Note: The feed rate for the cylinder lubrication oil should be so that not much and not less oil is present for the lubrication. The two stroke crosshead type of marine diesel engines burning residual fuel provide the largest percentage of propulsive power for ships globally. Your email address will not be published. Abanteriba, S. "Analysis of the Lubrication Condition of a Crosshead Pin Bearing of a Large Marine Diesel Engine." 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. Remove standing oil in the frame and guide compartment low points. ... 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. So there is no non-working stroke during which the oil film on the wall can be reformed at moderate temperature and pressure. 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. Read this interesting article: Faults during engine is running Note: The feed rate for the cylinder lubrication oil should be so that not much and not less oil is present for the lubrication. There is therefore no cooling effect of crankcase oil on the piston, cylinder lubrication being entirely dependent upon the oil supply by mechanical lubricators. Shaft has a rotary motion as compared to the bearing material. Hope you enjoyed reading it. 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. Now from the drillings in the connecting rod, it goes to the bottom end bearing. Shaft has a rotary motion as compared to the bearing material. Most of the cylinder oil which is used for lubrication is burned off. Around a viscosity of 120-150cst at the temperature of 50 degree celsius is used. It must burn cleanly, leaving as little and as soft a deposit as possible. All modern marine engines are of two stroke type. 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. Ash, either soluble or insoluble, in fuel can increase the abrasive wear of piston rings and liners. But gradually when it picks up speed, the oil around starts to accumulate in between bearing and the shaft. As engine picks up speed, the oil is drawn into the inside of the shaft, and thus it forms a wedge. Due to engine development to give higher outputs per cylinder and the commercial pressure to burn residual fuels, have all contributed to harsher conditions on the liner, How to Build LED Strobe Lights - Fun Project Explained. Furthermore, we discuss the trouble-shooting related to cylinder lubrication in two stroke crosshead marine engines. Power Assessment. The crosshead on a slow speed 2 stroke is a difficult bearing to lubricate effectively. The characteristics of those bearings are compared and the concept of design approaches is standardized. Remove diaphragm pump and plug connection upstream of frame mounted oil … 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. As we know that guide have a sliding surface and friction is too much. It was revealed that the frictio Mineral acids formed as a result of condensation of sulphur oxides produced during combustion create a serious hazard if they find their way into the crankcase. The isolation of the crankcase allows lower cost residual fuels to be burnt without the fear of any fuel contamination of the lubricating oil of the crankcase. It must possess adequate viscosity at high working temperatures and still be sufficiently fluid to spread over the entire working surfaces to form a good adsorbed oil film. If you can remember, crosshead does not have a rotary motion, and have movement of some degrees (small end of crankpin bearing). And bearing is floating on the layer of oil. But there is a problem with the lubrication here. Similarly the maximum pressure and mean effective pressure also have increased drastically. Because, hydrodynamic lubrication is disturbed. Slow speed two-stroke diesel engines have various arrangements to deliver lubricating oil directly to the crosshead bearings and guides to ensure adequate lubrication. Under such extreme conditions it is impossible for hydrodynamic conditions to exist except perhaps about mid-stroke. The piston has a long piston rod which sits on the crosshead. Engine development to reduce cost of running. At sea you are not woman or man, you are sailor. MEO Class 1 Preparatory Course Institutes, How To Join Merchant Navy After 10th, 12th Class And Graduation, Mandatory Sign Off After 15th June- Trade Unions, Sign Off Procedure Gibraltar (UK) to India: By A Sailor, When he Left first Time to Sea after Marriage’- My Story. The running surfaces of crosshead bearings oscillate relative to each other during operation rather than rotate and therefore full film hydrodynamic lubrication is not possible. This was all from the article on the Main engine bearing lubrication. Because, hydrodynamic lubrication is disturbed. The lube oil pump would be started to ensure a flow of oil from the bearing, and the engine turned on the turning gear to ensure that no restriction to movement is present. Crosshead lubrication,from where the oil is coming(Bhoumick) Type of lubrication in crosshead bearing Prime until old oil is purged from oil passages and flushing oil steadily flows from all bearings and crosshead bushings. 