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Lubrication and Oil Analysis Dictionary
Category: General technical and industrial > Oil terms
Date & country: 25/09/2008, US
Words: 423

a device which converts low pressure fluid power into higher pressure fluid power.

A device which cools a gas between the compressive steps of a multiple stage compressor.

Interfacial tension
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 Standards Organization, sets viscosity reference scales.

ISO Solid Contaminant Code
a code assigned on the basis of the number of particles per unit volume greater than 5 and 15 micrometers in size. Range numbers identify each increment in the particle population throughout the spectrum of levels.

ISO Standard 4021
the accepted procedure for extracting samples from dynamic fluid lines.

Joint Industry Conference

A unit of work, energy, or heat. 1J (joule)=1 Nm) (Newton meter).

that part of a shaft or axle that rotates or angularly oscillates in or against a bearing or about which a bearing rotates or angularly oscillates.

Journal bearing
a sliding type of bearing having either rotating or oscillatory motion and in conjunction with which a journal operates. In a full or sleeve type journal bearing, the bearing surface is 360¦ in extent. In a partial bearing, the bearing surface is less than 360¦ in extent, i.e., 150¦, 120¦, etc.

Karl Fischer Reagent Method
the standard laboratory test to measure the water content of mineral base fluids. In this method, water reacts quantitatively with the Karl Fischer reagent. This reagent is a mixture of iodine, sulfur dioxide, pyridine, and methanol. When excess iodine exists, electric current can pass between two platinum electrodes or plates. The water in the sample reacts with the iodine. When the water is no l...


thousand Hertz (cycles per second)


Kinematic viscosity
the time required for a fixed amount of an 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, both at the same temperature--


a deposit resulting from the oxidation and polymerization of fuels and lubricants when exposed to high temperatures. Similar to, but harder, than varnish.

Laminar particles
particles generated in rolling element bearings which have been flattened out by a rolling contact.

Lead naphthenate
a lead soap of naphthenic acids, the latter occurring naturally in petroleum.

Light Ends
Low-boiling volatile materials in a petroleum fraction. They are often unwanted and undesirable, but in gasoline the proportion of light ends deliberately included are used to assist low-temperature starting.

Light obscuration
the degree of light blockage as reflected in the transmitted light impinging on the photodiode.

Lip seal
an elastomeric or metallic seal that prevents leakage in dynamic and static applications by a scraping or wiping action at a controlled interference between itself and the mating surface.

any substance that flows readily or changes in response to the smallest influence. More generally, any substance in which the force required to produce a deformation depends on the rate of deformation rather than on the magnitude of the deformation.

Lithium Grease
The most common type of grease today, based on lithium soaps.

Load-carrying capacity
property of a lubricant to form a film on the lubricated surface, which resists rupture under given load conditions. Expressed as maximum load the lubricated system can support without failure or excessive wear.

Load-wear index
Measure of the relative ability of a lubricant to prevent wear under applied loads; it is calculated from data obtained from the Four Ball EP Method. Formerly called mean Hertz load.

logarithm (common)

any substance interposed between two surfaces in relative motion for the purpose of reducing the friction and/or the wear between them.

The control of friction and wear by the introduction of a friction-reducing film between moving surfaces in contact. The lubricant used can be a fluid, solid, or plastic substance.

A device which adds controlled or metered amounts of lubricant into a pneumatic system.

ability of an oil or grease to lubricate; also called film strength.

Low Viscosity Index, typically below 40 VI units.


a separator that uses a magnetic field to attract and hold ferromagnetic particles.

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
strategically located in the flow stream to collect a representative sample of wear debris circulating in the system: for example, engine swarf, bearing flakes, and fatigue chunks. The rate of buildup of wear debris reflects degradation of critical surfaces.

Magnetic seal
A seal that uses magnetic material (instead of springs or a bellows) to provide the closing force that keeps the seal faces together.

a filter assembly containing multiple ports and integral relating components which services more than one fluid circuit.

Manifold filter
a filter in which the inlet and outlet port axes are at right angles, and the filter element axis is parallel to either port axis.

Material Safety Data Sheet
A publication containing health and safety information on a hazardous product (including petroleum). The OSHA Hazard Communication Standard requires that an MSDS be provided by manufacturers to distributors or purchasers prior to or at the time of product shipment. An MSDS must include the chemical and common names of all ingredients that have been determined to be health hazards if they constitut...

Media migration
material passed into the effluent stream composed of the materials making up the filter medium.

the porous material that performs the actual process of filtration. The plural of this word is 'media'.


Metal oxides
oxidized ferrous particles which are very old or have been recently produced by conditions of inadequate lubrication. Trend is important.

Metalworking lubricant
Any lubricant, usually petroleum-based, that facilitates the cutting or shaping of metal. Basic types of metalworking lubricants are: cutting and tapping fluids, drawing compounds, etc.


See Micron.

a unit of length. One Micron = 39 millionths of an inch (.000039'). Contaminant size is usually described in microns. Relatively speaking, a grain of salt is about 60 microns and the eye can see particles to about 40 microns. Many hydraulic filters are required to be efficient in capturing a substantial percentage of contaminant particles as small as 5 microns. A micron is also known as a microme...

Microscope method
a method of particle counting which measures or sizes particles using an optical microscope.



Mineral oil
oil derived from a mineral source, such as petroleum, as opposed to oils derived from plants and animals.

Mineral seal oil
A distillation fraction between kerosene and gas oil, widely used as a solvent oil in gas adsorption processes, as a lubricant for the rolling of metal foil, and as a base oil in many specialty formulations. Mineral seal oil takes its name – not from any sealing function – but from the fact that it originally replaced oil derived from seal blubber for use as an illuminant for signal lamps and ligh...

capable of being mixed in any concentration without separation of phases; e.g., water and ethyl alcohol are miscible.

