cp propeller equipment - martin's marine engineering page

CP Propeller Equipment

1

Contents Page

Introduction 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller designation 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General Description 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller equipment 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mechanical Design 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller type VBS 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller type VB 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Servo Oil System 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydra Pack 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lubricating oil system, VB 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lubricating oil system, VBS 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Propeller Shaft and Coupling Flange 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coupling flange 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stern tube 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Liners 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seals 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydraulic bolts 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Installation 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Propeller Blade Manufacturing and Materials 17. . . . . . . . . . . . . . . . . . . . . . . . Blade materials 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Optimizing Propeller Equipment 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller design 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optimizing the complete propulsion plant 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrodynamic design of propeller blades 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cavitation 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High skew 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Technical Calculation and Services 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrangement drawings 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plant information book 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment instructions 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torsional vibrations 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Whirling and axial vibration calculations 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Main Dimensions 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller equipment VB 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propeller equipment VBS 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data Sheet for Propeller and Propulsion Plant 27. . . . . . . . . . . . . . . . . . . . . . .

Instruction Manual 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

2This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

3

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 ar-rangement drawings. Furthermore, aguide line in some of the basic layoutcriteria is given.

Our design department is available withassistance concerning speed and bol-lard pull 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 im-proved as needs and conditions dic-tate.

We therefore reserve the right to makechanges to the technical specificationand data without prior notice.

In connection with the propeller equip-ment the Alphatronic Control Systemcan be used. Special literature con-cerning this field can be forwarded onrequest.

Propeller designationVB 640

VBS 1080

Diameter of propeller hubCP propeller with hydraulic servo motorin gearbox

Diameter of propeller hubCP propeller with hydraulic servo motorin hub


4 This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net

5

General DescriptionMAN B&W Alpha have manufacturedmore than 6,000 controllable pitch pro-pellers of 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 control-lable pitch 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 manoeuvr-ability with quick response via the re-mote control system and high asternpower.

These are just a few of many advan-tages achieved by controllable pitchpropellers.

0

1000

2000

3000

4000

5000

6000

7000

8000

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Propeller Diameter [mm]

Engine Power [kW]

VBS740VBS860

VBS980VBS1080

VBS1180VBS1280

VBS1380

VBS1460

VBS1560

VBS1680

Fig 1: VBS propeller equipment programme for no ice class notation


6

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 de-pend on size and utilization of the pro-peller equipment.

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

.0

50 10 15 20

Fig 2: Propeller equipment type VB (12V23/30A, AMG 16, VB 640)

2 03

35

91–5

.2

05 5 10 15 20 25

Fig 3: Propeller equipment type VBS (8L35MC, VBS 980)


7

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 pis-ton diameter 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 gear-box.

05 5 10 15 20 25 30

2 03

35

90–3

.1

Fig 4: Propeller equipment type VBS (8L40/54, VBS 1280)

2 03

38

04–0

.1

15 20 25 30 351050

Fig 5: Propeller equipment type VBS (8S60MC, VBS 1680)


8

Mechanical Design

Propeller type VBSIn the propeller equipment type VBSthe hydraulic servo motor for pitch set-ting is 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 iso-

lated from the pitch regulating mechan-ism and thus also from the bladeflanges, which means that the bladesealings only are subjected to gravita-tion oil pressure.

By using a large servo piston diameterand balanced blade shapes, the oilpressure and reacting forces are mini-mized in 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 reliabil-ity and sealing, also under extreme ab-rasive wear conditions. For servicingand inspection of the internal parts thehub remains attached to the shaft

flange during disassembly thereby re-ducing time and need for heavy liftingequipment. Optionally an intermediateflange can be inserted, by which under-water replacement 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.

Blade flange

Hydraulic pipe

Propeller shaft

Monoblock hub

Zinc anode

Servo piston

Propeller cap

2 04

05

28–3

.0

Pitch control head

Fig 6: Propeller hub type VBS


9

Blade footIntermediate flange

Slide ringO–ring

2 03

25

73–1

.0

Fig 7: Blade sealing rings

Oil distributionThe oil distribution to the hydraulicservo motor can be carried out in twodifferent ways. For two–stroke plantsthe oil distributor is located at the shaft-line. For four–stroke plants with reduc-

tion gearboxes 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 coupl-ing flange, 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 with-drawal of the shaft or dismounting of thehydraulic coupling flange.