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. Main engine shaft  Bearings or Journal Bearings or crank pin bearing. Solution to this problem is to feed high pressure lubrication oil in to the bearing like in Sulzer or have drilled passage from the main lubrication system as in MAN Engines. Remove as much oil as possible with a vacuum hose. The type of motion of the crosshead of a marine diesel engine is oscillatory in nature wherein it oscillates to a few degrees on either side of the center of oscillation. The load is continually downward and because the con rod swings about the pin, changing direction each stroke, true hydrodynamic lubrication … MEO Class 1 Preparatory Course College Name Address Status Fosma Maritime Institute & Research Organisation (Kol) 305, […], Fuel changeover procedure from HFO to DO has been discussed in this article in detail. Use of SKF lubrication products can extend the life of the cylinder liner and piston and increase the time between required service. The piston rings on the liner surface mostly operate under boundary or thin film lubrication conditions. Learn how your comment data is processed. Internal drilled passages supply the oil for the bearing. And hence the type of lubrication is hydrodynamic and builds when the shaft actually starts rotating. 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. Nature of bearing Assembly at upper part :- In a crosshead type ,the upper part of the connecting rod is a connected to the Crosshead assembly Which consist of crosshead Block,pins and Slippers.This Cross head … Low spreadability of cylinder lubricating oil. In gear wheel boundary lubrication works as the oil is sprayed all over the contact surface. Fuel changeover procedure from HFO to DO-Vice Versa. First let’s pick the main shaft bearings. 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? Two strokes and crosshead operation of marine engines. The temperature of water cooled liner surface varies from 230 degrees C to 120 degrees C depending upon the design. Loves to talk about gadget, music, nerdy stuff and witty substance in the talks. The crosshead converts the linear motion of the piston into the rotational motion of the crankshaft with the help of the connecting rod. Go through the list given below, if you are planning to do this course. It must reduce sliding friction between the rings and the liner to a minimum, thereby minimizing metal to metal contact and frictional wear. The crosshead bearing slides within a track and connects to the conrod and then to the crankshaft. The crosshead on a slow speed 2 stroke is a difficult bearing to lubricate effectively. We discuss the emulsion type cylinder lubricants, the dispersion type cylinder lubricants, and the single phase cylinder lubricants. Also over the years, engine developments aimed at giving higher output per cylinder and adapting the engine to burn ever deteriorating fuel grades have worsened the problem of cylinder liner lubrication. Thus at the time of starting or change of speed of the engine, the wear on the bearing will be too much. On the crosshead connecting rod bearing, the small-end bearing is a split sliding bearing, which is often made separately from the shaft. Lubrication between the piston rings and the liner is a very challenging issue considering the extreme temperature and combustion products present in this area. A crosshead is a mechanism used as part of the slider-crank linkages of long reciprocating engines and reciprocating compressors to eliminate sideways pressure on the piston. Also the surface finish for such bearing is kept better during manufacturing and the shell material is more smooth as compared to other shell. Lubrication in this is same as that happens in the main bearing of the engine. #marinersgalaxy, A post shared by marinersgalaxy.com (@mariners_galaxy) on May 2, 2020 at 9:10am PDT. Lubrication between the piston rings and the liner is a very challenging issue considering the extreme temperature and combustion products present in this area. Interested in listening from you. 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. 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. There is no non working stroke during which the oil film on the wall can be reformed but this problem has also been solved by improvement in timely oil injection system. What are low speed two-stroke Crosshead-type Marine Diesel Engines? Once the bearing has been assembled, all crosshead clearances would be taken, checked with maker’s tolerances, and recorded. MEO CLASS 1 preparatory course institutes have been given in this post and they are latest. Because of the very small bore-to-stroke ratio on … Thus for this reason they are heavily loaded and are very expensive. And since there is no hydrodynamic lubrication here. The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Apart from aggravating lubrication problems, these fuels can damage injectors and corrode turbocharger nozzles and moving blades. Also, the lubricant which is used for the lubrication should have a good viscosity that it can last in such high temperature. The piston slows to rest before reversing direction on the return stroke. 