristics or load carrying capabilities. It derives its name from the four ½” steel balls used as test specimens. Three of the balls are held together in a cup filled with lubricant while the fourth ball is rotated against them.
FOOD GRADE
Lubricant suitable for use in food processing plants and applications. The H1, H2, and H3 designations were created by the USDA and are based on the likeliness the lubricant will contact the food with approval and registration dependent on the ingredients used in the formulation. FORCE- Any interaction that, when unopposed, will change the motion of an object.
FORCE FEED LUBRICATION
A system of lubrication in which the lubricant is supplied to the bearing surface under pressure.
FORMULATION
A ‘recipe’ for a given type of lubricant.
FREE WATER
That water in an oil reservoir that is separated, and normally below, the oil depending on the fluid’s specific gravity.
FRETTING
A form of wear resulting from small amplitude vibrations and oscillations. Fretting is a common issue in stored equipment.
FRICTION
A resistance to motion between two surfaces in contact.
FULL FILM LUBRICATION
see Hydrodynamic Lubrication GREASE- A lubricant composed of an oil, emulsified, and thickened with soap or other material to semisolid consistency.
FULL-FLOW FILTER
A filter that, under specified conditions, filters all influent flow.
FULL-FLOW FILTRATION
A system of filtration in which the total flow of a circulating fluid system passes through a filter.
FZG TEST (Four Square Gear Test)
A German gear test for evaluating EP properties through systematic increases in loading on a set of green (untreated) gears. This test depicts the relative performance of various greases to perform under conditions similar to the actual mechanical loading conditions to which lubricants are exposed.
GASEOUS CAVITATION
Cavitation caused by (generally) phase change from dissolved to gaseous vapor in low pressure circuits.
GEAR
A machine part which transmits 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. These are all examples of Class I gears.
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 used necessary to maintain effective lubrication. This is an example of a Class II gear.
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 axles of hypoid gears introduces additional sliding between the teeth, which, when combined with high loads, requires a high-quality EP oil. This is an example of a Class III gear.
GEAR OIL
A high-quality oil with 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, steel gear sets are encountered.
GEARBOX
A casing for gear sets that transmit power from one rotating shaft to another. A gear box has a number of functions: it is precisely bored to control gear and shaft alignment, it contains the gear oil, and it protects gears and lubricants from water, dust, and other environmental contaminants. Gear boxes are used in a wide range of industrial, automotive, and home machinery. Not all gears are enclosed in gear boxes; some are open to the environment and are commonly lubricated by highly adhesive greases.
GRAPHITE
A crystalline form of carbon having a laminar structure, which is used as a lubricant. It may be of natural or synthetic origin.
GRAVIMETRIC ANALYSIS
A method of analysis whereby the dry weight of contaminant per unit volume of fluid can be measured showing the degree of contamination in terms of milligrams of contaminant per liter of fluid.
GRAVITY
See Specific Gravity, API Gravity.
GREASE
A lubricant composed of an oil or oils thickened with soap, soaps, or other thickener to a semi-solid or solid consistency.
HEAT EXCHANGER
A device which transfers heat through a conducting wall from one fluid to another.
HOUSING
A ported enclosure which directs the flow of fluid through the filter element.
HYDRAULIC FLUID
Fluid serving as the power transmission medium in a hydraulic system. The most commonly used fluids are petroleum oils, synthetic lubricants, oil-water emulsions, and water-glycol mixtures. The principal requirements of a premium hydraulic fluid are proper viscosity, high viscosity index, anti-wear protection (if needed), good oxidation stability, adequate poor point, good demulsibility, rust inhibition, resistance to foaming, and compatibility with seal materials. Anti-wear oils are frequently used in compact, high-pressure, and capacity pumps that require extra lubrication protection.
HYDRAULIC MOTOR
A device which converts hydraulic fluid power into mechanical force and motion by transfer of flow under pressure. It is usually provided by rotary mechanical motion.
HYDRAULIC OIL
An oil especially suited for use as a power transmission medium in hydraulically operated equipment.
HYDRAULIC PUMP
A device which converts mechanical force and motion into hydraulic fluid power by means of producing flow.
HYDRAULIC SYSTEM
A system designed to transmit power through a liquid medium, permitting multiplication of force in accordance with Pascal’s Law, which states 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 hold 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 return 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
Engineering science pertaining to liquid pressure and flow.
HYDROCARBONS
Chemical compounds of hydrogen and carbon. Carbon atoms form the skeleton of the hydrocarbon molecule. Three principal petroleum types exist from crude: paraffins, naphthenes, and aromatics. Aromatics are more reactive as they are unsaturated molecules.
HYDROCRACKING
Processing method that requires more severe conditions for hydro processing to convert aromatics and naphthenes and linear and branched paraffins.
