Glossary

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 the fluid’s density equals...
Absorbent polymeric materials filter water from turbine oil – just as filters are used to remove particulate contamination from such oils. Oil is passed through a polymeric filtration system. The...
ASTM D974: A measure of the acidic constituents present within the lubricant. Most rust inhibitors used in turbine oils are acidic and contribute to the acid number of the new. Increases from the new...
Water depletes or diminishes the performance of lubricant additives, including antioxidants, AW, EP, rust inhibitors, dispersants, detergents, and demulsifying agents. It hydrolyzes, agglomerates,...
Occurs when the oil film becomes so thin that the roughest points of the opposing surfaces begin to touch each other. It occurs normally during both break-in and route service as the parts wear...
Water lowers oil’s interfacial tensions, which can cripple its air-handling ability, leading to aeration and foam. Air weakens oil films, increases heat, induces oxidation, causes cavitation, and...
 Agglomeration, whereby the moist sticky particles collide due to the turbulence and adhere to each other forming agglomerates, is essential for the rewet process.
One of two types of additives used to reduce foaming in petroleum products: silicone oil to break up large surface bubbles; and various kind of polymers that decrease the amount of small bubbles...
See oxidation inhibitor.
An additive that minimizes wear caused by metal-to-metal contact during conditions of mild boundary lubrication (e.g., stops and starts, oscillating motion). The additive reacts chemically with, and...
Visual assessment for sample clarity, cloudiness, separations, visible debris or free water, etc. 
Standard unit of measurement in the petroleum industry, equivalent to 42 standard U.S. gallons, or approximately 35 Imperial gallons.
One of a broad class of compounds that react with acids to form salts plus water.
See neutralization number.
Base Oil - is the name given to lubrication grade oils initially produced from refining crude oil (mineral base oil) or through chemical synthesis (synthetic base oil).
A primary refined petroleum fraction, usually a lube oil, into which additives and other oils are blended to produce finished products.
High viscosity oils, highly refined and dewaxed to make clear products of good color, produced from residual stocks, or bottoms; used for blending with lower viscosity oils.
Occurs when metal is removed from parts by the impact of collapsing cavitation bubbles on the surfaces. Cavitation itself is associated with partial vacuums formed in a liquid by sudden changes in...
Gravity alone is often not enough to separate water from oils in a reasonable amount of time. In this case, purifying systems called centrifugal separators are used to “push” the water from the...
ISO: 4406:99: Turbine journal bearing clearances (10 to 20 microns) and hydraulic servovalve clearances (2 to 5 microns) dictate the need for clean oil. Excessive bearing wear and servovalve...
Sometimes the surface tension between oil and water increases to a point where neither gravity nor centrifugal force is sufficient to remove the water from the oil. In this situation, a coalescence...
ASTM D2500: New turbine oils are typically light in color. Darkening will occur with age and service. Periodic comparisons of the sample color are useful in spotting significant and/or rapid...
The ability of petroleum products to form a homogeneous mixture that neither separates nor is altered by chemical interaction.
Any of a wide variety of mechanisms designed to compress air or other gas to produce useful work.
ASTM D130: The copper strip test measures the potential corrosive nature of a lubricant and the possible difficulties with yellow metals, such copper and brass or bronze components, within a system....
Corrosion is commonly called rusting. Free water and soluble water both result in increased corrosive potential of acids. Results are etched and pitted surfaces and in worst cases formation of...
Results when chemical reactions cause corrosion or oxidation of part surfaces and part movement or fluid pressure dislodges material from this surface layer. This type of wear is associated with rust...
Fluid, usually of petroleum origin, for cooling and lubricating the tool and work in machining and grinding.
Ability of an oil to separate from water, as determined by ASTM D 1404 or D 2711.
ASTM D1401: This test measures the ability of a lubricant to separate from water. New turbine oils are designed to have good water separability characteristics. Polar contaminants influence turbine...
The mass of a unit volume of a substance. Its numerical value varies with the units used. See specific gravity.
The best way to eliminate water from any lubricant application is to stop it from getting into the lubricant supply or into the machinery in the first place. In some cases, this is very challenging,...
Minimum voltage required to produce an electric arc through an oil sample, as measured by test method ASTM D 877; hence, an indication of the insulting (arc preventive) properties of a transformer...
The ability of an oil to emulsify with water. The oil becomes suspended in the water in minute particles in a more or less stable form.
Intimate mixture of oil and water, generally of a milky or cloudy appearance.
Lubricant additive that prevents sliding metal surfaces from seizing under conditions of extreme pressure (EP). At the high local temperatures associated with metal-to-metal contact, an EP additive...
Occurs when cyclic or repeated load stresses cause cracking, spalling, and pitting of the component part surfaces. This type of wear is more commonly associated with rolling element bearings and...
Property of a lubricant which acts to prevent scuffing or scoring of bearing surfaces.
A portable device which can be connected to a unit's hydraulic system to filter water and/or other contaminants out of the hydraulic system fluid.