The sealing consists of mechanicalthrow–off rings which ensures that no

wear takes place and that sealing ringsof V–lip–ring type or similar are unnec-essary.

The oil distributor ring is prevented fromrotating by a securing device compris-ing a steel ball located in the ring. Ac-ceptable installation tolerances are en-sured and 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 man-ual oil flow control possible. A hold cir-cuit will then maintain the chosen pitch.

Gearbox mounted OD–box

For propulsion plants with reductiongearboxes the propeller equipment canbe supplied with an oil distribution boxmounted at the front–end of the gear-box. The OD–box incorporates an elec-tric pitch feed–back.

2 04

07

48–7

.1

Feed–back ringOil distribution ring(OD–ring)

Propeller shaft Hydraulic pipe

Electrical pitch feed–backbox

Fig 8: Coupling flange with OD–ring and pitch feed–back ring


10

Propeller type VB

The 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 passing

through a hollow bored shaft from a hy-draulic servo 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 mech-anism, giving good pitch movementand control. This system ensures thatthe propeller pitch is proportional to thepitch control rod stroke. Pitch ahead is

applied 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 di-ameters and stroke for the pitch controlmechanism.

Fig 9: Propeller type VB Fig 10: Pitch control mechanism


11

Servo Oil SystemThe principle design of the servo oil sys-tems for 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

.0

Oil distributionring

Sterntube

Lip ringseals

Propeller shaft

Hydraulicpipe

Monoblockhub

Zincanode

Servopiston

Sterntube oil

tank

Oil tankforward

seal

Pitchfeed–back

M

PD

M

M M

LAL

TI

TAH

PSL PSL

PAL PAH PI

PAL

Pitchorder

Draintank

Hydra Pack

Fig 11: Propeller equipment type VBS

2 04

05

36–6

.0

Oil distributionring

Pitchfeed–back

Pitch controlrod

Monoblockhub

Sterntube

Zinkanode

Lip ring seals

Servopiston

Sterntube oil

tank

Oil tankforward

seal

Gearbox

Fig 12: Propeller equipment type VB


12

Hydra PackThe servo oil unit – Hydra Pack (fig 13),consists of an oil tank with all compo-nents top mounted, to facilitate installa-tion at yard.

Two electrically driven pumps draw oilfrom the oil tank through a suction filterand deliver high pressure oil to the pro-portional valve. One of the 2 pumps isin service during normal operation. Asudden change of manoeuvre will startup the second pump. A servo oil pres-sure adjusting valve ensures minimumservo oil pressure at any time herebyminimizing the electrical power con-sumption. 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 tem-perature indication.

If the servo oil unit cannot be locatedwith maximum oil level below the oil dis-tribution ring the system must incorpor-ate an extra, small drain tank completewith pump, located at a suitable level,below the oil distributor ring drain lines.

TA

INS

/PR

OP

/821

0–03

Fig 13: Servo oil unit – Hydra Pack


13

Lubricating oil system, VBThe VB propeller and stern tube have acommon lubricating oil system, fig 14.

In order to prevent sea water penetra-tion the system is kept under staticpressure by the gravity tank placedabove normal load water line in accord-ance with the stern tube seal manufac-turer’s recommendations.

Because of a pumping effect in the pro-peller hub during pitch changes, oil iscirculated through propeller equipmentand oil tank. Non return valves in hub

and 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 con-trol rod 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 en-gine and reduction gear.

Stern tubeoil tank

Circulating oilsystem for

forward sterntube sealing

Oil tank(4 l)

Minimum level 3 mabove sea level

Aft sealing Forward sealing

Drain

TI8.1

DrainLow pressure pipe

Venting pipe

Non–return valvesTAH63

TAH62

LAL64

2 03

34

01–2

.0

Fig 14: VB lubricating oil system


14

Propeller Shaft and CouplingFlangeThe tail shaft is made of forged steelnormalized and stress relieved, fig 15and table 1.