HYDRODYNAMIC LUBRICATION
The lubrication regime where the oils film thickness is greater than the machine’s composite surface roughness, Lambda (£) > 3. Condition of no metal-to-metal contact. Film thickness will be proportional Micelle to the viscosity and speed, and inversely proportional to load.
HYDROFINISHING
A process for treating raw extracted base stocks with hydrogen to saturate them for improved stability.
HYDROLYSIS
Degradation of base oil due to the presence of water. A breakdown process that occurs in anhydrous hydraulic fluids as a result of chemical reaction to heat, water, and metal catalysts (iron, steel, copper, etc.) with water being the central influence.
HYDROLYTIC STABILITY
Ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water.
HYDROMETER
An instrument for determining either the specific gravity of a liquid or the API gravity.
HYDROPEROXIDE
Reactive hydrocarbon produced through chemical change of stable hydrocarbons during the process of oxidation.
HYDROPHILIC
Compounds with an affinity for water.
HYDROPHOBIC
Compounds that repel water.
HYDROSTATIC LUBRICATION
A system of lubrication in which the lubricant is supplied under sufficient external pressure to separate the opposing surfaces by a fluid film.
HYPOID GEAR LUBRICANT
A gear lubricant having extreme pressure characteristics for use with a hypoid type of gear as in the differential of an automobile.
HYPOID GEARS
Gears in which the pinion axis intersects the plane of the ring gear at a point below the ring-gear axle and above the outer edge of the ring gear, or above the ring-gear axle and below the outer edge of the ring gear.
ILSAC
The International Lubricant Standardization and Approval Committee (ILSAC) is a joint committee of AAMA and JAMA members that assists in the development of new minimum oil performance standards.
IMPURITY
Anything that doesn’t belong in the lubricant.
INCOMPATIBILITY
Two lubricating greases show incompatibility when a mixture of the two shows physical properties or service performance markedly inferior to those of either of the greases before mixing.
INGRESSION LEVEL
Particles added per unit of circulating fluid volume.
INHIBITOR
A substance (additive) which slows or prevents chemical reactions, such as oxidation or corrosion.
IN-LINE FILTER
A filter assembly in which the inlet, outlet and filter element axis are in a straight line.
INSIDE-MOUNTED SEAL
A mechanical seal located inside the seal chamber with the pumped product’s pressure as its OD.
INSOLUBLES
Particles of carbon or agglomerates of carbon and other material, generally created by combustion and oxidation/chemical degradation of the lubricant.
INTERCOOLER
A device which cools a gas between the compressive steps of a multiple stage compressor.
INTERFACIAL TENSION (IFT)
The energy per unit area present at the boundary of two immiscible liquids. It is usually expressed in dynes/cm (ASTM Designation D 971).
INTERNATIONAL COUNCIL for MACHINERY LUBRICATION (ICML)
Organization dedicated to helping lubrication practitioners succeed in their careers. Certification options include MLA (1-3), MLT (1-2), and LLA (1-2).
INVERT EMULSION
A water in oil lubricant mixture, often used to create fire resistance hydraulic oils and various metal process fluids.
ISO
International Standards Organization, sets viscosity reference scales.
ISO GRADE
International Organization for Standardization Viscosity Grade. A measure of kinematic viscosity at 40°C. Each ISO grade corresponds to the midpoint of a viscosity range expressed in centistokes(cSt), with a defined viscosity tolerance range of +- 10%.
ISO SOLID CONTAMINATION CODE (ISO 4406-99)
A code assigned on the basis of the number of particles per unit volume greater than 4, 6, and 14 micrometers in size. Range numbers identify each increment of the particle population for a spectrum of levels.
JOURNAL BEARING
A sliding type of bearing having either rotating or oscillatory motion and in conjunction with which a journal operates.
KARL FISCHER TITRATION TEST
A test to measure the water content (in ppm) in oils, ASTM D1744 & D4928. Widely considered the most accurate test for water quantification and measure all phases of water in oil (dissolved, emulsified, and free).
KINEMATIC VISCOSITY
Noted as the time required for a fixed amount of oil to flow through a capillary tube under 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. ASTM D 3448.
L10 LIFE- L 10
The life that 90% of bearings should be expected to achieve for a given application and conditions.
LACQUER
A deposit resulting from the oxidation and polymerization of fuels and lubricants when exposed to high temperatures. Like, but harder, than varnish.
LAMINAR PARTICLES
Particles generated in rolling element bearings which have been flattened out by rolling contact.
LOAD-CARRYING CAPACITY
The 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 failure or excessive wear.
LOAD-WEAR INDEX (LWI)
Measure of the relatively 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.
LUBRICANT
Any substance, interposed between two surfaces in relative motion, which reduces the friction or wear of the surfaces. MICRON- Measurement of length commonly used when referring to particle size. 25,400 microns equal to 1 inch.
