CP Propeller Equipment - Martin's Marine Engineering Page

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IntroductionThe purpose of this manual is to act asa guide line in the project planning of theMAN B&W propeller equipment.The manual gives a description of thebasic design principles of the MANB&W controllable pitch (CP) propellerequipment. It contains dimensionalsketches, thereby making it possible towork out shaft line and engine room arrangementdrawings. Furthermore, aguide line in some of the basic layoutcriteria is given.Our design department is available withassistance concerning speed and bollardpull prognoses, determining powerrequirements from the propeller, as wellas advice on more specific questionsconcerning installation and modes ofoperation.All our product range is constantlyunder review, being developed and improvedas needs and conditions dictate.We therefore reserve the right to makechanges to the technical specificationand data without prior notice.In connection with the propeller equipmentthe Alphatronic Control Systemcan be used. Special literature concerningthis field can be forwarded onrequest.Propeller designationVB 640VBS 1080Diameter of propeller hubCP propeller with hydraulic servo motorin gearboxDiameter of propeller hubCP propeller with hydraulic servo motorin hubThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net3

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General DescriptionMAN B&W Alpha have manufacturedmore than 6,000 controllable pitch propellersof which the first was producedin 1902.The basic design principle is well–proven, having been operated in alltypes of vessels including ferries,cruise and supply ships etc, many ofwhich comply with high classificationrequirements.Today the MAN B&W Alpha controllablepitch propeller equipment typesVB and VBS are handling engine outputup to 20,000 kW, fig 1.Controllable pitch propellers can utilizefull engine power by adjusting bladepitch irrespective of revolutions orconditions.They offer not only maximum speedwhen free sailing, but also maximumpower when towing, good manoeuvrabilitywith quick response via the remotecontrol system and high asternpower.These are just a few of many advantagesachieved by controllable pitchpropellers.Propeller Diameter [mm]800070006000VBS16805000VBS1560400030002000VBS740VBS860VBS980VBS1080VBS1180VBS1460VBS1280 VBS1380100000 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000Engine Power [kW]Fig 1: VBS propeller equipment programme for no ice class notationThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net5

Propeller equipmentThe standard propeller equipmentcomprises a four–bladed CP propellercomplete with shafting, stern tube,outer and inboard seals, oil distributorand coupling flange.The location of the hydraulic servomotor for controlling the pitch will dependon size and utilization of the propellerequipment.Propeller type VBFor propellers coupled to the MANB&W Alpha gearbox the hydraulicservo motor is located in the gearboxcontrolling propeller pitch via a pitchcontrol rod, fig 2.2 03 38 05–1.00 510 15 20Fig 2: Propeller equipment type VB (12V23/30A, AMG 16, VB 640)2 03 35 91–5.25 05 10 15 20 25Fig 3: Propeller equipment type VBS (8L35MC, VBS 980)6This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Propeller type VBSWhen using propeller hub diameters of740 mm or larger, the hydraulic servomotor can be placed in the hub, figs 3,4 and 5.The system is featuring large servo pistondiameter with low oil pressure andreacting forces, few components andreduction of overall installation length.Oil distributorFor the VBS propeller equipment the oildistributor for the hydraulic servo motorcan either be shaft mounted ormounted at the front end of the gearbox.2 03 35 90–3.15 05 10 15 20 25 30Fig 4: Propeller equipment type VBS (8L40/54, VBS 1280)2 03 38 04–0.1051015 20 25 30 35Fig 5: Propeller equipment type VBS (8S60MC, VBS 1680)This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net7

Mechanical DesignPropeller type VBSIn the propeller equipment type VBSthe hydraulic servo motor for pitch settingis an integral part of the NiAl–bronze propeller hub. The design of thefour–bladed CP propeller is shown in fig6. The propeller hub is bolted to theflanged end of the tailshaft, which isbored to accommodate the servo oiland pitch feed–back rod.The servo piston which is bolted to thepitch control head, forms the hydraulicservo motor together with the propellercap.The high pressure servo oil system atthe aft end of the hub is completely isolatedfrom the pitch regulating mechanismand thus also from the bladeflanges, which means that the bladesealings only are subjected to gravitationoil pressure.By using a large servo piston diameterand balanced blade shapes, the oilpressure and reacting forces are minimizedin the servo oil pressure space.Blade sealing rings are placed betweenblade foot and blade flange, fig 7. Acompressed O–ring presses a PTFE(teflon) slide ring against the blade foot.This design ensures maximum reliabilityand sealing, also under extreme abrasivewear conditions. For servicingand inspection of the internal parts thehub remains attached to the shaftflange during disassembly thereby reducingtime and need for heavy liftingequipment. Optionally an intermediateflange can be inserted, by which underwaterreplacement of propeller bladesis possible.A hydraulic tube, located inside theshafting, is connected to the piston.With hydraulic oil flowing through thetube, oil is given access into the aftersection of the propeller cap, displacingthe servo piston forward, into an aheadpitch position. The displaced hydraulicoil from forward of the piston is returnedvia the annular space between the tubeand shaft bore to the oil tank.Reverting the flow directions will movethe propeller in astern position.Zinc anodeBlade flangeServo pistonHydraulic pipePropeller shaftPropeller capPitch control headMonoblock hub2 04 05 28–3.0Fig 6: Propeller hub type VBS8This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

