Auxiliary Propulsion SystemFor Two-stroke Engine Plants

Add Propulsion Redundancy, Operational Safety and Minimize Risk - in a Very Simple Way

2

Extra margins of safety are dictated bythe transportation and handling ofvolatile and flammable liquids andgases, corrosive chemicals, and similarhazardous cargoes which may harmthe personnel and the environment.

Therefore Safety First…Safety precautions on board ships haveconstantly been improved throughoutshipping history. Accidents at sea giverise to such improvements in order tosecure the best possible safety for thecrew, the ship, other vessels andinstallations at sea, the environmentand the business as a whole.

Governments, authorities, classificationsocieties, shipowners and insurancecompanies are challenging the manu-facturers of ships and ships’ equip-ment to encourage them to improvetheir products in relation to reliabilityand safety. More than ever before,safe transportation of oil products,toxic chemicals and liquefied gases isa must. This kind of transportation isan important and growing business,characterized by high stakes, huge

capital costs, high-value cargoes andrisk management. On the other hand,environmental fractions, politicians,the press and the public opinion exertan increasing pressure for environ-mental consciousness and safety.

Propulsion RedundancyIn recent years focus has been set onredundancy of propulsion machineryas well as on requirements for arran-gements necessary to restoring andmaintaining availability of the ships’propulsion power and manoeuvringcapability.

In order to meet this demand, MANB&W have developed a new AuxiliaryPropulsion System consisting of:

• Two-stroke propulsion engine• CP Propeller & Control System• Tunnel gear with two steps • El-motor/alternator

- and the Alpha Clutcher

The principle of an auxiliary propulsion system

Safety of Highest Priority

Photo: Øyvind Hagen, Statoil

3

Proven ElementsThe low-speed two-stroke engine it-self is unique in its simplicity and effici-ency always securing safe operation.

The long lasting know-how and practi-cal experience from a vast number ofdifferent ship types and propulsionapplications form the basis for thevery high mechanical quality of our CPpropellers.

The supply of a large number of com-plete propulsion packages includingtunnel gear and shaft alternator hasaccumulated good long-term serviceexperience.The design of the Alpha Clutcher isbased on a disconnecting device de-veloped under the name “Separex”by Burmeister & Wain in Copenhagenin 1973.

With the Alpha Clutcher, the mainengine can automatically be clutchedout from the direct-coupled propellershaft, and consequently the propulsi-on power is delivered by the GenSetsto the shaft alternator used as electricmotor, and via the tunnel gear to thepropeller shaft.

Single is SimpleThe MAN B&W Auxiliary PropulsionSystem (MAN B&W AP System) is avery simple and cost effective alterna-tive to, for instance diesel electric pro-pulsion systems and maintains all theadvantages of a low-speed two-strokeengine plant. In relation to twin-screwpropulsion installations, the singlescrew configuration is usually prefer-red due to a 10 - 12% higher propul-sion efficiency and last but not leastdue to the obvious cost reasons.

44

Advantageous Auxiliary Propulsion Power

Increase the Safety for the Crew as Well as for the ShipIn case of a failure causing loss ofmain propulsion power, the MAN B&WAP System secures the course andmanoeuvrability as well as safe navi-gation at reduced speed to the nea-rest harbour. From the bridge panelthe main engine is stopped and theAlpha Clutcher is clutched out en-abling the propeller to be driven by thePTI-motor on the tunnel gear. Propul-sion power is retained and the shiphas regained its steering capability ata service speed of at least sevenknots. Under adverse weather conditi-ons the ship can maintain its positionuntil the weather conditions improveor assistance has arrived.

Reduce the Tug Related Harbour FeesAs a safety precaution, harbour authori-ties often demand stand-by harbourtugs alongside ships when loading/dis-charging critical cargoes. The propulsi-on system must be ready for take-awayoperation and consequently overhaul ofmain engine and its auxiliary systemsand equipment is not allowed. With theauxiliary propulsion system in take-awaymode ready for take-off, the ship fulfilsthe demands of the authorities and caneliminate the costs for stand-by tugswhen immobilizing the main engine.

