Licensees Conference 2015, Interlaken 1 / 13

WinGD Low-speed EnginesLicensees Conference 2015

Concepts, Testing and First Service Experience with theGeneration X-Engines

(35 to 92 cm bore)

ABSTRACT

This paper describes, how the concept of theso-called Generation X-engines, namely

· X-tra efficiency· X-tra manufacturing-friendly· X-tra reliability· X-tra environmentally-friendly

has been realised on the different models of thisengine family i.e. the W-X35 and 40, the W-X52,the W-X62 and 72, the W-X82 and the largestengine, the W-X92. Further it is explained whythere are some differences in the realisation ofthe Generation X concept, whether due to theneed for different solutions based on enginesize, due to different requirements from theshipyards or due to the availability of technicalconcepts.

Additionally, a short update is given on the up-graded versions of the W-X35 and 40 and theW-X82 – the so-called B versions – as well as apreview of the newest X-engine model, the W-X52.

Several Generation X-engines are already inservice – these are the W-X35 and 40, the W-X62 and 72 and the W-X82. Field experiencewith these engines is described in the secondpart of this paper.

INTRODUCTION

As the expectations of major players in the mar-ket for large low-speed diesel engines, i.e. theengine builders; the shipyards and the designinstitutes; the ship owners and operators; andthe legislative authorities, have not changed,but they have become particularly tough. Therequirements for highly cost-efficient and envi-ronmentally-friendly solutions for the transporta-tion of goods were never higher than today. It iseasily shown that shipping is environmentallysound when calculating the emissions per unitof cargo transported. Yet when a single vesselcan consume between 50 to 60 tonnes of fuelper day, the resulting level of pollution is high inabsolute terms. Environmental concerns andthe price of fuel have been driving shipping tobecome more cost conscious. The official termfor the latest and most efficient vessels is theso-called “eco-ship”, which claims efficiencygains of up to 30% compared with previous gen-erations of ships. These gains can be achievedby various means, including alternative energysources (renewables, biofuels, LNG), designmeasures (bulbous bow, lightweight construc-tion, design speed reduction), hydrodynamicmeasures like propeller modifications and hullcoatings, and machinery measures such asmain engine design, tuning, rating and hybridshaft generators.

The market has evolved and is more seriouslyconsidering the condition and performance ofships at sea. For example, the largest shippingbanks are much more interested in the qualityand the value of assets today than back in 2010.After the global economic crisis and the intro-duction of stricter banking regulation, financialinstitutions have much less enthusiasm for risk-taking. Banks are looking for ships that can

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maximise asset utilisation, ensuring that ownersand operators remain compliant with their loanconditions. Furthermore, in the case of bank-ruptcy or liquidation, a good quality asset willhave a higher resale value.

Then, another important aspect is the charterervs. owner debate. In times of high spot rates, ascurrently seen in the tanker market, operatorsare looking into accepting spot rates as theycome. In more tumultuous and volatile markets,owners will be opting for the stability of longterm charters, transferring the fuel cost respon-sibility to the charterer. The charterer is there-fore deliberately looking at environmentallysound, more efficient ships. Consequently, theindustry is experiencing the emergence of com-panies rating ships depending on their emis-sions and performance levels.

To summarise, the higher the rating, the moreefficient the ship, which then allows more attrac-tive bank loan terms, a better charter contract(possibly even with a premium) and a higher re-sale value.

As mentioned above, machinery is one key ele-ment in the design of an “eco-ship”. The newGeneration X-engines are the first in WinterthurGas & Diesel Ltd’s (WinGD) two-stroke marinediesel portfolio which are specifically developedwith the aforementioned increased focus on lowoperating costs combined with optimised firstcosts, on actual and forthcoming environmentallegislation and, finally, on compact design forthe highest possible cargo capacity (payload).

To highlight the new generation of engines, anupdated type designation was introduced inMay 2011, namely W-X35 and W-X40, W-X62and W-X72, and W-X92, where “W” stands forWärtsilä and “X” for cross-head engine, extralow speed and flexible fuel injectiontechnology.

THE TECHNICAL REALISATION OF THEX CONCEPT

X-tra environmentally-friendly

A newly developed engine needs to be pre-pared for the coming enactment of the Interna-tional Maritime Organization’s (IMO) limits onemissions of oxides of nitrogen (NOX) emis-sions legislation. The Tier III limits will becomeeffective from 1st January 2016 and, in additionto NOX limitation, limits will be introduced for fuelsulphur content for the first time, in order to limitemissions of oxides of sulphur (SOX).

