Mitsui-MAN B&W 6S50MC-C Engine
The production of Mitsui-MAN B&W 6S50MC-C engine was completed in April, 1997 at Tamano Works of Mitsui Engineering & Shipbuilding Co., Ltd. The engine type, S50MC-C, is one of the S-MC-C series of engines, which have been lately introduced as successors to previous engine series, S-MC. The produced engine has 6 cylinders, and its principal particulars are;
The engine was successfully tested in Tamano Works, then installed in a small container vessel made in Peene shipyard in Germany, and has been in service with good results.
Compared with the S-MC engines, the S-MC-C engines are designed to produce 10% more power, while the size of the engine body has become more compact (about 10% weight reduction). The power up has been achieved by about 5% increase in the mean effective pressure from 18 bar to 19 bar, and by about 5% increase in the mean piston speed. In order to secure the reliability of the engine, the engine construction has been thoroughly reviewed, and various new designs have been introduced.
Stay Bolt Design
The stay bolt tightens the main construction of the engine, such as the bed plate, the frame box, and the cylinder frame. The conventional stay bolt goes from the bottom of the bed plate to the top of the cylinder frame, while in case of the new design of S-MC-C, it goes from the top of the bed plate to the top of the cylinder frame. Thus, the bed plate does not get the tightening force, thereby the main bearing housing does not become deformed by the tightening force. It would contribute to improvement in the working condition of the main bearing. Further, the conventional stay bolt was going through a hole, therefore, it was not exposed inside the crank case, The new stay bolts are arranged with 2 pieces on each side, and they are exposed inside the crankcase. This contributes to simplifying the construction and to decrease the weight of the engine.
Combustion Chamber
Components
To cope with the increased power, so called "high top land" piston design has been introduced. This means that the piston ring position with respect to the top of the piston crown is lowered, in other words the rings have been moved away from the heat. The first piston ring design is the so called "CPR (controlled pressure relief)" type, which is gas-tight ring with some gas leakage grooves. By using this ring, the circumferential temperature distribution becomes much even compared with the angle cut piston ring.
Tin-Aluminum Bearings
For the major bearings of the engine, such as the main bearing, the crank pin bearing, and the cross head bearing, the tin-aluminum bearing material is used. This material has stronger fatigue strength compared with conventional white metal.
The number of orders for the S50MC-C has increased to 23 by October, 1998, and the other types of the series, such as S46MC-C and S60MC-C were completed in the spring of 1998. Good customer satisfaction on those S-MC-C series of engines is expected.
