DNV rudder, steering gear, anchoring, mooring.pdf

RULES FORCLASSIFICATION OF

DET NORSKE VERITASVeritasveien 1, N-1322 Hvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11

SHIPSNEWBUILDINGS

HULL AND EQUIPMENTMAIN CLASS

PART 3 CHAPTER 3

HULL EQUIPMENT AND APPENDAGESJANUARY 2000

CONTENTS PAGE

Sec. 1 General Requirements ................................................................................................................ 5Sec. 2 Sternframes, Rudders and Steering Gears ................................................................................. 6Sec. 3 Anchoring and Mooring Equipment ........................................................................................ 28Sec. 4 Masts and Rigging.................................................................................................................... 42Sec. 5 Seats for Additional Lifting, Towing or Mooring Equipment ................................................ 45App. A Additional Requirements for non duplicated Rudder Actuators ........................................ 48

CHANGES IN THE RULES

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If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such personfor his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compen-sation shall never exceed USD 2 million.In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of DetNorske Veritas.

GeneralThe present edition of the rules includes additions and amend-ments decided by the board as of December 1999, and super-sedes the January 1996 edition of the same chapter (includinglater amendments).The rule changes come into force 1 July 2000.This chapter is valid until superseded by a revised chapter.Supplements will not be issued except for minor amendmentsand an updated list of corrections presented in Pt.0 Ch.1 Sec.3.Pt.0 Ch.1 is normally revised in January and July each year.Revised chapters will be forwarded to all subscribers to therules. Buyers of reprints are advised to check the updated listof rule chapters printed Pt.0 Ch.1 Sec.1 to ensure that the chap-ter is current.

Main changes Sec.3 Anchoring and Mooring Equipment In A102 an additional sentence has been added indicating that if

certification of materials is needed, voluntarily, then this will bedone in accordance with A204.

In A204 "fibre ropes (W)" has been included in the list of itemsrequiring DNV Product Certificate (NV) for materials, ISO10474: Type 3.1 C. Where the "(W)" indicates that a work's cer-tificate (for materials, ISO 10474 Type 3.1 B) from an approvedmanufacturer will normally be accepted.

Sec.5 Seats for Additional Lifting, Towing or MooringEquipment

In A102 it is now stated that the crane pedestal flanges and boltsare only subject to approval when CRANE, DSV or CraneVessel is requested. The amendment is made to remove anymisunderstanding in regard to the material requirements and ap-proval of pedestal flanges and bolts.

In A301 the material requirement for pedestal top flanges hasbeen removed.

Corrections and ClarificationsIn addition to the above stated rule amendments, some detected errorshave been corrected, and some clarifications have been made in theexisting rule wording.

Rules for Ships, January 2000Pt.3 Ch.3 Contents Page 3

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CONTENTS

SEC. 1 GENERAL REQUIREMENTS .......................... 5A. Classification..........................................................................5A 100 Application........................................................................5

B. Definitions ..............................................................................5B 100 Symbols.............................................................................5

C. Documentation ......................................................................5C 100 General ..............................................................................5

SEC. 2 STERNFRAMES, RUDDERS AND STEERINGGEARS .................................................................. 6

A. General...................................................................................6A 100 Introduction.......................................................................6A 200 Definitions.........................................................................6A 300 Documentation .................................................................7

B. Materials ................................................................................8B 100 Plates and sections ............................................................8B 200 Forgings and castings........................................................8B 300 Bearing materials ..............................................................8B 400 Material certificates...........................................................8B 500 Heat treatment ...................................................................8

C. Arrangement and Details .....................................................8C 100 Sternframes and rudders....................................................8C 200 Steering gears....................................................................9

D. Design Loads and Stress Analysis........................................9D 100 Rudder force and rudder torque, general .........................9D 200 Rudders with stepped contours .......................................10D 300 Stress analysis .................................................................11

E. Sternframes and Rudder Horns ........................................11E 100 General ............................................................................11E 200 Propeller posts.................................................................11E 300 Sole pieces ......................................................................12E 400 Rudder horns...................................................................12

F. Rudders................................................................................14F 100 General arrangement and details.....................................14F 200 Rudder plating.................................................................14F 300 Rudder bending...............................................................14F 400 Web plates.......................................................................15F 500 Single plate rudders.........................................................15F 600 Mounting of rudder .........................................................15

G. Rudder Stocks and Shafts ..................................................15G 100 General ............................................................................15G 200 Rudder stock with couplings...........................................16G 300 Rudder shaft ....................................................................18G 400 Bearings and pintles .......................................................19

H. Propeller Nozzles.................................................................20H 100 General ............................................................................20H 200 Plating .............................................................................20H 300 Nozzle ring stiffness........................................................20H 400 Welding...........................................................................20H 500 Supports ..........................................................................21

I. Propeller Shaft Brackets ....................................................21I 100 General ............................................................................21I 200 Arrangement....................................................................21I 300 Struts ...............................................................................21I 400 Welding...........................................................................21I 500 Material ...........................................................................21I 600 Testing.............................................................................21

J. Steering Gears .....................................................................21J 100 Arrangement and performance........................................21J 200 Power actuating system, general requirements ...............22J 300 Piping systems, relief valve arrangements......................23J 400 Rudder actuator ...............................................................23J 500 Steering gear control and monitoring systems, general

requirements....................................................................25

J 600 Control gear for steering motors .....................................25J 700 Indications and alarms ...................................................25J 800 Power supply and distribution ........................................25J 900 Emergency power supply................................................26J 1000 Operating instructions.....................................................26J 1100 Additional requirements for oil carriers, chemical carriers

and liquefied gas carriers of 10 000 tons gross andupwards ...........................................................................26

K. Testing ................................................................................. 26K 100 Sternframes .....................................................................26K 200 Rudders and rudder stock connections ...........................27K 300 Steering gears..................................................................27K 400 Trials ...............................................................................27

SEC. 3 ANCHORING AND MOORINGEQUIPMENT .................................................... 28

A. General ................................................................................ 28A 100 Introduction.....................................................................28A 200 Documentation................................................................28A 300 Assumptions....................................................................28

B. Structural Arrangement for Anchoring Equipment ...... 28B 100 General ...........................................................................28

C. Equipment Specification.................................................... 29C 100 Equipment number..........................................................29C 200 Equipment tables.............................................................30

D. Anchors ............................................................................... 31D 100 General ............................................................................31D 200 Materials .........................................................................31D 300 Anchor shackle................................................................31D 400 Testing.............................................................................32D 500 Additional requirements for H.H.P. (High Holding

Power) anchors..............................................................32D 600 Identification ...................................................................32

E. Anchor Chain Cables ........................................................ 33E 100 General ............................................................................33E 200 Materials .........................................................................33E 300 Heat treatment and material testing ...............................35E 400 Breaking test ...................................................................35E 500 Proof test .........................................................................35E 600 Tolerances.......................................................................35E 700 Identification ...................................................................36E 800 Repair of defects .............................................................36

F. Windlass and Chain Stoppers .......................................... 38F 100 General design ................................................................38F 200 Materials .........................................................................38F 300 Testing.............................................................................39

G. Towlines and Mooring Lines ............................................ 39G 100 General ............................................................................39G 200 Materials .........................................................................39G 300 Testing of steel wire ropes ..............................................39G 400 Testing of natural fibre ropes..........................................40G 500 Mooring Winches............................................................41

SEC. 4 MASTS AND RIGGING................................... 42

A. General ................................................................................ 42A 100 Introduction.....................................................................42A 200 Assumptions....................................................................42A 300 Definitions.......................................................................42A 400 Documentation................................................................42

B. Materials and Welding ...................................................... 42B 100 Materials .........................................................................42B 200 Welding...........................................................................43

C. Arrangement and Support ................................................ 43C 100 Masts and posts ...............................................................43C 200 Standing rigging..............................................................43

Rules for Ships, January 2000Pt.3 Ch.3 Contents Page 4

DET NORSKE VERITAS

D. Design and Scantlings.........................................................43D 100 General ............................................................................43D 200 Unstayed masts and posts with derricks .........................43D 300 Stayed masts or posts with derricks with a lifting capacity

not exceeding 10 t ...........................................................43D 400 Stayed masts of posts with derricks with a lifting capacity

of 10 t or more, but not exceeding 40 t ...........................43D 500 Stayed masts without derricks.........................................44D 600 Shrouds............................................................................44

