Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M163/00—Lubricating compositions characterised by the additive being a mixture of a compound of unknown or incompletely defined constitution and a non-macromolecular compound, each of these compounds being essential
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/02—Hydroxy compounds
  • C10M2207/023—Hydroxy compounds having hydroxy groups bound to carbon atoms of six-membered aromatic rings
  • C10M2207/027—Neutral salts thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/02—Hydroxy compounds
  • C10M2207/023—Hydroxy compounds having hydroxy groups bound to carbon atoms of six-membered aromatic rings
  • C10M2207/028—Overbased salts thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/14—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to carbon atoms of six-membered aromatic rings
  • C10M2207/144—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to carbon atoms of six-membered aromatic rings containing hydroxy groups
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/26—Overbased carboxylic acid salts
  • C10M2207/262—Overbased carboxylic acid salts derived from hydroxy substituted aromatic acids, e.g. salicylates
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2223/00—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions
  • C10M2223/02—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions having no phosphorus-to-carbon bonds
  • C10M2223/04—Phosphate esters
  • C10M2223/045—Metal containing thio derivatives
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2010/00—Metal present as such or in compounds
  • C10N2010/04—Groups 2 or 12
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/02—Pour-point; Viscosity index
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/52—Base number [TBN]
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/25—Internal-combustion engines
  • C10N2040/252—Diesel engines

Definitions

• This invention relates to lubrication methods and in particular to methods for lubricating two-stroke, diesel crosshead engines.
• Two-stroke, diesel crosshead engines are compression ignition engines in which each piston rod is connected to the crankshaft by a crosshead bearing (sometimes also just referred to as a crosshead). Such engines are usually used in marine applications and sometimes in land-based power generation plants.
• the cylinder liner is lubricated by a cylinder oil which lubricates the inner walls of the cylinder and the piston ring pack and controls corrosive and mechanical wear.
• the cylinder oil also removes deposits from the outer surfaces of the pistons, and from the piston rings and/or cylinder liners.
• the crankcase In two-stroke, diesel crosshead engines, the crankcase is lubricated with a system oil which lubricates the crankshaft, the crosshead, the main bearings, the crosshead bearings and the camshaft and protects the crankcase against corrosion.
• the system oil also cools the piston undercrown and removes deposits from the undercrown area.
• a barrier sometimes referred to as a stuffing box
• contamination of the system oil for example by un-burnt fuel, by by-products of the combustion of the fuel, by used cylinder oil which may have leaked through the stuffing box, or by water which may have leaked from the engine's cooling system.
• system oils do not have high base numbers or a high neutralisation capacity because the system oil is not generally exposed to acidic by-product gases produced by combustion of the diesel fuel.
• system oils do not have very high contaminant-handling performance because generally they are not expected to be subject to any great extent to contamination by un-burnt fuel etc. because of the separation provided by the stuffing box.
• current experience indicates that this is not always the case.
• system oils may additionally contain some anti-wear, corrosion-inhibition and/or anti-oxidancy additives, they are generally not well suited to cope with the higher levels of contamination of system oil which are increasingly being encountered in modem crosshead engines, where such contamination may include unburnt fuel, by-products of the combustion of the fuel, used cylinder oil and/or water.
• system oil in the engine which may require correction is viscosity. This commonly increases during operation of the engine. Usually, partial replacement of the system oil in the engine with fresh system oil of the same viscosity as that previously charged to the engine is used to correct this viscosity increase. However, it is also known, but not common, to use a system oil (sometimes referred to as a cutter oil) which has a viscosity which is less than that of the system oil previously charged to the engine. This may reduce the extent of replacement of the system oil which is required to correct the viscosity increase.
• a system oil sometimes referred to as a cutter oil
• ATLANTA MARINE 20 (trade mark) is said to be used to top up crankcase lubrication of slow 2 stroke crosshead diesel engines when the viscosity and the BN of the in service system oil is higher than the warning limit, due to contamination by cylinder lubricant through the stuffing box. It is said that it can be used to regularly top up in order to decrease and to maintain the viscosity at an acceptable level or to replace a part of the in service oil in order to drastically decrease the viscosity below the warning limit.
• ATLANTA MARINE 20 has a base number of only 2.
• a top-up system oil which is added to the engine may have a lower viscosity than that previously charged to the engine, it will generally have the same additives, and in the same concentrations, as those in the system oil which was previously charged to the engine.
• a system oil of the desired viscosity but with no, or relatively low, additive content may be used, for example a base oil or a hydraulic oil.
