Interpretation of the characteristics of lubricating oil
Onboard tests
1. TBN
2. Water content
3. Viscosity
4. Alkalinity
5. Flash point
6. Spot test
7. Chloride/Sea water content
1. TBN
2. Water content
3. Viscosity
4. Alkalinity
5. Flash point
6. Spot test
7. Chloride/Sea water content
1. Spectro-Analysis(metal/additives contamination)
2. Flash point
3. Base number
4. Viscosity
5. Density
6. Insoluble content
7. Water content
8. Micro-Biological test.
2. Flash point
3. Base number
4. Viscosity
5. Density
6. Insoluble content
7. Water content
8. Micro-Biological test.
Onboard tests
1. TBN
Reagent T and N 10ml each are added in the 10ml sample oil and placed in the testing unit cup. The cup is properly sealed and well mixed, the resultant pressure rise is compared with a chart according to the oil used.
The alkalinity of lubricating oil is defined as the quantity of hydrochloric acid or perchloric acid required to neutralize one gram of oil, expressed in terms of the equivalent number of milligrams of potassium hydroxide (mg KOH/g). The BN is measured by titration with acid.
AN (Acid number) formerly called Total Acid Number (TAN) describes the amount of acidic components in the oil. It is measured by titration with a base such as Potassium Hydroxide (KOH). The acidity of a lubricant is measured by the amount of KOH required for neutralization and is expressed in mgKOH/g. The AN is relevant for lower BN oil and mainly in engines operated on gas. It is influenced by oil degradation.
The BN (formerly called TBN total base number) is a measure of the alkalinity reserve. It shows the potential of the lubricating oil to neutralize acids caused by combustion products condensing on the cylinder walls and elsewhere within the engine. For example sulphur in the fuel is converted to sulphur oxides during combustion - mainly SO2 along with a small proportion of SO3. Together with the water formed during the combustion process, the sulphur oxides condense on the cylinder walls as sulphuric acid, this acid is then neutralized by the alkalinity of the lubricant.
BN depletion is mainly influenced by the sulphur content of the fuel used, the oil consumption of the engine and the operating conditions of the engine.
The BN of new lube oil drops sharply for a short while and then decreases more slowly to an equilibrium value. Thereafter, this equilibrium will continue indefinitely, provided the Sulphur content of the fuel and lubricating oil consumption remain stable.
If the alkalinity of the lube oil has dropped too much, there is a serious risk of corrosive wear of the cylinder liners, piston rings and bearings (anti-friction layer) as the oil has not enough potential to neutralise the sulphuric acid produced by fuel combustion. This neutralisation results in the formation of either calcium or magnesium sulphates (depending on the additive contained in the lube oil) which inevitably become part of the insoluble carried by the lube oil when returning to the crankcase.
The BN of the drain oil is influenced by the fuel sulphur level, the cylinder oil BN and the cylinder oil feed rate. The higher the fuel sulphur level, the more sulphuric acid is formed during combustion. The acid formed condenses on the liner surface and the basicity (expressed as BN) provided by the
cylinder oil will neutralize the acid.
From this it follows that the lower the fuel sulphur level and/or the higher the cylinder oil BN and feed rate, the higher the drain oil BN. Optimisation of the demand for neutralisation and the demand for the appropriate fluid film forming capability is a constant challenge for the engineer as the sulphur content of the fuel varies for each bunker and for differing areas of operation. With a fixed BN for the cylinder oil neutralisation demand can be met by adjusting the feed rate, however the required oil film properties are proportional to engine operation, therefore the best solution will likely be a compromise of some sorts.
The BN of a fresh system oil is generally low (below 10 mg KOH/g) but the contamination by scavenge drain oil will lead to a BN increase. The system oil topping-up helps to balance this change and BN levels of 15-20 mg KOH/g are observed on average. High BN levels may result in water separation problems for which reason the manufacturers have a caution limit of BN 25, and recommend to replace a portion of the system oil at a BN level of 30.
The alkalinity of lubricating oil is defined as the quantity of hydrochloric acid or perchloric acid required to neutralize one gram of oil, expressed in terms of the equivalent number of milligrams of potassium hydroxide (mg KOH/g). The BN is measured by titration with acid.
AN (Acid number) formerly called Total Acid Number (TAN) describes the amount of acidic components in the oil. It is measured by titration with a base such as Potassium Hydroxide (KOH). The acidity of a lubricant is measured by the amount of KOH required for neutralization and is expressed in mgKOH/g. The AN is relevant for lower BN oil and mainly in engines operated on gas. It is influenced by oil degradation.
The BN (formerly called TBN total base number) is a measure of the alkalinity reserve. It shows the potential of the lubricating oil to neutralize acids caused by combustion products condensing on the cylinder walls and elsewhere within the engine. For example sulphur in the fuel is converted to sulphur oxides during combustion - mainly SO2 along with a small proportion of SO3. Together with the water formed during the combustion process, the sulphur oxides condense on the cylinder walls as sulphuric acid, this acid is then neutralized by the alkalinity of the lubricant.
BN depletion is mainly influenced by the sulphur content of the fuel used, the oil consumption of the engine and the operating conditions of the engine.
The BN of new lube oil drops sharply for a short while and then decreases more slowly to an equilibrium value. Thereafter, this equilibrium will continue indefinitely, provided the Sulphur content of the fuel and lubricating oil consumption remain stable.
If the alkalinity of the lube oil has dropped too much, there is a serious risk of corrosive wear of the cylinder liners, piston rings and bearings (anti-friction layer) as the oil has not enough potential to neutralise the sulphuric acid produced by fuel combustion. This neutralisation results in the formation of either calcium or magnesium sulphates (depending on the additive contained in the lube oil) which inevitably become part of the insoluble carried by the lube oil when returning to the crankcase.
The BN of the drain oil is influenced by the fuel sulphur level, the cylinder oil BN and the cylinder oil feed rate. The higher the fuel sulphur level, the more sulphuric acid is formed during combustion. The acid formed condenses on the liner surface and the basicity (expressed as BN) provided by the
cylinder oil will neutralize the acid.
From this it follows that the lower the fuel sulphur level and/or the higher the cylinder oil BN and feed rate, the higher the drain oil BN. Optimisation of the demand for neutralisation and the demand for the appropriate fluid film forming capability is a constant challenge for the engineer as the sulphur content of the fuel varies for each bunker and for differing areas of operation. With a fixed BN for the cylinder oil neutralisation demand can be met by adjusting the feed rate, however the required oil film properties are proportional to engine operation, therefore the best solution will likely be a compromise of some sorts.