SEC. 5 SEATS FOR ADDITIONAL LIFTING,TOWING OR MOORING EQUIPMENT ...... 45

A. Crane Pedestals and Miscellaneous Lifting Posts............45A 100 Introduction ....................................................................45A 200 Documentation ................................................................45A 300 Materials and welding .....................................................45A 400 Arrangement....................................................................45A 500 Design loads ....................................................................45A 600 Allowable stresses...........................................................46

B. Seatings for Winches, Windlasses and other PullingAccessories...........................................................................46

B 100 Introduction. ....................................................................46B 200 Documentation ................................................................46B 300 Design loads ....................................................................47B 400 Calculation of stresses.....................................................47B 500 Allowable stresses. Materials..........................................47

APP. A ADDITIONAL REQUIREMENTS FOR NON DUPLICATED RUDDER ACTUATORS ...... 48

A. Introduction......................................................................... 48A 100 Scope ...............................................................................48

B. Materials ..............................................................................48B 100 Special Requirements......................................................48

C. Design................................................................................... 48C 100 Design pressure ...............................................................48C 200 Analysis...........................................................................48C 300 Dynamic loads for fatigue and fracture mechanics

analysis............................................................................48C 400 Allowable stresses...........................................................48C 500 Burst test .........................................................................48

D. Construction Details ...........................................................48D 100 General ............................................................................48D 200 Welds ..............................................................................48D 300 Oil seals...........................................................................48D 400 Isolating valves ...............................................................48D 500 Relief valves....................................................................49

E. Testing.................................................................................. 49E 100 Non-destructive testing ...................................................49E 200 Other testing ....................................................................49

Rules for Ships, January 2000Pt.3 Ch.3 Sec.1 Page 5

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SECTION 1GENERAL REQUIREMENTS

A. ClassificationA 100 Application101 The Rules in this chapter apply to steering arrangementand anchoring, mooring and load handling equipment.102 Necessary strengthening of the hull structure due toloads imposed by the equipment and installations are givenwhere appropriate.

B. DefinitionsB 100 Symbols101

L = Rule length in m 1)B = Rule breadth in m 1)

D = Rule depth in m 1)T = Rule draught in m 1) = Rule displacement in t 1)CB = Rule block coefficient 1)V = maximum service speed in knots on draught T

1) For details see Ch.1 Sec.1 B

C. DocumentationC 100 General101 Plans and particulars to be submitted for approval or in-formation are specified in the respective sections of this chap-ter.

102 For instrumentation and automation, including compu-ter based control and monitoring, see Pt.4 Ch.9 Sec.1.


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SECTION 2STERNFRAMES, RUDDERS AND STEERING GEARS

A. GeneralA 100 Introduction101 Requirements to side thrusters and other appliances in-tended for manoeuvring or positioning purposes are given inPt.4 Ch.5.

A 200 Definitions201 Main steering gear means the machinery, rudder actua-tor(s), the steering gear power units, if any, and ancillaryequipment and the means of applying torque to the rudderstock (e.g. tiller or quadrant) necessary for effecting movementof the rudder for the purpose of steering the ship under normalservice conditions.202 Auxiliary steering gear means the equipment other thanany part of the main steering gear necessary to steer the ship inthe event of failure of the main steering gear but not includingthe tiller, quadrant or components serving the same purpose.203 Steering gear control system means the equipment bywhich orders are transmitted from the navigating bridge to thesteering gear power units. Steering gear control systems com-prise transmitters, receivers, hydraulic control pumps and theirassociated motors, motor controllers, piping and cables.204 Rudder actuator means the component which convertsdirectly hydraulic pressure into mechanical action to move therudder.205 Steering gear power unit means:

1) in the case of electric steering gear, an electric motor andits associated electrical equipment;

2) in the case of electrohydraulic steering gear, an electricmotor and its associated electrical equipment and connect-ed pump;

3) in the case of other hydraulic steering gear, a driving en-gine and connected pump.

206 Power actuating system means the hydraulic equipmentprovided for supplying power to turn the rudder stock, com-prising a steering gear power unit or units, together with the as-sociated pipes and fittings, and a rudder actuator. The poweractuating systems may share common mechanical compo-nents, i.e. tiller quadrant and rudder stock, or components serv-ing the same purpose.207 Maximum ahead service speed is the maximum speedcorresponding to maximum nominal shaft RPM and corre-sponding engine MCR in service at sea on summer load water-line.208 Maximum astern speed is the speed which it is estimatedthe ship can attain at the designed maximum astern power atthe deepest seagoing draught.209 Maximum working pressure means the maximum oilpressure in the system when the steering gear is operated tocomply with J102.210 For terms redundancy and independence see Pt.4 Ch.1Sec.1.211 Some terms used for rudder, rudder stock and supportingstructure are shown in Fig. 1.


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Fig. 1Rudders

212 Symbols:

f1 = material factor, see Bpm = maximum bearing surface pressure, see BFR = design rudder force, see DMTR= design rudder torque, see DA = total area in m2 of rudder bladeH = mean rudder height in m.

A 300 Documentation301 Plans etc. as specified below are to be submitted for ap-proval:

sternframe, horn and propeller brackets, outline of the pro-peller

rudder including details of bearings, shaft, pintles and rud-der lock arrangement

rudder stock including details of couplings, bolts and keys rudder carrier sectional drawing of rudder actuator dimension drawings for torque transmitting parts and parts

subject to internal hydraulic pressure foundation bolts and chocks rudder stoppers piping (and function) diagram according to Pt.4 Ch.6 schematic diagrams for:

power supply arrangement motor control systems (detailed requirements for the

diagrams are given in Pt.4 Ch.8 for electrical installa-tions)

calculations according to K402 and K403 if sea trials areplanned to be carried out in a load condition not providingfully submerged rudder. Such calculations are at least toinclude evaluation of expected trial loads (torque and sup-

port reaction forces) on the actuator versus calculated rud-der torque fully submerged and at trial conditions takinginto account the friction losses and any back pressure inthe return side.

The plans are to give full details of scantlings and arrangementas well as data necessary for verifying scantling calculationstogether with proposed rated torque. Set pressure for all reliefvalves are to be specified. Material specifications and particu-lars about heat treatment are also required.302 For important components of welded construction (e.g.rudder, rudder stock, tiller), full details of the joints, weldingprocedure, filler metal and heat treatment after welding are tobe specified on the plans.303 Procedure for stress relieving of nodular cast iron andcast steel parts, when dimensional stability is important (suchas tiller and rotor, see B502), is to be specified on the plans.304 Plans of the following items are to be submitted for in-formation:

general arrangement drawings of steering gear and steer-ing gear compartment

installation instructions for steering gear (inclusive fittingto rudder stock)

locking or brake arrangement steering gear relief valve discharge characteristics (pres-

sure-flow diagram) total delivery capacity of steering gear hydraulic pumps operation instructions (according to J1000).305 Steering gear manufacturers who intend their product tocomply with the requirements of the IMO Guidelines for non-duplicated rudder actuators, see Appendix A, are to submitdocumentation as specified in the guidelines when plans areforwarded for approval.306 For instrumentation and automation, including compu-ter based control and monitoring, see Pt.4 Ch.9 Sec.1.


DET NORSKE VERITAS

B. MaterialsB 100 Plates and sections101 Selection of material grades for plates and sections is tobe based on material thickness. NV-steel grades as given in Ta-ble B1 will normally be accepted.