2 03 25 73–1.0Blade footIntermediate flangeSlide ringO–ringFig 7: Blade sealing ringsOil distributionThe oil distribution to the hydraulicservo motor can be carried out in twodifferent ways. For two–stroke plantsthe oil distributor is located at the shaftline.For four–stroke plants with reductiongearboxes the oil distributor caneither be placed at the front end of thegearbox or in the shaftline.Shaft mounted OD–ringThe shaft mounted unit consists of acoupling flange with OD–ring and pitchfeed–back. Via the oil distribution ring,high pressure oil is connected to oneside of the servo piston and the otherside to the drain.The piston is herebymoved setting the desired propellerpitch. A feed–back ring is connected tothe hydraulic pipe by slots in the couplingflange, fig 8. The feed–back ringactuates a displacement transmitter inthe electrical pitch feed–back boxwhich measures the actual pitch.The inner surface of the oil distributionring is lined with white–metal.The ringitself is split for exchange without withdrawalof the shaft or dismounting of thehydraulic coupling flange.The sealing consists of mechanicalthrow–off rings which ensures that nowear takes place and that sealing ringsof V–lip–ring type or similar are unnecessary.The oil distributor ring is prevented fromrotating by a securing device comprisinga steel ball located in the ring. Acceptableinstallation tolerances are ensuredand movement of the propellershaft remains possible.In the event of failing oil pressure orfault in the remote control system,special studs can be screwed into theoil distribution ring hereby making manualoil flow control possible. A hold circuitwill then maintain the chosen pitch.Gearbox mounted OD–boxFor propulsion plants with reductiongearboxes the propeller equipment canbe supplied with an oil distribution boxmounted at the front–end of the gearbox.The OD–box incorporates an electricpitch feed–back.Electrical pitch feed–backbox2 04 07 48–7.1Propeller shaftHydraulic pipeFig 8: Coupling flange with OD–ring and pitch feed–back ringOil distribution ring(OD–ring)Feed–back ringThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net9

Propeller type VBThe VB propeller equipment is normallyused for minor MAN B&W Alpha four–stroke propulsion plants in which thehydraulic servo motor for controlling thepropeller pitch is located inside theAlpha gearbox.The design of the VB propeller is shownin fig 9.The propeller pitch, for the VB propellerequipment is controlled via a push/pullrod. The push/pull rod is passingthrough a hollow bored shaft from a hydraulicservo motor located inside thegearbox to the pitch control mechanismplaced inside the monobloc hub.The pitch control mechanism is shownin fig 10.The system uses the pin–in–slot mechanism,giving good pitch movementand control. This system ensures thatthe propeller pitch is proportional to thepitch control rod stroke. Pitch ahead isapplied when the pitch control yoke ismoved aft.The NiAl bronze hub is easy accessiblefrom the aft end. On the cap a zincanode is fitted to protect the propelleragainst galvanic corrosion.Use of the largest possible blade flangediameter offers reduced bearing loadsand ample room for securing bolts.More space is also available in order toaccommodate large actuating pin diametersand stroke for the pitch controlmechanism.Fig 9: Propeller type VBFig 10: Pitch control mechanism10This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Servo Oil SystemThe principle design of the servo oil systemsfor VBS (fig 11) and for VB (fig 12)is identical.The VBS system consists of a servo oiltank unit – Hydra Pack, and a couplingflange with electrical pitch feed–backbox and oil distributor ring.For VB propeller equipment with Alphareduction gearbox, the servo oil systemis an integrated part of the gearbox.This means that the servo piston, pitchfeed–back box and oil distributor ringare located inside the gearbox.The electrical pitch feed–back boxmeasures continuously the position ofthe pitch feed–back ring and comparesthis signal to the pitch order signal. Ifdeviation occurs, a proportional valve isactuated.Hereby high pressure oil is fed to one orthe other side of the servo piston, viathe oil distributor ring, until the desiredpropeller pitch has been reached.The pitch setting is normally remotecontrolled, but local emergency controlis possible.2 04 00 22–5.0ServopistonZincanodeSterntube oiltankMonoblockhubOil tankforwardsealLip ringsealsSterntubePropeller shaftFig 11: Propeller equipment type VBS2 04 05 36–6.0Sterntube oiltankOil tankforwardsealHydraulicpipeOil distributionringPitch controlrodHydra PackLALTITAHMPSL PSLMPALPAL PAH PIDraintankPDPitchfeed–backOil distributionringPitchorderMMLip ringsealsZinkanodeMonoblockhubSterntubeServopistonPitchfeed–backGearboxFig 12: Propeller equipment type VBThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net11