The BN of a fresh system oil is generally low (below 10 mg KOH/g) but the contamination by scavenge drain oil will lead to a BN increase. The system oil topping-up helps to balance this change and BN levels of 15-20 mg KOH/g are observed on average. High BN levels may result in water separation problems for which reason the manufacturers have a caution limit of BN 25, and recommend to replace a portion of the system oil at a BN level of 30.
.
2. Water content
Water crackle test is done by heating 10 drops of oil in an aluminium foil container over a flame. A crackling sound confirms the presence of water in the oil.
The water content is qualitatively is ascertained by measuring the resultant pressure rise of a test mixture. 5ml sample oil and 15ml petroleum reagent A are mixed in the test unit cup. A standard amount in a sealed sachet of reagent B is added and the mixture sealed and shaken thoroughly. The chemical reaction takes place between water in the oil and the reagent calcium carbide to form acetylene gas which gives a resultant pressure. Reagent A is a paraffin or toluene and B is calcium carbide.
Water affects the viscosity and lubricity of the lubricating oil and if not removed may form an emulsion with it. It is, therefore, desirable to keep the water content as low as possible by centrifuging (if installed). If the water content exceeds 0.2% (v/v), appropriate operation of the centrifuge should be carefully checked and if necessary adjusted to ensure optimum lubricating oil / water separation. In addition root causes of water contamination should be investigated and solved as soon as possible.
Some lubricants can form water-in-oil emulsions preventing the water from being removed by centrifuge alone. Such emulsion, if circulated, will reduce the load carrying capacity of the lubricating oil in bearings and may lead to failures. In some cases it is possible to drive off and thus reduce the water content by higher temperature purification at ~95ºC, if this is not possible as a consequence, any emulsified lubricating oil should be replaced as soon as possible. Alkaline and most other additives are sensitive to water content. If lubricating oil is contaminated by water, additive depletion could take place, which means, among other effects, a drop of BN. With water, additives form insoluble sludges which are disposed in the centrifuge. Used lubricating oils exhibit greater intolerance compared to the same lubricating oil when new. Sea water is corrosive and potentially harmful. Whether corrosion will actually occur in the engine depends on a number of factors - for instance, how much salt is in the lubricating oil, how much water and strong acids are also present and whether the lubricating oil retains sufficient anti-corrosion performance capability.
The water content is qualitatively is ascertained by measuring the resultant pressure rise of a test mixture. 5ml sample oil and 15ml petroleum reagent A are mixed in the test unit cup. A standard amount in a sealed sachet of reagent B is added and the mixture sealed and shaken thoroughly. The chemical reaction takes place between water in the oil and the reagent calcium carbide to form acetylene gas which gives a resultant pressure. Reagent A is a paraffin or toluene and B is calcium carbide.
Water affects the viscosity and lubricity of the lubricating oil and if not removed may form an emulsion with it. It is, therefore, desirable to keep the water content as low as possible by centrifuging (if installed). If the water content exceeds 0.2% (v/v), appropriate operation of the centrifuge should be carefully checked and if necessary adjusted to ensure optimum lubricating oil / water separation. In addition root causes of water contamination should be investigated and solved as soon as possible.
Some lubricants can form water-in-oil emulsions preventing the water from being removed by centrifuge alone. Such emulsion, if circulated, will reduce the load carrying capacity of the lubricating oil in bearings and may lead to failures. In some cases it is possible to drive off and thus reduce the water content by higher temperature purification at ~95ºC, if this is not possible as a consequence, any emulsified lubricating oil should be replaced as soon as possible. Alkaline and most other additives are sensitive to water content. If lubricating oil is contaminated by water, additive depletion could take place, which means, among other effects, a drop of BN. With water, additives form insoluble sludges which are disposed in the centrifuge. Used lubricating oils exhibit greater intolerance compared to the same lubricating oil when new. Sea water is corrosive and potentially harmful. Whether corrosion will actually occur in the engine depends on a number of factors - for instance, how much salt is in the lubricating oil, how much water and strong acids are also present and whether the lubricating oil retains sufficient anti-corrosion performance capability.
3. Viscosity
It is measured by using a flow stick comparator method. The relative flow rate is measured between a new oil and used oil. 3ml new and 3ml used oil at the same temperature are placed in the flow stick reservoir respectively. The flow stick is tilted allowing both the oils to flow through separate channels. When the new oil has reached the reference mark, the position of the used oil is checked. Markings on the flow stick give the conditions of the oil.
Viscosity is the most important property of lubricating oils. It determines not only the internal friction, but also the load carrying capability and the oil film thickness between bearing surfaces. Viscosity influences the bearing temperature, the oil quantity transported to the piston under crown for cooling and to the cylinder liners/piston rings. It also affects the oil’s “spread-ability”.
Viscosity of the lubricant in use varies in service, mainly due to contamination with soot produced by combustion of fuel and lubricating components, contamination with the fuel, oxidation, thermal degradation and water content.
Reasons for viscosity increase:
Low lubricating oil level. This is of particular importance because of its impact on all other processes listed below. The lubricating oil volume should be kept at the level recommended by the engine manufacturer.
Oxidation. This is a process that is very dependent on temperature, contamination and the availability of oxygen. It is aggravated when the lubricant is contaminated with raw fuel (e.g. containing unstable olefinic components). Furthermore, the catalytic activity of wear metals, such as copper and iron, can accelerate oxidation.
Nitration. This occurs mainly due to high NOx content of blow-by gases. This is more relevant to gas engine lubricating oil than diesel engine lubricating oil.
Sulphation. Sulphation is inversely proportional to BN depletion and can be used to give an indication of the degree of degradation of the lubricant.
Contamination by residual fuel. This occurs if coagulation of asphaltenes from residual fuel takes place within the lubricating oil in use and it is the main reason for viscosity increase of engines operating on heavy fuel oil (HFO).
Insolubles. Significant increases of insolubles in used lubricating oil can result from poor combustion, faulty operation of purifiers, insufficient capacity of filters, and also ingress of sulphuric acid into the lubricating oil due to low cylinder liner temperature, poor mechanical condition of the engine, etc.