The strategies and the technologies WinGD isfollowing to meet the upcoming emissions leg-islation are described in detail in two separatepapers.

The Tier III NOX legislation can be fulfilled byusing so-called Dual-Fuel (DF) technology,which produces NOX emissions are well belowthe given limits during operation on gas. Twoother technologies which can be applied to re-duce NOX emissions to the required low levelare Selective Catalytic Reduction (SCR) andExhaust Gas Recirculation (EGR).

Among emissions, carbon dioxide (CO2) is cur-rently receiving great attention. CO2 is the di-rect product of hydrocarbon fuel combustion inthermal engines, is directly proportional to theirfuel consumption and contributes to the green-house effect. CO2 has also become a new focusin the marine industry since IMO introduced theEnergy Efficiency Design Index (EEDI). TheEEDI is a method used to quantify the CO2

emissions of merchant vessels by benchmark-ing them, and transport work, against a limit im-posed by the IMO. Several measures can betaken to reach an EEDI below the limit, such asoptimisation of the cargo capacity and hull effi-ciency of the ship, engine and propulsion effi-ciency or the application of a Power-Take-Off(PTO) generator. The following paragraph de-scribes in which ways an engine developer cancontribute to an optimised EEDI.

X-tra efficiency

The optimisation of engine efficiency – or,equivalently, Brake Specific Fuel Consumption(BSFC) – has always been one of the most im-portant targets of an engine developer. One ofthe biggest steps on low-speed two-strokes was

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the introduction of the electronic control of fuelinjection and exhaust valve actuation. While onmechanical engines it was only possible to opti-mise these aspects at one single operatingpoint, a BSFC optimisation at all loads becamepossible with the introduction of fully flexibleelectronic control. As the IMO NOX legislationweights the emissions for different load steps todefine the total NOX emissions of an engine, itis possible to use the flexibility of electronically-controlled engines to offer different tuning op-tions to optimise the total fuel consumption of avessel depending on its operating profile. Thefour tuning options which are available for theRT-flex and the X-engines are:

· Standard Tuning· Delta Tuning· Delta Bypass Tuning· Low-load Tuning

The Figure 1 shows BSFC depending on the en-gine load for the four tuning options.

Figure 1: Typical BSFC curves to illustrateStandard, Delta, Delta Bypass and Low LoadTuning

Striving for more efficient propulsion systemsleads to lower speed engines and thus to largerpropellers, since reduced engine speed im-proves the propulsion efficiency of the propeller,and higher stroke-to-bore ratios lead to betterinternal efficiency of the engine. In the mid1990s Wärtsilä introduced engine models witha stroke-to-bore ratio of over 4.0, namely thevery successful RT flex48T, RT flex58T and RTflex68. All the X-engines have a stroke-to-boreratio in the range of 4.1 to 4.5 with the exceptionof the W-X92. On such a large engine the strokeis limited due to machining limitations at thecrankshaft manufacturers.

Why WinGD was seeking a compromise be-tween a long stroke and engine height for someof the X-engines is described in the followingChapter.

X-tra manufacturing-friendly

As described above, the goal of highest total ef-ficiency for the vessel propulsion system leadsto engines with higher stroke-to-bore ratios.This automatically leads to engines which areconsiderably higher than predecessor models,with consequences for engine room design aswell as component and engine weights andcost. For the W-X52, W-X62, W-X72 and W-X82 models, a bore diameter has been selectedwhich is 2 cm bigger than for the respectivecompetitor’s engines. As a consequence, therequested cylinder power can be achieved witha stroke which is about 5% shorter, leading to aconsiderably lower engine room height (pistondismantling height) and also to a lower engineweight.

As mentioned above, the stroke of the W-X92has been limited to 3468 mm to give the majorcrankshaft manufacturers the possibility of pro-ducing the crankshaft without major investmentin new machining facilities. For the small W-X35and W-X40, the stroke and bore have been se-lected at the same length as well-establishedcompetitors’ models to limit engine room re-de-sign work at the shipyards and design institutesto a minimum.

