Propulsion Machinery Review

by Graeme MacLennan, international editor

Propulsion machinery makers are keeping ahead of the market, and are well able to meet the requirement for increasing unit powers and operational flexibility with high economy. A difference of 2 g/kW-h in fuel consumption may not sound like very much, but when associated with an engine developing a continuous 40 MW over a trans-Pacific voyage, it will amount to nearly two tons per day. The design of large engines has reached a plateau, with only modest year-by-year improvements to performance. Activity is devoted to extending the time between necessary overhaul and inspection, ease of maintenance and the life of working parts. Builders of engines of all sizes, and gas turbine makers, have had to devote much time and attention to the quality of exhaust gases. A number of port authorities already have legislation in force for limiting No , So and particulate emissions, and those composed in Ihe State of California are very strict. Checking presents an enforcement problem when applied to a ship moving within port limits and with the machinery operating at various powers.

However, controls will come into force generally and the IMO has drawn up a timetable of recommended limits.

Crossheod Diesel Engines Past months have seen feverish activity in ordering very large and fast containerships, maximum capacity having now exceeded 5,000-TEU in the most recent contract for five 5,046-TEU, 24.5-knot ships for Hyundai Merchant Marine of South Korea. These will be built and engined in the associated Hyundai Heavy Industries plant at Ulsan. Vessels of this order call for machinery of the highest output and the engines specified are the recently uprated Mark V versions of MAN B&W's 12-cylinder 12K90MC-C model, currently the most powerful available on the market. This has an MCR of 54,720 kW (74,520 bhp) at 104 rpm, and will probably be operated at about 47,000 kW (64,000 bhp) on the long continuous runs across the Pacific, if the same margin is applied as in the six 4,400-TEU Hyundai ships of late 1992 and last year. New Sulzer Diesel is enjoying considerable success with its most powerful containership model, the RTA84C, having two ships in service with 12 cylinders and 11 more on order, including one for six with an MCR of 48,600 kW (66,120 bhp) for ultra- Panamax 4,960-TEU ships ordered by Oriental Overseas Container Line in Japan and South Korea. The most popular size is the nine-cylinder version, of which 36 have been ordered.

Although specifications of proposed 6,000-TEU ships have already been circulated, it is felt that the present range of engines will suffice, unless a strongly competitive element arises in the freight market, in which case resort will have to be made to twin-screw propulsion.

These large engines are increasingly adopted for central electricity- generating stations serving island populations; the wider market helping to spread development costs.

Mitsubishi has its first examples of large faster-running engines at sea in containerships, a new class of Norasia vessels built in Germany of open-hatch design with innovative rain shelters.

These have Mitsubishi 7UEC85LSC engines of 29,290 kW (37,100 bhp) at 102 rpm, moderated to 90 percent for a continuous sea speed of 22.5 knots. The UEC33 engine, introduced in replacement of the 370mm bore model, has also been sent to sea, in a day-cruising ship.

The smaller-bore crosshead engine sells very well in Far Eastern markets for large coasters and inter- island traders. MAN B&W is making a bid for sales in Europe, offering models with two-cylinder sizes as robust and economical alternatives to the medium-speed engine.

Both the 35MC and the 42MC have been redesigned as S-prefix models, to incorporate most of the piston strokes so that propeller speeds more nearly match those of a comparable medium-speed engine and gearbox.

While more expensive, a longterm economic balance taking into account potentially greater cargo space due to the shorter plant, lower fuel consumption, maintenance and spares shows to advantage in a number of situations which are the usual application for geared machinery: large coasters, small tankers and container feeder ships.

The S42MC has a stroke/bore ratio of 4.2:1, the highest of any production engine today. It is to be made with from four to 12 cylinders, developing 1,025 kW (1,395 bhp) per cylinder at 136 rpm.

The crosshead diesel engine is universally adopted for propelling large tankers. It is estimated that 30 to 40 VLCCs will have been scrapped by the year's end, leaving 450, of which a number are known to be unacceptable to the leading oil companies.

