Lubricating oil system for a marine diesel engine Function of lubrication: lubrication: The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Its main function is to enable the formation of a film of oil between the moving parts, which reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant.
Lubricating oil system Lubricating oil for an engine is stored in the bottom of the crankcase, known as the sump, or in a drain tank located beneath the engine . The oil is drawn from this tank through a strainer, strainer, one of a pair of pumps, into one of a pair of fine filters. It is then passed through a cooler before entering the engine and being distributed to the various branch pipes. The branch pipe for a particular cylinder may feed the main bearing, for instance. Some of this oil will pass along a drilled passage in the crankshaft to the bottom end bearing and then up a drilled passage in the connecting rod to the gudgeon pin or crosshead bearing.
An alarm at the end of the distribution pipe ensures that adeuate pressure is maintained by the pump. !umps and fine filters are arranged in duplicate with one as standby. The fine filters will be arranged so that one can be cleaned while the other is operating. After use in the engine the lubricating oil drains back to the sump or drain tank for re"use. A level gauge gives a local read"out of the
drain tank contents. A centrifuge is arranged for cleaning the lubricating oil in the system and clean oil can be provided from a storage tank. The oil cooler is circulated by sea water, which is at a lower pressure than the oil. As a result any leak in the cooler will mean a loss of oil and not contamination of the oil by sea water. #here the engine has oil"cooled pistons they will be supplied from the lubricating oil system, possibly at a higher pressure produced by booster pumps,. An appropriate type of lubricating oil must be used for oil"lubricated pistons in order to avoid carbon deposits on the hotter parts of the system. Lubricating Oil Sump Level The level of lubricating oil indicated in the sump w hen the main engine is running must be sufficient to prevent vorte$ing and ingress of air which can lead to bearing damage. The sump level is to be according to manufacturers%shipbuilders instructions . The &Sump 'uantity( is always maintained at the same safe operating level and is given in litres. It is essential that the figures are mathematically steady and correct from month"to"month, taking into account consumption, losses and refills and reported . The &Sump 'uantity( is calculated with the engine stopped, but the lubricating oil pump in operation, thus keeping the system oil in circulation. Sufficient reserve uantities of lubricating oil must always be held, i.e. to completely fill the main sump and sufficient uantities of other lubes must be held to cover the intended voyage plus )*+. Lubricating oils are a maor e$penditure item, therefore, all purchasing must be pre"planned with the aim of buying the ma$imum amounts from the cheapest supply sources which are primarily the -S, urope and Singapore. Lub oil reuisitions should be sent to the office at least /* days before the intended port of purchase and clearly indicate if the vessel reuires supply in bulk or in drums
Lubricating Oil Filters: The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Its main function is to enable the formation of a film of oil between the moving parts, which reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant.
Lubricating oil filters can be found both on the suction and discharge sides of the lubricating oil pump dependent on the installation and type of engine or engines. Their maintenance is absolutely critical to the life e$pectancy of the crankshaft and its bearings, which depends entirely on an uninterrupted supply of c lean and correctly filtered oil. The lubricating oil filter is the final barrier preventing particulate matter 0solid impurities1 from reaching the engine bearings. If the particulate si2e is greater than the hydrodynamic film thickness, i.e. 0*.**) to *.**3 mm1 then mechanical damage will occur to the bearing shell wearing surfaces and the ournal and crankpin surfaces of the crankshaft. It is a fact that failure to maintain an adeuate flow of clean lubricating oil will lead to bearing failure and possible severe damage to the crankshaft.
It is imperative that the long, small diameter, filter candles as used in 4oll 5 6irch type filters are cleaned strictly according to the makers( instructions. -nder no circumstances must dirty cleaning fluid be allowed to flow into the open clean side of the filter candle as it is almost impossible to get dirt out again either by blowing or flushing. Such dirt%impurities, however, will almost certainly find its way directly into the engine once the filter element is back in service. Therefore, when hand"cleaning, the filter candles must stand upright in the cleaning tank 0not lying on the bottom1 and the fluid level in the cleaning tank must be low enough to ensure no fluid flows into the clean side of the candles. Actual cleaning is done by blowing the filter candles with compressed air cleaning gun from the inside of the filter. The cleaning tank must only be used for cleaning filter candles and for no other cleaning work. 7n many vessels, the actual cleaning work is usually left to people who do not always realise the importance of proper cleaning, servicing and assembly of sophisticated lub oil filters. It is therefore most important that the 8hief ngineer ensures and organises total uality control on this service work. If no strict uality control is carried out the filters may actually cause damage to the engine which they are meant to protect. 9or this and other mesh"type lub filters, the cleaning procedures on board are to be carefully monitored and verified and any substandard cleaning immediately corrected. !roper assembly and checking that the clean and dirty side of the filter elements are positively sealed against each other 0o"ring, gaskets etc. in good order1 is essential. 8areful study of the filter maker(s instructions and manuals is essential for anybody entrusted with cleaning, servicing and uality control on board. After cleaning, the cleanliness and condition are to be carefully checked and any
elements replaced should the filter"mesh be damaged. Throw"away filter cartridges made from cellulose or similar material must never be cleaned and reused. These filters must be discarded when dirty and new cartridges fitted. The use of lubricating oil filter by"pass valves is for emergency operation only and must never be opened during routine starting or running conditions.
!articular care must be taken during refitting of filtering cartridges, to ensure that gasket, compression springs etc. are in position and in good condition, in order to avoid any oil bypassing the filtering mesh. Indications of pressure drops and alarms must be maintained operational and must be tested according to maker(s recommendations.