102 The material factor f1 included in the various formulaefor structures may be taken as:f1 = 1,0 for NV-NS steelf1 = 1,08 for NV-27 steelf1 = 1,28 for NV-32 steelf1 = 1,39 for NV-36 steelf1 = 1,43 for NV-40 steel

B 200 Forgings and castings201 Rudder stocks, pintles, coupling bolts, keys and castparts of rudders are to be made of rolled, forged or cast carbonmanganese steel in accordance with Pt.2.For rudder stocks, pintles, keys and bolts the minimum yieldstress is not to be less than 200 N/mm2.202 Nodular cast iron may be accepted in certain parts afterspecial considerations. Materials with minimum specified ten-sile strength lower than 400 N/mm2 or higher than 900 N/mm2will normally not be accepted in rudder stocks, axle or pintles,keys and bolts.203 Ram cylinders, pressure housings of rotary vane type ac-tuators, hydraulic power piping, valves, flanges and fittings,and all steering gear components transmitting mechanical forc-es to the rudder stock (such as tillers, quadrants, or similarcomponents) are to be of steel or other approved ductile mate-rial, duly tested in accordance with the requirements of Pt.2. Ingeneral, such material is to have an elongation of not less than12 % nor a tensile strength in excess of 650 N/mm2.Grey cast iron may be accepted for redundant parts with lowstress level, excluding cylinders, upon special consideration.204 The material factor f1 for forgings (including rolledround bars) and castings may be taken as:

f = minimum upper yield stress in N/mm2, not to be takengreater than 70% of the ultimate tensile strength. If notspecified on the drawings, f is taken as 50% of the ul-timate tensile strength.

a = 0,75 for f > 235= 1,0 for f < 235

205 Before significant reductions in rudder stock diameterdue to the application of steels with yield stresses exceeding235 N/mm2 are granted, the Society may require the evaluationof the rudder stock deformations. Large deformations shouldbe avoided in order to avoid excessive edge pressures in wayof bearings. The slope of the stock should be related to thebearing clearance, see G405.

B 300 Bearing materials301 Bearing materials for bushings are to be stainless steel,bronze, white metal, synthetic material or lignum vitae. Stain-

less steel or bronze bushings are to be used in an approvedcombination with steel or bronze liners on the axle, pintle orstock.The difference in hardness of bushing and liners is not to beless than 65 Brinell. 13% Chromium steel is to be avoided.302 Synthetic bearing bushing materials are to be of an ap-proved type. For this type of bushing, adequate supply of lubri-cation to the bearing for cooling/lubrication purposes is to beprovided.303 The maximum surface pressure pm for the various bear-ing combinations is to be taken as given in Table B2.

Surface pressure exceeding the values in Table B2 may be ac-cepted for rudder actuator bearings in accordance with bearingmanufacturer's specification and when verified by tests.

B 400 Material certificates401 Det Norske Veritas Product Certificate (NV) will berequired for:

sternframe structural parts rudder structural parts rudder shaft or pintles rudder stock rudder carrier tiller or rotor crosshead cylinders/rams rotor housing manifolds.

402 Works certificate (W) will be accepted for: bolts and pins stoppers steering gear covers steering gear pistons.

B 500 Heat treatment501 Fabricated parts in the steering gear are to be fully an-nealed after welding.502 Nodular cast iron and cast steel parts for transmission ofrudder torque by means of keyless conical or cylindrical con-nections are to be stress relieved.

C. Arrangement and DetailsC 100 Sternframes and rudders101 Relevant types of rudder arrangements are shown in Fig.1. Other combinations of couplings and bearings may be ap-plied.102 Suitable arrangement to prevent the rudder from liftingand accidental unshipping is to be provided. The arrangement

Table B1 Plate material gradesThickness in mm Normal strength

structural steelHigh strength struc-

tural steelt 30 A A

30 < t 40 B A40 < t 120 D D

f1f

235---------

a

=

Table B2 Bearing surface pressuresBearing material pm (kN/m2)Lignum vitae 2500White metal, oil lubricated 4500Synthetic material with hardness between 60and 70 Shore D 5500

2)

Steel 1) and bronze and hot-pressed bronze-graphite materials 7000

1) Stainless and wear-resistant steel in an approved combination withstock liner

2) Surface pressure exceeding the specified limit may be accepted for rud-der bearing applications in accordance with bearing manufacturer'sspecification and when verified by tests and/or service experience.


DET NORSKE VERITAS

is to effectively limit vertical movement of rudder in case ofextreme (accidental) vertical load on rudder.103 Effective means are to be provided for supporting theweight of the rudder without excessive bearing pressure, e.g.by a rudder carrier attached to the upper part of the rudderstock. The hull structure in way of the rudder carrier is to besuitably strengthened.104 If the rudder trunk is open to the sea, a seal or stuffingbox is to be fitted above the deepest load waterline, to preventwater from entering the steering gear compartment and the lu-bricant from being washed away from the rudder carrier.An additional seal of approved type is required when the rud-der carrier is below the summer load waterline.105

Guidance note:The after body should be so shaped as to ensure a proper flow ofwater to the propeller, and so as to prevent uneven formation ofeddies as far as possible. The apex of the waterlines in front ofthe propeller should have the least possible radius, together witha relatively small angle . Plane or approximately plane partsabove the propeller tip should be avoided.The strength of pressure impulses from propeller to hull will nor-mally decrease with increasing clearances. However, even withlarge clearances to the propeller, a hull may be exposed to strongimpulses if the propeller is subject to heavy cavitation.For a moderately cavitating propeller, the following minimumclearances are proposed (see Table C1 and Fig. 2):

R = propeller radius in mZP = number of propeller blades.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

Fig. 2Propeller clearances

106Guidance note:Rudders (one or more) working directly behind a propellershould preferably have a total area not less than:

For ships which frequently manoeuvre in harbours, canals or oth-er narrow waters, the rudder area determined by the formulashould be increased. For ships with a streamlined rudder post,half of the lateral area of the post may be included in the rudderarea. For ships with a rudder horn, the whole area of the horn lay-ing below a horizontal line from the top of the rudder may be in-cluded.Rudders not working directly behind a propeller should have thearea as given above, increased by at least 30%.Rudders with special profiles or special configurations (e.g. flapsor nozzles) giving increased efficiency may have smaller total ar-eas.

For ships with large freeboard and/or high continuous super-structures an increase of the rudder area ought to be considered.Larger rudder area may result in excessive heeling angle whenusing the rudder in extreme position at full speed ahead. This isparticularly relevant for passenger vessels, ferries, vehicle ro/rocarriers and other vessels where the combination of speed,draught, vertical centre of gravity and metacentric height may re-sult in excessive heeling angle in case of smaller turning circles.For estimating the result angle of heel, reference is made to Pt.5Ch.2 Sec.2 K400.In cases where the resulting angle of heel may exceed 10 degrees,the Master should be provided with warning about this in the sta-bility manual.


107Guidance note:In order to minimise vibrations, the balancing and design of therudders should be carried out as follows:

the balanced portion should not be greater than 23% of thetotal area of the rudder

the length of the balanced part at any horizontal sectionshould nowhere be greater than 35% of the total length ofthe rudder

the widest part of the rudder section should preferably be atleast 30% aft of the leading edge of the rudder section con-sidered.


108 Over-balanced rudders are subject to special considera-tion with respect to type of steering gear and risk of an unex-pected and uncontrolled sudden large movement of ruddercausing severe change of ship's pre-set course. See J106.

Guidance note:A rudder shall be considered over-balanced, when balanced por-tion exceed 30% in any actual load condition. Special ruddertypes, such as flap rudders, are subject to special consideration.


C 200 Steering gears201 For arrangement and details of steering gear see subsec-tion J.

D. Design Loads and Stress AnalysisD 100 Rudder force and rudder torque, general101 The rudder force upon which the rudder scantlings are tobe based is to be determined from the following formula:

FR = 0,044 k1 k2 k3 A V2 (kN)A = area of rudder blade in m2, including area of flap.

= vertical projected area of nozzle rudder

Table C1 Minimum clearancesFor single screw ships: For twin screw ships:a 0,2 R (m)b (0,7 0,04 ZP) R (m)c (0,48 0,02 ZP) R (m) c (0,6 0,02 ZP) R (m)e 0,07 R (m)

A TL100--------- 1 50CB

2 BL----

2+ (m2 )=


DET NORSKE VERITAS

k1 = coefficient depending on rudder profile type (see Fig.3):

k2 = coefficient depending on rudder/nozzle arrangement= 1,0 in general= 0,8 for rudders which at no angle of helm work in the

propeller slip stream= 1,15 for rudders behind a fixed propeller nozzle

k3 = not to be taken greater than 4

H = mean height in m of the rudder area. Mean height andmean breadth B of rudder area to be calculated asshown in Fig. 4

At = total area of rudder blade in m2 including area of flapand area of rudder post or rudder horn, if any, withinthe height H.