Some 25 new VLCCs will have come into service, leaving a substantial market to be met.

Recent developments by Sulzer, MAN B&W and Mitsubishi now enable an engine to be run at near the MCR on loaded voyages, and immediately and readily tuned for optimum performance and much reduced power for the return lightdraft passage.

This is achieved by electronic intervention of the fuel injection and has exchange timings.

Medium-Spaed Diesels The medium-speed diesel engine builders have not been idle. A number of European makers have presented entirely new models,and others have introduced significant modifications of existing engines. All three crosshead engine builders have important medium-speed activity, notably MAN B&W with its home base in Augsburg building a successful range of three sizes of geometrically similar heavier models (joined recently by the junior 32/40 series) and the popular 230 and 280mm bore models from Frederikshavn and Holeby in Denmark.

In each case, the new engines have been designed to reduce emissions, improve economy and simplify the manufacturing process.

The Stork-Wartsila SW38—with a 380mm cylinder bore and a 475mm piston stroke of660 kW per cylinder at 600 rpm, developmed at the Zwolle works with the backing of the Wartsila Diesel Group — will ultimately take over from the popular and long-lived TM410 series. Available in models from six to 18 cylinders, the engine covers an output range from 4,000 to 12,000 kW.

Orders have been received, and se- ries production is ready in Amsterdam in the factory on the historic site of Werkspoor, one of Dr. Diesel's original seven licensees at the turn of the century.

Krupp-MaK presented its M32 at Kiel, a middle-weight model available in models from six to 16 cylinders in a power range from 2,640 to 7,040 kW at 600 rpm. (The shorter stroke vee engines run at up to 750 rpm). These engines will have optional equipment for rephasing the camshaft timing, to maintain optimum efficiency with reduced emissions, over a range of speeds and fuel quality.

MAN B&W's offering, the six- to nine-cylinder L 32/40 range is in production and examples are already at sea. This is the model which features a camshaft dedicated to actuating fuel pumps, and another at the back of the engine for controlling the gas exchange events, both of them with provision for rephasing the timing.

The designation SEMT-Pielstick PC2-6B does not sound like that of a new model, but in fact covers the first PC2 engine to have cylinder dimensions different from the 400 mm by 460mm used by Dipl.-Ing.

Gustav Pielstickas far back as the early 1950s. The PC2-6B develops 630 kW/cyl. at 530 rpm, and four 18- cylinder engines have been specified for the new and largest French mainland to Corsica ferry building at St. Nazaire. All in-line and veeform models will have cast iron frames for stiffness and lower noise emission values. The cylinder liner is carried directly in the frame, and not within its own jacket, and cooling is applied only at the upper part and through bored passages at the top. The Deutz-MWM 632 series is a faster-running 255mm x 320mm model to cover a range of powers from 1,440 to 6,330 kW. This is another which fills a gap in the builder's power/speed plan. Perhaps the most interesting item in this connection is that all of the veeform versions will be assembled at a new plant being set up in Grove City, Pa., in cooperation with General Electric Transportation System.

From Japan has come news that the five-year development program of a very highly rated medium-speed engine, to develop 1,485 kW per cylinder, has been concluded with trials sufficiently promising to lead to production. No physical details have been released, but high claims are made for reliability; fuel consumption (10 to 15 percent lower); bmep (20 to 50 percent higher); piston speeds up to 12m/s; and specific weight (40 to 50 percent lower). The remarkable advances in bmep and piston speed have been achieved by applying porous ceramic shielding to the piston crowns, and anti-wear and high-slip ceramic plasma coatings to the cylinder liners and piston rings. This development has been undertaken jointly by Mitsui, Kawasaki and Hitachi, supported by a number of government agencies.

Mgh SpMd Diesels A Gas TerMees The large and fast lightweight ferry for passengers and cars has rapidly become a significant factor in certain areas of marine transportation.