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. When engine is not running, the shaft actually touches and sit on the bearing only. At the very top most part of the liner, lubrication film does not last much longer as it is burned off very easily. Two stroke crosshead operation of marine engine. When engine is not running, the shaft actually touches and sit on the bearing only. If any is found then the pin must be replaced or polished. 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. The crosshead bearing is more or less similar to the one which we use for the main bearing. Multilevel lubrication systems have increased oil film thickness considerably. A known method of overcoming this difficulty is to provide, in association with each small end bearing between a connecting rod and a crosshead of a reciprocating internal combustion engine a reciprocating oil pump which delivers to the substantially continuously loaded area of the bearing a "shot" of lubricant at … But there is a problem with the lubrication here. Save my name, email, and website in this browser for the next time I comment. Thus hydrodynamic lubrication is not possible here. If you can remember, crosshead does not have a rotary motion, and have movement of some degrees (small end of crankpin bearing). The piston rod reciprocates up and down through the stuffing box which seals the crankcase from the under-piston space. Crosshead pin is made more bigger in diameter so that it can take higher load. From the main LO p/p, LO is supplied to manifold and is supplied to crosshead via a telescopic … And the kind of lubrication changes across the liner. A Good respect in heart- for web. So let’s discuss one by one starting from main shaft bearing. But occasionally it touches bearing when running at very low speed. 1 Main bearing Lubrication, cooling System oil System oil Load, heat 2 Crank pin bearing Lubrication, cooling System oil System oil Load, heat 3 Crosshead and conrod Bearings Lubrication, cooling System oil System oil Load, heat 4 Cylinder liner, piston ring and piston ring groove Lubrication, wear control, sealing, … It must effectively neutralize the corrosive effects of mineral acids formed during combustion of the fuel. Also the surface finish for such bearing is kept better during manufacturing and the shell material is more smooth as compared to other shell. The remaining oil goes to the thrust bearing, chain drive, hydraulic power supply unit to actuate exhaust valves, main bearings… The duration of the course is 2 months. Also less oil will mean localized contact of piston rings with the liner surface without any film of oil and hence it will damage the liner. 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. Also, the lubricant which is used for the lubrication should have a good viscosity that it can last in such high temperature. The crosshead bearing is difficult to lubricate effectively. Here in this article we discuss about the fuel changeover on commercial ships. Engine development is basically aimed towards reducing cost of running, i.e. 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. 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 … But occasionally it touches bearing when running at very low speed. First let’s pick the main shaft bearings. Around a viscosity of 120-150cst at the temperature of 50 degree celsius is used. And the kind of lubrication changes across the liner. 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. The high operating temperature, pressure, and the presence of a corrosive environment make the working condition very harsh. Solution to this problem is to feed high pressure lubrication oil in to the bearing like in Sulzer or have drilled passage from the main lubrication system as in MAN Engines. It must effectively prevent the buildup of deposits in the ring zone and in ports of port exhausted two stroke engines. Instead the lubrication starts as boundary, and … Combustion forces are passed on from piston to the crosshead. There is provided a crosshead bearing for a marine engine, comprising a bearing alloy layer, and a coating layer comprising a synthetic resin which is bonded onto the bearing alloy layer, and said coating may contain at least one kind selected from the group consisting of a solid lubricant, hard particles, and a metal powder. Hi there! With Strict Regulations for emission control coming in control, fuel changeover to cleaner fuel is mandatory. Volume 1: Symposia, Parts A and B . Chances of bearing getting damaged are quite high as there is no proper lubrication and load acting on to it is too much. The upper connecting rod bearing, guide shoes and the lower connecting rod bearing are lubricated from the crosshead-oil system. Oil is usually fed through various holes around the liner called as quills and usually injected at the time when piston is going upwards. In MAN B&W ENGINE. Cylinder lubricating oil is highly viscous, which hampers its spreadibility thereby resulting in uneven wear on the cylinder liner. Again, all modern engines are fitted with diaphragm plates and piston rod glands, which effectively separate the cylinder from the crankcase. For better lubrication of crosshead pin bearings, which have a high rate of damage, two types of bearing structures are mainly used as oil supply methods for sliding surfaces at present. At the very top most part of the liner, lubrication film does not last much longer as it is burned off very easily. In MAN engine, the crosshead lube oil pressure is same as that of main lube oil system. 