Mold lubricant
A compound, often of petroleum origin, for coating the interiors of molds for glass and ceramic products. The mold lubricant facilitates removal of the molded object from the mold, protects the surface of the mold, and reduces or eliminates the need for cleaning it.

Molybdenum disulfide, a solid lubricant and friction reducer, colloidally dispersed in some oils and greases.

Molybdenum disulfide
A black, lustrous powder (MoS2) that serves as a dry-film lubricant in certain high-temperature and high-vacuum applications. It is also used in the form of pastes to prevent scoring when assembling press-fit parts, and as an additive to impart residual lubrication properties to oils and greases. Molybdenum disulfide is often called moly or molysulfide.

a type of petroleum fluid derived from naphthenic crude oil, containing a high proportion of closed-ring methylene groups.

National Aerospace Standard

National Aeronautics and Space Administration

National Electrical Code

Needle bearing
a rolling type of bearing containing rolling elements that are relatively long compared to their diameter.

National Electrical Manufacturers Association

Neutralization number
a measure of the total acidity or basicity of an oil; this includes organic or inorganic acids or bases or a combination thereof (ASTM Designation D974-58T)

Newtonian fluid
a fluid with a constant viscosity at a given temperature regardless of the rate of shear. Single-grade oils are Newtonian fluids. Multigrade oils are NON-Newtonian fluids because viscosity varies with shear rate.

National Fluid Power Association

nitration products are formed during the fuel combustion process in internal combustion engines. Most nitration products are formed when an excess of oxygen is present. These products are highly acidic, form deposits in combustion areas and rapidly accelerate oxidation.

Trade association whose main interest is grease and grease technology. NLGI is best known for its system of rating greases by penetration.

NLGI consistency grades
Simplified system established by the National Lubricating Grease Institute (NLGI) for rating the consistency of grease.

Nominal filtration rating
an arbitrary micrometer value indicated by a filter manufacturer. Due to lack of reproducibility this rating is deprecated.

Non-Newtonian fluid
fluid, such as a grease or a polymer-containing oil (e.g., multi-grade oil), in which shear stress is not proportional to shear rate.

Nonwoven medium
a filter medium composed of a mat of fibers.

Normal paraffin
A hydrocarbon consisting of molecules in which any carbon atom is attached to no more than two other carbon atoms; also called straight chain paraffin and linear paraffin.

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.

a greasy, unctuous liquid of vegetable, animal, mineral or synthetic origin.

Oil Analysis
The routine activity of analyzing lubricant properties and suspended contaminants for the purpose of monitoring and reporting timely, meaningful and accurate information on lubricant and machine condition.

Oil Consumption Ratio
Annual oil purchases divided by machine charge volume. For example, if you purchased 10,000 gallons of oil in one year and the total amount of oil that all of your machine holds is 4,200 gallons, your consumption ratio is 2.4.

Oil ring
a loose ring, the inner surface of which rides a shaft or journal and dips into a reservoir of lubricant from which it carries the lubricant to the top of a bearing by its rotation with the shaft.

A device for once-through lubrication. Three common types of oilers are: drop-feed, wick-feed, and bottle-feed; all depend on gravity to induce a metered flow of oil to the bearing. The drop-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...

that property of a lubricant that produces low friction under conditions of boundary lubrication. The lower the friction, the greater the oiliness.

Oiliness Agent
An additive, usually polar in nature, used to improve the lubricity of a mineral oil. Now usually called a boundary lubrication additive.

Open bubble point
the differential gas pressure at which gas bubbles are profusely emitted from the entire surface of a wetted filter element under specified test conditions.

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. They are found in such applications as mining and construction machinery, punch presses, plastic and rubber mills, tube mills, and rotary kilns. Open gears require viscous, adhesive lubricants that bond to the metal surfaces and resist run-o...

Occupational Safety and Health Administration

Outside-mounted seal
A mechanical seal with its seal head mounted outside the seal chamber that holds the fluid to be sealed. Outside seals have the pumped fluid`s pressure at their I.D.

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 anti-oxidant. An oxidation inhibitor may work in one of these ways: (1) by combining with and modifying peroxides (initial oxidation products) to render them harmless, (2) by decomposing the peroxides, or (3) by rendering an oxidation catalys...

Oxidation stability
ability of a lubricant to resist natural degradation upon contact with oxygen.

pressure - psi

Paper chromatography
a method which involves placing a drop of fluid on a permeable piece of paper and noting the development and nature of the halos, or rings, surrounding the drop through time. The roots of this test can be traced to the 1940s, when railroads used the 'blotter spot' tests.

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 ...

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.

Parallel Systems
Lubrication systems where the dispensing devices are connected to the main line in 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.

Particle density
an important parameter in establishing an entrained particle's potential to impinge on control surfaces and cause erosion.

Particle erosion
occurs when fluid-entrained particles moving at high velocity pass through orifices or impinge on metering surfaces or sharp angle turns.

Particle impingement erosion
a particulate wear process where high velocity, fluid-entrained particles are directed at target surfaces.

Particles made up of a wide range of natural materials (e.g., pollen, dust, resins), combined with man-made pollutant (e.g., smoke particles, metallic ash); in sufficient concentrations, particulates can be a respiratory irritant.

Unit of pressure in the metric (SI) system.

Pascal`s Law
A pressure applied to a confined fluid at rest is transmitted with equal intensity throughout the liquid and that pressure is considered to act at right angles to each surface contacted by the fluid.