Analysis of Fuel and Lube Oil Flashcards

Question

what are hydrocarbons and what are the 4 main series?

Answer 1

hydrocarbon is an organic chemical compound that is composed exclusively of hydrogen and carbon atoms. Hydrocarbons are naturally-occurring and form the basis of crude oil, natural gas, coal, and other important energy sources. The exact proportions and compositions decide the character of the petroleum as well as the refining processing equipment used. Hydrocarbons are made up of at least nine recognisable series, a series being a range of products with the same molecular structure pattern. The four main series are Paraffins Naphthenes Aromatics Olefines The first two are classed as saturated and the other two are unsaturated. Unsaturated series are rarely found in crude petroleum but can be found by molecular bonding alternation during later processing. olefines and naphthenes have the same C:H ratio and are distinguished by their difference in molecular structure. The lowest members of any series are gases, graduating to liquids as the molecular structure becomes more complex, thence to semi solids and to solids . For example , the paraffin hydrocarbon series methane to butane are gases, pentane to nonane, which are liquids of decreasing volatility. By octadecane there is a mineral jelly and further up the series lies paraffin wax solid. With slight deviations from the molecular grouping system, millions of different combinations called isomers are possible.

Answer 2

Density is the measurement of how tightly a material is packed together. It is defined as the mass per unit volume. Density Symbol: D or ρ Density Formula: ρ = m/V, where ρ is the density, m is the mass of the object and V is the volume of the object. density is related to temperature and If temperature cant be fixed at 15℃,like for instance with high viscosity oils, then a correction factor per ℃ above the 15℃ is added to the observed density, or if measured below 15℃ is subtracted from the observed density. Density is measured by a hydrometer. The datum temperature is 15℃ and the reciprocal of density is specific volume (m3 /kg). Density is important because when fuel is ordered by the weight and delivered by volume there's always a chance of the density being incorrect. Density is also proportional to the energy extracted, therefore there will be a reduction in performance if density is lowered. Marine fuel density meter are available on-board. On-board test equipment also measure the CCAI (calculated carbon aromaticity index) for residual fuel oil . Mass flow meters are also installed which measure incoming bunker fuel coming on-board.

Answer 3

a.) Defined as the resistance flow rate of a fluid. Fluid changes flow rate and shape due to internal molecular friction of molecule against molecule of the fluid, which produces a frictional drag effect. Increase in temperature has the effect of reducing viscosity. To achieve correct atomization of fuel you have to heat up the fuel that has high viscosity to reduce viscosity to about 20cSt at the fuel injector and about 13cSt for internal combustion common rail engine system. The viscosity of diesel oil is about 7cSt at 38℃.When providing a value for viscosity you have to also quote temperature otherwise value is meaningless for comparison. Scale readings between viscometers can be related to each other by graphs or the use of constants. Its not possible to calculate viscosities at different temperature without using a viscosity temperature curve. Each oil and blend type is different with the effect of temperature change so a curve is required for each type. Sulphur content is falling dramatically due to pressure being put on the industry to reduce atmospheric pollution. b.) Absolute (dynamic) viscosity is used for calculations is difficult to determine due to it being numerically equal to that force to shear a plane fluid surface of area 1m2, over another plane surface at the rate of 1m/s. when the distance between the the two surfaces is 1m. c.) Kinematic viscosity is the ratio of absolute velocity to the density at the temperature of the viscosity measurement. Kinematic method is chosen to determine values in the ISO fuel specification. viscosity is expressed in centistokes (cSt) or mm2/s. Kinematic viscosity is expressed in centipoise (cP) and measured by a capillary flow of a set liquid volume from a fixed head. For practical purposes viscosity is measured on on a time basis. Its measured as the number of seconds for the outflow of a fixed quantity of fluid through a specifically calibrated instrument at a specified temperature. Temperature accuracy is vital , a variation of + or - 0.1℃ is a maximum for temperatures up to 60℃.

Answer 4

The International Standards Organization (ISO) sets classifications for marine fuels that are supplied on a world-wide basis (Marine fuels are specifically covered under ISO 8216 and 8217).

Answer 5

Viscometer is an instrument used for measuring the viscosity of a fluid. In the capillary tube viscometer, the pressure needed to force the fluid to flow at a specified rate through a narrow tube is measured. Capillary U tube viscometer can be used. The oil is raised to start position by a suction applied at the top of the right hand section of the tube. As this position is reached the suction is released and the oil is left to fall through the capillary under its own weight. Time is measured from the start point until oil level reaches the end point

Answer 6

Factors that are influenced by viscosity frictional drag effect, pipe flow losses, fouling factor frictional drag is caused by the friction of a fluid against the surface of an object that is moving through it. also Fluid changes flow rate and shape due to internal molecular friction of molecule against molecule of the fluid, which produces a frictional drag effect pipe flow loses refer to when a liquid or gas flows along a pipe, friction between the pipe wall and the liquid or gas causes a pressure or head loss. This pressure or head loss is an irreversible loss of the fluids potential energy. Calculating this loss is fundamental to the design of any pipeline system. fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger

Answer 7

Viscosity index A numerical value that measures the ability of an oil to resist viscosity change when temperature changes. High viscosity index refers to oil that is capable of maintaining a fairly constant viscosity value despite wide variations in temperature. Value of viscosity index is determined from a chart based on knowledge of viscosity values at different temperature. On-board a ship viscosity index is important for deck equipment, emergency generators and lifeboat engines. These may be required to be operated at large range temperatures during winter months.