• the range within which the viscosity of the system oil in the engine must be maintained is usually quite wide and may permit the viscosity of the system oil in the engine to be allowed to rise considerably above the viscosity of the system oil previously charged to the engine.
• fuel economy benefits may be obtained if the viscosity of the system oil in the engine can be maintained at a low value within the allowable range.
• EP-1728849-A a typical system oil has a viscosity at 100 °C of 11.5 cSt and a total base number of 5 mg KOH/g (ASTM 2896-98).
• EP-1728849-A seeks to provide a method of lubricating a cylinder liner and a crankcase in a marine diesel crosshead engine with the same lubricant.
• This lubricant is said to comprise at least 40 mass % of an oil of lubricating viscosity, at least one detergent, at least one dispersant and at least one anti-wear additive, the lubricating oil composition having a BN, as measured using ASTM D 2896-98, of 10 to 55, preferably 20 to 45, mg KOH/g.
• Lubricating a crosshead engine with the same lubricant used as both cylinder oil and system oil has disadvantages, one of which at least, is that the properties of that lubricant will be a compromise of properties suited for cylinder oil duties and properties suited for system oil duties, and the oil is therefore not optimised for either duty.
• the lubricating oil composition preferably has a viscosity at 100 °C of 15 to 21 cSt. Such a high viscosity in a system oil is expected to cause poorer fuel economy than would be obtained, for example with a typical system oil having a viscosity at 100°C of 11.5 cSt.
• a method of lubricating a two-stroke, diesel crosshead engine which method comprises lubricating the engine with a cylinder oil and with a system oil, which oils are different from each other, characterised in that the system oil is an SAE 20 or SAE 30 oil, has a total base number of at least 10 mg KOH/g and comprises :-
• the present invention solves the technical problems identified above by the use of a system oil comprising at least one anti-wear additive and having a defined performance and a defined base number. This can mitigate the problem of increased contamination (for example leaked fuel, combustion debris and by-products, and/or waste cylinder oil) in the system oil which is encountered by modem two-stroke, diesel crosshead engines, and which is usually the dominant underlying cause of the viscosity increase.
• a system oil comprising at least one anti-wear additive and having a defined performance and a defined base number.
• the present invention may be particularly beneficial when the system oil in the engine is partially replaced and/or topped-up to control the properties of the system oil in the engine, for example to control the viscosity of the system oil in the engine.
• a method of lubricating a two-stroke, diesel crosshead engine which method comprises lubricating the engine with a cylinder oil and with a system oil, which oils are different from each other, characterised in that the system oil is an SAE 20 or SAE 30 oil, has a total base number of at least 10 mg KOH/g and comprises :-
• the problem of increasing viscosity of the system oil in the engine can be addressed at the same time as addressing other aspects of degradation of the performance of the system oil, such as the problem of increased contamination (for example leaked fuel, combustion debris and by-products, and/or waste cylinder oil) in the system oil.
• This may enable the viscosity of the system oil in the engine to be controlled within a range of viscosities which is lower than might otherwise be the case. This can have benefits of fuel economy for the engine.
• the top-up system oil of the present invention has the same additives as those in the system oil which was previously charged to the engine, but in concentrations which independently, may the same or different to the concentrations in the system oil which was previously charged to the engine.
• the system oil and top-up system oil of the present invention each comprise a base oil.
• the base oil may comprise at least one basestock selected from the group consisting of Group I basestocks; Group II basestocks; Group III basestocks; basestocks derived from Fischer-Tropsch synthesised, waxy, paraffinic hydrocarbon materials; naphthenic basestocks; mineral basestocks having a viscosity index in the range 40 to 80; and mixtures thereof.
• Basestock groups are defined according to API standard 1509, " ENGINE OIL LICENSING AND CERTIFICATION SYSTEM", November 2004 version 15th edition Appendix E , as set out in Table 1 below : Table I Group Saturated hydrocarbon content (wt%) Sulphur content (wt%) Viscosity Index I ⁇ 90 and/or > 0.03 and ⁇ 80 and ⁇ 120 II ⁇ 90 and ⁇ 0.03 and ⁇ 80 and ⁇ 120 III ⁇ 90 and ⁇ 0.03 and ⁇ 120 IV polyalpha olefins V all basestocks not in Groups I, II, III or IV
• Group I and Group II basestock are derived from mineral oil by known refinery process.
• Group III basestocks may be derived from mineral oil by refinery processes known in the art.
