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  Lubrication is a science and it is intended that this Lubrication Library will provide you with a thorough scientific yet easily understandable glossary of all the relevant terms. We hope that it will prove to be informative and interesting. |
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ABRASIVE WEAR : Wear between two surfaces in relative motion due to particles (three bodies) or surface roughness (two bodies). ABSOLUTE VISCOSITY : Term used interchangeably with dynamic viscosity to distinguish it from kinematic viscosity. The SI unit of absolute viscosity is the poise, however, is generally reported as centipoises (cP). ACCUMULATOR (HYDRAULICS) : A device in which hydraulic fluid is stored under pressure in a system to be used a source of fluid power. ACID : A compound containing Hydrogen, which can be replaced by a metal, forming a salt. In grease manufacture, Fatty Acids are used, which form a specific type of salt, known as soap (see definition of soap). ACID AND BASE NUMBER : An indication of the amount of free acidic or alkaline materials in a petroleum product. These materials may be either inorganic or organic. The acid number is the weight in milligrams of potassium hydroxide (KOH) required to neutralize the acidic constituents in one gram of the sample. Base number is the number of milligrams of potassium hydroxide (KOH) equivalent to the acid required to react with one gram of the sample. The unit usually expresses as mg KOH/g. Also known as Neutralization Number. ACTIVATED : The condition of a substance which has been treated in a special manner to increase its activity which may be physical, such as the behavior of catalysts. Organoclay and silica are materials which have received special treatment of this type, when they are used as inorganic grease thickeners. ACTUATOR : A mechanic device, like a cylinder or hydraulic motor, used to convert hydraulic energy into mechanic energy. ADDENDUM (GEARS) : Distance between the pitch circle and tooth crest. ADDITIVE : Name given to petroleum oils compounded with chemical addition agents to enhance certain properties such as detergency, antioxidant characteristics, etc. or any material added to a lubricating grease or lubricating oil to improve its suitability for service. It may improve a property already possessed by the lubricant, or give it properties not naturally possessed. Typical examples are antioxidants, EP agents or anti-wear additives. ADHESION : The force which causes the particles of unlike substances to tend to stick together as for example treacle to a spoon. The force or forces causing two materials, such as lubricating grease and a metal, to stick together. This is a measure of the solvent quality of a petroleum product and gives a clue as to its type, i.e. Paraffinic, Naphthenic, etc. It also indicates the material's tendency to cause rubber seals to swell. ADHESIVE WEAR : Wear caused by metal-to-metal contact; characterized by local welding and tearing of the surface. AFFINITY : The attraction between elements which, under favorable conditions, result in their union. AGE HARDENING : An undesirable process during which a solid (a grease, an elastomeric seal or rubber hose) hardens with prolonged storage. AGGLOMERATION : The potential of the system for particle attraction and adhesion. AIR ENTRAINMENT : The presence of air bubbles throughout an oil as a result of agitation and/or the release of dissolved air because of a sudden change in environment. Air entrainment is visible, as the oil becomes opaque and bubbly. AIR LINE LUBRICATOR : An oil reservoir attached to an air line that provides automatic air-borne lubrication to air operated power consuming equipment by means of venturi action. AIR OIL SEPARATOR : A mechanical device that defoams oil, using a centrifugal oil trap, or any oil condensing device in an air line. ALKALI : Any substance having basic properties (as contrasted with acid properties). In a restricted sense in grease manufacture, this term is applied to the hydroxides of the alkali metals, including lithium, sodium, calcium and other metal ions. ALUMINUM COMPLEX GREASE : A grease prepared from a lubricating fluid thickened with aluminum complex soap. AMORPHOUS (WITHOUT FORM) : A term applied to such materials as carbon black, as contrasted with such crystalline materials as graphite or Molybdenum Disulfide. ANHYDROUS : Being devoid of water. ANILINE POINT : The lowest temperature at which equal volumes of aniline and hydrocarbon fuel or lubricant base stock are completely miscible. A measure of the aromatic content of a hydrocarbon blend, used to predict the solvency of a base stock or the cetane number of a distillate fuel. ANNULAR GEARS : Gears which are internal in nature having parallel teeth similar to the spur gear but cut on the inside rim or inner surface of a cylinder or ring. The companion pinion of an annular gear, however, must be a standard gear. ANTI-FOAM AGENT : An additive used to suppress the foaming tendency of petroleum products in service. May be a silicone oil to break up surface bubbles or a polymer to decrease the number of small entrained bubbles. ANTI-MICROBIAL AGENT : A substance that kills or inhibits the growth of microbes, such as bacteria, yeast and mold in the finished products, such as lubricants. ANTI-SEIZE COMPOUND : Grease-like substance with significant amount of dispersed solid lubricants, such as graphite, molybdenum disulfide and metallic powders, primarily to prevent seizure on threaded joints. Sometimes, it is also called as a tool joint compound. ANTI-WEAR AGENT : Additive or its reaction product, which forms thin, tenacious film on highly loaded parts to prevent metal-to-metal contact. ANTIOXIDANT : Small quantities of certain reagents used to prevent the oxidation by air or free oxygen of a variety of substances (including petroleum) which undergo oxidation or auto-oxidation when exposed to air or oxygen or oxidation inhibitor an additive, usually incorporated in a relatively small proportion, to retard oxidation of lubricants including greases and gear lubricants. API ENGINE SERVICE CATEGORIES : Gasoline and diesel engine oil quality levels established jointly by API, SAE and ASTM; formerly called API Engine Service Classifications. API GRAVITY : See GRAVITY APPARENT VISCOSITY : The ratio of shear stress to rate of shear of a non- Newtonian fluid, calculated from Poiseuille's equation and measured in poises or centipoises. The apparent viscosity of most greases varies with changing rates of shear and temperature, and must therefore be reported as the value at a given shear rate and temperature. APPEARANCE : Those characteristics of a lubricating grease which are observable by visual inspection only. This general term includes various characteristics described under BULK APPEARANCE, TEXTURE, BLOOM, COLOR AND LUSTER. ASH : Metallic deposits formed in the combustion chamber and other engine parts during high-temperature operation. ASH (SULFATED) : The ash content of an oil, determined by charring the oil, treating the residue with sulfuric acid, and evaporating to dryness. Expressed as % by mass. 