Answer 8

Restricting the sulphur in marine fuel oil and meeting its obligations is important for restricting air pollution. Problem is that the very low sulphur option for use in emission control areas (ECA) is only available in diesel oil, which is more expensive than residual fuel oil and in short supply. Another problem is specification for marine diesel is basically the same as for automotive diesel but flashpoint is different , 60 for marine and 55 for automotive, there would also need to be a change in SOLAS for the maritime industry to have access to wider availability of automotive diesel. The limits on sulphur is to reduce SOx and particulate matter from the emissions of power plants on ships. Annex VI regulation 4 allows flag administration to use alternative methods of compliance with exhaust emission limits

Answer 9

Bunkers should be ordered to the most up to date specification and checks made that fuel delivery is in accordance with specifications. DMX and DMA are considered as representatives of marine gas oil (MGO), while DMB and DMC are representatives of marine diesel oil (MDO). Residual fuel products are as follows: RMA and RMB are fuels for use at low ambient temperature, they have a low pour point and wouldn’t necessarily require heat in storage tanks; RMD, RME and RMG are fuel requiring a standard treatment plant; RMK is very heavy residual fuel oil that requires a special treatment plant to handle such fuels. DMX is the low sulphur product fuel used in ECAs. A general rule is the heavier the oil the higher the viscosity and flashpoint and the lower the calorific value.

Answer 10

Octane number This is indicative of the knock rating. Knocking or pinking are characteristics of some IC engine fuels , particularly in spark ignition engines. It can cause pre-ignition, overheat and damage. Normally on spark initiation the flame front proceeds through the mixture at a speed of about 18m/s. if, due to engine conditions or type of fuel used, the mixture in the front of the flame front has its temperature and pressure raised above the spontaneous ignition point the auto ignition occurs. By the time the last gas charge is reached the flame front speeds can reach 2.2km/s and detonation, temperature rise and heavy shock waves occur. Knocking tendency is dependant on many variables such as revs/s, compression ratio, turbulence, mixture strength and if a hot spot has developed due to a build up of carbon. Cetane number Indication of the ignition quality of diesel oil with CCAI being the measure applied to residual fuels. In a compression ignition engine, cold starting is often required, here the time interval between fuel injection and firing, called ignition delay, must not be too long otherwise collected fuel will generate high pressure when it ignites and diesel knock results. Paraffin hydrocarbons have the best ignition quality and are therefore more suitable. Speed and Cetane number can be correlated for high speed engines (above 13revs/s) cetane number of 48 can be regarded as a minimum, ISO sets 35 as minimum for diesel oil. Diesel fuel used in hot petrol engine would cause detonation, that is it has a low octane number. Cetane is a paraffin hydrocarbon, hexadecane being its correct designation, of high ignition quality and is taken as the upper limit of 100. Alpha-methyl-napthalene is of low ignition quality and is taken as the lower limit of zero. Cetane number is numerically the percentage by volume of cetane in a mixture of cetane and alpha-methyl-napthalene that matches the chosen fuel in ignition quality Crankcase oil dilution This is the percentage of fuel contamination of lube oil occurring in IC engines, which can reduce the lubricity of oil. The lubricating oil sample is mixed with water and heated, and fuel volatiles are carried over when steam vapour is formed. By condensation of these vapours and separation, the fuel content can be measured and can be expressed as a percentage of the original lube oil sample by mass. Its important to check the lube oil for water contamination and for this another separation test with heating is carried out. Severe corrosion of crankshafts has been caused by sulphur products from fuel oil mixing with any water in lube oil which forms sulphuric acid, which is then carried around the lube oil system.

Answer 11

octane number Test Iso-octane has very good anti-knock properties and is taken as upper limit 100. Normal heptane has very poor anti-knock properties and is taken as lower limit zero. Therefore octane number is the percentage by volume of iso-octane in a mixture of iso-octane and normal heptane, which has the same knock characteristics as the chosen fuel. The test is conducted under fixed conditions on a standard engine, which usually has electronic detonation detection. The octane rating does not equate to the energy content of the fuel, it is only a measure of its tendency to burn n a controlled way at the lower end or explode uncontrollably at the higher end. cetane number test Test One test is done by measurement of delay period when running, by use of a cathode ray tube on a standard engine. Another test, this being the most used, is to use a standard engine running under fixed conditions with a variable compression ratio to give a standard delay, and using the compression ratio as an indication of a cetane number. One alternative test, called diesel index, is used but isn't as reliable. Density is often indicative of cetane number especially in the middle ranges. For instance the cetane number for density of 850kg/m3 is about 61. some success has been achieved by using additives such as acetone peroxide.

