El ABC de los lubricantes: ¡En la web y como aplicación!
De la A a la Z, de los recubrimientos antifricción al aceite regenerado, el ABC de los lubricantes de BECHEM abarca muchos aspectos químicos y físicos entorno a los lubricantes y sus aplicaciones.
Procedure to determine the flash point of flammable liquids in a range of -30 °C to 70 °C in a closed cup according to Abel. Method according to Abel-Pensky (DIN 51755) is similar.
[Lat. Abrasio = scratching]. Material loss by fine and flexible abrasive solid particles when two surfaces are sliding on each other.
[French] (= Association des Constructeurs Europeéns d'Automobiles). European Automobile Manufacturers Association in the field of operating fluids.
Polymer with elastomeric properties from ethyl acrylate or copolymer with additional monomers, e.g. ethylene (ethene).
Thermosetting polymer, produced from three different monomers.
[French] (= Attestation de conformité sanitaire). French approval for products to be used in contact with drinking water.
Sulfur containing chemical compound, which reacts at temperatures of +100 °C or or lower with copper forming copper sulphide.
Additives are active ingredients which are added to lubricants in order to achieve or improve special features of lubricating base oils or to minimize negative properties. Additives are e.g. antioxidants, defoamers, EP-additives, AW-additives, demulsifiers, dispersing agents, corrosion inhibitors and viscosity improvers, etc.
Tacky, adhesive and often high-viscous lubricating oils with tackifiers. For easier application they are often diluted with readily volatilizing solvents.
Chemical modification of substances resp. lubricants by influences such as aerial oxygen, temperature, light (general: radiation) and by the catalytic effect of metal and other contaminations.
The ageing behaviour of industrial lubricating oils is an important criterion which can be determined according to different procedures: For lubricating oils the tendency to form Conradson carbon residues can be measured by feeding air according to DIN 51352 T1 or feeding air in the presence of ferrous (III) oxide (for turbine oils TDL) according to DIN 51352 T2. To characterise the ageing behaviour of steam turbines and hydraulic oils, the increase in neutralisation number when introducing oxygen in the presence of water, steel and copper is determined according to DIN 51587 or DIN EN ISO 4263-1 (TOST procedure). For industrial gear oils the TOST test according to DIN EN ISO 4263-4 is slightly modified and evaluated by means of the change in viscosity.
(= American Gear Manufacturers Association). The AGMA-Specification includes lubricant recommendations for open and closed industrial gears. The gear oils are divided into 9 viscosity ranges.
Ability of lubricating oils to release entrapped air (German: Luftabscheidevermögen, LAV). Important property in gear oils and hydraulic fluids to prevent foaming problems. The air-release property of an oil indicates the velocity of releasing dispersed air bubbles which influence the compressibility of the fluid and cause malfunctions in hydraulic systems. The air-release capacity is determined according to the Impinger method. ";
Alcohols are hydrocarbons the molecules of which contain one or more OH-groups, such as ethanol, methanol, isopropanol with one OH-group and ethane diol (ethylene glycol), propane triol (glycerine) with one or more OH-groups.
Aliphatic hydrocarbons are saturated and unsaturated hydrocarbons. They can contain straight or branched chains and cyclic (ring-type) molecules, however no aromatic compounds. Saturated aliphates with one or more double bonds are called olefines (alkenes, dienes), with one or more triple bonds we call them alkines.
Not exactly defined designation for substances the solution of which shows an alkaline reaction (pH > 7). These are e.g. alkali and alkaline earth metals such as sodium, lithium, calcium and barium. They are used for neutralisation of organic and inorganic acids (phenols, sulphuric acid, etc.) and for the production of metal soaps for lubricating greases.
In organic chemistry Alkanes are saturated hydrocarbons without multiple bonds (also called paraffines). The basic structure consists of straight (n-alkanes) or branched molecular chains (iso or neo alkanes). These saturated hydrocarbons form a homologous series with the general formula CnH2n+2. Cyclic saturated molecules are called cycloalkanes. The general formula is CnH2n.
Procedure of organic synthesis for the attachment of alkyl groups (group of interconnected carbon and hydrogen atoms) to hydrocarbons. Alkyl groups are transferred from one molecule to the other. Conventional chemical synthesis to produce raw materials for the petrochemical industry.
Test apparatus for the analysis of gear oils, lubricating greases, solid substances dispersions, pastes and metal working fluids. Extreme pressure properties and wear behaviour in the mixed friction range by means of hydraulic load of the test shaft up to breakage are analysed (indication of maximum load during breakage).
Mixture of different, in most cases organic acids, saponified with aluminium hydroxide.
Mixtures of alkaline, in most cases organic salts (mixtures of different, mostly organic acids, saponified with aluminium hydroxide) of the aluminium hydroxide act as thickener. They excel in good water resistance, excellent adhesive properties, good pump ability, low oil separation and high drop point. Their worked stability is rather moderate. This type of grease is often used as food grade lubricant and multi-purpose grease in the steel industry.
Aluminium soap grease has good adhesive properties, excellent water resistance, a low drop point and a poor worked stability. An organic acid (in most cases fatty acid) saponified with aluminium hydroxide is used as thickener.
Classification letters for standard lubricating oils (regular oils) according to DIN 51502.
Temperature in °C at which a solution (homogenized by heating) with equal volume fractions of oil and aniline will get cloudy by cooling and segregation. When comparing two mineral oils the oil with the lower aniline point has a polar character and thus the better solution properties for additives.
Properties to reduce abrasive wear by formation of a reaction layer on the surface of the friction partners under pressure and temperature.
Oils and greases with anti-corrosion properties to protect metal surfaces against corrosive impact of humidity, atmospheric oxygen and aggressive media, e.g. acids.
Anti-friction coatings are lubricant dispersions which in their formulation resemble common industrial varnishes. An organic solvent or water contains solid lubricants instead of pigments as well as resins as bonding agents. In most cases molybdenum disulfide, graphite and PTFE are used, partly also as nanoparticles. After evaporation of the solvent and curing of the binder a touch-dry coating is produced. In addition to the selection of the individual raw materials, the pigment volume concentration is decisive for lubricity and corrosion protection. AFC are preferrably applied by spraying and dipping on the carefully degreased surfaces. Other application possibilities include the varnish drum method, immersion centrifuges, electrostatic and automatic spraying, printing, roller coating, as well as various drying and curing methods.
Microscopically small microcapsules filled with a lubricating oil are embedded in a coating layer. Under load these microcapsules release the lubrication oil at the friction or lubricating point, a lubricating film between the friction partners is formed (see: functioning of anti-friction coatings with microcapsule technology
Additives (AW additives) based on organic compounds, reducing abrasive wear by formation of an adsorption layer and/or reaction layer under pressure and temperature on metal surfaces. These additives reduce wear in the mixed friction range at low temperatures by physisorption like fatty acids, fatty oils (polar additives) and high temperatures by formation of a reaction layer like metal dithiophospates as well as other sulfur and/or phosphorus containing compounds.
Antioxidants, also called oxidation inhibitors, are chemical compounds which can delay or prevent undesired reactions with oxygen or other oxidative processes. They are added to lubricants in order to delay the ageing process of the lubricant.
[Greek]. Apparatus to determine the density according to DIN 51757: submersible spindle.
Aromatic hydrocarbons are planary, unsaturated cyclic (ring-type) hydrocarbons with conjugated (connected) double bonds.
Residue which remains from combusion (ashing) of the organic part e.g. of lubricants. Ash consists of the oxides and carbonates of the inorganic components (mineral compounds), in case of addition of sulphuric acid (sulfate ashes) also of the sulfates of the mineral compounds.
(= American Society for Testing and Materials). American institution for standardisation.
Method to determine chemical elements e.g. in lubricants.
Special gear oils to be used in automatic gears with excellent product features such as high shear stability, good viscosity-temperature behaviour, high oxidation stability, excellent load carrying ability with defined friction characteristics, low foaming and good air release properties.
(= Anti Wear Additive). Additives based on organic compounds to reduce wear. An adsorption layer on metal surfaces is formed by physicochemical forces which offers protection against wear. These additives reduce wear in the mixed friction range at low temperatures by physisorption like fatty acids, fatty oils (polar, surface active additives), as well as additives forming a reaction layer like metal dithiophosphates and extreme pressure additives in form of sulfur, chlorine and phosphorus compounds, etc.
With this test the ageing behaviour of gear, hydraulic, insulating and turbine oils under influence of copper and heat is determined. The result shows the dielectric dissipation factor, copper soap number and sludge content.
Bacterial attack of a medium or substrate which often occurs with water mixed metal working fluids (emulsions, solutions). The presence of organic components, the high water content and salinity level, the good aeration and heat from the metal working process create excellent growth conditions. Bacterial attack in coolants in most cases leads to a decrease in the pH-value and thus to corrosion problems as well as the formation of unpleasant smell, increased foaming and finally to the phase separation of emulsions (creaming). To avoid these problems metal working fluids in most cases contain bactericides, fungicides and bacteriostatic additives
Mixture of different, in most cases organic acids, saponified with barium hydroxide.
Lubricating greases with good water and steam resistance, excellent corrosion protection properties, high load carrying ability and high drop point. Suitable for low and high temperatures where mixtures of different, in most cases organic acids, saponified with barium hydroxide are used as thickener. They are resistant to weak acids and bases and of toxicological concern.
International cubic measure. While the imperial barrel is no longer used, the US barrel is still common in the petroleum industry since the beginning of oil production. Still today petroleum is quoted in dollar per barrel on the international markets.
1 Barrel (1 bbl) = 42 US-Gallon (42 gal) = 159 Litre (exactly: 158,9873)
Main component of oil containing lubricants, in most cases mineral oil, but may also include polyalphaolefin, ester, polyglycol etc. Various lubricant properties, such as oxidiation resistance, elastomer compatibility, viscosity-temperature-behaviour, low and high temperature properties, additive solubility and response are determined by the selection of the base oil resp. the base oil mixture. In lubricants mineral oils as well as native and synthetic oils are used as base oils.
Batchwise (discontinuous) production (mixing and additivation) of mixtures and preparations in heatable stirred vessels. Common production method for lubricants. In rare cases lubricants are produced continuously by inline blending (simultaneous addition of base oils and additives into a tube-shaped mixing line which is directly connected to the storage tank) or other continuous processes since this will limit the flexibility of the lubricant industry to offer a large variety of products.
Registered trademark of CARL BECHEM GMBH, Hagen, the oldest German lubricant manufacturer (company foundation in 1834). BECHEM develops, produces and sells high-performance lubricants and additives based on latest tribological knowledge all over the world.
Certificate of the Belgian Federation for the Water Sector for products in contact with drinking water.
Mixture of swellable siliceous mineral with layer structure. Suitable as inorganic thickener to produce lubricating greases with good high temperature behaviour. No drop point, incompatible with other lubricating grease. Difficult to improve the grease performance by additives.
Cyclic hydrocarbon with the molecular formula C6H6. Most simple variant of the aromatic hydrocarbons characterized by the presence of a planary structure of one or more cyclic systems with conjugated (connected) double bonds. Formerly used as a solvent, benzene has been replaced in this application after the confirmation of its carcinogenic potential by toluene (methylbenzene) and xylene (isomers of dimethylbenzenes).
Hydrocarbons extracted from crude oil, in a boiling range from approx. 25 °C to approx. 210 °C (including petroleum up to approx. 280 °C): We distinguish between the following qualities: Naphtha as initial product for petrochemical processes, special and white spirit as solvent, detergent, such as e.g. petroleum ether, white spirit, FAM-regular petrol and petrol for safety lamps, petrol for Otto engines, turbine fuel (kerosene) and aviation petrol.
The denominations biolubricants and bio hydraulic oils are not generally determined. The following definition is meanwhile established: "Biolubricants and bio hydraulic oils mainly consist of renewable raw materials and are readily biodegradable.”
Property to resist microbial degradation.
[Lat.] High-molecular weight, semi-solid to solid mixtures of hydrocarbons derived as a residue from the vacuum distillation of the crude oil. Bitumen is used for the production of asphalt, roofing paper and coating products for building protection.
Blackening oils are used for blackening (burnishing) of steel surfaces. Burnishing is a process to increase the adhesive strength for further surface treatments (e.g. coating, varnishing).
A process during which the base oil contained in a lubricating grease separates from the soap structure and flow out (bleed).
Production of mixtures and preparations by blending different raw materials to one finished product without chemical reacation (exception: neutralisation reactions). The blending process can be discontinuous in stirred vessels (see batch blending), by inline blending or other continuous processes.
Lubricating greases in brick, block or briquet form of the NLGI grades 5 and 6. These very solid greases are today no longer used in practice.
German eco label for products with environmental advantages. The "Blue Angel" is the best known and first environmental label worldwide which is awarded by an independent commission for environmentally friendly services and products since 1978. The "Blue Angel" is awarded for 90 product categories. The responsible agency is the RAL German Institute for Quality Assurance and Certification. The exact denomination of the "Blue Angel" for hydraulic fluids is: RAL UZ 79.
Liquids of high purity consisting of only one substance are boiling at a defined temperature, the boiling point, up to the total evaporation of the substance. If the liquid substance is contaminated with another fully soluble liquid substance, the mixture does not boil at a defined temperature, but in a boiling temperature range up to total evaporation.