Hydra PackThe servo oil unit – Hydra Pack (fig 13),consists of an oil tank with all componentstop mounted, to facilitate installationat yard.Two electrically driven pumps draw oilfrom the oil tank through a suction filterand deliver high pressure oil to the proportionalvalve. One of the 2 pumps isin service during normal operation. Asudden change of manoeuvre will startup the second pump. A servo oil pressureadjusting valve ensures minimumservo oil pressure at any time herebyminimizing the electrical power consumption.Maximum system pressureis set on the safety valve.The return oil is led back to the tankthrough a cooler and a paper filter. Theservo oil unit is equipped with alarmsaccording to the Classification Societyas well as necessary pressure and temperatureindication.If the servo oil unit cannot be locatedwith maximum oil level below the oil distributionring the system must incorporatean extra, small drain tank completewith pump, located at a suitable level,below the oil distributor ring drain lines.AINS/PROP/8210–03Fig 13: Servo oil unit – Hydra PackT12This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Lubricating oil system, VBThe VB propeller and stern tube have acommon lubricating oil system, fig 14.In order to prevent sea water penetrationthe system is kept under staticpressure by the gravity tank placedabove normal load water line in accordancewith the stern tube seal manufacturer’srecommendations.Because of a pumping effect in the propellerhub during pitch changes, oil iscirculated through propeller equipmentand oil tank. Non return valves in huband at pitch control rod secure that theoil flow to the hub passes the stern tubejournal bearings and further along thechromium steel journal to the bladeactuator mechanism.The return oil flows along the pitch controlrod back to the lub oil tank.The propeller hub is fitted with 2 plugsfor draining and venting during docking.The pitch control rod is lubricated withgrease where intermediate shafts arefitted.Lubricating oil system, VBSAs with the VB equipment the sterntube and hub lubrication is a commonsystem. The stern tube is therefore keptunder static oil pressure by a stern tubeoil tank placed above sea level, see fig11.All MAN B&W propeller equipment withseals of the lip ring type operates on luboil type SAE 30 – usually the same typeof lubricating oil as used in the main engineand reduction gear.Minimum level 3 mabove sea levelLAL64Stern tubeoil tankLow pressure pipeDrainVenting pipeOil tank(4 l)Aft sealingTI8.1Forward sealingNon–return valvesTAH63TAH62Circulating oilsystem forforward sterntube sealing2 03 34 01–2.0DrainFig 14: VB lubricating oil systemThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net13

Propeller Shaft and CouplingFlangeThe tail shaft is made of forged steelnormalized and stress relieved, fig 15and table 1.MaterialYield strengthTensilestrengthElongationImpact strengthCharpy V notchBrinell hardnessN/mmN/mm%JoulesHBForged steelCk45Nminimum 285570–690minimum 18minimum 17170–2102 03 24 14–0.0Fig 15: Tail shaftTable 1The tail shaft is hollow–bored, housingeither a pitch control rod or piping forpitch adjustment.InjectorsIn plants with long shaftlines, the distancebetween the journal bearings canbe estimated by means of the followingformula provided the propeller speed isbelow 350 r/min.InstallationdimensionVenting100CL 450 shaft diameter (mm)L = maximum bearing distanceCoupling flangeA two–parted coupling flange isclamped on to the propeller shaft forflange diameters up to 475 mm. Forcouplings with flange diameters above475 mm a special shrink fitted mountingis used, fig 16. High pressure oil of morethan 2,000 bar is injected between themuff and the coupling flange by meansof the injectors. By increasing the pressurein the annular space C, with the hydraulicpump, the muff is graduallypushed up the cone.Longitudinal placing of the couplingflange as well as final push–up of themuff are marked on the shaft and themuff.2 03 32 21–4.0Mark onshaftHydraulic pumpFig 16: Shrink fitted coupling flangeAMeasurement for push–upstamped on the coupling muff14This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Stern tubeThe standard stern tube is designed tobe installed from aft and is bolted to thestern frame boss, fig 17.The forward end of the stern tube issupported by the welding ring. The oilbox and the forward shaft seal arebolted onto the welding ring. This designallows thermal expansion/contractionof the stern tube and decreases thenecessity for close tolerances of thestern tube installation length.Normally the stern tube and the weldingring are supplied with 5 mm machiningallowance for yard finishing.The stern tube and welding ring can besupplied machined and finished, if required.As an option the stern tube can be installedwith epoxy resin.LinersThe stern tube is provided with forwardand aft white–metal liners, fig 18.Sensors for bearing temperature canbe mounted, if required.A thermometer for the forward bearingis standard.SealsAs standard, the stern tube is providedwith forward and after stern tube sealsof the lip ring type having three lip ringsin the after seal and two lip rings in theforward seal, fig 19.2 04 46 49–1.0Stern tubeBossFig 17: Standard stern tube – VBS2 03 24 14–1.0Fig 18: Stern tube white–metal linersCast ironWelding ringLead–basedwhite metalOil box2 03 24 18–2.0Outboard stern tube sealInboard stern tube sealFig 19: Stern tube sealsThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net15