Material Forged steelCk45N

Yield strength

Tensilestrength

Elongation

Impact strengthCharpy V notch

Brinell hard-ness

N/mm�

N/mm�

%

Joules

HB

minimum 285

570–690

minimum 18

minimum 17

170–210

Table 1

The tail shaft is hollow–bored, housingeither a pitch control rod or piping forpitch adjustment.

In plants with long shaftlines, the dis-tance between the journal bearings canbe estimated by means of the followingformula provided the propeller speed isbelow 350 r/min.

L � 450 shaft diameter (mm)�L = maximum bearing distance

Coupling 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 pres-sure in the annular space C, with the hy-draulic pump, 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

24

14–0

.0

Fig 15: Tail shaft

100Installationdimension

A

Mark onshaft

C

Measurement for push–upstamped on the coupling muff

Hydraulic pump

Venting

Injectors

2 03

32

21–4

.0

Fig 16: Shrink fitted coupling flange


15

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 de-sign allows thermal expansion/contrac-tion of 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 re-quired.

As an option the stern tube can be in-stalled with 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.

Stern tube

Oil box

Welding ring

2 04

46

49–1

.0 Boss

Fig 17: Standard stern tube – VBS

Lead–based white metal

Cast iron

2 03

24

14–1

.0

Fig 18: Stern tube white–metal liners

Outboard stern tube seal Inboard stern tube seal

2 03

24

18–2

.0

Fig 19: Stern tube seals


16

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 differ-ent ways 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 al-ternatives to meet specific wishes ordesign requirements.

2 03

54

91–9

.0

Fig. 20 Hydraulic bolt


17

Propeller Blade Manufacturingand Materials

The international standard organizationhas introduced a series of manufactur-ing standards in compliance with whichpropellers have to be manufactured(ISO 484). The accuracy class is nor-mally selected by the customer and thetable below describes the range ofmanufacturing categories.

Class Manufacturing accuracy

S

I

II

III

Very high accuracy

High accuracy

Medium accuracy

Wide tolerances

At 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 materials

Propeller blades are made of eitherNiAl–bronze (NiAl) or stainless steel(CrNi). The mechanical properties ofeach material at room temperature are:

Material NiAl CrNi

Yieldstrength

Tensilestrength

Elonga-tion

ImpactstrengthCharpy Vnotch

BrinellHardness

N/mm�

N/mm�

%

Joules

HB

min 250

590–780

min 16

30

min 150

min 380

600–790

min 19

21

240–300

Both materials have high resistanceagainst cavitation erosion. The fatiguecharacteristics in a corrosive environ-ment are 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 Socie-ties will give a 10% higher thickness forthe CrNi compared to NiAl in order toobtain the same fatigue strength.

As an example the difference in thick-ness and weight for a propeller blade forengine type MAN B&W 6S35MC(4,200 kW at 170 r/min) is stated in ta-ble 2.

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 ma-terial depends on the operating condi-tion of the vessel. In general terms theNiAl material is preferable for ordinarypurposes whereas CrNi could be an at-tractive alternative for non–ducted pro-pellers operating in heavy ice ordredgers and vessels operating in shal-low waters.

Ice class C 1A*

Material NiAl CrNi NiAl CrNi

Thickness at r/R = 0.35



Blade weight

mm

mm

mm

kg

132

71

0

729

146

78

0

877

169

90

15

952

187

100

13

1053

Table 2 Classificaton society: Det Norske Veritas


18

Optimizing Propeller Equip-ment

Propeller 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 re-gard to the main variables such as di-ameter, speed, area ratio etc, is deter-mined by the requirements formaximum efficiency and minimumvibrations and noise levels.

The chosen diameter should be aslarge as the hull can accommodate, al-lowing the propeller speed to be se-lected according to optimum efficiency.The optimum propeller speed corre-sponding to 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 condi-tion, demands of fully immersed pro-pellers may cause limitations in pro-peller diameter. 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 in-flow conditions 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 es-sential for optimizing the propeller suc-cessfully, therefore it is of great import-ance that such information is available.

To 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/disen-gaged) the operating time spent in eachmode should be given.