LUBRICATION
The control of friction and wear by the introduction of a fiction-reducing film between moving surfaces in contact. The lubricant used can be a fluid, solid, or plastic substance.
LUBRICATOR
A device which adds controlled or metered amounts of lubricant into a pneumatic system.
LUBRICITY
Ability of an oil or grease to lubricate; also called film strength.
MAGNETIC FILTER
A filter element that, in addition to its filter medium, has a magnet or magnets incorporated into its structure to attract and hold ferromagnetic particles.
MAGNETIC PLUG
A magnet that is strategically located in the flow stream to collect a representative sample of ferro-magnetic wear debris circulating in the system, which reflects degradation of critical surfaces.
MEDIUM
The porous material that performs the actual process of filtration. The plural of this word is “media”.
METAL SOAP
Thickening agent used to stiffen lubrication oils in grease formulation. Composed of a metal ion, a fatty compound, and an acid.
METALLOPHILLIC
Having an affinity for metal surfaces.
MICELLE
A loosely bound aggregation of atoms, ions (electrically charged atoms), or molecules, forming a colloidal particle – i.e., one of several ultramicroscopic particles dispersed through some continuous medium.
MICROMETER (µm)
See Micron.
MICRON
A unit of length, also known as a micrometer. One Micron = 39 millionths of an inch (.000039”). Contaminant size is usually described in microns (µm). Many hydraulic filters are required to be efficient in capturing a substantial percentage of contaminant particles as small as 5µm.
MINERAL OIL
Oil derived from a mineral source, such as petroleum, as opposed to oils that are synthesized or derived from plants and animals. In the API base oil classification system, Group I, Group II, or Group III, depending on how finely refined.
MISCIBLE
Fluids that may be mixed in any concentration without separation of phases, e.g., water and ethyl alcohol are miscible.
MIXED FILM LUBRICATION
Lubrication regime where the oil carries most of the load but asperities come in contact. Lambda = 1-3 MLT- Machinery Lubrication Technician. A certification, with multiple levels, as set forth by the standards by ICML.
MOLYBDENUM DISULPHIDE
A black, lustrous powder (MoS2) that serves as a dry-film lubricant in certain high-temperature and high-0vacuum applications. It is also used in the form of pastes to prevent scoring when assembling press-fit parts, and as an additive to impart residual lubrication properties to oils and greases. Molybdenum disulfide is often called moly or moly disulfide.
MOTOR CURRENT ANALYSIS (MCA)
Form of electrical motor condition measurement that is based on collection and analysis of discrete frequencies of vibration energy produced by variations in motor electrical conditions.
MULTIGRADE OIL
An oil meeting the requirements of more than one SAE viscosity grade classification and may therefore be suitable for use over a wider temperature range than a monograde oil.
MULTIPASS TEST (RECIRCULATION)
Filter performance tests in which the contaminated fluid is allowed to recirculate through the filter for the duration of the test. Contaminant is usually added to the test fluid during the test. The test is used to determine the Beta-Ratio of an element.
NAPHTHENE
Hydrocarbon characterized by saturated carbon atoms in a ring structure. Naphthenic oils have low pour points and good solvency properties.
NAPHTHENIC
A type of petroleum fluid derived from naphthenic crude oil, containing a high proportion of closed-ring methylene groups.
NATURAL RUBBER
The rubber material obtained from the latex produced by certain plants and trees. Essentially cis-1, 4-polyisoprene. The only rubber of any commercial significance until the 1930s, and still one of the most important.
NEEDLE BEARING
A roller type bearing containing elements in the form of rollers which are relatively long compared with their diameter.
NEOPRENE
Chloroprene polymer synthetic rubber with high resistance to weather, chemicals, petroleum oil and heat.
NEUTRALIZATION NUMBER
A measure of the total acidity or basicity of an oil; this includes organic or inorganic acids or bases of a combination there of (ASTM Designation D974-58T).
NLGI
(National Lubricating Grease Institute) Trade association whose main interest is grease and grease technology. NLGI is best known for its system of rating greases by penetration.
NLGI NUMBER (PENETRATION NUMBER)
The National Lubricating Grease Institute (NLGI) established a simplified system for rating the consistency of grease (hardness). NLGI Grease grade ranges from 000 to 6.
NOMINAL FILTRATION RATING
The nominal rating refers to a filter capable of cutting off a nominated minimum percentage by weight of solid particles of a specific contaminant greater than a stated micron size, normally expressed in micrometers (mm).
NSF
National Sanitation Foundation – a public health and safety organization now responsible for the food grade classification system.
OBLITERATION
A synergistic phenomenon of 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 increases.