Soot. Increase of sooty insolubles in the lubricating oil in use can be caused by high lubricating oil consumption that can lead to increased soot production from burnt lubricant in the combustion chamber. Also low-load operation in the engines equipped with conventional (jerk pump) fuel injection equipment can increase soot content in lubricating oil, since the combustion process is not so optimal due to low fuel injection pressures. Further, also worn fuel injection nozzles can result in increased soot content in used lubricating oil.
Water. Contamination with water forming an emulsion will increase the lubricating oil viscosity. Admixture with another lubricant. Mixing with higher viscosity oil will cause an increase in the viscosity of the total oil charge.
Reasons for viscosity decrease:
Decrease in lubricant viscosity is potentially more harmful to the engine than an increase of viscosity. It will reduce lubricating oil film thickness with the risk of seizure, more particularly in bearings. The main cause of viscosity reduction is the dilution by light fuels, use of lower viscosity lubricating oil for topping up or by contamination with cleaning fluids.
Viscosity is the most important property of lubricating oils. It determines not only the internal friction, but also the load carrying capability and the oil film thickness between bearing surfaces. Viscosity influences the bearing temperature, the oil quantity transported to the piston under crown for cooling and to the cylinder liners/piston rings. It also affects the oil’s “spread-ability”.
Viscosity of the lubricant in use varies in service, mainly due to contamination with soot produced by combustion of fuel and lubricating components, contamination with the fuel, oxidation, thermal degradation and water content.
Reasons for viscosity increase:
Low lubricating oil level. This is of particular importance because of its impact on all other processes listed below. The lubricating oil volume should be kept at the level recommended by the engine manufacturer.
Oxidation. This is a process that is very dependent on temperature, contamination and the availability of oxygen. It is aggravated when the lubricant is contaminated with raw fuel (e.g. containing unstable olefinic components). Furthermore, the catalytic activity of wear metals, such as copper and iron, can accelerate oxidation.
Nitration. This occurs mainly due to high NOx content of blow-by gases. This is more relevant to gas engine lubricating oil than diesel engine lubricating oil.
Sulphation. Sulphation is inversely proportional to BN depletion and can be used to give an indication of the degree of degradation of the lubricant.
Contamination by residual fuel. This occurs if coagulation of asphaltenes from residual fuel takes place within the lubricating oil in use and it is the main reason for viscosity increase of engines operating on heavy fuel oil (HFO).
Insolubles. Significant increases of insolubles in used lubricating oil can result from poor combustion, faulty operation of purifiers, insufficient capacity of filters, and also ingress of sulphuric acid into the lubricating oil due to low cylinder liner temperature, poor mechanical condition of the engine, etc.
Soot. Increase of sooty insolubles in the lubricating oil in use can be caused by high lubricating oil consumption that can lead to increased soot production from burnt lubricant in the combustion chamber. Also low-load operation in the engines equipped with conventional (jerk pump) fuel injection equipment can increase soot content in lubricating oil, since the combustion process is not so optimal due to low fuel injection pressures. Further, also worn fuel injection nozzles can result in increased soot content in used lubricating oil.
Water. Contamination with water forming an emulsion will increase the lubricating oil viscosity. Admixture with another lubricant. Mixing with higher viscosity oil will cause an increase in the viscosity of the total oil charge.
Reasons for viscosity decrease:
Decrease in lubricant viscosity is potentially more harmful to the engine than an increase of viscosity. It will reduce lubricating oil film thickness with the risk of seizure, more particularly in bearings. The main cause of viscosity reduction is the dilution by light fuels, use of lower viscosity lubricating oil for topping up or by contamination with cleaning fluids.
4. Alkalinity
PH paper indicator is used to check the reserve alkalinity in the oil sample.
If the alkalinity of the lube oil has dropped too much, there is a serious risk of corrosive wear of the cylinder liners, piston rings and bearings (anti-friction layer) as the oil has not enough potential to neutralise the sulphuric acid produced by fuel combustion. This neutralisation results in the formation of either calcium or magnesium sulphates (depending on the additive contained in the lube oil) which inevitably become part of the insoluble carried by the lube oil when returning to the crankcase.
If the alkalinity of the lube oil has dropped too much, there is a serious risk of corrosive wear of the cylinder liners, piston rings and bearings (anti-friction layer) as the oil has not enough potential to neutralise the sulphuric acid produced by fuel combustion. This neutralisation results in the formation of either calcium or magnesium sulphates (depending on the additive contained in the lube oil) which inevitably become part of the insoluble carried by the lube oil when returning to the crankcase.
5. Flash point
Onboard ship if Pensky-Martine apparatus is available, the flash point can be checked. Lube oil flash point changes when fuel oil mixes in it.
A drop in the flash point normally indicates contamination of the lubricant by distillate fuel, although with residual fuel no significant change may be apparent. For guidance, it is advisable to check for fuel leakages when the flash point drops by 30°C or more. A reduced Flash Point normally indicates that there is a fuel leakage into the lubrication system. A more precise test method for measuring fuel contamination in distillate fueled engine oil, which is commonly utilized in used oil analysis laboratories, is gas chromatography. However, in order to detect fuel leakages via the flash point, only results achieved with the same test method can be compared.
Crankcase Explosions
Temperature limits for safe/unsafe operation have been found unreliable because crankcase explosions have been reported where high flash points are measured. The current position is that two preconditions must exist for a crankcase explosion to occur
1. The presence of a flammable vapour atmosphere (ratio of oil droplet size to oxygen)
2. A heat source or “hot spot”.
A hot spot can be a hot running bearing, a fire outside the engine or piston failure undetected by a defective or switched off oil mist detectors, etc.
A drop in the flash point normally indicates contamination of the lubricant by distillate fuel, although with residual fuel no significant change may be apparent. For guidance, it is advisable to check for fuel leakages when the flash point drops by 30°C or more. A reduced Flash Point normally indicates that there is a fuel leakage into the lubrication system. A more precise test method for measuring fuel contamination in distillate fueled engine oil, which is commonly utilized in used oil analysis laboratories, is gas chromatography. However, in order to detect fuel leakages via the flash point, only results achieved with the same test method can be compared.
Crankcase Explosions
Temperature limits for safe/unsafe operation have been found unreliable because crankcase explosions have been reported where high flash points are measured. The current position is that two preconditions must exist for a crankcase explosion to occur
1. The presence of a flammable vapour atmosphere (ratio of oil droplet size to oxygen)
2. A heat source or “hot spot”.
A hot spot can be a hot running bearing, a fire outside the engine or piston failure undetected by a defective or switched off oil mist detectors, etc.