We talk about boiling retardation if under certain conditions liquids are heated up to temperatures above the boiling point without boiling. Water can be heated to 110 °C without forming any vapour bubbles by evaporation. The metastable state can, however, lead to a risky situation since already small vibrations might form a bigger gas bubble which will deflagrate from the vessel. This effect will mainly occur in high, narrow vessels, e.g. test tubes, since the liquid has a higher temperature at the bottom than on the top. Boiling retardation is favoured by a high purity of the liquid substance as well as by local overheating caused by poor mixing and plane and smooth walls of the vessels. Possible remedies are stirring equipments, boiling stones or boiling capillaries.
State of friction with an intense contact of the roughness peaks of the friction partners in the range of low relative speed between the partners. The state of boundary friction is the subsequent state following solid friction when increasing the relative speed from v = 0. A further increase in relative speed leads to the state of mixed friction with a partial separation of the roughness peaks of the friction partners and finally to the state of fluid friction with a complete separation of the roughness peaks. Due to the intense metal contact between partners heavy wear occurs in the boundary friction range. Coming from the fluid friction or mixed friction range, the state of boundary friction can be achieved by reducing the relative speed of the friction partners and by increasing temperature or load, leading to a breakdown of the lubricating film.
Moment (force) occuring at the transition from static friction to rolling or sliding friction .The breakaway torque has to be expended to overcome the static friction between two friction partners and to beginn a rolling or sliding motion.
Voltage which is required to induce flow of current in a dielectric. In case of (insulating or transformer) oils the voltage (kV) is determined according to DIN 57370-2 at which an oil layer of 2,5 mm will break down between two standardized electrodes. Important characteristic for transformer and insulating oils.
Oils for heat treatment of steels to adjust defined hardness. Based on the high ageing resistance and particular additive system dark deposits on the heat-treated parts in the quenching process are avoided.
Light, highly viscous lubricating oil (in most cases 450 to 700 mm² at 40 °C) extracted from the residue of the vacuum distillation of crude oil, good lubricating properties.
The test method according to Brugger describes the behaviour of lubricants in tribological systems where mixed friction between the friction partners of steel occurs. Depending on the lubricant properties the rotating test ring produces wear areas of different sizes on the stationary test cylinder. From this wear area the load carrying capacity of the lubricant is calculated in N/mm². Suitable for medium to highly viscous lubricants.
Classification letter for lubricating oils, describes requirements of circulation oils according to DIN 51517-1.
Lubricating greases for the lubrication of wire ropes to prevent friction of the individual wires and to protect against corrosive atmosphere. Cable greases often contain graphite or molybdenum disulfide additives.
Mixture of different, in most cases organic acids, saponified with calcium hydroxide.
Water resistant lubricating grease with good corrosion protection properties and high load carrying capacity. Mixtures of different, in most cases organic acids, saponified with calcium hydroxide are used as thickener. Being exposed to higher temperatures for a longer period of time, the consistency will increase.
Organic acid (mostly fatty acid), saponified with calcium hydroxide.
The CAS-No. is a number allocated by the Chemical Abstract Service to identify a chemical compound.
Substances which accelerate chemical reactions whereby they are not consumed during the process. Catalysts reduce activation energy of chemical reactions.
[Lat. cavum: cave, hollow space]. Cavitation is the formation and breakdown of vapour-filled hollow spaces in fluids. It occurs at a pressure level below the vapour pressure of the liquid by fluid flow or oscillation. The breakdown of the hollow spaces (implosion) and the resulting extreme pressure fluctuations lead to severe wear at the surfaces of constructions parts (gears, bearings, pumps).
(= Committee of Common Market Automobile Constructors). No longer existing association of European automobile producers which has been replaced by the ACEA.
(=Co-ordinating-European-Council for the Development of Performance Tests for Lubricants and Engine Fuels). Association of European automobile producers to define test methods for engine lubricants and fuels.
Eldest test method to confirm ready biodegradability (previous version CEC L-33-T-82).
Centipoise (acc. to J. L. M. Poiseuille) is a no longer used measuring unit of dynamic viscosity. Today mPa x s (millipascal second) acc. to SI-system. 1cP = 1 mPa x s (Pa = Pascal).
Today no longer used measuring unit of kinematic viscosity. Today mm²/s acc. to SI-system. 1cSt = 1 mm²/s.
Classification letters for slideway oils which contain anti-ageing and anti-corrosion additives to reduce friction and wear.
The lubricant remains unchanged even under the influence of various substances such as acids and bases.
Property, not to react chemically with other substances or compounds.
Absence of chlorine containing additives.
Chlorine containing elastomer, generated by polymerisation of 2-chloro-1,3-butadiene.
Classification letters for gear oil according DIN 51517-2 containing antioxidants and anti corrosion additives (Class C oils plus anti corrosion additives).
Method to determine the flash and fire point of lubricants in open cup system.
Cloud point means the start of the precipitation (crystallisation) of long-chain paraffinic hydrocarbons at low temperatures in a mineral oil or saturated long-chain esters in ester oils. Based on the formation of insoluble crystals the oil gets cloudy which can be measured under defined conditions according to DIN ISO 3015.
"Classification letters for gear oil according DIN 51517-3 containing anti corrosion additives, antioxidants and additives to reduce friction and wear (Class CL oils plus additives to reduce friction and wear).
Welding of metallic friction partners at room temperature, supported by high contact area and contact pressure.
Colloids are formed by very small particles (solid particles or droplets) which are finely dispersed in an ambient medium (dispersion medium: solid, liquid or gaseous phase), such as e.g. solutions of soap, oil-in-water emulsions, suspensions, etc. The particle size is in general between 1 µm and 10 µm.
The colours of liquid products from mineral oils (e.g. diesel, fuel oil, lubricating oil, paraffine) or synthetic oils are determined by the colour index according to different standards. 16 colour grades from 0,5 to 8,0, which are measured in transmittance, are defined according to ISO 2049 or ASTM D 1500. The Sayboldt colour index for products lighter than 0,5 acc. to ASTM D 1500 is measured in accordance with DIN 51411 (ASTM D 156). Other common colour indices are measured according to Gardner (DIN EN ISO 4630-1, ASTM D 1544 and D 6166) as well as APHA (DIN ISO 6271, ASTM D 1209).
The colour of lubricating oils does not represent any quality characteristic and is influenced by the type of base oil and type and quantity of additives. The colour of used lubricating oils are additionally influenced by ageing condition and impurities (darker colour compared to fresh oils). The same applies to lubricating greases and pastes. Mineral oils of highly refined qualities are light-coloured, as well as oils with a lower additive content. The colour is determined by the colour index.
Lubricating oils V to be applied in compressors and vacuum pumps. In most cases special base oils with low evaporation loss. Depending on the additive level classified acc. to DIN 51506 in lubricating oils VB, VC, VBL, VCL and VDL.
Method to analyse the properties of mineral oils to form coke residues in the absence of air. The values prove possible clogging of e.g. diesel injection nozzles, nozzles of fuel oil burners or formation of residues in lubricating oils. During the test the sample is combusted under air shortage, and the percentage of carbon residue in the initial sample is indicated.
The consistency (stiffness, solidity) of greases and pastes is determined by the method of cone penetration according to ISO 2137. The penetration of a standardised cone and shaft in a predefined quantity of lubricant obtained within 5 seconds is measured. In case of soft greases the cone will penetrate deeper into the grease (high penetration figure), if the grease is stiffer the cone will penetrate less deep (lower penetration figure). The classification will then be done based on the penetration depth, given in 0.1 mm units (see NLGI grades).
Characterisation of the relationship between temperature and consistency of greases and pastes.
Lubricating greases, gear, hydraulic and motor oils suitable for construction machinery.
Force per area in the contact of the friction partners.
Fluids providing cooling and lubrication in metal working operations (metal removal) and partially in forming operations of (in most cases) metal workpieces. There are many traditional denominations: cutting oil, soluble oil, grinding oil, fully synthetic oils, metal working fluids, etc. According to DIN 51502 and DIN 51385 coolants are divided into two main groups:
1. Non water miscible coolants: Are applied undiluted (grinding oil, deep drilling oil, machining oil, cutting oil, etc.)
2. Water miscible coolants (water mixed metal working fluids): Are applied diluted with water.
a) Emulsifiable coolants (in application: coolant emulsion): Contain water insoluble components (in most cases as base oil).
b) Water soluble coolants (in application: coolant solution): Contain only water soluble components.
General description for water-free fluids for heat removal in various applications, e.g. in rectifiers and metal working processes (metal removal) - also see coolants.
To detect possible corrosive impact of lubricating greases, oils and coolants on copper and copper alloys (e.g. brass) caused by the additives - e.g. EP additives - contained in lubricants.
Fractions from the vacuum distillation of crude oil with a narrow boiling range (narrow-cut fractions). These core fractions should be used as base oil for certain applications which require a preferably low tendency to evaporation (compressor oils, quenching oils).
Corrosion inhibitors prevent rust formation on metal surfaces in a physical way by forming surface layers by adsorption of polar substances which avoids the access of hydrogen and oxigen to the metal surface. Prevention of rust by neutralisation of acids. Typical corrosion inhibitors are salts of carboxylic and dicarboxylic acids, sulfonates and waxes.
Simple qualitative method to detect water in mineral oils. When heating oils (mineral oils, ester oils, synthetic oils) in a test tube or spatula above 100 °C water will quickly evaporate with a characteristic crackling noise. For the quantitative detection of water in lubricants the Karl-Fischer-Titration is the common test method (DIN 51777, DIN EN ISO 12937, ISO 6296).
Capability of lubricants to penetrate into cracks, gaps and fittings.
Crude oil is the term for the untreated petroleum (crude petroleum) directly recovered from the earth. Light yellow up to black in colour, crude oil mainly consists of hydrocarbons. Crude oil has been formed by the decay of organic materials from dead plants and algae etc. under pressure and temperature. It is of great importance as fossile energy source for the production of fuels. Furthermore crude oil is a crucial raw material for most products of the chemical industry, e. g. plastic materials and pharmaceuticals.
Cutting oils are non water miscible coolants (metal working oils) which are used for machining operations in metal working for lubrication, heat flow and chip transport.
Lubricating oils Z which, as superheated steam, saturated steam and wet steam cylinder oils can be used for the lubrication of vapour carrying parts such as cylinders, slides and valves. In most cases these are dark mineral oils of high viscosity (800 - 1500 mm²/s at 40 °C) without additives.
[German] (= Deutsches Arzneimittelbuch). German pharmacopeia: inventory of rules and test methods for quality, testing, storage and nomenclature of pharmaceutical substances and preparations.
Complying with the requirements of the 10th issue of the German pharmacopeia.
Grease to absorb noises and vibrations.
Surface active substances or formulations which prevent foam formation or guarantee the rapid foam decay, e.g. polysiloxanes or polyglycol ether. They avoid foam formation of fluids in case of strong shear forces or air ingress. Foam formation impairs the lubricating properties (e.g. ageing resistance, load carrying ability, etc.) of a lubricant.
Particle size (droplets, solid particles) of the dispersed phase of a dispersion.
Properties of hydraulic and lubricating oils not to incorporate but to separate water resp. to avoid emulsification. The demulsifying behaviour of hydraulic and lubricating oils is tested acc. to DIN 51599 resp. DIN ISO 6614.
Substances which guarantee the phase separation of an emulsion or to separate water from oil.
Ratio of mass m and volume V at a certain temperature T. Equivalent to specific weight.
Contaminants consisting of dirt and/or carbon black resulting from e.g. oil ageing, mechanical wear, combustion residues, high thermal stress, etc.
Surface active substances (wetting agents). They are used in lubricants to prevent agglomeration of oil-insoluble combustion residues and reaction products from ageing processes (black carbon, coke, resinous and asphalt containing oxidation products), to keep them in suspension in order to avoid deposition of sludge and thickening of oils.
Electrically non-conductive or very weakly conductive materials with non-movable charge carriers (ions, electrones); in metal working name for so-called spark erosion fluids used for cooling of parts in electrical discharge machining, as insulation fluid and to remove abrasive particles.
Maximum electrical field strength in an isolator without electrical breakdown. Quotient of breakdown voltage (Ud) and the lowest electrode distance (kV/mm).
[German] (= DIN Deutsches Institut für Normung e.V.). German Institute for Standardization, located in Berlin.
Certificate of the German Technical and Scientific Association for Gas and Water.
Dip slides help to trace bacterial or fungal growth in water mixed coolants. Bacteria and fungi can cause corrosion, poor filterability, decrease in the pH-value and odour problems (see bacterial attack).
Charge transfer in groups of atoms lead to separate centers of charge in molecules resulting in a dipole moment. In polar molecules a permanent charge transfer generates a permanent electric dipole moment. Unpolar molecules can be polarized by electric or magnetic fields resulting in charge transfer with separate cebters of charge which are called induced dipoles. Thus e.g. metal surfaces can polarize unpolar oil molecules by their electromagnetic fields so that the molecules can be adsorbed by the surface.
are surface-active substances (wetting agents). They are used in lubricants to prevent agglomeration of oil-insoluble combustion residues and reaction products from ageing processes (black carbon, coke, resinous and asphalt containing oxidation products, etc.), to keep them in suspension in order to avoid deposition of sludge and thickening of oils.
Mixing (or mixture) of unsoluble substances into each other.