Answer 12

a.) Neutralisation number is the mass, in milligrammes, of an alkali, which is often potassium hydroxide, needed to neutralise acid in 1g of sample. b.) Ash is expressed as a mass percentage of the original sample and usually consists of hard abrasive mineral particles, such as quartz, silicates, iron and aluminium oxides and sand. A residue test (% by volume after heating to 350℃) is sometimes used. Sodium can enter the fuel due to it being in a marine environment but the ISO sets the maximum standards allowed for fuel and sets limits for bunker fuel. Vanadium is present in all crude oil but but the amount varies depending upon the source of the crude oil. Vanadium is very hard and can have an abrasive and corrosive effect on the engine.

Answer 13

CCAI is a measure of the ignition quality of marine fuel. It is a calculated parameter that is used to predict the combustion performance of heavy fuel oils in marine diesel engines. The CCAI is calculated based on the density and viscosity of the fuel, as well as its carbon and hydrogen content, and it provides an indication of how easily the fuel will ignite and burn in a diesel engine. A lower CCAI value generally indicates a better ignition quality and more efficient combustion of the fuel. Combustion of residual fuel is a combination of efficiency and effectiveness of the injection system on the IC engines, burner on oil fired boilers and ignition quality of fuel. The modern refining process uses a combination of techniques to extract lighter products for crude oil. This process produces fuels that are unstable. One problem that occurs from this process is an increase in aromatic compounds found in residual fuel. These compounds have high resistance to auto ignition. When the level of aromatic compounds in bunker fuel reaches high enough the fuel will not auto ignite at the temperature of the compressed air in diesel engines. The ISO 8217 specification sets the CCAI for residual fuel at 870, this is important for engineer to know. Combustion is the rapid oxidisation of fuel that results in the release of heat but the ratio of air to fuel and ignition temperature all have to be correct for when fuel is introduced into combustion space. When fuel is introduced into combustion space there is a time lag until the conditions are correct for start of oxidisation process. If this time lag is too long or in other words there is a long ignition delay then a large amount of unburnt air to fuel mixture will build up before initial combustion takes place. The next combustion stage is controlled by how rapidly the oxygen and remaining vaporised fuel can be mixed as the initial supply of oxygen close to the fuel droplets boundary has been used in the first stage of combustion. If combustion stages occur to quickly than very rapid rates of pressure rise in the cylinder and a shock waves are transmitted which cause damage to piston rings and there is overheating of metal surfaces.

Answer 14

A quick test for presence of water in a substance is to add a sample to white copper sulphate, which will turn to blue copper sulphate when water is present. The test conducted is called the LP (laboratory procedure) standard method. In this test 100ml of sample is mixed completely with 100ml of special high grade gasoline. Steady heat is applied for an 1hour. Water vapours will then carry over with the distilled gasoline and be condensed in the condenser and measured in the lower part of the receiver. The result being expressed as for example 1% water IP method. The test must also be carried out under closely controlled conditions. ISO 8217:2010 set the maximum water content in the fuel at 0.5% by volume for residual fuel and 0.3% for diesel oil. Water content is generally much lower, however this doesn’t change the fact that engineers should be checking for water in the fuel and carrying out standard on-board practices so that in case there is water in the fuel its being removed before it enters the engine. If water is found in fuel then you have to check all possible sources because that water hasn’t necessarily come from bunker tanks it could be from malfunctioning purifier or it could be because steam heating coil inside tank is broken.

Answer 15

This is a test that indicates the relative carbon forming propensity of an oil. It finds out the residual carbon, when oil is burned under certain conditions. The test is used often for high viscosity fuels in IC engines. Its preformed using a Conradson carbon test apparatus. The mass of the sample placed in the silica crucible must not exceed 0.01kg. Initial heating period 10minutes + or - 1.5, vapour burn of period 13mins + or - 1, further heating for exactly 7mins, total heating period 30mins + or - 2. the cover has to be a loose fit to allow vapour to escape. After removal of sample and weighing, the result is expressed as carbon residue (Conradson) as a percentage of the original sample mass. Test has to be repeated several times to obtain a uniformity of results.

Answer 16

This is a determination of the lowest temperature value at which oil will pour or flow under certain test conditions. This value is important of lube oils working under low temperature conditions, for example in refrigeration, machine lubricants and telemotors. A pour point apparatus is used for the test and various mixtures. For very low temperatures solid carbon dioxide and acetone are used. At 11℃ above the expected pour point the test is started. At temperature intervals of 3℃ the test jar is removed, check for surface oil tilt and replaced in a time interval of 3secs maximum. When the surface oil wont tilt, for a time interval of 5secs, check temperature, add 3℃ and this is the pour point. The oil is heated to 46℃ before the test and cooled in progressive stages of about 17℃ in different cooling agent baths: in each case the jar must be transferred to another bath when the oil temperature reaches 28℃ above the bath temperature. The pour point is also important for fuel oil as this lowest temperature at which the fuel can be stored and used without the formation of wax. If a fuel is below the pour point, the wax will build up on tank bottoms and heating coils. If fuel is used in this condition the wax will also block the fuel filters, making fuel transfer between bunker tank to settling service tank impossible. Depending on where in the fuel system the wax forms it can also stop a running engine. When fuel is heated up again the wax will not re-dissolve because of its insulating nature, therefore manual cleaning of tanks and all affected machinery and components will have to be carried out. To avoid this the fuel temperature has to be kept 10℃ above the pour point. The pour point for residual fuel oils is a maximum of 40℃. This in line with the best industry practice of between 45 and 50. fuel transfer pumps are designed to operate at a maximum viscosity of 800 - 1000mm2/s. The fuel should be between 45 and 50 so its at correct viscosity for efficient transfer. For less viscous fuels, like RMA 10 and RMB 30, the pour point value is important for handling purposes especially if tank heating isn't available.

