crosshead bearing lubrication

So let’s discuss one by one starting from main shaft bearing. When engine is not running, the shaft actually touches and sit on the bearing only. It must effectively prevent the buildup of deposits in the ring zone and in ports of port exhausted two stroke engines. Interested in listening from you. The high operating temperature, pressure, and the presence of a corrosive environment make the working condition very harsh. Now from the drillings in the connecting rod, it goes to the bottom end bearing. MEO CLASS 1 preparatory course institutes have been given in this post and they are latest. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new … At the very top most part of the liner, lubrication film does not last much longer as it is burned off very easily. First let’s pick the main shaft bearings. Over eighty percent of total lubricant consumption is on cylinder oil alone and it represents a major expense in the daily operation of the engine. Apart from that the speed of oscillation is not very significant which in turn means that it will not generate a pumping action for lubrication … Lubrication between the piston rings and the liner is a very challenging issue considering the extreme temperature and combustion products present in this area. It must burn cleanly, leaving as little and as soft a deposit as possible. The load is continually downward and because the con rod swings about the pin, changing direction each stroke, true hydrodynamic lubrication … In spite of these difficulties, the cylinder lubricants have to perform their duties. But there is a problem with the lubrication here. Here in this article we will discuss lubrication in following bearings: The lubrication in all the above surfaces is different as the relative motions are either rotary, sliding and point contacts. If you can remember, crosshead does not have a rotary motion, and have movement of some degrees (small end of crankpin bearing). What are low speed two-stroke Crosshead-type Marine Diesel Engines? The lubrication in all the above surfaces is different as the relative motions are either rotary, sliding and point contacts. 2. It will ultimately lead to blow down which further aggravates lubrication problems. The load is continually downward and because the con rod swings about the pin, changing direction each stroke, true hydrodynamic lubrication cannot take place. Abanteriba, S. "Analysis of the Lubrication Condition of a Crosshead Pin Bearing of a Large Marine Diesel Engine." And bearing is floating on the layer of oil. Low speed two stroke crosshead diesel engines are generally used as prime movers on ships and are also used for electricity generation on shore based power plants. But reliable analysis indicates that only 10 to 15 % is converted into sulphuric acid, and that amounts to 450 Kg of sulphuric acid per day which may lead to highly corrosive wear. increasing the thermal efficiency, lowering the specific fuel oil combustion, and reducing the size and weight. The remaining oil goes to the thrust bearing, chain drive, hydraulic power supply unit to actuate exhaust valves, main bearings… All Rights Reserved. Drain frame. The piston rod reciprocates up and down through the stuffing box which seals the crankcase from the under-piston space. And hence the type of lubrication is hydrodynamic and builds when the shaft actually starts rotating. In gear wheel boundary lubrication works as the oil is sprayed all over the contact surface. Thus hydrodynamic lubrication is not possible here. Thus at the time of starting or change of speed of the engine, the wear on the bearing will be too much. This resulted in higher engine pressure, thinner oil film formation, high liner temperature, and increased corrosion. The inclusion of additives such as polymethacrylates and ethylene-propylene co-polymers (OCP) to improve the oiliness helps in maintaining the requisite oil film thickness due to its molecular bending with porous cylinder liner. The engine lubrication system, with exception of cylinder lubrication, is supplied by one of two main pumps, which take suction from the sump tank and supply oil to the low pressure main bearing system. The piston has a long piston rod which sits on the crosshead. Engine developments from the 1960s to the 2000s have led to higher average temperatures of liners in the upper zone (about 270 degrees C), which has also made lubrication difficult. Used on container vessels, oil and gas tankers and bulk carriers, large, two-stroke crosshead diesel engines with bore diameters from 300–960 mm (11–38 in) require significant amounts of lubricating … Main engine shaft  Bearings or Journal Bearings or crank pin bearing. The term low speed is applied to engines having a rotational speed of up to 300 rpm and output per cylinder between 400 Kilowatts to 6000 Kilowatts generally. The upper connecting rod bearing, guide shoes