Dispersing agents are surface-active substances, such as anti-settling agents, wetting agents, detergents, emulsifiers, which reduce the interface tension, i.e. optimize wetting. In contrast to dispersants, which are applied in oils, the name "dispersing agent" is mainly in use for water based formulations and paints.
Multi-phase system with a continuous phase (dispersant) and at least one more dispersed phase. Examples: suspension (solid particles in a fluid), emulsion (liquid droplet in a fluid), aerosols (mist: liquid droplets in gas, smoke: solid particle in gas, smoke).
Distillates are groups of substances separated according to their boiling points arising from distillation after cooling (condensation). In case of fractionated distillation of crude oil these are hydrocarbon mixtures of a certain boiling range.
Thermal process for the separation of liquid mixtures depending on the range of the individual components. The mixture to be separated is continuously heated while the vapour of the boiling component is passed into a cooled condensor and collected as distillate. In case of collecting different fractions of distillate, the process is called fractionated distillation. By using columns with several column plates (column trays) or packed columns, the performance of the separation process is significantly increased in view of multiple condensation and repeated distillation. This large-scale distillation in columns is also called rectification and is the most important procedure in crude oil refining which is carried out in two steps:
During atmospheric distillation the crude oil is heated up to approx. 360 °C in the column at the bubble trays, resulting in several fractions of fuel and gas oil.
For the vacuum distillation, the residue of atmospheric distillation is then again heated to 360 °C under vacuum in a special vacuum distillation column. The collected fractions are used as lubricating and heavy fuel oils. The residues of vacuum distillation are used for the production of bitumen or brightstock oils.
(=Department of Transportation). US authority, is responsible for the US specification of brake fluids.
Lubricating greases or oils which are used for metal forming operations (e.g. wires, tubes, profiles). Partially with a high additive content, e.g. EP-additives.
Temperature, at which a grease thickener starts to melt or degrade. Under defined conditions a grease sample is heated until it becomes liquid and a drop falls through the hole of the test tube. The temperature measured at this moment is called dropping point (DIN ISO 2176).
[German] (= Deutsche Vereinigung des Gas- und Wasserfaches). German Technical and Scientific Association for Gas and Water, determines the requirements for lubricants in drinking water taps.
The viscosity characterizes the flow properties of a liquid or a gas. Viscosity can also be described as internal friction of the fluid. Higher viscosity means low fluidity and low viscosity high fluidity. The viscosity depends on the molecular structure of the fluid components. Depending on the molecular structure varying attractive forces between the molecules of the fluid occur. High attractive forces result in high viscosity, low attractive forces in low viscosity of the fluid. In a simplyfied model, a fluid can be considered as a stack of molecular layers. In the state of flow the molecule layers are sliding along each other. To overcome the resistance between the molecules against displacement caused by the attractive forces, a certain power is required. The dynamic viscosity is defined as constant of proportionality in the correlation between required force and induced velocity gradient (shear rate).
Dynamic viscosity = shear stress / shear rate. The dynamic viscosity is measured in Pascal second (Pa • s = 1 Ns/m²).
Under the influence of gravity the kinematic viscosity is the ratio of dynamic viscosity and density (i.e. e.g. in case of free flow measurement by means of capillary viscosimeter, see Ubbelohde-Viscosimeter).
Classification letter for ester based lubricants according to DIN 51502, e. g. used as CLP E.
European certification and label for products with environmental advantages. Relatively new European environmental label (also called EU-Marguerite) to label especially environmentally friendly products. For lubricants the following factors are the basis to obtain this label: biodegradability, ecotoxicology and the use of hazardous substances as well as the application of renewable raw materials. Besides the "Blue Angel" the EU environmental label "EURO MARGUERITE" represents a decisive purchase argument for the consumer, e.g. a readily biodegradable hydraulic oil.
This type of hydrodynamic lubrication occurs during the contact of heavily loaded friction partners in relative motion (e.g. rollers and gears). The theory of elastohydrodynamic lubrication also considers the elastic deformation of the friction partners. This type of lubrication is characterized by the narrowing of the lubricating gap at the end of the contact zone. Based on the EHD theory the influence of lubrication, e.g. with regard to tooth damages, is determined.
Test procedure to analyse lubricating greases with regard to their anti-corrosion properties in roller bearings, plain bearings and on sliding surfaces in the presence of water under practical conditions.
Ability of an oil to form an emulsion with water.
Emulsifiers are surface-active substances, e.g. tensides, which are responsible for the formation and stability of an emulsion of water and oil by reducing surface tension of the water. Emulsifier molecules consist of an oil-soluble lipophilic part (hydrocarbon chain) and a water-soluble, hydrophilic part. Depending on the chemical structure of the hydrophilic part they are classified into anionic, cationic, non-ionic and mixed ionic emulsifiers.
Dispersion where the continuous as well as the dispersed phase consists of fluids which are not soluble in each other. The dispersed phase is distributed in the dispersant in the form of droplets resp. micelles. In case of mineral oils e.g. with water under stabilisation by emulsifiers. We differ between oil-in-water (O/W, oil droplets in water) and water-in-oil emulsions (W/O, water droplets in oil, inverse emulsion).
Engine oils are used for lubrication of combustion engines and are divided into SAE-classes according to their viscosity. Depending on the additives they fulfil various specifications (e.g. MIL, CCMC) and classifications (e.g. API, ACEA).
Former measuring unit of viscosity. The determination of viscosity in degrees Engler indicates the ratio to the efflux time of water from an Engler viscosimeter at 20 °C.
EP lubricating oils or greases contain extreme pressure additives (reaction layer forming additives and/or solid lubricants) to increase the load bearing capacity. These additives react with the metal surface under the extreme pressure and temperature conditions in the lubricating gap and reduce friction by forming a reaction layer.
Chemical compound, derived from chemical reaction between alcohols and acids (in most cases organic acids/fatty acids) under release of water. Native esters (alcohol component glycerin: triglycerides) are the main components of animal and vegetable greases and oils. In case of synthetic esters at least one of the two components is of synthetic origin or made from native raw materials by synthesis. In view of the higher polarity of the esters, their higher affinity to metal surfaces results in improved lubricating properties compared to mineral oil. Native esters have an inferior temperature and ageing stability in comparison to mineral oils. Based on the variety of combination possibilities the group of synthetic esters is very extensive. ";
Elastomeric polymer, at a percentage of ethylene of 65 % or higher with thermoplastic properties.
European environmental label (also called EU-Marguerite) to label especially environmentally friendly products. For lubricants the following factors are the basis to obtain this label: biodegradability, ecotoxicology and the use of hazardous substances as well as the application of renewable raw materials.
The agency is located in Helsinki and is responsible for registration, evaluation, authorization and restriction of chemical substances in order to guarantee uniform processes within the European Union. These so-called REACH-procedures (see REACH) are intended for additional information on chemical substances in order to guarantee that these are properly used and that the competitiveness of the European industry is maintained.
Volatility of lubricants and base oils under defined conditions. The evporation loss increases with rising temperature and depends on viscosity, actually the molar mass, for chemically similar base oils, respectively on the degree of refining and mixing ratio of the different base oil components for mineral oils. Measurement is done according to DIN 51581 (method acc. to Noack) for one hour at 250° at a slight vacuum. Depending on the flash point measurement can also be done at lower temperatures. DIN 58397 T1 (lubricating greases) – DIN 51581 (mineral oil products).
Lubricant additives which, under the influence of pressure and temperature, form a reaction layer on the surface of the friction partners to reduce friction and wear and to prevent cold welding of the friction partners. They are added to gear oils, motor oils, hydraulic oils, metal working oils and greases to increase the load bearing capacity and wear protection in the mixed friction range. EP-additives are e.g. zinc dialkyl dithiophosphates, tricresyl phosphates, organic phosphates, sulfur and nitrogen compounds, today rarely chlorine compounds.
Lubricating oils or greases contain extreme pressure additives (reaction layer forming additives and/or solid lubricants) to increase the load bearing capacity in the boundary and mixed friction range. These additives react with the metal surface under the extreme pressure and temperature conditions in the lubricating gap and reduce friction by forming a reaction layer. High-pressure lubricating oils are used as gear oils and above all as metal working oils.
Classification letter according to DIN 51502 for lubricants containing solid lubricants.
Fatty acids are organic acids (monocarboxylic acids) with a carbon chain length of C4 to C30 derived from animal or vegetabel oils and fats respectively produced by chemical synthesis. They are applied to reduce friction or as basis for the synthesis of emulsifiers, synthetic esters, EP/AW additives, grease thickeners, etc. As friction modifier they are mainly used in the lower temperature range since other EP additives cannot form any reaction layers du to the lack of activation energy.
(= Food and Drug Administration). US Authority.
With the FE 8 test rig the influence of the lubricant (lubricating greases and oils) on the friction and wear behaviour of roller bearings is measured under influence of temperature, axial load and rotational speed. After 500 h both test bearings are dismantled and wear of cage and rolling elements is gravimetrically determined and indicated in mg.
The analysis of lubricating greases on the roller bearing test apparatus FE 9 is carried out to determine the upper service temperature limit under practical test conditions. According to DIN 51825 for lubricating greases K (roller bearing greases) a test run with 5 bearings at the desired upper temperature at 6000 rpm and 1,5 kN axial load has to be passed (F50 = 100 h).
Indicates the lowest temperature relating to a defined pressure at which the vapour phase of a fluid with constant heating by ignition in an open cup will burn on for at least 5 s.
The flash point according to DIN 51755, DIN ISO 2592 and DIN EN ISO 2719 indicates the temperature at which under fixed conditions the air-oil-vapour mixture above the liquid surface ignites for the first time but does not constantly burn by the approach of a defined igniting flame. The flash point is relevant for safe operation and serves as indicator to classify inflammable fluids into hazard classes.
Determines the temperature at which a cooled, homogenous mixture from 10 % refrigerator oil and 90 % refrigerant show first visible clouding in transmitted light.
The flow characteristics depend on the molecular structure of the substances and the interactions between the molecules. For the so-called Newtonian fluids, e.g. water, the flow behaviour can be described via a linear, time-independent correlation according to Newton's law of viscosity. This means that viscosity does not depend on the applied shear forces. For the non-Newtonian fluids the viscosity changes depending on the applied shear forces and on the duration of the shear forces. If the viscosity decreases with increasing shear force, the effect is called shear thinning (structural viscosity). If the viscosity increases with increasing shear force, the phenomenon is called shear thickening (dilatancy). In both cases the viscosity returns to its original value after removing the shear force. If the viscosity increases at a constant shear force, the effect is called rheopexy (example: cement). The opposite behaviour of decreasing viscosity at a constant shear force is called thixotropy (example: ketchup, modern non-drip wall colours). Rheopexy and thixotropy are both time-dependent, and for this reason the viscosity does not return immediately to its original value after removing the shear force, but after a certain time of relaxation.
For the determination of the flow pressure according to Kesternich, a small amount of grease in a test nozzle is cooled down to the test temperature and then extruded through the nozzle by pressurized air. The flow pressure indicates the consistency of lubricating greases, characterizes the flow behaviour and is used to determin the lower temperature limit if special maximum pressures are observed (1400 mbar for lubricating greases K according to DIN 51825).
State of friction with a complete separation of the friction partners by a liquid film leading to ideal hydrodynamic lubrication. Since there is no contact between the roughness peaks of the friction partners, no mechanical wear occurs in this state of friction. Achieving hydrodynamic lubrication depends on the viscosity of the lubricant, relative speed between the friction partners, shear rate and temperature.
Collective name for fluorinated polymers with elastomeric properties.
Rinsing and cleaning of machine parts and systems prior to start or oil change. In general the lubricant intended for filling should be used for rinsing and cleaning before starting the machine, if possible in a lower viscosity or with detergent additives.
Analysis of the emission behaviour, i.e. the tendency to release substances into the ambient air.
Efflux viscosimeter (flow cup viscosimeter) to determine the viscosity of fluids such as lacquers, paints, resins and liquids of similar viscosity. The liquid is filled in a conical cup with a defined nozzle at the bottom. Viscosity can be determined by means of the cup volume, nozzle diameter and the measured efflux time of the fluid. The test method is described under ASTM D 1200:1994, ISO 2431 and DIN 53211 (in October 1996 this standard was cancelled).
Oils used in the construction industry as separating agent for wood or steel moulds in concrete processing.
Test unit to determine the weld load (welding of test balls) and the wear characteristics (size of wear scars) of lubricating greases (parts 4 and 5) and lubricating oils (parts 4 and 5) as well as to determine the shear stability of polymer containing lubricating oils (part 6). Parts 2 and 3 are often applied for coolant lubricants. The system consists of a rotating ball (1450 min-1), which, in pyramidal configuration, slides on three fixed balls at different loads. To determine the weld load (parts 2 and 4) the load is increased step by step until these four balls will weld. The test per load stage is carried out for 60 s. As a result the last passed load stage (OK load) and the load stage during welding (weld load) is indicated in Newton (N). To determine the wear characteristics (parts 3 and 5) the size of the wear scar is indicated in mm. DIN 51350 T1 – T6, DIN EN ISO 20623.
[Lat. fractio: fraction, fractional amount], in petrochemistry fraction describes the part of distillation products extracted in a certain distillation temperature range. Fractions are hydrocarbon mixtures with different boiling points of atmospheric distillation and vacuum distillation of the crude oil (see distillation).
