Sulzer Common Rail

Experience with Sulzer Common-Rail Engines* Kaspar Aeberli Director, Marketing & Sales Support, Marine Wärtsilä Switzerland Ltd, Winterthur

Summary The paper outlines the new Sulzer RT-flex60C which is the world’s first low-speed marine engine to be designed and built from the outset with electronically-controlled common-rail systems for fuel injection and valve actuation. Reference is made to the building and testing of the first RT-flex60C engines in Italy and Korea. As the Sulzer RT-flex common-rail system is radical new technology for low-speed marine diesel engines, the paper also reports on the service experience with the first series-built Sulzer RT-flex engine; namely the Sulzer 6RT-flex58T-B engine which entered service in September 2001 in the bulk carrier “Gypsum Centennial” and has already exceeded 7500 running hours. The Sulzer RT-flex engine programme has recently been extended to lower powers with the new Sulzer RT-flex50 engine and to the higher powers with adaptation of well-established large-bore engines of the Sulzer RT-flex96C and RT-flex84T-D types for the largest container liners and tankers.

Introduction The major steps in marine diesel technology have been surprisingly few: the two-stroke engine cycle in about 1905, airless fuel injection in the 1930s, welded construction in the late 1940s, and exhaust-gas turbocharging and the use of heavy fuel oil both in the 1950s. Now we have another major step – electronicallycontrolled common-rail fuel injection, introduced in the Sulzer RT-flex engines. Although common-rail fuel injection is itself not new, the addition of integral electronic control allows full use to be made of the flexibility possible with common-rail injection. This makes the Sulzer RT-flex engines the most advanced lowspeed marine engines available in the world today. The Sulzer RT-flex electronically-controlled commonrail system has already been well described [1, 2, 3]. However, note should be made of some key dates, see Table I. It is ten years since development of the Sulzer RT-flex common-rail system began and more than 20 years since the first tests were made with electronically-controlled fuel injection in Winterthur. The change in injection concept from individual, hydraulically-operated fuel injection pumps to a commonrail system in 1993 was made because the system with individual pumps did not offer potential for further technological development despite it having integral electronic control. Electronic control was seen as insufficient, a new fuel injection concept was recognised as

essential. Common rail was seen as the road ahead. The latest step in the above chronology is particularly significant as the Sulzer RT-flex60C engine is the first large low-speed marine diesel engine designed from the Table I: Some key dates 1981: First tests with electronically-controlled fuel injection on a Sulzer low-speed engine, using individual, hydraulically-operated fuel injection pumps. 1990 March: World’s first multi-cylinder electronically-controlled uniflow two-stroke engine is started on the Winterthur test bed. Tested until 1995. 1993: Project started to develop the Sulzer RT-flex common-rail system. 1996: Component testing began for the Sulzer RT-flex common-rail system. 1998 June: Starting of the first Sulzer RT-flex fullscale engine on the Winterthur test bed. 2000 February: Order for the first series-built Sulzer RT-flex engine. 2001 January: Official shop test of the first seriesbuilt Sulzer RT-flex engine, the Sulzer 6RT-flex58T-B in Korea. 2001 September: Sea trials of the “Gypsum Centennial” with the Sulzer 6RT-flex58T-B engine. 2002 October: Official shop test of the first Sulzer RT-flex60C engine.

* Paper presented at The Motor Ship Marine Propulsion Conference, Hamburg, 7–8 May 2003. —1—

© Wärtsilä Corporation, May 2003

bedplate up solely as an electronically-controlled engine with common-rail fuel injection. In fact, it is not available in any other form. When the new 600mm-bore engine was announced in mid 1999, it was envisaged that it would be primarily built as a conventional engine with camshaft-actuated fuel injection pumps, etc. However, the full-scale tests with the new RT-flex electronically-controlled common-rail system were progressing so well that it was decided to complete the design of the new 600mm-bore engine solely in the RT-flex60C form.