Answer 17

Its the amount of heat energy released during complete combustion of a unit mass of a fuel. This is a value for the complete combustion of unit mass of fuel expressed MJ/kg, kJ/kg,. High calorific value include the heat in water vapour formed from water as the products of combustion are cooled, vapours condensed and so latent heat is available again for heat utilisation. The low calorific value is more realistic because it’s the actual heat available for boiler water evaporation but this is due to fault of utilisation so the high calorific value is the actual heat available so it’s the value that normally used for quotation. Fuel will always experience a decrease in calorific value to an extent when in storage.

Answer 18

Oil characteristics relating to closed flash point Oils with flash point below 22℃ are classified as dangerous and highly flammable, these oil can include oil types like gasoline's or benzenes. Flash points in the range of 22-66℃ are kerosenes and vaporising oils. Flash points above 60℃ are classified as safe and include gas, diesel and fuel oils

Answer 19

This is the minimum temperature at which oil gives off flammable vapour, which when refereed to the application of a flame in a specified apparatus would cause momentary ignition. Test is carried out open or closed depending upon whether the apparatus is sealed or not. Closed flash point is always lower due to the lid seal allowing accumulation of volatiles above liquid surface. Test applied for oils above 45℃ is the pesky marten closed flash point test. For oils below 45℃ the Abel apparatus is used. When the operating handle is depressed for the pesky martens test, the shutter uncovers the ports. Down movement of the handle opens a shutter just below the ports through the use of a ratchet, any further movement and ratchet travel gives a flame insertion. The flame element is depressed through one port above the oil surface. Starting at a temperature of 17℃ below the judged flash point, the flame is depressed, left and quickly raised in a period of under 2secs, at 1℃ temperature intervals. Just before flash point is reached a blue halo occurs around the flame, the flash is observed just after, through the two observation ports, stirring being discontinued during flame depression. A fresh sample must be used for every test and care should be taken so that there's no trace of cleaning solvents present in oil cup. SOLAS states that fuel on-board ship must be a minimum of 60℃.SOLAS chapter 2 regulation 4 sets out the basic fuel requirements for main engine and auxiliary engine. It also states that fuel with a minimum flash point of 43℃ can be used for emergency generator as long as there's no reserve in machinery space. Oil in storage should not heated be above 52℃and should also not be stored in temperature range of 15 an 40℃because this promotes bacterial growth and degrades the oil. When high viscosity oil is used and degree of heating in necessary for atomisation its possible to heat the oil to within 20℃ of closed flash point. Ensure to control the heat going to the heater, which are located on the suction side of fuel pumps in order not to cause oil vaporisation and the possibility of explosive vapour formation. Any vaporisation also causes pumps to lose suction and stop pumping.

Answer 20

Separate entirely the contact surfaces, thereby reducing static and dynamic friction to least possible value to prevent wear and tear. Remove heat generated within the bearing. Protection of the working surfaces against corrosion. Removal of contaminants. Dampen noise produced. Act as a sealant.

Answer 21

Hydrodynamic Lubrication or Full fluid film lubrication. Boundary Lubrication or Thin film lubrication. Hydrostatic Lubrication or Thick film lubrication. Elasto-hydrodynamic Lubrication or Thin film or square film lubrication.

Answer 22

Viscosity: To be suitable for the purpose Viscosity index: To be high Pour Point: Must be low Flash point: Must be high Oxidation stability: To be high Carbon residues: To be low Total acid number or TAN: To be suitable for the purpose Total basic number or TBN: To be suitable for the purpose Detergency: For cleaning Dispersancy: To facilitate purification

Answer 23

For cylinder oil, viscosity is 12.5 – 22 Cst

Answer 24

It is the rate of change of viscosity of an oil with respect to change in temperature. An oil with low viscosity index has greater change of viscosity with change in temperature. An oil with high viscosity index has very little change of viscosity with change in temperature, which is a desirable property for lubricating oil. For crankcase oil, viscosity index is 75 to 85. For cylinder oil, viscosity index is 85. Viscosity index of mineral oils is highest, about 115 and this may be raised to about 160 by adding special additives. Hydraulic oils should have high viscosity index for faster response of the system. It is usually around 110.

Answer 25

It is the lowest temperature below which an oil will stop flow. Pour point indicates that oil is suitable for cold weather or not. Pour point of engine crankcase should be -18°C.

Answer 26

It is the lowest temperature at which the oil will give off a sufficient inflammable vapour to produce a momentary flash when a small flame is brought into the surface of the oil. Close flash point for crankcase lubricating oil is around 220°C. Why flash point is important?