Corrosion phenomenon (tribocorrosion), which occurs in tribosytems with oscillating loads. Fretting corrosion can often be found at screw connections, linear guidings, bearing seats and spindles.The oscilliating movements will destroy the lubricating film which results in direct metallic contact between the asperities of the friction partners. As a consequence, wear occurs. Contact of the asperities results in cold welding, abrasive material wear, crack formation and tribo-chemical reactions of the formed metal particles with oxygen (oxidation, corrosion), which leads to strong wear of the material fit. Fretting corrosion can be prevented by a complete separation of the metal surface, e.g. by using solid lubricants.
Friction is the physical force which acts opposing a relative motion of two friction partners in contact to each other. The forms of friction can be distinguished according to the type of motion (static friction, sliding friction, rolling friction) or according to the states of friction (solid friction, boundary friction, mixed friction, fluid friction).
Dimensionless quotient of friction force Ff and normal force Fn. A low friction coefficient means low friction.
µ = Ff / Fn
Also called coefficient of friction, frictional coefficient, COF. Formula symbol µ or more modern f.
Force generated by the contact of two friction partners in relative motion in opposite direction to the driving force.
To improve the friction value. Additives for lubricants to reduce friction resp. to adjust defined friction behaviour or to prevent stick-slip. As friction modifiers fatty acids and their derivates, organic amines, amine phosphates, etc. are used.
In rotational system equivalent to the friction force.
without using mineral oil in the lubricant formulation.
[German] (= Forschungsstelle für Zahnräder und Getriebe). Gear Research Centre, belongs to the Institute for Machine Elements at the Technical University of Munich, Germany.
Test method for gear lubricants and hydraulic oils using the FZG gear test rig (e.g. FZG test method A/8.3/90 for relative scuffing load-carrying capacity). A set of two test gears of a spur gear runs in an oil bath at a defined temperature and load. The load is increased stepwise by adding weight plates to achieve a maximum of 12 (14) load stages. After each load stage the wear loss of the gear is determined gravimetrically and the gear surfaces are examined visually. For HLP hydraulic oils according to DIN 51524-2 load stage 10 has to be passed, for CLP gear oils according to DIN 51513-3 load stage 12 has to be passed.
Dimension, English gallon (Imperial gallon = Imp.gal.) = 4.54609 litre; American gallon (US liquid gallon = US.liq.gal.) = 3.785311784 litre, 42 US.liq.gal = 1 barrel
Chromatographical method for the separation and analysis of gases and undecomposed vaporizable substances, which, after evaporation in the injector, are transported by an inert carrier gas via a separating column to the detector. Various detection methods to identify and quantify the separated substances are available (e.g. thermal conductivity, flame ionization, mass spectrometry and infrared spectroscopy) acc. to DIN 51405, DIN 51422-1 and 2, DIN 51619.
Stringy, soft to semi-fluid greases (NLGI 0, 00, 000 and 1), thickener in most cases metal soaps, for gears and gear motors.
Lubricating oils for gears.
1. for industrial gears: DIN 51509, 51 517 T 1/T 2/T 3 (Schmieröle/lubricating oils C, CL, CLP).
2. for automotive gears acc. to API GL 1 to GL 6; SAE-classes: DIN 51512.
System of a solid substance, which is finely dispersed in a liquid, forming a sponge-like structure.
Lubricating greases with a polymeric, chemically modified silicium dioxide, in most cases transparent appearance.
[German] (= Gesellschaft für Tribologie e. V). Association of members from industry, universities, research centres and service companies to discuss subjects of tribology and lubrication.
(= Globally Harmonised System of Classification and Labelling of Chemicals), all chemical substances and preparations are classified and labelled according to their hazardous properties prior to marketing. By identifying hazardous properties and special labelling with hazard symbols, human health and the environment shall be protected against harmful effects. The GHS establishes for the first time a worldwide uniform system for the classification and labelling of chemical substances. In all countries of the European Union the classification and labelling of substances according to GHS is obligatory since December 1, 2010. During a transfer period until June 1, 2015, the MSDS has to show the old labelling as well as the new GHS label. Preparations have to be classified and labelled according to GHS from June 1, 2015.
"Glycoles are dioles (bivalent alcohols), e.g. ethylene glycol (ethanediol), propylene glycol (1,2-propanediol), diethylene glycol, polyglycoles with higher chain lengths. In view of their freezing point depressing properties, ethylene glycol, propylene glycol and diethylene glycol are often used as additives for cooling fluids, polyglycoles as base oils for high-performance lubricants.
Graphite containing greases: graphite is a stable form of the chemical element carbon. Its planar layer structure offers excellent gliding behaviour; it is well suitable as solid lubricant, e.g. in lubricating greases.
Grey staining describes a defined failure mode on tooth flanks of gears. Areas of very small pittings (micropittings) which cannot be recognized as single pit marks, but as grey stains on the metal surface.
Grinding oils are non water miscible coolants for grinding of metal surfaces, in most cases based on low-viscous mineral oils (kinematic viscosity up to approx. 10 mm²/s at 40 °C, in special cases up to approx. max. 30 mm²/s at 40 °C) or synthetic hydrocarbons (PAO). Tailored to the special requirements of the grinding process they produce a very fine grinding surface pattern.
Ageing process of lubricants and base oils producing polymeric reaction products of high molecular weight leading to a strong increase in viscosity resp. consistency.
[Arab.]. The term "halal" characterizes any product, material or process which is permitted, acceptable or lawful according to Islamic law. Food grade lubricants can be certified by authorized certifying bodies as "halal" when selected raw materials and production equipment are used and when contamination by forbidden ("haram") raw materials can be excluded. By labelling proudcts with a "halal" certificate compliance with Islamic law during the production process of materials and food can be ensured.
Property to form stable emulsions, solutions and dispersion in hard water (high water hardness) resp. to prevent the formation of deposits with hard water.
Classification letters for polyalphaolefin based lubricants according to DIN 51502, e. g. used as CLP HC.
Oils (mineral or synthetic oils) with good temperature and oxidation stability, high initial boiling point, low vapour pressure, good resistance to low temperatures as well as high flash point which are used for cooling or heating in technical equipment, such as reactors and heat exchangers.
Classification letters according to DIN 51502 for synthetic ester based hydraulic fluids.
Corrosion protection test of cast iron in the presence of steel chips for water miscible or water mixed coolants.
Classification letters according to DIN 51502 for trigylceride based (native ester based) hydraulic fluids.
Classification letters according to DIN 51502 for fire resistant hydraulic fluids type A: HFAE - oil in water emulsions, HFAS - aqueous solutions.
Classification letters according to DIN 51502 for fire resistant hydraulic fluids type C: aqueous polymer solution (water glycol).
Classification letters according to DIN 51502 for fire resistant hydraulic fluids type D: fluids free of water, subgroup U - ester based.
Classification letters for hydraulic oils according to DIN 51524-1, containing antioxidants and anti corrosion additives.
Classification letters for hydraulic oils according to DIN 51524-2, containing antioxidants, anti corrosion additives and additives to reduce friction and wear.
Classification letters according to DIN 51502 for hydraulic oils with detergent properties.
Low-viscous machining oil (non water miscible coolant) for honing (machining process in metal working with geometrically non defined cutting edge). Viscosity approx. 2 to 10 mm²/s at 40 °C.
Classification letters for hydraulic oils with high viscosity index (min. 140) according to DIN 51524-3, containing antioxidants, anti corrosion additives and additives to reduce friction and wear.
Product derived from the combination of different technologies.
Hydraulic fluids are used in hydraulic systems for power transmission and control. The different types are classified according to ISO 6743-4. Base oil options include: mineral-oil based hydraulic oils (requirements according to DIN 51524), fire-resistant hydraulic fluids (requirements according to DIN EN ISO 12922) and biodegradable hydraulic fluids (requirements according to DIN 15380).
At high operating pressures of >200 bar in hydraulic systems the potential exists for large quantities of hydraulic fluid to be released in the event of a leak. In high temperature environments (blast furnaces, rolling mills, foundries, mining) this will lead to extreme fire risk. For these fields of application the so-called fire-resistant hydraulic fluids are available for hydraulic power transmission and control. They are defined in extensive standards: VDMA 24 317, 24 320, ISO 6743-4, DIN EN ISO 12922 as well as according to the "requirements and testing of fire-resistant fluids for hydraulic power transmission and control", Commission of the European Communities, Luxembourg Report (Advisory Committee on Safety, Hygiene and Health Commission for the Mining and Other Extractive Industries).Classification of fire-resistant hydraulic fluids:
? HFAE: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type A: HFAE - oil
in water emulsions.
? HFAS: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type A: HFAS - aqueous solutions.
? HFB: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type A: HFB - water in oil emulsions.
? HFC: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type C: aqueous polymer solution (water glycol).
? HFD: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type D: fluids free of water
? HFDR: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type D: fluids free of water, subgroup R - phosphoric acid ester based.
? HFDU: Classification letters according to DIN 51502 for fire resistant hydraulic fluids type D: fluids free of water, subgroup U - other base fluids (in most cases synthetic fatty acid ester).
Highly refined mineral oil or synthetic hydrocarbon based hydraulic fluids (pressure fluids) with good ageing resistance, low pour point, no foam formation and low viscosity. It is used in hydrodynamical and hydrostatical drive systems.
? HL DIN 51524 T1
Classification letters for hydraulic oils according to DIN 51524-1, containing antioxidants and anti
? HLP DIN 51524 T 2, VDMA 24 318
Classification letters for hydraulic oils according to DIN 51524-2, containing antioxidants, anti corrosion
additives and additives to reduce friction and wear.
? HVLP DIN 51524 T 3
Classification letters for hydraulic oils with high viscosity index (min. 140) according to DIN 51524-3,
containing antioxidants, anti corrosion additives and additives to reduce friction and wear.
Classification letters according to DIN 51502 for hydraulic oils with detergent properties.
Chemical compounds, only consisting of the chemical elements carbon and hydrogen: Paraffines (alkanes), isoparaffines (isoalkanes), naphthenes (cycloalkanes), olefines (alkenes), alkines, aromates (aromatic hydrocarbons).
Complete separation of the friction partners by a fluid lubricating film, e.g. in roller or plain bearings. In this state of fluid lubrication wear is minimized.
Elastomer, generated by polymerisation of acrylonitrile and butadiene and a following treatment with hydrogen.
Addition of hydrogen to chemical compounds, e.g. to aromatic hydrocarbons. Improves the quality of mineral oils. A further process is cracking, i.e. by the addition of hydrogen heavy oils are fractionized into lighter oils.
Type of hydrogenation in mineral oil refining. Components, such as aromatic and unsaturated hydrocarbons as well as sulfur and nitrogen compounds are reduced or removed. Depending on the reaction temperature and the hydrogen partial pressure three different processes are possible:
a) Hydrofinishing: mild hydrotreating following a solvent refining process to remove remaining undesired particles
b) Hydrofining: hydrogenating refining process to improve colour, odour, stability and demulsification properties
c) High pressure hydrogenation or hydrocracking: full removal of heterocyclic compounds of the distillate fraction, also predominant hydrogenation of aromatic hydrocarbons and cleavage of napthenic hydrocarbons into paraffinic hydrocarbons.
Lubricating oils with EP additives to be used in automotive axle drives with spiral-toothed and axial-offset bevel gears (hypoid gears).
Lubricants (lubricating oils and greases) according to DIN 51502 or DIN ISO 6743 for the application in industrial plants and machinery.
Property of substances and materials (e.g. lubricants) not to react chemically with other compounds.
Technique of chemical analysis, based on infrared light. Infrared spectroscopy (IR spectroscopy) is used to identify unknown substances by comparison with reference spectra, to determine the chemical structure of unknown substances and for the quantitative determination of identified substances in mixtures using standards of different concentrations. The IR spectrum is generated by recording the resonance frequencies of the oscillations of the atomic bonds of functional groups in a molecule. By these resonances energy is absorbed from the irradiated infrared light at characteristic wavelengths to a certain extent, depending on the number and type of functional groups
Lubricants with additives to prevent from non-ferrous metal corrosion.
Substances which delay or prevent chemical reactions. In lubricants they are used to protect against corrosion and ageing (oxidation).
Microbiological term, starting a cultivation of microorganisms (bacteria, fungi) by adding a small amount of microorganisms to the nutrient medium, e.g. nutrient solution or agar plate.
Microbiological term, small amount of microorganisms (bacteria, fungi) to be added to a nutrient medium (nutrient solution, agar plate etc.) to start a cultivation of microorganisms.
Binding agent in coatings, based on inorganic compounds.
Mainly low-viscous, in most cases mineral oil based fluids with high electrical resistance, typically applied in electrical transformers, capacitors, circuit breakers and with even lower viscosity in electrical discharge machining (EDM).
Property of dielectrics to prevent a high-voltage flashover between differently charged poles. Important for insulating oils and transformer oils.
Interface-active substances are e.g. tensides, emulsifiers, demulsifiers, wetting agents, defoamers, etc. which accumulate at the interface between two phases (e.g. oil and water) and thus influence (mostly reduce) the surface tension. Interface-active substances are mainly organic compounds.