Reduce the Insurance PremiumIn comparing two ships - one suppliedwith the MAN B&W AP System andone without - the risk-scenario for theship supplied with the system is clear-ly better and thus directly triggering apositive effect when fixing the ship’sinsurance premium.

Alpha Clutcher AlternativeFor ship types where considerableelectrical power is essential duringstays in harbours, the clutch can belocated on the aft side of the tunnelgear to enable clutching out of thepropeller from the engine and use ofthe main engine as power source forthe shaft alternator in PTO-mode sup-plying power for large cargo pumps etc.

Main engine

Clutch-C2-disengaged

Clutch-C1-engaged

Shaft alternator G1motor M1 1800 rpmPTO load max. 1400 kW

Propeller-120 rpm

2 Speed PTO / PTI gear

120 rpm

Alpha Clutcher engaged

Main engine

Clutch-C2-engaged

Shaft alternator G1motor M1 1800 rpmPTI load max. 1400 kW

Propeller-85 rpm

2 Speed PTO / PTI gear

0 rpm

Alpha Clutcher disengaged

Clutch-C1-disengaged

Main engine

Propeller-0 rpm

120 rpm

Clutch-engaged

Shaft alternator G1motor M1 1800 rpmPTO load max. 1400 kW

PTO gearAlpha Clutcher disengaged

• Ordinary Propulsion Mode

• Auxiliary Propulsion Mode

• Harbour Mode

5

Reduce the Maintenance-stress at Short Stays in HarbourPunctuality, short stays in harbour andscheduled maintenance of the mainengine must form a synthesis with theship’s charter. During the stay atquayside, overhaul and maintenancework can be carried out withoutdelaying the scheduled departure.

Increased Propulsion AvailabilityNecessary main engine immobilizationor shut downs for, longer lasting scheduled checks and inspectionscan alternatively be dealt with at seaat reduced speed without off-hirejeopardizing the ship’s trading scheduleor charter.

Sailing in Confined WatersThe MAN B&W AP System makes itpossible for the crew to operate safe-ly at reduced speed in channels, riversand straits and simultaneously nursethe main engine or related auxiliaryequipment.

Boost the Propulsion PowerAs a measure for observing the ship’stransportation schedules, the auxiliarypropulsion system can be suppliedwith the possibility to boost electrical

power to the propeller, in addition tothe main engine power and hence increase the ship’s speed whennecessary.

The Alpha Clutcher is for All Ship TypesBoth safety and economy will benefitfrom this concept and it makes theMAN B&W AP System an obviouschoice for many ship types equippedwith low-speed two-stroke main engi-nes and CP Propellers.

Time for inspectionsand overhauls

App. 2708

4327W=2538

620

770

1645

2977 3740 917

6117S=24959921030

D=

4900

1380

1 2 3 4 5 6 7 80 32313029282726252423222120191817161514131211109

Compact installation for a 13 500 tdw tanker with a 6S42MC main engine

Maintainability

6

Class Notation for Propulsion Redundancy

Another Stamp of QualityIt is expected that an increasing num-ber of shipowners in future will speci-fy their new vessels on the basis ofhigh quality and ‘green images’ likecrew safety and environmental safety- rather than exclusively on short-termeconomic efficiency. With MAN B&W’sAP System including:

• Two-stroke propulsion engine• CP Propeller & Control System• Tunnel gear with two steps • El-motor/alternator • Alpha Clutcher

- ship designers, yards, owners andoperators can obtain a specific classnotation for redundant propulsion andmanoeuvring capability.

The following table is a brief overviewof the present class rules for redundan-cy, some of them are provisional only:

The Clutcher ready for full load testing

Service Speed in Auxiliary Propulsion ModeCalculations and practical experienceshow - as an input to evaluation of theengine power needed, that an electri-cal shaft alternator/motor correspond-ing to 20% of the main engine outputis recommended in connection withtwo-step gearing in the tunnel gear.

Favourable InvestmentCompeting clutch systems are avail-able in the market, at almost twice theprice of the Alpha Clutcher concept.These systems are also more complexand more expensive to install.