Hydraulic boltsThe propeller equipment can be suppliedwith hydraulic bolts for easy assemblyand disassembly between propeller shaftline, intermediate shafts and main engineflywheel, fig 20.InstallationInstallation of propeller equipment intothe ship hull can be done in many differentways as both yards and ownershave different requirements of how toinstall and how to run the propellerequipment. Other designs of stern tubeand/or shaft sealing may be preferred.MAN B&W Alpha are available with alternativesto meet specific wishes ordesign requirements.2 03 54 91–9.0Fig. 20 Hydraulic bolt16This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Propeller Blade Manufacturingand MaterialsThe international standard organizationhas introduced a series of manufacturingstandards in compliance with whichpropellers have to be manufactured(ISO 484). The accuracy class is normallyselected by the customer and thetable below describes the range ofmanufacturing categories.ClassSIIIIIIManufacturing accuracyVery high accuracyHigh accuracyMedium accuracyWide tolerancesAt MAN B&W Alpha the propellerblades are checked by computerizedfour–axis measuring equipment.If no class is specified, the propellerblades will be manufactured accordingto class I but with surface roughnessaccording to Class S.Blade materialsPropeller blades are made of eitherNiAl–bronze (NiAl) or stainless steel(CrNi). The mechanical properties ofeach material at room temperature are:Material NiAl CrNiYieldstrengthTensilestrengthElongationImpactstrengthCharpy VnotchBrinellHardnessN/mmN/mm%JoulesHBmin 250590–780min 1630min 150min 380600–790min 1921240–300Both materials have high resistanceagainst cavitation erosion. The fatiguecharacteristics in a corrosive environmentare better for NiAl than for CrNi.Propeller blades are, to a large degree,exposed to cyclically varying stresses.Consequently, the fatique materialstrength is of decisive importance.The dimensioning of a propeller bladeaccording to the Classification Societieswill give a 10% higher thickness forthe CrNi compared to NiAl in order toobtain the same fatigue strength.As an example the difference in thicknessand weight for a propeller blade forengine type MAN B&W 6S35MC(4,200 kW at 170 r/min) is stated in table2.CrNi–steel requires thicker blades thanNiAl–bronze, which is unfortunate fromthe propeller theoretical point of view(thicker = less efficiency). Additionally,the CrNi is more difficult to machinethan NiAl.For operation in ice the CrNi materialwill be able to withstand a higher forcebefore bending due to its higher yieldstrength and for prolonged operationsin shallow water the higher hardnessmakes it more resistant to abrasivewear from sand.The final selection of blade and hub materialdepends on the operating conditionof the vessel. In general terms theNiAl material is preferable for ordinarypurposes whereas CrNi could be an attractivealternative for non–ducted propellersoperating in heavy ice ordredgers and vessels operating in shallowwaters.Ice class C 1A*Material NiAl CrNi NiAl CrNiThickness at r/R = 0.35mm132146169187Thickness at r/R = 0.60mm717890100Thickness at r/R = 1.00mm001513Blade weightkg7298779521053Table 2Classificaton society: Det Norske VeritasThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net17