6. Spot test
It shows the amount of insoluble in the oil. This test also know as Blotter Test or patch test, which can be used to quickly reference the condition of used engine oil. This is a highly subjective analysis and as such no standards currently exist for the analysis of the patches. However, it has value as a very inexpensive and useful trending tool. The two main features are the amount of insolubles present and the condition of the dispersancy additive. If the oil is new, the patch will be uniform and exhibit no ring formation. As the oil ages then the patch will darken due to increased insoluble particulate, but may remain without rings due to the presence of sufficient dispersancy additive. As this additive weakens then rings start to form as the insolubles start to
become less susceptible to the effects of the remaining dispersancy. However dispersancy characteristics will vary from a uniform light grey deposit where dispersancy is good to one of to a dark two phase deposit. At this point issues in future performance are of concern, because the deposits within the engine itself may not be able to be reabsorbed into the new charge or fresh top up. Other aspects that can be detected are fuel content, usually as a clear external ring and water which causes the insolubles to form uneven dropouts or spots.They rely upon the relative density and film forming properties of the various constituents of the used lubricant. More specifically, as an oil ages and the dispersancy and detergency capabilities deteriorate, it is possible to detect these via the different types of pattern that are left behind.
A small quantity of used oil sample and the corresponding fresh oil is dropped onto a sheet of special filter paper and allowed to spread. For simple tests it is used purely for comparison. For the basic analysis the droplet will behave in a number of ways. Firstly the insolubles will separate from the oil thus allowing a basic comparison to be made. Quantification of this can be assessed by the trained analyst but should not be quoted as there are no statistical qualitative or quantative controls which apply in this regard.
become less susceptible to the effects of the remaining dispersancy. However dispersancy characteristics will vary from a uniform light grey deposit where dispersancy is good to one of to a dark two phase deposit. At this point issues in future performance are of concern, because the deposits within the engine itself may not be able to be reabsorbed into the new charge or fresh top up. Other aspects that can be detected are fuel content, usually as a clear external ring and water which causes the insolubles to form uneven dropouts or spots.They rely upon the relative density and film forming properties of the various constituents of the used lubricant. More specifically, as an oil ages and the dispersancy and detergency capabilities deteriorate, it is possible to detect these via the different types of pattern that are left behind.
A small quantity of used oil sample and the corresponding fresh oil is dropped onto a sheet of special filter paper and allowed to spread. For simple tests it is used purely for comparison. For the basic analysis the droplet will behave in a number of ways. Firstly the insolubles will separate from the oil thus allowing a basic comparison to be made. Quantification of this can be assessed by the trained analyst but should not be quoted as there are no statistical qualitative or quantative controls which apply in this regard.
For a more quantitative assessment of insolubles there is a more detailed analysis based upon a photometric measurement. After patch development is complete, the sheet is then transferred to a special photometer which has been adjusted to zero using the spot of the fresh oil. The absorbance of used oil spot is measured automatically over concentric zones. Absorbance in the central zone provides a measure of the amount of sooty insoluble material present in the used oil and the radial distribution of absorbance relates to the lubricant’s dispersancy.
Blotter Test or spot test is a highly subjective analysis and as such no standards currently exist for the analysis of the patches. However, it has value as a very inexpensive and useful trending tool. The two main features are the amount of insolubles present and the condition of the dispersancy additive. If the oil is new, the patch will be uniform and exhibit no ring formation. As the oil ages then the patch will darken due to increased insoluble particulate, but may remain without rings due to the presence of sufficient dispersancy additive. As this additive weakens then rings start to form as the insolubles start to become less susceptible to the effects of the remaining dispersancy. However dispersancy characteristics will vary from a uniform light grey deposit where dispersancy is good to one of to a dark two phase deposit. At this point issues in future performance are of concern, because the deposits within the engine itself may not be able to be reabsorbed into the new charge or fresh top up. Other aspects that can be detected are fuel content, usually as a clear external ring and water which causes the insolubles to form uneven dropouts or spots..
7. Chloride/Sea water content
This test is indication of the sea water contamination in the oil. 5ml sample oil is mixed with 5ml of distilled water. Separate the water and take one ml of it. Add 3-5drops of mercuric thiocyanate and an iron salt. This will give a reddish orange mixture which is an indication of presence of chloride. The colour can be the compared with to a scale chart calibrated from 0 to 300ppm. The colour change took place because of the formation of chloromercurate and ferric thicyanate.
Shore Testing
1. Spectro-Analysis(metal/additives contamination)
The metallic elements in the oil are measured by spectroscopic methods. This can be atomic emission, atomic absorption or X-ray fluorescence spectroscopy.
The elements measured include additive elements, wear metals, combustion products and external contaminants e.g. from cooling water or intake air. Therefore these values are influenced by the additive package of the oil, component wear and fuel combustion.
Mostly Plasma Emission Spectrometry (ICP - Inductively Coupled Plasma) is used to determine the metal contents of used lubricating oils. However particles bigger than 5 - 7μm are not detected by this method as they are not fully vaporised in the plasma due to mass effects and so wear element concentration can be underestimated in cases of particularly high wear. Here non-routine analysis like x-ray fluorescence spectroscopy, ashing of the sample before ICP measurement (to collect 100% of the material within the sample), ferrography, ferrometry, PQ (Particle Quantifier) and similar methods can help.
It must be realised that - according to the type of apparatus and way of sample preparation, the results obtained can be very different. When comparing and plotting results for trend analysis, therefore, it is important to ensure that the data are generated by the same laboratory, the same apparatus and the same method.
The accuracy and lower detection limits of the methods have to be considered carefully before any alarm or alert condition is applied to the analysis- especially low values (below 5 ppm) should be interpreted with caution.
Spectro-Analysis is done by Plasma Atomic Emission procedure for particles of 10 micron (or less) in size. The quantity of these particles can be determined by a particle quantifier which gauges the quantity in terms of PR index". Separation of the particles is done by a rotary particle depositor.
Additive Elements: Ca, Si, Mg, P, Zn.
Their concentration can serve for the identification of the lubricant in use, or as an indicator that the lubricant analysed has been mixed or contaminated by another type of oil grade or brand.
Wear elements: Al, Cr, Cu, Fe, Mo, Pb, Sb, Sn.