The Sulzer RT-flex60C The market need for a new Sulzer two-stroke engine design in the region of 600 mm bore was seen a few years ago when there was an increasing number of container liners of 5500 TEU capacity or larger being ordered. It was evident that there would be a growing market for container feeder vessels to serve these larger container liners, and also that the sizes of feeder vessels would tend to become larger, perhaps in the capacity range of 1200– 3000 TEU. Market research among shipowners and shipbuilders showed that the various sizes of feeder vessels envisaged would need compact engines in the power range of around 12,000 to 19,000 kW for the envisaged range of ship speeds. There was clearly a need for more power than is available from the RTA62U-B type, and with a higher shaft speed than the RTA58T-B engine type. Thus the decision was made to introduce the Sulzer RT-flex60C which would cover the required power range with five to eight cylinders at an output of 2360 kW/ cylinder. The nine-cylinder model was added later to extend the power range to 21,240 kW. The rotational speed selected, 114 rev/min, is a little faster than would be ideal hydrodynamically for suitable propellers but it was

Fig. 1: Cross section of the Sulzer RT-flex60C engine. [02#064] selected as the best fit between the priorities of operating and manufacturing costs. As usual for low-speed engines, the installed maximum continuous power of the engine can be freely selected over a layout field down to 70 per cent nominal power and 80 per cent nominal speed to give flexibility for exactly matching individual ship requirements.

Fig. 2: Sulzer 7RT-flex60C engine in Wärtsilä’s Trieste factory. [03#023]

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Table II: Principal parameters of the Sulzer RT-flex60C engines Bore Stroke Output, R1 Speed range, R1–R3 BMEP at R1 Pmax Mean piston speed at R1 Number of cylinders BSFC: at full load, R1 at 85% load, R1

mm mm kW/cyl bhp/cyl rpm bar bar m/s

600 2250 2360 3210 114–91 19.5 155 8.55 5–9

g/kWh g/bhph g/kWh g/bhph

170 125 167 123

The new RT-flex60C engine is equally well suited to vessel types other than container carriers, such as reefers, large Ro-Ro vessels and large car carriers with similar requirements for engine power and rotational speed. The height of the RT-flex60C, 8.52 m overall above the shaft centreline, is particularly advantageous for such vessels. The piston withdrawal height of 10.4 m to the hook can be reduced by special lifting tools. Shipbuilders in East Asia have also shown an interest in employing the RT-flex60C in bulk carriers and tankers, for which there is a tendency to operate at higher ship speeds.

Sulzer RT-flex Common-Rail System This Sulzer RT-flex engine is basically a standard Sulzer RTA low-speed two-stroke marine diesel engine, except that, instead of the usual camshaft and its gear drive, fuel injection pumps, exhaust valve actuator pumps and reversing servomotors, it is equipped with a common-rail system for fuel injection and exhaust valve actuation, and

fully-integrated electronic control. The key feature of the RT-flex system is that it gives complete freedom in the timing and operation of fuel injection and exhaust valve actuation. This flexibility is employed to obtain benefits in terms of reduced engine running costs, less exhaust emissions and steady operation at very low speeds. Additionally, redundancy is a natural key feature of the common-rail concept, giving safety and reliability. Reduced running costs The reduced running costs come from reduced maintenance requirements and a lower part-load fuel consumption. The fuel saving, however, is limited by the need to comply with the NOX regulation of the MARPOL 73/78 convention. Maintenance costs become more predictable through better balanced operation and better retention of engine settings over many running hours. Excellent balance in power developed between the different engine cylinders and from cycle to cycle is provided by the common-rail system with its volumetric control. As engine settings are made electronically, the ‘as-new’ settings are retained so that engine performance such as fuel consumption does not deteriorate over time. The better running of the engine will also make for better prediction of maintenance timing and allow times between overhauls to be extended. Smokeless operation A clearly visible benefit of RT-flex engines is their smokeless operation at all ship speeds. This was well demonstrated during the sea trials of the “Gypsum Centennial”. The superior combustion performance with the common-rail system is achieved by maintaining the fuel injection pressure at the optimum level right across the engine speed range. In addition, the selective shut-off of single injectors and an optimised exhaust valve timing help to keep smoke emissions below the visible limit at very low speeds.

