Analyses

The exact proportion of oil in petrol is determined following extraction of the solvent (petrol), after which the oil fraction is weighed and converted to a concentration in %.
 

The acids in the oil are titrated by a base until completely neutral. This is called the equivalence point. The number of ml of base until the equivalence point is expressed as the number of mg of potassium hydroxide per gram of oil. The acid number is also called the AN (Acid Number), TAN (Total Acid Number) or the neutralisation number. This figure is a measure for all acids present in the oil, both mineral acids and organic acids. In a mineral oil without any additives, the acidity is very low, almost zero. Oils with more additives have a higher acidity. The increase of the acidity can indicate oxidation and acidification of the oil.

The acids in the oil are titrated by a base until completely neutral. This is called the equivalence point. The number of ml of base until the equivalence point is expressed as the number of mg of potassium hydroxide per gram of oil. The acid number is also called the AN (Acid Number), TAN (Total Acid Number) or the neutralisation number. This figure is a measure for all acids present in the oil, both mineral acids and organic acids. In a mineral oil without any additives, the acidity is very low, almost zero. Oils with more additives have a higher acidity. The increase of the acidity can indicate oxidation and acidification of the oil.

The sample is spread across the microcount Combi growth medium and incubated in the incubator at 37°C. After 24 hours the number of aerobic bacteria is read in quantity per ml. After 48 hours the proportion of moulds and yeasts is read from the second growth medium.

The air release capacity of an oil is the time required by an oil to release dispersed air in the oil to a residual proportion of 0.2 vol%. The air is blown into the oil under a certain pressure and for a certain time. Subsequently the density of the oil is measured until the volume stops changing. The time of the air release is expressed in minutes.

The anaerobic bacteria in a sample are measured by placing the sample in the bottom of a closed container with a growth medium and to incubate this for 48 hours at 37°C. The presence of anaerobic bacteria is expressed as: 0 (none), + (traces), ++ (moderate presence) and +++ (high presence).

A portion of oil is mixed with an equal amount of aniline. This is heated until the aniline and oil form a single phase when mixed. The mixture is then cooled to the moment when the aniline is again separated from the oil phase. This temperature is called the aniline point. The lower the aniline point, the more aromatic the product is and the greater the chance of damage to elastomers.

The ashes are measured by burning the organic components of an oil or lubricant sample at a high temperature, as a result of which only ash remains which consists of metal oxides and impurities. The metal oxides are sulphated in the presence of concentrated sulphuric acid.

The BN value (or TBN value) of an engine oil represents the reserve alkalinity of an engine oil, i.e. the capacity of the oil to be able to neutralise acids in the oil. These acids are mainly formed upon combustion. When the TBN drops below 50% of the initial value of the unused oil, it is recommended to change the oil. Measuring the TBN value of an engine oil is particularly relevant for gas engines, stationary engines, engines subject to high thermal loads and combustion engines burning fuels with a high sulphur content. In the case of gas engines the BN is measured but also the AN value, whereby it is recommended to change the oil when the AN value exceeds the BN value.

The breakdown voltage of an oil is measured by increasing the electric current between 2 electrodes placed at a set distance of each other in the oil. The breakdown voltage is measured and the average result of 6 measurements is shown. This test is mainly carried out on the insulation oils of transformers and gives an indication when the oil must be changed. The test is very sensitive to water pollution, hence it is important that the sample is captured in a representative manner.

The colour of the oil is compared with the standard colour scale, as set out under ASTM D 1500, which ranges from 0.0 to 8.0. In this scale 0.0 is colourless, 2 is yellow, 4 is red, 6 is burgundy and 8 is very dark brown.

The congealing point and and pour point of an oil are measured by cooling the oil in standardised circumstances. The congealing point is the lowest temperature whereby the oil is still liquid. This is checked in steps of 3°C. The pour point is always 3°C lower than the congealing point. The pour point and congealing point provide an indication regarding the lowest temperature at which the oil can still be used.

On a paper filter 2 grams of standardised iron filings are weighed. 2 ml of the fluid to be examined is poured onto this. After 24 hours the iron filings are rinsed under flowing water and the corrosion spots, which are a measure for the corrosion percentage of the fluid, are assessed and counted.

Standardised iron filings are placed on a polished metal plate, over which a certain amount of the fluid to be analysed is poured. After a certain period, e.g. 24 hours, the metal plate is rinsed and the corrosion spots, which are a measure for the corrosion percentage of the fluid, are assessed and counted.