These may indicate wear of bearings, piston rings, cylinder liners and other engine components. Component wear is directly influenced by the engine type i.e. the internal component technology, the mode of engine operation (speed, partial or full load profile, number of daily starts etc.).
a. Molybdenum (Mo) can also be an additive element contained within the lubricating oil and or cooling water. As a consequence limit values cannot be given. The only way to appreciate the analysis results is to plot the different values and follow the trends using the same test method. A correct interpretation of the different metal contents can only be done if there is a significant historical feedback, either built up by the customer on similar engines or by the engine builder. It has to be mentioned that the most often used method of metals analysis, ICP, is insensitive to particles above 5-7μm.
Oil Contaminants: Na, Ni, V, Al, Si, Cl, Mg, B, K.
K, Mg, B, Cl and Na derive from water based contaminants, condensate, sea water, coolant etc. Si may come from dust/sand (e.g. Aluminium Silicate) but is typically also contained in lubricating oil additives (anti-foam). V and Ni derive from fuel in case HFO is used. Na and K can derive from heavy fuel oil and diesel fuels containing biodiesel or can be present from additives used in the engine coolant.
a. Iron:- Iron present in lube oil in excess amount is the result of wear out of the following lubricated moving parts of the engine.
Cylinder walls and liners
Crank and cam shafts;
Valve guides;
Rockers;
Rings:
Bearings;
Gears;
Shafts
b. Copper
Presence of copper in the lube oil is mainly due to bushing and bearing metal wear.
Copper alloys such as brass & bronze are used in the following components:-
Big-end and crankshaft bearings;
Bushings;
Oil coolers;
Washers;
Copper based anti-seizing compounds
c. Antimony
Presence of excessive Antimony is the clear indication of wear of white metal.
White metal bearings have a composition of 88%Sn, 8%Sb and 4%Cu.
Main Bearing shell, Bottom end bearing shells and Cross head bearing etc. are to be inspected when Antimony is found in excess amount in lube oil.
d. Tin
Presence of excessive Tin is the clear indication of wear of white metal.
White metal bearings have a composition of 88%Sn, 8%Sb and 4%Cu.
Main Bearing shell, Bottom end bearing shells and Cross head bearing etc. are to be inspected when Tin is found in excess amount in lube oil.
e. Silica
Silica may come from dust/sand (e.g. Aluminium Silicate) but is typically also contained in lubricating oil additives (anti-foam). Excessive silica present in the lube oil is the indication of ingress of Dirt. It can present major hazard for the lubricated components as it is highly abrasive.
The following areas are required to be inspected and maintained:-
Air inlet filter of turbocharger is in proper condition. Covered adequately with a fine felt filter. The air filter should be check for any damage and proper fitting. Renew the filters at appropriate times.
Air breathers and sounding pipes of the storage tanks are also ways for ingress of dirt. Breathers should be properly covered with proper felt filters and Sounding pipes caps must be kept close when not in use. Also care must be taken when using sampling and sounding equipment in the tanks, dirt accumulated on those equipment can be a source of contamination.
f. Chrome
Crome is present in piston rings as a layer or in full.
g. Sodium
Sodium comes from sea water ingress or from HFO contamination.
h. Vanadium
Vanadium comes from HFO contamination.
The elements measured include additive elements, wear metals, combustion products and external contaminants e.g. from cooling water or intake air. Therefore these values are influenced by the additive package of the oil, component wear and fuel combustion.
Mostly Plasma Emission Spectrometry (ICP - Inductively Coupled Plasma) is used to determine the metal contents of used lubricating oils. However particles bigger than 5 - 7μm are not detected by this method as they are not fully vaporised in the plasma due to mass effects and so wear element concentration can be underestimated in cases of particularly high wear. Here non-routine analysis like x-ray fluorescence spectroscopy, ashing of the sample before ICP measurement (to collect 100% of the material within the sample), ferrography, ferrometry, PQ (Particle Quantifier) and similar methods can help.
It must be realised that - according to the type of apparatus and way of sample preparation, the results obtained can be very different. When comparing and plotting results for trend analysis, therefore, it is important to ensure that the data are generated by the same laboratory, the same apparatus and the same method.
The accuracy and lower detection limits of the methods have to be considered carefully before any alarm or alert condition is applied to the analysis- especially low values (below 5 ppm) should be interpreted with caution.
Spectro-Analysis is done by Plasma Atomic Emission procedure for particles of 10 micron (or less) in size. The quantity of these particles can be determined by a particle quantifier which gauges the quantity in terms of PR index". Separation of the particles is done by a rotary particle depositor.
Additive Elements: Ca, Si, Mg, P, Zn.
Their concentration can serve for the identification of the lubricant in use, or as an indicator that the lubricant analysed has been mixed or contaminated by another type of oil grade or brand.
Wear elements: Al, Cr, Cu, Fe, Mo, Pb, Sb, Sn.
These may indicate wear of bearings, piston rings, cylinder liners and other engine components. Component wear is directly influenced by the engine type i.e. the internal component technology, the mode of engine operation (speed, partial or full load profile, number of daily starts etc.).
a. Molybdenum (Mo) can also be an additive element contained within the lubricating oil and or cooling water. As a consequence limit values cannot be given. The only way to appreciate the analysis results is to plot the different values and follow the trends using the same test method. A correct interpretation of the different metal contents can only be done if there is a significant historical feedback, either built up by the customer on similar engines or by the engine builder. It has to be mentioned that the most often used method of metals analysis, ICP, is insensitive to particles above 5-7μm.
Oil Contaminants: Na, Ni, V, Al, Si, Cl, Mg, B, K.
K, Mg, B, Cl and Na derive from water based contaminants, condensate, sea water, coolant etc. Si may come from dust/sand (e.g. Aluminium Silicate) but is typically also contained in lubricating oil additives (anti-foam). V and Ni derive from fuel in case HFO is used. Na and K can derive from heavy fuel oil and diesel fuels containing biodiesel or can be present from additives used in the engine coolant.
a. Iron:- Iron present in lube oil in excess amount is the result of wear out of the following lubricated moving parts of the engine.
Cylinder walls and liners
Crank and cam shafts;
Valve guides;
Rockers;
Rings:
Bearings;
Gears;
Shafts
b. Copper
Presence of copper in the lube oil is mainly due to bushing and bearing metal wear.
Copper alloys such as brass & bronze are used in the following components:-
Big-end and crankshaft bearings;
Bushings;
Oil coolers;
Washers;
Copper based anti-seizing compounds
c. Antimony
Presence of excessive Antimony is the clear indication of wear of white metal.
White metal bearings have a composition of 88%Sn, 8%Sb and 4%Cu.