This will provide the propeller designerwith the information necessary to de-sign a propeller capable of deliveringthe highest overall efficiency.

Propeller diameter mm

75

100

125

150

175

200

250

300350400

r/min

1000

2000

3000

4000

5000

6000

7000

1000 3000 5000 7000 9000 11000 13000 15000

Engine power kW

2 03

24

10–2

.2

Fig 21: Optimum propeller diameter


19

To assist a customer in selecting theoptimum propulsion system, MANB&W Alpha are able of performingspeed prognosis (fig 23), fuel oil con-sumption calculations (fig 24) and tow-ing force calculations (fig 25). Variousadditional alternatives may also be in-vestigated (ie different gearboxes, pro-peller equipment, nozzles against freerunning propellers, varying draft andtrim of vessel, etc).

0

2000

4000

6000

8000

8 10 12 14 16

Power (kW)

Speed (knots)

Fig 23: Speed prognosis

0

400

800

1200

1600

8 10 12 14 16

Consumption (kg/hour)

Speed (knots)

Fig 24: Fuel oil consumption

400

440

480

520

560

600

0 1 2 3 4 5 6

Tow force (kN)

Speed (knots)

Fig 25: Tow force

VB 480 75

VB 560

VB 640

VB 740

VB 860

VB 980

VBS 1080

VBS 1180

VBS 1380

VBS 1460

VBS 1560

VBS 1680

Hub of capDismantling

X mmpropeller

High skew

Ypropeller

Non–skew

YclearanceBaseline

Z mm

100

115

115

135

120

330

365

420

450

480

515

VBS 1280 395

15–20% of D 20–25% of D Minimum 50–100

YD

Z

Baseline

X

2 03

34

68–3

.0

225

265

300

VBS 740

VBS 860

VBS 980

Fig 22: Recommended tip clearance


0,60

0,80

1,00

1,20

1,40

0,40 0,60 0,80 1,00

Pitch/diameter ratio

Dimensionless ratio of radii r/R

Fig 26: Pitch distribution along radius

V

2 03

93

91–1

.0

Fig 27: Suction side (sheet cavitation)

V

2 03

93

91–1

.0

Fig 29: Pressure side (sheet cavitation)

20

Hydrodynamic design of propellerbladesThe propeller blades are computer de-signed, based on advanced hydrody-namic theories, practical experienceand model tests at various hydrody-namic institutes.

The blades are designed specially foreach hull and according to the operat-ing conditions of the vessel.

High propulsion efficiency, suppressednoise levels and vibration behaviour arethe prime design objectives.

Propeller efficiency is mainly deter-mined by diameter and the correspon-ding optimum 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 re-quirements for minimum cavitation,noise and vibration levels.

To reduce the extent of cavitation on theblades even further, the pitch distribu-tion is often reduced at the hub and tip,fig 26.

Care must be taken not to make ex-cessive pitch reduction which will effectthe efficiency.

Thickness distribution is chosen ac-cording to the requirements of theClassification Societies for unskewedpropellers.

CavitationCavitation is associated with gener-ation of bubbles caused by a decreasein the local pressure below the prevail-ing saturation pressure. The low pres-sure can be located at different posi-tions on 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 gener-ation of air bubbles. Further downstream the bubbles will enter a higherpressure region where the bubbles willcollapse and cause noise and vibra-tions to occur, in particular if the col-lapse of 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 ca-vitation is limited and the clearance tothe hull is sufficient, no severe noise/vibration will occur. In case the cavita-tion extends 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 ca-vitation in the tip region can develop intoa tip vortex which will travel downstream. If the tip vortex extends to therudder, it may cause erosion.

� 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 ero-sion. Due to this it must be avoided inthe design.

V

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 ten-dency to 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 pro-grammes the propeller designs sup-plied by MAN B&W Alpha will bechecked for the above cavitation typesand designed to minimize the extent ofcavitation as well as avoiding harmfulcavitation erosion.


21

For each condition and all angular posi-tions behind the actual hull, the flowaround the blade is calculated. The ex-tent of cavitation is evaluated with re-spect to noise and vibration, fig 30.