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. ASPHALT/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. AUTOMATIC TRANSMISSION FLUID (ATF) : Fluid for automatic, hydraulic transmissions in motor vehicles. BACTERICIDE : Additive to inhibit bacterial growth in the aqueous component of fluids, preventing foul odors. BAKERYLUBE : A trademark of Bel-Ray products. Suspended solid lubricants suitable for lubrication of chains and rollers of conveyers operation in ovens or in other locations under relatively high temperature conditions. BARIUM/BARIUM COMPLEX GREASE : A grease prepared from a lubricating fluid, thickened with barium soap or barium complex soap. BASE STOCK : The base fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants. BASES : Compounds that react with acids to form salts plus water. Alkalis are water-soluble bases, used in petroleum refining to remove acidic impurities. Oil soluble bases are included in lubricating oil additives to neutralize acids formed during the combustion of fuel or oxidation of the lubricant. BEARINGS : Contact surfaces between the frame of a machine and the moving parts whereby support and guidance are given to sliding, revolving or semirotative members. They are not necessarily stationary parts, however, as in the case of gudgeon pin and crank pin bearings, where both bearing and pin are in motion. Another form of bearing is that in which rolling members such as balls or rollers are used to control the relative movements of the connected parts, and which are known as anti-friction bearings. BEL-BIO : A trademark of Bel-Ray products. All purpose highly biodegradable lubricants. BENCH TEST : A modified service test in which the service conditions are approximated in the laboratory. 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. BEVEL GEAR : Gear in which the teeth are cut on an angular surface, such as would be presented by a truncated cone. They are used for the transmission of motion between shafts with intersecting center lines which form an angle between each other, usually 90 degrees. BIODEGRADABLE : Capable of decaying through the action of living organisms. BIODEGRADATION : The process of chemical break-down or transformation of a substance caused by living organisms and their enzymes. BLACK OILS : Lubricants containing asphaltic materials, which impart extra adhesiveness, that are used for open gears and steel cables. BLEEDING/OIL SEPARATION (GREASE) : The separation of oil from a grease structure. A certain amount of bleeding is considered desirable in greases, since this tends to provide continuous oil lubrication to bearings. BLENDING : Blending is regarded as the process of mixing lubricant components for the purpose of obtaining desired physical and/or chemical properties. It is the intent to establish a difference between blending and compounding. COMPOUNDING is here regarded as the mixing or otherwise combining lubricant components with other components for the purpose of securing chemical and/or physical properties not usually obtainable by blending of fluid lubricant components alone. BLOOM : The surface color (usually blue or green) of a lubricating oil or grease when viewed by reflected daylight at an angle of about 45 degrees from the surface. BLOOM is associated with the absorption of ultra violet light in the oil and may not be visible if the sample is viewed by artificial light or the color of an oil as reflected from its surface and which differs from the color of the oil by transmitted light. Also called "Fluorescence" or sometimes "Outertone". BOUNDARY LUBRICATION : Lubrication between two rubbing surfaces without the development of a full fluid lubricating film. It occurs under high loads and requires the use of anti-wear or Extreme-Pressure (EP) additives to prevent metal-to-metal contact. BREATHER : An air filtering device placed on top of a reservoir to allow it to “breath” as the oil level rises and falls. All incoming air is thereby filtered to keep out airborne contaminants. 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 : Denting caused by impact of one bearing component against another while stationary. BROMINE NUMBER (VALUE) : The percentage of bromine that will be absorbed by a chemically unsaturated substance (base oil, vegetable oil, rubber, etc.) in a given time under arbitrary conditions. A measure of unsaturation. BROOKFIELD VISCOSITY : Measure of apparent viscosity as determined by the Brookfield viscometer at a controlled temperature and shear rate. BULK APPEARANCE (GREASE) : Visual appearance of grease when the undisturbed surface is viewed as an opaque container. BULK APPEARANCE should be described in the following terms:
CALCIUM SULFONATE COMPLEX GREASE : A calcium neutralized grease thickened with sulfonic acid and other acids. CALCIUM/CALCIUM COMPLEX GREASE : A grease made from a lubricating fluid thickened with calcium soap or calcium complex soap. CAMS : Eccentric shafts used in most internal combustion engines to open and close valves. CAPILLARITY : The tendency of certain liquids to ascend capillary tubes or fine orifices. This property is of importance in wick feed lubricators, in kerosene lamps, etc. CARBON RESIDUE : Coked material remaining after an oil has been exposed to high temperatures under controlled conditions. Laboratory test originally developed to compare the carbon- forming properties of lubricating oils used in internal combustion engines, but now having more general application. CATALYST : A material which promotes some chemical action without itself entering into the reaction. CATALYTIC CONVERTER : An integral part of vehicle emission control systems since 1975. Oxidizing converters remove hydrocarbons and carbon monoxide (GO) 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 or phosphorous compounds in the fuel or lubricant. CATASTROPHIC FAILURE : Sudden, unexpected failure of a machine resulting in considerable cost and downtime. CAVITATION :
CAVITATION DAMAGE : An erosion process in which metal is removed by cavitation. CENTISTOKE : Measurement unit of kinematic viscosity of a fluid. One centiStoke equals 0.01 Stokes and is equivalent to one mm2/sec in SI units. See definition of Stoke. CENTRALIZED LUBRICATION : A system of lubrication in which the lubricant for various parts of a machine or a group of machines is supplied from a central location. CETANE INDEX : A value calculated from the physical properties of a diesel fuel to predict its Cetane Number. CETANE NUMBER : A measure of the ignition quality of a diesel fuel, as determined in a standard single cylinder test engine, which measures ignition delay compared to primary reference fuels. The higher the Cetane Number, the easier a high-speed, direct-injection engine will start, and the less "white smoking" and "diesel knock" after startup. CETANE NUMBER IMPROVER : An additive (usually an organic nitrate) that boosts the Cetane Number of a fuel. CHANNELING :
CIRCULATING OILING SYSTEM : In such lubricating systems, the oil may be pumped under pressure directly to the parts requiring lubrication or, in a gravity circulating system, the oil is pumped to a tank located above the parts to be lubricated and flows down by gravity. The used oil then drains to a sump from where it is pumped through a filter or centrifuge then, usually through an oil cooler, back to the initial reservoir. Term also sometimes used to describe pressure oiling system of automotive engines. CLEANLINESS RATING : A rating based on the number of particles of specified sizes in a measure of fluid. The ISO 4406 standard specifies the code to be used for such rating. CLOUD POINT : The temperature at which a cloud of wax crystals appears when a lubricant or distillate fuel is cooled under standard conditions. Indicates the tendency of the material to plug filters or small orifices under cold weather conditions. COHESION : The molecular attraction causing particles of a given substance to attract each other and stick together. Cohesion contributes to the resistance of a lubricating grease to flow. 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. COLLOID : Substances of particle size larger than molecules, but small enough to possess reasonable dispersion stability in two phase systems. A lubricating grease is a colloidal system (See also THICKENING AGENT). COLOR (LUBRICANT) : The shade and intensity shown when lubricating grease is viewed under conditions such as to eliminate BLOOM. Such conditions may be obtained by viewing the lubricating grease in an opaque container such as a metal package, by reflected light, from a position approximately perpendicular to the surface; or by viewing it with a transmitted light only, by placing the sample on a transparent plate. When colors of lubricating grease are referred to, the method by which colors are determined should be clearly indicated. Colors of lubricating greases are best described in terms of the predominant hue such as amber, brown (or perhaps green, red, or blue for dyed greases) with a qualifying adjective describing intensity in terms of light, medium or dark (of lubricating oil). That shade shown when viewed under transmitted light only. Usually lubricating oil colors are obtained by viewing the oil under specified conditions in test equipment. Several such methods are available, the most widely used being ASTM D1500 which describes the colors in terms of number. COMPLEX SOAP (GREASE) : A soap to thicken grease wherein the soap crystal of fiber is formed by a co-crystallization of two or more compounds:
COMPOUNDED OILS : It is usual to regard "Compounded Oils" as mixtures of fatty oils with mineral oils, and "Blended Oils" as mixtures of different grades of mineral oils. COMPRESSION RATIO : In an internal combustion engine, the ratio of the volume of combustion space at bottom dead center to that at top dead center. CONDITION MONITORING : The use of specialized techniques that monitor the condition of equipment and detect the onset of failure in sufficient time to plan a maintenance intervention that prevents failures; these techniques include lubricant analysis, vibration analysis, thermography, motor current signature analysis, Non-destructive testing (NDT) surface inspections (such as ultrasonic, acoustic emission, electromagnetic, radiography, magnetic particle and penetrant testing). CONSISTENCY/HARDNESS (GREASE) : The degree to which a plastic material such as lubricating grease resists deformation under the application of force. (It is therefore a characteristic of plasticity, as viscosity is a characteristic of fluidity. Consistency is usually indicated by either apparent viscosity or NLGI grade). COPPER CORROSION TEST : To determine whether or not a lubricant contains corrosive or tarnishing materials, a polished copper strip is submerged in the lubricant, which is maintained at an elevated temperature for a period of some hours. If the lubricant contains any trace of a chemically reactive substance under these conditions the copper strip becomes discolored with a characteristic dark film. The test is particularly useful for detecting the presence of corrosive sulfur compounds. CORROSION : Any chemical reaction which results in the conversion of useful materials, generally metals or alloys, into substances of no value for the purpose fulfilled by the original material. Rusting is the most common example of corrosion, chemical attack or reaction on metals by acid, alkali oxygen, chlorine, sulfur, or other chemicals. This is distinct from metal destruction by wear and may be evident by either discoloration or pitting. CORROSION INHIBITOR : Additive that protects lubricated metal surfaces from chemical attack by water or other contaminants. CORROSIVE WEAR : Wear caused by chemical reaction. COUPLING : A frequently-used alternative term for “fitting”: a straight connector for fluid lines; or a large-diameter device that connects the ends of two shafts, between a motor shaft and a gear drive unit, for example. CROWN : The top of the piston in an internal combustion engine above the fire ring, exposed to direct flame impingement. CUP GREASE : Common name for lime soap greases. Usually a calcium base grease having a yellowish color and a buttery structure for use in grease cups. CUTTING FLUID/OIL : Oil used in machining operations to lubricate the cutting tool, to act as a coolant to dissipate the heat that is generated by friction and the stressing of the metal, and to prevent rust and corrosion of the machine tool or machined part. DEMULSIBlLITY : A measure of a fluid's ability to separate from water. DENATURANTS : Toxic or noxious components used in fuel ethanol to make it unfit for use as a beverage. DENSITY : Mass per unit volume. Usually, the unit expresses as g/ml, g/L or kg/m3. DETERGENCY :
DETERGENT : A substance added to a fuel or lubricant to keep engine parts clean. In motor oil formulations, the most commonly used detergents are metallic soaps with a reserve of basicity to neutralize acids formed during combustion. DETERGENT/DISPERSANT : An additive package that combines a detergent with a dispersant. DETONATION : Uncontrolled burning of the last portion (end gas) of the air/fuel mixture in the cylinder of a spark-ignition engine. Also known as "knock" or "ping." DIELECTRIC STRENGTH : Test designed to give a measure of the insulating properties of oils, carried out by applying an increasing voltage to the oil under specified conditions until breakdown occurs, denoted by the establishment of an arc. DILUENT/CUTBACK SOLVENT : Instead of heating, a solvent added to viscous lubricants to permit application in cold weather. The solvent evaporates after application, leaving the lubricant in place. Diluent is widely used in open gear lubricant. DILUTION OF ENGINE OIL : Contamination of crankcase oil by unburned fuel, leading to reduced viscosity and flash point. May indicate component wear or fuel system maladjustment. DISPENSABILITY : The property of a grease which governs the ease with which it may be transformed from its container to its point of application. Most used in discussions of dispensing in grease systems, where it includes both the properties of pumpability and feedability. DISPERSANT : An additive that helps keep solid contaminants in a crankcase oil in colloidal suspension, preventing sludge and varnish deposits on engine parts. Usually nonmetallic ("ashless"), and used in combination with detergents. DISPERSANT ACTION : The property of an oil which prevents the coagulation or sticking together of carbonaceous particles by keeping them in a finely divided state, and which thus prevents their settling out and deposition on engine parts. DISTILLATION : The basic test used to characterize the volatility of a gasoline or distillate fuel. DN FACTOR/SPEED FACTOR : Used as a guide to lubricant selection for rolling contact bearings. DN value is determined by the mean bearing diameter in mm (D) multiplied by the speed of the bearing at standard operating conditions in rpm (N). DROPPING POINT (GREASE) : The temperature at which a drop of material falls from the orifice of the test apparatus under the conditions of ASTM D566 or D2265 tests. This test should be considered as having very limited bearing upon service performance. It is not the melting point of the grease, this being a term of little or no significance when applied to plastic materials such as lubricating grease. These materials are characterized by a melting range during which the material becomes steadily softer. Only through the establishment of an arbitrary and fully controlled test procedure such as the ASTM Dropping Point, can any single temperature be established as a characteristic of the material. Test carried out on grease which is, in general, an indication of the temperature of transition from the solid or semi-solid, to the liquid state. DRY FILM LUBRICANT : A solid material, such as graphite, molybdenum disulfide or PTFE, used with loads in the boundary region of lubrication. These materials may be applied as pastes, by spraying, dipping, brushing in an air-drying carrier, burnishing or resin bonding. DYNAMIC VISCOSITY : See absolute viscosity ELASTOHYDRODYNAMIC LUBRICATION (EHD) : A lubricant regime characterized by high unit loads and high speeds in rolling elements where the mating parts deform elastically due to the incompressibility of the lubricant film under very high pressure. ELASTOMER : A rubber or rubber-like natural or synthetic material that cab be stretched repeatedly and that returns to its approximate original dimensions when the stress is released. EMULSIFIER : Additive that promotes the formation of a stable mixture, or emulsion, of oil and water. EMULSION : A mixture of water and oily material in which either very small drops of water are suspended in oil, or similar drops of oil are suspended in water, the whole being stabilized by a third component such as soap, called an emulsifying agent. Milk is an emulsion of fat in water.