Optimizing Propeller EquipmentPropeller designThe design of a propeller for a vesselcan be categorized in two parts: Optimizing the complete propulsionplant Hydrodynamic design of propellerblades.Optimizing the complete propulsionplantThe design of the propeller, giving regardto the main variables such as diameter,speed, area ratio etc, is determinedby the requirements formaximum efficiency and minimumvibrations and noise levels.The chosen diameter should be aslarge as the hull can accommodate, allowingthe propeller speed to be selectedaccording to optimum efficiency.The optimum propeller speed correspondingto the chosen diameter canbe found in fig 21 for a given referencecondition (ship speed 12 knots andwake fraction 0.25).For ships often sailing in ballast condition,demands of fully immersed propellersmay cause limitations in propellerdiameter. This aspect must beconsidered in each individual case.To reduce emitted pressure impulsesand vibrations from the propeller to thehull, MAN B&W Alpha recommend aminimum tip clearance as shown in fig22.The lower values can be used for shipswith slender aft body and favourable inflowconditions whereas full after bodyships with large variations in wake fieldrequire the upper values to be used.In twin screw ships the blade tip mayprotrude below the base line.The operating data for the vessel is essentialfor optimizing the propeller successfully,therefore it is of great importancethat such information is available.Propeller diameter mm70006000500040003000To ensure that all necessary data areknown by the propeller designer, thedata sheets on page 27 and 28, shouldbe completed.For propellers operating under varyingconditions (service, max or emergencyspeeds, alternator engaged/disengaged)the operating time spent in eachmode should be given.This will provide the propeller designerwith the information necessary to designa propeller capable of deliveringthe highest overall efficiency.75r/min100125150175200250300350400200010002 03 24 10–2.21000 3000 5000 7000 9000 11000 13000 15000Engine power kWFig 21: Optimum propeller diameter18This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

YTo assist a customer in selecting theoptimum propulsion system, MANB&W Alpha are able of performingspeed prognosis (fig 23), fuel oil consumptioncalculations (fig 24) and towingforce calculations (fig 25). Variousadditional alternatives may also be investigated(ie different gearboxes, propellerequipment, nozzles against freerunning propellers, varying draft andtrim of vessel, etc).2 03 34 68–3.0HubDismantlingof capX mmVB 480 75VB 560 100VB 640 115VB 740 115VB 860 135VB 980 120VBS 740 225VBS 860 265VBS 980 300VBS 1080 330VBS 1180 365VBS 1280 395DZHigh skewpropellerYVBS 1380 420VBS 1460 450VBS 1560 480VBS 1680 515Fig 22: Recommended tip clearanceXNon–skewpropellerYBaselineBaselineclearanceZ mm15–20% of D 20–25% of D Minimum 50–100Power (kW)800060004000200008 10 12 14 16Speed (knots)Fig 23: Speed prognosisConsumption (kg/hour)1600120080040008 10 12 14 16Speed (knots)Fig 24: Fuel oil consumptionTow force (kN)6005605204804404000 1 2 3 4 5 6Speed (knots)Fig 25: Tow forceThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net19

Hydrodynamic design of propellerbladesThe propeller blades are computer designed,based on advanced hydrodynamictheories, practical experienceand model tests at various hydrodynamicinstitutes.The blades are designed specially foreach hull and according to the operatingconditions of the vessel.High propulsion efficiency, suppressednoise levels and vibration behaviour arethe prime design objectives.Propeller efficiency is mainly determinedby diameter and the correspondingoptimum speed. To a lesser, butstill important degree, the blade area,the pitch and thickness distribution alsohave an affect on the overall efficiency.Blade area is selected according to requirementsfor minimum cavitation,noise and vibration levels.To reduce the extent of cavitation on theblades even further, the pitch distributionis often reduced at the hub and tip,fig 26.Care must be taken not to make excessivepitch reduction which will effectthe efficiency.Thickness distribution is chosen accordingto the requirements of theClassification Societies for unskewedpropellers.Pitch/diameter ratio1,401,201,000,800,600,40 0,60 0,80 1,00Dimensionless ratio of radii r/RFig 26: Pitch distribution along radiusCavitationCavitation is associated with generationof bubbles caused by a decreasein the local pressure below the prevailingsaturation pressure. The low pressurecan be located at different positionson the blade as well as in thetrailing wake.When water passes the surface of thepropeller it will experience areas wherethe pressure is below the saturationpressure eventually leading to generationof air bubbles. Further downstream the bubbles will enter a higherpressure region where the bubbles willcollapse and cause noise and vibrationsto occur, in particular if the collapseof bubbles takes place on the hullsurface.Three main types of cavitation exist –their nature and position on the bladescan be characterized as: Sheet cavitation on suction side(Fig 27)The sheet cavitation is generated at theleading edge due to a low pressurepeak in this region. If the extent of cavitationis limited and the clearance tothe hull is sufficient, no severe noise/vibration will occur. In case the cavitationextends to more than half of thechord length, it might develop into cloudcavitation. Cloud cavitation often leadsto cavitation erosion of the blade andshould therefore be avoided. Sheet cavitationin the tip region can develop intoa tip vortex which will travel downstream. If the tip vortex extends to therudder, it may cause erosion.2 03 93 91–1.0Fig 27: Suction side (sheet cavitation)V Bubble cavitation(Fig 28)In case the propeller is overloaded – iethe blade area is too small compared tothe thrust required – the mid chord areawill be covered by cavitation. This typeof cavitation is generally followed bycloud cavitation which may lead to erosion.Due to this it must be avoided inthe design.2 03 93 91–1.0Fig 28: Suction side (bubble cavitation) Sheet cavitation on pressure side(Fig 29)This type of cavitation is of the sametype as the suction side sheet cavitationbut the generated bubbles have a tendencyto collapse on the blade surfacebefore leaving the trailing edge. Thedanger of erosion is eminent and theblade should therefore be designedwithout any pressure side cavitation.By using advanced computer programmesthe propeller designs suppliedby MAN B&W Alpha will bechecked for the above cavitation typesand designed to minimize the extent ofcavitation as well as avoiding harmfulcavitation erosion.2 03 93 91–1.0Fig 29: Pressure side (sheet cavitation)VV20This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