OEM
Original Equipment Manufacturer OSHA- Occupational Safety and Health Administration
OILER
A device for once-through lubrication. Three common types of oilers are: drip-feed, wick-feed, and bottle-feed; all depend on gravity to induce a metered flow of oil to the bearing. The drip-feed oiler delivers oil from the bottom of a reservoir to a bearing one drop at a time; flow rate is controlled by a needle valve at the top of the reservoir. In a wick-feed oiler, the oil flows through a wick due to capillary flow properties of the wick. In a bottle-feed oiler, a vacuum condition is created at the oil bulb, As the level in the sump declines air bubbles enter the bulb, the vacuum is reduced, and a small amount of oil enters the bearing or is added to the reservoir.
OILINESS AGENT
An additive, usually polar in nature, used to improve the lubricity of a mineral oil. Now usually called a boundary lubrication additive.
OIL RING
A loose ring floating on the surface of the shaft or journal. The ring dips into a reservoir of lubricant from which it carries the lubricant to the top of a bearing by its own rotation.
OLEOPHILLIC
Attracted to oil.
OPEN GEAR
A gear that is exposed to the environment, rather than being housed in a protective gear box. Open gears are generally large, heavily loaded, and slow moving. Open gears require viscous, adhesive lubricants that bond to the metal surfaces and resist run-off.
ORGANO-METALLIC SOAP
Thickening agent used to stiffen lubrication oils in grease formulation. Composed of a metal ion, a fatty compound, and an acid.
OVER BASED
Alkali condition created using a class of basic chemistry additives. Over based lubricants are used in motor and diesel engine oils.
OXIDATION
A chemical change involving, or precipitated by, oxygen reactions with petroleum fluids. The process is accelerated by heat, light, metal catalysts and the presence of water, acids, or solid contaminants. It leads to increased viscosity and deposit formation.
OXIDATION INHIBITOR
Substance added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or storage life; also called antioxidant. An oxidation inhibitor may work in one of three 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 (OXIDATIVE) STABILITY
The resistance of a lubricant to chemical reaction with oxygen. The absorption and reaction of oxygen may lead to deterioration of lubricants. So, oxidation stability increases effective lubricant service life.
PANEL COKER TEST
Test that involves dripping cold fluid onto a hot panel to determine the detergency and deposit-forming tendencies of the test fluid.
PARAFFIN
Any hydrocarbon identified 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.
PARETO
A method of organizing errors, problems, or defects to help focus on problem solving efforts; graphic way of identifying the few critical items as opposed to many less important ones.
PARALLEL SYSTEMS
Lubrication systems where the dispensing devices are connected to the main line parallel. Each dispensing device operates independent of any other in the system.
PARTICLE COUNT
The number of particles present greater than a particular micron size per unit volume of fluid often stated as particles >10 microns per milliliter.
PARTICEL DENSITY
An important parameter in establishing an entrained particle’s potential to impinge on control surfaces and cause erosion.
PARTICLE SCRUBBING
Process through which additives prone to attach to microscopic particles are literally stripped from the lubricant because of a very high population of particles.
PARTICULATES
Foreign matter in oil, typically meant as solids like dust, wear debris, soot, process material, etc.
PASCAL’S LAW
The principle of transmission of fluid pressure. States that pressure exerted anywhere in a confined incompressible fluid are transmitted equally in all directions such that the pressure remains the same.
PATCH TEST
A field level test that uses specific membrane filter material to recognize contamination presence and morphology (shape, color, size)
PENETRATION
is the consistency or hardness of a grease measured by the distance a standard cone will penetrate the surface by a free fall cone at a standard temperature.
PERMEABILITY
The relationship of flow per unit area to differential pressure across a filter medium.
P-F INTERVAL
The interval between the occurrence of a potential failure and its decay into a functional failure.
PHASE TRANSFORMATION
Process where matter changes from one state to another. Water evaporation is an example of phase transformation.
PHOSPHATE ESTER
Any group of synthetic lubricants having 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-resistance hydraulic fluid in high-temperature applications.
PITCH DIAMETER
Used to determine the linear velocity of bearing or gears (D +d)/2, or simply stated as the average diameter.
PINION
The smaller of two mating or meshing gears can be either the driving or the driven gear.
PISTON RINGS
Circular metallic elements that ride in the grooves of a piston and provide compression sealing during combustion. Also used to spread oil for lubrication.
PLAIN BEARING
Any simple sliding type bearing, as distinguished from ball or rolling type bearings.
PLASTIC DEFORMATION
Condition where metal surfaces deform under stress loads as though malleable (like plastic). Classic evidence of plastic flow can be found at the tips of heavily loaded gears in the form of a fine edge.
PLEATED FILTER
A filter element whose medium consists of a series of uniform folds and has the geometric form of a cylinder, cone, disc, plate, etc. Synonymous with “convoluted” and “corrugated”.
PNUEMATICS
Engineering science pertaining to gaseous pressure and flow.
PSI
Pounds per square inch.
PSIA
Pounds per square inch absolute. (PSIG + 14.696)
PSID
Pounds per square inch differential.