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! As engine picks up speed, the oil is drawn into the inside of the shaft, and thus it forms a wedge. Most of the cylinder oil which is used for lubrication is burned off. Required fields are marked *. 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 … Proceedings of the ASME 2005 Fluids Engineering Division Summer Meeting . And since there is no hydrodynamic lubrication here. This site uses Akismet to reduce spam. Drain frame. This is taken care of by lubricating oil of high TBN values (60-80 TBN). It must be remembered that the cylinder lubricants are used only as a once-through oil. 2.Crosshead engine has a Diaphragm which separate the cylinder spaces from Crankcase. Also, the crosshead enables the connecting rod to freely move outside the cylinder. An optimized lubrication condition of the crosshead bearing in low-speed marine diesel engines is pivotal to its prolonged service life, because the bearing oscillates at a low speed and the direction of the high load is always downward. The finish should be mirror like with no evidence of scoring or roughness. And hence the type of lubrication is hydrodynamic and builds when the shaft actually starts rotating. Crosshead pin is made more bigger in diameter so that it can take higher load. Incompletely burnt heavy ends of the fuel can cause excessive deposits in the piston ring zone. 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. Thus hydrodynamic lubrication is not possible here. It must form an effective seal in conjunction with the piston rings, preventing gas blow by and burning away of the oil film and lack of compression. It also helps in cooling the contacts once the gear teeth messes together. In spite of these difficulties, the cylinder lubricants have to perform their duties. The function of the crosshead is that it absorbs the transverse thrust of the engine. The bearing clearance and the functioning of the bearing lubrication are to be checked periodically. Thus at top dead center where the temperature is at maximum and also the radial pressure of the rings on the walls is highest, the piston slows down. Short exhaust valve life due to deposit formation or corrosive attack by vanadium, sodium, sulphur, and other chemical compounds present either in the fuel or in the lube oil. One way to reduce this friction is to apply oil film called as boundary layer. A typical large engine developing 20000 Bhp with a daily fuel consumption of 76103 Kg burning a 3000 second Redwood No 1 fuel at 100 F and a sulphur content of 4%, the total weight of sulphur burnt would be 3048 Kg or 3 tons. HVAC: Heating, Ventilation & Air-Conditioning. The two stroke crosshead type of marine diesel engines burning residual fuel provide the largest percentage of propulsive power for ships globally. The load is continually downward and because the con rod swings about the pin, changing direction each stroke, true hydrodynamic lubrication … 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. It will ultimately lead to blow down which further aggravates lubrication problems. But there is a problem with the lubrication here. Cross Head Bearing Lubrication. From the crosshead, the oil is further diverted to the under piston space, guides and crosshead bearings. 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. A few engine manufacturers have recently developed a timely oil injection system similar to the fuel injection. If this were all converted into SO3 and then into sulphuric acid, this would produce 10 tons of highly corrosive acid. Thus at the time of starting or change of speed of the engine, the wear on the bearing will be too much. Oil is sprayed over the sliding surfaces, and because of the boundary layer, lubrication takes place. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new … 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. If you can remember, crosshead does not have a rotary motion, and have movement of some degrees (small end of crankpin bearing). 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. Gas temperature exceeding 1667 degrees Celsius are encountered at the beginning of the firing stroke and the local temperature may be appreciably higher if the combustion is poor resulting in flame impingement on cylinder walls. An original pin boss friction measuring device was developed and used to successfully obtain measurements. Copyright © 2020 Bright Hub PM. The crosshead bearing is more or less similar to the one which we use for the main bearing. Well I am not a writer, just writes what can help people-that's it. 2. That means that they have to accomplish their work in one go, and then they are discharged. It also helps in cooling the contacts once the gear teeth messes together. This is especially true of high additive content oils as unsuitable types can form objectionable ash deposits.