ABS GL DNV LRS RINA

Restoredpropulsionpower

N/A N/A 50% 50% N/A

Time torestore thepropulsionpower

max 2 min N/A N/A N/A N/A

Speed withrestoredpropulsionpower

7 knots/ 1/2of design

speed (whichever

is less)

7 knots/ 1/2of design

speed(whichever

is less)

6 knots 7 knots 6 knots/ 7 knots

(TakeHome/AlternativePropulsion)

Time /distance

36 hours 72 hours 72 hours N/A 1000 miles/2000 miles

Weatherconditions

Wind:17 m/s(33 knots)

Waves: 4.5 m (15 ft)

Wind andwaves: BF 8

(Beaufortscale)

Wind andwaves: BF 8

(Beaufortscale)

N/A N/A

Obtainablenotations

R1 R1+R1-S R1-S+

RP1 x% – – THSAPS(p/v/m)

Propulsion Redundancy Class Requirements and Notations

Normal speed Vs design in knots

Auxiliary speedPTI power

= 20% of ME

12131415161718

7.07.68.28.89.49.9

10.5

Knots

7

Alpha Clutcher Characteristics

DescriptionThe MAN B&W AP System is basedon the “Power Take-In” principle in-cluding the Alpha Clutcher, for clutch-ing out the main engine from the pro-peller shaft in PTI-mode.

The prototype of the Alpha Clutcherwas produced in the spring of ‘99. Theclutch function is controlled byhydraulic oil added through an oildistributor ring similar to that of theCP Propellers.

No Foundation RequiredThe propeller shaft is connected to anintermediate shaft passing throughthe tunnel gear. The Alpha Clutcher isinstalled on this intermediate shaft.

A short intermediate shaft is installedbetween the Clutcher and the mainengine. The tunnel gear is connectedto the Clutcher via a flexible coupling.A single bearing supports the shaftlineand the tunnel gear has a normalfoundation seating in the ship.

The Alpha Clutcher has internal bea-rings and does therefore not need anexpensive thrust transmitting founda-tion.

Conical BoltsThe cone bolt connection instead ofgearwheels is chosen in order to avoidclearance problems and hence ham-mering in-between the load transmit-ting surfaces. It may be critical to use gearwheels in the shaftline of a two-stroke engine because of torsionalvibrations.

The principle consists of two radiallysplit shaft flanges with a number ofcone holes, a part of each in the outerflange and a part of each in the innerflange. When the cones are pressedinto the holes, the flanges are lockedtogether. When the cones are out ofthe holes, the flanges are free to rota-te independently of each other.

The cone bolt connection and the split flanges

Tugs´ assistance duringberthing and mooring

8

Perfect Fit ConnectionTo align the two flange parts for a per-fect fit between the cone holes and thecones, a ring is pressed against theflanges opposite the cones. This ring iscontrolled by studs and tightened bynuts on these to the backside of thecones. Tension in the studs presses thecones into the cone holes and ensuresalignment of the flanges. This ensuresa perfect fit connection, which preventshammering in-between the connectionsurfaces like an ordinary fitted bolt.

When the nuts are loosened, thecones and the ring are free to moveand the flanges are free to rotatebecause the studs are placed outsidethe split diameter.

In the Alpha Clutcher the stay bolts donot pass inside the cones, but in-between them. The cones and thestuds are moved by servo pistons toenable hydraulic remote control.

Patented Locking PrincipleInstead of tightening a nut on eachstud, a locking ring locks all conebolts at one time. When hydraulic pres-sure is added, the studs are stretchedand the ring is turned into locked posi-tion. The pressure is then releasedand the cone bolts are mechanicallylocked. To unlock the cone bolt con-nection, “clutch-in pressure” has to beadded to be able to turn the lockingring, and after this pressure is addedfor clutching out.

The principle of the locking ring

Auxiliary Propulsion ModeClutching out the Alpha Clutcher isdone remotely from the bridge. Auxili-ary propulsion mode is established inless than two minutes. When clutch-ing in, the Clutcher is remotely con-trolled from a panel in the engineroom.

