A method and a system for recovering lubricant when lubricating a large combustion engine and such engine

Abstract

A method and a system for collecting, recovering and reusing lubricant used for lubricating a large combustion engine and such engine A method for lubricating a large combustion engine, and with a lubrication system comprising - a lubricant supply, - a plurality of lubricant injectors distributed along a perimeter of the cylinder, - a lubricant supply conduit connecting the lubricant supply with the lubricant injectors, the engine further comprising - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors, wherein each lubricant injector comprises - an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it, - a nozzle with a nozzle aperture extending into the cylinder. The method furthermore comprises the steps of - collecting drained lubricant, - recovering drained lubricant and - reusing drained and recovered lubricant for lubricating the engine.

Description

[0001] A method and a system for recovering lubricant when lubricating a large combustion engine and such engine

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method and a system for recovering lubricant when lubricating a large combustion engine. Furthermore, the invention relates to an engine provided with such recovering system.

[0004] More specific the invention relates to a method comprising the steps of collecting drained lubricant, recovering drained lubricant and reusing drained and recovered lubricant.

[0005] More specific the invention relates to a system comprising a collecting system for collecting drained lubricant, a recovering system for recovering the drained lubricant in a large combustion engine, for example a large slow-running two-stroke engine.

[0006] In the following the term “engine” will refer to a “large combustion engine, for example a large slow-running two-stroke engine”.

[0007] The engine may be a crosshead engine. Alternatively, the engine may be a trunk engine.

[0008] For example, the large engine, such as slow-running two-stroke crosshead engine, is a marine engine or an engine in a power plant.

[0009] Lubricant is also known as lube oil which is used for lubricating a liner and piston rings in large combustion engines. This lube oil is different from “system oil” used for cooling of moving parts and lubricating bearings etc in the large combustion engines.

[0010] In the following the term “fresh lubricant” will refer to a lubricant which has provided from a supplier, and which has the desired properties for use as a lubricant to lubricating the engine. In the following the term “recovered lubricant” will refer to a lubricant which has been drained from the engine and has been cleaned and upgraded to have similar properties as a fresh lubricant.

[0011] Moreover, the invention relates to a method for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and with a lubrication system comprising

[0012] - a lubricant supply,

[0013] - a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at positions on the perimeter during injection phases,

[0014] - a lubricant supply conduit connecting the lubricant supply with the lubricant injectors, the engine further comprising

[0015] - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors, wherein each lubricant injector comprises

[0016] - an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,

[0017] - a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase wherein the method comprises the steps of

[0018] - draining lubricant from a piston underside,

[0019] - collecting drained lubricant,

[0020] - recovering drained lubricant by steps comprising

[0021] - sedimentation in a sedimentation unit thereby pre-cleaning the drained lubricant for providing a pre-cleaned lubricant,

[0022] - removing impurities in a filter unit and in a centrifuge for providing a filtered lubricant, and

[0023] - reusing drained and recovered lubricant when lubricating the engine.

[0024] Moreover, the invention relates to a large combustion engine, for example a large slow- running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and with a system comprising

[0025] - a lubricant supply,

[0026] - a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at various positions on the perimeter during injection phases,

[0027] - a lubricant supply conduit connecting the lubricant supply with the lubricant injectors,

[0028] - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors,

[0029] - a computer to which the controller is connected, wherein each injector comprises

[0030] - an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,

[0031] - a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase when using the engine in cyclic operation, wherein the engine in the injection phase provides pressure-liquid to the lubricant supply conduit and wherein the engine comprises a system for collecting, recovering and reusing lubricant.

[0032] BACKGROUND OF THE INVENTION

[0033] Due to the focus on environmental protection, efforts are on-going with respect reduction of emissions from marine engines. This also involves the steady optimization of lubrication systems for such engines, especially due to increased competition. One of the economic aspects gaining increased attention is a reduction of oil consumption, not only because of environmental protection but also because this is a significant part of the operational costs of ships. Especially the lubricant for lubrication of the cylinder liner and the piston rings gains attention as it is a costly oil. A further concern is proper lubrication despite reduced lubricant volume because the longevity of engines should not be compromised by the reduction of oil consumption. Thus, there is a need for steady improvements with respect to lubrication. For lubricating of large slow-running two-stroke marine diesel engines, several different systems exist, including injection of lubrication oil directly onto the cylinder liner or injection of oil quills to the piston rings.

[0034] The lubrication may be effected as jet injection which is an injection where lubricant in metered quantity is injected as a compact jet into the liner of a cylinder or into the piston ring pack. This is also called pulse lubrication.

[0035] Alternatively, the lubrication may be effected as a spray injection where lubricant under hight pressure is injected into the combustion chamber. Hereby a fine mist of the lubricant is injected into the cylinder, preferably in the combustion chamber. The lubricant is provided as a mist of atomized droplets. The injector for spray injection is called spray injector. A specific spray injection is SIP injection. The injector for SIP injection is called SIP injector. The SIP injection is explained in further detail below.

[0036] An example of a lubricant injector for a marine engine is disclosed in EP1767751, in which a non-retum valve is used to provide the lubricant access to the nozzle passage inside the cylinder liner. The non-return valve comprises a reciprocating spring-pressed ball in a valve seat just upstream of the nozzle passage, where the ball is displaced by pressurised lubricant. The ball valve is a traditional technical solution, based on a principle dating back to the start of the previous century, for example as disclosed in GB214922 from 1923.

[0037] An alternative and relatively new lubrication method, compared to traditional lubrication, is commercially called Swirl Injection Principle (SIP). It is based on injection of a spray of atomized droplets of lubricant into the scavenging air swirl inside the cylinder. The helically upwards directed swirl results in the lubricant being pulled towards the Top Dead Centre (TDC) of the cylinder and pressed outwards against the cylinder wall as a thin and even layer. This is explained in detail in international patent applications W02010 / 149162 and W02016 / 173601. The injectors comprise an injector housing inside which a reciprocating valve member is provided, typically a valve needle. The valve member, for example with a needle tip, closes and opens the lubricant’s access to a nozzle aperture according to a precise timing. In current SIP systems, a spray with atomized droplets is achieved at a pressure of, typically, 35-40 bar. In comparison, the oil pressure is less than 30 bar and often less than 10 bar in systems working with compact oil jets that are introduced into the cylinder. In some types of SIP injectors, the high pressure of the lubricant is also used to move a spring-loaded valve member against the spring force away from the nozzle aperture such that the highly pressurised oil is released therefrom as atomized droplets. The ejection of oil leads to a lowering of the pressure of the oil on the valve member, resulting in the valve member returning to its origin and remaining there until the next lubricant cycle where highly pressurized lubricant is supplied to the lubricant injector again.

[0038] In such large marine engines, a number of injectors are arranged in the circumference of the cylinder, and each injector comprises one or more nozzle apertures for delivering lubricant jets or sprays into the cylinder from each injector. Examples of SIP lubricant injector systems in marine engines are disclosed in international patent applications W02002 / 35068, W02004 / 038189, W02005 / 124112, W02010 / 149162,

[0039] WO2012 / 126480, WO2012 / 126473, WO2014 / 048438 and W02016 / 173601.

[0040] Optimization of the spray in SIP lubrication is undergoing steady development. Although, lubrication injectors have some similarities with fuel injectors, comparison also shows different behaviour and different effects. This is mainly attributed to the different working conditions for the injectors, which leads to different effects such as viscosity, surface tension and liquid pressure. Accordingly, results from studies of fuel injection are not automatically transferable to lubricant injection, and the difference in behaviour is in some cases surprising.

[0041] It is known from large slow-running two-stroke engines, e.g. crosshead engines, that rather large amounts of lubricant can be drained away from the engine during the normal operation of the engine. Lubricant will drain away mainly via following drain systems: A: Oil draining from the “Piston underside space” and “Scavenge air receiver” B: Drains from the piston rod stuffing boxes of the engine.

[0042] The oil draining from A originate from the rather large amount of lubricant (lube oil) which is injected into the cylinders of the engine during operation. As mentioned above the purpose of injecting the lubricant is to lubricate cylinder liner and piston rings to reduce friction and wear, and furthermore, the lubricant is utilized e.g. to neutralize sulfuric acid, to clean piston from combustion deposits and fulfill other functions.

[0043] The oil draining from B is a combination of oil from above the cylinder rod stuffing box, the cylinder oil dripping from cylinder lubrication and oil coming from below the stuffing box. The purpose of the stuffing boxes is to facilitate airtight sealing between the upper “piston underside space” and the lower crankcase area.

[0044] The crankcase area is nearly pressure less, whereas the “piston underside space” is pressurized with scavenging air up to app. 4 bar.

[0045] Unfortunately, the lubricants draining from both A and B are contaminated with solid particles (sludge) from the combusting process and water entering the engine via the scavenging air. The contamination with particles and sludge is considered very high, seen in relation to other system oils being cleaned for further use.

[0046] Furthermore, various of the additives in the original lubricant has been warn away or used during the function of the lubricant inside the engine. These drained lubricants from the two-stroke crosshead engines have therefore historical been considered unfit for filtration, cleaning and / or reuse.

[0047] The reuse potential in terms of yearly amount of lubricant from the engines, has also been highly underestimated until now.

[0048] Therefore, the lubricant oil has historically been considered as “sacrificial oil” as it was only injected into the engine one time and considered lost. The continuous consumption of this cylinder oil is a major cost of operating a large slow-running two-stroke engine.

[0049] The reason is that it has been considered impossible to clean and reuse the oil as lubricant. There are examples of reusing lube oil as a part of the system oil supplied to the engine. However, no prior art teaches a method or a system for collecting and cleaning the lubricant and for a following recovering for reusing the drained and recovered lubricant as lubricant to lubricate the cylinder liner and the piston rings.

[0050] As there is a steady motivation for improvement of lubrication in large two-stroke gas and diesel engines, for example marine engines or engines for power plants, one may like to optimise the lubricant consumption for reducing the amount of lubricant used to lubricate the liner and the piston rings and to flush out combustion residues and wear particles. Hitherto the improvements are based on a continuously monitoring showing the build-up of such combustion residues and wear particles for reducing the amount of lubricant and thus reduce the amount of “sacrificial oil”.

[0051] JP 2014084716 A describes a method for lubricating a large combustions engine. The method comprises collecting drained oil, recovering drained lubricant and reusing the drained and recovered lubricant for lubricating the engine.

[0052] Similar technology is described in JP 2010090897 A, JP H0299708 A, JP 2013064401 A, JP S60147519 A, JP H0680805 U and JP S58165515 A.

[0053] These publications describe the draining of lubricant from the piston underside and a recovering comprising a sedimentation only for removing water from the drained lubricant followed by a filtering in a filter unit comprising a centrifuge.

[0054] The publications do not describe draining of lubricant from a scavenge air receiver or from piston rod stuffing boxes. The publications neither disclose a sedimentation unit where sludge is sedimented and where the pre-cleaned lubricant from the sedimentation unit is led via a buffer unit to the filter unit. The publications neither disclose specific method steps to be performed prior to the filtering or to be performed during the filtering steps performed in the filter unit.

