Answer EKG Question 39
Q39. A. Explain how analysis of used lubricating oil can be used as a “health-monitoring” tool for diesel engines.
B. Describe how vibration measurement can be used with a main engine turbo-charger:
i. For fault analysis;
ii. For condition monitoring with respect to maintenance;
B. Describe how vibration measurement can be used with a main engine turbo-charger:
i. For fault analysis;
ii. For condition monitoring with respect to maintenance;
iii. As a substitute to opening up machinery for survey.
Answer:
Used Oil Analysis is one of the important, and maybe the simplest, approaches to diagnosing the health of an engine. It is, however, not easy for engine users or engineers to understand and interpret each analysis parameter correctly and to assess the condition of the oil and the engine. It is an important part of engine maintenance. It provides information about the condition of the oil, its suitability for further use and to a certain extent information about the condition of the machinery lubricated by the oil.
Need of used oil analysis
The purpose of conducting used oil analysis is two-fold:
a. To assess the condition of the oil - to provide recommendations on its suitability for further use and optimisation of the oil change intervals.
b. To assess the condition of the engine - to enable the detection and thus prevention of issues which left unattended may impact the reliable operation of the engine.
Routine Analyses
The physical & chemical characteristics of an in-service oil are obviously linked back to the specific type of oil, its age and the conditions under which it operates. For engine oils, the tests carried out under “Routine Analyses” will typically include:
1) Viscosity
2) Water content
3) Base Number (BN) or Alkalinity reserve
4) Insolubles
5) Flash Point
6) Elements (measuring the concentration of additives and levels of wear metals, etc.)
These tests are typically carried out in highly automated specialised laboratories. Only a small volume of oil is needed- typically less than 250 ml for a full Routine Analysis, and fully automated equipment can be used. This makes Routine Analysis quick, easy & economical to run. Normally the test method used will be according to conventional ISO or ASTM standards but where in-house specialised test methods are used these can have the advantage that the tests are specifically designed for their relevance to ‘used oil’ based on many years field experience. In cases of a dispute the ISO or ASTM methods are used as the referee method.
In cases where a high degree of test precision is needed standard Routine Analysis testing may not be suitable.
Non Routine Analyses
Sometimes more sophisticated testing is needed to investigate an ongoing problem or to obtain a better diagnosis of the condition of the engine or its components. These analyses are known as “Non Routine” analyses. Such tests can be carried out as part of an investigation or indeed be done as part of an oil based condition monitoring programme. Extended analysis suites can include tests carried out on engine deposits, debris & fuel samples as well as the oil samples themselves.
Non routine analyses typically require larger sample volumes (1 litre or so), and the analyses performed are chosen on a case by case basis with guidance from the oil supplier and / or engine manufacturer. Use of a different laboratory may also be required. It is necessary to provide specific and detailed information on the history of the engine & practical working details in order to determine which analysis is most useful to provide the most relevant diagnosis.
As such Non Routine analyses are more time consuming and specialised, they are also more costly so
it is important to provide as much background information on the nature of the problem at the point of
submitting the sample.
Key Actions required for a correct analysis
In order to enable a full and proper routine or non routine analysis it is essential that:
a. The oil sample bottles are clean
b. The oil sample taken is representative of the oil in service,
c. All supporting details (e.g. sampling point, date, oil name and hours of service) are attached to the sample container and so are made available to the laboratory
d. The sample is quickly dispatched to the laboratory
Sampling Procedure
How, when and where a sample is taken from within the lubrication system is very important. This is because only a very small amount of oil is taken during sampling. A 250 ml sample represents only a very small percentage of the total oil capacity which can be up to 100,000 litres. It goes without saying that it is essential to be sure that the sample taken is truly representative of the full oil volume and take the necessary precautions when sampling oils which may be hot and contained within pressurised systems, the use of gloves and face protection is advisory.
Some general, but key points regarding the acquisition of representative oil samples include:
a. Sample when the machine is running at normal operating temperature, never when the equipment is stationary or cold, or after any significant addition of fresh oil.
b. Sample from the main supply line of the engine, if necessary arrange to fit dedicated sampling valves that can be accessed easily and safely.
c. Always sample from the same sampling point for any particular piece of equipment.
d. Sample after flushing a small quantity of oil (0.5 - 1.0l) through the sampling point - and without operating the sampling valve between flushing and sampling.
e. Whenever possible fill the sample directly into the sampling bottle to avoid any unnecessary contamination.
f. Use only dedicated clean and dry sampling equipment intended for the sampling of used oils.
g. To avoid leakage fill the sample bottle to 90% capacity and ensure it is properly sealed before despatch to the laboratory.
Used Oil Analysis is one of the important, and maybe the simplest, approaches to diagnosing the health of an engine. It is, however, not easy for engine users or engineers to understand and interpret each analysis parameter correctly and to assess the condition of the oil and the engine. It is an important part of engine maintenance. It provides information about the condition of the oil, its suitability for further use and to a certain extent information about the condition of the machinery lubricated by the oil.
Need of used oil analysis
The purpose of conducting used oil analysis is two-fold:
a. To assess the condition of the oil - to provide recommendations on its suitability for further use and optimisation of the oil change intervals.
b. To assess the condition of the engine - to enable the detection and thus prevention of issues which left unattended may impact the reliable operation of the engine.
Routine Analyses
The physical & chemical characteristics of an in-service oil are obviously linked back to the specific type of oil, its age and the conditions under which it operates. For engine oils, the tests carried out under “Routine Analyses” will typically include:
1) Viscosity
2) Water content
3) Base Number (BN) or Alkalinity reserve
4) Insolubles
5) Flash Point
6) Elements (measuring the concentration of additives and levels of wear metals, etc.)