Answer 27

Fuel oil flash point is to be high because if it is low, there would be a possibility of fire in storage. Engine crankcase lubricating oil flash point should be as high as possible to prevent crankcase explosion. For safe storage, oil storage tank heating temperature to be limited to at least 14°C lower than flash point to prevent fire.

Answer 28

The ability of an oil to react with a base reagent which indicates the acidity is expressed as TAN. The ability of an oil to react with acidic reagent which indicate the alkalinity is expressed as TBN. The results are expressed in milligrams of potassium hydroxide (KOH) required to neutralise one gram of sample oil for both TAN and TBN. TBN for an oil used for cross head type diesel engine crankcase is 8mg KOH/gram of oil. TBN for an oil used for trunk type engine using heavy oil is 30mg KOH/gram of oil.

Answer 29

If blow pass occur in a trunk type engine using heavy fuel oil, incomplete combustion products reach directly into the crankcase and may cause the contamination of lube oil with acid. Thus in this type of engine to neutralize the acid contamination must be used high TBN oil.

Answer 30

It is a chemical additive called detergent which has a property of preventing the deposition of carbon deposits and wash away with the lube oil. Dispersant additive is added to divide the larger size deposits into tiny particles to be carried in a colloidal suspension evenly throughout the bulk of oil, which can be removed while filtration of the oil.

Answer 31

The sample should be drawn with oil circulation with the system such as a test cock on the discharge side of the LO oil pump. Before taking the sample oil sufficient amount of oil should be drain out to clear the line. The sample is filled into the chemically cleaned container after it is rinsed with the sample oil and immediately closed. The container should be attached with information on engine type, engine running hours, LO running hours, fuel used, draw off point and date of sampling.

Answer 32

Draw samples from a connection that comes directly out of the main oil supply line to the engine. Always sample for the same point. Sample only when the oil is up to its operating temperature with the engine running. Depending upon the draw off point, sufficient amount of oil should be drained out of the line prior to drawing the sample. The sample should be filled into a chemically cleaned container after it is rinsed with sample oil and immediately closed. The container should be attached with a label as follows: Records for Sample Date of sample drawn Point of sample drawn Type of oil Type of machinery use Temperature of sample drawn The period of time since the last renewal of oils. Avoid sampling from places where the oil may be stagnant or have little or no flow, such as sumps, auxiliary smaller pipelines, purifier suction or discharge lines, drain cocks of filters, coolers etc. Also avoid sampling while engine is stopped.

Answer 33

Viscosity of lube oil Load acting on the bearing Surface smoothness of moving parts Speed of rotation Continuous LO supply Bearing clearance, bearing length and pin diameter. There must be convergence between fixed end and moving surface.

Answer 34

To prevent pump damage due to ferrous metal particles. Screw p/p used in LO oil system is working in very fine clearance thus to prevent entering the small ferrous particles into the p/p. Magnetic fitter is fitted prior to the main circulation LO p/p.

Answer 35

Contamination of fresh Water (JW leaking) Contamination of SW (Cooler leakage) Contamination of fuel (Poor Atomisation, Unburned Fuel) Oxidation products (High Exhaust Temperature, Burned Cyl Oil, Carbon from incomplete combustion) Products of fuel combustion Foreign mineral matters (Scale formation, Wear and tear) Biological contamination.

Answer 36

Causes Condensation of water vapour within the crankcase Leakage from the cooling water system for cylinder or piston Leakage from the sump tank heating steam coils. Effects Reduce cooling efficiency. Increase the acid formation in trunk type piston engine. Can cause corrosion on m/c parts. Microbial degradation, [Reduce centrifuging efficiency; promote local pitting and corrosion] Reduce load carrying capacity Reduce L.O properties, and TBN of oil Form sludge due to emulsification

Answer 37

Cause Poor atomization of a fuel injector and back leak through the fuel injector p/p plunger and barrel. Effects Fuel dilution usually diesel oil. Lower viscosity and low fresh point Lower viscosity LO reduces this properties ( e.g load carrying capacity ) Lower fresh point will case crankcase explosion.

Answer 38

Filtering: Removes large oil insoluble matter Gravity separation: Removes heavy matters, sludge and water Adding special additives: Reduce acids, sludge, finer oil insoluble matter Centrifuging: Removes sludge, foreign matter and water Water washing: Only for straight mineral oil or oil without additives, can remove acids.

Answer 39

Batch Purification must be done Renovating Tank heating and regular draining For SW contamination, Water Washing is required Sump to be opened and thoroughly wipe out.

Answer 40

Batch purification refers to the process where the engine is shut down and the whole of sump lube oil charge is pumped up to the dirty lube oil tank in the upper part of the engine room. The lube oil is heated in the tank and left as long as possible to settle out solids, sludges and any water. Procedure: Firstly take the immobilization permit from the port authority. The entire oil charge should be pumped by the purifier or by main circulation p/p into settling tank. It should be allowed to settle for at least for 24 hours with heating about 60° C . Water and sludge should be drained out periodically. Cleaned the interior of the sump tank and carefully examined. The oil should be passed through the purifier at its optimum efficiency and than pump back into the sump tank. When sump tank empty, its interior should be cleaned and examined.