The interfacial tension is the mechanical tension (force divided by unit of length) affecting the end of an interface. In case of positive interfacial tension the interfacial area is reduced. In this case the interfacial area behaves like a rubber membrane. In case of negative interfacial tension the interfacial area is enlarged. A negative interfacial tension is e.g. the reason that water will rise in a glass capillary. It is therefore also called specific interfacial energy (surface energy). Measurement unit: N/m. If one of the two phases involved is a gas phase, we talk about surface tension.
Characteristic number to differentiate between fats and oils from animal or vegetable sources as well as between synthetic esters or derivatives based on the quantity of unsaturated parts (carbon-carbon double bonds). Specifies the amount of iodine in gramme, which reacts with the unsaturated parts of the molecules in 100 g sample (addition to the double bonds). A low iodine number is usually correlated with good ageing resistance.
(= Institute of Petroleum). British organisation which deals with the standardization of test methods for oil, gas and mineral oil products. Today parts of the "Energy Institute". The code IP is still used in the denomination of test methods.
(= International Organization for Standardization). International network for standardization, central office in Geneva, Switzerland. Also code designation for international standards (e.g. ISO 6743-4).
DIN ISO 3448 classifies fluid industrial lubricants (hydraulic oils, gear oils, slideway oils, spindle oils) into 20 viscosity grades. Basis is the kinematic viscosity in mm²/s at 40 °C. A tolerance range of +/- 10 % from the mid point is allowed.
Isoparaffines (also called isoalkanes) are branched, saturated hydrocarbons.
[Greek Keros = wax]. Kerosene is a fraction which is generated from the distillation of crude oil. These are mainly hydrocarbons with chain lenghts between C10 and C16. Typcial application is aviation fuel.
The viscosity characterizes the flow properties of a liquid or gas and is the reciprocal value of the fluidity. Due to this, high viscosity means low fluidity and low viscosity high fluidity. Viscosity is the internal friction of a fluid and depends on the molecular structure of the components of the fluid. The kinematic viscosity can be calculated from the dynamic viscosity by dividing by the specific gravity (density) of the fluid:
Kinematic viscosity v = n / p with v (ny), dynamic viscosity n (eta) and specific gravity p (rho).
In view of the above, the unit of kinematic viscosity is square meter per second: 1 Pa•s•m³/kg = 1 N•s•m³/(kg•m²) = 1 kg•m•s•m³/(kg•m²•s²) = 1 m²/s
In common practice the kinematic viscosity is usually measured at temperatures of 20 °C, 40 °C or 100 °C in capillary viscosimeters (see Ubbelohde viscosimeter) and given in square millimeter per second: 1 mm²/s = 10-6 m²/s = 1 cSt St = Stokes (out-of-date unit)
Guidelines of the Federal Environmental Office for the hygienic estimation of organic materials in contact with drinking water, e.g. for sanitary lubricants. KTW stands for "Kunststoffe und Trinkwasser" (plastics and drinking water).
Wool wax resp. purified wool fat, by-product from the production of sheep wool. Lanolin is used as anti-corrosion additive in lubricants, as ointment base as well as for greasing textile and leather material.
Non water miscible coolant for lapping (machining of geometrically non-defined cutting edge) and carrier medium for the lapping grit (analogue abrasive grit for grinding), viscosity range approx. 3 to 15 mm²/s at 40 °C.
Limited slip additives are used in gear oils for hypoid and automotive transmission gears as well as in slideway oils to prevent stick-slip.
Mixture of different, in the majority of cases organic acids, saponified with lithium hydroxide.
Lithium complex soaps are mixtures of different, in most cases organic acid, saponified with lithium hydroxide, which are used as thickener in lubricating greases. Lithium complex soap based lubricating greases excel in their higher drop point, good water resistance and wide service temperature range.
Organic acid (mostly fatty acid), saponified with lithium hydroxide.
Multipurpose lubricating greases with an organic acid (mostly fatty acid) saponified with lithium hydroxide as thickener. In general 12-hydroxistearic acid is used, thus lithium-12-hydroxistearate as thickener. Good water resistance, good additive response, good shear stability and wide service temperature range.
Organic acid (mostly fatty acid), saponified with lithium hydroxide and calcium hydroxide.
Ability of a lubricant to resist mechanical loads in a tribo-system in which no damage (wear, cold welding etc.) occurs.
Characterizes the properties of mineral oil products at low temperatures. Typical methods to measure the low temperature behaviour are the determination of the pour point, cloud point, cold filter plug point, floc point, point of crystallisation or solidification.
Lubricants are substances or preparations designated to optimize relative motions between friction partners. This optimisation means the protection of shape and surface structure of at least one of the friction partners (prevention of wear and abrasion) and the reduction of the energy consumption during the relative motion (reduction of friction) respectively the adjustment of frictional forces to a required level. Apart from the reduction of friction and wear, lubricants have the function of heat removal (cooling), corrosion protection, material transport (chip transport in metal working), power transmission and control (hydraulic fluids), damping of noise and vibrations and of forming a barrier against ambient influences. Lubricants can be distinguished by their physical state of aggregation into gaseous, liquid, consistent (greases, pastes) and solid lubricants.
Homogenous lubricants comprised of a mineral oil and/or synthetic oil and a thickener, and which possibly contain additives and/or solid lubricants. Depending on the type of thickener we distinguish between metal soap greases (e.g. lithium, calcium, sodium soap greases), lubricating greases with organic thickeners (e.g. polyurea greases) and lubricating greases with inorganic thickener (e.g. silica gel or bentonite greases).
The "requirements and testing of fire resistant fluids for hydraulic power transmission and control" were defined by "the Advisory Committee on Safety, Hygiene and Health Protection at Work and the Safety and Health Commission for the Mining and Other Extractive Industries" in the Luxembourg report. Although the nomination of this advisory board had been cancelled on January, 1st, 2004, by EC council decision (2003/C 218/01), the 7th Luxembourg Report has not yet been withdrawn and is still applied for fire resistant hydraulic fluids in mining (see hydraulic fluids, fire resistant).
Non water miscible coolant (cutting oil) for easy metal working operations on automated lathes.
Manufacturers, importers or distributors of hazardous substances or preparations containing hazardous substances (if the content of hazardous substances exceeds certain threshold values) are obliged in the European Community and in many other countries to provide material safety data sheets (safety data sheets, MSDS) for the professional users. Driven by the market, material safety data sheets are available even for non-hazardous materials. The MSDS shows the classification and labelling of substances and preparations with respect to their hazardous properties to human beings and the environment. Furthermore, the safety data sheet gives advice for handling, storage, transport, required protection equipment, fire fighting measures, first aid measures and waste disposal. In Europe, the design and requirements for MSDS are regulated by the REACh regulation, GHS and their execution in Germany by the "Gefahrstoff-Verordnung" (GefStoffV, hazardous substances regulation).
By treatment with hydrogen highly refined mineral oil with extremely low content of aromatic hydrocarbons, suitable for pharmaceutical applications.
Ignoble metals and mainly their hydroxides react with organic acids, such as fatty acids, to form metal soaps. They are used as thickener in lubricating greases, as anti-corrosion or performance additives.
Collective name for non water miscible, rarely also for water miscible metal working fluids, e.g. cutting, rolling, drawing and drilling oils. According to current standards they are called coolant lubricants and are responsible for cooling, lubrication, chip transport and corrosion protection.
Property to prevent micropitting (grey staining) in gears.
Minimum requirements for operating fluids (US Military Specs).
All distillation and refining products extracted from crude oil, mostly mixtures of saturated and unsaturated hydrocarbons.
State of friction between boundary friction and fluid friction. Partial contact of the roughness peaks of the friction partners with a predominant separation by a fluid film as interfacial medium. In view of the above, the mixed friction range can be described as a coincidental presence of boundary friction and fluid friction.
Inorganic solid lubricant with layer structure, which is used in lubricating greases, oils, pastes and coatings to increase the load carrying capacity and to reduce friction and wear, especially at high mechanical loads.
Gear oils for various applications, e.g. in manual gears, auxiliary transmission gears and hypoid gears in vehicles, tractors and construction machinery. Comply with required MIL-specifications resp. API-classifications.
Multipurpose greases are lubricating greases which are suitable for a great variety of lubricant applications in a wide range of requirements, e.g. over a wide temperature and rotational speed range for plain and roller bearings.
Industrial lubricants with a specific additive system fulfilling the requirements for the use in several machine tool lubricant applications as well as for the metal working fluid in the machine tool. Suitable as gear oils, slideway oils, cutting oils, hydraulic oils in central lubrication systems.
Also called cyclopharaffines or cycloalkanes; they are saturated, cyclic hydrocarbons. Their generic formula is CnH2n.
Chemically unmodified oil from vegetable or animal sources, in most cases triglycerides (ester with glycerol as alcohol component).
Denomination of mineral oils, derived from solvent refining (SN = solvent neutral oils). The oils are commonly used as base oils in lubricants.
Amount (in mg) of potassium hydroxide (KOH), required for the neutralisation of the acidic or basic components in 1 g of oil sample. Changes in the neutralisation number of a lubricant during use can be correlated to oxidation processes (ageing) or variations in additive levels.
Newtonian liquids are fluids, whose viscosity does not depend on the applied shear rate and the state of deformation. Any shear stress leads to an immediate deformation and the viscosity does not change by applying shear forces. Whereas most fluids show Newtonian behaviour, some fluids are behaving non-Newtonian. In non-Newtonian fluids, e. g. blood, ketchup, starch-water mixtures and asphalt, the viscosity is influenced by the applied shear forces (see flow characteristics).
Elastomer, generated by polymerisation of acrylonitrile and butadiene.
Some nitrogen compounds, e. g. secondary amines, are able to react chemically with nitrite (NO2-) in an acidic environment (e. g. in the human stomach) forming carcinogenic nitrosamines. To prevent the formation of nitrosamines in water-mixed metal working fluids, the German regulation TRGS 611 (technical regulations for hazardous substances) restricts the use of listed secondary amines (max. 0.2 %) in metal working fluid concentrates in Germany and requires the weekly measurement of pH and nitrite (max. 20 mg/l) in water-mixed metal working fluids in use. In case of exceeding the nitrite threshold value, certain measures are mandatory.
Founded in the USA in 1933, association of lubricant producers and consumers. Target is the communication of tribological knowledge, such as new scientific knowledge, new developments, new production technologies, modification or innovation of standards, etc. Forums for technical discussions are e.g. the magazine "Spokesman" or the annual NLGI Meeting.
Lubricating greases are classified into the so-called NLGI-grades according to DIN 51818. To determine the NLGI-grade the cone penetration (worked penetration after 60 double strokes at 25 °C) is measured according to DIN ISO 2137. Since it is not possible to produce a lubricating grease always in the same consistency, each NLGI-grade has a penetration tolerance of 30 units (1 unit = 0,1 mm). The various grades follow each other at intervals of 15 units - see consistency.
Main application NLGI-grade Worked penetration in 1/10 mm
Semi-fluid gear greases 000 445 – 475
Soft 00 400 – 430
0 355 – 385
Roller bearing greases 1 310 – 340
2 265 – 295
3 220 – 250
Sealing and block greases 4 175 – 205
Hard 5 130 – 160
6 85 – 115
BECHEM classification of the noise damping properties of lubricants to prevent background noise from car interior components (low: against slight, medium: against medium, high: against heavy squeak and rattle noises).
All metals apart from iron and its alloys, sometimes colloquially used for yellow metals.
(NSF = National Sanitation Foundation), National Sanitation Foundation der USA, assigns approvals for food, pharmaceutical and sanitary applications. Lubricants for production machinery for food are subject to severe hygienic and toxicological regulations. The compliance of a lubricant with these requirements is reviewed and approved by the NSF resulting in the NSF-H1 certificate according to the FDA-regulations (Food and Drug Administration) or the NSF-H2 certificate.
H1: Lubricant approval of the NSF for incidental food contact. The lubricants can be used even if contact with food cannot be excluded.
H2: Lubricant approval of the NSF for applications with no food contact. The lubricants can be used in food processing provided contact with food is excluded.
(= Organisation for Economic Co-operation and Development); international institution with 34 member states, head office in Paris. The OECD deals with the worldwide standardisation of test methods for chemicals.
Today’s common test methods to prove ready biodegradability. Several procedures are available (A - F), depending on tested substance properties and detection method. See OECD.
Properties of lubricating greases to separate certain amounts of base oil during storage, at increased temperature or pressure. When low amounts of oil are separated, the grease properties will not be influenced. Oil separation can be determined according to various test methods, e.g. according to DIN 51817.
Traditional term of unsaturated hydrocarbons, i.e. hydrocarbons with one or more carbon-carbon double bonds. Modern term: alkenes (one double bond, CnH2n), alkadienes (two double bonds, CnH2n-2), alkatrienes (three double bonds, CnH2n-4).
Oleic acid, C18:1 fatty acid (mono-unsaturated non-branched fatty acid with 18 carbon atoms) with molecular formula C18H34O2 resp. C17H33COOH. Sources: Animal and vegetable fatty oils (triglycerides). Oleic acid is used to improve the rinsing and adhesive properties in metal working oils (non-water miscible metal working fluids) and for the production of metal soaps (metal salts of oleic acid), emulsifiers, synthetic esters or other derivates.";
(= Organisation of the Petroleum Exporting Countries). Head office in Vienna, Austria.
Binding agent in coatings, based on organic chemical compounds.
Macromolecules, generated by polymerisation of organic monomers.