A liquid in which is suspended another immiscible liquid. Water and oil can be emulsified under certain conditions of oil type and severe agitation. Emulsifying agents are sometimes added to oils for the production of cutting fluids, which are to be mixed with water. END POINT : Highest vapor temperature recorded during a distillation test of a petroleum stock. ENGINE DEPOSITS : Hard or persistent accumulation of sludge, varnish, lacquer and carbonaceous residues due to blow-by of unburned and partially burned fuel, or the partial breakdown of the crankcase lubricant. Water from the condensation of combustion products, carbon, residues from fuel or lubricating oil additives, dust and metal particles also contribute. EP AGENT (EXTREME PRESSURE ADDITIVE) : Lubricant additive that prevents sliding metal surfaces from seizing under extreme pressure conditions. EROSION : Wearing away of a surface by an impinging fluid or solid. ESTERS : Compounds formed by the combination of an organic acid with an alcohol. Ester compound, such as diester or polyol ester, is widely used as a type of synthetic oil. EVAPORATION LOSS : That portion of a lubricant which volatilizes under the effects of temperature pressure and time. Such loss can occur in use or in storage. A widely used testing method is ASTM D972. FALSE BRINELLING : Fretting of one bearing component against another; may appear as a dent, but original surface finish is worn away. FAT : An animal or vegetable oil which will combine with an alkali to saponify and form a soap (See definition of soap). FATIGUE : Cracking, flaking or spalling of a surface due to stresses beyond the endurance limit of the material. FATTY ACID : The acid-reactive part of a fat. Fatty acids are more uniform, since the refining of the fat produces a more uniform raw material. FEEDABILITY : The ability of a lubricating grease to flow to the suction of a dispensing pump at a rate of at least equal to pump delivers capacity. (Some lubricating greases do not feed satisfactorily and cause cavitation at the inlet of a dispensing pump). FERROGRAPHY : Magnetic particle analysis. FILM STRENGTH : The ability of a film or lubricant to resist rupture due to load, speed and temperature. FLASH POINT : Minimum temperature at which a fluid will support instantaneous combustion (a flash) but before it will burn continuously (fire point). Flash point is an important indicator of the fire and explosion hazards associated with a petroleum product. FLUID FRICTION : The internal friction of the lubricating oil film when the solid surfaces between which relative motion is taking place and separated completely by a fluid film. Under such conditions, the oil flows in parallel layers like a pack of playing cards sliding over each other when the outside cards are held adhering to the palms of the hands and the palms are moved relatively to each other, thus causing the outside cards to move with the hands and the intervening cards to move in relation to their position in the pack. FLUIDITY : The property of flowing freely: the reciprocal of viscosity. FOAMING : Oil foaming is generally caused from excessive agitation, moisture contamination or air ingression in suction lines. FOLLOWER PLATE : A piece of sheet metal used on top of grease in a pump type dispenser to assure the grease remaining level as it is pumped. This avoids the formation of a cavity around the grease pump pick-up tube and permits the dispensing of all the grease in the container without manual leveling of the grease from time to time. FRETTING : A form of wear resulting from oscillating or vibratory motion of limited amplitude, resulting in the removal of very finely divided particles from rubbing surfaces. In the case of ferrous metals in air, the wear particles oxidize to a reddish, abrasive iron oxide which has led to the name of FRETTING CORROSION. This latter happening has also been called FALSE BRINELLING AND FRICTION OXIDATION when it occurred in rolling contact bearings. FRICTION : A resistance to motion between two surfaces in contact. When two surfaces are brought into contact and made to slide, the one over the other, a force immediately comes into play resisting this motion. This force is known as friction. Friction is not confined to solids; it plays an equally important part with liquid and gaseous substances. FROST : Field of micropits; form of micro-adhesive wear. GALLING : When loads are heavy and the film strength of the oil is insufficient to support the load, momentary metallic contact occurs resulting in a ridge at the pitch line of the driven gear and a hallow at the pitch line of driving gear. In severe cases, wear of the metal takes place along the faces and flanks of the gear teeth, also known as "Galling". GASEOUS FUELS : Liquefied or compressed hydrocarbon gases (propane, butane or natural gas), which are finding increasing use in motor vehicles as replacements for gasoline and diesel fuel. GASOLINE : A volatile mixture of liquid hydrocarbons, containing small amounts of additives and suitable for use as a fuel in spark-ignition, internal- combustion engines. GASOLINE/ETHANOL BLEND : A spark-ignition automotive engine fuel containing denatured fuel ethanol in a base gasoline. It may be leaded or unleaded. GEAR RATIO : Ratio of the number of teeth on the gear to the number of teeth on the pinion, also the number of teeth on the worm wheel to the number of teeth on the worm. GEL : An elastic solid mixture of a colloid and liquid possessing a yield point and a jellylike texture. GREASE : A solid to semi-fluid product of dispersion of a thickening agent in a liquid lubricant. Other ingredients imparting special properties may be included. HALOGENATED SOLVENT : Solvent formulated with one of the halogens, usually chlorine or fluorine. Most of halogenated solvents are associated with the atmospheric depletion of ozone. HELICAL GEAR : Resembles the spur gear in that the teeth are cut on a cylindrical body, but differs in that the teeth are spiraled around the body rather than formed parallel to the axis of the gear body. Spiraling the teeth provides smoothness. HERRINGBONE GEAR : Resembles two helical gears having reversed directions of spiral, placed side by side, so that the teeth come together to form a chevron pattern. In the herringbone gear, spiraling the teeth in both directions neutralizes end thrust. HIGH TEMPERATURE HIGH SHEAR RATE VISCOSITY (HTHS) : A measure of a fluid's resistance to flow under conditions resembling highly-loaded journal bearings in fired internal combustion engines, typically 1 million S-1 at 150°C. HOMOGENIZATION : The process of subjecting a lubricating grease to intimate mixing and intensive shearing action, the end result of which is to obtain a more uniform and higher degree of dispersion. HYDRATED SOAP : A soap which has water associated with its structure. A typical example is water stabilized calcium soaped grease which owes its stability to hydrated calcium soap. HYDRAULIC FLUID : Hydraulic fluids are used to transmit force from one part of a system to another, as in hydraulic brakes, to damp out suddenly applied forces to another, as in shock absorbers, or to retard motion as in gun recoil mechanisms. HYDRODYNAMIC (FLUID FILM) LUBRICATION : That state of lubrication in which the shape and relative motion of the sliding surfaces causes the formation of a continuous fluid film under sufficient pressure to prevent any contact between the surfaces. It is also called Fluid Film Lubrication. HYDROFINISHING : A process for treating raw extracted base stocks with hydrogen to saturate them for improved stability. HYDROLYTIC STABILITY : Ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water. HYDROMETER : An instrument for determining the gravity (either specific or API.) of liquids, consisting of loaded bulk, surmounted by a narrow tube bearing a scale. The gravity is indicated by a line on the scale which coincides with the meniscus of the liquid. HYDROPHILIC : Having an affinity for water; capable of uniting with or dissolving in water. HYDROPHOBIC : Having antagonism for water; not capable of uniting or mixing with water. HYDROSTATIC LUBRICATION : That state of lubrication in which the lubricant is supplied to a plain bearing under sufficient external pressure to separate the opposing surfaces by