PSIG
Pounds per square inch gauge. (PSIA – 14.696)
POLARITY
The ability of the oil and or additives to properly wet the metal surface. Positively or negatively charged affinity. Polar affinity.
POLYGLYCOLS
Polymers of ethylene or propylene oxides used as a synthetic lubricant base. Properties include very good hydrolytic stability, high viscosity index (VI), and low volatility. Used particularly in water emulsion fluids.
POLYMER
A substance formed by the linkage (polymerization) of two or more simple molecules called monomers to form a single larger molecule having the same elements in the same proportions as the original monomers, i.e., each monomer retains its structural identity. A polymer may be liquid or solid; solid polymers may consist of millions or 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.
POLYOL ESTER
A synthetic lubricant base, formed by reacting fatty acids with a polyol (such as a glycol) derived from petroleum. 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 relatively simple olefins. Polyethylene and polyisoprene are important polyolefins.
PORE
A small channel or opening in a filter medium which allows passage of fluid.
PORE SIZE DISTRIBUTION
The ratio of the number of effective holes 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.
POTENTIOMETRIC
Method of determining an oil’s acidity (alkalinity) by measuring electric potential.
POUR POINT
Lowest temperature at which an oil or distillate fuel is observed to flow, when cooled under conditions prescribed by test method ASTM D 97. The pour point is 3°C (5°F) above the temperature at which the oil in a test vessel shows no movement when the container is held horizontally for five seconds. Used to help determine an oil’s suitability for low temperature service.
POUR POINT DEPRESANT
An additive which retards the adverse effects of wax crystallization and lowers a finished lubricant’s pour point.
PREDICTIVE MAINTENANCE (PdM)
A condition-based maintenance strategy emphasizing early prediction of failure utilizing non-destructive techniques (NDT) such as oil analysis, vibration monitoring, and thermography to identify incipient failures in advance.
PRESSURE CONTROL RELIEF VALVE
A pressure control valve whose primary function is to limit system pressure.
PRESSURE DROP
Resistance to flow created 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 differential above or below atmospheric pressure.
PRESSURE LINE FILTER
A filter located in a line conducting working fluid to a working device or devices.
PREVENTIVE MAINTENANCE (PM)
Maintenance Strategy whereby the practice is to repair, replace, or perform an activity based on historical or statistical representation of expected failure interval.
PROACTIVE MAINTENANCE (PaM)
Maintenance strategy to monitor equipment and/or lubricant condition for the purpose of directing corrective actions by detecting and eliminating the root causes of failure, such as high lubricant contaminant, misalignment and imbalance are among the most critical.
PROLONGED WORKED PENETRATION
grease that has been worked specified number of strokes (more than 60) and then brought back to 77°F then subjected to additional 60 double strokes in the grease worker.
PROPYLENE OXIDE
A raw material component used to manufacture Polypropylene Glycol (PAG) synthetic base stock.
PUMP
A device which converts mechanical force and motion into hydraulic fluid power.
PUMPABILITY
The ability of lubricating grease to flow under pressure through the line, nozzle, and fitting of a grease dispensing system. The low temperature, low shear stress-shear rate viscosity characteristics of an oil that permit satisfactory flow to and from the engine oil pump and subsequent lubrication of moving components.
R & O
Rust & Oxidation inhibited.
RADIAL LOAD
The force exerted perpendicular to the shaft. In a horizontal shaft, this normally includes the weight of the shaft and what it supports.
RATED PRESSURE
The qualified operating pressure which is recommended for a component or a system by the manufacturer.
REACTIVE MAINTENANCE
Maintenance strategy where the practice is to repair or replace equipment upon failure. Also referred to as Corrective Maintenance
REDUCER
A connector having a smaller line size at one end than the other.
RELIABILITY CENTERED MAINTENANCE (RCM)
The goal of RCM is to provide the given operational function with the required reliability and availability at the lowest cost. This process seeks to optimize operational reliability and associated tactics with respect to operational requirements. The strategy may choose to incorporate any, or all, of the 4 general maintenance techniques of Reactive, Preventive, Predictive or Proactive maintenance.
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.
RETURN LINE
A location in a line conducting fluid from working device to reservoir.
RETURN LINE FILTRATION
Filters located upstream of the reservoir but after fluid has passed 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 usually changes from laminar to turbulent between Reynold’s Number 2,000 and 4,000.
RING LUBRICATION
A system of lubrication in which the lubricant is supplied to the bearing by an oil ring.
ROLLER (OR ROLLING ELEMENT) BEARING
A bearing employing rollers making contact along a line. Frequently referred to as a rolling friction bearing, or an anti-friction bearing.
ROLLING FRICTION
Friction caused by surface contacts, where one surface rolls across another.
