Many people are confused about the different –Type of lubrication in marine diesel engine. Marine diesel engines use a variety of lubricants to keep them running smoothly. It may seem daunting to decide which type of lubrication to use in a marine diesel engine. But with the correct information, it’s not that difficult. This post will cover the different kinds of lubrication used in marine diesel engines. We will also help the readers to understand the benefits of using each type of lubrication.We will also provide the readers with easy-to-read guides that will help them understand the different types of lubrication and how they can be used in marine diesel engines.
What is types of lubrication in marine diesel engine ?
The Definition of Lubrication minimizes the friction between frictions, minimizing material between rubbing surfaces of parts having relative motion. In other terms, lubrication is the solution to energy wastage reduction and deterioration of components/parts. Reduction in wear will help in achieving Maintenance of mechanical equipment at their optimum efficiency and extended mechanical life.
Definition of friction is the force interposed between two contacting surfaces of two bodies and resistance of motion of one body relative to the other. Friction causes deterioration of the surfaces that rub against each other; this is called vernacular wear. The other significant effect of friction is the wastage of energy which is spent in overcoming the friction. Continued operation of a machine in such a state will fail machinery.
Friction is a major headache for the Maintenance engineers since it causes equipment breakdown and continuous replacement of worn-out parts.
Role of Lubricating oil in Diesel Engines
- Reduction of wear in all revolving and sliding surfaces within the engine by abbreviating the friction.
- Decrease in temperature rise by Cooling of under crown and piston ring area
- Cleaning and flushing of pollutants
- Retention of jolts and blows between bearings and other moving components.
- Providing a sealing between piston rings and cylinder liner walls to diminish the infiltration of gases from combustion chamber to crankcase.
- Increased life of machinery
- Reduction in downtime
- Reduces the interruption of machinery operation
- Lower the maintenance cost by reducing the spares consumption
The Main Components of lubricating Oil
- Gear-driven or multi-lobed rotor type Lube Oil circulating pump.
- Pressure Relief valve to manage the constant pressure in the system
- Lubricating oil filters combo of full flow and partial flow type.
- Thermostatic valve
- A shell type of Plate type heat exchanger between the feed pump and the filters.
Before the Engine, the Lube oil discharge pressure is maintained between 0.5 to 2 bar in slow-speed engines and up to 5 bar in high-speed engines.
In dry sump-type Engines, two pumps are installed. Lubricating Oil after circulation flows down by gravity to the engine crankcase pan. The first Pump, known as the scavenging Pump, deports the Oil to a tank independent of the Engine. The second Pump, known as the pressure pump, takes suction from this tank and distributes the Oil through the thermostatic valve, heat exchangers, and filters to the engine lubrication points.
Another arrangement is called a wet sump. In this system lubricating Oil after lubrication falls with gravity in the crankcase known as a sump. Oil is drawn by the pump from the sump and distributes the high-pressure Oil through the thermostatic valve, heat exchangers, and filters to the engine lubrication points.
Types of Maintenance Lube oil Maintenance
The maintenance department looks after the following two types of maintenance
- Corrective maintenance
- Preventive maintenance
Corrective maintenance in (type-of-lubrication-in-marine-diesel-engine)
Corrective maintenance is encompassed during any failure or damage in a machine. This policy is generally adopted in smaller industries where production flow is not affected due to such damages.
Preventive Lubrication Oil Maintenance is the most critical aspect of preventative maintenance. Preventive maintenance aims to achieve the maximum performance of machinery without problem or damage, which would disrupt the production flow
Lubrication Types (Lubrication of Marine Diesel Engine)
- Boundary Lubrication
- Hydrodynamic Lubrication.
- Hydrostatic Lubrication
- Extreme pressure lubrication
In this state of Lubrication, the thickness of the oil film is so small that oiliness becomes the predominant factor. This lubrication condition could be said to exist in some top-end bearing guides.
in Hydrodynamic lubrication the bearing surfaces are entirely separated by an oil layer. The oil film wholly takes the load; the film thickness is more significant at the inlet and remains steady up to the bearing centre, and becomes zero at the outlet. This form of lubricates most suitable for the journal bearings where wedge formation takes place.
In Hydrostatic Lubrication metal surfaces are separated by optimum oil film but the oil pressure is supplied at pressure from external source. The Hydrostatic lubrication is dependant of oil clearance between surfaces and oil inlet pressure.
Wrist pin and cross head pin bearing is the example of such lubrication
Extreme pressure lubrication Lubrication- Hydrodynamic (type-of-lubrication-in-marine-diesel-engine)
Due to theattainment of high local temperature by virtue of high pressure and speed between two sliding surfaces, lubrication fails to stick around the moving surfaces.
To overcome such conditions special additives are added to mineral oils. This type of lubrication is known as extreme pressure lubrication. Added additives form a durable film which can withstand high loads and temperatures.