a continuous lubricant film. HYGROSCOPIC : Capable of absorbing water from the air readily. HYPOID GEAR : Gear construction in which a line bisecting the pinion does not dissect the gear, i.e. the pinion is offset to the center line of the gear. HYPOID GEAR LUBRICANT : A gear lubricant having extreme pressure characteristics for use in hypoid type gears, such as automotive differentials. INCOMPATIBILITY : Two lubricating greases show incompatibility when a mixture of the products show physical properties of service performance which markedly is inferior to those of either of the greases before mixing. Performance or properties inferior to one of the products and superior to the other may be due to simple mixing and would not be considered as evidence of incompatibility. INDUCTION PERIOD : In an oxidation test, the time period during which oxidation proceeds at a constant and relatively low rate. It ends at the point where oxidation rate increases sharply. INHIBITOR : Additive that improves the performance of a petroleum product by controlling undesirable chemical reactions, i.e. oxidation inhibitor, rust inhibitor, etc. INORGANIC THICKENER : See NON-SOAP THICKENER. INSOLUBLES : 1. ASTM D893 – contaminants found in used oils due to dust, dirt, wear particles or oxidation products. Often measured as pentane or toluene insolubles to reflect insoluble character. 2. ASTM D128 – components of a grease that are insoluble in the prescribed reagents; generally denotes fillers, additives and certain types of thickeners as well as impurities. IODINE NUMBER/IODINE VALUE : The percentage of iodine that will be absorbed by a chemically unsaturated substance (base oil, vegetable oil, rubber, etc.) in a given time under arbitrary conditions. A measure of unsaturation. JOURNAL : Male portion of a rotary bearing; part of shaft or axle that rests on bearings. KINEMATIC VISCOSITY : Kinematic viscosity is generally measured by taking the time of flow of a certain volume of the product, at a fixed temperature (usually 40°C or 100°C), through a standard-sized orifice. The SI unit of kinematic viscosity is the stoke, however, is generally reported as centiStoke (cSt). LITHIUM/LITHIUM COMPLEX GREASE : A grease prepared from a lubrication fluid thickened with lithium soap or lithium complex soap. LUBRICANT : A substance used to reduce friction or to make surfaces slippery. The lubricant tends to eliminate the effect of aspirates of the surface, to prevent adhesion between surface and to introduce a material, either solid or fluid, of sufficient consistency to maintain a film which can be easily sheared. Any substance interposed between two surfaces in relative motion, which reduces the friction of wear of the surfaces. LUBRICATING GREASE STRUCTURE : The physical arrangement of the component particles of a lubricating grease thickener additive, if any, and liquid lubricant. It is the nature and stability of this arrangement which determine the appearance, texture and physical properties of lubricating grease. LUBRICATION : Control of friction and wear by the introduction of a friction-reducing film between moving surfaces in contact. May be a fluid, solid or plastic substance. LUBRICITY : See oiliness. LUSTER : The intensity of light reflected by lubricating grease; its sheen or brilliance. Luster should be described as follows: BRIGHT: Reflects light with a relatively strong intensity. DULL: Reflects light with a relatively weak intensity. Some greases with a high water content may have a dull luster. Certain thickeners and fillers give a grease characteristic dull luster. MECHANICAL STABILITY (GREASE) : See Shear Stability. MELTING POINT : The temperature at which a product begins to melt or to change from the solid to the liquid state MICRON : 10-6 meter; one millionth of a meter. MISCIBLE : Liquids capable of forming a liquid solution or uniform mixture of more than one type of liquid. MIXED FILM LUBRICATION : A condition of lubrication in which the lubricant film is so thin that the friction between the surfaces is determined by the properties of the surfaces as well as the viscosity of the lubricant. MOBILITY (GREASE) : Analogous to fluidity, the property of a lubricating grease that permits flow under pressure, as in centralized grease dispensing systems. MOLYLUBE : A trademark of Bel-Ray products. Any lubricant comprising molybdenum disulfide or other molybdenum-contained compounds to improve lubricating property. MOTOR OIL : Motor oil is a type of liquid oil used for lubrication by various kinds of internal combustion engines. Other benefits from using motor oil include cooling by carrying heat away from moving engine parts and often include cleaning and corrosion inhibition in internal combustion engines. The major fraction of the majority of motor oils is derived from petroleum. Synthetic motor oil, consisting of artificially-synthesized compounds, currently has a minority share in the motor oil market place because it is more expensive, but offers enhanced performance. MULTI-GRADE OIL : Engine or gear oil that meets the requirements of more than one SAE viscosity grade classification and that can be used over a wider temperature range than a single grade oil. NAPHTHA : Generic term describing a variety of light petroleum distillates such as mineral spirits and other petroleum solvents. NAPHTHENIC : A type of petroleum fluid derived from naphthenic crude oil, containing a high proportion of closed-ring methylene groups. NEUTRAL OIL : The basis of most commonly used automotive and diesel lubricants, they are light overhead cuts from vacuum distillation. NEUTRALIZATION NUMBER : A measure of the acidity or alkalinity of an oil. The number is the mass in milligrams of the amount of acid (HCl) or base (KOH) required to neutralize one gram of oil. NEWTONIAN BEHAVIOR : The property of simple liquids by which the rate of shear is proportional to the shearing stress. This constant proportion is the viscosity of the liquid. NEWTONIAN FLOW : Rheological characteristic of a fluid where the rate of shear is directly proportional to the shearing force, as with straight grade oils that do not contain a polymeric viscosity modifier. When rate of shear is not directly proportional to the shearing force, flow is non-Newtonian, as it is with oils containing viscosity modifiers engine oil. NITRATION : The process whereby nitrogen oxides attack petroleum fluids at low temperatures, often resulting in viscosity increase and deposit formation. NLGI NUMBER/NLGI GRADE : A numerical scale for classifying the consistency range of lubricating greases, and based on the ASTM D217 worked penetration (60 strokes) at 25°C (77°F). NLGI grades are in order of increasing consistency (hardness) as follows: NLGI CONSISTENCY NUMBER WORKED PENETRATION RANGE 25°C (77°F), mm/10 or dmm 000 445 - 475 00 400 - 430 0 355 - 385 1 310 - 340 2 265 - 295 3 220 - 250 4 175 - 205 5 130 - 160 6 85 - 115 Greases both softer and harder than this consistency range are well known in industry. Such greases could bear an NLGI number such as 1.5 or 1½, but those grades are not official NLGI numbers. NO-TOX : A trademark of Bel-Ray products. Food grade industrial oils and greases for use in food processing plants. NON-NEWTONIAN BEHAVIOR : The property possessed by some fluids and many plastic solids including lubricating grease, of having variable relationship between shear stress and rate and shear. (Non-Newtonian materials, therefore, do not possess a viscosity as defined by Newton, but rather an apparent viscosity, the quantitative value of which may vary widely with varying shear rate. Conventional types of viscometers with uncontrolled shear rates will not satisfactorily measure non-Newtonian materials.) NON-SOAP THICKENER : Any of several specially treated or synthetic materials, excepting the metallic soaps of long chain fatty acids, which can be either thermally or mechanically dispersed in liquid lubricants to form lubricating grease. Some of non-soap thickeners, such as polyurea, are also called SYNTHETIC THICKENER. Certain types, such as silica, are called INORGANIC THICKENERS. OCTANE NUMBER : A measure of a fuel's ability to prevent detonation in a spark ignition engine. Measured in a standard single-cylinder, variable- compression-ratio engine by comparison with primary reference