Main Bearing shell, Bottom end bearing shells and Cross head bearing etc. are to be inspected when Antimony is found in excess amount in lube oil.
d. Tin
Presence of excessive Tin is the clear indication of wear of white metal.
White metal bearings have a composition of 88%Sn, 8%Sb and 4%Cu.
Main Bearing shell, Bottom end bearing shells and Cross head bearing etc. are to be inspected when Tin is found in excess amount in lube oil.
e. Silica
Silica may come from dust/sand (e.g. Aluminium Silicate) but is typically also contained in lubricating oil additives (anti-foam). Excessive silica present in the lube oil is the indication of ingress of Dirt. It can present major hazard for the lubricated components as it is highly abrasive.
The following areas are required to be inspected and maintained:-
Air inlet filter of turbocharger is in proper condition. Covered adequately with a fine felt filter. The air filter should be check for any damage and proper fitting. Renew the filters at appropriate times.
Air breathers and sounding pipes of the storage tanks are also ways for ingress of dirt. Breathers should be properly covered with proper felt filters and Sounding pipes caps must be kept close when not in use. Also care must be taken when using sampling and sounding equipment in the tanks, dirt accumulated on those equipment can be a source of contamination.
f. Chrome
Crome is present in piston rings as a layer or in full.
g. Sodium
Sodium comes from sea water ingress or from HFO contamination.
h. Vanadium
Vanadium comes from HFO contamination.
2. Flash point
For a fresh lube oil the flash point should be at least 220 deg.C. Pensky Martens standard apparatus is used to determine the flash point. The sample is slowly heated in a closed apparatus at a constant rate and an external flame is introduced at different temperate intervals through an open shutter.
The temperature at which a spark or a flame can ignite the oil vapor is called the flash point. This is the lowest temperature, at which vapours from the oil can be ignited. Change of flash point is mainly influenced by fuel contamination and to a certain extent by oil degradation.
There are different Industry flash point test methods including the “Open Cup” and “Closed Cup” type methods.
It must be noted that due to evaporation losses the result with the Closed Cup method is generally lower than the result with the Open Cup method. Flash Point is NOT a measure of flammability. A drop in the flash point normally indicates contamination of the lubricant by distillate fuel, although with residual fuel no significant change may be apparent. For guidance, it is advisable to check for fuel leakages when the flash point drops by 30°C or more. A reduced Flash Point normally indicates that there is a fuel leakage into the lubrication system. A more precise test method for measuring fuel contamination in distillate fueled engine oil, which is commonly utilized in used oil analysis laboratories, is gas chromatography. However, in order to detect fuel leakages via the flash point, only results achieved with the same test method can be compared.
There are different Industry flash point test methods including the “Open Cup” and “Closed Cup” type methods.
It must be noted that due to evaporation losses the result with the Closed Cup method is generally lower than the result with the Open Cup method. Flash Point is NOT a measure of flammability. A drop in the flash point normally indicates contamination of the lubricant by distillate fuel, although with residual fuel no significant change may be apparent. For guidance, it is advisable to check for fuel leakages when the flash point drops by 30°C or more. A reduced Flash Point normally indicates that there is a fuel leakage into the lubrication system. A more precise test method for measuring fuel contamination in distillate fueled engine oil, which is commonly utilized in used oil analysis laboratories, is gas chromatography. However, in order to detect fuel leakages via the flash point, only results achieved with the same test method can be compared.
3. Base number
In shore based laboratories the BN of sample lube oil is determined by using titration methods. Electronically controlled titration gives a highly accurate result.
Oil sample is added with Anhydrous chloro benzene and Glacial acid. This mixture is titrated by perchloric acid and glacial acid solution.
4. Viscosity
The kinematic viscosity is commonly referred to as just ‘viscosity’ and is determined by measuring the time a fluid needs to flow through a defined capillary at a defined temperature. The viscosity describes the flow resistance of a fluid and is typically expressed as a kV@40 or kV@100 test result,
where 40 or 100 denotes the test temperature used (°C).
The viscosity of lubricating oil is defined at 100°C according to the SAE J300 Industry Classification System and is expressed in mm2 s-1 or cSt (centistokes). In practice, this parameter is also measured at 40°C and many used oil analysis laboratories report the viscosity measurement at 40°C, 100°C or both. Kinematic viscosity is the absolute or dynamic viscosity in Pa. S divided by the fluid density.
Change to oil viscosity during operation is mainly influenced by oil contamination (Insolubles, fuel, soot, particles and water) and oxidation. In the case of a two stroke engine, the system oil could also be contaminated by the cylinder oil.
VI (Viscosity Index)
The VI is calculated from the two measurements of viscosity at 100°C and 40°C and describes the viscosity-temperature relationship of the oil. A high VI indicates a small change of viscosity with temperature.
The VI is mainly defined by the base oil properties and by additives used.
A high VI is important for multi-grade oils where a restricted range of viscosity over a large temperature range is required to meet specification. Such a high VI enables optimum performance under varying temperature conditions.
where 40 or 100 denotes the test temperature used (°C).
The viscosity of lubricating oil is defined at 100°C according to the SAE J300 Industry Classification System and is expressed in mm2 s-1 or cSt (centistokes). In practice, this parameter is also measured at 40°C and many used oil analysis laboratories report the viscosity measurement at 40°C, 100°C or both. Kinematic viscosity is the absolute or dynamic viscosity in Pa. S divided by the fluid density.
Change to oil viscosity during operation is mainly influenced by oil contamination (Insolubles, fuel, soot, particles and water) and oxidation. In the case of a two stroke engine, the system oil could also be contaminated by the cylinder oil.
VI (Viscosity Index)
The VI is calculated from the two measurements of viscosity at 100°C and 40°C and describes the viscosity-temperature relationship of the oil. A high VI indicates a small change of viscosity with temperature.
The VI is mainly defined by the base oil properties and by additives used.
A high VI is important for multi-grade oils where a restricted range of viscosity over a large temperature range is required to meet specification. Such a high VI enables optimum performance under varying temperature conditions.
5. Density
Measured by a hydrometer at a given temperature and density is useful for the selection of gravity disc.
6. Insoluble content
Insoluble can be defined as solid material that can be isolated from the oil by filtration or by centrifugation after a solvent (pentane, heptane or toluene) has been added. However it should be realised that this is not the amount of insoluble material (particles) in the oil. It’s important to know that different insolubles analysis methods will generate different values and so only the analyses made by the same test method are reliably comparable with one another.
