Marine Engine Lubrication

Abstract

A two-stroke, cross-head, slow-speed, compression-ignited marine engine is operated by (i) fuelling it with a diesel fuel, as a pilot fuel, and with a low sulphur fuel, as a main fuel; and (ii) lubricating the engine cylinder(s) with a lubricant having a BN of 20 or less and having a detergent additive system comprising one or more different metal detergents having a surfactant group selected from phenate, salicylate and sulphonate, or one or more complex metal detergents containing two or more different surfactant soap groups selected from phenate, salicylate and sulphonate, and a distilled cashew nut shell liquid or hydrogenated distilled cashew nut shell liquid.

What is claimed is: 
     
         1 . A method of operating a two-stroke, cross-head slow-speed compression-ignited engine comprising
 (i) fuelling the engine with a diesel fuel, as a pilot fuel, and with a low sulphur fuel, as a main fuel; and   (ii) lubricating the cylinder(s) of the engine with a cylinder lubricant having a base number (BN) of 20 mg KOH/g or less, comprising a detergent additive system comprising one or more metal detergents having a surfactant selected from phenate, salicylate and sulphonate, or one or more complex metal detergents containing two or more different surfactant soap groups selected from phenate, salicylate and sulphonate, and comprising 1-5 mass %, based on the lubricant mass of one or more phenolic compounds comprising distilled cashew nut shell liquid or hydrogenated distilled cashew nut shell liquid.   
     
     
         2 . A method as claimed in  claim 1 , wherein the cylinder lubricant also comprises a zinc- and boron-containing antiwear system. 
     
     
         3 . A method as claimed in  claim 1 , wherein the phenolic compound(s) comprises hydrogenated distilled cashew nut shell liquid. 
     
     
         4 . A method as claimed in  claim 3 , wherein the hydrogenated distilled cashew nut shell liquid is hydrogenated cardanol. 
     
     
         5 . A method as claimed in  claim 1 , where the phenolic compound(s) comprise 3-pentadecylphenol and 3-pentadecylresorcinol. 
     
     
         6 . A method as claimed in  claim 1 , wherein the metal is calcium. 
     
     
         7 . A method as claimed in  claim 1 , wherein the low sulphur fuel is liquefied natural gas (‘LNG’) or compressed natural gas. 
     
     
         8 . A method as claimed in  claim 1 , where the detergent system comprises one or more overbased calcium phenates. 
     
     
         9 . A method as claimed in  claim 1 , where the cylinder lubricant has a base number (BN) of 15 mg KOH/g or less. 
     
     
         11 . A method as claimed in  claim 1 , wherein the fuel includes more than 50% of main fuel and less than 50% of pilot fuel. 
     
     
         12 . A method as claimed in  claim 11 , wherein the fuel includes more than 60% of main fuel. 
     
     
         13 . A method as claimed in  claim 12 , wherein the fuel includes more than 90% of main fuel. 
     
     
         14 . A method as claimed in  claim 11 , wherein the main fuel is a low sulphur gaseous fuel.