Power struggle

People who buy and build ships are still demanding more and more horsepower. IMO is demanding more paperwork to demonstrate that new engines don't pump out too much NOx. And the people who actually operate are demanding a little more reliability

Large, slow speed diesels are still the propulsion unit of choice for most oceangoing commercial ships, accounting, by one reckoning, for more than 70% of installed propulsion power in ships of 2,000 dwt and over delivered last year. With many ship types getting larger and/or faster, the two major two stroke designers seem locked in a battle to produce ever more powerful engines.

The strength of the demand for these really powerful engines is demonstrated by orders for the most powerful diesel currently in service, the Sulzer RTA96C, orders for which earlier this year passed the two million horsepower mark--all for fast post-Panamax containerships of 500 TEU or larger. As at mid-year, RTA96C engines in service and on order comprised:

• Eight 12RTA96C for P&O Nedlloyd
• Two 11RTA96C for NYK Line
• Five 10RTA96C for Conti Rederi
• Two 10RTA96C for Hanjin Shipping
• Five 10RTA96C for P&O Nedlloyd
• Five 10RTA96C for Yangming Marine

Total: 27 engines aggregating 2,151,360 bhp (1,581,882 kW)

The first RTA96C, an 11-cylinder engine, was started on the test bed in March 1997, and entered service in the 5,750 TEU containership NYK Antares in October 1997. The first engines have now exceeded 10,000 hours' operation. The most powerful engines are the 12RTA96C engines each of 89,640 bhp (65,880 kW) which entered service from June 1998 onwards in the four P&O Nedlloyd Southampton class of 6,690 TEU containerships.

Soon, though, the 'most powerful" title will be taken by MAN B&W's K98MC with an output of 7,780 bhp/cyl or 93,360 bhp for the 12-cylinder engine. Production of the first example, a seven-cylinder unit, was started at Korean licensee Hyundai Heavy Industries Co. Ltd. earlier this year.
The first engine, leading a series of ten 7K98MC models, will power a 4,800 TEU Hapag-Lloyd ship. These engines will be followed by five 10K98MC-C models. The engines will be delivered in 1999-2000.

The largest engines ever designed, five 12K98MC-C engines, are scheduled to be manufactured at Hyundai in years 2000 and 2001.

7K98MC on the testbed

The 7K98MC engine has now been subjected to a comprehensive test program. Several of the large engine components have been tested, and the results included in the evaluations of the overall engine performance. The prototype test was successfully completed according to schedule, and, says MAN B&W, the results fulfilled all design targets for performance, heat load and stresses as well as exhaust gas emissions.

GAS TURBINE CHALLENGE
The need for ever more powerful two strokes is in response to the trend to larger, faster containerships. As we noted here, Rolls-Royce plc has reached agreement on what will be its largest single order for marine engines, worth around $1 billion. FastShip Inc., Philadelphia, is to contract for 25 marine Trent gas turbines. Each of FastShip's initial four high speed containerships will be powered by four of the engines, the agreement also including five spare engines and a 20-year support package.
The marinized derivative of the successful Trent aero-engine is the most powerful gas turbine propulsion unit available to ship operators. Rated at 50 megawatts it will power the 860 ft FastShip vessels at speeds of up to 40 knots.

AIR QUALITY ISSUES
In the cruise ship market, the gas turbine is being touted as producing less air pollution than the diesel. A new Annex VI of the MARPOL 73/78 convention on air pollution from ships sets limits on, among other things, NOx and SOx (nitrogen oxide and sulfur oxide) emissions from ships' diesels. As it happens, the number of countries thus far ratifying the agreement is way below the number required to bring it into force by the target date of next year. However, the IMO diplomatic conference that adopted the annex, agreed to review the standard requirements for entry into force and the contents of the annex, should it not have entered force by December 31, 2002. What's more, as Colin Brookman of ABS told delegates at Marine Log's Maritime Legislation conference last month, "there are two regulations which will be retrospectively applied in many areas of the world" when the air pollution annex actually does come into effect. These cover NOx emissions from new or substantially modified diesels and from new shipboard incinerators. Both regulations refer to a compliance date of January 1, 2000, regardless of the date of entry into force of Annex V.

IMO limits on compliance with the NOx emissions requirements is demonstrated by a certification process--yes, more paper!

The first IMO certificate for a large two-stroke diesel engine-issued by Germanischer Lloyd on behalf of the Danish Maritime Authority-was received by MAN B&W for a 12K90MC model with a rating of 74,640 bhp, tested in Ariake, Japan, by licensee Hitachi Zosen Corporation. It will power an A.P. Møller containership building at the Lindø Shipyard in Denmark.

The first IMO exhaust emissions certificate for a Sulzer diesel engine was issued by NKK for a Sulzer 7RTA52U engine that was tested at the Aioi works of licensee Diesel United Ltd., Japan. Developing 10,920 kW (14,840 bhp) at 135 rev/min, the engine will propel a 1,618 TEU Uniglory containership building at Evergreen H.I. in Japan.

