Troubles by the damage of the shafting of main propulsion system give a great impact on the safety of vessels as well as the budget of ship's owners with its tendency of ceaselessness. Cause of trouble varies widely and identification of it requires huge efforts and long time in many cases. The trouble case introduced hereunder also forced the vessel about two-month downtime for repair work and about six-month investigation by the ship builder and the engine manufacturer etc. Estimated cause of trouble obtained is as follows: •Original design of shaft alignment was rather less flexble. •Deformation of hull structure from the warming of engine (cool condition→warm condition) and change of ship's condition (light condition→laden condition) . Original design of shaft alignment was based on the cool and light condition. •The journal of No.8 main bearing got afloat reclining down aftward and too high oil pressure generated at the aft edge of the lower bearing metal, which load to the metal fracture and heat crack of crankshaft. Unknown factors are still left, yet for the prevention of recurrence of similar trouble as many lessons as possible must be learned from this accident and close cooperation of parties concerned including ship owners, ship builders and engine manufactures is strongly required.
The ship have completed the docking survey at Singapore. After twenty hours in sailing for loading port, the main deisel engine occurred explosion in the scavenging air manifold. And then the main engine stopped by auto.device. But it was not re-start. Both of the aux. blowers damaged at impeller and casing. The ship was staying for a week at emergency anchorage. The aux, blowers changed completely with elect. Motors. It caused that much accumulated oily mist in the scavenging air manifold by the drain pipe be blockade was ignited.
With the successive introduction of larger and faster ships, two components are needed: high-output propulsion engines and highly efficient engines. This requirement has been fulfilled with extensive research and studies of the engine manufacturers along with all kinds of feedback from the users. However, it appears that the engine safety margin has been sacrificed somewhat in the process of engine development to meet the above requirement. For example, abnormalities in combustion chamber-related components on high-output engines with large bore sizes are major concerns to be resolved. In addition electric power consumption on recent ships has increased with the delivery of lager ships. A large number of electrically operated control systems have been adopted on ships, and proper handling and maintenance of the electric feeding device have become increasingly important. In view of these concerns, marine engineers are making the utmost efforts to keep the ship's schedules, maintaining the safe operation of the engin plant. I would like to take this opportunity to explain how to cope with the unexpected abnormalities and introduce two cases of trouble shooting which I experienced on board. One problem is the abnormal wear of piston rings and cylinder liners, and the other is the malfunction of the generator and the electric feeling control system. Hopefully this report will serve as a useful reference for marine equipment manufacturers, marine engineers and the concerned parties. In addition we hope that the manufacturers will take our requests as direct feedback from the“engine room”and understand the circumstances pertaining to marine equipment operation.
This essay is introdusing troubles on medium and small size diesel engines that author had met during his long life on training ship, and also explaining their phenomenon and cause. On account of the development of high reliability and antipollution diesel engine further more, this article advise engineers in charge of design or manufacture at diesel engine factories on their professional attitude that put on the heavy work of diesel engine in hard sea condition.
This paper was voted best diesel paper at the 22nd CIMAC Congress, May 1998. Engine manufactures promote medium speed trunk piston engine designs equipped with flame rings on the basis of less bore polish and controlled, low oil consumption as a direct consequence of the virtual elimination of piston crown land deposits. A model of the influence of oil consumption and oil charge on oil stress factors has been used to illustrate the increase in oil stress when such modern designs are introduced.The oil degradation as predicted by the model is compared with actual practices using as an example parameter the BN depletion rate. Results from the full scale Wärtsilä 4L20 laboratory engine shed light on the actual BN degradation process and the effect different oil chemistries have. Also the operating environment for acceptable equilibrium oil conditions-at which no oil change would be required-is analysed in detail and it is calculated that a minimum oil consumption of 0.5 g/kWh is required, in line with current recommendations by major engine manufacturers. In addition, the test results reveal to what extent critical engine condition parameters like piston under crown cleanliness and fuel pump plunger sticking are affected not only by different levels of oil stress, but also by variations of oil chemistry. Finally, the data generated in the controlled laboratory environment are shown to be consistent with information from service experience and may thus be used with confidence to guide selection of commercial lubricants.