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Fig.2: List of references, total MC programme

 

The S-MC-C engines were introduced in 1996, with the S50MC-C as the first. They soon gained a firm foothold in the market and, today, some 300 are on order or in service world-wide, Fig.3. More details of the S-MC-C engines are given in Ref. [1].

The engines have now been in service for more than two years, and the general service experience has been very satisfactory.

The large bore engine types, the K98MC/MC-C and the S90MC-C were also introduced some five years ago, with the K98 targeting the containership market, and the S90MC-C the VLCC market. However, until a few years ago, our popular K90MC/MC-C and the S80MC were able to meet the market demand in these sectors.

Containerisation has kept increasing over the years, and l998 was the year in which the first vessels with a capacity of more than 6,000 teu entered service - and even larger vessels are likely to come. In this context, increasing power is called for, in excess of 90,000 bhp, and the K98MC engine meets this demand. So far, more than 60 such engines have been ordered, including a large number of 12-cylinder units, developing more than 93,000 bhp each.

For even larger and/or faster container ships, engine power in excess of 100,000 bhp will be needed - some 125,000 bhp is often mentioned these days as a likely power demand for 8,000-l2,000 teu vessels.

In order to be able to meet this power demand, we have been investigating the feasibility of the 14, 16 and even 18-cylinder in-line engines and found that such options are realistic, providing nearly 140,000 bhp from a single unit. These in-line engines will, however, become rather long and heavy, and might therefore rather lead to the cylinder configuration with the cylinders arranged in a narrow V-form, as this enables the arrangement of 16 cylinders within the space of an in-line 12-cylinder version, see Ref. [2],

For VLCCs, our 7S80MC has been, and still is, widely used. However, increased speeds have already resulted in several orders for our S90MC-C and, as larger ships are required, ULCCS have returned. Eight or nine-cylinder S90MC-Cs are already available to propel them.

These larger engine types reflect the design evolution already successfully implemented on our S46, S50, S60 and S70MC-C types, i.e. a higher power concentration in a compact engine body.

 

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Fig.3 : List of references, two-stroke S-MC-Compact engines

 

3. DESIGN FEATURES

 

The general design is described in Ref. [1] with relation to our small bore and medium bore engines, but the majority of the features are valid for our K98 and S90 as well.

Fig.4 shows the cross-section of the K98MC/MC-C with a brief description of the design features. The following will describe the structural design changes, compared with the previous design, and the development that has taken place in the design of the combustion chamber components as well as factors influencing the cylinder condition.

 

3.1 Engine Structure

Thc structure of the K98MC/MC-C engines incorporates the latest features as introduced on the smaller S-MC-C engine types.

Fig.5 shows a comparison between the original design with throughgoing staybolts and the new design with two smaller staybolts attached to the top of the bedplate.

This design features:

・well defined and rigid main bearing housings for thin-shell main bearings

・transfer of forces to holding-down bolts and cylinder cover through simple structure and high-quality double-butt welds

・simple steel castings without holes for staybolts, giving better casting quality

・staybolts attached to the top of the bedplate, thus significantly reducing deformation of the bearing housing and eliminating fretting in the bearing saddle

・easier maintenance of the holding-down bolts

・reduced deformation of the crosshead guides and thus improved sliding condition for the guide shoes.

 

This design was introduced more than six years ago in the design of our 4T50MX research engine, and was implemented on our S-MC-C engines with good results.

 

 

 

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