Fire pumps Two independently powered pumps must be provided in all cargo ships of /*** tons gross and over and in passenger ships of less than *** tons gross. Larger passenger vessels and passenger ferries must have three such pumps. The pumps are fitted with non"return valves if they are of the centrifugal type, to prevent loss of water back through open valves when not running. A relief valve is necessary in the system if the pumps are capable of raising the pipeline pressure so that it is greater than the design figure. #ith centrifugal pumps the relief valve is unlikely to be needed but it is essential for a positive displacement fire pump. ;inimum line pressures and capacities are governed by the regulations.
Emergency fire pump This euipment is of the utmost importance to the saf ety of the ship and due care and attention is to be given to both maintenance and training of the euipment. Instructions are to be clearly posted on start"up procedures and valves are to be clearly marked with their correct operating positions. The emergency fire pump is to be run and tested weekly for at least five
minutes, ensuring that remote starts are working and that the reuired pressure can be maintained at the furthest away fire hydrant. If any defects are noted, including insufficient water pressure, then the 8ompany is to be notified and an urgent plan agreed to rectify the situation as uickly as possible. 4y regulation cargo vessels are provided with emergency fire pumps because a fire in the engine room could put all of the other pumps out of action. Such a pump is indicated in 9igure below and is located away from the engine room in the shaft tunnel, steering gear or in the forward part of the ship. The suction lift of any pump is limited and for this reason emergency fire pumps are restricted to being at a ma$imum of < m from the water level at light draught conditions. Ideally they are installed below the waterline to guarantee avoidance of suction problems. There have been difficulties in the past with some steering gear located emergency fire pumps when the ship was in the ballast condition. If the location of a centrifugal type emergency fire pump is the steering flat then, because of the high suction lift involved, a priming pump is fitted. This may be friction driven from the fire pump flywheel and once the fire pump is running the priming pump drive wheel, normally held away from the flywheel by a spring, must be held against it until the fire pump is primed. The fire pump 0centrifugal type1 discharge valve is shut while the pump is being primed and opened gradually as the suction is taken up. 7n large vessels a special two stage pump arrangement may be used . The first stage below the waterline is driven by a hydraulic motor. The second stage and the hydraulic power unit are driven by a prime mover 0or electric motor from the emergency supply1 which can be positioned at more than the normal distance from the waterline. If the fire pump is driven by a water"cooled diesel engine supplied with cooling water from the fire pump a header tank will be provided to ensure that the engine is cooled while the fire pump is being primed. The engine could have a closed circuit fresh"water system, with the water being cooled in a radiator. It is usual however, to fit an air"cooled diesel engine. #here a closed"circuit fresh"water cooled engine is installed anti"free2e may be needed for the radiator in cold weather. An emergency pump has an independent diesel drive or some alternative such as an electric motor powered from the emergency generator.
Emergency fire pump This euipment is of the utmost importance to the saf ety of the ship and due care and attention is to be given to both maintenance and training of the euipment. Instructions are to be clearly posted on start"up procedures and valves are to be clearly marked with their correct operating positions. The emergency fire pump is to be run and tested weekly for at least five minutes, ensuring that remote starts are working and that the reuired pressure can be maintained at the furthest away fire hydrant. If any defects are noted, including insufficient water pressure, then the 8ompany is to be notified and an urgent plan agreed to rectify the situation as uickly as possible. 4y regulation cargo vessels are provided with emergency fire pumps because a fire in the engine room could put all of the other pumps out of action. Such a pump is indicated in 9igure below and is located away from the engine room in the shaft tunnel, steering gear or in the forward part of the ship. The suction lift of any pump is limited and for this reason emergency fire pumps are restricted to being at a ma$imum of < m from the water level at light draught conditions. Ideally they are installed below the waterline to guarantee avoidance of suction problems. There have been difficulties in the past with some steering gear located emergency fire pumps when the ship was in the ballast condition. If the location of a centrifugal type emergency fire pump is the steering flat then, because of the high suction lift involved, a priming pump is fitted. This may be friction driven from the fire pump flywheel and once the fire pump is running the priming pump drive wheel, normally held away from the flywheel by a spring, must be held against it until the fire pump is primed. The fire pump 0centrifugal type1 discharge valve is shut while the pump is being primed and opened gradually as the suction is taken up. 7n large vessels a special two stage pump arrangement may be used . The first stage below the waterline is driven by a hydraulic motor. The second stage and the hydraulic power unit are driven by a prime mover 0or electric motor from the emergency supply1 which can be positioned at more than the normal distance from the waterline. If the fire pump is driven by a water"cooled diesel engine supplied with cooling water from the fire pump a header tank will be provided to ensure that the engine is cooled while the fire pump is being primed. The engine could have a closed circuit fresh"water system, with the water being cooled in a radiator. It is usual however, to fit an air"cooled diesel engine. #here a closed"circuit fresh"water cooled engine is installed anti"free2e may be
needed for the radiator in cold weather. An emergency pump has an independent diesel drive or some alternative such as an electric motor powered from the emergency generator.
International shore connection The international shore connection 09igure below1 is a standard si2ed flange with nuts, bolts and washers and a coupling for the ship=s fittings. The dimensions are shown. The fitting and oint must be suitable for a working pressure of at least /*.> bar. 9our bolts are reuired of /*mm length, also eight washers.
9ig:International shore connection
Hoses and nozzles 9ire hoses must be of approved materials. They are positioned adacent to hydrants together with suitable no22les. ?ual purpose no22les can be adusted by rotation of the sleeve to produce a et or spray. These are an
alternative to having available separate et and spray or fog no22les.