fuels. Under mild conditions, the engine measures Research Octane Number (RON); under severe conditions Motor Octane Number (MON). Where the law requires posting of octane numbers on dispensing pumps, the Antiknock Index (AKI) is used. This is the arithmetic average of RON and MON, (R M)/2. It approximates the Road Octane Number, which is a measure of how an "average" car responds to the fuel. OIL SLINGER : Device designed to prevent creepage of oil along a shaft. OILINESS/LUBRICITY : A term used to describe the ability of a lubricant to reduce friction between rubbing surface. There are no generally accepted test methods available to evaluate this property. Oiliness is mostly important in conditions of boundary lubrication and probably represents some relation to the ability of the oil to wet the bearing surfaces and to resist being rubbed off. Oiliness has no known direct relation to oil viscosity. OILLESS BEARING : Bearings made of porous metal impregnated with 10/20 percent of oil or sometimes with graphite. ORGANOCLAY BASE GREASE : A grease prepared from a lubricating fluid thickened with an organic modified naturally occurring earth or clay. OUTBOARD MOTOR : Outboard motor for a boat is developed as a self-contained unit with engine, subsidiary systems, and propeller, designed to be mounted at the stern (rear) of the craft. It is the most common method of propelling small watercraft. OXIDATION : Occurs when oxygen attacks 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. OXIDATION STABILITY : Resistance of a petroleum product to oxidation and, therefore, a measure of its potential service or storage life. OXYGENATE : An oxygen containing, ashless organic compound, such as alcohol or ether, that can be used as a fuel or fuel supplement. OXYGENATED FUELS : Fuels for internal combustion engines that contain oxygen combined in the molecule, e.g. alcohols, ethers and esters. Term also applies to blends of gasoline with oxygenates, e.g. Gasohol, which contains 10% by volume anhydrous ethanol in unleaded gasoline. PARAFFINIC : A type of petroleum fluid derived from paraffinic crude oil and containing a high proportion of straight chain saturated hydrocarbons. Often susceptible to cold flow problems. PENETRATION (GREASE) : A measure of the hardness or consistency of a solid or semi-solid material based on ASTM D217 Method (and similar methods standardized by other organizations). A grease penetrometer consists of a specially designed cone which penetrates the grease under prescribed conditions of temperature, force moving the cone, time and condition of the grease. Penetration is the number of tenths of a millimeter that the cone penetrates into the product under prescribed conditions. The ASTM definitions are given as follows:
PENETROMETER : Instrument for measuring the penetration of semi-solid substances like greases. PERCENTAGE PERMANENT VISCOSITY LOSS (PPVL) : Measure of the PVL related to the viscosity of the fresh oil; equals PVL divided by fresh oil viscosity, multiplied by 100. PERCENTAGE TEMPORARY VISCOSITY LOSS (PTVL) : Difference between the viscosity of an oil measured at low and high shear rates, divided by viscosity measured at low shear rate, multiplied by 100. All viscosities must be measured at the same temperature and using the same units (cSt or cP). PERMANENT VISCOSITY LOSS (PVL) : Irreversible reduction in lubricant viscosity due to mechanical shear in engines or laboratory test rigs. PVL equals the difference between the fresh oil viscosity and that of the degraded oil, both measured at the same temperature. PILLOW BLOCK : Denotes a block that encloses and supports a journal or shaft; a bearing. The block is used for transferring energy at 90 degrees and supports a “transfer shaft” with the use of bearings. The shaft is secured via an “off center” ring, that tightens itself onto the main bearing manifold. Pillow block is also know as “plummer block” outside of the US. PITTING : Surface cavities; may be related to fatigue, overload or corrosion. PLAIN BEARINGS : Bearings in which the motion is sliding as distinct from rolling, as anti-friction bearings, vide "Bearings". PLASTIC FLOW : Surface deformation of metal as a result of yielding under heavy load. Plastic flow differs from fluid flow in that the shearing stress must exceed a yield point before any flow occurs. PLASTICITY : That property of apparently solid material which enables it to be permanently deformed under the application of force, without rupture. POISE (P) : Measurement unit of a fluid's resistance to flow, i.e., viscosity, defined by the shear stress (in dynes per square centimeter) required to move one layer of fluid along another over a total layer thickness of one centimeter at a velocity of one centimeter per second. This viscosity is independent of fluid density, and directly related to flow resistance. POLISHING (BORE) : Excessive smoothing of the surface finish of the cylinder bore or cylinder liner in an engine to a mirror-like appearance, resulting in depreciation of ring sealing and oil consumption performance. POLYUREA GREASE : A grease made from a lubricating fluid thickened with polyurea or polyurea complex thickener. Polyurea is created by the chemical reaction between an isocyanate and an amine. POSITIVE CRANKCASE VENTILATION (PCV) : System for removing blow-by gases from the crankcase and returning them through the carburetor intake manifold to the combustion chamber where the recirculated hydrocarbons are burned. A PCV valve controls the flow of gases from the crankcase to reduce hydrocarbon emissions. POUR POINT : An indicator of the ability of an oil or distillate fuel to flow at cold operating temperatures. It is the lowest temperature at which the fluid will flow when cooled under prescribed conditions. POUR POINT DEPRESSANT : Additive used to lower the pour point or low-temperature, low shear-rate fluidity of a petroleum product. PUMPABILITY : 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. This item also is used to indicate the "resistance to flow" of grease through grease pump lines. Soft "buttery" grades are easy to pump. Hard, fibrous greases are difficult to pump. The ability of a lubricating grease to flow under pressure through the line, nozzle and fitting of a grease dispensing system. It is best indicated by the apparent viscosity at moderate rate of shear. PYCNOMETER : A device for measuring densities of liquids. PYROLYSIS : Chemical decomposition by the action of heat. QUENCHING OILS : Oils used in dipping baths to control the rate of cooling of metals, especially steel, in order to obtain desirable specific properties such as ductility, hardness, strength, etc. R&O OIL : Oil compounded with chemical agents to inhibit rust formation in turbine lubricating systems and to minimize oil oxidation. RAYLENE : A trademark of Bel-Ray products. General purpose lubricating oils. RE-REFINING : A process of reclaiming used lubricant oils and restoring them to a condition similar to that of virgin stocks by filtration, clay adsorption or more elaborate methods. RECLAIMED OILS : This term should only be applied to used oils which have been treated by such relatively simple processes as filtration or centrifuging, which aim mainly at removing foreign contaminants. REFINING : Series of processes to convert crude oil and its fractions into finished petroleum products, including thermal cracking, catalytic cracking, polymerization, alkylation, reforming, hydrocracking, hydroforming, hydrogenation, hydrogen treating, Hydrofining, solvent extraction, dewaxing, de-oiling, acid treating, clay filtration and deasphalting. RHEOLOGY : Study of the deformation and/or flow of matter in terms of stress, strain, temperature and time. The rheological properties of lubricating greases are commonly measured by penetration and apparent viscosity. RHEOPECTIC GREASE : A grease which will heavy up in consistency on being worked or agitated as little as would be caused pumping it through a grease distribution line. RIDGING : In gear teeth, a form of plastic flow characterized by a rippled appearance on the surface. RING OIL BEARING : Consists of a large diameter ring placed around the journal and dipping into an oil reservoir. The rotation of the journal causes the ring also to rotate, although at a lower speed, due to slippage, and to carry oil from the oil both to the bearing. RING STICKING : Freezing of a piston ring in its groove in a piston engine or reciprocating compressor due to heavy deposits in the piston ring zone. 