During all development work, close and contin-uous attention is paid to optimising designs formanufacturing. Simplified manufacturing pro-cesses lead to both high quality production andcompetitive manufacturing costs. Apart fromshortened assembly time during production,simplified assembly leads to improved service-ability during engine operation. Since cost com-petitiveness can only be achieved by industrial-isation that takes into account local productionstandards and requirements, co-operations withmajor engine builders in Asia were establishedfor the development of X-engine. With thestrong support of its Asian partners, WinGD’s“Manufacturing Engineering” experts continu-ously drive this process throughout the wholedevelopment project, according to the “Winter-thur Gas & Diesel Ltd design-to-cost process”(see Figure 2).

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Figure 2: Winterthur Gas & Diesel Ltd design-to-cost process

Wherever possible, the X-engines follow anidentical design concept. In some cases, e.g. forthe engine control system, identical compo-nents are even being used. Besides the cost re-duction from increased production volumes, thismodular approach leads to optimisation in man-ufacturing and assembly since the accumulatedknowledge from one engine type can be readilytransferred to another type.

X-tra reliability

To ensure indisputable reliability, most of thedesign concepts of the X-engines were derivedfrom the very popular RT-flex50 andRT-flex82C/T engines. As of June 2015, some418 RT-flex50 and 129 RT-flex82C/T engineshave been ordered and around 400 of these en-gines are already in service, accumulating a to-tal of approximately 6 million running hours.

The new time-controlled “flex” fuel injection sys-tem is derived from Wärtsilä’s four-stroke me-dium speed diesel engine designs. Before itsimplementation on large two-stroke engines, itwas tested extensively under typical operatingconditions on dedicated test rigs and on anRT-flex60C engine in vessel operation.

The proven concepts then have to be custom-ised for the respective engine type and size.The use of state-of-the-art simulation tools likethe Finite Element Method (FEM) for stress andtemperature calculation, vibration, hydraulic orbearing calculations, ensures that all relevantparameters and loads stay within proven design

limits, without unnecessary margins whichwould lead to excessively high manufacturingcost.

“Same, same – but different!”

As far as possible, the same technical conceptsor even identical components are being appliedon all the X-engines. However, in several casessome adaptations were necessary to the re-spective engine types. One of the main reasonsfor such adaptations is the huge ranges of pow-ers and dimensions the X-engines cover. AW4X35 has a power output of 4,350 kWwhereas the biggest X-engine, the W12X92produces 73,560 kW. Also, the weight range of74 to 2140 tons for these two extremes in the X-engine family is impressive. It is self-evident,then, that technical concepts might differ oversuch huge ranges, for example due to limita-tions in manufacturing.

Another reason for adapted solutions is differentengine room designs, depending on the vesseltypes in which the X-engines can be installed.In larger vessels, the typical turbocharger loca-tion is laterally on the engine’s long side,whereas in smaller vessels with very compactengine rooms, the most suitable turbochargerlocation is often at the engine’s driving end.Other typical causes for engine size-dependentsolutions are the applicability of simpler con-cepts on smaller engines only – the oil-cooledpiston is such an example – or weight and sizelimitations in workshops – the biggest crank-shafts can only be produced in two parts.

The availability of technical solutions can alsobe a limitation to their application. It is possiblethat a certain technology is not yet developed tothe required level of maturity for the whole en-gine range and therefore “older”, proven tech-nology has to be applied until the end of the val-idation process. Such an example is the fuel in-jection system. The new time-controlled injec-tors were validated up to the W-X72. For thebigger W-X82 and W-X92 engines the technol-ogy is currently still in the validation phase. Thisis why the proven ICU (Injection Control Unit)technology can be found on these two enginetypes. Table 1 gives an overview of the main en-gine components.

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ComponentsW-X35/X40 W-X52/X62/X72 W-X82 W-X92

Run

ning

gear

Crankshaft Single piece; different executions Single or doublepiece; different exe-

cutions

Single or doublepiece; different exe-cutions; dual cylin-

der distance

Crosshead Straight crosshead pin, single piece guide shoe with white metal lining

Main bearings Thin shell, alu. lining Thin shell, white-metal lining

Crosshead bearings Wide shell, white-metal lining; white-metal lining in cover

Piston cooling Knee lever

Piston rod gland box Four oil scraper, two dirt scraper and two gas-tight rings; hardened piston rod

Engi

nest

ruct

ure

&sc

aven

gesy

stem

Bedplate Single wall, doubletie rod, integrated

thrust bearing

Single wall, single tie rod with Ikea nut, integrated thrust bearing(X82 with double wall bedplate)

