Copy of `Lubrication and Oil Analysis Dictionary`

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Lubrication and Oil Analysis Dictionary
Category: General technical and industrial > Oil terms
Date & country: 25/09/2008, USA
Words: 421

abbreviation for 'American Gear Manufacturers Associations,' an organization serving the gear industry.

a society for developing standards for materials and test methods.

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 break down 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 gage 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 viscosi...

Absorbent filter
a filter medium that holds contaminant by mechanical means.

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
A test contaminant used to assess both filters and the contaminant sensitivity of all types of tribological mechanisms.

a container in which fluid is stored under pressure as a source of fluid power.

in a restricted sense, any substance containing hydrogen in combination with a nonmetal or nonmetallic radical and capable of producing hydrogen ions in solution.

Acid number
The quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize the acidic constituents in 1 g of sample.

Acid sludge
The residue left after treating petroleum oil with sulfuric acid for the removal of impurities. It is a black, viscous substance containing the spent acid and impurities.

Acid treating
A refining process in which unfinished petroleum products, such as gasoline, kerosene, and lubricating oil stocks, are contacted with sulfuric acid to improve their color, odor, and other properties

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.

A device used to convert fluid energy into mechanical motion.

A chemical substance added to a petroleum product to impart or improve certain properties. Common petroleum product additives are: antifoam agent, anti-wear additive, corrosion inhibitor, demulsifier, detergent, dispersant, emulsifier, EP additive, oiliness agent, oxidation inhibitor, pour point depressant, rust inhibitor, tackiness agent, viscosity index (VI.) improver.

Additive level
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.

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.

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.

a soft, white, non-ferrous alloy bearing material composed principally of copper, antimony, tin and lead.

Background contamination
The total of the extraneous particles which are introduced in the process of obtaining, storing, moving, transferring and analyzing a fluid sample.

Microorganisms often composed of a single cell.

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.

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.

a unit of liquid volume of petroleum oils equal to 42 U.S. gallons or approximately 35 Imperial gallons.

a material which neutralizes acids. An oil additive containing colloidally dispersed metal carbonate, used to reduce corrosive wear.

Base number
The amount of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide, required to neutralize all basic constituents present in 1 g of sample

Base Oil
A base oil is a base stock or blend of base stocks used in an API-licensed engine oil.

Base stock
the base fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants.

Any quantity of material handled or considered as a `unit” in processing. I.e., any sample taken from the same `batch` will have the same properties and/or qualities.

a 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.

Bellows seal
A type of mechanical seal which utilizes bellows for providing secondary sealing and spring-type loading.

Bernouilli`s theory
If no work is done on or by a flowing, frictionless liquid, its energy, due to pressure and velocity, remains constant at all points along the streamline.

Beta Rating
the 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.

the ratio of the number of particles greater than a given size in the influent fluid to the number of particles greater than the same size in the effluent fluid, under specified test conditions (see 'Multi-Pass Test').

Bevel Gear
A straight-toothed gear with the teeth cut on sloping faces and the gear shafts at an angle (normally a right angle)

Additive designed to inhibit the growth of microorganisms in liquids

The chemical breakdown of materials by living organisms in the environment. The process depends on certain microorganisms, such as bacteria, yeast, and fungi, which break down 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. Most petroleum products typically ...

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.

The separation of some of the liquid phase from a grease

The process of mixing lubricants or components for the purpose of obtaining the desired physical and/or chemical properties (see compounding)

leakage of combustion gases between a piston and the cylinder wall into the crankcase in an automobile


Corporate Average Fuel Economy

eccentric shafts used in most internal combustion engines to open and close valves.

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.

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.

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 piston 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.

Carbon Type
The distinction between paraffinic, naphthenic, and aromatic molecules. In relation to lubricant base stocks, the predominant type present.

Carbonyl iron powder
a contaminant which consists of up to 99.5% pure iron spheres.

A cancer-causing substance. Certain petroleum products are classified as potential carcinogens OSHA criteria. Suppliers are required to identify such products as potential carcinogens on package labels and Material Safety Data Sheets.

Cartridge seal
A completely self-contained assembly including seal, gland, sleeve, mating ring, etc., usually needing no installation measurement.

Case drain line
A line conducting fluid from a component housing to the reservoir.

a substance that initiates or increases the rate of a chemical reaction, without itself being used up in the process.

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.

A highly alkaline substance such as sodium hydroxide.

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 violent collapse of a vapor bubble. Cavitation can occur in a hydraulic system as a result of low fluid levels that draw air into the fluid, produ...

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 coll...

cubic centimeter

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.


a unit of absolute viscosity. 1 centipoise = 0.01 poise.

a separator that removes air from the system fluid through the application of bubble dynamics.

removing air from a liquid, usually by ultrasonic and/or vacuum methods.

the progressive failure of a machine or lubricant.

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.

the ability of a fluid that is insoluble in water to separate from water with which it may be mixed in the form of an emulsion.

An additive that promotes oil-water separation in lubricants that are exposed to water or steam

the mass of a unit volume of a substance. Its numerical value varies with the units used.

The depletion of additives expressed as an approximate percentage.

oil-insoluble materials that result from oxidation and decomposition of lube oil and contamination from external sources and engine blow-by. These can settle out on machine or engine parts. Examples are sludge, varnish, lacquer and carbon.

Depth filter
a filter medium that retains contaminants primarily within tortuous passages.

Inflammation of the skin. Repeated contact with petroleum products can be a cause.

opposite of absorption or adsorption. In filtration, it relates to the downstream release of particles previously retained by the filter.

in lubrication, either an additive or a compounded lubricant having the property of keeping insoluble matter in suspension thus preventing its deposition where it would be harmful. A detergent may also redisperse deposits already formed.

Detergent oil
Is a lubricating oil possessing special sludge-dispersing properties usually conferred on the oil by the incorporation of special additives. Detergent oils hold formed sludge particles in suspension and thus promote cleanliness especially in internal-combustion engines. However detergent oils do not contain `detergents” such as those used for cleaning of laundry or dishes. Also detergent oils do n...

Removal of wax from a base oil in order to reduce the pour point.

Dielectric Strength
a measure of the ability of an insulating material to withstand electric stress (voltage) without failure. Fluids with high dielectric strength (usually expressed in volts or kilovolts) are good electrical insulators. (ASTM Designation D 877.)

Differential pressure indicator
an indicator which signals the difference in pressure between any two points of a system or a component.

Dirt capacity
the weight of a specified artificial contaminant which must be added to the influent to produce a given differential pressure across a filter at specified conditions. Used as an indication of relative service life.

in lubrication, a term usually used interchangeably with detergent. An additive, usually nonmetallic ('ashless'), which keeps fine particles of insoluble materials in a homogeneous solution. Hence, particles are not permitted to settle out and accumulate.

a filter element intended to be discarded and replaced after one service cycle.

Dissolved air
Air which is dispersed in a fluid to form a mixture.

Dissolved gases
those gases that enter into solution with a fluid and are neither free nor entrained gases.

Dissolved water
Water which is dispersed in the fluid to form a mixture.

Distillation method
a method involving distilling the fluid sample in the presence of a solvent that is miscible in the sample but immiscible in water. The water distilled from the fluid is condensed and segregated in a specially-designed receiving tube or tray graduated to directly indicate the volume of water distilled.

the fluid leaving a component.