ROLL-OFF CLEANLINESS
The fluid system contamination level at the time of release from an assembly or overhaul line.
ROOT CAUSE
Default factor or group of factors for an underlying condition.
ROOT CAUSE FAILURE ANALYSIS (RCFA)
is the process of investigating how an equipment failure, process problem, quality problem, safety incident, environmental incident, and many other problems in a plant happened. RCFA is also commonly referred to as Root Cause Analysis or RCA.
ROTARY VISCOMETER
Device that measures viscosity between a fixed and rotating surface. They are very useful for measuring thixotropic fluids and viscosity at low temperatures.
ROTARY PRESSURE VESSEL OXIDATION TEST (RPVOT)
A test for the oxidation stability of a product obtained be sealing it in a closed container with oxygen under pressure. The drop in pressure of the oxygen is a measure of the amount of oxidation that has occurred. RPVOT (also known as RBOT) rotates the container during the test.
RULER
Commonly referred to as the Remaining Useful Life Evaluation Routine, this test measures hindered phenolic and aromatic amine antioxidant content. The purpose is to detect antioxidant additives remaining to estimate degradation and remaining life of the lubricant.
RUST INHIBITOR
A type of corrosion inhibitor used in lubricants to protect surfaces against rusting.
SAE
Society of Automotive Engineers, an organization serving the automotive industry.
SAE GRADE
Most typically used for viscosity classification of motor oils, developed by SAE. This viscosity method uses 100°C for the main viscosity measurement and is often accompanied by a “W” suffix as an indication of the cold temperature viscosity characteristics.
SAPONIFICATION
A critical process in the manufacturing of grease, saponification is the conversion of certain chemicals into soaps, which are the metallic salts of organic compounds. Typically, this is accomplished by a reaction of fat, fatty acids, or ester with an alkali.
SATURATION POINT
The point at which oil can hold no more water in the dissolved phase.
SAYBOLT UNIVERSAL SECONDS (SUS, SSU)
The time in seconds required 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).
SERVOVALVE
A valve which modulates output as a function of an input command.
SHEAR LOSS
Permanent and temporary viscosity loss due to high shear condition (high shear rate) in a fluid system. Shear thinning occurs with a multi-viscosity fluid when it is pumped through a line.
SHEAR RATE
Rate at which adjacent layers of fluid move with respect to each other, usually expressed as reciprocal seconds.
SHEAR STABILITY
Measure of the change in consistency of a grease after it has been subjected to prolonged shearing by means of a mechanical device like a grease worker (10,000 strokes) or a roll test; the percentage change in penetration values is an indicator of 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 is constant.
SILICONE
Signal conditioning is the manipulation of a signal from a transducer by such instruments as preamplifiers, filters, etc., in preparation for its final destination, which might be an FFT analyzer or recording device.
SILT
Contaminant particles 5µm and less in size.
SILTING
A failure generally associated with a valve which movements are restricted due to small particles that have wedged in between critical clearances (e.g., the spool and bore).
SINGLE LINE (or SERIES PROGRESSIVE)
A distribution system comprised of a distribution block that is supplied by a single header and can feed to multiple points. The progression of grease through the system requires that each point be supplied for each cycle of the system. If a point is blocked, then the supply line is corrupted for all points until the blockage is corrected.
SINGLE LINE PARALLEL
A distribution system comprised of a individually cycled injectors that are supplied by a single header. The header can provide multiple injectors independently. If a point is blocked the line continues to feed the balance of the points without interruption. All injectors must be individually inspected to confirm proper operation.
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.
SLEEVE BEARING
A journal bearing, usually a full journal bearing. Designed in an unbroken circular shape. Also called “solid bearing” and “bushing bearing”.
SLIDING FRICTION
The friction of two bodies that are in sliding contact.
SLOUGHING OFF
The release of containment from the upstream side of a filter element to the upstream side of the filter enclosure.
SLUDGE
The collective name for contamination in an engine crankcase. This includes decomposition products from fuel and oil, as well as materials from external sources. Insoluble material formed as a result either of deterioration reactions in an oil or of contamination of an oil, or both.
SPIN-ON FILTER
A throw-away 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.
SOCIETY OF MAINTENANCE & RELIABILITY PROFESSIONALS (SMRP)
A professional organization dedicated to the advancement of maintenance and reliability. SMRP offers credentials of CMRP and CMRT.
SOCIETY OF TRIBOLOGIST & LUBRICATION ENGINEERS (STLE)
A professional organization dedicated to the advancement of tribology and the lubricants industry. STLE also offers credentials via CLS, OMA, and CMFS.
SOLVENCY
Ability of a fluid to absorb inorganic material and polymers. The aniline point indicates the aromaticity of oils.
SOLVENTS
Compound with strong capability to dissolve a given substance. Aromatic-type solvents have the strongest solvency among hydrocarbons.