[0055] In studies leading to the present invention, it has been found possible to collect, recover and reuse the lubricant drained away from the engine by draining lubricant from the scavenge air receiver and from the piston rod stuffing boxes in addition to the lubricant drained from the piston underside. Especially, it has been found that a substantial amount of lubricant may be drained from the scavenge air receiver. Moreover, the studies have shown that specific method steps are needed in the recovering for obtaining an efficient recovering of lubricant. Especially when the recovering is effected on a marine engine on a ship. These studies have shown that it is possible to obtain an automated sequence to control the collection, cleaning and reuse where the recovered lubricant is used either alone or is mixed together with “new” lubricant for lubrication of a large combustion engine, for example a large slow-running two-stroke engine.

[0056] It is therefore desirable to provide a method and a system which makes it possible to recover lubricant for lubrication of a large combustion engine.

[0057] DESCRIPTION / SUMMARY OF THE INVENTION

[0058] It is the objective of the invention to provide an improvement in the prior art systems in order to collect, recover and reuse lubricant which has earlier been considered as “sacrificial oil” and where the collection comprise collecting lubricant from the scavenge air receiver and from the piston rod stuffing boxes.

[0059] Especially, it is the objective to provide a method and a system where the recovering of the lubricant comprises a sedimentation of sludge, filtering the pre-cleaned lubricant by a combination of centrifugal action, heating and filtering in cellulosic filters, upgrading the lubricant by adding additives and where the upgraded lubricant is blended with fresh lubricant and are led to a lubricant supply of a lubrication system.

[0060] It is a further objective to provide the method and the system for collecting, recovering and reusing as a part of a method and a system for lubrication with SIP injectors or lubrication with a common rail system in large combustion engines, for example in a large slow-running two-stroke engine. However, the recovering system according to the invention may also be used in large four-stroke combustion engines, for example marine engines or combustion engines for power plants.

[0061] Moreover, a purpose of invention is to provide a method and a system for recovering lubricant which makes it possible to optimise an automated sequence for collecting, cleaning and reusing lubricant drained out from drain systems of the large combustion engine. Such automated sequence will preferably be controlled by a controller.

[0062] These objectives are achieved by a method for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine, which method comprises the steps of:

[0063] - draining lubricant from a piston underside,

[0064] - collecting drained lubricant,

[0065] - recovering drained lubricant by steps comprising

[0066] - sedimentation in a sedimentation unit thereby pre-cleaning the drained lubricant for providing a pre-cleaned lubricant,

[0067] - removing impurities in a filter unit and in a centrifuge for providing a filtered lubricant, and

[0068] - reusing drained and recovered lubricant for lubricating the engine, peculiar in that the method comprises the steps of:

[0069] - draining lubricant comprises draining lubricant away via:

[0070] A: draining lubricant from a scavenge air receiver and

[0071] B: draining lubricant from piston rod stuffing boxes of the engine.

[0072] These objectives are also achieved by a method for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and with a lubrication system comprising

[0073] - a lubricant supply,

[0074] - a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at positions on the perimeter during injection phases,

[0075] - a lubricant supply conduit connecting the lubricant supply with the lubricant injectors, the engine further comprising

[0076] - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors, wherein each lubricant injector comprises

[0077] - an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,

[0078] - a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase, wherein the method comprises the steps of

[0079] - draining lubricant from a piston underside,

[0080] - collecting drained lubricant,

[0081] - recovering drained lubricant by steps comprising

[0082] - sedimentation in a sedimentation unit thereby pre-cleaning the drained lubricant for providing a pre-cleaned lubricant,

[0083] - removing impurities in a filter unit and in a centrifuge for providing a filtered lubricant, and

[0084] - reusing drained and recovered lubricant for lubricating the engine, peculiar in that

[0085] - the step of draining lubricant further comprises draining lubricant away via:

[0086] A: draining lubricant from a scavenge air receiver and

[0087] B: draining lubricant from piston rod stuffing boxes of the engine.

[0088] In an example of the method the injection in the injection phase will be the SIP injection explained above.

[0089] The system for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine, the which system comprises:

[0090] - a collecting system for collecting drained lubricant from a piston underside,

[0091] - a recovering system for recovering the drained lubricant and which recovering system comprises a sedimentation unit and a filter unit,

[0092] - a lubrication system for reusing the drained and recovered lubricant for lubricating the engine, peculiar in that the collecting system further comprises

[0093] A: a drain system for draining lubricant from a scavenge air receiver and B: a drain system for draining lubricant from piston rod stuffing boxes of the engine.

[0094] Moreover, the objectives are obtained with a system according to the invention for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and which system comprises

[0095] - a lubricant supply,

[0096] - a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at various positions on the perimeter during injection phases,

[0097] - a lubricant supply conduit connecting the lubricant supply with the lubricant injectors,

[0098] - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors,

[0099] - a computer to which the controller is connected, wherein each injector comprises

[0100] - an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,

[0101] - a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase when using the engine in cyclic operation, wherein the engine in the injection phase provides pressure-liquid to the lubricant supply conduit, wherein the system further comprises:

[0102] - a collecting system for collecting drained lubricant from a piston underside,

[0103] - a recovering system for recovering the drained lubricant, which recovering system comprises a sedimentation unit and a filter unit and

[0104] - a lubrication system for reusing the drained and recovered lubricant for lubricating the engine, peculiar in that the collecting system further comprises

[0105] A: a drain system for draining lubricant from a scavenge air receiver and

[0106] B: a drain system for draining lubricant from piston rod stuffing boxes of the engine.

[0107] In an example of the system the injection in the injection phase will be the SIP injection explained above. These objectives are also achieved by a method for recovering lubricant used for lubricating a large combustion engine, for example a large slow-running two-stroke engine, wherein:

[0108] - lubricant has been drained from a piston underside space, scavenge air receiver and piston stuffing boxes of the engine,

[0109] - lubricant has been collected,

[0110] - lubricant has been pre-cleaned by sedimentation in a sedimentation unit for providing a pre-cleaned lubricant, peculiar in that the method comprising:

[0111] - leading the pre-cleaned lubricant to a filter unit comprising a centrifuge and a mechanical filter e.g. a cellulose-based filter and

[0112] - finally cleaning of the pre-cleaned lubricant by centrifugal filtering and filtering in the mechanical filter.

[0113] The lubricant cleaning centrifuge is also called centrifugal filter. The centrifuge is characterized by having a spinning bowl driven the lubricant flow, also called flow driven centrifuge. Typically, the centrifuge will be driven with app. 4.000 revolutions per minute. Alternatively, the centrifuge may be driven with other driving means e.g. an electric motor.

[0114] The centrifugal filter will collect dirt and particles from the lubricant on a mechanical filter lining in the centrifuge bowl. Typically, it is a paper lining which is inserted in the spinning bowl.

[0115] The method and the system according to the present invention is especially intended and suitable for use in a marine engine on a ship.

[0116] The large combustion engine, for example a large slow-running two-stroke engine according to the invention is peculiar in that the engine further comprises the system according to any one of the claims 16 - 21.

[0117] The invention is especially developed for recovering drained lubricants from two-stroke crosshead engines. The invention involves that lubricant for cylinder lubrication is provided wholly or partly as collected, cleaned and reused lubricant which have been drained out from below drain systems of the large combustion engine.

[0118] The invention makes it possible to reuse the collected and recovered drain oil as lubricant for the cylinder liner and piston rings for the engine prior to reinjection into the engine, it is often needed to upgrade the drained and cleaned lubricant with additives.

[0119] Accordingly, the rather large amount of lubricant that is drained away from the engine during the normal operation of the engine may be reused. This gives advantages in form of environmental protection due to reduction of sacrificial oil from the engines. This also involves advantages of the cost reduction gained by reduction of lubricant consumption.

[0120] In studies leading to the present invention it has shown that it might be possible drain and collect up to 60% of the lubricant injected.

[0121] Furthermore, it has shown that the part of lubricant drained from the scavenge air receiver may constitute up to 30 % of the total amount of lubricant collected. This amount is found at higher load of the engine whereas the amount of lubricant drained from the scavenge air receiver may be a lower percentage at lower load of the engine.

[0122] Introduction of the recovered lubricant will also improve the environmental footprint of the engine operation significant. Recovered lubricant will reduce CO2 emissions and reduce the consumption of various chemicals, additives and carbon-based base oils.

[0123] Moreover, the consumption of additives is reduced when utilizing drained and cleaned lubricant. The cleaned drain oil still contains a significant amount of usable additives. This means less additional additives is needed for the final blend of lubricant, compared to production of fresh lubricant where a relative clean base oil is mixed with relative higher concentration of additives.

[0124] The collecting drained lubricant comprises the steps of - draining lubricant away via draining steps for:

[0125] A: draining lubricant from a piston underside space and a scavenge air receiver and B: draining lubricant from piston rod stuffing boxes of the engine.

[0126] The lubricant drained from A and B originates from lubricant injected by lubricant injectors distributed along a perimeter of the cylinder.

[0127] This lubricant is no longer a “sacrificial oil” as it is collected and recovered for being injected into the engine more than one time.

[0128] The drained lubricant is a combination of lubricant from above the piston rod stuffing box, the cylinder oil dripping from cylinder lubrication and oil coming from below the stuffing box. The purpose of the stuffing boxes is to facilitate airtight sealing between the upper “piston underside space” and the lower crankcase area.

[0129] The oil entering the internal stuffing box from below is “system oil” in some teaching also called as “crank case oil”. This oil originates from a separate oil system with separate oil type / grade. The main purpose of the system oil is to lubricate and cool moving parts of the engine e.g. bearings.

[0130] During the engine operation, the piston rod will move up and down through the stuffing box. When the piston is almost in Bottom Dead Center (BDC) the piston rod will be sprayed with system oil inside the crankcase. When the piston starts to move upwards towards Top Dead Center (TDC), some of the oil on the rod will pass the scraper rings of the stuffing box and some oil will enter the center part of the stuffing box assembly.

[0131] The same phenomenon happens from the top side, where some lubricant / lube oil dripping from the cylinder will be dragged down into the stuffing box, during the downwards movement of the piston.

[0132] It is not desirable to have used lubricant mixed with the relative clean system oil of different type / grade. The stuffing boxes therefore are provided with a collecting system comprising a drain system in form of drainpipes connected to the center part of the assembly. This allow the oils entering the stuffing box either from above or below to escape to the outside of the engine and being drained away.

[0133] This is reducing the risk of cross contamination of lubricant and system oil.

[0134] The amount of oil draining from the stuffing boxes depends among other factors of air pressure in the “piston underside space”, engine RPM and wear condition of the sealing rings in the stuffing box.

[0135] In one embodiment the oil draining from the stuffing boxes is pumped, by a drain pump, into the drain piping from “Piston underside space” and “Scavenge air receiver” upstream of a sedimentation unit. In a practical embodiment the sedimentation unit comprises a “Sludge Collecting Unit”- SCU. The SCU will be explained in further detail below. The drain pump used is typically of membrane type.

[0136] The purpose of the stuffing box drain pump unit is to pump the drain oil from the pressure less stuffing box drain system into the pressurized drain from “Piston underside space” and “Scavenge air receiver”.

[0137] The reason for this pumping transfer of oil is to allow particles and sludge in the stuffing box oil to settle and segregate in the SCU together with drain oil coming from “Piston underside space” and “Scavenge air receiver”.