A pre-polished copper strip is immersed in the fluid to be examined for a certain period and at a certain temperature. Afterwards the discolouration of the copper strip is compared with the ASTM D130 colour scale.

The oil is mixed at a certain constant speed in the presence of an equal amount of water and at a temperature set in relation to the viscosity of the oil. After 5 minutes the separation time of the water is measured and the result expressed in 3 figures: volume water, ml/volume oil, ml/volume emulsion, ml, followed by the time in minutes. The demulsibility of an oil deteriorates in proportion to the presence of polar components, such as oxidation products.

The density of the oil is expressed in kg/l. The density changes in relation to the temperature, increasing at a lower temperature. Checking the density of an oil provides information about the chemical changes in the oil and/or whether it has been mixed with other oils.

The oil is distilled to remove the diesel. This diesel is caught in a graduated receptacle and the amount in vol% is recorded.

The flash point of the oil is measured at a temperature set in advance. If at that temperature a flash point is measured, the dilution with fuel is given as > 4%.

The dispersion ability of an engine oil in use is measured using a CCD camera. Under standardised circumstances a stain is made with the engine oil. This stain is subsequently dried at 80°C and is then read by the camera. The stain is divided into small squares and the light absorption in each square is measured in proportion to the soot content. The sum of the squares with the highest soot content is divided by the total number of squares. The quotient is a measure for the dispersion ability of the engine oil.

The lubricant to be measured is warmed up in a special cup in a dedicated container. The temperature at which the lubricant starts to drip is the drip point of the lubricant. Knowing the drip point contributes to the identification of the lubricant.

The oil is heated to a certain temperature in a metal container. In the container a small rod is mounted between 2 small metal cubes. The rod twists at a constant speed and the pressure of the 2 cubes on the rod is increased. At each increase in pressure the increase of the load on the rod is recorded. This test is carried out up to a load of 4500 lbs or until the cubes are welded to the rod. Afterwards the metal parts are weighed and the friction coefficient and wear is calculated.

The oil to be measured is mixed with an aliquot of water and is filtered through a 0.8µm membrane filter under a pressure of 1 bar. The time it takes to filter 50 ml, 200 ml and 300 ml of oil is measured and on the basis of the measured times the filterability index is calculated. The filterability index of an oil gives an idea of the contamination of the oil and the costs of filtering the oil.

The flash point of an oil is the temperature at which the oil releases so many inflammable substances that the oil, in the presence of a flame and air, inflames and continues to burn. The COC flash point measures the fire point in an open cup.

The flash point of an oil is the temperature at which the oil releases so many inflammable substances that the oil, in the presence of a flame and air, inflames for a short while. The flash point COC measures the flash point in an open cup.

The flash point of an oil is the temperature at which the oil releases so many inflammable substances that the oil, in the presence of a flame and air, inflames for a short while. The PMCC flash point measures the flash point in a closed cup.

Air is blown at a certain pressure level into the oil to be measured for a period of 5 minutes at a certain temperature. The time required to break down the foam is measured and expressed in seconds. This test can take place at 1 sequence i.e. at 24°C or at 3 sequences: at 24°C, at 93°C and at 24°C.

By way of fractional distillation, substances with a different boiling point are separated from each other.

By means of gas chromatography, molecules are separated from each other according to size at a high temperature. With this method it is possible to determine the proportion of diesel or petrol in an engine oil.

By way of gas chromatography, the fuel content in the oil can be measured, but it is also possible to determine the antifreeze content.

Any antifreeze present in the oil is detected by a chemical reaction, in which monoethylene glycol is converted into an aldehyde with a colour change as a consequence. This test helps to detect possible infiltration of coolants into the oil.

The metal elements in the oil are measured through flame emission spectrophotometry. The oil is diluted with an organic solvent and then atomised with an inert gas into an aerosol. The aerosol is magnetically induced to form a plasma or torch. Due to the high temperature (9000°C) of the torch, the electrons in the outer layer of the metal atom absorb energy as a result of which they jump to an outer shell. This situation is unstable and the electrons fall back to their original shell while releasing energy in the shape of photons. These photons are measured per wave length, specific for each metal element. Through ICP spectrometry, only the metals dissolved or suspended in the oil are measured.