Column Single wall, inte-grated gear housing

Double wall, separate gear housing

Cylinder jacket Cast cylinder jacket with inspection door to piston underside

Turbo charger location Aft end Lateral side (or aftend)

Lateral side

Water separation Charging unit with underslung design, 3-nose water separator

Fuel

inje

ctio

n,va

lve

driv

e&

auto

mat

ion

Fuel injection Time controlled electronic Injectors Injection Control Unit

Fuel pumps Multi-elementpumps

Single element, cam-shaft driven fuel pumps

Servo oil system 300 bar servo oil pressure, cast VCU 200 bar SO pres-sure, machined

VCU

200 bar SO pres-sure, cast VCU

Drive of supply unit Direct gear drive from crankshaft

Control system UNIC-flex WECS

Com

bust

ion

cham

ber&

pist

onru

nnin

g

Cylinder liner Self-supported slimtype liner

Self-supported liner with bore cooled collar (X52 with slim type liner)

Cylinder cover Forged or cast execution, 6 elastic studs Forged or cast exe-cution, 8 elastic

studs

Forged or cast exe-cution, 10 elastic

studs

Piston Through-flow oilcooling

Jet-shaker oil cooling

Piston rings Three chromium-ceramic plated, pre-profiled piston rings

Exhaust valve Electronically controlled operation, hydraulically actuated, pneumatically closed

Cylinder lubrication Electronically controlled Pulse Lubricating System (PLS)

Table 1: Concept overview of the main engine components on the X-engines

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THE B VERSIONS OF W-X35 & 40 ANDW-X82

W-X82-B

The design of the W-X82 is very much based onthe successful RT-flex82T and the RT-flex82C.Some 130 RT-flex82T&C engines are in opera-tion today, the earliest ones since 2008.

In 2011 the RT-flex82T became a member ofthe Generation X family and it was renamed theW-X82. But not only was the name changed inorder to indicate that the RT-flex82 was alreadya very modern engine. A number of updateswas also implemented. The most significantchange for the market was the considerably big-ger rating field, which required a number ofmodifications. In addition, some improvementswere implemented, of which two were the intro-duction of the Pulse Jet cylinder lubricating sys-tem and the FAST (Fuel Actuated SaclessTechnology) fuel injection valves.

Due to requirements from the market for evenlower engine speeds and further de-rating pos-sibilities, WinGD recently decided to upgradethe W-X82 to the B version, with an even largerrating field.

Figure 3: Extended rating field of W-X82-B(dark blue)

The only change which is needed due to thelarger rating field is the introduction of cross-head booster pumps. An increase in oil-feedpressure is needed for the reliable operation ofthe crosshead and crankpin bearings at lowerengine speeds with today’s high maximum firingpressures. Thanks to the higher oil pressure,the oil film thickness is increased and the maxi-mum oil film pressure is reduced, while addition-ally the bearings benefit from improved oil re-freshment (cooling).

The introduction of the B-version is also used toimplement two proven features from other en-gine types. The first is the bypass cooling of thecylinder liner and the second is the latest crankangle sensor technology, known as “Angela”.The bypass cooling system was introduced onthe W-X62 & 72 engines as a measure againstlow temperature corrosion on the cylinder linerrunning surface and the piston rings. The linertemperatures are increased by a combination ofreduced cooling water flow and increased inlettemperature of the liner cooling water, as shownschematically in Figure 4.

Crank angle detection was implemented on allthe RT-flex engines by means of a sensor lo-cated at the free end of the crankshaft. The new“Angela” system fulfils the same function, whichis to give at all times the exact position andspeed of the crankshaft, in order to the controlsystem. Four standard proximity sensors“count” the teeth of the intermediate gear wheeland twice per crankshaft revolution two addi-tional sensors are used to detect the Top DeadCentre (TDC) and Bottom Dead Centre (BDC)positions of cylinder no. 1. The rationale for theintroduction of “Angela” was improved cost effi-ciency. “Angela” was first introduced on the RT-flex48T-D in 2012.

Figure 4: Diagram of the bypass cylinder linercooling system

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W-X35-B & W-X40-B

As with the W-X82, there was also increasingdemand for enlarged rating fields for the smallerW-X35 and W-X40 engines. Shown in Figure 5,the relative increase in the rating field is slightlybigger since this is the first time that it has beenadapted to the latest market trends.