[0138] As mentioned, the oils drained from A and / or B are containing large amount of solid particles with particle seizes ranging from few micron to several millimeters. It is necessary to segregate most of the larger particles prior to further treatment and cleaning. The oil is too contaminated with relatively large particles to allow use of pumps, filters and other process equipment. Therefore, sedimentation is established prior to guiding the oil to a filter unit for filtering the overflow of lubricant from the sedimentation unit.

[0139] According to prior art the initial segregation of these large particles mainly takes place in the “Sludge Collecting Unit” (SCU) described in WO 2022 / 106341 Al.

[0140] The piping and ducts used for transferring the drained lubricant to the SCU will preferably comprise an auger. In an example the augur is of construction described either in WO 2018 / 233789 or WO2022 / 157134. This ensures the possibility for an automatic cleaning of piping and ducts.

[0141] The main function of the SCU is to initial segregate most of the large, heavy and solid particles by settling (gravitation). In one embodiment the settling takes place inside a standard 210L (55 gallon) steel barrel. The steel barrel serves as a replaceable cartridge containing segregated particles and sludge. This process is very efficient for initial and rough cleaning of the drain oils. The SCU is designed in a special way to allow balance of the engine scavenging air pressure inside / outside the standard 210L barrel as described in WO 2022 / 106341 Al.

[0142] After initial and rough sedimentation / segregation of parti cles / sludge in the SCU, the sedimented sludge will accumulate in the bottom of the SCU which will be more and more full. Where a certain level of sludge is accumulated in the SCU the steel barrel will be replaced. The steel barrel containing the sludge will be stored and transported to a sludge handling plant. This sludge handling plant will be an on-shore plant. Accordingly, the steel barrels in a system for a marine motor will be stored and unloaded when the ship docs.. This SCU unit and the handling are described in WO 2022 / 106341 Al.

[0143] A pre-cleaned overflow of lubricant from the SCU may flow to a buffer tank before entering a filter unit for providing final cleaning process and provide a filtered lubricant

[0144] The purpose of the buffer tank is to store the pre-cleaned overflow of lubricant, until it is transferred into a filter unit. The filter unit will typically treat the pre-cleaned lubricant batchwise. Therefore, the buffer tank is used, and the pre-cleaned lubricant is transferred to the filter unit when it is ready to receive next batch of pre-cleaned lubricant.

[0145] The buffer tank can consist of one or more tanks. The buffer tanks can be existing tanks or new installed tanks. In an embodiment the buffer tank is constructed with liquid level sensing system to inform present level to the control system.

[0146] The buffer tank is also constructed with automated bottom drainage system. The drainage system is designed to automatically detect sludge accumulation and automatically remove it to a separate “Sludge tank”. The content of the sludge tank can be discharged. E.g. the sludge may be pumped to a tank truck or ship with tanks by means of related pump and piping. The sludge content from the sludge tank is normally transferred to an on-shore-based facility for environmental process / treatment.

[0147] In an embodiment of the invention the lubricant is heated prior to transfer into the filter unit in which the final cleaning by a process comprising centrifugation and filtering in mechanical filter elements. The filter elements are in one example cellulose-based filter elements, e.g. filters from C.C. Jensen.

[0148] The heating may take place with a heating coil build into the buffer tank or with a separate heat exchanger build into a piping line between buffer tank and the filter unit. The heating may also take place in a heat exchanger in form of a pre-heating unit being a part of the filter unit. The heating may also be effected as a combination of two or all three of the possible heating methods.

[0149] Accordingly, heating may be effected as a combination of heating in the buffer tank and heating in the piping leading the pre-cleaned lubricant into the filter unit and heating I a pre-heater being part of the filter unit.

[0150] It has shown that the temperature existing in the pre-cleaned oil is machine room in the ship creates difficulties in the centrifugation and filtering process. Therefore, a heating of the pre-cleaned lubricant prior to the centrifugation and filtering process is important for providing an efficient centrifugation and filtering of the lubricant in the filter unit.

[0151] The heating reduces the viscosity of the lubricant and thereby provides for more efficient centrifugation and filtering. The heating is also lowering the density of the lubricant. This makes the segregation of more heavy particles more effective in the centrifugation process.

[0152] The heating media for the heating of lubricant from or in the buffer tank can be engine cooling water. Using the engine cooling water may provide at heating of the pre-cleaned lubricant to a temperature between 50 and 99 °C, preferably between 75 and 85 °C.

[0153] The heating may be effected in a heat exchanger in which hot water from the cooling system of the engine is used for heating the pre-cleaned lubricant. This is advantageous as the cost for heating the pre-cleaned lubricant hereby is greatly or totally reduced. High temperature cooling water is normally seen as “wase energy” on most ships.

[0154] Alternatively, steam, hot oil, electric heating, or other heat sources may be used as heating media for heating the pre-cleaned lubricant.

[0155] The cleaning process of the filter unit is described in detail later.

[0156] The filter unit work with batches. This means there is no constant flow through the filter unit.

[0157] An example of a batch of pre-cleaned lubricant is e.g. 2000L. This batch stays in the filter unit until sufficient cleaned. This is the reason why a buffer tank is needed to contain oil draining from the engine until the filter unit is ready to receive next batch.

[0158] Likewise, a storage tank to store the filtered lubricant is often needed before transferring the filtered lubricant to a blending unit which is connected with at least one additive supply, and which is intended for upgrading the filtered lubricant by adding additives from an additive supply into the filtered lubricant and thereby providing the upgraded lubricant for reuse. Alternatively, the filtered lubricant may be transferred directly to the blending unit.

[0159] Thus, in one embodiment the filtered lubricant from the filter unit is transferred to a storage tank for filtered lubricant. Alternatively, a solution is to upgrade the filtered lubricant with additives before or when being transferred from the filter unit. In this case the upgraded lubricant can be transferred directly to a mixing unit for blending the upgraded lubricant with fresh lubricant to provide a blended lubricant and to transport the blended lubricant to a lubricant supply of a lubrication system.

[0160] Alternatively, the upgraded lubricant can be transferred as a recovered lubricant to directly to the lubricant supply of the lubrication system.

[0161] The upgrades lubricant will be a recovered lubricant ready for use in the lubrication system for lubricating the engine.

[0162] The filter unit may in an embodiment be constructed with the blending unit build into the unit or included in the filter unit. However, in general the blending unit will be a separate unit.

[0163] A blending unit will receive cleaned oil from the storage tank for filtered lubricant either by gravity or by means of a pump.

[0164] The blending unit is used to add and blend and mix additives into the filtered lubricant to create an upgraded lubricant with properties corresponding to the properties of fresh lubricant and which is suitable for later injection into the engine.

[0165] The blended and mixed lubricant leaving the mixing unit is normally referred to as “Lubricant”.

[0166] The lubricant from mixing unit is normally transferred to lubricant supply tank of the lubrication system. This lubricant supply tank is typically a smaller tank which is often named “Lubricant day tank”. The purpose of this tank is to hold sufficient lubricant to lubricate the engine for a day or few days.

[0167] In some cases, blended lubricant from the Blending Unit can also be transferred to other and normally larger storage tanks. The blending unit and the mixing unit can be provided as one single unit in which it is possible to blend lubricants and additives from a mix of several sources and tanks. In one embodiment the blending unit can blend from additive tank plus lubricant type 1 tank plus lubricant type 2 tank plus cleaned lubricant from the cleaned lubricant storage tank.

[0168] The additive tank may contain a “additive package” meaning an oil with a very high concentration of additives. This “additive package” is then blended with one or more oils or additional additives in a desired ratio for the final lubricant for use in the lubrication system.

[0169] The blending ratio is often calculated based on the calcium content (Base number) of the additive package(s) and oil(s) respectively. The additive package is containing a variety of additives. The purpose of the blend with additive package is to improve the calcium level of the final lubricant for use in the lubrication system as well as improve other performance properties of the oil. Performance properties to improve could be oxidation resistance, detergency, wear resistance, viscosity index, viscosity and other properties.

[0170] The actual ratio of chosen oils, additives and other content is controlled by weight and or volume. The blending unit will control the mass and or volume of the various oils and additives.

[0171] The actual mixing and blending in the blending unit is either based on flow-based mixing or batch-based mixing.

[0172] The flow-based mixing device with continuous flow will receive oils and additives through individual flow controlling devices (flowmeters) at the desired ratio. The mixing device will create turbulence of the flowing oils and additives and thereby form a homogeneous mixture when the mixture leaves the mixing device.

[0173] The batch-based mixing and blending is distinguished by the mixing taking place in a tank without flow out at the time of mixing and blending. In one embodiment of the batch-based blending unit, the batch tank is supported by weight cells. The batch tank is connected to its pipe and valve system, using flexible hoses - thus not affecting the wight cells significantly.

[0174] This allows stepwise filling of the batch tank with the desired oils and additives.

[0175] The control unit will control filling mass of each individual oil and additive by measuring the mass of incoming oil and additive using the weight cells supporting the batch tank.

[0176] When desired amount of each oil and / or additive is contained in the batch tank, a pump will circulate the batch tank content until a homogeneous mixture is created.

[0177] After end mixing and circulation, the now blended lubricant can be transferred by pump or gravity to desired tank either the lubricant day tank or the larger lubricant storage tank.

[0178] In another embodiment of the batch-based blending unit, the liquid level and / or volume in the batch tank is monitored by one or more level sensor(s).

[0179] The control unit will control filling volume of each individual oil and additive by measuring the volume increase resulting from the incoming oil and additive using level sensors) in the batch tank.

[0180] When desired amount of each oil and / or additive is contained in the batch tank, a pump will circulate the batch tank content until homogeneous mix is created. After end mixing and circulation, the now blended lubricant can be transferred by pump or gravity to desired tank either the lubricant day tank or the larger lubricant storage tank.

[0181] In another embodiment of the batch-based blending the tank in the filter unit is utilized as batch tank for batch-based blending. The blending ratio of oils and additives is controlled by level and volume in this embodiment. The lubrication system of the engine will receive lubricant from the lubricant day tank. The engine integrated lubrication system is injecting lubricant into each cylinder of the engine by injectors described earlier. The amount of injected lubricant is normally controlled by the control system.

[0182] The engine operator can change settings for the cylinder lubrication control and dosage.

[0183] In general, one can say the cleaning occur in two steps: a coarse cleaning and a fine clearing.

[0184] The coarse cleaning is affected in the sludge collecting unit and the fine cleaning is effected in the filter unit where lubricant is cleaned in batches.

[0185] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0186] - leading the pre-cleaned lubricant as an overflow from the sedimentation unit to a buffer unit

[0187] - leading the pre-cleaned lubricant batchwise from the buffer unit to the filter unit.

[0188] In the filter unit the pre-cleaned lubricant is treated batchwise. And the filter unit is only emptied for lubricant when it has reached a desired degree of cleaning. Hower during the treatment of the batch the sludge collected in the bowl of the centrifuge will be removed and a clean bowl is installed in the centrifuge.

[0189] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0190] - heating the pre-cleaned lubricant prior to centrifugation and filtering in the filter unit.

[0191] The heating may be effected to temperatures between 50 and 99 °C, preferably between 75 and 85 °C.

[0192] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising: -leading the pre-cleaned lubricant through an 30-130 Micron self-cleaning edge filter when entering the filter unit.

[0193] The self-cleaning filter is arranged in the piping leading the pre-cleaned lubricant from the buffer unit to the filter unit or alternatively the self-cleaning is arranged in a common tank being containing the filter unit.