V = maximum service speed (knots) with the ship on sum-mer load waterline. When the speed is less than 10knots, V is to be replaced by the expression:

For the astern condition the maximum astern speed is to beused, however, in no case less than:

Vastern = 0,5 VThe maximum service speed corresponds to the maximumcontinuous rating (MCR) of the engine. In special ship types(such as tugs) the maximum output of the propelling machin-ery may exceed MCR by more than 15%. In such cases V is tobe increased by the following percentage:

102 The rule rudder torque is to be calculated for both theahead and astern condition according to the formula:

MTR = FR xe (kNm)= minimum 0,1 FR B

FR = as given in 101 for ahead and astern conditionsxe = B ( - k) (m)B = mean breadth of rudder area, see Fig. 4 = 0,33 for ahead condition

= 0,66 for astern condition

k =

AF = area in m2 of the portion of the rudder blade area situ-ated ahead of the center line of the rudder stock

A = rudder blade area as given in 101.

For special rudder designs (such as flap rudders) direct calcu-lations of rudder torque, supported by measurements on simi-

lar rudders, may be considered as basis for rudder torqueestimation.

Fig. 3Rudder profiles

D 200 Rudders with stepped contours201 The total rudder force FR is to be calculated according to101, with height and area taken for the whole rudder.202 The pressure distribution over the rudder area may bedetermined by dividing the rudder into relevant rectangular ortrapezoidal areas, see e.g. Fig. 5. The rule rudder torque maybe determined by:

= minimum 0,1 FR xemn = number of partsi = integer

F Ri =

x ei = Bi ( - ki)

x em =

Ai = partial area in m2Bi = mean breadth of part area, see Fig. 4 = as given in 102

For parts of a rudder behind a fixed structure such as arudder horn:

= 0,25 for ahead condition= 0,55 for astern condition

ki =

A iF = rudder part area forward of rudder stock centre line,see Fig. 5

FR and A as given in 102.

Table D1 Rudder profile type - coefficientProfile type Ahead AsternNACA - Gttingen 1,1 0,8Hollow profile 1) 1,35 0,9Flatsided 1,1 0,9Profile with fish tail 1,4 0,8Rudder with flap 1,65 1,3Nozzle rudder 1,9 1,51) Profile where the width somewhere along the length is 75% or less of

the width of a flat side profile with same nose radius and a straight linetangent to after end

Table D2 Percentage increase in MCR vs VMaximum engine outputabove normal (%) 15 20 25 30 35 40V increase (%) 3 5 7 9 11 12

H2

At------ 2+

VminV 20+

3----------------=

AFA-------

MTR FRixei( ) (kNm)i 1=

n

=

AiA-----FR

AiBi( )A

----------------

i 1=

n

AiFAi

--------


DET NORSKE VERITAS

Fig. 4Rudder dimensions

Fig. 5Rudder area distribution

D 300 Stress analysis301 The rudder force and resulting rudder torque as given in100 and 200, causes bending moments and shear forces in therudder body, bending moments and torques in the rudder stock,supporting forces in pintle bearings and rudder stock bearingsand bending moments, shear forces and torques in rudderhorns and heel pieces.The bending moments, shear forces and torques as well as thereaction forces are to be determined by a direct calculation orby approximate simplified formulae as given in the following.For rudders supported by sole pieces or rudder horns thesestructures are to be included in the calculation model in orderto account for the elastic support of the rudder body.Acceptable direct calculation methods are given in Classifica-tion Note No. 32.1 Strength Analysis of Rudder Arrange-ments. For rudder horns, see also E404.302 Allowable stresses for the various strength members aregiven in subsections E to J.For evaluation of angular deflections, see B205 and G405.

E. Sternframes and Rudder HornsE 100 General101 Sternframes and rudder horns are to be effectively at-tached to the surrounding hull structures. In particular the sternbearing or vertical coupling flange for rudder axle is to be ap-propriately attached to the transom floor adjacent to the rudderstock.For semi-spade and spade rudder arrangements structural con-tinuity in the transverse as well as the longitudinal direction isto be specially observed.102 Cast steel sternframes and welded sternframes are to bestrengthened by transverse webs.Castings are to be of simple design, and sudden changes of sec-tion are to be avoided. Where shell plating, floors or otherstructural parts are welded to the sternframe, there is to be agradual thickness reduction towards the joint.Steel forgings and castings for sternframes, rudder horns andrudders are to be in accordance with the requirements in Pt.2Ch.2 Sec.5 and Sec.7 for general applications.103 Depending on casting facilities, larger cast steel propel-ler posts are to be made in two or more pieces. Sufficientstrength is to be maintained at connections. The plates of weld-ed propeller posts may be welded to a suitable steel bar at theafter end of the propeller post.104 Stresses determined by direct calculations as indicatedin D300 are normally not to exceed the following values:

Normal stress : = 80 f1 (N/mm2) Shear stress : = 50 f1 (N/mm2) Equivalent stress : e = 120 f1 (N/mm2)

E 200 Propeller posts201 The boss thickness at the bore for the stern tube is not tobe less than:

dp = rule diameter of propeller shaft in mm.

202 The scantlings of fabricated propeller posts are not to beless than:

l, b and t are as shown in Fig. 6 Alt. I.Where the section adopted differs from the above, the sectionmodulus about the longitudinal axis is not to be less than:

203 The scantlings of cast steel propeller posts are not to beless than:

e 12

22

12 32

+ +=

t 5 dp 60 (mm)=

l 53 L (mm)=

b 37 L (mm)=

t 2 4 L,f1

----------------- (mm)=

ZW1 35L L,

f1------------------------ (cm3 )=

l 40 L (mm)=

b 30 L (mm)=


DET NORSKE VERITAS

l, b, t1 and t2 are as shown in Fig. 6 Alt. II.Where the section adopted differs from the above, the sectionmodulus about the longitudinal axis is not to be less than:

When calculating the section modulus, adjoining shell plateswithin a width equal to 53 from the after end of the postmay be included.

Fig. 6Propeller posts

E 300 Sole pieces301 The sole piece is to be sloped in order to avoid pressurefrom keel blocks when docking. The sole piece is to extend atleast two frame spaces forward of forward edge of the propel-ler boss. The cross section of this extended part may be gradu-ally reduced to the cross section necessary for an efficientconnection to the plate keel.302 The section modulus requirement of the sole piece abouta vertical axis abaft the forward edge of the propeller post isgiven by:

ls = distance in m from the centre line of the rudder stockto the section in question. ls is not to be taken less thanhalf the free length of the sole piece.

303 The section modulus of the sole piece about a horizontalaxis abaft the forward edge of the propeller post is in no placeto be less than:

304 The sectional area of the sole piece is not to be less than:

E 400 Rudder horns401 The section modulus requirement of the rudder hornabout a longitudinal axis is given by:

lh = vertical distance in m from the middle of the horn pin-tle bearing to the section in question

yh = vertical distance in m from the middle of the rule pintlebearing to the middle of the neck bearing

F Ri = part of rudder force acting on the i-th part of the rudderarea, see D202

y ei = vertical distance in m from the centroid of the i-th partof the rudder area to the middle of the neck bearing

n = number of rudder parts

For the straight part of the rudder horn the section modulusmay be taken for the total sectional area of the horn.When the connection between the rudder horn and the hullstructure is designed as a curved transition into the hull platingthe section modulus requirement as given above is to be satis-fied by the transverse web plates as follows:

n = number of transverse websbi = effective breadth in mm of web no. i. (including the

flange thickness)ti = thickness in mm of web no. ibmax = largest bi.