Figure 5: Extended rating field of W-X35-B andW-X40-B (dark blue)

As with the X82-B, crosshead booster pumpsare also needed for the extension of the ratingfield. To have sufficient space for the additionalpiping on the exhaust side of the engine and tokeep stress levels within prescribed limits, theoil supply to the main bearings has been re-de-signed.

In addition, the W-X35-B and W-X40-B will alsobenefit from a number of improvements com-pared to their predecessors. Some of the im-provements are adopted from the W-X62 and72, namely:

· Fuel injection nozzles with FAST technol-ogy, leading to cleaner combustion and re-duced fuel consumption

· Pilot valve in the fuel injection nozzles withincreased clearance

· Optimised fuel drain from the Pressure Con-trol Valve

· Improved design of the Valve Control Unit(VCU) with integrated Parker control valve

· Hardware and base software of the UNICcontrol system identical to W-X62/72

· Integration of the control system power sup-ply into the rail unit, leading to a simplifica-tion for shipyards and reduced cost

· Offering the Integrated Injection Control(ICC) as an option.

The cylinder block, liner and cover will receive are-design as a measure against repeated is-sues with leakages from the combustion cham-ber. With the updated design it will also be pos-sible in future to increase the maximum firingpressures for further reduced BSFC. The ex-haust valve cage will be equipped with opti-mised cooling, as some issues were reportedwith the insulation applied in the current solu-tion. The regulation of the fuel and servo-oilpumps will be optimised to improve stability andthe conditioning tank for the cylinder lubricatingsystem will be omitted. This measure and otherre-design work will lead to simpler and moreservice-friendly pipework and cabling aroundthe engines.

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THE NEW W-X52

The W-X52 is the latest member of the X-enginefamily and is currently under development. Alt-hough it has a slightly increased stroke-to-boreratio of 4.45 compared to 4.29 on the W-X62,the W-X52 is mostly scaled down from the big-ger 62 cm bore engine. Due to its smaller size,there are three changes which are worth men-tioning:

· For bore sizes below 580 mm, typically onlytwo instead of three fuel injection valves arebeing used.

· The already well-established supply unitfrom the RT-flex50 fits perfectly on the W-X52. The only change is the increase inservo oil pressure from 200 to 300 bar.

· While the bigger engines need a bore-cooled collar on the cylinder liner to ensureefficient cooling and the required rigidity,smaller engines can be equipped with a sim-pler, slim type cylinder liner, as show in Fig-ure 6

Figure 6: Slim type cylinder liner, shown usingthe example of RT-flex50

According to the project schedule, the deliveryof the first W-X52 from the engine builder is dueby the end of June 2016. Of the engines cur-rently on order, the first W5X52 will be deliveredfrom the engine builder in September 2016.

PROTOTYPE TESTING AND SERVICEEXPERIENCE

Before the very first engine of a new type is de-livered from the engine builder to the shipyard,it undergoes an extensive testing programme.The first target of this prototype testing is theoptimisation of all the relevant parameters toachieve optimum engine performance. Even intimes when almost everything can be simulated,it is still necessary to carry out fine tuning on thereal engine. The second important reason fortesting is to verify the simulation results. As de-scribed earlier in this paper, WinGD is applyingthe latest simulation technologies, but verifyingthe results on the engine it is still an unavoidablepart of the process and also confirms the cor-rectness of all the boundary conditions. Typicalmeasurements and tests during prototype test-ing are:

· Fuel consumption· Emissions (NOX)· Stress & strain· Temperatures· Pressures· Vibrations· Flows· Starting behaviour and air consumption

In some cases it is possible that on one of thefollowing engines, additional tests have to beperformed, based on the findings from proto-type testing. The Type Approval Test (TAT) withall relevant Classification Societies is typicallydone on the third or fourth engine produced, toensure smooth operation during this importantevent.

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Service experience – W-X82

The first 82 cm bore engines entered serviceoperation in the year 2008 and since then thepopulation has increased to 165 engines (RTAand RT-flex versions). Another 60 engines arecurrently on order. In total, the 82 cm bore en-gines have accumulated about 3 million runninghours with very positive service experience. Inparticular, all the white metal bearings (see Fig-ure 7) have close to a zero failure rate over thewhole engine population, which is a greatachievement when considering past issues, es-pecially on the main bearing.