Fig. 3: Cylinder tops of the 7RT-flex60C engine with the side panels of the rail unit open for access. [03#031]

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Lower running speeds Sulzer RT-flex engines also have the advantage of steady running at lower speeds than engines with mechanicallycontrolled injection. This is made possible by the precise control of injection, together with the higher injection pressures achieved at low speed, and the sequential shutoff of injectors. The result is that RT-flex engines can run very steadily, and without smoking, at 10–12 per cent of nominal speed. This has been well confirmed in service in the “Gypsum Centennial”. High reliability and redundancy Although particular attention has been given to making the RT-flex system reliable, the common-rail concept has great reliability through inherent redundancy. The multiple fuel and servo oil supply pumps have adequate redundancy for the engine to deliver full power with one fuel pump and one servo oil pump out of action, and a strictly proportional reduction in power should further pumps be out of action. High-pressure fuel and servo-oil delivery pipes, and the electronic systems are also duplicated for redundancy. Sulzer RT-flex installation Fig. 4: The RT-flex supply unit on the first 7RT-flex60C with fuel pumps to the right and servo oil pumps to the left of the gear drive. [03#040]

Fig. 5: Gear drive for the supply unit in the RT-flex60C showing how second-order balancer masses may be added to the intermediate wheels. [02#180]

The RT-flex system is seen on the engine as two principal elements: the supply unit on the side of the engine and the rail unit along the side of the cylinder covers. There is also a filter unit for the servo oil. For the first two RT-flex60C engines, the supply unit is arranged low on the manifold side but subsequent engines have it higher on the opposite side. This keeps the engine ‘footprint’ small so that RT-flex60C engines can be located far aft in ships with fine afterbodies. In the supply unit, a number of high-pressure pumps deliver heated fuel at the usual pressure ready for injection. The pumps have suction control to regulate the fuel delivery volume according to engine requirements. Servo oil for injection control and exhaust valve actuation is provided at a lower pressure by a number hydraulic pumps also on the supply unit. Fuel is delivered from the common rail through an individual injection control unit for each engine cylinder to standard fuel injection valves. The control units, using quick-acting Sulzer rail valves, regulate the timing of fuel injection, control the volume of fuel injected, and set the shape of the injection pattern. The three fuel injection valves in each cylinder cover are separately controlled so that, although they normally act in unison, they can also be programmed to operate separately as necessary. The exhaust valves are operated in much the same way as in existing Sulzer RTA engines by a hydraulic pushrod but with the actuating energy now coming from a servo oil rail at 200 bar pressure. The electronically-controlled actuating unit for each cylinder gives full flexibility for valve opening and closing patterns. This unit utilises exactly the same Sulzer rail valves as are used for controlling fuel injection.

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The Core Engine However, a new marine engine, such as the RT-flex60C, needs more than electronically-controlled fuel injection to ensure satisfactory performance and service behaviour. It needs, at its core, to be a good basic engine. For example, attention to piston-running behaviour is essential for engine reliability and long times between overhauls. For this reason the RT-flex60C incorporates TriboPack technology. This comprises a combination of design measures, including deep-honed liners of appropriate material with sufficient hard phase, multi-level lubrication, pre-profiled rings in all four piston grooves, chromium-ceramic coating on the top ring, anti-polishing ring at the top of the liner, increased thickness of chromium layer in the piston ring grooves, insulating tubes in the cooling bores of the liner, and mid-stroke liner insulation according to the engine rating. Most of the TriboPack design measures have been in employed in Sulzer RTA engines with good effect. However, it has been proven in service that only the complete package brings the full benefits. Thus TriboPack was introduced in 2000 for all Sulzer RTA engines. It is expected that this approach will enable times between overhauls to be extended to at least three years.

