CP Propeller Equipment - Martin's Marine Engineering Page

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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
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Page 6 and 7: Propeller equipmentThe standard pro
Page 10 and 11: Propeller type VBThe VB propeller e
Page 12 and 13: Hydra PackThe servo oil unit - Hydr
Page 14 and 15: Propeller Shaft and CouplingFlangeT
Page 16 and 17: Hydraulic boltsThe propeller equipm
Page 18 and 19: Optimizing Propeller EquipmentPrope
Page 20 and 21: Hydrodynamic design of propellerbla
Page 22 and 23: Technical Calculation andServicesAr
Page 24 and 25: 600K1K2K32000 3785 1100 1197 950 94
Page 26 and 27: Propeller equipment VBSA B C D2 04
Page 28 and 29: Data Sheet for Propeller and Propul

CP Propeller Equipment - Martin's Marine Engineering Page

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