Z, bi and bmax are to be taken at a horizontal section 0,7 r abovethe point where the curved transition starts (r = radius ofcurved part, see Fig. 7).The formula for ZW is based on the material in web plates andshell plate being of the same strength.For a cast rudder horn any vertical extension of the side plating(see Fig. 8) may be included in the section modulus.

t13 L

f1----------- (mm)=

t23 7 L,

f1----------------- (mm)=

ZC1 3L L,

f1--------------------- (cm3 )=

L

Z16 25FRls,

f1----------------------- (cm3 )=

Z2Z12

------ (cm3 )=

AS0 1FR,

f1---------------- (cm2 )=

Z15MVlh

yhf1-------------------- (cm3 )=

MV FRiyeii 1=

n

=

ZW

bi3ti

i 1=

n

6000bmax------------------------ 0 45Z,=


DET NORSKE VERITAS

Fig. 7Curved plate transition rudder horn/shell plating

Fig. 8Curved cast transition rudder horn/shell plating

402 The rudder horn thickness requirement is given by:

k =

eh = horizontal projected distance in m from the centre lineof the horn pintle to the centroid of AS

AS = area in cm2 in horizontal section enclosed by the horn.

For a curved transition between horn plating and shell platingthe thickness of the transition zone plate is not to be less than:

s = spacing between transverse webs in mmr = radius of curved transition in mmZA = section modulus at section immediately below the

transition zoneZ = section modulus requirement in same section, as given

in 401.

403 The vertical parts of the rudder horn participating in thestrength against transverse shear are to have a total area in hor-izontal section given by:

C =

= 1,0 at lower endAH = area of horn in m2. At intermediate sections AH should

be taken for part of horn below sectionA = total area of rudder in m2.

In a curved transition zone the thickness of the transverse webplates is not to be less than:

tr = 0,8 tc (mm)tc = thickness of curved plate

In the transition zone the curved shell plate is to be welded tothe web plates by full penetration weld or by a fillet weld withthroat thickness not less than:

t = 0,55 f1 tr (mm)404 A direct stress analysis of the rudder horn, if carried out,is to be based on a finite element method.For a curved transition to the hull structure the maximum al-lowable normal and equivalent stresses as given in 104, may inthe curved plate be increased to:

= 120 f1 N/mm2

e = 180 f1 N/mm2

A fine-mesh finite element calculation will be considered as anacceptable method.In the web plates the normal stresses should not exceed = 130 f1 N/mm2.405 For a curved transition between the horn side plating andthe shell plating, the side plate thicknesses given in 401 to 404are to be extended to the upper tangent line of the curved part.

t110kFReh

f1AS------------------------- (mm)=

50

4000 1500 Z ZA( )2

---------------------------------------------------------

tc0 15 s 40( )2,

r----------------------------------

ZZA------- (mm)=

AW C0 3FR,

f1---------------- (cm2 )=

1A AH+( )AH

A2--------------------------------+

at upper end of horn


DET NORSKE VERITAS

The transverse web thicknesses are to be kept to the same leveland are to be welded to the floors above. No notches, scallopsor other openings are to be taken in the transition area.The alternative design is to carry the side plating of the rudderhorn through the shell plate and connect it to longitudinal gird-ers (see Fig. 9), or weld it to the shell plate in line with longi-tudinal girders. In the latter case the welds below and above theshell plate are to be full penetration welds, and the shell plateis to be specially checked for lamellar tearing. The transversegirders are to be connected to/supported by transverse floors.Floor plating welded to rudder horn web plates is to have athickness not less than 75% of the web plate thickness.406 The lower end of the rudder horn is to be covered by ahorizontal plate with thickness not less than the side plating.

Fig. 9Shell plating connected to longitudinal girders in line with rudderhorn sides

F. RuddersF 100 General arrangement and details101 Rudders are to be double plate type with internal verticaland horizontal web plates.The rudder body is to be stiffened by horizontal and verticalwebs enabling it to act as a girder in bending.Single plate rudders may be applied to smaller vessels of spe-cial design and with service restrictions, see 500.102 All rudder bearings are to be accessible for measuring ofwear without lifting or unshipping the rudder.

Guidance note:In case cover plates are permanently welded to the side plating,it is recommended to arrange peep holes for inspection of secur-ing of nuts and pintles.


103 Great care is to be taken in highly stressed connectionssuch as:

welds between rudder side plating and upper heavy part ofrudder at stock coupling

welds around cut-outs in semi-spade rudders and openingsfor demounting of cone coupling and pintles.

104 Welds between plates and heavy pieces (cast or verythick plating) are to be made as full penetration welds, prefer-ably to cast or welded on ribs. Where back welding is impos-sible welding is to be performed against backing bar orequivalent.105 Webs are to be connected to the side plates in accord-ance with Ch.1 Sec.12.Slot-welding is to be limited as far as possible. Horizontal slotsin side plating in areas with large bending stresses are to becompletely filled by welding.Normally, slots of length 75 mm and a breadth of 2 t (where t= rudder plate thickness), with a distance of 125 mm betweenends of slots, will be accepted. In areas where slots are requiredto be completely filled by welding, more narrow slots with in-clined sides (minimum 15 to the vertical) and a minimumopening of 6 mm at bottom may be used. A continuous slotweld may, however, in such cases be more practical.106 Plate edges at corners in cut-outs and openings in rudderside plating are to be ground smooth in those parts of the rud-der where high stresses will occur.107 Means for draining the rudder completely after pressuretesting or possible leakages is to be provided. Drain plugs areto be fitted with efficient packing.108 Internal surfaces are to be covered by a corrosion-resist-ant coating after pressure-testing and possible stress-relieving.109 For testing of rudder, see K.

F 200 Rudder plating201 The thickness requirement of side, top and bottom plat-ing is given by:

ka =

maximum 1,0

s = the smaller of the distances between the horizontal orthe vertical web plates in m

b = the larger of the distances between the horizontal or thevertical web plates in m.

In no case the thickness is to be less than the minimum sideplate thickness as given in Ch.1 Sec.7 C101 or Ch.2 Sec.6C102.

F 300 Rudder bending301 Bending moments in the rudder are to be determined bydirect calculations as indicated in D300.For some common rudder types the following approximateformulae may be applied:

t 5 5,f1

---------kas T0 1FR,

A----------------+ 2 5 (mm),+=

1 1 0 5 sb---

2,,


DET NORSKE VERITAS

For balanced rudders with heel support:Mmax = 0,125 FR H (kNm)

For semi-spade rudders at the horn pintle:

For spade rudders:

A1 = area in m2 of the rudder part below the cross-section inquestion

hs = vertical distance in m from the centroid of the rudderarea A1 to the section in question.

302 The nominal bending stress distribution in the ruddermay normally be determined on the basis of an effective sec-tion modulus to be estimated for side plating and web plateswithin 40% of the net length (cut-outs or openings deducted)of the rudder profile. The effective length is not to be takengreater than 2,5 ds (ds = rudder stock diameter at neck bearing)or the length of the flange coupling at the top of the rudder.Special attention to be paid to open flange couplings on therudder. The external transverse brackets will normally have tobe supplied with heavy flanges to obtain the necessary sectionmodulus of the rudder immediately below the flange.As an alternative the bending stress distribution in the ruddermay be determined by a finite element calculation.303 Nominal bending stresses calculated as given in 301 and302 are not to exceed:

= 110 f1 N/mm2 in general= 75 f1 N/mm2 at sections in way of cut-outs (e.g. semi-

spade rudders) in the rudder.In case of openings in side plate for access to cone coupling orpintle nut, = 90 f1 to be applied when the corner radius isgreater than 0,15 l ( l = length of opening), = 60 f1 when theradius is smaller.

F 400 Web plates401 The thickness of vertical and horizontal webs is not to beless than 70% of the thickness requirement given in 200, in nocase less than 8 mm.402 The total web area requirement for the vertical webs isgiven by:

P =

with heel support

= for spade rudder or lower part of

semi-spade rudderh1 = height in m of the smaller of rudder parts below or

above the cross-section in questionh2 = height in m of the rudder part below the cross section

in question.

Shear stresses in web plates determined by direct stress calcu-lations are not to exceed:

= 50 f1 (N/mm2)

Equivalent stress is not to exceed:

e =

= 120 f1 N/mm2 in rudder-blades without cut-outs= 100 f1 N/mm2 in rudder-blades with cut-outs.