Fig. 6: Three-dimensional finite-element model for the RT-flex60C. [02#063]

Optimised structural design, minimum length In the design of the RT-flex60C, careful attention was also paid to the structural design to achieve a reasonable engine weight, economy in manufacturing and above all safety. The RT-flex60C follows other Sulzer RTA engines in having a very rigid structure comprising a fabricated bedplate, fabricated box-type columns and cast cylinder block, all secured by pre-tensioned vertical tie rods. The structural design is based on extensive stress and strain calculations using a full three-dimensional finite-element model and always confirmed by strain gauge measurements on the first engine. Careful consideration was also given to the structure to ensure that welding and casting quality can be good. Certain features in the arrangement of the thrust bearing as well as the crankshaft and connecting rod bottom ends have been employed to minimise the length of the RT-flex60C Improvements in basic diesel engine technology Minimising engine length has had an influence on bearing design. All bearings – main, bottom and crosshead – are fitted with thin shell bearings having a white-metal running layer. Similar bearings are now standard in the latest version of the RTA-8T engines, and are running well. However, with the flexibility of the thin steel shells of the main bearings, it proved necessary to improve the geometry of the bearing housings. Thus the main bearing bores are machined with the bearing caps in place and tightened. The main bearings each have four elastic holding-down studs. Two pairs of studs give the most even distribution of holding-down load and also allow the tie

measured +/- 17 calculated +/- 18 measured +/- 14 measured +/- 19 calculated +/- 21

Fig. 7: Comparison of calculated and measured stresses in the RT-flex60C bedplate. [03#077] rods to be located close to the bearing for efficient transfer of firing pressure loads. The design also allows aluminium bearings to be incorporated at a later date. The cylinder covers are secured by eight elastic holding-down studs arranged in four pairs. This arrangement is compact, so helping to achieve a short engine length, while giving good security and accessibility. There is a support ring between the cylinder block and the collar of the cylinder liner, thus carrying both the liner and the cylinder cover. It also passes cooling water to the cooling bores and to the cover. —5—

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measured ±47 calculated ±46

measured ±70 calculated ±69

Fig. 8: Comparison of calculated and measured stresses in the crankshaft fillet of the RT-flex60C. [03#078]

Fig. 10: Combustion space of the RT-flex60C. [02#193]

The combustion space of the RT-flex60C follows wellestablished Sulzer RTA practice. All the surrounding components are bore cooled. The piston crown employs the usual jet-shaker oil cooling principle with an arrangement of cooling bores in the crown so that the surface temperatures of the crown are moderate with a very even distribution. Scavenge air is delivered by the latest generation of turbochargers, the TPL-B from ABB Turbo Systems and the equivalent from other manufacturers. The scavenge air receiver is of a simplified and modular design with integral non-return flaps, hanging cooler bundles and two auxiliary air blowers. The receiver also incorporates, after the scavenge air cooler, a new design of water separator of higher efficiency than in other Sulzer RTA engines. Removing all water condensate from the air before it enters the engine cylinders has proven vital for satisfactory piston running. There are ample drainage provisions to remove completely the condensed water collected at the bottom of the air cooler and separator. To avoid blow-back through the drains from the higher pressure areas, all the drains are collected at the bottom of a vertically mounted pot which is filled with water and kept under scavenge air pressure. Drain water then leaves from the top of the pot with an orifice controlling the discharge. This arrangement has no moving parts.



Fig. 9: Close-up of a crankshaft fillet on the RT-flex60C. [02#099]

Fig. 11: Component surface temperatures measured around the combustion chamber of the 7RT-flex60C at the full-load R1 rating. [03#079]

First RT-flex60C Engines The first pair of Sulzer RT-flex60C engines were specified by Agricultural Export Co (Agrexco) and Münchmeyer, Petersen GmbH & Co KG for the propulsion of two 13,200 tdw containerised reefers contracted in Portugal towards the end of 2000. Each seven-cylinder RT-flex60C engine has a maximum continuous power of 16,520 kW at 114 rev/min. The engines were built at Wärtsilä’s Trieste factory. The first engine completed its official shop test on 14–15 October 2002. —6—

© Wärtsilä Corporation, May 2003

The second engine successfully passed a type approval test on 17–20 December 2002. This test was witnessed by the representatives of the classification societies, as well as the shipowners and shipbuilder. Four similar 7RT-flex60C engines are also being built under licence at Hyundai Heavy Industries Ltd in Korea for four 30,000 tdw multipurpose carriers contracted at Shanghai Shipyard in China by Chinese-Polish Joint Stock Shipping Co (Chipolbrok). The first two of these engines successfully passed their official shop tests on 22–28 January and 6–7 March 2003.