[0194] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0195] - heating is effected by using the engine cooling water in a heating unit to provide at heating of the pre-cleaned lubricant to a temperature between 50°C and 99 °C, preferably between 75°C and 85 °C.

[0196] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0197] - controlling, by a controller, an automated sequence of steps for cleaning the lubricant drained out from the engine.

[0198] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0199] - monitoring sludge accumulation level of a sludge cake built up in the centrifuge bowl, which monitoring may be effected as inertia-based sludge cake measurements or bowlweighing based sludge cake measurements and

[0200] - stopping and emptying the centrifuge bowl at predetermined levels of sludge accumulation before the centrifuge over-fills.

[0201] An example of the method for recovering lubricant used for lubricating a large combustion engine is peculiar in that method comprising:

[0202] - cleaning the batch in a process taking 5-7 days,

[0203] - stopping and emptying the centrifuge bowl when initiating cleaning of a batch is effected at short intervals of only few hours, typically at intervals between 3 and 7 hours but even as low as every second hours. The cleaning of the batch may be different from 5-7 days which is a typical time. For more “clean” lubricant the cleaning may only take 3 days and for more “dirty” lubricant the cleaning may take up to 10 days.

[0204] The time intervals between the emptying the centrifuge differs over the time when the batch is cleaned in the centrifuge. When the centrifugal cleaning continues the time between emptying will increase. Already after 2-3 days the interval between emptying the centrifuge may be up to 24 hours or even up to 72 hours.

[0205] The time intervals will be controlled of the control unit and be based on the measured filing of the centrifuge with sludge as explained in further detail below. Especially the time interval is determined in order to obviate that a sludge cake will reach bowl discs in the centrifuge. More detailed explanation if found in the description of Fig. 8.

[0206] In the following explanation is given where some of the elements in the system is explained with other terminology than the terminology uses above. E.g. the filter unit is also denoted as a LRS unit or LRS tank where LRS has the meaning “Lube oil Reuse System”.

[0207] In a specific embodiment the following steps are used.

[0208] When filling the LRS tank, the coarsely cleaned lubricant is heated to a temperature of approx. 50-70°C. The lubricant is then led through an approx. 30-0 Micron self-cleaning edge filter when entering the LRS tank. The self-cleaning edge filter may be between 30 and 130 Micron. An example of such self-cleaning edge filter is illustrated in Fig. 5

[0209] The LRS tank is a unit in which the pre-cleaned lubricant will be finally cleaned before being transferred to the tank for cleaned lubricant.

[0210] Before entering the LRS tank or in the LRS tank, the lubricant is heated to approx. 70- 85°C. In a marine engine waste heat from the engine’s cooling water system is used to heat the lubricant. The lubricant is heated to obtain a sufficiently low viscosity, as well as to lower the lubricant’s specific gravity. The lubricant is then circulated through the centrifugal filter. This may be a step taking approx. 5-7 days.

[0211] The last step is circulation of the lubricant through a cellulose-based filter, e.g. a filter from C.C. Jensen. This filtering ensures that lubricant with a significant content of particles or water does not pass through.

[0212] The lubricant is now ready for storing for later upgrading by adding additives in order to be ready for reuse.

[0213] Below different embodiments of the method and the system will be defined.

[0214] According to a further embodiment of the invention the method is peculiar in that the step of recovering comprises the following steps of

[0215] - establishing a sedimentation of sludge for creating an overflow of lubricant from the sedimentation step,

[0216] - filtering the lubricant for providing a filtered lubricant and

[0217] - upgrading the filtered lubricant by adding additives and thereby providing the upgraded lubricant for reuse.

[0218] According to a further embodiment of the invention the method is peculiar in that the recovering step further comprises a step of

[0219] - heating the overflow of lubricant from the sedimentation unit.

[0220] According to a further embodiment of the invention the method is peculiar in that the method comprises the steps of

[0221] - mixing the upgraded lubricant with fresh lubricant to provide a blended lubricant and

[0222] - leading the blended lubricant to a lubricant supply of a lubrication system.

[0223] According to a further embodiment of the invention the method is peculiar in that the method comprises the step of controlling, by a controller, an automated sequence of steps for collecting, cleaning and reusing lubricant drained out from drain systems of the engine. According to a further embodiment of the invention the system is peculiar in that the collecting system comprises:

[0224] A: a drain system for draining lubricant from a piston underside space and a scavenge air receiver and

[0225] B: a drain system for draining lubricant from piston rod stuffing boxes of the engine.

[0226] According to a further embodiment of the invention the system is peculiar in that the recovering system comprises:

[0227] - a sedimentation unit for sedimentation of sludge and providing an overflow of lubricant from the sedimentation unit,

[0228] - a filter unit for filtering the overflow of lubricant from the sedimentation unit and arranged for providing a filtered lubricant, and

[0229] - a blending unit which is connected with at least one additive supply, and which is intended for upgrading the filtered lubricant by adding additives from the additive supply into the filtered lubricant and thereby providing the upgraded lubricant for reuse.

[0230] According to a further embodiment of the invention the system is peculiar in that the recovering system further comprises

[0231] - a heating unit for heating the overflow of lubricant from the sedimentation unit.

[0232] According to a further embodiment of the invention the system is peculiar in that the system comprises:

[0233] - a mixer unit for blending the upgraded lubricant with fresh lubricant to provide a blended lubricant and

[0234] - transport means for leading the blended lubricant to a lubricant supply of a lubrication system.

[0235] According to a further embodiment of the invention the system is peculiar in that the method comprises a controller for controlling an automated sequence of steps for collecting, cleaning and reusing lubricant drained out from drain systems of the engine.

[0236] In a specific embodiment the method of lubricating a large slow-running two-stroke engine includes the steps of providing for the engine - a computer to which the controller is connected, or alternatively

[0237] - a mobile phone arranged to communicate with the controller.

[0238] The controller may be built into the system or may be connected to the system.

[0239] The controller may be connected to the system by wiring or in a wireless way.

[0240] The controller may also be arranged for controlling the lubricant type used.

[0241] The control unit is designed to be user-friendly and with a high degree of failsafe (foolproof).

[0242] In a normal "Automatic mode", the control unit will prevent incorrect operation and inappropriate use. This is done because the equipment must be operated by operators having different competence level.

[0243] The control unit comprise a log system that logs a multitude of parameters, e.g. alarms pressure, temperatures, centrifugation time, revolutions and more.

[0244] Results from the log system may be transmitted to a central computer via internet or may be extracted manually to a storage item e.g. an USB key.

[0245] Furthermore, the operator must enter the result of lubricant analyzes carried out on the lubricant on board. This is effected with test kits. The results may comprise results measured for water content BN (Base no) and viscosity. These results will be entered into the control system via a HMI panel when prompted. The entered results must be within defined limits - before the lubricant is allowed to be sent on to the "Cleaned lubricant storage tank" for use in lubricating the engine.

[0246] Moreover, the control unit comprises assistance functions for troubleshooting. It is an option to set the control unit to “Manual operation” and thereby control the process completely manually. This may be used during running-in and possible troubleshooting or as a temporary solution to a problem.

[0247] The control unit provides a monitoring of revolutions of the centrifuge and that the system is stopped with an alarm if the revolution is outside permissible predefined limits stored in the control unit. In the same way, the control unit provides for a "level alarm" in a waste tray under the centrifuge. This will stop all pumps and give an alarm if a leak should occur at the centrifuge.

[0248] The method and the system may be used for lubricating a marine engine on a ship.

[0249] The method and the system make use of an HMI-panel for operating and controlling the process and system.

[0250] The system can be used both as a retrofit on existing engines, marine engines on ships and installations such as power plants on shore, as well as for installation in or on new engines, marine engines on ships and installations such as power plants on shore. The system can be used independent of the type of fuels being combusted in the engine.

[0251] SHORT DESCRIPTION OF THE DRAWINGS

[0252] The invention will be explained in more detail with reference to the drawing, where Fig. 1 is a sketch of part of a cylinder in an engine according to prior art,

[0253] Fig. 2 is a drawing of an engine in which the system and method according to the invention may be implied,

[0254] Fig. 3 is a sketch of a system according to the invention,

[0255] Fig. 4 is a sketch illustrating separation and cleaning principle in a coiled cartridge for use in filtering the lubricant,

[0256] Fig. 5 is a sketch illustrating the functional principle of a metal-edge filter corresponding to Fig. 4 in filtering the lubricant according to the present invention, Fig. 6 is a sketch illustrating the flow through a filter unit for use in an embodiment of a system according to the present invention, Fig. 7 is a more detailed sketch of the filter unit illustrated in Fig. 6 illustrating more construction details,

[0257] Fig. 8 is a sketch illustrating a centrifuge for use in an embodiment of the system according to the present invention,

[0258] Fig. 9 is a sketch illustrating a transfer unit in an embodiment of the system according to the present invention,

[0259] Fig. 10 is a sketch of a more detailed embodiment of a filter unit for use in an embodiment of the system according to the present invention and

[0260] Fig. 11 is a PI diagram of a filter unit according to the present invention.

[0261] DETAILED DESCRIPTION / PREFERRED EMBODIMENT

[0262] In Fig. 1 is illustrated of part of a cylinder in an engine according to prior art e.g. shown in WO 2023 / 088526 Al. Fig. 1 illustrates a lubrication for an engine in which the system and method according to the present invention may be used.

[0263] In Fig. 1, only the elements necessary for understanding the lubrication system are shown. More elements will be needed in an actual system.

[0264] Fig. 1 illustrates one half of a cylinder 1 of a large slow-running two-stroke engine, for example marine diesel engine. The cylinder 1 comprises a cylinder liner 2 on the inner side of the cylinder wall 3. Inside the cylinder wall 3, there are provided a plurality of injectors 4 for injection of lubricant into the cylinder 1. As illustrated, the injectors 4 are distributed along a circle with the same angular distance between adjacent injectors 4, although this is not strictly necessary. Also, the arrangement along a circle is not necessary, seeing that an arrangement with axially shifted injectors is also possible, for example every second injector shifted towards the piston’s top dead centre (TDC) relatively to a neighbouring injector.

[0265] Each of the injectors 4 has a nozzle 5 with a nozzle aperture 5’ from which a fine atomized spray 8 with miniature droplets 7 is ejected under high pressure into the cylinder 1. For example, the nozzle aperture 5’ has a diameter of between 0.1 and 0.8 mm, such as between 0.2 and 0.5 mm, which at a pressure of 10-100 bars, for example 25 to 100 bars, optionally 30 to 80 bars or even 50 to 80 bars, atomizes the lubricant into a fine spray 8, which is in contrast to a compact jet of lubricant. The swirl 14 of the scavenging air in the cylinder 1 transports and presses the spray 8 against the cylinder liner 2 such that an even distribution of lubrication oil on the cylinder liner 2 is achieved. This lubrication system is known in the field as Swirl Injection Principle, SIP.

[0266] However, also other principles are envisaged in a lubrication system, for example injectors that have jets directed towards the cylinder liner.

[0267] Optionally, the cylinder liner 2 is provided with free outs 6 for providing adequate space for the spray 8 or jet from the injector 4.

[0268] In addition to the lubricant feed conduit 9, the injectors 4 are connected to the controller 11 by a pressure-control conduit 10. The lubricant feed conduit 9 is used for providing lubricant for injection. The pressure-control conduit 10 provides oil at high pressure to activate an internal pumping system inside the injector 4.