Oxidation inhibitors, also called antioxidants, are chemical additives which delay or prevent (inhibit) undesired chemical reaction with oxygen or other oxidative processes. They are added to lubricants in order to delay the ageing process.
Method to determine the stability of lubricating greases against oxidative ageing. A defined amount of grease is stored in a stable stainless steel vessel (oxidation bomb) at elevated temperature (99 °C) and oxygen partial pressure (7,7 bar) for a certain time. The result is the decrease of oxygen partial pressure. The oxidation resistance of the lubricating grease depends on the pressure decrease (lower decrease of pressure - higher oxidation resistance). Determination according to DIN 51808.
Determination of the ash content of mineral oil based products in an open crucible. Residues from the refining process or contaminations from production, transport and storage or additives do not vaporize during incineration, but form inorganic oxides remaining in the crucible. The oxide ash content is determined according to DIN EN ISO 6245 to evaluate the purity of unused oils without additives or with ashless additives.
Historical term for the chemical group of saturated hydrocarbons without multiple bonds consisting only of the elements carbon (C) and hydrogen (H). They are also called alkanes. The basic structure consists of straight and branched chains. The first two types n-alkanes and iso or neo-alkanes form a homologous series with the general formula CnH2n+2. The cyclic molecules are also called cycloalkanes. Their general formula is CnH2n and are called naphthenes.
Liquid mixture of mainly paraffinic hydrocarbons (medical white oils), complying with the 10th issue of the German pharmacopeia. These low-viscous oils (25 - 80 mPa•s at 20 °C) are water-white, nearly odourless and consist of alkanes and cycloalkanes.
The composition of pastes is in general similar to greases. Pastes, however have a higher part of solid lubricants and thickeners. This guarantees reliable lubricating, separating and anti-corrosion properties even under extreme temperature and pressure conditions. With regard to lubricating greases the lubrication properties are of major importance.
Additives, which smooth the surface roughness of friction partners by plastic deformation.
Method for the determination of the consistency (stiffness, solidity) of greases and pastes. The cone penetration is measured according to ISO 2137 as the depth of penetration of a defined metal cone into a grease under defined conditions and given in units of 0.1 mm (see NLGI grades).
Apparatus for the determination of the penetration (cone penetration) or consistency of greases and pastes according ISO 2137 (see NLGI-grades).
Method to determine the flash point of mineral oils and other flammable liquids by using a closed cup. This method is applied in a range from 65 °C to 200 °C: DIN 51758, DIN EN ISO 1516.
Fully fluorinated polyethers: polymeric lubricating oils with outstanding temperature stability and plastic compatibility.
Peroxides are substances containing a peroxide anion O22- in inorganic peroxides or a peroxy group (–O–O–) in organic peroxides. Since peroxides result from oxidation and ageing of the mineral oil and lead to acid formation and polymerisation (resinification), their presence in lubricants is objectionable.
Paste-like mixture of oily and waxy paraffines (saturated, branched and straight hydrocarbons). Residue from crude oil refining which is used as ointment base in cosmetics or in anti-corrosion agents. See Vaseline.
Classification letters for polyglycol based lubricants according to DIN 51502, e. g. used as CLP PG.
Dimensionless number characterizing the acidic, neutral or basic (alkaline) reaction of an aqueous solution. The pH is defined as the negative logarithm (base 10) of the molar concentration (or more exact: activity) of Hydronium ions (H3O+, more modern: oxonium ion).
pH = 7 = neutral
pH > 7 = basic, alkaline
pH < 7 = acidic
Measuring the pH in water mixed metal working fluids provides valuable information about the condition (anti-corrosion properties) of the fluid and is required minimum once per week. In Germany the weekly measurement of pH and nitrite in metal working fluids is obligatory according to the regulations of TRGS 611.
Additives containing phosphorus as a component of the molecule.
Name of a failure mode on tooth flanks of gears or in roller bearings. Pitting is a form of surface ageing, generated by movements at high loads, especially with a high ratio of rolling friction, e. g. in gears or roller bearings. Small cracks are formed leading to spalling and leaving small pittings on the metal surface.
No longer used measuring unit of dynamic viscosity, abbreviation P. Calculation by means of measured kinematic viscosity by multiplication with the density of the fluid at a certain test temperature. Today pascal second acc. to SI-system is the common measurement: 1 P = 0,1 Pa•s. See viscosity.
Additives, forming a lubricating film by physisorption (adsorption without chemical reaction). Due to their molecular structure and the presence of heteroatoms (atoms other than carbon or hydrogen) like oxygen, sulfur, chlorine etc., some chemical compounds possess a permanent dipole moment and are absorbed to metal surfaces forming a lubricating film by physisorption better than unpolar compounds. In lubricants mainly fatty acids and fatty esters are used as polar additives improving the load carrying capacity in solid friction, boundary friction and mixed friction in the low temperature range. Furthermore polar additives are used to prevent stick-slip on slideways of machine tools.
Synthetic hydrocarbon, generated by polymerisation of alpha-olefines (C10 or C12). Synthetic isoparaffines with short main chains and long side chains, formed by hydrocracking of slack wax with subsequent polymerisation of the alpha-olefines.
Thermoplastic polymer, formed by polycondensation from amino carboxylic acids or lactames or dicarboxylic acids with diamines or amino carboxylic acids.
Thermoplastic polymer belonging to the group of polyesters.
Thermoplastic polymer, generated by polymerisation of ethylene (ethene).
Thermoplastic polymer belonging to the group of polyesters.
Polymer (polyether), generated by polymerisation of ethylene oxide and/or propylene oxide, in use as lubricant base oil or additive.
Build-up of molecule chains by chemical reaction of smaller molecules with each other.
Thermoplastic polymer, generated by polymerisation of formaldehyde.
Thermoplastic polymer, generated by polymerisation of propylene (propene).
Thermoplastic, fully fluorinated polymer used as solid lubricant and thickener for greases. The white coloured polymer is well known under the brand name Teflon® and shows excellent resistance against agressive chemicals and solvents as well as humidity and UV radiation. Due to the plain and slippery surface, a lot of substances are repelled from the material and PTFE particles are used in greases as thickener and solid lubricant, especially in plastic lubrication.
Organic polymer, generated by polyaddition from isocyanates and amines, in use as thickener for greases or as binder in adhesives and coatings. Belonging to the group of aminoplast resins, polyurea thickeners are designated by the presence of urea groups and can be described with the following generic formula: [-NH-R1-NH-(C=O)-NH-R²-NH-(C=O)-]n.
Organic polymer, generated by polyaddition aus isocyanates and alcoholes, in use as organic binder in coatings.
Thermoplastic, chlorine containing polymer, generated by polymerisation of vinyl chloride.
Additives which improve the flow properties of lubricating oils at low temperatures. They prevent the agglomeration of paraffin crystals arising from cooling.
Lowest temperature at which a liquid lubricant or base oil is still flowable under defined cooling and test conditions. Calculated by the point of solidification at which the oil is no longer flowable. Pour point = point of solidification +3 °C.
(= Parts per million). Measurement to indicate concentration. SI-measuring unit for ppm: mg/kg or referring to the volume µl/l resp. ml/m³.
Preserving agents are substances to prevent contamination of natural or industrial products or food by microorganisms, vermin or others. In water mixed coolants (e.g. oil-in-water emulsions) preserving agents (bactericides, fungicides, biostatical agents) are used to prevent contamination by fungi, yeast or bacteria which may lead to corrosion, filter clogging, phase separation, unpleasant odour, skin irritations, etc. Regular control of the germ number in water mixed fluids is essential.
Partly fluorinated elastomer, copolymer from propylene (propene) and tetrafluoro ethylene (tetrafluoro ethene).
Measuring vessel with a calibrated volume for the determination of specific gravity (density) according DIN 51757.
Oil for heat treatment of steels to adjust defined hardness (see tempering oil, burnishing oil). Depending on service temperature and requirements tempering oils (bath temperature up to approx. 320 °C) are used, martempering oils (bath temperature from 100 °C to 230 °C), high-performance quenching oils (addition of hydrocarbon resins to reduce the vapour phase), bright hardening oils (for bright metal surfaces), which can be water soluble or emulsifiable by adding emulsifiers (see bright hardening oils).
Oils for heat treatment of steels to adjust defined hardness (hardening, tempering). Depending on the service temperature and requirements tempering oils (bath temperature up to approx. 320 °C), martempering oils (bath temperature from 100 °C to 230 °C), high-performance quenching oils (addition of hydrocarbon resins to reduce the film boiling phase), bright hardening oils (for bright metal surfaces) are used which, by adding emulsifiers, can be washed of or emulsified (see tempering, quenching, bright hardening oils).
Short name for "RAL Institut für Gütesicherung und Kennzeichnung e. V." (German institute for quality assurance and certification) located in St. Augustin. The RAL is the office for the submission of the environmental label, e.g. RAL-UZ 79 for readily biodegradable hydraulic fluids.
(= Registration, Evaluation, Authorisation and Restriction of Chemicals). REACh is the present European legislation for chemicals with the goal of examining all chemical substances which are produced in quantities of more than 1 ton per year, with respect to their hazardous potential to human beings and the environment. REACh is based on the principle of individual responsibility of the industry and follows the motto \"no data - no market\"". Within the European Community chemicals can only be marketed, if after registration and presentation of a set of chemical, physical, environmental and toxicological data the substances are authorized by the responsibly authorities (ECHA: European Chemicals Agency). Depending on the produced volume of the substances, different volumes of data are required for evaluation and authorization. Each manufacturer or importer of chemical substances is obliged to register the substances and to pass the REACh process to obtain his own registry number for the substance. The REACh regulation came into force on June, 1st, 2007."
Measuring unit (especially in the UK) for viscosity, measured with the Redwood viscosimeter.
Crude oil processing plants to manufacture different mineral oil products via various steps (cleaning, distillation, hydrogenation, cracking, mixing, inclusion of additives).
Also called refractive number. Indicates the change in direction of propagation of light at the transition between two non-absorbing media of different optical density. Suitable to identify substances, e.g. mineral and other oils.
Optical device to determine the light refracting properties of substances and preparations. As hand refractometer it is often used to determine the concentration of water mixed metal working fluids (emulsions and solutions). The factors to calculate the actual concentration given by the manufacturer have to be observed - see refractive index.
Low-viscous mineral oil raffinates with good low-temperature properties (low pour point); no chemical reaction with the refrigerant is allowed.
Mineral oil without additives for lubricant application with minor requirements.
Oils which are designed to support demoulding in the various casting, moulding and ceramic firing processes (removal of the manufactured piece from the mould).
Raw materials which are generated from agriculture and forestry but are not intended for food or animal feed production. They are used for power generation and the production of fuels and lubricants or in the manufacturing industry. To obtain the EU-eco label (Euro-Marguerite) the use of a minimum quantity of renewable raw materials is mandatory - see Eco Label.
[Greek]. Science, dealing with the flow and deformation properties of substances and materials. The flow characteristics and the deformation properties depend on the molecular structure of the substances and the interactions between the molecules. For Newtonian fluids like water the flow characteristics can be described via a linear time-independent correlation according to Newton’s law of viscosity. In view of the above, the viscosity of Newtonian fluids does not depend on the applied shear forces. For non-Newtonian fluids the viscosity changes depending on the applied shear forces and on the time of application of the shear force. If the viscosity decreases with increasing shear force, the effect is called shear thinning (structural viscosity). If the viscosity increases with increasing shear force, the phenomenon is called shear thickening (dilatancy). In both cases, the viscosity immediately returns to its original value after removing the shear force. If the viscosity increases at a constant shear force, the effect is called rheopexy. The opposite behaviour of decreasing viscosity at a constant shear force is called thixotropy. Rheopexy and thixotropy are time-depending effects. Due to this the viscosity does not return immediately to its original value after removing the shear force, but after a certain time of relaxation.
[Greek]. Rheopexy is a property shown by some non-Newtonian fluids and describes the effect of increasing viscosity at a constant shear force. The opposite behaviour of decreasing viscosity at a constant shear force is called thixotropy. Rheopexy and thixotropy are time-depending effects. In view of the above, the viscosity does not return immediately to its original value after removing the shear force, but after a certain time of relaxation. An example for rheopexy is a plaster (gypsum)-water mixture with approx. 40 % plaster.
Production of a rippling structure caused by stick-slip.
Non water miscible metal working oils (forming oils) used for lubrication and cooling of the rollers for cold rolling of steel and aluminium sheets.
Apparatus for the determination of the dynamic viscosity, which is available in different configurations and variations. Common principle of all variations is the use of rotating test pieces (cylinder, cone, disk).
The corrosion product rust originates from the chemical reaction (oxidation) of iron or steel with oxygen in the presence of water and consists of water containing ferrous oxides. Contrary to oxide layers of other metals like aluminium, chromium or zinc the porous layer of rust does not protect against further decomposition.
Classification of automotive lubricants into viscosity grades, determined by the American Society of Automotive Engineers.
Method to determine anti-corrosion properties of lubricants (e.g. lubricating greases or anti-friction coatings) on metal parts under salt water atmosphere in a closed chamber at 35 °C. Test results are the elapsed time until first visible signs of corrosion occur is indicated. DIN EN ISO 9227 (formerly DIN 50021).
Salting will appear when in water mixed metal working fluids water, which has evaporated caused by the heat generated during the metal working process, is permanently topped up with water of a high salinity level (tap water, well water). High salinity levels lead to corroded machines and work pieces. Salting can be avoided by using fully desalinated top-up water.