October 2002, the RT-flex system has received full classification society approval for general application in ships.

Service Experience with “Gypsum Centennial” In parallel with the building and testing of the Sulzer RTflex60C, service experience has been accumulating with the first RT-flex engine. This is a 6RT-flex58T-B engine which passed its official shop test in January 2001 and is installed in the 47,950 tdw bulk carrier “Gypsum Centennial”. The ship was built for her owners Gypsum Transportation Ltd (GTL) of Bermuda by Hyundai Mipo Dockyard in Ulsan, Korea. The Sulzer RT-flex main engine has a maximum continuous output of 11,275 kW at 93 rev/min. The ship was delivered in September 2001 and the service experience with the engine has since been very good, with currently more than 7500 hours’ operation. This Sulzer 6RT-flex58T-B is the world’s first seriesbuilt large low-speed engine with electronically-controlled common-rail fuel injection. It must be remembered that this engine was built to operate using only the electronically-controlled common-rail system with no alternative. It went to sea as a fully industrialised product fully capable of continuous heavy-duty commercial operation. It achieved this performance with very good success. Sea trials of the ship were run during 12–18 September 2001. During the trials, the Sulzer RT-flex engine ran very satisfactorily, coming fully up to expectations without causing any delays in the trials. The ship, however, did not leave the shipyard until 15 November 2001 owing to delays in completing other aspects of the ship. After her delivery voyage, she began commercial service on 5 December 2001. Throughout the engine has basically run very

Testing of the RT-flex60C engines The four RT-flex60C engines so far tested have been put through the usual test programmes for new engine types. For all four engines, initial tests runs were employed to optimise the turbocharging and fuel injection equipment. The usual test measurements were taken as for all production engines to confirm their predicted performance in terms of power, speed, fuel consumption, etc. However, the first two engines were subjected to further tests with measurements of component stresses and temperatures to confirm design calculations. An important part of the test programmes was final adjustment and thorough testing of the RT-flex systems, particularly of their electronic control systems. During the tests, the four engines all performed as expected. The electronic systems were noticeable stable. The engines could be started, stopped, manoeuvred, taken up to load and unloaded without any hindrance. Type approval for RT-flex system The 6RT-flex58T-B engine of the “Gypsum Centennial” entered service with individual approval for the RT-flex system from the classification society Lloyd’s Register of Shipping. However, following the successful type approval test of the second Trieste-built RT-flex60C engine in Shutdowns Faults

4

1

14 12 10 8 6 4 2 0

15 Nov 2001 Start of delivery voyage

16

18 Sep 2001 Sea trials completed

Fig. 12: History of all faults which have occurred in the RT-flex system of the main engine of the “Gypsum Centennial” to the end of February 2003. Faults are defined as events which trip an alarm signal. [03#080]

