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Wartsila ?31DF Series Product Manual
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Contents
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Crankshaft itself is forged in one piece. Both main bearings and big end bearings temperaturesare continuously monitored.Counterweights are fitted on every web. High degree of balancing results in an even and thickoil film for all bearings.The connecting rods are arranged side-by-side and the diameters of the crank pins and journalsare equal irrespective of the cylinder number.All crankshafts can be provided with torsional vibration dampers or tuning masses at the freeend of the engine, if necessary. Main features of crankshaft design: clean steel technologyminimizes the amount of slag forming elements and guarantees superior material durability.The crankshaft alignment is always done on a thoroughly warm engine after the engine isstopped.4.2.3 Connecting rodThe connecting rod is of forged alloy steel. All connecting rod studs are hydraulically tightened.The connecting rod is of a three-piece design, which gives a minimum dismantling height andenables the piston to be dismounted without opening the big end bearing.4.2.4 Main bearings and big end bearingsThe main bearings and the big end bearings are of tri-metal design with steel back, lead-bronzelining and a soft running layer. The bearings are covered with a Sn-flash for corrosion protection.Even minor form deviations can become visible on the bearing surface in the running in phase.This has no negative influence on the bearing function. A wireless system for real-timetemperature monitoring of connecting rod big end bearings, "BEB monitoring system", is asstandard.4.2.5 Cylinder linerThe cylinder liners are centrifugally cast of a special alloyed cast iron. The top collar of thecylinder liner is provided with a water jacket for distributing cooling water through the cylinderliner cooling bores. This will give an efficient control of the liner temperature. An oil lubricationsystem inside the cylinder liner lubricates the gudgeon pin bearing and also cools piston crownthrough the oil channels underside of the piston.4.2.6 PistonThe piston is of composite type with steel crown and nodular cast iron skirt. A piston skirtlubricating system, featuring oil bores in a groove on the piston skirt, lubricates the pistonskirt/cylinder liner. The piston top is oil cooled by the same system mentioned above. Thepiston ring grooves are hardened for extended lifetime.4.2.7 Piston ringsThe piston ring set are located in the piston crown and consists of two directional compressionrings and one spring-loaded conformable oil scraper ring. Running face of compression ringsare chromium-ceramic-plated.4.2.8 Cylinder headThe cross flow cylinder head is made of cast iron. The mechanical load is absorbed by a flameplate, which together with the upper deck and the side walls form a rigid box section. Thereare four hydraulically tightened cylinder head bolts. The exhaust valve seats and the flamedeck are efficiently and direct water-cooled. The valve seat rings are made of alloyed steel,for wear resistance. All valves are hydraulic controlled with valve guides and equipped withvalve springs and rotators.4-2 DBAE248994Wärtsilä 31DF Product Guide4. Description of the Engine |
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