and the lower connecting rod bearing are lubricated from the crosshead-oil system. In the next article “Cylinder Liner Lubrication of Marine Two Stroke Crosshead Diesel Engines Part 2,” we discuss lubricants and the selection of the lubricants for different types of fuel oils. Internal drilled passages supply the oil for the bearing. Combustion forces are passed on from piston to the crosshead. One of two crosshead lubrication pumps takes suction from the main bearing system, after the automatic back flush filter, … The finish should be mirror like with no evidence of scoring or roughness. The temperature of water cooled liner surface varies from 230 degrees C to 120 degrees C depending upon the design. Also the surface finish for such bearing is kept better during manufacturing and the shell material is more smooth as compared to other shell. Because, hydrodynamic lubrication is disturbed. Around a viscosity of 120-150cst at the temperature of 50 degree celsius is used. The angular distance of the lubricating groove 22 can be a maximum of 120 °. In a vertically oriented engine the pressure on the bearing is always downwards, resulting in a depleted lubrication film on the lower contact surfaces of the bearing shell. All modern marine engines are of two stroke type. Two strokes and crosshead operation of marine engines. Crosshead Lubrication. In these types of engines the piston is not connected to the crankshaft directly with the connecting rod but an additional member called the crosshead is provided. Remove as much oil as possible with a vacuum hose. Why Fuel Changeover is Needed As per the direction by the […], Being a Marine Engineer is very much a rewarding career if you are willing to put up with the difficulties! A Good respect in heart- for web. When engine is not running, the shaft actually touches and sit on the bearing only. This is taken care of by lubricating oil of high TBN values (60-80 TBN). The crosshead bearing is difficult to lubricate effectively. Because the top of the connecting rod swings about the pin and changes direction each time the piston reaches mid stroke, the relative speed between bearing and pin at mid stroke is zero, accelerates to a maximum as the piston approaches top or bottom dead … With Strict Regulations for emission control coming in control, fuel changeover to cleaner fuel is mandatory. First let’s pick the main shaft bearings. ... in the crankshaft to the bottom end bearing and then up a drilled passage in the connecting rod to the gudgeon pin or crosshead bearing. From the mechanical point of view, the working conditions are about the worst possible for the establishment of hydrodynamic lubrication. And hence the type of lubrication is hydrodynamic and builds when the shaft actually starts rotating. So cylinder liner lubricant needs to be competent enough to fight against these aggravated conditions. Prime until old oil is purged from oil passages and flushing oil steadily flows from all bearings and crosshead bushings. This is especially true of high additive content oils as unsuitable types can form objectionable ash deposits. Most of the cylinder oil which is used for lubrication is burned off. There is therefore no cooling effect of crankcase oil on the piston, cylinder lubrication being entirely dependent upon the oil supply by mechanical lubricators. This makes cylinder lubrication critical, and any deficiency in it may lead to failure of the engine. Required fields are marked *. Two stroke crosshead operation of marine engine. But there is a problem with the lubrication here. If this were all converted into SO3 and then into sulphuric acid, this would produce 10 tons of highly corrosive acid. Most of the cylinder oil which is used for lubrication is burned off. And bearing is floating on the layer of oil. Further it is ensured that the cylinder liner temperature doesn’t go below the dew point temperature of sulphuric acid in the upper zone and thus the corrosion is reduced to a minimum value. This was all from the article on the Main engine bearing lubrication. Note: As we can see the oil wedge which floats the shaft away from the bearing, forms when only there is a considerable speed and relative motion between the two. Slow speed two-stroke diesel engines have various arrangements to deliver lubricating oil directly to the crosshead bearings and guides to ensure adequate lubrication. Incompletely burnt heavy ends of the fuel can cause excessive deposits in the piston ring zone. Thus hydrodynamic lubrication is not possible here. Ash, either soluble or insoluble, in fuel can increase the abrasive wear of piston rings and liners. The function of the crosshead is that it absorbs the transverse thrust of the engine. #marinersgalaxy, A post shared by marinersgalaxy.com (@mariners_galaxy) on May 2, 2020 at 9:10am PDT. Engine development to reduce cost of running. It must reduce sliding friction