Factors affecting Hydrodynamic (type-of-lubrication-in-marine-diesel-engine)
- Relative surfaces speed
- Bearing clearances
- Pressure on bearing (per unit area )
Relative surface speed
The higher relative speed is proportional to the greater tendency toward Hydrodynamic Lubrication.
Increasing the diameter of a crankpin/ journal and retaining the rotational speed will increase the relative speed.
– in case of too large clearance knocking will cause. This impulsive loading will increase the pressure between the surfaces and cause boundary lubrication if the clearance is too small; overheating of oil causes the boundary lubrication and will result in a seizure.
Pressure on bearing (per unit area
high load/pressure can lead to boundary lubrication. If the peak pressures are high in cylinders of a diesel engine due to the wrong fuel injection timing or other reasons, bearing pressure will increase.
Diesel Engine Lubrication System (type-of-lubrication-in-marine-diesel-engine
- Viscosity Index
- Pour Point
- Flash Point
- The Fire point
- Total Acid Number or TAN
- Total Base Number or TBN Total Base
- Detergency and dispersancy
- Cold filter filling point
- Demulsification number
Viscosity of the oil is directly proportional to the hydrodynamic lubrication tendency. The temperature will be increased due to insufficient oil circulation to remove the heat generated in a bearing. This condition could be caused by too little clearance and/inadequate supply of oil.
Viscosity results are recorded in the following three ways for type-of-lubrication-in-marine-diesel-engine
Investigate the High and Low Viscosity results to ascertain the cause and should undertake immediate maintenance.
Causes of abnormal Viscosity in type-of-lubrication-in-marine-diesel-engine
- Overextended oil change period
- Oil contamination by water
- Oil mixed with various grades of lubricants.
- Contaminated with anti-freeze
- Break down of additives
- Wrong use of lubricant.
Maintenance action for type-of-lubrication-in-marine-diesel-engine
- Check working temperature
- Check Air-fuel ratio
- Check for polluted new oil
- Check for high soot density
- Check for the grade of oil used
- Check for dilution by fuel
- Check for the equipment operations assessment
- Asses the oil change intervals
- Check for idling period of engine
- Check for the water contamination
- Replace/ repair the defective seal
- Change oil and filters
- Ensure the use of correct grade oil
Observation in abnormal changes of viscosity is severe, and takes immediate action for the maintenance.
Viscosity index is the numerical expression of the average slope of the viscosity – temperature curve of a lubricating oil between 400 C to 1000 C.
Higher the viscosity index lowers the rate at which viscosity decreases with increase of temperature.
Pour point is the temperature below which lubricating oil will lose its flow attributes. The lubricating oil will flow above the pour point temperature under standard conditions. Above the pour point temperature lubricating oil flow with gravity.
Pour point is influenced by presence of waxes..
The minimum temperature at which the lubricating oil gives off adequate vapour to ignite momentarily when a flame of specified standard dimension brought near the oil surface for a prescribed rate in an apparatus of specified dimensions is defined as Flash point.
The Fire point
The Fire point of oil is the lowest temperature vapor of oil burn continuously for at least five seconds when the standard flame is brought near the surface of the oil.
Choosing of oil for the engine will depend on above essential factors. It is important that the flashpoint should always be higher than the working temperature of the engine.
Different fluids Flash Point of various machines
- Lube Oil = 220°C
- Diesel Oil = 65°C
- Petrol = -20°C
- 70cSt Fuel Oil = 71°C.
- Paraffin = 40°C
Total Acid Number or TAN
The Total Acid Number is an assessment of acidity, which is decided by the measure of Potassium hydroxide in mg required to neutralize the acids in one gram of oil. In this process, quantities depletion, acidic pollution, and lubricating oil deterioration by oxidation are estimated.
TAN analysis is a quality analysis of crude oil and is referred to as a standard in Lubricating oil composition quality monitoring. This analysis is also used as an assessment of Lubricating oil deterioration.
The Total Acid Number value illustrates the probabilities of Corrosion issues. Therefore, TAN analysis is a must to monitor and conserve the equipment.
The weak organic acids and solid inorganic acids commenced in lubricating
oil will be indicated by Tan analysis assessment.
Higher TAN indicates the danger of component failure. lubricating oil oxidation due to prolonged use of oil/ higher operating temperatures will be indicated byincrease in TAN
Total Base Number or TBN Total Base
This is about the measure of acid, indicated in terms of the correspondent figure of mg. Of potassium hydroxide needed to neutralize all essential components available in 1 gram of specimen.
The control of acid effect during the combustion process is determined by the TBN. Higher TBN reduces acid corrosion by suspending wear, causing contaminants.
The Total Base number is a property related to the Machine oils. It is oil’s capability to nullify acid. Therefore, the higher the TBN value, the more the lube oil power negates the acid effects in lubricating oils.