F 500 Single plate rudders501 Mainpiece diameterThe mainpiece diameter is calculated according to G201. Forspade rudders the lower third may taper down to 0,75 timesstock diameter.When calculating the rudder force FR as given in D101 the fac-tor k1 may be taken equal to 1,0 in ahead condition.502 Blade thicknessThe blade thickness is not to be less than:

tb = 1,5 s V + 2,5 (mm)s = spacing of stiffening arms in metres, not to exceed 1 mV = speed in knots, see D101.

503 ArmsThe thickness of the arms is not to be less than the blade thick-ness:

ta = tbThe section modulus is not to be less than:

Za = 0,5 s C12 V2 (cm3)C1 = horizontal distance from the aft edge of the rudder to

the centre line of the rudder stock in metres.For higher tensile steels the material factor according to B100is to be used correspondingly.

F 600 Mounting of rudder601 For rudder with continuous shaft it is to be checked thatthe rudder shaft has the right position in relation to the uppercoupling, both longitudinally and transversely, when the lowertapered part of the rudder axle bears hard at the heel. The rud-der shaft is to be securely fastened at the heel before the cou-pling bolts at the upper end are fitted.602 Before final mounting of rudder pintles, the contact be-tween conical surfaces of pintles and their housings is to bechecked by marking with Prussian blue or by similar method.When mounting the pintles, care is to be taken to ensure thatpackings will not obstruct the contact between mating surfac-es. The pintle and its nut are to be so secured that they cannotmove relatively to each other.

G. Rudder Stocks and ShaftsG 100 General101 Stresses determined by direct calculations as indicatedin D300 are normally to give equivalent stress e not exceed-ing 118 f1 N/mm2 and shear stress not exceeding 68 f1 N/mm2. The equivalent stress for axles in combined bending andtorsion may be taken as:

= bending stress in N/mm2 = torsional stress in N/mm2.

102 The requirements to diameters are applicable regardlessof liner. Both ahead and astern conditions are to be considered.

MFRA1hs

A------------------- (kNm)=

MmaxFRA1hs

A------------------- (kNm)=

AWP

5f1------- (cm2 )=

0 6h1H-----,

FR for balanced rudder

h2H-----FR

b2 32+

e 2 32+ (N/mm2 )=


DET NORSKE VERITAS

103 A rudder stock cone coupling connection without hy-draulic arrangement for mounting and dismounting is not to beapplied for spade rudders.104 An effective sealing is to be provided at each end of thecone coupling.

G 200 Rudder stock with couplings201 The diameter requirement is given by:

kb = 1 above the rudder carrier, except where the rudderstock is subjected to bending moment induced by therudder actuator (bearing arrangement versus rudderstock bending deflections, or actuator forces acting ontiller)

=

MB = calculated bending moment in kNm at the section inquestion.

If direct calculations of bending moment distribution are notcarried out, MB at the neck bearing or the rudder coupling maybe taken as follows:

for balanced rudder with heel support:

for semi-spade rudder:

for spade rudder:MB = FR hs (kNm)

hs = vertical distance in m from the centroid of the rudderarea to the middle of the neck bearing or the coupling.

At the bearing above neck bearing MB = 0, except as follows:

for rotary vane type actuators with two rotor bearings,which allow only small free deflections, calculation ofbending moment influence may be required if bending de-flection in way of upper bearing exceeds two times dia-metrical bearing clearances at full rudder force FR

for actuator force induced bending moment the greater ofthe following:

M BU = FA hA (kNm)or

M BU = PA hA (kNm)hA =vertical distance between force and bearing centrePA =according to J404M BU =bending moment at bearing above neck bearing.

Minimum diameter of the rudder stock between the neck andthe bearing above is not to be less than if tapered with kb=1,0at the second bearing.202 Tapered cone connections between rudder stock andrudder and steering gear are to have strength equivalent to thatrequired for rudder stock with respect to transmission of torqueand bending moments as relevant and are to comply with thefollowing:

a) Length/diameter ratio:

b) Hub/shaft diameter ratio D/ds:

c) Taper of cone:

d) Contact surface roughness in micron:

contact area minimum 70% evenly distributed (seeK200 for control and testing)

if oil is used for fitting, the design must enable escapeof the oil from between the mating surfaces

the connection is to be secured by a nut which is prop-erly locked to the shaft.

e) The dimensions at the slugging nut are not to be less than(see Fig. 10):

external thread diameter:dg = 0,65 ds

height of nut:hn = 0,6 dg

outer diameter of nut:

dn = 1,2 dt or dn = 1,5 dg whichever is the greater.

f) Average surface pressure pr due to shrinkage for transmis-sion of torque by means of friction is to be:

T fr = required torque to be transmitted by means of fric-tion in following couplings:

1) Keyless rudder stock connections to: rudder: 3 MTR steering gear: 2 Tdes T fr 2 MTR

2) Keyed rudder stock connections to: rudder: 1,5 M TR (0,5 MTR) steering gear: T fr TW (0,25 TW)(figures in parentheses are subject to specialconsideration - see 203)

dm = mean diameter = 0,5 (ds + dt) (mm)l = effective cone length, which may normally be tak-

en as boss length lt, see Fig. 10, (mm)mu = maximum 0,14 for oil injection fitting

= maximum 0,17 for dry fittingMTR = rule rudder torque (kNm), see D102 and D202Tdes = maximum torque corresponding to steering gear

design pressure, or safety valve opening pressure(kNm) - see J404 for calculation of Tdes

Tw = effective steering gear torque at maximum workingpressure (kNm).

ds 42kbMTR

f1------------

13---

(mm)=

1 43---

MBMTR------------

2+

16---

at arbitrary cross-section

MBFRH

7----------- (kNm)=

MBFRH17

----------- (kNm)=

Connection Rudder Steering gearlt/ds 1,5 0,75

Type With key KeylessD/ds 1,5 1,25

Type With key Keylesstaper 1:10 - 1:15 1: 15

Type of fitting Dry fitted Oil injectionroughness (RA) maximum 3,5 maximum 1,6

pr2Tfr10

6

dm2l

------------------- (N/mm2 )


DET NORSKE VERITAS

g) The surface pressure (p) used for calculation of pull-uplength is not to be taken less than:

pr pmin 1,25 pb (N/mm2)and is not to exceed:

k = 0,95 for steel forging and cast steel= 0,90 for nodular cast iron= 0,50 for keyed connections.

Variation due to different hub wall thickness is to be con-sidered.Pressure at the bigger end due to bending moment, Mb,may be taken as:

which may be reduced to zero at a distance l x = 0,5 d or0,5 l (smaller applies) as follows:

p bx = pressure due to bending moment at position xlx = distance from top of cone, see Fig. 10 (mm)dx = ditto shaft diameter at distance lx (mm)Mb = bending moment (kNm).

h) Shrinkage allowance (mm):

Ei = module of elasticity of shaft (N/mm2)Ee = module of elasticity of hub (N/mm2)i = Poisson's ratio for shafte = Poisson's ratio for hubci = diameter ratio di/d at considered sectionce = diameter ratio d/D at considered sectiondi = diameter of centre bore in shaft (mm)d = shaft diameter at considered section (mm)D = outer diameter of the hub at considered section

(mm).Minimum shrinkage allowance may be calculated basedon average diameters and the surface pressure (pmin) fromthe above equation.However, in case hub wall thickness have large variationseither longitudinally or circumferencially this equation isnot valid.Maximum shrinkage allowance is to be calculated basedon maximum permissible surface pressure (pmax, see g).

i) Pull-up length, minimum:min = K ( min + 2 (R Ai + RAe) 10-3 ) (mm)

min 2 mm for all keyless rudder - rudder stock connec-tions.

j) Pull-up length, maximum:max = K ( max + 2 (R Ai + RAe) 10-3 ) (mm)

= pull-up length (mm)

K = taper of the cone = lt/(ds dt)min = calculated minimum shrinkage allowancemax =calculated maximum shrinkage allowanceR Ai = surface roughness RA of shaft (micron)R Ae = surface roughness RA of hub (micron).

k) Necessary force for pull-up may be estimated as follows:

pu = average friction coefficient for pull-up (for oil in-jection (usually in the range 0,01 to 0,03).203 Tapered key-fitted (keyed) connections are to be de-signed to transmit rudder torque in all normal operating condi-tions by means of friction in order to avoid mutual movementsbetween rudder stock and hub. The key is to be regarded as asecuring device.For calculation of minimum and maximum pull-up length see202 i) and j).Where it is not possible or practicable to obtain above requiredminimum pull-up, special attention is to be given to fitting ofthe key in order to ensure tight fit (no free sideways play be-tween key and key-way).Tapered key-fitted connections are in addition to comply withfollowing:

a) Key-ways shall not be placed in areas with high bendingstresses in the rudder stock and are to be provided with suf-ficient fillet radii (r):

r 0,01 dsb) The abutting surface area between the key and key-way in

the rudder stock and hub respectively, is not to be lessthan:

where the torque Tkey is (kNm):1,5 Tdes Tfr Tkey 2 M TR Tfr

based on verification of pull-up force, and1,5 Tdes 0,7 Tfr Tkey 2 MTR 0,7 Tfr

based on verification of pull-up distance,but not less than:

Tkey = M TR (kNm).Yield strength used for calculation of fk is to exceed thelowest of:

f,keyand

1,5 f, hub (for calculation of hub) or1,5 f, stock (for calculation of stock).