The metal elements in the oil are measured through flame emission spectrophotometry. The oil is diluted with an organic solvent and then atomised with an inert gas into an aerosol. The aerosol is magnetically induced to form a plasma or torch. Due to the high temperature (9000°C) of the torch, the electrons in the outer layer of the metal atom absorb energy as a result of which they jump to an outer shell. This situation is unstable and the electrons fall back to their original shell while releasing energy in the shape of photons. These photons are measured per wave length, specific for each metal element. Through ICP spectrometry, only the metals dissolved or suspended in the oil are measured.

The metal elements in the oil are measured through flame emission spectrophotometry. The oil is diluted with an organic solvent and then atomised with an inert gas into an aerosol. The aerosol is magnetically induced to form a plasma or torch. Due to the high temperature (9000°C) of the torch, the electrons in the outer layer of the metal atom absorb energy as a result of which they jump to an outer shell. This situation is unstable and the electrons fall back to their original shell while releasing energy in the shape of photons. These photons are measured per wave length, specific for each metal element. Through ICP spectrometry, only the metals dissolved or suspended in the oil are measured.

The oil sample is scanned in the infrared region between 4000 and 400 cm-1. During this process, the interatomic bonds of the oil absorb the infrared light at specific wave lengths and the infrared spectre becomes visible. With this technique, oils can be compared to each other and the amount of specific components in the oil can be assessed.

A certain amount of oil is mixed with heptane and filtered in relation to viscosity through a 0.8µ or 5µ filter. Following filtration, the filter membrane is dried and the total amount of insoluble components is weighed in mg per litre of oil. This total amount consists of oxidation products insoluble in heptane and of contamination foreign to oil. The amount of insoluble components gives an indication of the purity and degree of oxidation of the oil.

The filtered components obtained after the test 'insoluble components in heptane' are rinsed with toluene. The oxidation products of the oil are soluble in toluene. This is all filtered again and the difference between the weight of the components insoluble in heptane minus the content of components in insoluble toluene is the amount of oxidation products expressed in mg per litre of oil.

Kinematic viscosity is expressed in mm²/s (cSt) and is the time in seconds required for a certain amount of oil to flow, under the influence of gravity, through a calibrated viscosity measurement tube at a certain temperature. Kinematic viscosity is also the correlation between the absolute viscosity and density of the oil at a certain temperature. The viscosity of an oil varies with the temperature; the higher the temperature, the lower the viscosity and vice-versa. Generally the viscosity is measured at 40°C and 100°C (ISO-SAE standards).

Kinematic viscosity is expressed in mm²/s (cSt) and is the time in seconds required for a certain amount of oil to flow, under the influence of gravity, through a calibrated viscosity measurement tube at a certain temperature. Kinematic viscosity is also the correlation between the absolute viscosity and density of the oil at a certain temperature. The viscosity of an oil varies with the temperature; the higher the temperature, the lower the viscosity and vice-versa. Generally the viscosity is measured at 40°C and 100°C (ISO-SAE standards).

A certain amount of the oil sample is shaken and then filtered through a 0.8µ or 5.0µ filter. After drying the filter, the sediment on the filter is examined under a microscope with a magnification of 100x or 200x for the presence of contamination particles and wear particles. Differentiation is made of white metal, black metal, welding beads, silt, silica, polymers, fibres, plastics, resins, rust particles, bearing wear particles, etc. The number, size, texture and structure of the particles give an indication of the type and severity of the wear.

100ml of oil is filtered through a 0.8µm or 5.0µm filter membrane. Following filtration, the membrane is dried and weighed. The difference between the weight before and after filtration is expressed as the proportion of insoluble components in mg per litre of oil.

The insoluble particles in the oil are counted to size and number using a laser sensor. The purity class is expressed in accordance with ISO 4406, NAS 1638 and/or SAE 4059J. The purity class gives an indication with regard to the effectiveness of the filter system. It is important for the life span of the oil and the machine to obtain and maintain an oil which is as pure as possible.

The amount of polychlorobiphenyl is measured by way of the method EN 61619/1997 (IEC 61619:1997) - Calculation of 109 congeners.

A certain amount of lubricant is placed in a standard cup. Under particular conditions, a standardised conical object is dropped into the lubricant for a certain period. The penetration of the cone into the lubricant is measured and expressed in 0.1 mm. The extent of the penetration indicates the NLGI consistency number, ranging from 000 to 6. A liquid lubricant with a high penetration has a low NLGI number, while a hard lubricant has a high NLGI number.