[0269] The pressure in the pressure-control conduit 10 is higher than the pressure in the lubricant feed conduit 9. Typically, the lubricant pressure in the lubricant feed conduit 9 is in the range of 1-15 bar, for example in the range of 5-15 bar, and the oil pressure in the pressure-control conduit 10 is in the range 20-100 bar, for example in the range 30-80 bar, optionally 50-80 bar.

[0270] The controller 11 is connected to a supply conduit 12 for receiving lubricant from a lubricant supply 25, including an oil pump and a return conduit 13 for return of lubricant, typically to an oil reservoir, optionally for recirculation of lubricant. The lubricant pressure in the supply conduit 12 is higher than the pressure in the return conduit 13, for example at least two times higher.

[0271] The controller 11 supplies lubrication oil to the injectors 4 in precisely timed pulses, synchronised with the piston motion in the cylinder 1 of the engine. For example, for the synchronisation, the controller system 11 is electronically by wires or wireless connected to a computer 19 which controls components in the controller 11 for the lubrication supply. Potentially, the computer 19 is part of the controller 11, for example provided inside a single casing with the other components of the controller 11. Optionally, the computer monitors parameters for the actual state and motion of the engine, for example speed, load and position of the crankshaft, the latter revealing the position of the pistons in the cylinders.

[0272] Furthermore, the controller will control the function of the method steps and the elements of a system according to the present invention and which system comprises

[0273] - a collecting system for collecting drained lubricant,

[0274] - a recovering system for recovering the drained lubricant and

[0275] - a lubrication system for reusing the drained and recovered lubricant for lubricating the engine.

[0276] Alternatively, two separate controllers may be used.

[0277] In the following explanation is given to the drawings. Some of the elements in the system is explained or illustrated with other terminology than the terminology uses above.

[0278] Fig. 2 is a sketch of an engine in which the system and method according to the invention may be implied. The engine is a large slow-running two-stroke crosshead marine engine.

[0279] In Fig. 2 different elements are described in order to give an understanding of the construction of the engine.

[0280] Fig. 3 illustrates a diagram of a lay-out for a system according to the present invention and in connection with the engine illustrated in Fig. 2.

[0281] In Fig. 3 different units and elements are described in order to give an understanding of the construction of the system. Here it is noted that the filter unit is denoted with LRS. In the filter unit LRS a heating unit may be provided. Alternatively, heating may be effected in the piping leading the pre-cleaned lubricant into the filter unit. This may be provided simply by having the heating coil shown inside the buffer tank arranged in the piping between the buffer tank and the filter unit instead. This position for the heating coil is not illustrated as it will be a matter of routine for a skilled to rearrange the position of the heating coil.

[0282] Alternatively, the heating coil may be arranged in the filter unit as a pre-heating unit.

[0283] The important feature is that the heating of the pre-cleaned lubricant is effected prior to the centrifugation and filtering process.

[0284] The heating may be effected in a heat exchanger in which hot water from the cooling system of the engine is used for heating the pre-cleaned lubricant.

[0285] The heating of the lubricant is effected to temperatures between 50 and 99 °C, preferably between 75 and 85 °C.

[0286] “SCU” is a sedimentation unit, and the abbreviation means sludge collecting unit. Fig. 3 shows that a piping is used to lead an overflow of lubricant from the SCU to a buffer tank. In the buffer tank a heating unit is illustrated.

[0287] From the buffer tank the pre-cleaned lubricant is lead to the filter unit denoted “LRS” through a piping. In this piping an edge filter unit as illustrated in Fig. 4 and Fig. 5 may be inserted.

[0288] A piping is provided between the filter unit LRS and the storage tank for cleaned lubricant denoted “Cleaned LRS oil Storage Tank” The cleaned lubricant is transferred through this piping when the cleaning process in the LRS is considered to be finished. The cleaning process in the LRS comprised centrifugation and filtering which may last for several days. There are be provided a centrifuge unit for centrifuging the cleaned lubricant and filter housing for filtering the lubricant.

[0289] “Cyl. Oil Day Tank” is used to denote a lubricant supply for the lubrication system for the engine.

[0290] The cleaned lubricant is lead to a blending unit which is connected with tank for additives and different oil types. In the blending unit a blending is effected to provide an upgrade lubricant for reuse in the lubrication system.

[0291] Alternatively, a separate blending unit and mixing unit may be used. A blending unit for blending additives into the cleaned lubricant to provide an upgraded lubricant for reuse. And a mixing unit for mixing the upgraded lubricant with fresh lubricant.

[0292] Fig. 4 and Fig. 5 illustrate a metal edge filter having a coiled cartridge. The filter is an automatic metal edge filter with radial scraper cleaning. The pre-cleaned lubricant is led through this metal edge filter when entering the filter unit denoted as the LRS tank.

[0293] Filtration:

[0294] A triangular wire is wound immovably on a core element. The gap width and this the filter rating are determined by the threaded pitch. The suspension flows inward through the coiled cartridge. There is a significant increase in the cross section downstream of the narrowest gap due to the triangular geometry. Clogging is practically eliminated as a result.

[0295] Automatic cleaning:

[0296] The particles that settle on the coiled cartridge cause the differential pressure between the dirty side and the clean side to increase. If this pressure difference exceeds a (settable) limit value, a cleaning process is started. The cartridge begins to turn. The filter cake is detached for the cartridge by the scraper.

[0297] To start the cleaning process:

[0298] A cleaning process can be start in the following ways: manually, by means of a differential pressure, by means of a time switch or by means of a higher-level controller.

[0299] The functional principle of metal-edge filter illustrated in Fig. 5 is as follows. Top left shows the suspension flows tangentially into the metal-edge filter. Thereafter the suspension flows through the coiled cartridge. The particles contained in the suspension settle on the outside of the cartridge. To the to right the filtered fluid enters the clean side and exits the filter.

[0300] The cleaning process is started when the maximum differential pressure is reached or after a preset time. In top behind the broken away wall a differential gauge / switch is seen.

[0301] Top right in Fig. 5 is shown a gear motor for turning the cartridge. Alternatively, the cartridge is turned manually by means of a ratchet. The separated particles are detached by the stationary scraper. Typically, the cartridge is turned with 15-25 revolutions per minute, however also a lower rotational speed is possible. The filtration process is not interrupted.

[0302] In the bottom of the metal edge filter a collection cone is provide for the enriched particles. And a discharge may be provided periodically either manually or automatically.

[0303] Fig. 6 and Fig. 7 illustrate an embodiment for a filter unit to be used in a system according to the present invention.

[0304] In Fig. 7 different elements for the filter unit are described in order to give an understanding of the construction and the function of the unit.

[0305] Fig. 8 illustrates a centrifuge unit to be used in a system according to the present invention.

[0306] In Fig. 8 different elements for the centrifuge unit are described in order to give an understanding of the construction and the function of the unit.

[0307] Fig. 9 illustrates a transfer unit to be used in a system according to the present invention.

[0308] In Fig. 9 there is shown a common transfer unit for transferring sludge from filter unit and from an edge filter as described above to a sludge tank. The transfer unit may comprise a rotating flexible centerless spiral auger of the type described in EP 22700954.5 or EP 3,642,139 Bl.

[0309] Fig. 10 illustrates a more detailed flow diagram for an embodiment of the system according to the present invention.

[0310] Explanation to Fig. 10 is given below. In this explanation the general term “oil” is used to describe the lubricant.

[0311] The main component and structure of the filter unit is the filter batch tank (3: 1). The tank is a cylindrical vertical tank with conical bottom and flat top. The tank is constructed from steel plating and is isolated on outer surface. The isolation is protected with thin steel plating on the sides and canvas on the top. Alternatively, the insulation may be protected with aluminum plating. The tank is supported by 4 steel legs and has brackets in the top for additional top stiffening of the tank.

[0312] All other components of the filter unit are fastened / connected to the main structure / tank with one or more of following methods: welding, by bolts, by rivets, by U-bolts, cable ties, flanges, clamps, pipe thread, thread and other industrial standard methods.

[0313] The batch tank is constructed with heating element. The heating element can be heating jacket type or an internal mounted heating coil. The purpose of the heating element is to heat and maintain the temperature of the lubricant in the tank at desired temperature (often 60-90°C). Alternatively, the heating element may be a heat exchanger arranged outside the batch tank. Such heat exchanger may be used both for heating the lubricant during the filing of the batch tank and during the cleaning process. Such heat exchanger may be mounted on the outside of filter unit and are fastened / connected to the main structure / tank.

[0314] The heating media for the tank heating element: jacket type, pipe type and coil type can be either engine cooling water, steam, hot lubricant, electric heating, or other heat sources. Engine cooling water is preferred as heating media, as it is considered waste energy on most ships.

[0315] Description of filling circuit for the filter unit:

[0316] The purpose of the filling circuit is to transfer precleaned lubricant from the buffer tank via self-cleaning fine filter which may be in form of the metal edge filter explained above (3:8) to the filter batch tank (3 : 1) of the filter unit.

[0317] The filling transfer pump (3:7) is of membrane type. This pump type can handle significant amount of dirt and larger particles in the lubricant. The membrane pump is either pneumatic or electric driven. The filling transfer pump takes suction from the buffer tank and pump the lubricant into the self-cleaning fine filter (3:8), passing manual valve (3:9) and non-return valve (3: 10) The function of manual valve (3:9) is to block and secure piping during maintenance on the pump. The function of non-retum valve (3: 10) is to prevent reverse flow towards the pump.

[0318] Prior to the filling sequence the lubricant is heated with the build-in heating coil in the buffer tank or alternative with an in-line heater in the piping between buffer tank and fine filter. The lubricant is heated to desired temperature in order to lower the viscosity of the lubricant to a desired level.

[0319] A pressure transmitter (3: 11) is connected to the filter inlet, downstream of the nonreturn valve. The purpose of the pressure transmitter is to give the filter control system information of the inlet pressure to the filter. The pressure reading at filter inlet is compared to an estimated pressure on the outlet of the filter. This gives the filter control system a sufficient accurate indication of the pressure-drop over the filter. The level of cross-filter pressure drop indicates fouling or clogging level of the fine filter. This information can be used to identify need of filter cleaning.

[0320] A flushing pipe (3 : 12) is connected to the filter inlet. An automated control valve (3: 13) and non-return valve (3:14) is controlling flushing flow of relative clean lubricant from the filter main pump (3: 15) the purpose of the flushing flow of lubricant, is to flush and clean the self-cleaning fine filter (3:8) with relative clean lubricant at a later stage in the batch cleaning process. This way the self-cleaning fine filter (3:8) will be flushed with relative clean lubricant, prior to next filling sequence with relative dirty lubricant.

[0321] The flushing flow sequence is also initiated when circulation in the batch tank (3: 1) without operation of the lubricant cleaning centrifuge(s) (3:29) is desired, - e.g. during initial heating of a new batch of lubricant.

[0322] The flow of the filter main pump is adjusted from filter control system to the desired flow rate during flushing and circulation sequences.

[0323] The filter function is further described in detail below.

[0324] The outlet of the filter (3:8) is connected to the upper half of the batch tank (3: 1) via automated control valve. The purpose of valve (3: 16) is to control inlet to the batch tank.