MAN B&W says that even though ratification has yet to take place, all engine manufacturers need to prepare their engines to meet the regulation due to the difficulty of certifying the engines later onboard the vessel. More specifically, Regulation 13 of Annex VI will be applied to all marine diesel engines installed on new ships of 400 tons and above, built after January 1, 2000, once Annex VI enters into force. It also applies to engines supplied to fixed and floating drilling rigs and offshore platforms, and to all engines that undergo a major modification or where there is an increase in power of more than 10%.

Requirements for testing, survey and certification to demonstrate compliance are set in the Technical Code on Control of Emissions of Nitrogen Oxides from Marine Diesel Engines (NOx Technical Code) drawn up by IMO's MEPC (Marine Environment Protection Committee).
The NOx emission limit is determined according to the engine crankshaft revolutions.
The NOx Technical Code applies to all diesels with an output of 130 kW or more, except those installed in lifeboats and any equipment intended solely for emergency use.
To minimize the amount of testing required, series-produced engines can be classed as family or group members and certified as such, based on satisfactory NOx emission testing of a representative parent engine.

The components and data of the subsequent engines in the series are verified as conforming to those of the parent engine, as documented in its approved technical file. This file is a record of the NOx-sensitive components, settings, engine data, method of verifying the engine compliance in service and NOx emission and engine test reports. Engines are subject to:

a) A pre-certification survey, normally carried out on the test bed to demonstrate it meets the NOx emission limit requirements. If the engine is found compliant, an Engine International Air Pollution Prevention (EIAPP) certificate is issued.
b) An initial survey is then carried out on board ship after the engine is installed, but before the ship enters service. This is to ensure the engine is still in conformity with the NOx emission requirements and is part of the on board survey for the issue of a ship's initial International Air Pollution Prevention (IAPP) certificate. This survey will also be required where an engine is modified or up-rated by more than 10%.
c) Periodical and intermediate survey. One or more surveys will be required during the life of the IAPP certificate to verify the engine(s) remain in compliance with the NOx emission requirements.
Until ratification of Annex VI, the pre-certification survey is required for new engines supplied to ships covered by Annex VI from January 1, 2000.

The MAN B&W 12K90MC certified at Ariake was the "parent" engine for a group of eight identical engines. Though only the "parent" needed to be tested. all "member" engines of the group, though, must later undergo a survey to verify their compliance with the regulation in order to obtain their own certificates.MAN B&W Diesel says that all new prototype engines will be IMO certified during the prototype testing.

Wärtsilä NSD notes that the technical file includes the testbed results, defines the relevant components and settings, and states the checking procedure that will be used by surveyors inspecting the vessel in future. In this respect, Wärtsilä NSD has established a clearly defined system of identification numbering for the components relevant to NOx emissions. This numbering system also guarantees the worldwide availability of the correct spare components to ensure that customers can maintain compliance of their Sulzer engines.

TOUGHER LIMITS TO COME
As noted, NOx emission requirements under the new MARPOL Annex VI relate to engine revolutions. The lower the engine's revolutions, the more polluting it is permitted to be! This "be kind to two-strokes" approach underscores the fact that the new Annex VI is actually not particularly demanding from an environmental protection viewpoint. It can be taken as a certainty that air pollution requirements will become much more stringent in the years ahead.
Diesel manufacturers have been investigating a whole range of air pollution reduction techniques available to them. According to ABS's Colin Brookman these include:

• Exhaust Gas Recirculation-promising reductions in NOx concentrations of up to 50% for as little as 15% recirculation of exhaust gas into the inlet manifold;
• Fuel/water Emulsion-offering reductions of produced NOx of up to 10% for each 10% of fresh water added to the fuel and emulsified prior to injection (up to a maximum of 50%).
• Direct Water Injection (without emulsification)-giving reductions of produced NOx of 20-50%.
• Humid Air Motor (HAM) Technique-reducing the produced NOx by humidifying the inlet air prior to its entry into the combustion chamber, giving reductions of NOx of 50%-80%.
• Selective Catalytic Reduction-giving reductions of produced NOx of 80%-95% when using injected urea as a catalyst. Unlike the other options, notes Brookman, this system is an after treatment device, is totally independent of the combustion process and is therefore potentially suitable for retrofitting to any existing engine.