Answer 41

If the oil is suspected from containing strong acids High insoluble contents due to poor combustion or water due to leak cooling system. It is also made at least once a year when cleaned and examined for sump tank. Suspecting biological contamination.

Answer 42

The cylinder oil is feed to the piston at the time when the top two piston rings pass the lubrication holes in the cylinder during the piston stroke.

Answer 43

It is a semisolid lubricant consisting of high viscosity mineral oil and metallic soap with filler. Metallic soaps are compound of Ca, Na, Al. Filler are lead, zinc, graphite and molybdenum.

Answer 44

Grease lubrication is known as solid lubrication

Answer 45

The oil can not flow freely and so this effects delivery rate

Answer 46

Low viscosity is required for fuel oil in order to obtain good atomization of fuel. Lube oil must be chosen which has a suitable viscosity for the working temperature for efficient lubrication.

Answer 47

L.O onboard test is carried out regularly. Regular cleaned L.O line filter. L.O purifier should be run during ship is in sea Maintain L.O purifier performance Periodic batch purification must be carried out & cleaned L.O sump tank once a year Maintain L.O temperature within limit Maintain good L.O cooler efficiency

Answer 48

It is more effective to filter the hot oil, as pressure drop through the filter is less and filter is more efficient.

Answer 49

Moving surfaces are separated completely by the pressure of a continuous unbroken film or a layer of lubricant, generated by the movement of the two surfaces relative to each other. Essential requirement is formation of a wedge of lubricants between surfaces. Thickness of film 0.025 – 0.10 mm. Happens in lubrication for Journal Bearing, Bottom End Bearing, Tilting Pad Thrust Bearing

Answer 50

It exists when a full-fluid film lubrication is not possible. The sliding surfaces are separated by only a thin film of lubricant. High friction between the surfaces and some degree of metal to metal contact occurs Lubricant oil film decreases, until asperities of mating surfaces touch

Answer 51

A form of thick film lubrication, but instead of being self- generated, it is supplied from an external source by oil under pressure from a pump.

Answer 52

Applies to line contact or nominal point between rolling or sliding surfaces, such as rolling contact bearings and meshing gear teeth. Thin film or squeeze film lubrication limits metal to metal contact. Elastic deformation of the metals occurs, and there is effect of high pressure on the lubricant.

Answer 53

Cylinder oil is detergent / dispersant oil System oil is straight mineral oil

Answer 54

Viscosity Determination The simplest method is three tube rolling ball viscometer Assuming the oil in the engine to be SAE 30 grade, one tube is filled with minimum safety viscosity (about SAE 20) and another one filled with maximum safety viscosity (about SAE 40). The last tube is to be filled with test sample. All tubes are placed in a bucket of warm water until the oils are at the same temperature. The three tubes then mounted on a tilted board and inverted. An internal hollow ball in each tube then rises to the surface. If the time taken in the test sample is between that of the lower and upper limit oils, the oil is fit for further use. If not, it must be replaced. Insoluble Content A drop of sample oil is released from a given height onto a special filter paper. Compare the result with the known varying insoluble content. The upper limit for straight mineral oil is 1% to 1.5 % and for detergent dispersant oil is 5%. Water and other Contaminants A known amount of sample oil in the test tube is heated and must be shaken the while doing so If there is no cracking, the oil is dry If there is slightly cracking, the oil having a trace of water If there is a heavily crackling, the oil is heavily diluted with water Acidity / Alkalinity Determination Acidity is tested by extracting the acids from the sample by means of shaking with a known amount of distilled water. The acidic extract is then placed on a watch glass with an indicator solution of known strength. The mixture is then drawn up into a glass tube and its colour compared with a series of colour standards, each representing a known PH value, from which the sample can be determined quite accurately. Another method is : A drop of indicator solution is placed on to blotting paper and this is followed by a drop of sample oil placed at the centre of the drop of previous absorbed indicator. If the change of colour is Red, it is acid If blue/green, it is alkaline. If yellow/green, it is neutral. Foreign Particles Test This can be done by either Spectrochemical analysis or Ferrographic analysis, each giving particle size less than 10 uM to 100 uM range depending on the tests applied. The most powerful technique is Inductively coupled plasma atomic emission spectrometry (ICP OR PES), which uses a direct spray technique to determine the wear and contaminant elements present in the oil. This technique will in the main only detect the particles below 10 uM size. In ferrographic test, the sample is thinned first with some solvents and allowed to pass slowly down a slide surrounded by powerful magnetic field. Then it is examined by special microscope with red and green filters under lights. The shape of the particles is used to identify the source of the wear debris. The advance ferrography method was added to the PFA (Progressive Fast Analysis) programme where all samples pass through the combination of two machines, a particle quantifier (PQ) and a rotary particle depositor (RPD). These test measures the induced magnetic moment of debris as deposited on a substrate or contained within a specific volume of liquid. These machines provide accurate test by rotating the metal particles and then separating into three different sizes, Theses three bands of particles are examined by very powerful microscope to determine the type of materials and shape. If more detailed examination is necessary, the debris may be subjected to a scanning electron microscope.