[0325] Detailed description of self-cleaning filter

[0326] The self-cleaning filter (3:8) and (Figs. 4-7) is of the type:

[0327] Automatic metal edge filter with radial scraper cleaning.

[0328] See for functional description for Fig. 4.

[0329] The known and available “Automatic metal edge filter with radial scraper cleaning type” has in our invention been modified with an internal mounted diving tube.

[0330] Fig. 6 illustrates the known embodiment of the “Automatic metal edge filter with radial scraper cleaning type”.

[0331] Fig. 7 illustrates modified and new design for the automatic self-cleaning edge filter with diving tube and paddle switch which is utilized in our invention.

[0332] The purpose of the diving tube design is to allow pneumatic press-out of the majority of lubricant contained inside the filter. The pneumatic press-out of contained lubricant is initiated when accumulated sludge and other substance need to be discharged via the sludge outlet valve at the bottom of the filter. The press-out and sludge discharge sequence is activated either by activation of the paddle switch type Level Switch (LS) (3:20) or by due to increased lubricant pressure difference across the filter during lubricant flow. Alternatively, activations of the press- out and sludge discharge sequence are emptying of filter after ended batch tank filling sequence, ended filter flushing sequence or preset timer function which is controlled from the filter control unit.

[0333] The reason for introducing the diving tube and pneumatic press-out is to reduce the amount of relative clean lubricant inside the filter housing, prior to complete emptying or the filter housing via the sludge outlet valve.

[0334] The pneumatic press-out sequence works in the following way:

[0335] The flow of lubricant through the filter is stopped by stopping the filling transfer pump (3:7) from filter control system. The non-return valve (3: 10) is preventing backflow towards the filling transfer pump. At this stage the lubricant outlet valve (3 :16) is still open and the sludge outlet valve (3: 17) is closed.

[0336] Now inlet valve for compressed air (3: 18) opens and compressed air with relatively high pressure flows through the non-return valve (3: 19) and into the inlet port of the filter housing. The incoming compressed air will accumulate in the top of the filter housing, due to its relative low density. The compressed air will create a downward force on the lubricant surface, thus driving the lubricant out of the housing, via the diving tube and lubricant outlet valve (3:16)

[0337] When the lubricant level inside the filter housing reaches the lower end of the diving tube, compressed air will start to escape via the diving tube. The press-out sequence is now completed.

[0338] After a preset time period controlled by the filter control system, the lubricant outlet valve (3: 16) will close. Now air pressure is built up inside the filter housing. Now the sludge outlet valve (3: 17) will open and allow accumulated sludge and other substances plus the remaining lubricant to flow out of the filter housing towards the sludge tank. The air pressure inside the filter housing will assist to drive the accumulated sludge and other substances plus the remaining lubricant out of the filter housing.

[0339] After a preset time delay controlled by the filter control system, the press-out and emptying sequence will be ended.

[0340] This means: Closing of inlet valve for compressed air, closing of sludge outlet valve and opening of lubricant outlet valve.

[0341] The filter is now ready for lubricant flow again and lubricant flow via starting the filling transfer pump (3:7) from filter control system.

[0342] In this embodiment of the present invention is utilizing a paddle switch type Level Switch (LS) (3:20).

[0343] The purpose of the paddle switch is to detect when a certain level of sludge and other substance with relative high density and or viscosity has accumulated in the lower part of the filter housing. The paddle switch works by having a sensing paddle slowly rotating inside the filter housing or alternative in the pipe between filter housing and sludge outlet valve. The paddle switch is calibrated in a way so it will detect increased resistance or torque in rotating its paddle. The rotating paddle will be exposed to increased rotating torque when the paddle is rotating in substances with higher density and viscosity, compared to the lubricant. Therefore, rising level of sludge will be detected when it reaches the rotating paddle. The paddle switch will send signal to the filter control unit.

[0344] Now follows a description of tank sludge trap and sludge removal system and of primary cleaning circuit - centrifuge(s).

[0345] The main component(s) in the primary lubricant cleaning circuit is one or more lubricant cleaning centrifuge(s) (3:29) also called centrifugal filter or centrifugal lubricant spinners. Other names are also used for the same equipment type.

[0346] This type of lubricant cleaning centrifuge(s) is characterized by having the spinning bowl driven by liquid (lubricant) flow (flow driven) The lubricant cleaning centrifuge(s) will collect dirt and particles from the lubricant on a paper lining inserted in the spinning bowl.

[0347] Different embodiments of the filter can utilize alternative types of lubricant cleaning centrifuge(s) like mechanical driven centrifuges or separators, decanter, force or motor driven centrifuge and separators.

[0348] The filter main pump (3: 15) takes suction from the filter batch tank (3: 1) via suction strainer (3:21), inlet valve (3:22) and suction piping (3:23). The suction piping (3:23) is connected with following equipment:

[0349] -Manual pressure indicator (Manometer) for manual reading of the suction pressure.

[0350] -Pressure switch (PS) (3:25) for monitoring of low pump suction pressure in case of clogged suction strainer.

[0351] -Temperature transmitter (TT) (3:26) of PT100 type for monitoring of the lubricant temperature.

[0352] -Manual temperature indicator (TI) (3:27) for manual reading of lubricant temperature. -Manual outlet valve to secondary cleaning circuit (3:28) (see detailed description).

[0353] The filter main pump (3: 15) is of the triple screw type in our embodiment of the filter. Other Embodiments can utilize other types of pumps.

[0354] The motor of the filter main pump (3: 15) is electrical coupled to a variable frequency drive (VFD) in the filter control system. The VFD allows the filter control system to adjust the speed of the pump and thereby the flow of the pump. The adjustment of pump flow can maintain a desired bowl speed of the flow driven centrifuge. Other situations of pump flow adjustments could be during filter flushing or batch tank circulation.

[0355] The filter main pump (3: 15) delivers lubricant flow to the lubricant cleaning centrifuge^) (3:29) via the 3-way valve (3:30).

[0356] The lubricant flows by gravity from the lubricant cleaning centrifuge(s) back in the top of the filter batch tank. The lubricant cleaning centrifuge(s) are equipped with bowl speed transmitters (ST).

[0357] The bowl speed feedback to the filter control system is used to control the speed and flow of the filter main pump (3: 15) to obtain desired bowl speed of the centrifuges.

[0358] The 3-way valve (3:30) is able to close for the lubricant flow from the pump and at the same time drain lubricant from the lubricant cleaning centrifuge(s) (3:29) back to the upper half of the filter batch tank (3: 1). The filter main pump (3: 15) is stopped prior to this draining sequence.

[0359] The centrifuge drain function via 3-way valve (3:30) is utilized for fast draining of the lubricant cleaning centrifuge(s) (3:29).

[0360] Fast draining of the lubricant cleaning centrifuge(s) is desired prior to maintenance and cleaning of the centrifuges.

[0361] Fast draining is also desired when bowl inertia-based sludge-cake measurements are carried out.

[0362] The lubricant cleaning centrifuge(s) are mounted in a lower recess spill tray (3:32) on top of the filter batch tank (3: 1) The spill tray is fitted with a level alarm switch (LS) (3:33) of the float type. The spill tray also works as foundation or mounting base for the centrifuges. Vibration sensor(s) (VS) (3:34) can be mounted on the spill tray / centri- fuge base in order to monitor if unbalanced operation of the centrifuges will create abnormal vibrations.

[0363] The centrifuges are normally covered with a hinged safety cover. The cover incorporates one or more proximity type limit switch(s) (3:35). The limit switch monitors the distance to the assembly clamp of the centrifuge(s)

[0364] The purpose of the limit switch(s) (3:35) is to hinder operation of the centrifuges in case the centrifuge(s) are not correctly assembled (assembly clamp not in correct position) or in case the hinged safety cover is swinged away from the centrifuge. The filter control system will immediately stop the filter main pump (3: 15) and thereby flow to and operation of the flow-driven centrifuge(s), in case safety cover and / or centrifuge assembly clamp not in correct position. This safety function prevents operation of centrifuges if they are incorrect assembled, or safety cover is open. The safety cover also prevents opening / disassemble of centrifuges during operation.

[0365] Fig. 8 shows an embodiment of a centrifuge to be described in more detail.

[0366] Lubricant is introduced into the separator bowl (6: 1) at pump lubricant pressure through holes drilled in the vertical hollow spindle (6:2) and via the accelerator channels in the bearing distributor.

[0367] The bowl then fills up and lubricant overflows into the turbine where it exits the bowl via the four speed turbine channels and then out via the nozzles (6:3). This in turn rotates the bowl, generating the centrifugal force required to remove the contaminants from the lubricant.

[0368] The contaminants migrate towards the outside of the bowl where they are deposited on a removable lubricant resistant insert (6:4). The cleaned lubricant migrates towards the center of the bowl, where it is expelled by the nozzles in the turbine, thus perpetuating the cycle.

[0369] Unlike conventional centrifugal spinners / separators, separator commercially available from IOW Group uses bowl discs (6:5) to increase the efficiency of separation, dramatically reducing the time that contaminants can stay in the lubricant.

[0370] Above-described centrifugal spinner / centrifuge is commonly used with various marine engines, to clean the internal circulating lubricant of the engine.

[0371] The method according to the present invention will in the LRS system require clean- ing / opening of the centrifuge much more often than for conventional engine system oil cleaning. The dirt / sludge concentration in the initial LRS lubricant is simply much higher. In the conventional system oil cleaning application, there might be several weeks between each cleaning of the centrifuge bowl. In our LRS application for cleaning lubricant (lube oil) the initial cleanings of the separator bowl will have short intervals of only few hours.

[0372] It should also be mentioned that it is very important to clean the centrifuge bowl, before the accumulated sludge layer / sludge cake (6:6) becomes too thick due to collection of too much sludge. Too much collected sludge in the bowl will reduce efficiency of the centrifuge. Furthermore, sludge will accumulate inside the disc-stack of the bowl when over-filled with sludge. Sludge accumulation in the disc-stack, is not desirable, as it will prolong the time needed for manual cleaning enormously.

[0373] It is therefore desirable to have a system to measure / monitor the actual sludge accumulation level in the bowl.

[0374] In specific embodiments of the LRS system, we take advantage of two new methods for monitoring the actual sludge accumulation level in the bowl.

[0375] A: inertia-based sludge cake measurements

[0376] B: bowl -weighing based sludge cake measurements.

[0377] Inertia-based sludge cake measurements is based on the fact that the more relative heavy sludge accumulated in the bowl - the more inertia will the spinning bowl have. The centrifuge is fitted with bowl speed transmitters (ST) (6:7).

[0378] By stopping the LRS main pump (3: 15) and draining the centrifuge via drain function via 3-way valve (3:30) during centrifuge operation, - the bowl will lose its driving lubricant flow and at the same time have its internal lubricant drained.

[0379] The bowl will continue rotating for some time (run-down) due to the inertia of the bowl. The more additional mass (wight) of accumulated sludge in the bowl - the more inertia. This means longer run-down time for a bowl almost filled with sludge, than for a clean bowl. The LRS control system will carry out a “base line” measurement of the run-down time, every time a cleaned bowl is placed in the centrifuge. The LRS control system is then comparing this “base line” measurement, with measurements taken of the working bowl at various intervals. The increased run-down time gives the LRS control system information of the actual sludge accumulation level inside the bowl. This information enables the LRS control system inform operator of cleaning advice and to stop centrifuge operation before the centrifuge over-fills.