The amount of Insolubles is increased in case of oil contamination (e.g. fuel) and by degradation of additives. Insoluble Content It is a measurement of the Pentane or Toluene insolubles.
For Pentane insolubles : A mixture of the oil sample and pentane is centrifuged. It is decanted and the precipitate washed with pentane twice. The dried weight gives the Pentane insolubles i.e. insoubles due to wear, carbon or dirt particles.
For Toluene insolubles : A mixture of the oil sample and pentane is centrifuged. It is decanted and the precipitate washed off with pentane twice. It is then washed once with a toluene alcohol solution, and again with toluene. The dried weight gives the toluene insolubles i.e. dirt and inorganic particles.
The control of the insolubles level in used lubricating oil is important for satisfactory lubrication of an engine and long term engine reliability. It requires an integrated view of the engine, the lubricating oil quality being used, the used lubricating oil condition and the effectiveness of the lubricant maintenance system. This, in particular, is relevant in engines with low lubricating oil consumption and/or extended drain intervals.
A high insolubles result can occur for a number of different reasons. Although particles are included in the insolubles, the main fraction are contaminants and degradation products that are dissolved or dispersed in the oil and cannot be considered as particles. The content of insolubles is a composite parameter that reflects the degree of oil degradation and oil contamination.
Contaminants, as described above, can increase the viscosity of the lubricating oil and may lead to the formation of deposits on piston under-crowns and filters. Also, the heat transfer performance of lubricating oil coolers may be compromised.
The amount of Insolubles is increased in case of oil contamination (e.g. fuel) and by degradation of additives. Insoluble Content It is a measurement of the Pentane or Toluene insolubles.
For Pentane insolubles : A mixture of the oil sample and pentane is centrifuged. It is decanted and the precipitate washed with pentane twice. The dried weight gives the Pentane insolubles i.e. insoubles due to wear, carbon or dirt particles.
For Toluene insolubles : A mixture of the oil sample and pentane is centrifuged. It is decanted and the precipitate washed off with pentane twice. It is then washed once with a toluene alcohol solution, and again with toluene. The dried weight gives the toluene insolubles i.e. dirt and inorganic particles.
The control of the insolubles level in used lubricating oil is important for satisfactory lubrication of an engine and long term engine reliability. It requires an integrated view of the engine, the lubricating oil quality being used, the used lubricating oil condition and the effectiveness of the lubricant maintenance system. This, in particular, is relevant in engines with low lubricating oil consumption and/or extended drain intervals.
A high insolubles result can occur for a number of different reasons. Although particles are included in the insolubles, the main fraction are contaminants and degradation products that are dissolved or dispersed in the oil and cannot be considered as particles. The content of insolubles is a composite parameter that reflects the degree of oil degradation and oil contamination.
Contaminants, as described above, can increase the viscosity of the lubricating oil and may lead to the formation of deposits on piston under-crowns and filters. Also, the heat transfer performance of lubricating oil coolers may be compromised.
7. Water content
It can be measured by distillation method. oil is heated under reflux with a water-immiscible solvent. The condensed water is separated from the solvent in a trap.
The water content of used oil is typically measured by Karl-Fischer titration or by infrared spectroscopy rather than by the more commonly referenced distillation method. Water can originate from various sources and can cause fresh or sea water contamination of the oil. Water in lubricating oil is a pollutant and is potentially harmful to the engine even in low quantity. Unfortunately traces of water in used lubricating oil tend to be unavoidable - they can result from internal leakages (water jacket, coolers), build up of condensation, or, through use of an incorrectly set separator. Water content can be measured in two ways – either as an absolute value (percent or ppm), or as the degree of maximum water saturation possible within the oil (the water activity). Different oil types have different saturation point and this point will change with temperature, relative humidity, contamination
and oil ageing. These contamination and oil ageing effects may not necessarily render the method inaccurate, but they will have to be considered when developing a sensor based water analysing system. The water content has to be low to avoid bearing damage (displacement of the oil film by free water droplets) and can be lead to an emulsification of the lubricant, which can cause cavitation inside engine bearings. It is commonly agreed to avoid water contents of more than 0.2%. High water content may also lead to corrosive attack on the bearings. Unless emulsified into the system oil, centrifugation of the system oil will remove the water. As system oil is usually only analysed a few times a year, short periods of water contamination might never be discovered unless they result in bearing damage. For this reason, some engine manufacturers recommend to use online water analysis equipment.
Apart from a direct analytical determination of the water content, the measurement of chloride and of sodium also can give an indication of water contamination. Water affects the viscosity and lubricity of the lubricating oil and if not removed may form an emulsion with it. It is, therefore, desirable to keep the water content as low as possible by centrifuging (if installed). If the water content exceeds 0.2% (v/v), appropriate operation of the centrifuge should be carefully checked and if necessary adjusted to ensure optimum lubricating oil / water separation. In addition root causes of water contamination should be investigated and solved as soon as possible. Some lubricants can form water-in-oil emulsions preventing the water from being removed by centrifuge alone. Such emulsion, if circulated, will reduce the load carrying capacity of the lubricating oil in bearings and may lead to failures. In some cases it is possible to drive off and thus reduce the water content by higher temperature purification at ~95ºC, if this is not possible as a consequence, any emulsified lubricating oil should be replaced as soon as possible.
Alkaline and most other additives are sensitive to water content. If lubricating oil is contaminated by water, additive depletion could take place, which means, among other effects, a drop of BN. With water, additives form insolubles sludges which are disposed in the centrifuge. Used lubricating oils exhibit greater intolerance compared to the same lubricating oil when new. Sea water is corrosive and potentially harmful. Whether corrosion will actually occur in the engine depends on a number of factors - for instance, how much salt is in the lubricating oil, how much water and strong acids are also present and whether the lubricating oil retains sufficient anti-corrosion performance capability.