These craft are weight-sensitive and require concentrated levels of power which can only be met by high-performance diesel engines and/or aero engine-derived gas turbines, generally driving water jets due to their shallow draft.

MTU can provide diesel engines of high power. The two Tirrenia ferries each have two of the lates 16V 595 engines driving the outer, steerable water jets and an MTUGE LM2500 gas turbine driving the center one. Engines of lower output already in service have been supplied by Ruston, Caterpillar, Deutz MWM, Niigata and Mitsubishi.

The GE family of gas turbines is well established at sea in the navies of many countries. Next year the first of the Stena HSS light alloy catamarans will enter service across the Irish Sea. Very large, these craft will carry 1,500 passengers and 375 cars (or 50 trucks and 100 cars) at speeds up to 40 knots, propelled by one LM2500 and one LM1600 GE gas turbine coupled in a unique COGOG configuration to drive two KaMeWa water jets in each hull, a total of 80,000 kW.

Three HSS' are on order from Finnyards, and the turbine modules and installations are in the hands of Kvaerner Energy A/S of Norway, a long-time GE manufacturing partner.

The Pratt & Whitney Turbo Power & Marine Div. has returned to the scene. The company will supply the "core" gas generator for the Mitsubishi 24,280-kW MFT-8 gas turbine which will be installed in the half-scale prototype Techno Superliner, a 1,000-dwt, 50-knot freight carrier.

Smaller turbines are the Solar Taurus of 5.2 MW for five TriCat ferries, and the Textron Lycoming TF-40, a 3,000-kW unit already in service and specified for three Hong Kong ferries. Ulstein's 2.6 MW Eurodyne is completing its prototype trials.

i l M l r k D r i v e s With few exceptions diesel-electric propulsion has been specified for all of the larger cruise ships placed on order during the past two years; not for the reasons of its brief popularity 60 years ago when it was offered as a means of overcoming then-prevalent problems, but in its own right for the very clear advantages which it offers.

A cruise ship, as opposed to the vanished passenger liner, has an operating regime which calls for a wide range of speeds — running fast out to warmer waters and thereafter perhaps at very moderate speeds over short distances between venues on the cruising grounds.

The amenities expected today make a heavy demand on auxiliary power for hotel services and air-conditioning all the time that passengers are on board, which is almost continuously, between docking periods.

The high-powered bow and sternthrusters which enable these larger ships to enter and anchor safely in confined harbors and bays without tug assistance represent another demand.

It is only in recent years that the "power station" principle, in which there are no dedicated auxiliary generators, has been developed.

This highly-flexible arrangement of several generators, of the same or different outputs and driven by medium-speed diesel engines, enables the full range of power requirements from high speed in tropical waters to harbor in temperature climates to be accommodated by running the minimum number of sets under the optimum load conditions.

A modern power management system maintains this state, while keeping the minimum "spinning reserve" to meet any naviga- tional emergency requirement for sudden increase of speed or crashastern.

Electric transmission was once popular in ferries for the ease and flexibility of maneuvering which the system offered, benefits later conferred by the combination of engines of higher unit power and controllable- pitch propellers.

However, a contract placed with Finnyards for two advanced trailer ferries to operate in the environmentally- sensitive waters between Germany, Denmark and Sweden has been specified with diesel-electric machinery powered by four MaK 6M 552 engines burning a low-sulfur MDO grade of fuel. This order is of significance, as it marks the return of one of the major participants to this field, after a number of years of absence.

The propulsion outfit will be supplied by Systemtechnik Noord (STN) whose subsidiary AEG, notable for several important installations in the past, will provide the larger rotating machinery for the large Costa Cruises ship placed recently with the Vulkan Group. This will have six MAN B&W 58/64 engines, three with six and three with seven cylinders and two 15 MW AEG propulsion motors. Provision for abating exhaust emissions will be incorporated.