0.40 0.60 0.80

4

2

0

–2

–40.6 0.8 1.0

r/R0.4

Suction

Actual

Pressure

Angle of attack (degrees)

Dimensionless ratio of radii

1.00r/R

2 04

05

37–8

.0

Fig 30: Cavitation chart and extensionof sheet cavitation – suction side

High skewTo suppress cavitation–induced pres-sure impulses even further, a high skewdesign can be supplied, fig 31. By skew-ing the blade it is possible to reduce thevibration level to less than 30% of anunskewed design. Because skew doesnot affect the propeller efficiency, it is al-most standard design on vessels wherelow vibration levels are required.

Skew angle

Centre lineshaft

2 03

24

21–0

.1

Fig 31: High skew design

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.

4

2

0

–2

–40 90 180 270 360

Spindle torque (kNm)

Angle (degrees)

Single bladeAll blades

2 03

24

11–4

.1

Fig 32: Spindle torque

For high skew designs, the normalsimple beam theory does not apply anda more detailed finite element analysismust be carried out, fig 33.

10 20 30 40

50

60

ISO stress levels in N/mm�

2 04

01

12–4

.0

Fig 33: Finite element calculation ofpropeller blade


22

Technical Calculation andServices

Arrangement drawingsProvided MAN B&W Alpha have ad-equate information on the ship hull, anarrangement drawing showing a suit-able location 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 arrange-ment drawing MAN B&W Alpha needthe following drawings:

� Ship lines plan� Engine room arrangement� General arrangement

Moreover, to assist the consulting firmor shipyard in accomplishing their ownarrangement drawings, drawings of ourpropeller programme can be trans-mitted by E–mail or a disk can be for-warded by regular post. The disks arecompatible with various CAD pro-grammes. 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 draw-ings, specifications and installation in-structions for our scope of supply.

CAE programmes are used for makingalignment calculations, epoxy chockcalculations, torsional vibration calcula-tions etc. In the following a brief de-scription is given of some of our CAEprogrammes and software service.

Alignment instructionsFor easy alignment of the propellershaft line, alignment calculations aremade and a drawing with instructions isgiven in the Plant Information Book, fig34.

The alignment calculations ensure ac-ceptable load distribution of the sterntube bearings and shaft bearings.

Torsional vibrationsA comprehensive analysis of the tor-sional vibration characteristics of thecomplete propulsion plant is essentialto avoid damage to the shafting due tofatigue failures.

Based on vast experience with tor-sional vibration 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 tech-niques.

When the propeller is delivered with aMAN B&W engine a complete torsionalvibration analysis in accordance withthe Classification Society rules is per-formed. This includes all modes ofoperation including simulation of en-gine misfire.

When the total propulsion plant is de-signed and manufactured by MANB&W, the optimum correlation betweenthe individual items exists. The exten-sive know–how ensures that the opti-mum solution is found as regards mini-mizing stresses in connection withtorsional vibration calculations. Fig 35shows the result of a torsional vibrationcalculation.

1 2 3 4 5 6 7 8

0.6

0.4

0.2

0

–0.2

mm

m

0.00E+000.00E+003.56E–013.60E–013.60E–01

1 3 4 52

BearingNo.

Shaftline for S4633

43.1006.979

–0.04346.14746.318

12345

3.11E–041.83E–042.03E–057.28E–064.81E–06

Vertical displacement (mm)

Bearing reaction(kN)

Angular deflection(rad)

2 04

01

13–6

.0

Fig 34: Calculated reactions and deflections in bearings


23

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 calcula-tionsBased 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 analy-sis is made to ensure that the naturalfrequencies of the system are suffi-ciently outside the operating speed re-gime.

Propeller induced axial vibrations aregenerally of no concern but analysis ofshafting systems can be carried out inaccordance with Classification Societyrequirements.