• Group III basestocks may also be known as synthetic basestocks and include for example, Shell XHVI (trade mark) and Nexbase (trade mark). Naphthenic basestocks and other mineral oil basestocks may be derived from mineral oil by refinery processes known in the art.
• Basestocks derived from Fischer-Tropsch synthesised, waxy, paraffinic hydrocarbon materials may be made by any suitable known process for the manufacture of basestock from Fischer Tropsch processes. Processes for the manufacture of a basestock derived from Fischer-Tropsch synthesised, waxy, paraffinic hydrocarbon material which may be used, are described for example in US4943672 , EP-A-0668342 and EP-A-0776959 , the contents of which are hereby incorporated by reference.
• the basestock may be made by the steps of (i) producing Syngas, (ii) Fischer-Tropsch synthesis of hydrocarbons from the Syngas, (iii) hydrocracking of the hydrocarbons to produce naphtha and diesel/kerosene fuel process streams together with a waxy paraffinic residue and (iv) hydroisomerising the waxy residue to produce the basestock.
• the system oil and top-up system oil each comprise at least one detergent additive in a total amount of detergent corresponding in performance, as measured by the Hot Filtration Test, to at least 1.5 % by weight of the system oil, of a calcium alkyl salicylate detergent soap in which the alkyl group is a C 12 to C 30 alkyl group.
• the system oil and top-up system oil each comprise at least one detergent additive in a total amount of detergent corresponding in performance, as measured by the Hot Filtration Test, to at least 1.75 % by weight of the system oil, of a calcium alkyl salicylate detergent soap in which the alkyl group is a C 12 to C 30 alkyl group.
• the detergent additive performance is measured by the Hot Filtration Test. This compares the performance of a test sample against a reference sample.
• the Hot Filtration Test is a measure of detergency and fuel-contamination handling performance of the detergent additive. The following procedure may be used, the test being performed in duplicate :
• Each of the one or more detergent additives may comprise a metal salt of an acidic organic compound and a base.
• the metal may be an alkali or alkaline earth metal, for example sodium, potassium, lithium, calcium, barium or magnesium. Mixtures of metal salts may be used. Preferably, the metal is calcium.
• Each of the one or more detergent additives may comprise a metal salt of a carboxylate, a sulphonate, a phenate, a thiophosphate or a naphthenate. Mixtures of salts may be used.
• a preferred carboxylate is salicylate.
• the one or more detergent additives of the present invention comprise calcium phenates, calcium salicylates or mixtures thereof.
• the system oil comprises at least one calcium alkyl salicylate detergent additive, in which the alkyl group is a C 12 to C 30 alkyl group, in a total amount of at least 1.5 % by weight of the system oil, more preferably at least 1.75 % by weight, of calcium alkyl salicylate detergent soap.
• the system oil and top-up system oil each comprise at least one calcium alkyl salicylate detergent additive in which the alkyl group is a C 12 to C 30 alkyl group, in a total amount of at least 1.5 % by weight, more preferably at least 1.75 % by weight of the system oil and top-up system oil, of calcium alkyl salicylate detergent soap.
• Each of the one or more detergent additives of the present invention may comprise a complex/hybrid detergent which may be prepared from a mixture of one or more metal surfactants, for example from a mixture of a calcium alkyl phenate and a calcium alkyl salicylate.
• Each of the one or more detergent additives may contain at least one hydrocarbyl group, for example as a substituent on an aromatic ring.
• hydrocarbyl means that the group is primarily composed of hydrogen and carbon atoms and is bonded to the remainder of the compound via a carbon atom, but does not exclude the presence of other atoms or groups in a proportion insufficient to detract from the substantially hydrocarbon characteristics of the group.
• the alkyl groups have 5 to 100, preferably 7 to 30 carbon atoms.
• Each of the one or more detergent additives may be sulphurised. Processes for sulphurizing are known in the art.
• Each of the one or more detergent additives may be borated. Processes for borating are known in the art.
• Each of the one or more detergent additives may be a neutral detergent, a low based detergent, a low overbased detergent or a high overbased detergent
• Each of the one or more detergent additives may have a total base number in the range of from greater than 0 to 500 mg KOH/g, preferably in the range 25 to 500 mg KOH/g, more preferably in the range of 30 to 300 mg KOH/g.
• Total base numbers may be measured according to ASTM D 2896-98.
• the system oil and top-up system oil each may comprise at least one high base detergent additive in a relatively large amount - for example calcium phenate with a total base number of 400 mg KOH/g in an amount of 5 % by weight.