For each condition and all angular positionsbehind the actual hull, the flowaround the blade is calculated. The extentof cavitation is evaluated with respectto noise and vibration, fig 30.Angle of attack (degrees)4Suction2ActualHigh skewTo suppress cavitation–induced pressureimpulses even further, a high skewdesign can be supplied, fig 31. By skewingthe blade it is possible to reduce thevibration level to less than 30% of anunskewed design. Because skew doesnot affect the propeller efficiency, it is almoststandard design on vessels wherelow vibration levels are required.Today, the skew distribution is of the“balanced” type, which means that theblade chords at the inner radii areskewed (moved) forward, while at theouter radii the cords are skewed aft. Bydesigning blades with this kind of skewdistribution, it is possible to control thespindle torque and thereby minimizethe force on the actuating mechanisminside the propeller hub, fig 32.0–2–4Pressure0.4 0.6 0.8 1.0Dimensionless ratio of radii r/RSpindle torque (kNm)420–2–40 90 180 270 360Angle (degrees)0.40 0.60 0.801.00r/R2 03 24 21–0.1Fig 31: High skew designSkew angleCentre lineshaft2 03 24 11–4.1Single bladeAll bladesFig 32: Spindle torqueFor high skew designs, the normalsimple beam theory does not apply anda more detailed finite element analysismust be carried out, fig 33.2 04 05 37–8.0Fig 30: Cavitation chart and extensionof sheet cavitation – suction side10 20 30 4050602 04 01 12–4.0ISO stress levels in N/mmFig 33: Finite element calculation ofpropeller bladeThis document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net21

Technical Calculation andServicesArrangement drawingsProvided MAN B&W Alpha have adequateinformation on the ship hull, anarrangement drawing showing a suitablelocation of the propulsion plant inthe ship can be carried out with dueconsideration to a rational lay–out ofpropeller shaft line and bearings.In order to carry out the above arrangementdrawing MAN B&W Alpha needthe following drawings: Ship lines plan Engine room arrangement General arrangementMoreover, to assist the consulting firmor shipyard in accomplishing their ownarrangement drawings, drawings of ourpropeller programme can be transmittedby E–mail or a disk can be forwardedby regular post. The disks arecompatible with various CAD programmes.Should you require furtherinformation, please contact MAN B&WAlpha.Plant information bookAfter the contract documentation hasbeen completed a Plant InformationBook will be forwarded. This book willcomprise all necessary detailed drawings,specifications and installation instructionsfor our scope of supply.CAE programmes are used for makingalignment calculations, epoxy chockcalculations, torsional vibration calculationsetc. In the following a brief descriptionis given of some of our CAEprogrammes and software service.The alignment calculations ensure acceptableload distribution of the sterntube bearings and shaft bearings.Torsional vibrationsA comprehensive analysis of the torsionalvibration characteristics of thecomplete propulsion plant is essentialto avoid damage to the shafting due tofatigue failures.Based on vast experience with torsionalvibration analysis of MAN B&Wtwo and four–stroke propulsion plants,the VBS and VB propeller equipment isdesigned with optimum safety againstpremature failure due to fatigue. Stressraisers in the shafting or servo unit areminimized using finite element techniques.2 04 01 13–6.0mm–0.200.20.40.6Shaftline for S4633When the propeller is delivered with aMAN B&W engine a complete torsionalvibration analysis in accordance withthe Classification Society rules is performed.This includes all modes ofoperation including simulation of enginemisfire.When the total propulsion plant is designedand manufactured by MANB&W, the optimum correlation betweenthe individual items exists. The extensiveknow–how ensures that the optimumsolution is found as regards minimizingstresses in connection withtorsional vibration calculations. Fig 35shows the result of a torsional vibrationcalculation.1 2 3 4 5 6 7 81 23 4 5mAlignment instructionsFor easy alignment of the propellershaft line, alignment calculations aremade and a drawing with instructions isgiven in the Plant Information Book, fig34.BearingNo.12345Bearing reaction(kN)43.1006.979–0.04346.14746.318Vertical displacement(mm)0.00E+000.00E+003.56E–013.60E–013.60E–01Fig 34: Calculated reactions and deflections in bearingsAngular deflection(rad)3.11E–041.83E–042.03E–057.28E–064.81E–0622This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