Fire resistant hydraulic fluids are specially formulated lubricants that are more difficult to ignite and do not propagate a flame from an ignition source.  Fire resistant should not be confused...
Minimum temperature of a petroleum product or other combustible fluid at which vapor is produced at a rate sufficient to yield a combustible mixture. Specifically, it is the lowest sample temperature...
An additive which causes foam to dissipate more rapidly. It promotes the combination of small bubbles into large bubbles which burst more easily.
Occurrence of a frothy mixture of air and a petroleum product (e.g., lubricant, fuel oil) that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil...
ASTM D892: Measurement of the oil’s tendency to foam and the stability of the foam after it is generated. Some foaming is a typical occurrence and antifoaming agents are blended into the oil...
Fourier Transform Infrared: Infrared Spectroscopy is applied to measure organic molecular components. FTIR can be applied to monitor for additive depletions (antioxidants), organic degradation...
Resistance to the motion of one surface relative to another. The amount of friction is dependent on the smoothness of the contacting surfaces, as well as the force with which they are pressed...
Unit of liquid volume used in Canada, England, and other countries. Defined as the volume of ten pounds of water at 68 degrees Fahrenheit. One imperial gallon equals 1.20095 U.S. gallons.
Unit of liquid volume equal to 231 cubic inches.
The most basic method of water removal is gravity separation. As the name suggests, gravity can separate fluids because of its stronger pull on the more dense fluid, which separates it from the less...
Measure of the available energy content of a fuel, under controlled conditions specified by test method ASTM D 240 or D 2382.
Chemical compound of hydrogen and carbon; also called an organic compound. Hydrogen and carbon atoms can be combined in virtually countless ways to make diversity of products.
This is sometimes called embrittlement or blistering. Water is attracted to microscopic fatique cracks by capillary action. Water breaks down and liberates atomic hydrogen and causes further crack...
Ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water.
Bearings depend upon oil viscosity to provide critical clearance under a load. Water globules pulled into a bearing load zone reduce surface clearance and result in bumping or rubbing of opposing...
Additive that improves the performance of a petroleum product through the control of undesirable chemical reactions. See corrosion inhibitor, oxidation inhibitor, rust inhibitor.
Chemical compound, usually mineral, that does not include hydrocarbons and their derivatives.
Test for contaminants in used lubricating oils, under conditions prescribed by test method ASTM D 893.
ISO
International Standards Organization.
International systems, approved by the International Standards Organization (ISO), for classifying industrial lubricants according to viscosity. Each ISO viscosity grade number designation...
Absolute viscosity of a fluid divided by its density at the same temperature of measurement. It is the measure of a fluid’s resistance to flow under gravity, as determined by test ASTM D 445.
Lethal concentration, 50% mortality; a measure of inhalation of toxicity. It is the concentration in air of a volatile chemical compound at which half the test population of an animal species dies...
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.
Control of friction and wear by the introduction of a friction-reducing film between moving surfaces in contact. The lubricant used may be fluid, solid, or plastic substance.
Ability of an oil or grease to lubricate; also called film strength. Lubricity can be enhanced by additive treatment.
(additive, contaminant and wear, ASTM D5185) - all of these should be within the turbine and oil manufacturers specifications.
Water is known to promote the growth of microorganisms such as fungi and bacteria, which can form thick biomass suspensions over time that can plug filters and interfere with oil flow. Microbes also...
Any petroleum oil, as contrasted to animal or vegetable oils. Also, a highly refined petroleum distillate, or white oil, used medicinally as a laxative.
Capable of being mixed in any concentration without separation of phases.
Also called neut number, an indication of the acidity or alkalinity of an oil; the number is the weight in milligrams of the amount of acid (hydrochloric acid [HCI]) or base (potassium hydroxide [KOH...
Water is highly polar and has the ability to attach to oil impurities that are also polar (for example, oxides, spent additives, particles, carbon fines, and resin) to form sludge balls and emulsions...
The combination of a substance with oxygen. A reaction in which the atoms in an element lose electrons and the valence of the element to create longer chain molecules with higher molecular...
Substance added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or storage life; also called an antioxidant.
Resistance of a petroleum product to oxidation; hence a measure of its potential service or storage life. There are a number of ASTM test to determine the oxidation stability of a lubricant or fuel,...
ISO 11171: A count of the number of particles present greater than given micron sizes per unit volume of fluid. The results reflect the solid contaminants present and are applied to assess fluid...
PPM
Parts per million.
Occurs once the solubility threshold (saturation point) has been crossed or if there is a drop in temperature which reduces the solubility of the fluid. As additional oxidation by-products (free...
Force per unit area, measured in kilopascals (kPa) or pounds per square inch (psi).
Oil that serves as a temporary or permanent component of a manufactured product.
PSI
Pounds per square inch.
An analysis technique for purposely isolating and measuring the specific lubrication degradation by-products responsible for varnish formations. This is not a measure of varnish already formed; it...
Immersion of a heated manufactured steel part, such as a gear or axle, in a fluid to achieve rapid and uniform cooling. Petroleum oils are often used for this purpose. Quenching provides hardness...