2

New fault types Repeated faults

Dec 2001

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Feb 2002

Apr

Jun

Aug

Oct

Dec

Feb 2003

© Wärtsilä Corporation, May 2003

successfully. All the problems experienced can be regarded as ‘teething’ problems since all the new cases occurred during the early months of service. In the following months the faults have been few, and the causes are understood. In most cases the problems have been remedied, or new components are under development. It is notable that the ships’ engineers quickly became acquainted with the RT-flex system. They have been operating the engine without a Wärtsilä engineer since the end of May 2002. The fault history differentiates between new faults and repeated cases of the same problems. The number of repeated faults arose through the usual delays in developing final solutions. Existing spare parts were also used until improved parts became available. The fact that the whole design of the common-rail system was made ‘in-house’ proved invaluable when troubleshooting problems. In-house knowledge allows quick diagnosis of problems and prompt identification of suitable remedies. The great majority of the problems did not interfere with normal ship operation as they caused either an alarm or the engine to slow down. Some faults were rectified during normal engine halts while the majority, concerning common-rail and electronic components, could be rectified by briefly slowing the engine and replacing components. Six unplanned shutdowns occurred in the first couple of months’ operation, but since then there has only been a single stoppage. Problems with sensors occurred mainly concerning the right specification and securing the sensor against the local environment. A number of slowdowns arose through failure of electronic valve drive modules. The problem was resolved by replacing them with printed circuits having a revised layout for lower thermal stresses in electronic components. In October 2002, the engine was inspected in Tampa, Florida, as part of the ship’s guarantee docking after her first year’s service, 5295 running hours. The engine was found to be in good condition. The few shortcomings could all be corrected. The RT-flex system was thoroughly inspected to assess the condition of all hardware. Certain components were exchanged for later detailed inspection in Winterthur. The opportunity was also taken to exchange components for new, improved designs where appropriate. For example, the control oil pumps which had failed in service were replaced by a new design, and given elastic mountings and flexible hoses. The roller guide of a fuel pump was found to be seized. The problem was insufficient clearance between the roller guide and its casing. These components were thus renewed. This and previous exchanges meant that all fuel pumps were then of fully-modified design. Since the guarantee docking, the RT-flex engine has run well, behaving much as it had done during the months immediately before the docking inspection.

Experience from the core engine The traditional parts of the engine have operated well. The only disturbance had been in two of the main bearings. The engine had been equipped with the original design of main bearings and during the drydocking two bearings were replaced by shells of the revised design. The good piston-running behaviour deserves particular mention. This is the result of the proven TriboPack design measures together with the optimised fuel injection of RT-flex technology. TriboPack design measures are now standard for Sulzer RTA-series engines to give improved piston-running behaviour. Cylinder No.1 was opened at the docking. The maximum diametrical liner wear was measured at 0.01 mm/1000 hours, and the maximum radial ring wear was 0.055 mm/1000 hours. At the time of the drydocking, the cylinder oil feed rate was 1.2 g/kWh. The liner surface was in perfect condition, as were the piston rings. There was only moderate carbon build-up above the top ring, while the grooves and the areas between the rings were completely clean. Improved piston running The good piston-running results from the above engine are representative of the increasing numbers of Sulzer RTA engines entering service with TriboPack. TriboPack is now in service in 527 cylinders in 66 engines from 480 to 960 mm bore. They have up to 28,000 running hours. The engines are all reported to have uniformly excellent wear rates. Measurements from engines in service with TriboPack show that the maximum specific liner wear generally comes below 0.03 mm/1000 hours. The cylinder oil feed rates with these engines are in the range of 1.0–1.4 g/ kWh. Most notably, there have been no cases of scuffing The lack of scuffing and the uniformly low wear rates confirm the stability of piston running which is necessary for long TBO and good reliability. The service results confirm that three years’ TBO can now be routinely achieved and even exceeded.

Extension of the RT-flex Programme The excellent experience with the Sulzer RT-flex system, both in the research engine since June 1998, in the shop testing of now two 6RT-flex58T-B and four 7RT-flex60C engines, and in the shipboard service of the first 6RT-flex58T-B since September 2001 has encouraged Wärtsilä to extend the Sulzer RT-flex engine programme to both lower and higher powers. The objective is to offer a comprehensive programme of low-speed engines with electronically-controlled common-rail systems. Sulzer RT-flex50 Following the RT-flex58T-B and RT-flex60C engines, the first addition to the programme is the new Sulzer RT-flex50 engine which is currently being developed.

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Table III: Sulzer RT-flex engines delivered and on order No. 1

Model 6RT-flex58T-B

2 4 1 2 3 4 2

7RT-flex60C 7RT-flex60C 6RT-flex58T-B 5RT-flex58T-B 9RT-flex60C 12RT-flex96C 8RT-flex96C

Shipowner Gypsum Transportation Agrexco Chipolbrok Scinicariello Andromeda Safmarine Blue Star H. Dauelsberg

Ship type Bulk carrier

Shipbuilder Hyundai Mipo

Eng.builder Hyundai

Container/reefer Multipurpose Tanker Prod. tanker Container Container Container

ENVC/Portugal Shanghai Sumitomo Jiangdu Yuehai Volkswerft IHI Marine United Hyundai H.I.