Figure 7: Crosshead bearing from aRT-flex82C engine after 29’008 running hours

The good bearing performance is a result oflong experience in development and design, as-sisted by very accurate calculation methods.However, shaft alignment calculation methodshave also been further improved since theyhave an extremely strong impact on bearingload and, thus, lifetime. Unfortunately, even to-day it is still difficult, in some cases, to convincesome shipyards to follow our alignment specifi-cation.

The Injection Control Unit (ICU) for theRT-flex82T/C was launched with a new design(see Figure 8) which differs from the RT-flex84T-D and RT-flex96C-B. The injection control valvehad been completely redesigned with a newhousing, which is integrated into the main blockand enables the use of smaller parts and easiermaintenance.

1. Valve seat2. Valve sleeve ICV3. Valve spindle (injection control valve)

Figure 8: Injection Control Unit (ICU) W-X82

Initially, the new design led to some new chal-lenges with stress factors and material selectionin combination with particles in the Heavy FuelOil (HFO). Via minor design and materialchanges at the injection control valve, it waspossible to drastically improve both lifetime andperformance.

Since 2012, service experience has been out-standing, with components showing much lesssensitivity to HFO impurities. Today, mainte-nance on board by the crew is possible, offeringhigher flexibility and lower Operational Expend-itures (OPEX). For details see the relevantTechnical Bulletin.

FAST fuel injectors are standard on all newW-X82 deliveries. Service experience gatheredover the past three years indicates an effectivelifetime of up to 18,000 running hours for com-ponents such as the nozzle tip, which is morethan double that achieved with the previous de-sign. WinGD’s field testing experts observe thatthe fuel injection components show almost nosensitivity to fuel quality. On field testing ves-sels, no cavitation and no wear could be foundafter 12,600 hours in operation.

The core part of the FAST injection valve andthe needle with needle seat showed no wear atall (see Figure 9).

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Figure 9: Needle and needle seat without wearafter 12,600 running hours

On the nozzle tip, neither erosion on the sprayholes nor hot corrosion could be seen (see Fig-ure 10).

Figure 10: FAST nozzle tip of RT-flex82T after12,600 running hours

Service experience with piston running is thesource of high levels of satisfaction among en-gine owners and operators since the introduc-tion of the Pulse Jet lubricating system; gas-tight top piston rings and lower piston rings witha chromium ceramic layer; increased liner walltemperature; plus zig-zag and umbrella lubricat-ing oil distribution grooves. Those ship ownerswho strictly follow the fuel sulphur-dependentcylinder lubrication feed-rate and use the re-spective Base Number of the cylinder oil, as rec-ommended in our Technical Bulletins RT-138and 161, will benefit from the best piston run-ning performance. On W-X82 engines a specificcylinder liner wear as low as 0.04 mm/1000 isreadily achievable, as proven on several en-gines.

Today the W-X82 engine – and its RT-flex82Tpredecessor – is a reliable workhorse with verygood service experience, fulfilling the time-be-tween-overhaul (TBO) expectations of the shipowners and offering low OPEX.

Service experience W-X35/40

At the end of 2012 the first W-X35 engine wentinto commercial operation. Today, ten W-X35and two W-X40 engines are in operation andhave accumulated more than 125,000 runninghours (as of June 2015). The engines deliveredhave different cylinder numbers, Fixed Pitchand Controllable Pitch Propellers (FPP andCPP), and operate with and without shaft gen-erators.

What has been highlighted even by the most de-manding owners is the very good fuel consump-tion at all loads in comparison to competitors’engines of similar size.

The W-X35 and the W-X40 were the first Wärt-silä two-stroke engines with the new time-con-trolled fuel injection valves from L’Orange andwith the new UNIC engine control system.

Generally there has been very good feedbackregarding the effective lifetime and performanceof the L’Orange injectors. The initial estimate of8000 hours TBO has been confirmed and mightbe even increased further if current test runningshow no deterioration in the injector controlcomponents.

The UNIC control system, which was derivedfrom Wärtsilä four-stroke engines, revealed anumber of issues, which after several visitsaboard ships are now mostly resolved.

Repeated issues are reported with leakages be-tween cylinder liners and covers at higher loads.WinGD is working on permanent solutions forengines already on vessels. This point is alsobeing addressed in the redesign of the B-ver-sion of the W-X35/40, see chapter “W-X35-B &W-X40-B”.