When operating in auxiliary propulsionmode, the shaft alternator is used aselectric motor. This motor deliverspower via the tunnel gear to the pro-peller shaft. When the Alpha Clutcheris clutched out, the main engine isdisconnected from the propeller shaftand stopped. In this mode, however,the Alpha Clucher will transmit thepropeller thrust to the thrust bearingof the main engine.

To obtain the best possible propulsionefficiency in auxiliary propulsion modeat limited electrical power, it is neces-sary to reduce the rate of speed of thepropeller to match this limited powerwith the power absorption of the pro-peller. Therefore the tunnel gear incor-porates a two-step gearing. One‘step-up’ ratio for the ordinary propul-sion mode with shaft alternator, and alarger ‘step-down’ ratio for the PTIauxiliary propulsion mode.

The Clutcher housing

9

Ordinary Propulsion ModeWhen operating in ordinary propulsionmode, the main engine delivers thepropulsion power directly to the propel-ler shaft via the clutched-in Alpha Clutcher. PTO-power is delivered fromthe shaft via the flexible coupling to thetunnel gearbox and the shaft alternator.

When switching from auxiliary propul-sion mode, ordinary operation modeis re-established in five minutes. Themain engine and the shaft alternatorhave to be stopped, when the AlphaClutcher is activated for clutching in.

When the ship operates in ordinarypropulsion mode, the Alpha Clutcheris mechanically locked. No parts aremoving and the Clutcher is not expo-sed to internal wear of any kind. Nohydraulic systems including back-upsystems are required to maintain theClutcher in position. No additionalpower consumption.

Easy InstallationThe Clutcher is easily installed with atraditional hydraulic shrink-fitted coup-ling to the fore end of the intermediateshaft through the tunnel gear.

The connection to the intermediateshaft at the engine side is made byhydraulically operated fit and tie bolts.

Alignment InstructionsFor easy alignment of the propulsionplant, alignment calculations are madeand instructions are supplied to theshipyard. The alignment instructionsensure the right load distributions onthe stern tube bearings and shaft linebearings. In this connection the Clutc-her is seen as an intermediate shaftintegrated with the CP Propeller systemand is therefore easy to fit and align.

Clutch Oil SystemLubricating oil and hydraulic operatingoil are supplied via the Hydra Pack tankunit for the propeller system. This tankunit is always assembled and factory-tested prior to delivery in order to faci-litate the yard’s installation work.

Operating ManualsAn operating manual will provide theoperating crew with a clear guidanceon the redundancy features of thesystem. The manuals cover all detailsincluding a general description of thecomplete propulsion system, operat-ing instructions and procedures fordealing with the situations identified inthe class required Failure Mode andEffect Analysis, FMEA-report.

Test and TrialsClass approval of the Alpha Clutcherwill be obtained in our workshop priorto delivery. During quay and sea trialsthe functionality of the Alpha Clutcherwill be tested - and the capability ofthe Auxiliary Propulsion System tosecure the right speed and manoeu-vrability will be demonstrated.

Remote ControlSystemThe el-motor/alternator andclutch controlsystem is inte-grated with theCP Propellerand main engi-ne system.

The automatic PTI start-up sequenceincludes, eg interlocks for ‘main engi-ne stopped’, ‘Clutcher in clutched-outposition’, ‘el-motor/alternator clutchedout’, gearing in the tunnel gear ‘chan-ged to the PTI step-down ratio’, ‘pro-peller pitch adjusted to zero-position’.And then follows the transformer-startof the el-motor and the clutching in atthe tunnel gear. In auxiliary propulsionmode the power absorption of the CPPropeller is controlled to stay withinthe load range of the el-motor. All electrical circuits of the control systemare monitored by the alarm system.

Factory test of the Hydra Pack tank unit with pumps, filters, thermostatic valve, cooler, servo valves and instrumentation

10

Alpha Clutcher Range for Two-stroke MC Engines

Four Clutcher series - CB1 to CB4 -have been designed to match auxiliarypropulsion systems for two-strokeengine plants up to and including the60-bore MC series. This engine rangecorresponds to the power range of theMAN B&W CP Propellers, which againcovers a wide range of modern chemi-cal, gas and product tanker designs.