150

100

50

0

40 50 60 70 80 90 100 110 120 130

Torsional stress amplitude (N/mm�)

Rule limit fortransient running

Rule limit forcontinuous running

Actual stresses Barred speed range

Engine speed r/min

2 03

25

97–1

.0

Fig 35: Torsional vibration calculationBulk carrier project 6S50MC 8,580 kW/127 r/minPropeller shaft aft end (d= 460 mm/Ck = 0.55)


24

AIN

S, P

SK

ET

1175 1155 S–MEASURE= 5980 W–MEASURE=3700 5476

1560

D=

6100

K3

110

110

110

570/

180

565/

180

555/

180

510

520

510

600

150

2000 3785 1100 9431197 950

K2K1

740/

560

465 754

560/

180

4037

Fig 36: Propeller data for torsional vibration analysis

Propeller data

Inertia in airInertia in water (full pitch)Inertia in water (zero pitch)Number of blades

kgm�

kgm�

kgm�

329003930034500

4Number of bladesPropeller diameterDesign pitchExpanded area ratioPropeller weight (hub + blades)

mm

kg

461000.7550.48

22230

Shaft data

Shaft section Material Tensile strengthN/mm�

Yield strengthN/mm�

Torsional stiffnessMNm/rad

Propeller shaftServo unitIntermediate shaft

Forged steelForged steelForged steel

min 600min 740min 600

min 350min 375min 350

K1 99.0K2 1105.0K3 105.6


25

Main Dimensions

Propeller equipment VB

W minimumSML

A B C D

2 04

01

15–0

.0

Hubtype

Shaftdiameter

mm

Amm

Bmm

Cmm

Dmm

Lmm

Mmm

W min mm

VB 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 1600


26

Propeller equipment VBS

2 04

01

14–8

.1

L M S W minimum

A B C D

Hubtype

Shaftdiameter

mm

OD–shaftmm

Amm

Bmm

Cmm

Dmm

Lmm

Mmm

W min mm

Wpreferable

mm

VBS 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 3777


27

Data Sheet for Propeller and Propulsion PlantIdentification:

Type of vessel:

WS I

For 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 layout

3. Propeller aperture drawing

4. 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 plan

6. Classification Society :

Ice class notation:

7. Maximum rated power of shaft generator: kW

8. Optimisation condition for the propeller :To obtain the highest propeller efficiency please identify the most common service condi-tion for the vessel.

Ship speed : kn Engine service load : %

Service/sea margin : % Shaft gen. service load : kW

Draft : m

9. Comments:


28

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 DIMENSIONS

Symbol Unit Ballast Loaded

Length between perpendiculars LPP m

Length of load water line LWL m

Breadth B m

Draft at forward perpendicular TF m

Draft at aft perpendicular TA m

Displacement � m3

Block coefficient (LPP) CB –

Midship coefficient CM –

Waterplane area coefficient CWL –

Wetted surface with appendages S m2

Centre of buoyancy forward of LPP/2 LCB m

Propeller centre height above baseline H m

Bulb section area at forward perpendicular AB m2


29

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 plates

The manual can be supplied as aprinted copy as well as an electronicbook in English on CD–ROM.

The layout of the electronic book corre-sponds to 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 environ-ment when using a special viewerwhich is part of the software on the CD–ROM.

05. Data page 05–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10. Propeller equipment page 10–3. . . . . . . . . . . . . . . . . . . . . . .

15. Propeller hub/–shaft page 15–26. . . . . . . . . . . . . . . . . . . . . . .

30. Servo installation parts page 30–27. . . . . . . . . . . . . . . . . . . . .

35. Intermediate shaft page 35–28. . . . . . . . . . . . . . . . . . . . . . . . .

40. Propeller nozzle page 40–29. . . . . . . . . . . . . . . . . . . . . . . . . . .

45. Tools page 45–33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

50. Servo system page 50–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

80. Instrumentation page 80–43. . . . . . . . . . . . . . . . . . . . . . . . . . .

82. Remote control equipment page 82–44. . . . . . . . . . . . . . . . .

84. Monitoring equipment page 84–53. . . . . . . . . . . . . . . . . . . . . .

86. Safety equipment page 86–65. . . . . . . . . . . . . . . . . . . . . . . . . .

90. Spare parts page 90–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table of Contents

VBS–propeller

29��

Contents...

Instructions

Data Sheets

Spare PartsHow do I usethis book


cp propeller equipment - martin's marine engineering page

Documents