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. ROLLING AND PEENING : In gear teeth, a form of plastic flow that gives the surface a hammered appearance; metal may be rolled over the teeth tips. RUST PREVENTATIVE : Compound for coating metal surfaces with a film that protects against rust. Commonly used to preserve equipment in storage. SAPONIFICATION : The process of forming soap (See definition of Soap). SAPONIFICATION NUMBER : The number of milligrams of potassium hydroxide required to react with all fats and fatty acids in a one gram sample. This is a method of determining the quality of compounding in a gear oil, steam cylinder oil, or other compounded lubricant. SATURATED STEAM : Steam that is formed in a closed vessel to contact with water is called saturated steam. Dry saturated steam is steam that carries no water in suspension. SAYBOLT VISCOMETER : Industrial viscometer of the efflux type which is standard in USA. Now, it is obsolete. There are two types - the Saybolt Universal for lube oils and the Saybolt Furol for more viscous materials. The word "Furol" is a contraction of the phrase "Fuel and Road Oils." SCOURING : Is a washing process employed in the textile industry, where they generally utilize their own formulas for manufacturing the scourable agent, which is usually an alkali and water solution SCRAPER RING : A piston ring, the leading or upper edge of which is chamfered and which is designed to return excessive oil on cylinder walls to the crank case. Mainly used in internal combustion engines. SCRATCHING : Fine abrasive furrows in the direction of sliding. SCUFFING : Abnormal engine wear due to localized welding and fracture. It can be prevented through the use of anti-wear, Extreme-Pressure and friction modifier additives. SCUFFING OF GEARS : When loads are heavy and the film strength of the oil is insufficient to support the load, momentary metallic contact occurs resulting in a ridge at the pitch line of the driven gear and a hallow at the pitch line of driving gear. In severe cases, wear of the metal takes place along the faces and flanks of the gear teeth. Also known as "Galling". SEIZING OF GEARS : An extreme case of scuffing where the lubricating film fails, and due to high local temperatures, welding of the contacting surfaces occurs. Such damaged areas, cause of course, scoring of succeeding tooth surfaces. SET : In the manufacture of a lubricating grease is the change from a fluid to a semi-fluid or plastic state. SHEAR : Stress resulting in portions of a body bending to slide one over the other. A grease is sheared by stirring. SHEAR RATE : The rate of slip within a substance engaging in flow. The average or mean shear rate in a pipe or tube is the average velocity divided by the radius of the tube. It therefore has the dimensions of the reciprocal of time and is usually expressed in the unit of reciprocal seconds (S-1). The mean shear rate is reported in the determination of apparent viscosity in ASTM D1092. SHEAR STABILITY (GREASE) : The ability of a lubricating grease to resist changes in consistency (hardness) during mechanical working. Working may be in any of several types of laboratory machines or may in actual service. This may also be called MECHANICAL STABILITY. SHEAR STABILITY INDEX (SSI) : A measure of an oil's irreversible viscosity loss attributable to the viscosity modifier when the oil is subjected to engine operation or special test conditions. Also sometimes called Permanent Shear Stability Index (PSSI), SSI is defined by the equation: SSI = 100(Vo-Vs)/(Vo-Vb), where Vo = viscosity of the unsheared oil, Vs = viscosity of the sheared oil, and Vb = viscosity of the base oil. SHEAR STRESS : The force required to cause shearing in a substance. In fluids the relation of the shear stress to the shear rate is the viscosity of the substance. SHEARING : Slipping or sliding of one part of a substance relative to an adjacent part in a solid, such action involves cutting or breaking of the crystal structure but in a fluid of plastic, shearing does not necessarily destroy the continuous nature of the substance. SILICONES : Compounds which may be likened in many respects to hydrocarbons, except that the molecular chain is made up of silicone atoms bound to a carbon. Because of their unique temperature stability characteristics, silicones widely is used for specialty greases, etc. SLUDGE : A thick, dark residue, normally of mayonnaise consistency, that accumulates on nonmoving engine interior surfaces. Generally removable by wiping unless baked to a carbonaceous consistency, its formation is associated with insolubles overloading of the lubricant. SLUMPABILITY (GREASE) : A property of some greases which makes them partially self-leveling. Greases possessing this property will be pumped from a container without the necessity of using a follower plate. (See definition of Follower Plate). This property is often confused with PUMPABILITY (See definition). SOAP : A specific type of salt formed by the reaction of fatty acid with an alkali. SODIUM COMPLEX GREASE : A grease prepared from a lubricating fluid thickened with special sodium soaps and/or complex agents. Sodium complex grease usually has better properties, such as water resistant property and high temperature property, than a regular sodium grease. SODIUM SOAP GREASE : Also called Soda Grease, a grease prepared from a lubricating fluid thickened with sodium soap. SOLID FILM LUBRICANT/SOLID BONDED LUBRICANT : Materials with inherent lubricating properties which are firmly bonded to the surface of a substrate by some methods. Those methods include a bonding agent, burnishing, mechanical impingement or vacuum deposition. SOLID LUBRICANT : See dry film lubricant. SOLUBLE CUTTING OILS : Mineral oil compounded with suitable agents to permit the formation of emulsions with water. Whilst all cutting oils act as a coolant as well as a lubricant, water is more efficient as a cooling medium than oil, and for certain types of work it is necessary to provide a combination of the two in order to secure the most satisfactory results. SOLVENT EXTRACTION : Refining process used to separate reactive components (unsaturated hydrocarbons) from lubricant distillates in order to improve the oil's oxidation stability, viscosity index and additive response. SOLVENT REFINING : A process for extracting lubricant base stocks from stripped heavy gas oil or other heavy, stripped crude stream using selective solvents such as furfural or phenol. SPALLING : Severe damage characterized by large pits, cavities and related cracks; related to overload and fatigue. SPECIFICATIONS : Prescribed limits of control tests used to maintain uniformity of a specific product. SPLASH LUBRICATION : Method of lubrication in which the oil in a bath is splashed by the moving mechanism into those parts requiring a supply of lubricant. SPUR GEAR : A cylinder, wheel or disc on the surface of which are cut parallel teeth, each in common plane with the axis. SQUEEZE FILM LUBRICATION : That state of lubrication in which surfaces thickly coated or flooded with lubricant move toward each other at sufficient speed to develop fluid pressure sufficient to support a load of short duration. Because of viscosity (or apparent viscosity), the lubricant cannot immediately flow away from the area of contact. This action occurs for example between gear teeth and between pins and their bushings. STEAM CYLINDER OILS : The steam engine is unique in that the lubricating oil is not applied directly to cylinder walls or value surfaces, but is distributed by the steam after the latter has been charged or impregnated with oil from a lubricator in the main steam line adjacent to the value chest. Steam cylinder oils must be of comparatively heavy viscosity and possess high wettability in order to ensure that the lubricating film will cling to the valve seats and cylinder walls, withstand washing off by the steam, and resist the wearing or scraping effects of valves and piston rings. For operation under wet steam conditions the oil is generally compounded. STOKE (St) : A unit of measure