These tests are typically carried out in highly automated specialised laboratories. Only a small volume of oil is needed- typically less than 250 ml for a full Routine Analysis, and fully automated equipment can be used. This makes Routine Analysis quick, easy & economical to run. Normally the test method used will be according to conventional ISO or ASTM standards but where in-house specialised test methods are used these can have the advantage that the tests are specifically designed for their relevance to ‘used oil’ based on many years field experience. In cases of a dispute the ISO or ASTM methods are used as the referee method.
In cases where a high degree of test precision is needed standard Routine Analysis testing may not be suitable.
Non Routine Analyses
Sometimes more sophisticated testing is needed to investigate an ongoing problem or to obtain a better diagnosis of the condition of the engine or its components. These analyses are known as “Non Routine” analyses. Such tests can be carried out as part of an investigation or indeed be done as part of an oil based condition monitoring programme. Extended analysis suites can include tests carried out on engine deposits, debris & fuel samples as well as the oil samples themselves.
Non routine analyses typically require larger sample volumes (1 litre or so), and the analyses performed are chosen on a case by case basis with guidance from the oil supplier and / or engine manufacturer. Use of a different laboratory may also be required. It is necessary to provide specific and detailed information on the history of the engine & practical working details in order to determine which analysis is most useful to provide the most relevant diagnosis.
As such Non Routine analyses are more time consuming and specialised, they are also more costly so
it is important to provide as much background information on the nature of the problem at the point of
submitting the sample.
Key Actions required for a correct analysis
In order to enable a full and proper routine or non routine analysis it is essential that:
a. The oil sample bottles are clean
b. The oil sample taken is representative of the oil in service,
c. All supporting details (e.g. sampling point, date, oil name and hours of service) are attached to the sample container and so are made available to the laboratory
d. The sample is quickly dispatched to the laboratory
Sampling Procedure
How, when and where a sample is taken from within the lubrication system is very important. This is because only a very small amount of oil is taken during sampling. A 250 ml sample represents only a very small percentage of the total oil capacity which can be up to 100,000 litres. It goes without saying that it is essential to be sure that the sample taken is truly representative of the full oil volume and take the necessary precautions when sampling oils which may be hot and contained within pressurised systems, the use of gloves and face protection is advisory.
Some general, but key points regarding the acquisition of representative oil samples include:
a. Sample when the machine is running at normal operating temperature, never when the equipment is stationary or cold, or after any significant addition of fresh oil.
b. Sample from the main supply line of the engine, if necessary arrange to fit dedicated sampling valves that can be accessed easily and safely.
c. Always sample from the same sampling point for any particular piece of equipment.
d. Sample after flushing a small quantity of oil (0.5 - 1.0l) through the sampling point - and without operating the sampling valve between flushing and sampling.
e. Whenever possible fill the sample directly into the sampling bottle to avoid any unnecessary contamination.
f. Use only dedicated clean and dry sampling equipment intended for the sampling of used oils.
g. To avoid leakage fill the sample bottle to 90% capacity and ensure it is properly sealed before despatch to the laboratory.
B.
Vibration may be the result of general deterioration of the
turbocharger over a period of time or a sudden change in condition. If
allowed to continue unchecked, then serious damage may result. Vibration
monitoring may be used to diagnose faults in the turbocharger (harmonic
filters). As an alarm/shutdown protection, or as a condition monitoring
means in place of inspection.
Gradual increase in vibration normally due by gradual uneven fouling resulting from one or more of the following
(a) Ineffective in service cleaning.
(b) Gradual fouling of damping wires/blade roots.
(c) Deterioration of resilient mountings for bearings.
(d) Slackening of foundation bolts.
(e) External excitation.
Vibration can be prevented by maintaining good combustion and carrying out preventive maintenance, Regular and effective water wash, Regular bearing replacement, Maintenance of foundation and supports.
Sudden increase in vibration normally due to sudden imbalance caused by blade damage resulting from one or more of the following
(a) Sudden imbalance due to partial dirt removal on heavily fouled rotors
(b) Breakage of damping wires
(c) Breakage of resilient mountings
(d) Bearing failure.
(e) Water ingress due to casing leaks
(f) Irregularities in cylinder combustion
(g) Breakage of foundation bolts/supports.
(h) Sudden external excitation.
This can be prevented by maintenance of cylinder condition, regular and effective cleaning, lube. oil and bearing maintenance, regular inspection of casing, foundation bolts, etc.
Gradual increase in vibration normally due by gradual uneven fouling resulting from one or more of the following
(a) Ineffective in service cleaning.
(b) Gradual fouling of damping wires/blade roots.
(c) Deterioration of resilient mountings for bearings.
(d) Slackening of foundation bolts.
(e) External excitation.
Vibration can be prevented by maintaining good combustion and carrying out preventive maintenance, Regular and effective water wash, Regular bearing replacement, Maintenance of foundation and supports.
Sudden increase in vibration normally due to sudden imbalance caused by blade damage resulting from one or more of the following
(a) Sudden imbalance due to partial dirt removal on heavily fouled rotors
(b) Breakage of damping wires
(c) Breakage of resilient mountings
(d) Bearing failure.
(e) Water ingress due to casing leaks
(f) Irregularities in cylinder combustion
(g) Breakage of foundation bolts/supports.
(h) Sudden external excitation.
This can be prevented by maintenance of cylinder condition, regular and effective cleaning, lube. oil and bearing maintenance, regular inspection of casing, foundation bolts, etc.
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