The amount of TBN in new oils is found in the range of 5.0 to 15, depending upon the producer and the desired use. During the continuous use of oil, it gets polluted with acids resulting in a reduction of TBN value. Values lower than 3 TBN are considered dangerous and highly recommended for a replacement for the excellent fitness of the engine.
The cause of TBN depletion is the use of low-quality fuel with higher sulphur contents. Initially, in the engine operation, this sulphur turns into sulphurous acid, and with the prolonged continuation of the process, it gets converted into sulphuric acid. Overheating and prolonged oil replacement could cause oxidation.
Detergency and dispersancy
additives expedite the cleanliness of the mechanical parts in a machine. Omission of detergency and dispesancy in the combustion chamber, the lubricating oil accumulates are inhibited by detergent powder. The origin of deposits found in the engine is due to the following reasons.
2. Condition of combustion
3. Lubricating oil temperature
4. Temperature of coolant
5. Sealing of rings
These deposits will shorten the engine life exceedingly if the accumulated deposits are not withdrawn during the oil change.
Detergents assist in reducing the quantity of formed deposits and their easy extraction. The additives will pass on different detergent properties to oil depending upon the source of their orientation as high or low temperature.
Fuel combustion produces low-temperature deposits, and the detergent will keep them suspended in the oil. Conversely, an oxidized fraction of oil is the cause of high-temperature deposits. The detergents will not only keep the sediments suspended but will also stop the growth from orientation itself.
Cold filter filling point
The temperature at which crystallization of wax takes place is the cold filter filling point. There is no implication of this characteristic during the engine’s regular operation
The time ( in seconds) needed for the oil to separate from water under the condition of emulsification.
Combustion products in the lubricating oil are accelerated since the emulsification permits the water particles for the following undesirable reasons.
Lubricants will undergo degradation.
2. Will undergo Mechanical failures
3. Will result in Rust and corrosion
4. Foaming will be taking place.
General Guide Lines for the essential components of type-of-lubrication-in-marine-diesel-engine
A) Oil Testing. Oil testing is executed to authenticate the quality of oil supplied. In service, testing is performed to resolve the condition of oil. The test result will justify the type of oil maintenance needed, treatment, additives, and replacement in partial or complete quantity.
A single test result will never lead to a justified conclusion.
1. The test result certificate must be available during the receipt of the oil supply. If the certificate is not available, then the oil sample needs to be tested before the use of oil. However, it is good practice to get the sample tested for the new lot to cross-check and verify oil purity as per the specified data.
2. The sample report will predict the oil change or conditioning duration as per the engine manufacturer’s recommendation.
a) The oil sample must be analyzed regularly. The running hours since the last oil maintenance should be recorded in the logbook by the engine operator. The operator should maintain the accurate history of each engine separately.
b) Results of oil analysis will indicate the following predictions.
High iron level
Cylinder liner wear
Piston ring wear
Piston and /or bearing
Dirt due to damaged air intake filters
wear in bearings
If the quantity of all metals are excessive other than for silicone, this may indicate acid attack due to overcooling which can result from Low load or idle operation of the engine.
- Running the engine at no load:- Excessive carbon growth will occur in Engine Lube oil due to the increased acid under overcooled conditions. This phenomenon wills pre-pone the oil change intervals.
- Lube oil sample should be collected in a clean bottle. The sample should be taken while the engine in operation at average operating temperatures.
- Measure viscosity with the help of Visage.
- Monitor soot and residues using blotter test
- Monitor contaminants by centrifuge method.
- Measure the detergence capacity
Conclusion;- I hope the post on type-of-lubrication-in-marine-diesel-engine has been useful tothe readers.
Frequently asked Questions
What do you understand by the term Flash point and Fire point?
The lowest temperature at which vapors above a volatile combustible material ignite in air when brought near the flame is known as a flashpoint.
What is fire point?
The fire point of a fuel is generally defined as the temperature at which vapors will continue to burn for almost 5 seconds, and that too with open flame.
Which lubricating oil is to be used to minimize the cold corrosion in the engines using high sulfur fuel?
Using high TBN cylinder oil
Mixed lubrication consists of?
Hydrodynamic lube oil contamination.
What method is used is generally used to lubricate bearings in small high-speed engines?
Which type of pumps are used for the small marine engines taking suction from the engine sump?
Positive displacement type
what phenomenon is not a consequence of over lubrication of a cylinder liner?
Deposits in piston top land which can not only consume lube oil but always lead to increased abrasive wear
What will happen to the viscosity of engine oil If water contamination occurs in the crankcase oil of an auxiliary engine?
Will Increase the viscosity.-(Because Emulsification Increase the viscosity)
Why is it easier to maintain proper lubrication of a Single-acting four-stroke engine than the single acting two-stroke engine?
Due to the continuous reversal of lubricating oil pressure in single-acting four-stroke engines.
What action will you take if the oil’s viscosity is found high while testing the sample?
. Clean the oil system thoroughly and replace the oil.
Important marine Engineering Hand Books
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