[0380] Bowl-weighing based sludge cake measurements is based on actual weighing of the bowl at stillstand.

[0381] In one embodiment the standard centrifuge is modified with a lifting device for the bowl.

[0382] The bowl lifting device may be a pneumatic actuator (6:8). Alternatively, the actuator can be of any other type. The Actuator extends through an opening in the bottom base of the centrifuge.

[0383] The bowl of the centrifuge has a vertical-axial clearance (6:9) of app. 3 mm during stillstand. This means the bowl can be lifted app. 3 mm with insignificant friction as it slides in its well lubricated bush bearings (6: 10).

[0384] The lifting device is designed to lift the bowl app. 50% of bowl vertical clearance e.g. 1,5 mm.

[0385] The lifting device is designed in a way, so the actuator will push against an electronic weight cell (6: 11) during the bowl lifting. This means the weight cell is carrying the mass of the bowl + minor mass of the actuator arrangement.

[0386] The LRS control system will carry out a “base line” measurement of the bowl weight, every time a cleaned bowl is placed in the centrifuge. The LRS control system is then comparing this “base line” measurement of empty bowl, with measurements taken of the bowl at various intervals. The increased weight gives the LRS control system information of the actual sludge accumulation level inside the bowl. This information enables the LRS control system inform operator of cleaning advice and to stop centrifuge operation before the centrifuge over-fills.

[0387] The system is designed so the weight cell is “zero adjusted” when the lifting rod (6: 12) of the actuator is lowered, thus not carrying the weight of the bowl.

[0388] The system is also programmed with weight limits, in order to detect error measurements.

[0389] Alternatively, it is possible to carry out a manual weighing of the centrifuge bowl on a general electronic scale outside the LRS. The measured weight is then entered into an HMI panel on the LRS unit. These entries of bowl weight form the basis for calculating how long time the centrifuge shall run in the next period - before it is deemed to have an amount of built-up sludge which requires emptying.

[0390] Fig. 9 illustrates an embodiment of a tank sludge trap and a sludge removal system. This will be described in further detail.

[0391] The sludge trap arrangement of the LRS tank consist of two pneumatic actuated ball valves in seria at the bottom outlet from the conical bottom of the LRS tank (7: 1).

[0392] An intermediate pipe (7:2) is connecting the upper sludge trap valve (7:3) with the lower sludge trap valve (7:4).

[0393] During normal operation the upper valve (7:3) is kept open and the lower valve (7:4) is kept closed. Over time will relative heavy sludge parts of the LRS lubricant settle by gravity down towards the conical bottom of the LRS tank and further down through the open upper valve (7:3).

[0394] Sludge will start to collect on top of the now closed lower valve (7:4). More sludge will settle, and the sludge level will start to rise in the intermediate pipe (7:2).

[0395] When the rising sludge level reach the slow rotating paddle of the paddle level switch (7:5) an increased paddle turning resistance is sensed by the paddle level switch (7:5) due to the relative high density and viscosity of the sludge.

[0396] The paddle level switch (7:5) sends signal to the LRS control system about rising sludge level in the intermediate pipe.

[0397] The LRS control system will then initiate following sequence to remove the collected sludge:

[0398] 1 : Upper valve closes

[0399] 2: Lower valve opens

[0400] 3: Solenoid activated air valve (7:6) opens for compressed air at app. 5-10 bar pressure.

[0401] The incoming compressed air will create over pressure in upper part of the intermediate pipe, thus pushing the collected sludge down through the (now open) lower valve (7:4) and further down into the auger cleaned sludge drainpipe (7:7). The sludge drainpipe is having a motor rotated flexible auger to facilitate forced flow of the sludge towards sludge tank (7:8). In other embodiments, the sludge drainpipe can lead the sludge to replaceable containers, e.g. a 210L steel drum.

[0402] When the sludge trap emptying sequence is completed after preset time duration (app. 30 sec.) all 3 valves will change back to their normal sludge collecting position. The motor of the auger cleaned sludge drainpipe (7:7) will run as long as the lower valve (7:4) is open and continue app 5 min. after closing of the lower valve. This to ensure that the drainpipe is cleaned and drained completely before the auger motor is stopped.

[0403] The sludge rising sensor system and sludge emptying system for the self-cleaning filter (7:9) is identical to the above described - only difference is that the filter only having lower sludge valve and no upper valve. Reason for this is that it is desired to empty all of the remaining lubricant in the filter housing- together with sludge during the emptying sequence. Also here the lubricant and sludge is pushed down and out by help of compressed air entering via solenoid valve (7: 11).

[0404] The system comprises a secondary cleaning circuit which comprise paper or cellulose based filter(s). This secondary cleaning circuit will be described in further detail.

[0405] The main component of secondary cleaning circuit is a standard CJC filter, e.g. CJC HDU 27 / 54, which is commercially available marine fine filter with cellulose based filter inserts. This filter is available from C.C. Jensen A / S.

[0406] The purpose of this secondary cleaning circuit is mainly to ensure sufficient cleaning level of the LRS lubricant.

[0407] This type of filters is known to catch and absorb particles with size above app. 2 micron. This kind of filters are also absorbing water in the lubricant - until the filter insert is saturated with water. The filter insert will also become saturated with particles at some time.

[0408] In both cases the filter inserts after being saturated with particles or water will “clog”. This means that the flow through the filter insert will be restricted. The restricted flow will show itself in form of increased pressure drop across the filter.

[0409] In an embodiment of the LRS system the filter is working as a kind of checking and guaranteeing function.

[0410] The purpose of this filter is to circulate the LRS lubricant through it during the last day of the cleaning process. Such cleaning process normally takes days. The intension is that the primary cleaning circuit should remove most particles. Only after the primary cleaning is conducted the second cleaning circuit is started. This will expose the filter inserts of the filter to minimal particles - thus avoid early saturation and replacement of the relative expensive filter inserts. Most of the water in the lubricant cleaned in the LRS is removed by a dryer system described later.

[0411] The LRS control system will start a separate lubricant feed pump (3:36), e.g. a CJC feed pump. Bypass / air bleeder valve (3:42) will be opened from the LRS control system.

[0412] The initial flow through the bypass / air bleeder valve (3:42) has 2 purposes: First purpose:

[0413] 1- to allow air to escape from the top of the filter dome in case there is air in the dome (e.g. after replacement of filter inserts). The supply pump will fill the space between the dome and the filter inserts and eventually press out remaining air through the connection in the top of the dome - and further through the bypass / air bleeder valve (3 :42) and via manual ball valve (3:41) back to the LRS tank.

[0414] The feed pump (3:36) takes suction from the inlet pipe of the LRS main pump (3: 15), via manual ball valve (3:28) and delivers lubricant via non-return valve (3:37) and into the filter inlet port which is located in the bottom of the filter housing and distribute the incoming lubricant in the space between dome inner surface and filter inserts outer surface.

[0415] Second purpose:

[0416] 2- to continue this bypass / air bleed circulation until the filter housing and filter inserts as reached same warm temperature as the incoming LRS lubricant (often 60-90°C)

[0417] Reason for this is that the lubricant inside the filter (e.g. caused by ambient cooling to the non-circulating filter) will have relative high viscosity compared to the same lubricant at higher temperature. Circulating the relative cold lubricant through the filter inserts would result in very high pressure drop across the filter inserts. This is not desirable - as it might overload the supply pump and cause damage to the filter inserts.

[0418] When the circulation through the bypass / air bleeder valve (3:42) has continued for a fixed time (app. 30 minutes) the bypass / air bleeder valve (3:42) will be closed from the LRS control system.

[0419] The circulating lubricant is now forced through the filter inserts and back to the LRS tank. This process will continue for app. 12-24 hours.

[0420] During the process time the inlet pressure to the filter is monitored by LRS control system via pressure transmitter (3:38). The pressure signal is compared with an estimated pressure of the filter outlet / LRS tank inlet and gives sufficient accurate indication of the pressure drop across the filter.

[0421] The LRS control system will allow very minor increase in pressure drop across the filter during this 12 to 24-hour process.

[0422] No or minor increase in the pressure drop across the filter indicates that the LRS lubricant already is sufficient cleaned for particles and water - otherwise would an increased saturation of the filter inserts by particles and / or water result in increasing pressure drop.

[0423] In the following the PI diagram in Fig. 11 is explained in more detail.

[0424] The cleaning process starts with filling pre-cleaned lubricant into the LRS tank 99. 100 indicates outlet from the buffer tank illustrated in Fig. 3. A Pump 101 is used for leading the pre-cleaned lubricant through a heat exchanger 102 receiving heating water from an engine cooling system 103. Lubricant flows through a valve 115 and vis a filter 105 and a valve 114 is closed and leaves the heat exchanger via an outlet 104 and via an inlet 104 the lubricant enters the self-cleaning filter 105. The LRS tank 99 may have a capacity of 2,000 liter.

[0425] The lubricant is led through valves 106 and 107 to the LRS tank 99 which is filed to a predetermined level. Now pump 100 is stopped and valve 101 is closed. The lubricant in the LRS tank 99 is now approximately 50-60 °C.

[0426] The filter 105 is still filled with lubricant. The valve 115 is closed the valve 106 is maintained in open position. A valve 108 is opened which is connected with one of several air supplies 109. Hereby the lubricant is pressed through a pipe 110 and then the valve 106 is closed. Now a valve 111 is opened and sludge is led to a transfer unit 112 comprising a rotating flexible centerless spiral auger 113 which is also disclosed in Fig-9.

[0427] Also the heat exchanger 102 is emptied. Valves 114 and 115 is closed and valve 116 is opened and connects an inlet 117 to one of the air supplies 109. A valve 118 is opened and pre-cleaned lubricant is blown back to the buffer tank. Now the heat exchanger 102 and the self-cleaning filter 105 are emptied. The system is now ready to perform the batchwise cleaning.

[0428] Valves 106, 115 and 107 are opened and valve 114 is closed and a pump 98 is started with a low speed in the initial phase of the cleaning. Circulation is now effected through the self-cleaning filter 105 in an initial phase through the self-cleaning filter 105 and the heat exchanger 102. This circulation may be effected in a couple of hours. Again, the self-cleaning filter 105 is shot off and emptied as described above and the cleaning process continues with a centrifugation. Now the temperature will typically have raised to app 85 °C.

[0429] Valves 106, 107 and 115 is closed and valve 114 is now opened. Hereby the lubricant flows through a piping 119 into the centrifuge 120. The lubricant flows through a pipe 121 into the LRS tank 99. The lubricant flows into a container 122. Where a drying may be effected as dry air is blown in via a pump 123. Air is drawn out via a mist catcher 124 and through an air cooler 125 from which is led to a cyclone 126. In the cyclone moist is separated via an outlet 127.

[0430] In the centrifuge 120 a bowl in form of a metal cylinder rotates with app 4.000 rpm. The metal cylinder is covered with an inner paper liner. The sludge is built up on the inner side as illustrated in Fig. 8. To remove the accumulated sludge the circulation through the centrifuge 120 is stopped. This process is repeated in several days.

[0431] After finalizing the centrifugal filtering in the centrifugal filter, the lubricant shall be mechanical filtered in the mechanical filter 134 comprising a paper filter system.