SMART ENGINES
MAN B&W and Wärtsilä NSD are not only locked in a battle to produce the most powerful diesels, they are also competing fiercely to bring the "intelligent engine" to market.
As explained in the recently published seventh edition of "Pounder's Marine Diesel Engines," by Doug Woodyard, such highly reliable engines will, among other things, monitor their own condition. They will adjust parameters for optimum performance in all operating conditions-including fuel- and emissions-optimized modes. Engine performance data will be constantly monitored and compared with values defined in a built-in expert system. If deviations are detected, corrective action will be taken automatically. All this requires the ability to change the timing of the fuel injection and exhaust valve systems while the engine is running. Designing cam driven units with these capabilities would require a mechanical complexity that could sacrifice engine reliability. The alternative: an engine without a traditional camshaft.
Wärtsilä-NSD's approach-the RT-flex concept-will be available on its newest engine, the RTA60C.
The RT-flex uses the Sulzer Common Rail system to give a fully electronically controlled engine that has no need of the camshaft and its individual fuel pumps. The new RTA60C has been created to allow it to incorporate the RT-flex concept and Wärtsilä-NSD expects that conventional (with camshaft) and RT-flex versions will be manufactured in parallel.

LATEST SULZER IS AIMED AT MARKET FOR "FASTER" SHIPS
With cylinder dimensions of 600 mm bore by 2,250 mm stroke, the RTA60C has a maximum continuous output of 2,360 kW/cylinder (3,210 bhp/cylinder) at 114 rev/min. It is available with five to eight cylinders covering an overall power range of 8,250-18,880 kW (11,200-25,680 bhp) at 91-114 rev/min. It thus offers the right powers and speeds for a wide range of "faster" ships such as medium-sized container ships.

The RTA60C offers shorter engine length and lighter weight for a given power than other engines in its class, while incorporating all the latest design features for operating reliability and long times between overhauls. As expected for a marine engine today, it is fully compliant with the IMO NOx emission regulation.

Another requirement of the RTA60C design was to make it more economical to manufacture. This involved extensive co-operation with major licensees and subcontractors right through the design and development processes. Owners and shipbuilders also provided valuable input on installation and maintenance .

CONCORDIA OPTS FOR INTELLIGENT ENGINES
While Wärtsilä NSD is well advanced with plans for commercial introduction of the RT-flex, the first commercial application of an intelligent engine will be in Concordia Maritime's revolutionary new 314,500 dwt V-Max shallow draft tankers. MAN B&W has won a breakthrough order to supply each ship with two 7S60MC-E engines.

MAN B&W's 4T50MX research engine has used electronic/hydraulic control of the fuel oil and exhaust valve systems, rather than a mechanical camshaft, since 1993. In 1997, the design was updated to a "near commercial" second generation system.

Currently, the 37,500 dwt Odfjell chemical carrier Bow Cecil is at sea with a 6L60 MC engine fitted with both electrohydraulic controls and a mechanical camshaft. It is possible to switch from the conventional to the IE system in about three hours.

The conventional system was used on sea trials. In the initial operating period, the auxiliary systems on board have been tested. The electronic hardware and relevant software is being installed this fall to prepare for the start of operations as an intelligent engine. A long term test, over some 10,000 operating hours, will be conducted this year and next to confirm the efficiency and reliability of the IE systems and the engine.
The IE technology is an option on MAN B&W's MC engine program, under the designation MC-E.
The diesels ordered for the Concordia ships are 7S60MC-E engines. Built by licensee Hyundai Heavy Industries in Korea, the engines will be on the testbed from October through December 2000.
Hey, we ran out of space. We'll talk about what's happening in the medium speed sector in an upcoming issue.

WHAT ABOUT RELIABILITY?
Martin Hernqvist, Loss Prevention Officer at marine insurer The Swedish Club, believes manufacturers should be doing more to help owners avoid costly engine failures.At this year's 22nd CIMAC Congress in Copenhagen, Hernqvist said: "Apart from damage affecting the engine itself, the consequences of an engine failure may be severe.."

The Swedish Club is building a new Loss Prevention Database that is already sufficiently comprehensive to allow an analysis of main engine failures. Some of the highlights, according to Hernquist:

• Medium-speed engines: "These engines need extra care. They are over-represented in the damage statistics, more or less independent of the make. The causes of damage to crankshaft/connecting rod, journal/bearing, piston/piston rod and turbocharger should be highest on the agenda."
• Low-speed engines: "Similar causes of damage are evident. For low-speed engines, damage to the turbocharger accounts for around one-third of claims."
• New engines: "Do not trust new engines just because they are new. The statistics show that new engines have teething troubles."

Vessels with low-speed engines account for 69.4% of Swedish Club entries and produce 35.6% of main engine damage claims. Vessels with medium-speed engines represent only 24.2% of entries but 58.2% of main engine claims.
Hernqvist notes: "The recurrence of accidents may very well be blamed on insufficient information from, and lack of preventive steps by, the manufacturers. There is certainly scope for manufacturers to increase their efforts in assisting customers in the prevention of accidents."
During 1988-97, The Swedish Club dealt with 636 machinery claims costing a total of $157.8 million (an average of $248,144 per claim). Main engine claims during the period totaled 284 (by far the largest single category). The cost amounted to $80.4 million - accounting for just over half the total cost of all machinery claims. ML

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