The saponification number indicates the amount of potassium hydroxide which is required to neuralize all the acids and to saponify all the esters in 1 g oil sample according to DIN 51 559. This parameter is often used to characterize ester oils.
Scuffing marks arise during a relative motion of friction partners and the surface temperature generated by general heat exceeds the melting point of the material. This leads to welding of the surfaces, the metal contacts are interrupted, but visible surface defects remain as scuffing marks.
is important for lubricants in view of the complex influences. Incompatibilities between lubricants and sealing materials can lead to swelling and softening or shrinking and hardening of the seals in the lubricant circulation. This may result in functional constraints of mobile construction parts or leakages. There are, however, various reasons for leakages, e.g. constructional defects, unadjusted materials or material changes by ageing, change in temperature, etc. Each change in an adjusted system can lead to leakages. See swelling behaviour.
[German] (=Stahl-Eisen-Betriebsblatt). Technical guidelines of the German Steel Institute (VDEh).
Denomination for mineral oils extracted from waste oil recycling which can then be used as base oils in lubricant production. By modern recycling processes properties can be similar to those of primary raffinates.
Low-viscous technical white oils in a viscosity range from 7 to 12 mm²/s at 40 °C.
The shear rate (velocity gradient) describes the sterical change of flow velocity in fluids. Due to internal friction forces in fluids, different flow velocities occur, which decrease with increasing distance from the point of application of the shear force. In rheology the shear rate is an indication for mechanical stress in fluids and is used to define viscosity.
Oil soluble polymers (viscosity index improvers) are often added to improve the viscosity-temperature-properties or the pour point of oils. High loads during application often result in high shear forces which will lead to a destruction of the long-chain polymer molecules. Shear stability is the desired property of the polymer additives to withstand this phenomenon as long as possible. Test method e.g. four-ball tester acc. to DIN 51350-6.
Classification letters for silicone oil based lubricants according DIN 51502, e. g. used as CLP SI.
International system of scientific and technical basic units such as meter, kilogramme, second or Kelvin (French: Système International d'Unités).
Greases with silicone oils as base oils. Based on the good temperature and ageing resistance and the high viscosity index silicone greases are especially suitable for high temperature applications. Silicone greases are complatible with elastomers and plastic materials (except silicone rubber). The tribological properties (reduction of friction and wear protection) are inferior to most other lubricating grease types.
Silicones (polyorganosiloxanes) is the collective name for synthetic polymers with silicon atoms bonded to oxygen atoms. There are straight-chain and cyclic as well as cross-linked molecular structures. The two other free valence electrons of the silicon are used to bind hydrocarbon groups (methyl or phenyl groups), whereby silicones belong to the silicon organic compounds. Depending on the chain length of the molecules silicones are liquid (silicone oils) or even solid (silicone rubber, silicone resins). Liquid types are often used as lubricant base oils. Based on the good temperature and ageing resistance and the high viscosity index silicone oils are especially suitable for high temperature applications. Silicone oils are compatible with elastomers and plastic materials (except silicone rubber). The tribological properties (reduction of friction and wear protection) are inferior to most other base oil types.
Slack wax is the term for the paste-like, oil containing paraffines arising from the dewaxing of mineral oil in the refining process. This production step is followed by oil removal and refining.
Lubricating greases consist of a base oil and a thickener and possibly additives. Often metal soaps are used as thickeners, such as aluminium, calcium, lithium or sodium soap, as well as inorganic thickeners such as bentonite and organic thickeners, e.g. polyurea and PTFE. By special processes in grease production the thickener forms a sponge-type frame structure which absorbs the base oil. Under pressure the base oil is released and initiates lubrication.
Greases using sodium soaps, i.e. mixtures of different, in most cases organic acids, saponified with sodium hydroxide as thickener. They offer good lubricating and adhesive properties, low oil separation, they are suitable for high-speed bearings, however they have a low water resistance.
Organic acid (mostly fatty acid), saponified with sodium hydroxide.
Greases using sodium soaps, i.e. organic, in most cases fatty acid saponified with sodium hydroxide as thickener. They offer good emulsifying properties; they absorb moisture or prevent the migration of humidity into the tribologic contact. Sodium soap greases are used as long-fibred semi-fluid gear greases.
Solid substances, which reduce friction by their chemical structure or by surface reaction. Based on an excellent separation effect even at extremely low relative velocities and high loads, solid lubricants are primarily used in lubricants applied in the mixed friction and boundary friction range. Examples for solid lubricants are graphite, molybdenum disulfide, various plastic materials (e.g. PTFE), heavy metal sulfides, etc. Typical application are heavy-duty greases, anti-friction coatings, massive forming lubricants and lubricating oils with emergency running properties.
Temperature at which an oil cooled down under defined conditions becomes solid. Test method is DIN ISO 3016. Normally indicated as pour point (= solidification point + 3 °C).
A solubilizer is the chemical and pharmaceutical name for a substance which improves the solubility of hardly soluble substances in a solvent or preparation.
Colloquial, unexact denomination for emulsifiable coolants. The correct meaning is emulsifiable, mineral oil containing water miscible concentrates to produce emulsions for metal working processes.
In case of hardened metal surfaces (by heat treatment) the brittle upper surface layer can break after multiple load changes under deformation of the ductile core which leads to large area material fractures (spalling).
Spark erosion oils are applied in metal working to cool the workpieces, or as dielectric fluid and for the removal of abrasive particles. In most cases hydrocarbon fractions with a low content of aromatic hydrocarbons and a relatively high flash point at low viscosity are used.
Spectroscopy (spectrometry) is the collective name for a group of physico-chemical methods analysing the interaction of matter and electromagnetic radiation. These methods are mainly distinguished according to the wavelength range of the irradiated radiation like infrared light (IR spectroscopy), ultraviolet and visible light (UV/VIS spectroscopy), X rays (XRF spectroscopy) or according to the measured effect, e. g. absorption, emission and fluorescence. A big advantage of spectroscopical methods is the non-destructive testing of samples.
The speed factor is the product from mean bearing diameter and revolutions per minute of the bearing at standard operating conditions. The speed factor indicates the revolution of a bearing up to which a lubricating grease is suitable. Up to now there is no standardized process to determine the speed factors of lubricants. There is a direct connection between the base oil viscosity and the speed factor. For roller bearings with higher speed factors base oil with a lower viscosity are used. The calculation is as follows:
dk = dm • nD whereby dm = (da + di)/2
dk = speed factor (non dimensional value)
dm = mean bearing diameter in mm
da = external bearing diameter in mm
di = internal bearing diameter in mm
nD = revolution speed in U/min
Low-viscous lubricating oils (approx. 2 - 20 mm²/s at 40 °C) to lubricate spindles e.g. in textile machines or drive screws in machine tools.
Lubricating greases which are produced by saponification of vegetable and animal oils with calcium hydroxide and thus base on calcium stearate. In earlier times they were used for the lubrication of low-duty plain bearings or surfaces at temperatures up to approx. 60 °C and for sealing purposes. They are named after the producer Stauffer Chemicals.
Undesirable, inconsistent sliding motion with continuous stop and go. Stick-slip occurs at low speeds and high loads due to insufficient lubricating film formation. The reason for stick-slip is the periodical breakdwon of the separating lubricating film in a linear movement of a loaded body on a surface (e.g. slideway of machine tools) so that sliding friction will turn into static friction. Special additives (anti stick-slip additives) with high surface affinity can prevent stick-slip.
Elastomer, generated by polymerisation of Styrene with butadiene.
Determination of the ash content of organic substances in an open crucible under addition of sulfuric acid. The remaining residues consist of inorganic sulfates formed from inorganic contaminations and are called sulfate ash, which usually is given in per cent.
Additives containing sulfur as a component of the molecule, in use as EP or AW additives.
Frequently used term for surface-active substances which belong to the group of interface-active substances such as tensides, emulsifiers, demulsifiers, wetting agents, defoamers, etc. These substances accumulate at the interface between two phases, e.g. oil and water, and reduce the surface tension. In most cases surface-active substances are organic compounds.
Multi-phase mixture of a liquid with dispersed solid particles. Subgroup of the dispersions.
Describes the behaviour of elastomers, rubber and other plastic materials towards liquids and gaseous media; it is measured by the alteration of properties such as weight, volume, dimensions, hardness, tensile strength and break elongation. DIN ISO 1817, ISO 37, DIN 53505.
Lubricants, which are not based on mineral oil or native oils (native ester), but are based on chemically modified base oils (polyalphaolefines, polyglycoles, synthetic ester, alkylated aromatic hydrocarbons, polyphenylether, perfluoropolyether, silicone oils, phosphoric acid ester etc.). In comparison to mineral oil based lubricants, synthetic lubricants fulfill higher requirements depending on their particular properties, e. g. with respect to fire resistant properties, high temperature properties, low temperature behaviour, resistance against radiation, evaporation loss, oxidation resistance, extreme pressure properties, viscosity temperature behaviour etc.
Polymeric compounds, mostly hydrocarbons with a high molecular weight, or high-viscous, strongly polar substances which improve the adhesive properties of oil films on metal surfaces by structural viscosity and viscosity increase.
The total acid number (TAN) represents the amount of acidic substances in 1 g of oil sample given by the amount of potassium hydroxide (KOH, in milligramme) required to neutralize the acids. The determination is carried out by titration with ethanolic potassium hydroxide solution.
Non water miscible cooling oils with a high additive conent for forming or cutting of threads in metal parts.
The total base number (TBN) represents the amount of basic substances in 1 g of oil sample. The result of the titration is given by the equivalent amount of potassium hydroxide (KOH, in milligramme). Via TBN, the capability of a lubricant to neutralize acidic ageing products can be determined.
Oils for heat treatment of steels. They are used for "quenching" and "tempering" of hardened steel and thus release material tensions. See quenching oils, bright hardening oils.
At a specific temperature oils start to decompose even in the absence of oxygen. Thermal stability is the resistance against the destruction of the molecule structure.
Polymer with elastomeric properties at room temperature, capable of plastic deformation at elevated temperature.
Thermosoftening polymers which are reversibly deformable in a certain temperature range.
Thermosetting polymers which are not deformable after curing.
Additive to generate and adjust the consistency of greases and pastes. Lubricating greases consist of a base oil, a thickener and possibly additives. In most cases metal soaps, e.g. aluminium, calcium, lithium or sodium soaps are used as thickener, as well as inorganic thickeners such as bentonite and organic thickeners, e.g. polyurea and PTFE. In a lubricating grease, thickeners function like a sponge by absorbing the base oil until it is released under pressure allowing it to lubricate friction partners.
[Greek]. Thixotropy is a property shown by some non-Newtonian fluids and describes the effect of decreasing viscosity at a constant shear force. The opposite behaviour of decreasing viscosity at a constant shear force is called rheopexy. Thixotropy and rheopexy are time-depending effects. Due to this the viscosity does not return immediately to its original value after removing the shear force, but after a certain time of relaxation. Example for thixotropy are ketchup and water-sand mixtures.
Lubricant test equipment for wear tests of EP lubricants according to ASTM D-2509 and DIN 51434 (withdrawn). Load carrying capability and anti-wear properties can be measured by using a test piece with a quadrangular cross section, which is pressed by a lever arm with weight plates against a rotating shaft (800 rpm) with an outer bearing ring as the counter part. Result of the test is the OK load, which is the maximum load (lbs) with a wear loss less than 5 mg at the test piece in a defined test period (DIN 51434, ASTM D-2509).
Methods of chemical analysis with a large variety of applications, e. g. the quantitative determination of acids, bases, oxidising and reducing agents, water hardness, complexing (chelating) agents etc. In a tritation a standard solution (titrant solution) with a suitable reacting agent of known concentration is added stepwise to a sample solution of a known substance of unknown concentration up to the end point of the chemical reaction. From the tritant consumption, the concentration of the substance in the sample solution can be calculated stoichiometrically. The end point of the chemical reaction can be detected by colour change of indicator dyes, potentiometrically, amperometrically etc.
Mainly mineral oil based oils for cooling and insulation in transformers. Viscosity in general in a range from approx. 8 to 25 mm²/s at 40 °C.
The translatory oscillation tester (short term "SRV" from [German] Schwing-Reib-Verschleiß Tribometer) is a tribometer for testing friction and wear in linear oscillating motions between lubricated friction partners according to DIN 51834 (1-4). The upper friction partner (ball, cylinder, ring) oscillates in a translatory motion under a defined load on the surface of the lower friction partner (plate). Adjustable parameters are load [N], frequency [Hz], amplitude [mm], temperature [°C], duration [min] and the contact area by choice of the upper friction partner. Result of a test run is the course of the coefficient of friction. A large variety of auxiliary parts is available enabling rotational measurements or evaluation of wear etc.
[German] ("Technische Regeln für Gefahrstoffe" = Technical Rules for Hazardous Substances), additional German regulations to the "Gefahrstoffverordung" (= hazardous substances reugulation, see material safety data sheet). The TRGS determine the requirements for distributing and handling hazardous substances in Germany with respect to hygiene, occupational safety and health. Most important for the use of water-mixed metal working fluids is the TRGS 611 (Restriction of the use of water miscible and water-mixed metal working fluids, in which N-nitrosamines can be formed during application) containing rules and measures to prevent nitrosamine formation in metal working fluids.