R&O
Rust and oxidation-inhibited term applied to highly refined industrial lubricating oils formulated for long service in circulating systems, compressors, hydraulic systems, bearing housing, gear cases...
Technology to determine antioxidant levels. The antioxidants are measured by electrically charing a prepared sample and measuring chemical changes within it. The technique uses a solvent to...
Study of the deformation and flow of matter in terms of stress, strain, temperature, and time. The rheological properties of a grease are commonly measured by penetration and apparent viscosity.
(Previously RBOT). One of the most important properties of turbine oil is its oxidation stability or resistance. RPVOT test is a controlled, accelerated oxidation of a lubricant to determine the...
ASTM D665 A: Rust particles act as oxidation catalysts and can cause abrasive wear in journal bearings.
A lubricant additive for protecting ferrous (iron and steel) components from rusting caused by water contamination or other harmful materials from oil degradation.
ASTM D665: Antirust protection provided by the lubricant is of significant importance for turbine systems. Antirust inhibitors will deplete during lubricant service and can also be affected by...
Deformation which occurs when parallel planes of a body are displaced relative to each other in a direction parallel to themselves.
Rate at which adjacent layers of a fluid move with respect to each other, usually expressed as reciprocal seconds.
Frictional force overcome in sliding one “layer” of fluid along another, as in any fluid flow. The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with...
In gasoline engines, a soft, black, mayonnaise-like emulsion of water, other combustion by-products, and oil formed during low-temperature engine operation.  Another term for sludge is varnish....
Describes fluid's capacity to hold the varnish producing molecules in solution (dissolved). Solubility is directly affected by temperature. As more oxidation by-products are generated the fluid...
For petroleum products, the ratio of the mass of a given volume of product and the mass of an equal volume of water, at the same temperature. The standard reference temperature is 15.6 Degrees...
Spectrochemical Analysis: ASTM D6595: Specific trace metals are measured and monitored for wear and corrosion levels, airborne or internally generated contaminants, oil additives, and water treatment...
Petroleum oil containing no additives.
The ash content of fresh, compounded lubricating oil as determined by ASTM D 874. Indicates level of metallic additives in the oil.
Lubricating fluid made by chemically reacting materials of a specific chemical composition to produce a compound with planned and predictable properties; the resulting base stock may be supplemented...
Ability to resist chemical degradation at high temperatures.
(ASTM D974)– Should be no more than 0.3 to 0.4 above the new oil value.
See neutralization number.
Science of the interactions between surfaces moving relative to each other. Such interactions usually involve the interplay of two primary factors: the load, or force, perpendicular to the surfaces,...
The most comprehensive test package available for turbine oils. It covers the majority of the testing outlined in the TOQ, in addition to determining the varnish potential, additive levecls and...
ASTM D4378: to maintain effective lubrication of all parts of the turbine and guard against the onset of problems associated with oil degradation and contamination. 
Test includes spectrochemical and physical properties analyses, total acid number (TAN), appearance, water content, color, rust resistance capability, particle count analysis, copper corrosion, water...
ASTM D943: This test attempts to determine the expected turbine oil life by subjecting the test oil to oxidative stress using oxygen, high temperatures, water and metals catalysts, all of which...
Using a Vacuum Dehydrator is the only way to separate free, emulsified and dissolved water. It is an effective way to purify turbine, compressor, hydraulic, lubricating or quenching oils and...
This technique takes advantage of the fact that the vapor pressure of water is lower than that of most turbine oils. In this technique, the contaminated oil/water mixture is passed through a vacuum...
ASTMD.02C.01: A thin, hard, lustrous, oil-insoluble deposit, composed primarily of organic residue, & most readily definable by color intensity. It is not easily removed by wiping with a clean,...
ASTM D445: Viscosity is the most important characteristic of turbine oil and can be readily affected by more types of influences than any other property. Maintaining the proper viscosity is crucial...
Empirical, unitless number indicating the effect of temperature change on the kinematic viscosity of an oil. Liquids change viscosity with temperature, becoming less viscous when heated; the higher...
Lubricant additive, usually a high molecular weight polymer, that reduces the tendency of an oil to change viscosity with temperature. Multigrade oils, which provide effective lubrication over a...
Expression of evaporation tendency. The more volatile a petroleum liquid, the lower its boiling point and the greater its flammability.
ASTM D6304: Testing for water, particularly in steam turbines, is important because water is a precursor to oil exidation and rust formation. It can be more accurate than simple weight loss because...
http://globalindustrialsolutions.net/glossary/ppmASTM D1744: Water contamination within turbines adversely affects the lubricants by acting as a catalyst for oxidation and rapidly depleting water...
Pressurized water sprays can directly wash an additive out of a lubricant zone. Lubricant density is lower than that of water, and to much free water can displace lubricant if allowed to accumulate...
The attrition or rubbing away of the surface of a material as a result of mechanical action.
Highly refined straight mineral oil, essentially colorless, odorless, and tasteless. White oils have a high degree of chemical stability.