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Service experience W-X62/72

In mid 2014 the first W6X72 entered commer-cial operation and early in 2015 the first W6X62engine. Today, eleven W-X72 and four W-X62engines are in operation. The W-X72 populationin service is set to grow to about 40 enginessoon and the W-X62 to 20 engines. So far mostof the sea trials and maiden voyages were at-tended by Wärtsilä service engineers.

General feedback

· Good piston running behaviour (see Figure11)

· Reliable cylinder lubrication· Good operation of fuel injection and servo

systems· Spotless condition of gear wheels· Superb engine performance

Figure 11: Good piston running behaviourW6X72

However some challenges on the new enginesrequired the closest attention and immediateaction. On a few engines the new time-con-trolled L’Orange fuel injection valves, basicallyalready familiar from W-X35/40, stopped work-ing after changing over from Heavy Fuel Oil(HFO) to Marine Diesel Oil (MDO) due to stick-ing pilot valves. The issues were resolved viathe implementation of increased clearances inthe pilot valve and by reducing injector cooling.

The UNIC engine control system required opti-misations for engine start-up and crash ma-noeuvres. This was achieved by parameterchanges in the software. Finding the solutiontook some time and several onboard visits byour experts were required. Another recurring

defect was a pressure transmitter failure at theflex-lube cylinder lubricating pumps. To solvethis issue, the sensor membrane was reinforcedand the installation optimised.

A few further piston running failures occurred atthe free end cylinder number 6, which with nor-mal vessel trim stand the highest. All indicationsshow that air was entrapped in the cylinder lu-bricating system and countermeasures involv-ing improved venting are under preparation.

Cracked VCUs were found on one engine. Theroot cause for the crack was found to be insuffi-cient induction hardening of the cast housing.

The W-X62 and 72 are the first engines with thecombination of a double-walled column and sin-gle-wall bedplate. Both are manufacturing-friendly, allow a high quality of welding and re-quire no heat post-treatment. Assembly experi-ence with the new design of tie-rod with arounded nut is positive (see Figure 12).

Figure 12: Single wall bedplate with holes forthe tie rod’s rounded nut

The long term advantage will be that the lowertie rod thread is located in the crankcase andnot exposed to corrosion due to condensation.

The first engines in service have accumulated6000 running hours. Only minor issues arepending and the ship owners have a good opin-ion of the high performance of these new mem-bers of our two-stroke engine family.

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Service experience W-X92

As illustrated in Figure 13, in February andMarch 2015 the first W8X92 engines were shoptested at Hyundai Heavy Industries (HHI). Twofurther engines were tested at HHI in the sum-mer of 2015.

Figure 13: First 8X92 engine during shop-testat Hyundai Heavy Industries (HHI)

On the first engine extensive prototype testingtook place, carried out by WinGD experts.

All stress, temperature and vibration valueswere found to be within permissible limits. TheBSFC figures were confirmed to be within thepublished values. The component inspectiontaking place after the tests on all enginesshowed faultless condition of the inspectedparts. The Type Approval Test (TAT) was suc-cessfully passed on the fourth engine in August2015.

The first vessel with a W8X92 engine is ex-pected to enter commercial service in Novem-ber 2015.

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NOMENCLATURE

BSFC Brake Specific Fuel ConsumptionCAPEX Capital ExpenditureDF Dual FuelEEDI Energy Efficiency Design IndexEGR Exhaust Gas RecirculationFAST Fuel Actuated Sacless TechnologyFEM Finite Element MethodHFO Heavy Fuel OilMDO Marine Diesel OilOPEX Operating ExpenditureSCR Selective Catalytic ReductionVCU Valve Control UnitWinGD Winterthur Gas & Diesel

BIBLIOGRAPHY

‘THE NEW X GENERATION LOW-SPEED EN-GINES FROM WÄRTSILÄ’, Marc Spahni, An-dreas Kyrtatos, Ronald de Jong, CIMAC 2013,Shanghai

AUTHORS

Marc SpahniSenior Project ManagerProject ManagementResearch & Developmentmarc.spahni@wingd.com

Beat SchumacherGeneral Manager MediumBoreProduct Managementbeat.schumacher@wingd.com

Alexandros KaramitsosGeneral Manager BusinessdevelopmentSales & Marketingalexandros.karmitsos@wingd.com