The water content of used oil is typically measured by Karl-Fischer titration or by infrared spectroscopy rather than by the more commonly referenced distillation method. Water can originate from various sources and can cause fresh or sea water contamination of the oil. Water in lubricating oil is a pollutant and is potentially harmful to the engine even in low quantity. Unfortunately traces of water in used lubricating oil tend to be unavoidable - they can result from internal leakages (water jacket, coolers), build up of condensation, or, through use of an incorrectly set separator. Water content can be measured in two ways – either as an absolute value (percent or ppm), or as the degree of maximum water saturation possible within the oil (the water activity). Different oil types have different saturation point and this point will change with temperature, relative humidity, contamination
and oil ageing. These contamination and oil ageing effects may not necessarily render the method inaccurate, but they will have to be considered when developing a sensor based water analysing system. The water content has to be low to avoid bearing damage (displacement of the oil film by free water droplets) and can be lead to an emulsification of the lubricant, which can cause cavitation inside engine bearings. It is commonly agreed to avoid water contents of more than 0.2%. High water content may also lead to corrosive attack on the bearings. Unless emulsified into the system oil, centrifugation of the system oil will remove the water. As system oil is usually only analysed a few times a year, short periods of water contamination might never be discovered unless they result in bearing damage. For this reason, some engine manufacturers recommend to use online water analysis equipment.
Apart from a direct analytical determination of the water content, the measurement of chloride and of sodium also can give an indication of water contamination. Water affects the viscosity and lubricity of the lubricating oil and if not removed may form an emulsion with it. It is, therefore, desirable to keep the water content as low as possible by centrifuging (if installed). If the water content exceeds 0.2% (v/v), appropriate operation of the centrifuge should be carefully checked and if necessary adjusted to ensure optimum lubricating oil / water separation. In addition root causes of water contamination should be investigated and solved as soon as possible. Some lubricants can form water-in-oil emulsions preventing the water from being removed by centrifuge alone. Such emulsion, if circulated, will reduce the load carrying capacity of the lubricating oil in bearings and may lead to failures. In some cases it is possible to drive off and thus reduce the water content by higher temperature purification at ~95ºC, if this is not possible as a consequence, any emulsified lubricating oil should be replaced as soon as possible.
Alkaline and most other additives are sensitive to water content. If lubricating oil is contaminated by water, additive depletion could take place, which means, among other effects, a drop of BN. With water, additives form insolubles sludges which are disposed in the centrifuge. Used lubricating oils exhibit greater intolerance compared to the same lubricating oil when new. Sea water is corrosive and potentially harmful. Whether corrosion will actually occur in the engine depends on a number of factors - for instance, how much salt is in the lubricating oil, how much water and strong acids are also present and whether the lubricating oil retains sufficient anti-corrosion performance capability.
8. Micro-Biological test.
Micro Biological Test This test is only carried out if the lube oil.is suspected of microbial degradation. A nutritive gel is applied over a glass slide and immersed in the oil sample. It is allowed to incubate for 12 hours. Bacteria manifests itself by red spots on the slide which is then crammed with a reference guide.
Microbial Degradation of Lube Oil.
It is the degradation that takes place due to microorganisms thriving in the lube oil. Micro-organisms are bacteria, yeasts or moulds. They require phosphorous, nitrogen, carbon and water. They require water to grow in the beginning, but later they can self-sustain themselves at 20 to 40 deg.C. in stagnant conditions. The danger is that they multiply at a very rapid rate i.e. double in size and divide into two every half hour. Once the aerobic bacteria have consumed the dissolved oxygen, the sulphate reducing bacteria activated. This bacteria attacks the metal and forms hydrogen sulphide. It results in corrosion of steel. The properties of the lube oil add its additives are also affected, enhancing corrosion and reducing the load bearing capacity. Acids are formed which cause corrosion especially at Oxygen depleted zones. This microbial degradation is mostly seen in distillate fuels and not residual fuels.
Indications Rotten egg smells, sliminess of the oil in the crankcase painted surfaces. increased acidity and water content, filter choking more frequently, poor heat exchanger performance, black staining of white metal bearings and corrosion of exposed steel surfaces.
Prevention:
Crankcase water content to be weekly monitored and within limits. Lube oil bearing surfaces, exposed steel Work and crankcase painted surfaces is to be visually inspected during every crankcase inspection. Regular circulation of oil to be carried out by pumps to avoid stagnant conditions. Lube oil temperature at the purifier is to be at least 75 deg.C. as the bacteria perish above 70 deg.C. Purification and re-circulation of crankcase oil is to be continued even when the engine is stopped at port. Regular testing at various sample points is to be done. Inspection of sludge from purifiers or choked filters also indicates any degradation of tube oil.
Treatment:
Use of biocides or fungicides is carried out Heating and continuous purification above 75 deg.C. is done and the entire sump to be purified within a period of 12 hours. Heating is done to a temperature of 80deg.C, but not exceeding the supplier's limit. This kills the bacteria. Manual cleaning of the sump, filters and pipelines is carried out. Replenishment of the sump oil is done in case the lube oil is badly infected.
Microbial Degradation of Lube Oil.
It is the degradation that takes place due to microorganisms thriving in the lube oil. Micro-organisms are bacteria, yeasts or moulds. They require phosphorous, nitrogen, carbon and water. They require water to grow in the beginning, but later they can self-sustain themselves at 20 to 40 deg.C. in stagnant conditions. The danger is that they multiply at a very rapid rate i.e. double in size and divide into two every half hour. Once the aerobic bacteria have consumed the dissolved oxygen, the sulphate reducing bacteria activated. This bacteria attacks the metal and forms hydrogen sulphide. It results in corrosion of steel. The properties of the lube oil add its additives are also affected, enhancing corrosion and reducing the load bearing capacity. Acids are formed which cause corrosion especially at Oxygen depleted zones. This microbial degradation is mostly seen in distillate fuels and not residual fuels.
Indications Rotten egg smells, sliminess of the oil in the crankcase painted surfaces. increased acidity and water content, filter choking more frequently, poor heat exchanger performance, black staining of white metal bearings and corrosion of exposed steel surfaces.
Prevention:
Crankcase water content to be weekly monitored and within limits. Lube oil bearing surfaces, exposed steel Work and crankcase painted surfaces is to be visually inspected during every crankcase inspection. Regular circulation of oil to be carried out by pumps to avoid stagnant conditions. Lube oil temperature at the purifier is to be at least 75 deg.C. as the bacteria perish above 70 deg.C. Purification and re-circulation of crankcase oil is to be continued even when the engine is stopped at port. Regular testing at various sample points is to be done. Inspection of sludge from purifiers or choked filters also indicates any degradation of tube oil.
Treatment:
Use of biocides or fungicides is carried out Heating and continuous purification above 75 deg.C. is done and the entire sump to be purified within a period of 12 hours. Heating is done to a temperature of 80deg.C, but not exceeding the supplier's limit. This kills the bacteria. Manual cleaning of the sump, filters and pipelines is carried out. Replenishment of the sump oil is done in case the lube oil is badly infected.
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