SOLVENT EXTRACTION
A refining process used to separate components (unsaturated hydrocarbons) from lube distillates in order to improve the oil’s oxidation stability, viscosity index, and response to additives. The oil and the solvent extraction media are mixed in an extraction tower, resulting in the formation of two phases: a heavy phase consisting of the undesirable unsaturates dissolved in the solvent, and a lighter phase consisting of a high-quality oil with some solvent dissolved in it. The phases are separated, and the solvent recovered from each by distillation.
SPECIFIC GRAVITY (LIQUID)
The ratio of the weight of a given volume of liquid to the weight of an equal volume of water.
SPECTROSCOPY
Use of electromagnetics for detecting and quantifying metallic elements resulting from wear, contamination, or additive concentration in oils. There are several specific methods that can be used, with varying ways to absorb or emit energy to indicate the elements’ concentrations in the sample.
STABILITY
The ability of lubricating grease to resist changes in consistency (hardness) during mechanical working. Greases that are not sheer stable, will soften excessively in service. also called “mechanical stability”. When the term is used with oil, it refers to the stability of the oil’s viscosity relative to shear stress.
STRAINER
A coarse filter element (pore size over approximately 40 µm).
STRIBECK CURVE
Graphical depiction of the change in frictional resistance that occurs when surfaces move from dead stop to hydrodynamic condition.
STOKE (St)
The kinematic measurement of a fluid’s resistance to flow defined by the ratio of the fluid’s dynamic viscosity to its density.
SUCTION FILTER
A pump intake-line filter in which the fluid is below atmospheric pressure.
SURFACE DAMAGE
Damage caused to the surface of a lubricated component through contact, abrasion, corrosion, adhesin, etc.
SURFACE FATIGUE
The formation of surface or subsurface cracks and fatigue crack propagation resulting from cyclic loading of a surface.
SURFACE FILTRATION
Filtration which primarily retains contaminant on the influent surface.
SURFACE TENSION
The contractile surface force of a liquid by which it tends to assume a spherical form and to present the least possible surface. It is expressed in dynes/cm or ergs/cm2.
SURFACTANT
Surface-active agent that reduces interfacial tension of a liquid. A surfactant used in a lubricant may increase the oil’s affinity metal or aid in the reduction of foam or air entrainment.
SYNTHETIC HYDROCARBON
Oil molecule with superior oxidation quality tailored primarily out of paraffinic materials.
SYNTHETIC LUBRICANT
A lubricant produced by synthesis rather than by extraction or refinement. Man-made as opposed to naturally occurring. Because synthetic oils have better chemical uniformity, they tend to have better oxidation resistance and thermal stability (including high VI).
SYSTEM PRESSURE
The pressure which overcomes the total resistance(s) in a system. It includes all losses as well as useful work.
TEMPERATURE CONTROL
Elimination or restraint of unwelcome heat or cold.
THERMAL STABILITY
Ability of a fuel or lubricant to resist oxidation under high temperature operating conditions.
THERMOGRAPHY
The use of infrared energy measurement through which temperatures of a wide variety of targets can be measured remotely (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.
THICKENER
Also referred to as a ‘grease thickener’. An emulsifying agent, typically a soap, to form a semisolid with a lubricating oil. The various soaps will impart key grease characteristics like temperature resistance, water resistance and chemical stability.
THIXOTROPY
The property of a lubricating grease which is manifested by a softening in consistency as a result if shearing followed by a hardening in consistency starting immediately after the shearing is stopped.
THRUST BEARING
An axial-load bearing.
THRUST LOAD
Load on a bearing parallel to the shaft, same as axial load. Various thrust bearings are designed to handle (counteract) this force.
TIMKEN EP TEST
Measure of the extreme-pressure properties of a lubricating oil. The test utilizes a Timken tester, 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 is formed on the block.
TIMKEN OK LOAD
The heaviest load that a test lubricant will sustain without scoring the test block in the Timken Test procedures, ASTM Methods D 2509 (greases) and D 2782 (oils).
TOTAL ACID NUMBER (TAN)
Used to determine oxidation of oil it is a measurement of acidity in the oil expressed as the number of milligrams of Potassium Hydroxide to neutralize the acids in one gram of oil.
TOTAL BASE NUMBER (TBN)
Represents the oils’ ability to neutralize acids, generally used with engine oils. The higher the TBN, the more acid it can neutralize.
TRIBOLOGY
The science of the interactions between surfaces moving relative to each other, including the study and application of friction, lubrication, and wear.
Organizations behind the Science of Tribology:
-
- API (American Petroleum Institute)
- SAE (Society of Automotive Engineers
- NRCC (National Research Council of Canada)
- BHRA (British Hydro-mechanical Research Association)
- AGMA (American Gear Manufacture’s Association)
- FPRC (Fluid Power Research Center at OSU)
TRIBOLOGICAL FAILURES
Machine failure due to the conditional failure of a critical or protected surface, due to one of more of a set of predefined ‘tribological’ failure modes.