TYPE CB 1 CB 2 CB 3 CB 4Dimensions mmLenght [L] 1445 1635 1830 2160Diameter [D] 1185 1340 1500 1770Weight* [ton] 14 20 29 44ENGINE Cylinder versionsS26MC 4-12L35MC 4-12S35MC 4-10 11-12L42MC 4-7 8-10 10-12S42MC 4-5 6-7 8-12S46MC-C 4 5 6-8L50MC 4 5-6 7-8S50MC 4-5 6-8S50MC-C 4 5-7 8L60MC 4-5 6-8L60MC-C 4 5-8S60MC 4 5-7S60MC-C 4 5-6

* Approx weight incl intermediate shaft

11

Significant Advantages

The Auxiliary Propulsion System withAlpha Clutcher means:

• Cost-efficient propulsion redundancy• Simple, reliable and proven techno-

logy• Safe operation and quick change of

propulsion mode• Full integration with the CP Propel-

ler system• Easy handling and installation at

shipyards• No separate thrust transmitting

foundation required• No static hydraulic or electric power

consumption • Maintenance free• No practical wear• Free of back-lash

For a very wide range of typical pro-duct tankers, gas tankers and chemi-cal tankers the off-hire risk scenarioalone will justify the investment in theAlpha Clutcher system - even withoutadding the value of all the positiveside-effects like, for instance reducedtug related harbour fees and increa-sed main engine maintainability.

The Scientific AngleExtensive studies, recently performedby Prof Dr C M Gallin, Gallin MarineConsultants show a clear capital ad-vantage of a single-screw two-strokepropulsion plant with the Alpha Clutc-her Auxiliary Propulsion System - com-pared to a similar two-stroke propulsi-on system without propulsion redun-dancy on the one hand, and a corre-sponding twin-screw twin-engine two-stroke propulsion system on the other.This scientific study was based on allcosts in the fields of Safety, Environ-ment and Business related to thecumulative risk for the service life of aproduct tanker with the above threepropulsion plant options.

The cumulative risk is calculated fromstatistical ‘real life’ figures, based onaccidents and consequences due tomain engine failures, selected andevaluated from the casualty bank of

Lloyd’s Register in London. The costsevaluated are for instance: Value ofship and cargo, repair costs, loss ofhire due to repair time, loss of hire dueto waiting time, loss of hire due totowing time and the towing costs.

“The 5th Product” - Excellent Project Service Propulsion know-how, customization,system integration and service is atyour disposal comprising:

• Lay-out of engine, tunnel gear, propeller, piping system etc

• Optimizing of propulsion modes• Selection of the gear ratios for the

tunnel gear• Alignment analysis and instructions• Strength and vibration calculations• Arrangement and installation

drawings• Instruction books• Dimension sketches on disks• Project guides• Investment/pay back time

calculations • Operation and maintenance costs

- and much more due to a strong andflexible toolbox available for such pro-ject services.

The Genuine Propulsion PackageSince 1989, MAN B&W Diesel’s worksin Frederikshavn, Denmark have manu-factured and supplied two-strokeengines of the successful MC-series,today up to the 8S50MC-C engine.

The MAN B&W CP propeller program-me has been developed to efficientlymatch the MC-engine series up to the70MC versions.

The Alpha Clutcher is an integratedpart of those propeller systems whichare designed, manufactured and sup-plied by one company taking fullresponsibility for functionality, orderhandling, commissioning, warrantyand after-sales service of the comple-te propulsion system.

Photo: Øyvind Hagen, Statoil

MAN B&W Diesel A/SAlpha DieselNiels Juels Vej 15DK-9900 Frederikshavn DenmarkTelephone + 45 96 20 41 00Telecopy + 45 96 20 40 30e-mail: alpha@manbw.dkhttp//: www.manbw.dk

653/1.0-GB. Status March ‘01

Copyright©

MAN B&W Diesel A/S, Alpha DieselReproduction permitted

provided source is given.

Reg. no. 39 66 13 14