[0432] This cleaning in mechanical filter 134 is typically started up in the last 24 hours of the cleaning period. Typically, the centrifuge 120 continue the operation at the same time as cleaning through the mechanical filter 134 is in progress.

[0433] In the control unit a monitoring system is provided which monitors the counter pressure in front of the filter 134 using a pressure transmitter connected to the piping between the pump 128 and the filter 135. By monitoring this pressure while pumping lubricant through the filter 134, it is monitored if the filter is about to stop and need to be changed.

[0434] At the same time an important measurement is obtained. It is monitored whether the back pressure becomes unrealistically low, e.g. if an operator tries to drive the system without filter inserts in the filter 134. There will be a very low back pressure (pressure drop over the filter) if there are no filter inserts in the filter 134.

[0435] The mechanical filter 134 is used to ensure that the lubricant is sufficiently finely filtered before it is pumped further to the clean lubricant tank which is illustrated in Fig. 3. The control unit prevents a bypass of the filter 134 based on the measurement of the back pressure.

[0436] A pump 128 ensures the circulation through the mechanical filter 134 and through a piping 130 between the mechanical filter 134 and the LRS tank 99.

[0437] A valve 129 is provided for a possible circulation with a by-pass of the filter system in situation where the lubricant may have low viscosity and there is high risk of blocking the mechanical filter 134. This is always done when starting up the filter as it has lower temperature than the lubricant in the LRS tank 99. Accordingly, there will otherwise be a high pressure drop across the filter 134 until the lubricant in the filter and filter are warmed up.

[0438] The pump 119 continues to run during this process. The pump 119 will have a flow being several times higher than the flow through the pump 128. The difference may be 4-8 times or more.

[0439] After the mechanical filtering is stopped and the lubricant in the LRS tank 99 is finally cleaned and will be led to the tank for cleaned lubricant which is illustrated in Fig. 3. In the bottom of the LRS tank 99 an outlet for sludge is provided. Between the two valves 131 and 132 a connection 133 is provided for connection to one of the air supplies 109 whereby the evacuation of sludge by the auger 113 may be assisted by pressurized air. This "sludge trap" at the bottom of the LRS tank 99 works during the entire cleaning period or when there is lubricant in the LRS tank 99. In normal operation a small volume of lubricant (approximately 0.51) between valve 131 and 132 is emptied out one or more times a day. Thus, valve 131 is normally open and valve 132 is normally closed. In this way, sludge and heavy particles can settle down with valve 132. When emptying, the valve 131 is closed and the valve 132 is opened at the same time as air is supplied from the air supplies 109.

Claims

CLAIMS1. A method of recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine, which method comprises the steps of:- draining lubricant from a piston underside,- collecting drained lubricant,- recovering drained lubricant by steps comprising- sedimentation in a sedimentation unit thereby pre-cleaning the drained lubricant for providing a pre-cleaned lubricant,- removing impurities in a filter unit and in a centrifuge for providing a filtered lubricant, and- reusing drained and recovered lubricant for lubricating the engine, characterized in that the method comprises the steps of:- draining lubricant comprises draining lubricant away via:A: draining lubricant from a scavenge air receiver andB: draining lubricant from piston rod stuffing boxes of the engine.

2. A method of recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and with a lubrication system comprising- a lubricant supply,- a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at positions on the perimeter during injection phases,- a lubricant supply conduit connecting the lubricant supply with the lubricant injectors, the engine further comprising- a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors, wherein each lubricant injector comprises- an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,- a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase,wherein the method comprises the steps of- draining lubricant from a piston underside,- collecting drained lubricant,- recovering drained lubricant by steps comprising- sedimentation in a sedimentation unit thereby pre-cleaning the drained lubricant for providing a pre-cleaned lubricant,- removing impurities in a filter unit and in a centrifuge for providing a filtered lubricant, and- reusing drained and recovered lubricant for lubricating the engine, characterised in that- the step of draining lubricant further comprises draining lubricant away via:A: draining lubricant from a scavenge air receiver andB: draining lubricant from piston rod stuffing boxes of the engine.

3. The method according to claim 1 or 2, wherein the method comprises that:- the step of sedimentation in a sedimentation unit comprises a sedimentation of sludge in the sedimentation unit,- the step of removing impurities comprises- leading the pre-cleaned lubricant to the filter unit for a finally cleaning of the precleaned lubricant, which finally cleaning comprises centrifugal filtering in a centrifugal filter and filtering in a mechanical filter e.g. in a cellulose-based filter,- heating the pre-cleaned lubricant prior to centrifugation and filtering in the filter unit during the filtering step, and that the method comprises the step of controlling, by a controller, an automated sequence of steps for collecting, cleaning and reusing lubricant drained out from drain systems of the engine.

4. The method according to any one of claim 1 - 3, wherein the method further comprises the step of- upgrading the filtered lubricant by adding additives and thereby providing the upgraded lubricant for reuse as lubricant.

5. The method according to any one of claim 1 - 4, wherein the method further comprises the step of- the step of sedimentation comprises a sedimentation of sludge in a sedimentation unit comprising a barrel acting as a replaceable cartridge containing segregated particles and sludge and creating an overflow of pre-cleaned lubricant from the replaceable cartridge, which overflow of pre-cleaned lubricant is then led to a buffer unit,- exchanging the replaceable cartridge when a predetermined level of sludge is accumulated in the replaceable cartridge,6. The method according to claim 5, wherein the method comprises the step of heating the pre-cleaned lubricant before entering the filter unit, which heating is effected either in the buffer unit or in a exchanger arranged in the piping between the buffer unit and the filter unit or in a pre-heating unit in the filter unit.

7. The method according to any one of claims 1 - 6, wherein the method comprises the steps of- mixing the upgraded lubricant with fresh lubricant to provide a blended lubricant and- leading the blended lubricant to a lubricant supply of a lubrication system.

8. A method of recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine, wherein:- lubricant has been drained from a piston underside space, scavenge air receiver and piston stuffing boxes of the engine,- lubricant has been collected,- lubricant has been pre-cleaned by sedimentation in a sedimentation unit for providing a pre-cleaned lubricant, characterised in that the method comprising:- leading the pre-cleaned lubricant to a filter unit comprising a centrifuge and a mechanical filter e.g. a cellulose-based filter and- finally cleaning of the pre-cleaned lubricant by centrifugal filtering in a centrifugal filter and filtering in the mechanical filter.

9. The method according to claim 8, wherein the method comprising:- leading the pre-cleaned lubricant as an overflow from the sedimentation unit to a buffer unit- leading the pre-cleaned lubricant batchwise from the buffer unit to the filter unit.

10. The method according to claim 8 or 9, wherein the method comprising:- heating the pre-cleaned lubricant prior to centrifugation and filtering in the filter unit.

11. The method according to any one of claims 8 - 10, wherein the method comprising: -leading the pre-cleaned lubricant through an 30-130 Micron self-cleaning edge filter when entering the filter unit.

12. The method according to any one of claims 8 - 11, wherein the method comprising:- heating is effected by using the engine cooling water in a heating unit to provide at heating of the pre-cleaned lubricant to a temperature between 50°C and 99 °C, preferably between 75°C and 85 °C.

13. The method according to any one of claims 8 - 12, wherein the method comprising:- controlling, by a controller, an automated sequence of steps for cleaning the lubricant drained out from the engine.

14. The method according to any one of claims 8 - 13, wherein the method comprising:- monitoring sludge accumulation level of a sludge cake built up in the centrifuge bowl, which monitoring may be effected as inertia-based sludge cake measurements or bowlweighing based sludge cake measurements and- stopping and emptying the centrifuge bowl at predetermined levels of sludge accumulation before the centrifuge over-fills.

15. The method according to claim 14, wherein the method comprising:- cleaning the batch in a process taking 5-7 days,- stopping and emptying the centrifuge bowl when initiating cleaning of a batch is effected at short intervals of only few hours, typically at intervals between 3 and 7 hours but even as low as every second hours.

16. A system for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine, the which system comprises:- a collecting system for collecting drained lubricant from a piston underside,- a recovering system for recovering the drained lubricant and which recovering system comprises a sedimentation unit and a filter unit,- a lubrication system for reusing the drained and recovered lubricant for lubricating the engine, characterized in that the collecting system further comprisesA: a drain system for draining lubricant from a scavenge air receiver andB: a drain system for draining lubricant from piston rod stuffing boxes of the engine.

17. A system for recovering lubricant when lubricating a large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder and which system comprises- a lubricant supply,- a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at various positions on the perimeter during injection phases,- a lubricant supply conduit connecting the lubricant supply with the lubricant injectors,- a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors,- a computer to which the controller is connected, wherein each injector comprises- an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,- a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase when using the engine in cyclic operation, wherein the engine in the injection phase provides pressure-liquid to the lubricant supply conduit, wherein the system further comprises:- a collecting system for collecting drained lubricant from a piston underside,- a recovering system for recovering the drained lubricant, which recovering system comprises a sedimentation unit and a filter unit and- a lubrication system for reusing the drained and recovered lubricant for lubricating the engine, characterized in that the collecting system further comprisesA: a drain system for draining lubricant from a scavenge air receiver andB: a drain system for draining lubricant from piston rod stuffing boxes of the engine.

18. The system according to claim 16 or 17, wherein the sedimentation unit comprises:- a sedimentation unit for sedimentation of sludge and providing an overflow of lubricant from the sedimentation unit, and wherein the filter unit comprises- a centrifuge and a mechanical filter e.g. a cellulose-based filter, and- a heating unit for heating the pre-cleaned lubricant in the filter unit during the filtering, and- a blending unit which is connected with at least one additive supply, and which is intended for upgrading the filtered lubricant by adding additives from the additive supply into the filtered lubricant and thereby providing the upgraded lubricant for reuse.

19. The system according to claim 18, wherein the recovering system further comprises- a heating unit for heating the overflow of lubricant from the sedimentation unit.

20. The system according to any one of claims 16 - 19, wherein the system comprises:- a mixer unit for blending the upgraded lubricant with fresh lubricant to provide a blended lubricant and- transport means for leading the blended lubricant to a lubricant supply of a lubrication system.

21. The system according to any one of claims 16 - 20, wherein the system comprises a controller for controlling an automated sequence of steps for collecting, cleaning and reusing lubricant drained out from drain systems of the engine.

22. A large combustion engine, for example a large slow-running two-stroke engine comprising a cylinder with a liner and a reciprocal piston having piston rings establishing contact with the liner inside the cylinder, and with a system comprising- a lubricant supply,- a plurality of lubricant injectors distributed along a perimeter of the cylinder for injection of lubricant into the cylinder at various positions on the perimeter during injection phases,- a lubricant supply conduit connecting the lubricant supply with the lubricant injectors, - a controller for controlling the amount and timing of the lubricant injection by at least one of the lubricant injectors,- a computer to which the controller is connected, wherein each injector comprises- an inlet port flow-connected to the lubricant supply conduit for receiving lubricant from it,- a nozzle with a nozzle aperture extending into the cylinder configured for injecting lubricant from the inlet port into the cylinder in the injection phase when using the engine in cyclic operation, wherein the engine in the injection phase provides pressure-liquid to the lubricant sup- ply conduit, wherein the system is characterised in that the engine further comprises the system according to any one of the claims 15 - 20.

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