Electric transmission has also been revived as a medium for powering tankers, specifically those which have a need for power in addition to propulsion. Auxiliary generators are unnecessary since energy can be obtained from the main machinery via an extension of the switchboard.

It is well-suited to product carriers having a multiplicity of cargo tanks, each with its own motor- driven deepwell pump and segregated discharge system. An order for seven 37,000-dwt Stolt-Nielsen product tankers for delivery from late 1995 to late 1997 was placed during the year with Danyards.

They are to have generators, control gear and motors supplied by Cegelec (GEC Alsthom).

Shuttle tankers serving offshore oil production sources are ideal applications as, while approaching a loading buoy and throughout the time they are connected by hose, they must have reserves of power immediately available for the screw(s) and thrusters in order to keep station. To date all those on order in Spain and the Far East are North Sea operations and will have electrical plant by ABB Marine Drives of Finland. A topical application of electric drive is seen in the current uprating of three nine-yearold Sea-Land containerships by Blohm + Voss, in Hamburg. They are required to operate on a new trans-Atlantic service, but in their original state — as former USL econoships — they were too large and much too slow. They have been "cut and shut" by removing s section of three x 40-ft. cells from the parallel body amidships, reducing the capacity from 3,900 to 3,000 TEU.

A new and much finer forebody with a bowthruster was fitted, and the power on the shaft was increased by some 4,000 kW, the net effect being to raise the speed from 18 to 21 knots. The machinery uprating was a major physical problem as the engine room, containing a 20,500- kW 7RLB90 Sulzer engine, and set as far aft as possible, was very short and offered no space for a source of additional power. The solution adopted was to install a 4,860-kW 6.6 kV generator, driven by a 12- cylinder Wartsila Vasa 32E engine, together with auxiliaries and switchboard at upper deck level within the port side casing which supports the superstructure. There was no possibility of using a shaft-riding motor, as was the case with MOL ships three years ago, but a Lohmann & Stolterfoht verticallystepped "tunnel gear" was shoehorned into the narrow space immediately aft of the engine, with the 4,000-kW, 1,200 rpm driving motor above. The fixed propeller was changed for a KaMeWa cp one, enabling the plant to be run at a constant 102 rpm, with ship speed adjusted by changing the propeller pitch. The switch and control gear was thus greatly simplified. The generator was able to supply the 1,800 kW KaMeWa bowthruster, as the motor would not be required when maneuvering. ABB Marine Drives were responsible for this booster drive.

S t s u i i t Steam's last grasp of the marine propulsion market lies in the LNG tanker for which, except for one ship with a Sulzer crosshead engine and one with a General Electric (GE) heavy duty gas turbine, built some 20 years ago and no longer in service, it has been adopted exclusively.

In spite of very heavy investment in full-scale R&D by the leading diesel engine manufacturers of both slow-running and mediumspeed engines, no ships have been ordered with internal combustion machinery; the long-term economics of operating these very costly ships having shown no advantage.

They can burn the inevitable and continuous boil-off of the cargo under the boilers at sea and also in harbor when means might otherwise have made for disposal as burnoff ashore. Excess steam generated in harbor is passed to a dump condenser.

What is perhaps surprising is that steam turbines of only 12,500 shp were specified for a small distributive LNG tanker, built by NKK for operation on the Malaysian coast; another has been ordered in recent months.

Although a dozen large LNG tankers are on order in European yards and there are several concerns in Europe which have an illustrious past reputation for building steam turbines, none until a few weeks ago has shown any interest in reviving this activity. This, in spite of a forecast demand for a considerable volume of LNG newbuildings. Hitherto, all the turbines have been placed with Japanese engine builders Kawasaki and Mitsubishi, a duopoly broken recently by a contract for an LNG carrier and steam turbine machinery placed in Italy by the state natural gas enterprise Snam. The turbines and gears will be built to a GE design by the CNR Riva Trigoso engine works of Fincantieri, hitherto engaged in the construction of machinery for CODOG frigates and destroyers.

Other stories from September 1994 issue


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