A ab =effective abutting area of the key-way in stockand hub respectively (cm2)

fk =material factor (see B204)f,hub =yield strength of hub material (N/mm2)f,key =yield strength of key material (N/mm2)f,stock=yield strength of stock material (N/mm2).

c) The height/width ratio of the key is to be:

h = height (thickness) of the keyb = width of the key.

pmax kf1 ce

2

3 ce4

+

--------------------- pb (N/mm2 )

pb3 5Mb,

dml2

-----------------106 (N/mm2 )=

pbx pb18 1lx

0 5dx,--------------

(N/mm2 )=

d pEe------

1 ce2

+

1 ce2

----------------- ve+

pEi-----

1 ci2

+

1 ci2

---------------- vi

+=

F dmlpr1

2K------- pu+

103 (kN)

Aab65Tkey

dmfk----------------- (cm2 )

hb--- 0 6,


DET NORSKE VERITAS

Where necessary tapered connections are to be provided withsuitable means (e.g. oil grooves and bores to connect hydraulicinjection oil pump) to facilitate dismantling of the hub.204 Connection between rudder stock and splitted type oftiller or quadrant or rotor are to comply with 202 and 203 as ap-plicable and with the following:

boss halves are to be joined by at least four bolts (two ineach side)

one or two keys cylindrical connections are to be duly secured with regard

to axial loads.

205 Tiller or rotor joined to rudder stock by means of speciallocking assemblies, or by means of tapered connection with in-termediate sleeve, which transmit torque and/or axial forces bymeans of friction alone are to comply with the following:

a)2,5 Tdes Tfr 2,5 MTR

T fr = calculated friction torque.Tdes and MTR, see 202.

b) When number of locking assemblies is less than three, anarrangement is to be provided to limit drop of the rudderand stock in case of a slip in the friction connection.

Fig. 10Cone coupling

206 Where the rudder stock is connected to the rudder byhorizontal flange coupling the following requirements are tobe complied with:

a) At least 6 coupling bolts are to be used.b) The diameter of coupling bolts is not to be less than:

ds = rule diameter of rudder stock at coupling flange inmm as given in 201

n = number of coupling boltse = mean distance in mm from the centre of bolts to the

centre of the bolt systemf ms = material factor (f1) for rudder stockf mb = material factor (f1) for bolts.

c) Nuts are to be securely fastened by split pins or other effi-cient means.

d) If the coupling is subjected to bending stresses, the meandistance a from the centre of the bolts to the longitudinalcentre line of the coupling is not to be less than 0,6 ds.

e) The width of material outside the bolt holes is not to beless than 0,67 db.

f) The thickness of coupling flanges is not to be less than thegreater of:

db = bolt diameter, calculated for a number of bolts notexceeding 8

f mf = material factor (f1) for flange,or

MB = bending moment in kNm at couplinga = mean distance from centre of bolts to the longitudi-

nal centre line of the coupling, in mmd = diameter as built of rudder stock for stock flange,

breadth of rudder for rudder flange, both in mm = factor to be taken from the following table:

Ample fillet radius is to be in accordance with recognisedstandards.

G 300 Rudder shaft301 At the lower bearing, the rudder shaft diameter is not tobe less than:

c =

l, a and b are given in Fig. 11 in m.The diameter df below the coupling flange is to be 10% greaterthan dl. If, however, the rudder shaft is protected by a corro-sion-resistant composition above the upper bearing, df may beequal to dl.302 The taper, nut, etc. at lower end of rudder shafts, is to betaken as for rudder stock given in 202.303 The scantlings of the vertical coupling at the upper endof the rudder shaft are to be as required for horizontal ruddercouplings in 206, inserting the shaft dl instead of the stock di-ameter ds in the formula for bolt diameter.

db 0 62ds

3fmsnefmb---------------- (mm),=

d/a 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,8 1,5 1,25 1,0 0,8 0,6 0,45 0,35 0,25

t dbfmbfmf-------- , minimum 0,9db (mm)=

t 70MBafmf------------ (mm)=

dl 39FRc l c( )

lf1-------------------------

13---

(mm)=

a b+2

------------


DET NORSKE VERITAS

Fig. 11Rudder shaft

G 400 Bearings and pintles401 The height of bearing surfaces is to be taken not greaterthan:

hb = 1,2 dsl (mm)dsl = diameter in mm of rudder shaft or pintle measured on

the outside of liners.

402 The bearing surface area is not to be less than:

AB = hb dslhb and dsl = as given in 401P = calculated reaction force in kN at the bearing in

questionpm = maximum surface pressure as given in B303.

If direct calculations of reaction forces are not carried out, P atvarious bearings may be taken as given in the following (notethat values given for stern pintle or neck bearing in semi-spaderudders are minimum values):a) For balanced rudder with heel support:

P = 0,6 FR (kN) at heel pintle bearingP = 0,7 FR (kN) at stern pintle or neck bearingP = 0,1 FR (kN) at upper bearing.

b) For semi-spade rudder (The horn pintle bearing is assumedto be situated not more than 0,1 H above or below the cen-troid of the rudder):P = 1,1 FR (kN) at horn pintle bearingPmin = 0,4 FR (kN) at stern pintle or 0,3 FR (kN) at neckbearingP = 0,1 FR (kN) at upper bearing.

c) For spade rudder:

(kN) at neck bearing

(kN) at upper bearing

h1 = vertical distance from the centroid of rudder area tothe middle of the neck bearing

h2 = vertical distance from the middle of the neck bear-ing to the middle of the upper bearing.

403 The diameter of pintles is not to be less than:

P = as given in 402.

404 The thickness of any bushings in rudder bearings is notto be less than:

minimum 8 mm for steel and bronze,maker's specification for synthetic materials,minimum 22 mm for Lignum Vitae,other materials are to be especially considered.P = as given in 402.The bushing is to be effectively secured to the bearing. Thethickness of bearing material outside of the bushing is not tobe less than:

P = as given in 402.

405 With metal bearings the clearance on the diameter isnormally not to be less than:

0,001 db + 1,0 (mm)db=inner diameter in mm of the bushing.If non-metallic bearing material is applied, the bearing clear-ance is to be specially determined considering the materials'swelling and thermal expansion properties. This clearance isnot to be taken less than 1,5 mm on the bearing diameter.

ABP

Pm------- 106 (mm2 )=

Ph1 h2+

h2-----------------FR=

Ph1h2-----FR=

dp 10Pf1---- (mm)=

tv 0 32 P (mm),=

t 2 0 Pf1---- (mm),=


DET NORSKE VERITAS

For spade rudders with large bending moment and inducedslope at the neck bearing the clearance should be related to thecalculated angular deflection over the bearing length.Due attention should, however, be given to the manufacturer'srecommended clearance. For pressure lubricated bearings theclearance will be especially considered.406 Pintles are to have a conical attachment to the gudgeons.The various dimensions (taper, nut, key) are to be as requiredfor rudder stock in 202 and 203 inserting the pintle diameter dpinstead of the stock diameter ds in the various formulae.The bending moment, MB may be taken as pintle force P mul-tiplied by the height from 1/3 of height of bearing to 1/2 of thelength of cone and MTR may be taken as 0,00025 dbP.

db = inner diameter of bushing (mm).The length of pintle housing is not to be less than the pintle di-ameter and the thickness of material outside the bushing is notto be less than 0,25 db.An effective sealing against sea water is to be provided at bothends of the cone.