Answer 55

Crude oil is, at the present time, the source of most fuel oils for marine use. Synthetic fuels are being developed but will probably be too expensive for ship propulsion. Solid fuel, such as coal, is returning in a small way for certain specialised trade runs. The various refined products of crude oil seem likely to remain as the major forms of marine fuel. The refining process for crude oil separates by heating and distillation the various fractions of the oil. Paraffin fuel would be used in gas turbine plants, gas oil in high- and medium-speed diesel engines and crude oils in slow-speed and some medium-speed diesels. Paraffin and gas oil are known as 'distillates', which are free flowing, easily stored and can be used without further treatment. Residual fuels, however, are very viscous or thick at normal temperatures, and require heating before use. Additional treatment to remove harmful chemicals or sulphur may be required for all or some of the refined products, depending upon their application. Finally blending or mixing of the various oils is done to provide a range of commercial fuels for different duties

Answer 56

- The specific gravity or relative density is the weight of a given volume of fuel compared to the weight of the same volume of water expressed as a ratio, and measured at a fixed temperature. - The ignition quality of a fuel is measured by the time delay between injection and combustion, which should be short for good controlled burning. Ignition quality is indicated as cetane number, diesel index and calculated cetane index; the higher the value the better the ignition quality of the fuel. - The flash point is a figure obtained and used mainly to indicate the maximum safe storage temperature. The test determines the temperature at which the fuel will give off sufficient vapours to ignite when a flame is applied. Two values are possible: an open flash point for atmospheric heating, and a closed flash point when the fuel is covered while heating. - Low-temperature properties are measured in terms of pour point and cloud point. The pour point is slightly above the temperature at which the fuel just flows under its own weight. It is the lowest temperature at which the fuel can be easily handled. At the cloud point waxes will form in the fuel. Below the cloud point temperature, pipe or filter blocking may occur. - The carbon residue forming property of a fuel is usually measured by the Conradson method. Controlled burning of a fuel sample gives a measure of the residual carbon and other remains. Sulphur content is of importance since it is considered a cause of engine wear. A maximum limit, expressed as a percentage by weight, is usually included in specifications. - The calorific value of a fuel is the heat energy released during combustion. Two values are used, the more common being the Higher Calorific Value, which is the heat energy resulting from combustion. The Lower Calorific Value is a measure of the heat energy available and does not include the heat energy contained in steam produced during combustion but passing away as exhaust. The measurement is obtained from a bomb calorimeter test where a small fuel quantity is burnt under controlled conditions. - The various fuel properties have different effects on performance of the engine and the storage and handling requirements of the system. Blending and the use of various additives will also influence both the engine and the system. Viscosity will affect jerk-type injector pumps and injector operation since the liquid fuel is the operating medium. The pump mechanism is lubricated by the fuel which, if it is of low viscosity, will cause wear. - Cloud point and pour point values are important when considering the lowest system operating temperatures. Wax deposited in filters and fuel lines will cause blockages and may restrict fuel flow to the engine. - The cetane number or diesel index will determine injection timing and also influences the combustion noise and production of black smoke. The temperature in a fuel system should be progressively increased in order to deliver fuel at the correct viscosity to the injectors or burners. System cleanliness is also very important to reduce wear on the many finely machined parts in the fuel injection equipment. Regular attention to filters and general system cleanliness is essential. Various additives are used to, for instance, remove lacquer from metal surfaces, reduce wear and prevent rust.

Answer 57

The important lubricant properties will now be examined. Viscosity is an important property of lubricating oils. Viscosity index is also used, which is the rate of change of viscosity with temperature. The Total Base Number (TEN) is an indication of the quantity of alkali, i.e. base, which is available in a lubricating oil to neutralise acids. The acidity of an oil must be monitored to avoid machinery damage and neutralisation number is used as the unit of measurement. The oxidation resistance of a lubricant can also be measured by neutralisation number. When excessively oxidised an oil must be discarded. The carbon-forming tendency of a lubricating oil must be known, particularly for oils exposed to heat. A carbon residue test is usually performed to obtain a percentage value. The demulsibility of an oil refers to its ability to mix with water and then release the water in a centrifuge. This property is also related to the tendency to form sludge. Corrosion inhibition relates to the oil's ability to protect a surface when water is present in the oil. This is important where oils can be contaminated by fresh or salt water leaks. The modern lubricant must be capable of performing numerous duties. This is achieved through blending and additives. It must prevent metal-to-metal contact and reduce friction and wear at moving parts. The oil must be stable and not break down or form carbon when exposed to high temperatures, such as where oil cooling is used. Any contaminants, such as acidic products of combustion, must be neutralised by alkaline additives; any carbon build up on surfaces must be washed away by detergent additives and held in suspension by a dispersant additive. The oil must also be able to absorb water and then release it during purification, but meanwhile still protect the metal parts from corrosion. The various types of engine and other equipment will have oils developed to meet their particular duties. Trunk piston engine lubricating oil must lubricate the cylinders as well as the crankcase: some contamination from the products of combustion will therefore occur, resulting in acidity and carbon deposits. The oil must, in addition to lubricating, neutralise the acids and absorb the deposits. Turbine oil, while lubricating the moving parts, must also carry away considerable quantities of heat from the bearings. This calls for a stable oil which will not break down at high temperatures or form deposits. Where gearbox lubrication is also required certain extreme pressure (EP) additives will be needed to assist the lubricating film. Contact with water in the form of steam will be inevitable so good demulsifying properties will be essential. Slow-speed diesel engines will have separate cylinder and crankcase lubrication systems. The cylinder oil will have to neutralise the acidic products of combustion and also have good detergent properties to keep the metal, surfaces clean. Crankcase oils are either detergent type, multi-purpose oils or rust and oxidation inhibited. Good demulsification and anti-corrosive properties are required together with oxidation resistance which is provided by the inhibited crankcase oil. The detergent or multi-purpose oil is particularly useful where oil cooling of pistons occurs or where contamination by combustion products is possible