ULTRACLEAN
1 particle >10 micron per milliliter.
UNDISTRUBED PENETRATION
grease in its original container.
UNLOADING
The release of contaminant that was initially captured by the filter medium.
UNWORKED PENETRATION
The penetration number of a grease sample, at 77°F, which has received only the minimum handling in transfer to the test apparatus. This number is used to establish the NLGI Grade of the grease. VARNISH- A deposit resulting from oxidation and polymerization of fuels and lubricants. Like, but softer than, lacquer. Many experts believe that varnish ultimately becomes lacquer, with the passage of time and exposure to high temperatures.
VACUUM SEPARATOR
A separator that utilizes sub atmospheric pressure to remove certain gases and liquids from another liquid because of their difference in vapor pressure.
VALVE LIFTER
Sometimes called a “cam follower,” a component in engine designs that use a linkage system between a cam and the valve it operates. The lifter typically translates the rotational motion of the cam to a reciprocating linear motion in the linkage system.
VAPOROUS CAVITATION
Ebullition process (the boiling of a liquid) that occurs if a bubble grows explosively in an unbounded manner as liquid rapidly changes to vapor, which occurs when the pressure level falls below the vapor pressure of the liquid.
VARIABLE DISPLACEMENT PUMP
A pump in which the displacement per cycle can be varied.
VEGETABLE OIL
Raw material used in the manufacture of environmentally friendly (bio-degradable and readily biodegradable) lubricants. Also known as natural ester.
VENTURI EFFECT
The creation of a partial vacuum that restricts flow of a fluid. In bath lubricated system, a venturi against the headspace can cause an improper fluid level reading.
VIBRATION ANALYSIS
Analysis of machine signals representing the machine’s mechanical oscillation or motion about a reference point of equilibrium.
VI IMPROVER
Viscosity Index Improver – an additive, usually a high molecular-weight polymer, that reduces the tendency of an oil to change viscosity with temperature.
VISCOMETER or VISCOSIMETER
An apparatus for determining the viscosity of a fluid.
VISCOSITY
The measure of a fluid’s resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required 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, Engler Viscosity, and Redwood Viscosity.
VISCOSITY GRADE
Any of a number of systems which characterize lubricants according to viscosity for applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils.
VISCOSITY INDEX (VI)
A commonly used, unitless, measure of a fluid’s change in viscosity with temperature. The higher the V.I., the smaller the relative change in viscosity as temperature changes.
piston engine oils.
VISCOSITY INDEX IMPROVERS
Additives that increase the viscosity of the fluid throughout its useful temperature range. Such additives are polymers that possess thickening power as a result of their high molecular weight and are necessary for formulation of multi-grade engine oils.
VISCOSITY MODIFIER
An additive, usually a high molecular weight polymer, that reduces the tendency of an oil’s viscosity to change with temperature.
VISCOSITY-TEMPERATURE RELATIONSHIP
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 predict graphically the viscosity of a petroleum fluid at any temperature within a limited range if the viscosities at two other temperatures are known. The charts used for this purpose are the ASTM Standard Viscosity-Temperature Charts for liquid Petroleum Products, available in 6 ranges.
WATER RESISTANCE
The ability of grease to withstand the addition of water to the lubricant system without adverse effects. Generally measured in three areas: washout resistance, water absorption characteristics, and water corrosion resistance.
WATER WASHING
Like particle scrubbing, the effect of leaching the additives that are prone to dissolve in water as a consequence of allowing too much water to contact the lubricant.
WAY LUBRICANT
Lubricant for the sliding ways of machine tools such as planers, grinders, horizontal boring machines, shapers, jig borers, and milling machines. A way lubricant is formulated with special frictional characteristics designed to overcome the stick-slip motion associated with slow-moving machine parts.
WEAR
The removal of materials from surfaces in relative motion. See abrasive wear, adhesive Wear, and corrosive wear.
WEAR DEBRIS
Particles that are detached from machine surfaces as a result of wear and corrosion. Also known as wear particles.
WETTING AGENT
Polar additive used to ‘bond’ a base oil lubricant to the metal surfaces experiencing high sliding conditions. The bond is due to polarity affinity between molecule, additive and metal surface.
WICKING
The vertical absorption of a liquid into a porous material by capillary forces.
WORKED PENETRATION
The penetration of a sample of lubricating grease immediately after it has been brought to 77°F and then subjected to 60 double strokes in a standard grease worker. This procedure and the standard grease worker are described in ASTM Method D 217.
ZDDP
Zinc Dialkyl Dithiophosphate. Widely used as an anti-wear additive to protect heavily loaded components, ZDDP also acts as a corrosion inhibitor and antioxidant.