• the system oil and top-up system oil of the present invention each comprise at least one anti-wear additive.
• Suitable anti-wear additives include dihydrocarbyl dithiophosphate metal salts.
• the metals of the dihydrocarbyl dithiophosphate metal salts may be alkali metals, alkaline earth metals, aluminium, lead, tin, molybdenum, manganese, nickel, zinc or copper.
• the system oil and top-up system oil of the present invention each comprise at least one zinc dihydrocarbyl dithiophosphate anti-wear additive.
• Primary and/or secondary hydrocarbyl groups may be present in the anti-wear additives.
• the hydrocarbyl groups may be alkyl groups.
• Each hydrocarbyl group may have 1 to 18 carbon atoms.
• the total amount of the anti-wear additives in each of the system oil and the top-up system oil of the present invention is preferably in the range, expressed as zinc of up to 1100 ppm zinc.
• the total amount of the anti-wear additives in each of the system oil and the top-up system oil of the present invention is preferably in the range, expressed as phosphorus of up to 1000 ppm phosphorus, preferably in the range 100 to 600 ppm phosphorus and more preferably in the range of 200 to 400 ppm phosphorus.
• the system oil and top-up system oil of the present invention may also comprise one or more dispersants.
• the dispersants are ashless dispersants. These are non-metallic organic compounds that form substantially no ash on combustion.
• Each ashless dispersant may comprise a long chain hydrocarbon with a polar head.
• the polar head may comprise oxygen, phosphorus or nitrogen atoms.
• the hydrocarbon chain may have 40 to 500 carbon atoms.
• Suitable ashless dispersants are succinimides, for example polyisobutene succinic anhydride; polyamine condensation products; succinimides, for example polyisobutene succinimides; succinic esters, for example polyisobutene succinic esters; or aminated succinic ester, for example aminated polyisobutene succinic esters.
• the dispersants may be borated. If present, the total amount of dispersant in each of the system oil and top-up system oil of the present invention may be in the range of from greater than 0 to 3 % by weight, preferably in the range of from greater than 0 to 2 %, more preferably in the range of from greater than 0 to 1 % by weight.
• the system oil and top-up system oil of the present invention may also comprise one or more anti-foam additives.
• Typical anti-foam additives which may be used include polydimethyl siloxanes and methacrylates. If present, the total amount of anti-foam additives in each of the system oil and top-up system oil of the present invention may be an amount expressed as silicon, of up to 50 ppm, preferably up to 30 ppm, more preferably up to 15 ppm.
• the system oil and top-up system oil of the present invention may also comprise one or more anti-rust additives.
• Typical anti-rust additives which may be used include nonyl phenolamine, octyl phenolamine and non-phenol based anti-rust additives, for example alkylene glycols. If present, the total amount of anti-rust additives in each of the system oil and top-up system oil of the present invention may be up to 1 % by weight, preferably up to 0.5 % by weight and more preferably up to 0.2 % by weight.
• the system oil and top-up system oil of the present invention may also comprise one or more pour point depressants.
• Typical pour point depressants which may be used include polymethacrylate compounds. If present, the total amount of pour point depressants in each of the system oil and top-up system oil of the present invention may be up to 1 % by weight, preferably up to 0.5 % by weight, more preferably up to 0.25 % by weight.
• the system oil and top-up system oil of the present invention may also comprise one or more anti-oxidants in addition to the anti-wear additives and/or detergents, which may also act at least in part as anti-oxidants.
• Typical anti-oxidants which may be used include phenolic ashless anti-oxidants and aminic ashless anti-oxidants.
• the total amount of anti-oxidants other than anti-wear additive and/or detergents which act at least in part as anti-oxidants, in each of the system oil and top-up system oil of the present invention may be up to 1 % by weight, preferably up to 0.5 % by weight, more preferably up to 0.2 % by weight.
• the system oil and top-up system oil of the present invention may also comprise one or more friction modifiers.
• Typical friction modifiers include salicylates; stearates, for example calcium stearate; glycerol mono oleate and oleamides; and natural esters, for example sunflower oil.
• the total amount of glycerol mono oleate and/or oleamide friction modifiers in each of the system oil and top-up system oil of the present invention may be up to 1 % by weight, preferably up to 0.5 % by weight, more preferably up to 0.2 % by weight.
• Other friction modifiers may be present at higher concentrations.