Answer 58

Both fuel oils and lubricating oils require treatment before passing to the engine. This will involve storage and heating to allow separation of water present, coarse and fine filtering to remove solid particles and also centrifuging. The centrifugal separator is used to separate two liquids, for example oil and water, or a liquid and solids as in contaminated oil. Separation is speeded up by the use of a centrifuge and can be arranged as a continuous process. Where a centrifuge is arranged to separate two liquids, it is known as a 'purifier'. Where a centrifuge is arranged to separate impurities and small amounts of water from oil it is known as a 'clarifier'. The separation of impurities and water from fuel oil is essential for good combustion. The removal of contaminating impurities from lubricating oil will reduce engine wear and possible breakdowns. The centrifuging of all but the most pure clean oils is therefore an absolute necessity.

Answer 59

A homogeniser is used to create a stable oil and water emulsion which can be burnt in a boiler or diesel engine. Such an emulsion is considered to bring about more efficient combustion and also reduce solid emissions in the exhaust gas Various designs utilise an impact or rolling action to break down the fuel particles and mix them with the water. It is also considered that agglomerates of asphaltenes and bituminous matter are broken down and can therefore be burnt. The manufacturers contend that a homogeniser can render a sludge burnable whereas a centrifuge would remove such material. Homogenisers are able to reduce catalytic fines into finely ground particles which will do no harm. Shipboard experience with homogenisers is limited and generally not favourable. Most authorities consider it better to remove water and solid contaminants than simply grind them down

Answer 60

Blending is the mixing of two fuels, usually a heavy fuel and marine diesel oil. The intention is to produce an intermediate-viscosity fuel suitable for use in auxiliary diesels. The fuel cost savings for intermediate fuel grades are sufficient to justify the cost of the blending plant. Furthermore no supply problems exist since the appropriate mixture can be produced by the blender from available heavy and marine diesel oils. The blending unit thoroughly mixes the two fuels in the appropriate proportions before supplying it to a blended fuel supply tank. Compatibility can be a problem and tests should be conducted on any new fuel before it is used. Incompatible fuels may produce sludge or sediment. The cracked residues presently supplied from many refineries are very prone to incompatibility problems when blended with marine diesel oil.

Answer 61

Mechanical separation of solid contaminants from oil systems (fuel and lubricating) is achieved by the use of filters and strainers. A strainer is usually a coarse filter to remove the larger contaminating particles. Both are arranged as full flow units, usually mounted in pairs (duplex) with one as a standby. The strainer usually employs a mesh screen, an assembly of closely packed metal plates or wire coils which effectively block all but the smallest particles. It is usually fitted on the suction side of a pump and must be cleaned regularly or when the pressure differential across it become unacceptable. Where suction conditions are critical the strainer will be fitted on the discharge side of the pump. When cleaning is undertaken the other unit will be connected into the system by changeover valves or levers and oil circulation will continue. The particles of dirt collect on the outside of the strainer element or basket and can be removed by compressed air or brushing. A strainer should be cleaned as soon as it is taken out of the system, then reassembled and left ready for use. Magnetic strainers are often used in lubricating oil systems, where a large permanent magnet collects any ferrous particles which are circulating in the system. The magnet is surrounded by a cage or basket to simplify cleaning. Fine filters, again in pairs, are used to remove the smallest particles of dirt from oil before the oil enters the finely machined engine parts in either the fuel injection system or the bearings of the rotating machinery. Fine filters are full-flow units which clean all the oil supplied to the engine. The filtering substance may be a natural or synthetic fibrous woollen felt or paper.

Answer 62

Minute micro-organisms, i.e. bacteria, can exist in lubricating oils and fuel oils. Under suitable conditions they can grow and multiply at phenomenal rates. Their presence leads to the formation of acids and sludge, metal staining, deposits and serious corrosion. The presence of slime and the smell of rotten eggs (hydrogen sulphide) indicates a contaminated system. Water in a lubricating oil or fuel oil, oxygen and appropriate temperature conditions will result in the growth of bacteria and infestation of a system. The removal of water, or ensuring its presence is at a minimum, is the best method of infestation prevention. The higher the temperature in settling, service and drain tanks holding fuel or lubricating oils, the better. Test kits are available to detect the presence of bacteria, and biocides can be used to kill all bacteria present in a system. The system must then be thoroughly flushed out

Analysis of Fuel and Lube Oil Flashcards

(86 cards)