When propellers are delivered toanother engine make than MAN B&W,a complete set of data necessary forperforming the analysis is forwarded tothe engine builder in question, fig 36.Whirling and axial vibration calculationsBased on our experience the propellerequipment and shafting are designedconsidering a large safety marginagainst propeller induced whirl andaxial vibrations. In case of plants withlong intermediate shafting or sternposts carried by struts, a whirling analysisis made to ensure that the naturalfrequencies of the system are sufficientlyoutside the operating speed regime.Propeller induced axial vibrations aregenerally of no concern but analysis ofshafting systems can be carried out inaccordance with Classification Societyrequirements.2 03 25 97–1.0Torsional stress amplitude (N/mm)150100500Rule limit forcontinuous runningActual stressesRule limit fortransient runningBarred speed range40 50 60 70 80 90 100 110 120 130Engine speed r/minFig 35: Torsional vibration calculationBulk carrier project 6S50MC 8,580 kW/127 r/minPropeller shaft aft end (d= 460 mm/Ck = 0.55)This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net23

600K1K2K32000 3785 1100 1197 950 943465 7544037150110110110570/ 180560/ 180565/ 180555/ 180740/ 560510520510D=61001560AINS, PSKET1175 1155 S–MEASURE= 5980 W–MEASURE=3700 5476Fig 36: Propeller data for torsional vibration analysisPropeller dataInertia in airInertia in water (full pitch)Inertia in water (zero pitch)Number of bladesPropeller diameterDesign pitchExpanded area ratioPropeller weight (hub + blades)kgmkgmkgmmmkg329003930034500461000.7550.4822230Shaft dataShaft sectionMaterialTensile strengthN/mmYield strengthN/mmTorsional stiffnessMNm/radPropeller shaftServo unitIntermediate shaftForged steelForged steelForged steelmin 600min 740min 600min 350min 375min 350K1 99.0K2 1105.0K3 105.624This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Main DimensionsPropeller equipment VBA B C D2 04 01 15–0.0LMSW minimumHubtypeShaftdiametermmAmmBmmCmmDmmLmmMmmW minmmVB 480 180 390 280 440 340 270 508 850VB 560 180 440 280 440 340 293 553 965VB 560 200 440 315 440 340 293 553 900VB 640 180 520 280 440 340 360 585 900VB 640 200 520 305 440 345 360 585 900VB 640 215 520 318 490 385 360 595 975VB 640 245 520 381 560 440 360 600 1200VB 740 215 580 318 490 385 415 651 1150VB 740 245 580 381 560 440 415 655 1200VB 740 275 580 400 590 475 415 655 1200VB 860 245 660 381 560 440 445 745 1200VB 860 275 660 400 590 475 445 745 1350VB 860 300 660 430 590 475 445 745 1350VB 980 300 710 430 590 475 584 800 1350VB 980 325 710 447 700 575 584 820 1600VB 980 350 710 475 700 575 584 820 1600This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net25