Trieste Hyundai DU Yichang HSD DU Hyundai

The RT-flex50 is being adapted by Wärtsilä from the conventional 500 mm-bore engine with camshaft-based fuel injection, etc., being jointly developed by Wärtsilä and Mitsubishi Heavy Industries Ltd. Of 500 mm bore by 2050 mm stroke, the RT-flex50 has a maximum continuous power of 1620 kW/cylinder at 124 rev/min. With five to eight cylinders, it will cover a power range of 5650–12,960 kW at 99 to 124 rev/min. It thus offers the right powers and speeds for a wide variety of ship types including the new generation of Handymax and Panamax bulk carriers, large product tankers, container feeder vessels and medium-sized reefer ships. The first Sulzer RT-flex50 engine is scheduled to begin testing in the fourth quarter of 2004. Sulzer RT-flex96C and RT-flex84T-D The RT-flex concept will also be extended to the highest powers with the Sulzer RT-flex96C and RT-flex84T-D engines. The RTA96C engine type has been popular for the propulsion of container liners. Some 139 RTA96C engines are now in service or on order. They currently extend from seven-cylinder engines of 40,040 kW in 3000 TEU ships to the 68,640 kW 12-cylinder engines for the largest ships of more than 8000 TEU. The RTA84T engine type is employed solely for the propulsion of VLCCs and ULCCs, predominantly in the seven-cylinder model. The current 7RTA84T-D gives 28,700 kW. The benefits of the RT-flex engines – smokeless operation, better fuel economy, reduced maintenance and lower steady running speeds – will certainly be attractive for both types of ship types. The first RT-flex96C engine is scheduled for shop testing in April 2004, with delivery in the ship towards the end of 2004. The first RT-flex84T-D can be built in mid 2005, according to market requirements.

Sulzer RT-flex Engine Orders Sulzer RT-flex engines are certainly attracting increasing interest from shipowners. In mid April 2003, there is a total of 19 RT-flex engines in service and on order, amounting to 575,670 kW. There is a significant number of further orders ‘in the pipeline’. The current engines are listed in Table III.

In service 2001 (2003) (2003/04) (2003) (2004) (2004) (2004/2005) (2005)

Conclusion Sulzer RT-flex common-rail technology is the successful implementation of a quantum step forwards in engine development. It has even more significance than the change from air-blast injection to airless injection some 70 years ago. Common-rail injection is clearly the future direction for large diesel engines. The Sulzer RT-flex engine in the “Gypsum Centennial” was built from the outset as a fully-industrialised product, fully capable of continuous heavy-duty commercial operation. It has achieved this performance with very good success. No difficulties arose from the concept; all the problems experienced must be regarded as ‘teething problems’. All shortcomings are now resolved. The Sulzer RT-flex60C is a forward-looking engine offering a new range of benefits to shipowners. Not only does it bring the new benefits of electronically-controlled common-rail fuel injection, but embodies stepwise improvements in basic diesel engine technology which will give shipowners benefits in better reliability and longer times between overhauls. The logical extension of the Sulzer RT-flex engine programme is also progressing, thereby bringing the benefits of common-rail injection to all types and sizes of ships.

Bibliography 1. Stefan Fankhauser and Klaus Heim, ‘The Sulzer RTflex: Launching the Era of Common Rail on Low Speed Engines’, CIMAC 2001, Hamburg. 2. Stefan Fankhauser, ‘World’s first common-rail lowspeed engine goes to sea’, Wärtsilä, Marine News, No.32001, pp12–15. 3. Kaspar Aeberli and John McMillan, ‘Common Rail At Sea: The Sulzer RT-flex Engine’, The Motor Ship Marine Propulsion Conference, Copenhagen, 2002. 4. Matthias Amoser, ‘Insights into piston-running behaviour’, Wärtsilä, Marine News, No.2-2001, pp23– 27. 5. Rudolf Demmerle, ‘The first Sulzer RT-flex60C’, Wärtsilä, Marine News 2-2002, pp4–9. 6. Huber, Konrad and Beat Güttinger, ‘First year of service successful for first Sulzer RT-flex’, Wärtsilä, Marine News, No.1-2003, pp4–8.

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