between the rings and the liner to a minimum, thereby minimizing metal to metal contact and frictional wear. Also the surface finish for such bearing is kept better during manufacturing and the shell material is more smooth as compared to other shell. Main engine bearings lubrication is being discussed in this article and information about the lubrication of all the major bearings and type of lubrication happening between the surfaces. The bearing clearance and the functioning of the bearing lubrication are to be checked periodically. In this video you will see a nice animation about crosshead bearing which is only installed on 2 stroke engines. Engine development is basically aimed towards reducing cost of running, i.e. This is due to the design of the lower shell of the crosshead bearing which has machined wedges to hold oil in them and to support the hydrodynamic lubrication of crosshead pin. Lubrication in crosshead is very tough, reason being the restricted movement of the crosshead .However it is to be noted that in crosshead type engine the lower half of crosshead bearing is always loaded. Shaft has a rotary motion as compared to the bearing material. Well I am not a writer, just writes what can help people-that's it. The crosshead bearing is more or less similar to the one which we use for the main bearing. If you can remember, crosshead does not have a rotary motion, and have movement of some degrees (small end of crankpin bearing). Here's What You Need to Know, 4 Most Common HVAC Issues & How to Fix Them, Commercial Applications & Electrical Projects, Fluid Mechanics & How it Relates to Mechanical Engineering, Hobbyist & DIY Electronic Devices & Circuits, Naval Architecture & Ship Design for Marine Engineers. Copyright © 2020 Bright Hub PM. So let’s discuss one by one starting from main shaft bearing. An original pin boss friction measuring device was developed and used to successfully obtain measurements. A few engine manufacturers have recently developed a timely oil injection system similar to the fuel injection. But occasionally it touches bearing when running at very low speed. Also, the lubricant which is used for the lubrication should have a good viscosity that it can last in such high temperature. In gear wheel boundary lubrication works as the oil is sprayed all over the contact surface. At the very top most part of the liner, lubrication film does not last much longer as it is burned off very easily. Additives to improve dispersancy and detergency have been developed to minimize abrasive wear and ring zone deposits. Chances of bearing getting damaged are quite high as there is no proper lubrication and load acting on to it is too much. This provides the crosshead bearing with an effective bearing area in the heavily loaded part of the bearing, which is designed to make this type of bearing smaller so that a crosshead bearing with a lubrication pocket can be created. Proceedings of the ASME 2005 Fluids Engineering Division Summer Meeting . The aim of this research was to analyze the lubrication conditions of piston pin boss bearings used in the press-fit piston pins of automobile gasoline engines. What makes Cylinder Lubrication Difficult, What makes Cylinder Lubrication Difficult (Continued), The odds against cylinder lubricating oil, This post is part of the series: Cylinder Liner Lubrication of Marine Two Stroke Crosshead Diesel Engines, Cylinder Liner Lubrication of Marine Two Stroke Crosshead Diesel Engines, Cylinder Liner Lubrication of Marine Two Stroke Crosshead Diesel Engines Part 2, Commercial Energy Usage: Learn about Emission Levels of Commercial Buildings, Time to Upgrade Your HVAC? The liner average surface temperature has increased from 200 degrees C to 275 degrees C from the 1970s to the 2000s, thus making lubrication more difficult. 3. But gradually when it picks up speed, the oil around starts to accumulate in between bearing and the shaft. This series discusses the challenge of cylinder liner lubrication in Marine two stroke crosshead low speed diesel engines. And the kind of lubrication changes across the liner. Cylinder lubrication of two-stroke crosshead marine diesel engines AUTHOR: Ole Christensen, General Manager, Cylinder Lubrication, R&D Two-stroke Programs & Technologies, Wärtsilä Industrial Operations The two-stroke crosshead diesel ... to the engine system oil used for bearing lubrication and cooling purposes. If any is found then the pin must be replaced or polished. Because the crosshead bearing is not hydrodynamic ally lubricated, and relies on boundary lubrication at the beginning and end of the swing then any damage to the pin will damage the … As we know that guide have a sliding surface and friction is too much. The oil film made, makes sure that when two teeth touch, there is a film of oil to prevent the metal to metal contact in a dry state.

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