of kinematic viscosity defined by the ratio of the fluid's dynamic viscosity to its density. Usually expressed as centistokes (cSt), where 1 Stoke = 100 cSt and 1 cSt = 1 mm2/s. SULFURIZED CUTTING OILS : Cutting oils containing sulfur and used for difficult machining operations, such as threading and tapping at high speed, broaching, and for alloy steels that machine with difficulty. SUPER-HEATED STEAM : If more heat is added to steam after all the water it contains has been transferred into steam, the temperature of the steam will be greater than that of ordinary saturated steam having the same pressure. SURFACE TENSION : The attractive force exerted by molecules below the surface upon molecules at the surface/air interface. The strength of the surface tension various with the polarity of the liquid: high-polar substances like water have higher surface tension than low-polar substances like oils. SYNERESIS : Loss of liquid lubricant from a lubricating grease due to shrinkage or rearrangement of the structure. The shrinkage may be due to either physical or chemical changes in the thickener. Syneresis is a form of BLEEDING. SYNTHETIC LUBRICANT : Lubricating fluid made by chemically reacting materials of a specific chemical composition to produce a compound with planned and predictable properties. SYNTHETIC THICKENER : See NON-SOAP THICKENER. TACKY : A descriptive term applied to greases which appear particularly sticky or adhesive. TANK FARM : Name given to collection of oil storage tanks. TECHNICAL WHITE OILS : White oils which do not meet USP (United States Pharmacopeia) requirements, but have many industrial applications. TEMPORARY SHEAR STABILITY INDEX (TSSI) : The measure of the viscosity modifier's contribution to an oil's percentage viscosity loss under high shear conditions. Temporary shear loss results from the reversible lowering of viscosity in high shear areas of the engine, an effect that can positively influence fuel economy and cold cranking speed. TEMPORARY VISCOSITY LOSS (TVL) : Difference between dynamic viscosity measured at high shear rate compared to that determined at low shear rate. Both viscosities are measured at the same temperature. TENSILE STRENGTH : The force required to break a bar of unit cross section under tension. The tensile strength depends not only on the cohesion of the material, but also upon the consistency, and therefore, at least to some extent depends upon the rate of application of the load. TERMALENE : A trademark of Bel-Ray products. Waterproof grease for lubricating bearings exposed to water. TEXTURE (GREASE) : That property of lubricating grease which is observed when a small separate portion of it is pressed together and then slowly drawn apart. TEXTURE should be described in the following terms:
THICKENING AGENT (THICKENER) : The solid particles which are relatively uniformly dispersed to form the structure of lubricating grease in which the liquid is held by surface tension and other physical forces. THIXOTROPY (GREASE) : That property which is manifested by a decrease in consistency or softening, as a result of shearing, followed by an increase in consistency or hardening, beginning after shearing is stopped. (Thixotropic age hardening is a relatively prolonged process proportional to aging time and is seldom, if ever, complete whereas the apparent viscosity increase which occurs in non-Newtonian systems with decreasing shear rate, is instantaneous and fully reversible. Lubricating grease is both thixotropic and non-Newtonian). THRUST BEARINGS : These bearings support a load, acting in the direction of the axis of the bearing. They may be plain, anti-friction, or involve special sliding elements. TORQUE : Force which produces or tends to produce rotation or torsion "twist". TOUGHNESS : The property of yielding to force without breaking. TRACTION FLUID : Fluid displays high traction coefficients; under high stress it develops a glass-like structure, simultaneously transmitting shear forces and protecting the contacting surfaces from wear TRIBOLOGY : Science of the interactions between surfaces moving relative to each other, including the study of lubrication, friction and wear. TURBULENCE : Rapid movement of the air/fuel mixture in an internal combustion engine which affects the rate of combustion. UNSATURATED : A term applied to carbon compounds in which some of the carbon atoms are held together by double bonds or triple bonds so that these compounds are capable of combining directly with other elements or compounds. Lubricants containing unsaturated materials are usually somewhat unstable and subject to oxidation. 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. VAPOR PHASE CORROSION INHIBITOR : Corrosion inhibitor in the form of a vapor, which is made from fine, volatile powders, after vaporizing, it is absorbed by metal surfaces. VAPOR PRESSURE : Measure of the volatility of a liquid at specified temperatures and pressures (or vacuum). VARNISH : A thin, insoluble, non-wipeable film occurring on interior engine parts. Can cause sticking and malfunction of close-clearance moving parts. Called lacquer in diesel engines. VELOCITY : Time rate of motion in a fixed direction. VISCOMETER/VISCOSIMETER : An apparatus for determining the viscosity of a lubricant. VISCOSITY : Viscosity may be regarded as a measure of the internal resistance to flow of a fluid, semi-fluid or semi-solid substance. Its numerical value is based on the ratio of shear stress to the rate of shear during flow. Viscosities are usually determined by absolute or dynamic viscosity and kinematic viscosity. VISCOSITY GRADE : Any of a number of systems which characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils. The commonly used systems are ISO and SAE. VISCOSITY INDEX (VI) : Relationship of viscosity to the temperature of a fluid. It is determined by measuring the kinematic viscosities of the oil at 40 and 100°C and using the tables or formulas included in ASTM D 2270. High viscosity index fluids tend to display less change in viscosity with temperature than low viscosity index fluids. VISCOSITY MODIFIER : Lubricant additive, usually a polymer, whose function is to provide beneficial rheological properties to lubricating oils, such as reducing the tendency of an oil's viscosity to change with temperature. VOLATILITY : The tendency of a product to change form the state of liquid to that of vapor. This property is, of course, very important in gasoline. WATER RESISTANCE : The ability of a lubricating grease to withstand the addition of water to the lubricant system without adverse effects. WATER RESISTANCE is generally considered to be made up of four components as listed below.
WEAR : The removal of materials from surfaces in relative motion. Three types of wear are described below:
WET STEAM : Steam containing minute globules of water in suspension. WHITE METAL : Bearing alloy made of lead, antimony and copper. WHITE OIL or WHITE MINERAL OIL : Highly refined lubricant stock used for specialty applications such as cosmetics and medicines. White oil usually must meet USP (United States Pharmacopeia) or NF (National Formulary) requirements. WICK FEED CUPS : Lubricators consisting of oil reservoirs or cups in which one end of a wick of cotton, felt, wool, etc. dips into the oil and by capillary action drains the oil into the bearing to be lubricated. WORM GEAR : The two members of a worm gear set are known as the work and the worm wheel or gear. The worm resembles a screw, although it is really a special form of helical gear, and its teeth are referred to as threads. YIELD (OF LUBRICATING GREASE) : The amount of grease of a given consistency which may be made with a definite amount of thickening agent. As the yield increases, percent thickener decreases. YIELD POINT or YIELD STRESS : The minimum shear stress required to produce flow of a plastic material. It is estimated by the intercept of the shear stress axis of the shear stress - shear rate curve, by extrapolation of the straight portion of the curve. ZERK FITTING : A common grease fitting, one of may types of fittings used in lubrication. ZINC (ZDDP or ZDTP) : Commonly used name for zinc dialkyl dithiophosphate or zinc dithiophosphate, an anti-wear/oxidation inhibitor chemical. |
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