Propeller equipment VBSA B C D2 04 01 14–8.1L M S W minimumHubtypeShaftdiametermmOD–shaftmmAmmBmmCmmDmmLmmMmmW minmmWpreferablemmVBS 740 215 200 580 331 425 390 569 655 1760 2248VBS 740 245 225 580 370 445 410 569 655 1760 2248VBS 740 275 250 580 407 485 450 569 655 1970 2650VBS 860 245 225 670 370 445 410 653 742 1760 2248VBS 860 275 250 670 407 485 450 653 742 1970 2650VBS 860 300 280 670 432 515 480 653 742 2000 2615VBS 980 300 280 760 432 515 480 746 787 2000 2615VBS 980 325 310 760 455 565 530 746 807 2040 2655VBS 980 350 330 760 480 590 555 746 807 2170 2880VBS 1080 325 310 840 455 565 530 821 880 2040 2655VBS 1080 375 350 840 540 610 575 821 945 2170 2880VBS 1080 400 375 840 545 630 595 821 945 2265 2975VBS 1180 375 350 915 540 610 575 885 996 2170 2880VBS 1180 400 375 915 545 630 595 885 996 2265 2975VBS 1180 425 400 915 597 675 640 885 1021 2511 3241VBS 1280 375 350 1000 540 610 575 957 1049 2170 2880VBS 1280 425 400 1000 597 675 640 957 1075 2511 3241VBS 1280 480 450 1000 647 755 720 957 1075 2676 3451VBS 1380 425 400 1070 597 675 640 1030 1131 2511 3241VBS 1380 450 425 1070 622 705 670 1030 1131 2651 3426VBS 1380 480 450 1070 647 755 720 1030 1131 2676 3451VBS 1460 450 425 1130 622 705 670 1100 1170 2651 3426VBS 1460 480 450 1130 647 755 720 1100 1170 2676 3451VBS 1460 510 475 1130 700 820 785 1100 1185 2595 3510VBS 1560 480 450 1210 647 755 720 1175 1242 2676 3451VBS 1560 510 475 1210 700 820 785 1175 1257 2595 3510VBS 1560 560 510 1210 770 860 825 1175 1257 2919 3700VBS 1680 510 475 1295 700 820 785 1278 1323 2595 3510VBS 1680 560 510 1295 770 860 825 1278 1333 2919 3700VBS 1680 625 560 1295 815 930 895 1278 1338 2976 377726This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Data Sheet for Propeller and Propulsion PlantIdentification:Type of vessel:SWIFor propeller design purposes please provide us with the following information:1. S:_____________mm W:____________mm I:______________mm (as shown above)2. Stern tube and shafting arrangement layout3. Propeller aperture drawing4. Complete set of reports from model tank (resistance test, self–propulsion test and wakemeasurement). In case model test is not available the next page should be filled in.5. Drawing of lines plan6. Classification Society :Ice class notation:7. Maximum rated power of shaft generator: kW8. Optimisation condition for the propeller :To obtain the highest propeller efficiency please identify the most common service conditionfor the vessel.Ship speed : kn Engine service load : %Service/sea margin : % Shaft gen. service load : kWDraft : m9. Comments:This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net27

Data Sheet for Propeller and Propulsion Plant(in case model test is not available this page should be filled in)Identification:Type of vessel:MAIN DIMENSIONSSymbol Unit Ballast LoadedLength between perpendiculars L PP mLength of load water line L WL mBreadth B mDraft at forward perpendicular T F mDraft at aft perpendicular T A mDisplacement m 3Block coefficient (L PP ) C B –Midship coefficient C M –Waterplane area coefficient C WL –Wetted surface with appendages S m 2Centre of buoyancy forward of L PP /2 LCB mPropeller centre height above baseline H mBulb section area at forward perpendicular A B m 228This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

Instruction ManualAs part of our technical documentation,an instruction manual will be forwarded.The instruction manual is tailor–madefor each individual propeller plant andincludes: Descriptions and technical data Operation and maintenance guide–lines Spare parts platesVBS–propellerTable of Contents05. Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 05–110. Propeller equipment . . . . . . . . . . . . . . . . . . . . . . . page 10–3The manual can be supplied as aprinted copy as well as an electronicbook in English on CD–ROM.The layout of the electronic book correspondsto the paperback book. In theelectronic book it is possible to searchfor specific topics or words, zoom–in ondiagrams and technical drawings, jumpto references and to add personalnotes. Parts of the book or the entirebook can be printed out.The electronic book is compatible withany standard PC Windows environmentwhen using a special viewerwhich is part of the software on the CD–ROM.15. Propeller hub/–shaft . . . . . . . . . . . . . . . . . . . . . . . page 15–2630. Servo installation parts . . . . . . . . . . . . . . . . . . . . . page 30–2735. Intermediate shaft . . . . . . . . . . . . . . . . . . . . . . . . . page 35–2840. Propeller nozzle . . . . . . . . . . . . . . . . . . . . . . . . . . . page 40–2945. Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 45–3350. Servo system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 50–3480. Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . page 80–4382. Remote control equipment . . . . . . . . . . . . . . . . . page 82–4484. Monitoring equipment . . . . . . . . . . . . . . . . . . . . . . page 84–5386. Safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . page 86–65How do I usethis bookContents...InstructionsData SheetsSpare Parts90. Spare parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 90–6629This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net29