The pH is equal to the negative logarithm (with base 10) of the concentration of hydrogen ions (H+) in an aqueous solution. The pH of a neutral aqueous solution at room temperature is approximately 7. Acid solutions have a pH below 7, basic solutions have a pH above 7. The pH of a lubricant oil is measured after it is dissolved in an alcohol and water-based solvent, and is an indication of the presence of corrosive acids in the oil.

The PQ index is a number indicating the amount of magnetisable particles in an oil. The greater the amount of magnetisable particles, the higher the PQ index. The proportion of the PQ index to the number of iron particles measured with ICP provides information on the type of wear, normal friction wear, abrasion, pitting, fatigue, adhesion, corrosion, etc.

Before the sample can be placed on ICP, GC or FTIR, it is first prepared by filtering or diluting it in a suitable organic solvent. In the case of a lubricant sample, Alpha MS will firstly select which solvent is most suited to dissolve the lubricant.

The reserve alkalinity of an antifreeze is measured by way of titration of the bases by an acid, hydrogen chloride, until all acids are neutralised. This is called the equivalence point. The number of ml of acid until the equivalence point is converted into the number of mg of potassium hydroxide per gram of oil.

The RPVOT test measures the oxidation stability of a lubricating oil and provides an indication as to how long the oil can remain in use. The oil is oxidised in a pressure vessel at a temperature of 150°C under pressure of pure oxygen and in the presence of 10% water and a copper spiral. The pressure in the vessel is continuously measured while the sample turns at a constant speed. When all antioxidants present in the oil have been used and no more oxygen can be bound a reduction in pressure occurs. The period up to the pressure reduction is measured in minutes. This period, compared to the oxidation period of unused oil, gives an indication as to how long the oil can remain in use.

The proportion of saponifiable products in the oil is a measure for the concentration of esters and free acids in the oil. The result is expressed in mg KOH/g of oil. This test gives an indication regarding the presence of (biological) esters in an oil.

The soot content is indicated as a percentage, with a precision of up to 0.1%, by way of FT-IR or light absorption measurement of an oil mark developed in a standardised manner. The result of the soot content test is assessed in relation to the period of use and in relation to the type, brand and series of engine. Too much soot can cause blockages of the oil pipes and, as a result, increased wear.

The used engine oil is heated and cooled. Following cooling, 21µl of oil is placed by way of a pipette onto a filter paper with a known pore size. The mark obtained in this way is placed in the oven at 80°C for 1 hour and then scanned by a CCD camera. The mark is divided in many small squares and the intensity in each square is measured, based on which the soot content and the dispersion ability is calculated.

The sulphur content of an oil can be determined in several ways: ICP, X-ray fluorescence, pressure vessel method, etc. Sulphur in an oil generally originates from the oil itself, but is sometimes also caused by the additives. Knowing the sulphur content contributes to identifying the oil.

The proportion of ash in an oil is determined by carbonisation at 775°C. The residue is treated with sulphuric acid, as a result of which the organometallic additives of the oil are broken down, after which the oil is heated further until only sulphated ash remains. The sulphate ash is expressed in percentage of weight. Lower sulphate ash values of an engine oil guarantee lower deposits of the metallo-organic additives in and around the combustion chamber and valves.

This test measures the dielectric dissipation factor of an insulating oil, TAN delta.

The viscosity index is an empirical number which reflects the change of viscosity in relation to the temperature and is measured based on the viscosity at 40°C and at 100°C. The higher the viscosity index, the lower the reduction of viscosity in relation to the temperature increase.

The oil is distilled to remove the water. This diesel is caught in a graduated receptacle and the amount in vol% is recorded.

A certain amount of oil, diluted in a solvent not containing water, is left to react with calcium carbide in the presence of a catalyst. During this reaction, hydrogen gas is released. The pressure of the released hydrogen gas is a measure for the amount of water in the oil, expressed with an accuracy of up to 0.01%.

By way of iodometric titration, the water in the oil is titrated away until the equivalence point, to an accuracy of 1ppm. Alpha MS has several types of equipment and methods to carry out the Karl Fischer method, as a result of which the water content of all fluids can be determined.

The water content of a water glycol is measured by way of the Karl Fischer potentiometric method after heating the sample in an oven. The result is expressed in %.

The hardness of the water is measured by way of titration with an acid in the presence of a colour indicator. This is a measure for the amount of calcium and magnesium salts in the water.