Corrosion phenomenon (fretting corrosion), which occurs in tribo-systems with oscillating loads. Fretting corrosion can often be found at screw connections, linear guidings, bearing seats and spindles. The oscillating movements will destroy the lubricating film, which results in direct metallic contact between the asperities of the friction partners. As a consequence, wear occurs. Contact of the asperities results in cold welding, abrasive material wear, crack formation and tribo-chemical reactions of the formed metal particles with oxygen (oxidation, corrosion), which leads to strong wear of the material fit. Fretting corrosion can be prevented by a complete separation of the metal surface, e. g. by using solid lubricants.
Tribology is the science of surfaces interacting with each other under relative motion. It comprises the field of friction and wear as well as lubrication and interactions between solid, liquid and gaseous friction partners. Tribology and triboengineering are determined to reduce loss of energy and matter caused by friction and wear and to enable failure-free operation of technical systems by increasing efficiency and reliability.
Lubricating oils TD which, in view of their high ageing resistance, can be used for the lubrication of steam turbines and their components (gears, regulators, bearings, generators, compressors, pumps).
Guideline of the German Federal Environment Agency for hygiene assessment of organic materials in contact with drinking water.
With the Ubbelohde-viscositmeter the kinematic viscosity of fluids at different temperatures can be determined. The time which the fluid needs to flow through a capillary is measured. Finally the kinematic viscosity is calculated by multiplication of the required with the capillary constant. DIN 51562
Organic compounds with double or triple bonds between the carbon atoms. Hydrocarbons with double bonds are called alkenes, traditionally also called olefines. Unsaturated compounds cannot only be found in hydrocarbons but above all in all organic compounds which contain hydrocarbons, e.g. fatty acids and ester. In general unsaturated compounds show higher reactivity than saturated compounds; on the other hand they are not that resistant to ageing processes (oxidation).
Penetration at 25 °C of a grease sample which has been filled into the measuring cup under lowest possible shear stress, i.e. without previous treatment in the grease worker (DIN ISO 2137).
In daylight condition invisible dye, only becoming visible under UV light to check the lubricant application on parts and components.
Partial pressure of the gaseous fraction of a substance which, at a certain temperature, is in equilibrium with the liquid phase of the substance. Measuring unit for the evaporation loss of liquid fuels and lubricants.
Brand name for a pasty mixture of solid and liquid mineral oil components (paraffinic hydrocarbons) with a melting range between 38 °C and 58 °C.
1. (= Volatile Corrosion Inhibitor, Vapour Phase Corrosion Inhibitor). Volatile anti-corrosion additives, which evaporate into the gas phase and inhibit corrosion processes on metallic surfaces in contact to the gas phase. VCI substances are in most cases part of the packaging material (paper, cardboard, nonwoven material, plastic sheets, foils, foamed plastic) or are added separately as powder, spray or oil. VCI materials are used for the transport of corrosion-sensitive parts and machinery. After removal of the packaging, VCI materials evaporate completely and do not leave residues on the protected parts enabling a further processing of the parts without cleaning.
2. (= Verband der Chemischen Industrie e.V.). German Chemical Industry Association, located in Frankfurt/Main.
(= Verein Deutscher Ingenieure e.V.). Largest Association of German Engineers, founded 1856. Among others active in research funding and standardisation (VDI guidelines), head office Düsseldorf.
(= Verband Deutscher Maschinen- und Anlagenbau e.V.), German Engineering Federation. Based on the activities of various expert committees the VDMA is of outstanding importance in the field of lubrication, research, standardisation and information. Head office is Frankfurt/Main.
Classification of liquid lubricants and base oils based on their kinematic viscosity at 40 °C according to ISO 3448.
The viscosity characterizes the flow properties of a liquid or gas and is the reciprocal value of the fluidity. High viscosity means low fluidity and low viscosity high fluidity. Viscosity is the internal friction of a fluid and depends on the molecular structure of the components of the fluid. Depending on the molecular structure, varying attractive forces between the fluid molecules are occuring. High attractive forces result in high viscosity, low forces in low viscosity. In a simplified model, a fluid can be considered as a stack of molecular layers. In the state of flow, the molecular layers are sliding along each other. Attractive forces between the molecular layers induce resistance against the flow, resulting in a force required to keep the flow constant. The dynamic viscosity is defined as constant of proportionality in the correlation between required force and induced velocity gradient (shear rate).
Dynamic viscosity = shear stress / shear rate. The unit of dynamic viscosity is Pascal second (1 Pa • s = 1 N/m²). In common practice the dynamic viscosity is given in mPa•s (Milli pascal seconds): 1 Pa•s = 1000 mPa•s
Considering the gravitational force, the dynamic viscosity can be used to calculate the kinematic viscosity by dividing by the specific gravity (density)
(e. g. in case of free flow - driven by gravity - in a capillary; see Ubbelohde viscosimeter):
Kinematic viscosity n = h / r with n (Ny), dynamic viscosity h (eta) and specific gravity r (Rho).
Due to this, the unit of kinematic viscosity is square meter per second: 1 Pa•s•m³/kg = 1 N•s•m³/(kg•m²) = 1 kg•m•s•m³/(kg•m²•s²) = 1 m²/s
In common practice the kinematic viscosity is usually given in square millimeter per second: 1 mm²/s = 10-6 m²/s = 1 cSt St = Stokes (out-of-date unit)
Classification of lubricants according to their viscosity:
a) SAE-classification for automotive engine oils, determined by the American Society of Automotive Engineers. Example for a multigrade oil: 10W 30 (The first number indicates the viscosity at low temperatures - W like winter, the second number indicates the viscosity at 100 °C)
b) ISO VG-grades: DIN ISO 3448 divides fluid industrial lubricants (hydraulic oils, gear oils, slideway oils, spindle oils) into 20 viscosity grades (ISO VG-grades). Basis is the kinematic viscosity mm²/s at 40 °C. A tolerance range of +/-10 % from the mid point is allowed. The following grades are classified:
Dimensionless index to describe the viscosity-temperature-behaviour of liquid lubricants and base oils. Today the viscosity index is normally determined from the viscosities at 40 °C and 100 °C. A high viscosity index means a low change in viscosity with changing temperatures, whereby a low viscosity index means a larger change in viscosity with changing temperature. Naphthenic mineral oils have a viscosity index of approx. 30 - 70, paraffinic mineral oils of group I are situated within a viscosity index range from 90 - 100, mineral oils of group III at 120 - 140, polyalpha olefines (group IV) at 130 - 150, esters in part above 200, polyglycols up to almost 300, silicone oils up to approx. 400. The VI of mineral oils could be increased to almost 400 by adding so-called VI-improvers.
VI-improvers are additives to improve the viscosity-temperature-behaviour of oils, especially mineral oils, i.e. to reduce the degree of decrease or increase in viscosity in dependence of the temperature. At low temperatures the resulting oils excel in the favourable starting and friction characteristics of a low-viscous oil and at higher temperatures the good lubricating properties of a high-viscous oil. The addition of VI-improvers can increase the viscosity index of mineral oils from 30-150 to almost 400, depending on the type. Typical VI-improvers are polymers such as polymethacrylates (PMA) and olefin copolymers (OCP).
Describes the dependence of a lubricating oil on the pressure. With rising pressure the viscosity of compressible fluids increases which, at high pressures, can lead to considerable viscosity increases.
Collective name for volatile organic compounds (substances with a high tendency to evaporate). VOC’s evaporate at low temperatures or are already in the gaseous state at room temperature. According to the WHO definition, VOC and VVOC (very volatile organic compounds) show a boiling point of maximum 260 °C. In Germany VOC’s are classified according to their vapour pressure at 20 °C (above a minimum of 0.01 kPa). To prevent or reduce VOC emissions, the EC directive 1999/13/EC has been released, which is executed in Germany by the "VOC-Anlagen-Verordnung" (VAV = VOC equipment regulation).
(= Verband Schmierstoff-Industrie e.V.), Association of all important German lubricant manufacturers (multinational oil companies as well as small and medium-sized companies), head office Hamburg. The more than 60 member companies represent more than 90 % of the German lubricant industry. The VSI coordinates standardisation in the field of lubricants, cares for the exchange and communication of technical information, organises training courses and workshops and represents the members' interests with the authorities and other associations.
Waste oils are used oils, which cannot be utilized in their designated application due to a loss of lubricating properties by ageing and contaminations. According to the local regulations, waste oils have to be collected and treated by licensed waste management companies. Depending on the degree of contamination, waste oils usually are disposed by combustion or recycled (see secondary raffinates).
Colloquial term for fire resistant hydraulic fluids type C: HFC
German concept for the assessment of chemicals and preparations with respect to their hazardous potential against water and organisms living in water. This assessment is determined in the VwVws ([German] "Verwaltungsvorschrift wassergefährdender Stoffe" = Administrative Regulation on the Classification of Substances hazardous to waters into Water Hazard Classes). Due to the physico-chemical properties and the toxicity, substances are distinguished into different water hazard classes (WGK = [German] "Wassergefährdungsklasse"). Preparations are distinguished following the "mixture rules" of the regulation. The following classes exist:
WGK Denomination Examples
NWG non-hazardous to water native ester oils, certain synthetic esters
WGK 1 slightly hazardous to water some acids and bases, ethanol, methanol, most of the mineral oils
WGK 2 hazardous to water light heating oil, diesel fuel
WGK 3 severely hazardous to water benzine, waste oil, halogenated solvents, chromates, cyanides
Water miscible lubricants which are used for cooling and lubrication during cutting operations and partially in forming operations of in most cases metal materials. Many traditional names: drilling oils, grinding water, fully synthetic oils, metal working fluids, etc. The systematic and modernised denomination or classification of all coolant lubricants into two main groups follows DIN 51502 and DIN 51385:
1. Non water miscible coolants:
Are applied undiluted (grinding oil, deep drilling oil, machining oil, cutting oil, etc.)
2. Water miscible coolants (water mixed metal working fluids):
Are applied diluted with water.
a) Emulsifiable coolants (in application: coolant emulsion): Contain water insoluble components (in most cases as base oil).
b) Water soluble coolants (in application: coolant solution): Contain only water soluble components.
Relatively stiff lubricating greases (NLGI 3 or 4) with excellent water and temperature stability, e.g. suitable for heating and dehydrating plants.
Behaviour of lubricating greases in the presence of water. The behaviour towards distilled water is analysed under static test conditions (part 1) at 40 °C or 90 °C or dynamic conditions (part 2) at 40 or 80 °C. In case of static analysis the appearance and adhesion of the grease on a glass strip is checked visually; in case of dynamic analysis the amount of grease dragged out of the ball bearing by means water spray is measured gravimetrically. DIN 51807 T1 and T2.
Property to spread a liquid properly on a surface.
Wetting agents belong to the interface-active substances like tensides, emulsifiers, demulsifiers, defoamers, etc. which accumulate at the interface between two phases (e.g. oil and water) and thus influence (in most cases reduce) the surface tension. Wetting agents are used to improve wetting of surfaces.
White oils are highly refined, colourless to yellowish mineral oils with an extremely low content of aromatic hydrocarbons, also called MOAH. White oils are available in two qualities, technical and medical white oils. Technical white oils are transparent to yellowish mineral oil fractions which are less refined than medical white oils. Medical white oils are of highest purity and contain only traces of MOAH (mineral oil aromatic hydrocarbons). They are always transparent and consist of saturated hydrocarbons, also called alkanes. There are linear (straight-chain), branched and cyclic alkanes, also named MOSH (mineral oil saturated hydrocarbons). Medical white oils are used wherever direct contact with human beings or food is possible or where extreme chemical purity is required. They have to meet the standards of the European Pharmacopoea or the US Pharmacopeia (for NSF H 3). There are low-viscous white oils, such as “Paraffinum perliquidum”, and the high-viscous white oils “Paraffinum subliquidum”.
Forming lubricants to draw wires (in most cases steel, copper, aluminium). Depending on metal, wire diameter and type of drawing machine solid drawing lubricants, e.g. drawing soaps, drawing greases, drawing oils, aqueous emulsions and solutions are used.
For the lubrication of wire ropes to reduce friction of the individual ropes and to protect and corrosive influences. Wire rope lubricants often contain graphite or molybdenum disulfide additives.
Method of determination of the cone penetration of greases and pastes after previous working of the sample in the grease worker according to ISO 2137. The consistency of greases is classified into NLGI grades according to DIN 51818, which is based on measuring the cone penetration after working, i. e. the worked penetration. For the standard determination, the grease is worked for 60 double strokes (ds) in the grease worker at 25 °C. Afterwards, the cone penetration is measured according to ISO 2137 as the depth of penetration of a defined metal cone into a grease under defined conditions and given in units of 0.1 mm. Greases are changing their consistency under mechanical stress. For greases, especially for bearing greases, a small change in consistency induced by mechanical stress is highly advantageous. This change can be characterized by comparison of worked and unworked penetration. Excessive hardening of the grease degrades the transport properties in central lubrication systems and excessive softening leads to leakages out of the bearing resulting in starved lubrication. For further testing of the mechanical stability of greases, a prolonged working process is carried out with 5000, 60000 or 100000 double strokes (prolonged worked stability), comparing the worked penetration result after 60 ds with the results after prolonged working.
(= Water Regulation Advisory Scheme). British approval of products in contact with drinking water.