• the system oil and top-up system oil for the present invention may each independently have a total base number of 10 to 40 mg KOH/g, preferably of 10 to 30 mg KOH/g, more preferably of 15 to 30 mg KOH/g, yet more preferably of 15 to 20 mg KOH/g.
• the system oil and the top-up system oil may have the same total base number.
• the top-up system oil may have a base number which is lower than the system oil previously charged to the engine.
• the top-up system oil may have a base number which is higher than the system oil previously charged to the engine, for example a top-up system oil with a total base number in the range of 15 - 20 mg KOH/g may be used with a system oil previously charged to the engine having a total base number in the range of 10 - 15 mg KOH/g.
• Total base number may be measured according to ASTM D 2896-98.
• the system oil is an SAE 20 or SAE 30 oil.
• SAE 20 oils have a viscosity at 100 °C in the range of 5.6 to less than 9.3 cSt.
• SAE 30 oils have a viscosity at 100 °C in the range of 9.3 to less than 12.5 cSt.
• the system oil is an SAE 30 oil.
• engine designers and manufacturers often specify minimum viscosities of system oil which may be used in the engine.
• the system oil used in the present invention may have a kinematic viscosity at 100 °C in the range of 7.9 to less than 12.5 cSt, preferably in the range of 8.8 to 11.5 cSt, more preferably in the range of 9.3 to 11.5 cSt.
• the viscosity of the system oil in the engine may be controlled by replenishing the system oil in the engine with a top-up system oil in which the top-up system oil has the same additives and in the same or different concentrations as in the system oil previously charged to the engine but which has a viscosity which is lower than that of the system oil previously charged to the engine.
• the system oil in the engine may be replenished by adding to the engine, top-up system oil to replace engine oil which has been consumed or lost from the engine.
• the system oil in the engine may be replenished by removing part of the system oil from the engine and replacing it with top-up system oil.
• On-line cleaning may be used in conjunction with partial replacement of the system oil in the engine.
• the top-up system oil may be an SAE 20 or an SAE 30 oil, preferably, the top-up system oil is an SAE 20 oil.
• the top-up system oil has a kinematic viscosity measured at 100 °C which is in the range of 5 to 1 cSt less than that of the system oil previously charged to the engine, preferably in the range of 4 to 2 cSt less than that of the system oil originally charged to the engine.
• the viscosity of the system oil in the engine may be regularly and/or continuously monitored.
• the viscosity of the system oil in the engine may be continuously monitored for example, with an in-line monitor.
• Addition of system top-up oil may be controlled by an in-line monitor which continuously monitors the viscosity of the system oil in the engine.
• the cylinder oil may be any cylinder oil known in the art.
• the cylinder oil is an SAE 50 oil.
• Suitable cylinder oils include Castrol Cyltech 50S (trade mark), Castrol Cyltech 80AW (trade mark), Castrol Cyltech 70 (trade mark), Castrol Cyltech 40 SX (trade mark), BP Energol CLO 50M (trade mark), BP Energol CL-DX 405 (trade mark) and BP Energol CL 505 (trade mark).
• the methods of the present invention are used for lubricating a two-stroke, diesel crosshead engine.
• the diesel engine may be marine or land based.
• a system oil for use in the present invention was prepared using a mixture of Group I basestocks.
• This system oil comprised zinc dihydrocarbyl dithiophosphate anti-wear additive and had a concentration of salicylate and phenate detergents which will correspond in performance, as measured by the Hot Filtration Test, to at least 1.5 % by weight of the system oil, of a calcium alkyl salicylate detergent soap in which the alkyl group is a C 12 to C 30 alkyl group.
• the system oil was used to lubricant a MAN B &W model 6L 70MC Mk6 marine diesel crosshead engine having a power of 16980 KW at 108 rpm. It was operated with a load of 12917 KW at 103 rpm and 76 to 78 % of its Maximum Continuous Rating.
• the system oil in the engine may be replenished with a top-up system oil, which has the same additives, in the same or different concentrations as in the system oil previously charged to the engine but which has a viscosity which is lower than that of the system oil previously charged to the engine.
• a suitable top-up system oil might be an SAE 30 with a kinematic viscosity at 100°C of less than 11.5 cSt.
• a suitable top-up system oil might be an SAE 20 oil.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Lubricants (AREA)

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Citations (2)

• 2007
  • 2007-03-30 EP EP07251415A patent/EP1985689A1/de not_active Ceased
• 2008
  • 2008-03-20 CN CN200880011032A patent/CN101652458A/zh active Pending

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