H. Propeller NozzlesH 100 General101 The following requirements are applicable to fixed andsteering nozzles of inner diameter 4 metres or less.

Guidance note:The requirements may also be applied for the initial design ofnozzles with diameter exceeding 4 metres.In that case the scantlings and arrangement should be speciallyconsidered with respect to exciting frequencies from the propel-ler.


H 200 Plating201 The thickness of the nozzle shell plating in the propellerzone is not to be less than:

where:

N = 0,01 PS D, need not be taken greater than 100PS = maximum continuous output (kW) delivered to the

propellerD = inner diameter (m) of nozzles = distance in m between ring webs, is not to be taken less

than 0,35 metres in the formulaka = aspect ratio correction as given in F201, to be applied

when longitudinal stiffeners.

The thickness in zone I and II is not to be less than 0,7 t and inzone III not less than 0,6 t, corrected for spacing s.The propeller zone is to be taken minimum 0,25 b (where b =length of nozzle). For steering nozzles the propeller zone is tocover the variations in propeller position.On the outer side of the nozzle, zone II is to extend beyond theaftermost ring web.202 The thickness of ring webs and fore and aft webs is notto be taken less than 0,6 t. They are to be increased in thicknessin way of nozzle supports.203 If the ship is reinforced according to an ice class nota-tion, the part of the outer shell of the nozzle which is situatedwithin the ice belt is to have a plate thickness not less than cor-

responding to the ice class requirement for the after part of theship.

Guidance note:In order to prevent corrosion and erosion of the inner surface ofthe nozzle, application of a corrosion resistant material in thepropeller zone is recommended. All but welds should be groundsmooth.When a corrosion resistant material is used, the plate thicknessmay be reduced by 15%.


H 300 Nozzle ring stiffness301 In order to obtain a satisfactory stiffness of the nozzlering the following requirement is to be fulfilled:

I = 2,8 k b D3 V2 (cm4)I = moment of inertia of nozzle section about the neutral

axis parallel to centre line

k =

tm = mean thickness of nozzle inner and outer shell plating(mm), in propeller planeb = length of nozzle, see Fig. 12, in mD = as given in 201V = maximum service speed (knots)n = number of ring webs.

Fig. 12Section through nozzle ring

302 If the ship is reinforced according to an ice class notationthe parameter V for the requirement in 301 is not to be takenless than:

V = 14, 15, 16 and 17 knots for ice class 1C, 1B, 1A and1A*, respectively.

H 400 Welding401 The inner shell plate is to be welded to the ring webswith double continuous fillet welding.402 The outer shell plate is as far as possible to be weldedcontinuously to the ring webs. Slot welding may be acceptedon the following conditions:If the web spacing s 350 mm all welds to outer plating maybe slot welds. If the web spacing s > 350 mm at least two ringwebs are to be welded continuously to the outer shell. A con-tinuous weld according to Fig. 13 may be accepted.403 Slot welds are to have a slot length l not less than 75 mmand a breadth equal to 2t (t = nozzle shell plate thickness),maximum 30 mm. More narrow slots may be applied whereslots are completely filled by welding. The distance betweenslots (from centre to centre) is not to exceed 2l, maximum 250 mm. The slot weld throat thickness is normal-ly to be 0,7 t.

t 10 3kasNf1---- (mm)+=

28bDtm n 1+( )

--------------------------------


DET NORSKE VERITAS

H 500 Supports501 The nozzle is to be supported by at least two supports.The web plates and shell plates of the support structure are tobe in line with web plates in the nozzle.

Fig. 13Connection nozzle shell plate/ring web

I. Propeller Shaft BracketsI 100 General101 The following requirements are applicable to propellershaft brackets having two struts to support the propeller tailshaft boss. The struts may be of solid or welded type.102 The angle between the struts is not to be less than 50 de-grees.

I 200 Arrangement201 Solid struts are to be carried continuously through theshell plating and are to be given satisfactory support by the in-ternal ship structure.202 Welded struts may be welded to the shell plating. Theshell plating is to be reinforced, and internal brackets in linewith strut plating are to be fitted. If the struts are built with alongitudinal centre plate, this plate is to be carried continuous-ly through the shell plating. The struts are to be well roundedat fore and aft end at the transition to the hull.203 The propeller shaft boss is to have well rounded fore andaft brackets at the connection to the struts.204 The strut structure inside the shell is to terminate withina compartment of limited volume to reduce the effect of flood-ing in case of damage.

I 300 Struts301 Solid or built-up struts of propeller shaft brackets are tocomply with the following requirements:

h = 0,4 d (mm)A = 0,4 d2 (mm2)

W = 0,12 d3 (mm3)A = area of strut sectionW = section modulus of section. W is to be calculated with

reference to the neutral axis Y-Y as indicated on Fig.14

h = the greatest thickness of the sectiond = Propeller shaft diameter in mm.

The diameter refers to shaft made of steel with a minimumspecified tensile strength of 430 N/mm2.

Fig. 14Strut section

I 400 Welding401 Welding between struts and hull and propeller shaft bossis to be made as full penetration welds.402 For welded construction full details of the joints, weld-ing procedure, filler metal and heat treatment after welding areto be specified on the plans.

I 500 Material501 Regarding material of brackets reference is made to sub-section B.

I 600 Testing601 Ultrasonic and magnetic particle examination of thewelds is to be carried out on the brackets and at the shell pen-etrations.

J. Steering GearsJ 100 Arrangement and performance101 Unless expressly provided otherwise, every ship shall beprovided with a main steering gear and an auxiliary steeringgear to the satisfaction of the requirements in the Rules. Themain steering gear and the auxiliary steering gear shall be soarranged that the failure of one of them will not render the oth-er one inoperative.102 The main steering gear and rudder stock shall be:

a) of adequate strength and capable of steering the ship atmaximum ahead service speed which shall be demonstrat-ed

b) capable of putting the rudder over from 35 on one side to35 on the other side with the ship at its deepest seagoingdraught and running ahead at maximum ahead servicespeed and, under the same conditions, from 35 on eitherside to 30 on the other side in not more than 28 seconds(20 seconds for class notation Tug or Supply Vessel,see Pt.5 Ch.7 Sec.2 and Sec.3 and ice classes: ICE 05-15,POLAR 10-30 and 15 seconds for Icebreaker, see Pt.5Ch.1 Sec.4)

c) operated by power where necessary to meet the require-ments in b) and in any case when the rules require a rudderstock of over 120 mm diameter in way of the tiller, exclud-ing strengthening for navigation in ice

d) so designed that they will not be damaged at maximumastern speed.

103 The auxiliary steering gear shall be:

a) of adequate strength and capable of steering the ship atnavigable speed and of being brought speedily into actionin an emergency

b) capable of putting the rudder over from 15 on one side to15 on the other side in not more than 60 seconds with theship at its deepest seagoing draught and running ahead atone half of the maximum ahead service speed or 7 knots,whichever is the greater


DET NORSKE VERITAS

c) operated by power where necessary to meet the require-ments in b) and in any case when the rules require a rudderstock of over 230 mm diameter in way of the tiller, exclud-ing strengthening for navigation in ice.

Guidance note:Manually operated gears are only acceptable when the operationdoes not require an effort exceeding 160 N under normal condi-tions.


104 Where the main steering gear comprises two or moreidentical power units, an auxiliary steering gear need not be fit-ted, provided that:

a) in a passenger ship, the main steering gear is capable ofoperating the rudder as required in 102 b) while any one ofthe power units is out of operation

b) in a cargo ship, the main steering gear is capable of oper-ating the rudder as required in 102 b) while operating withall power units

c) the main steering gear is so arranged that after a single fail-ure in its piping system or in one of the power units the de-fect can be isolated so that steering capability can bemaintained or speedily regained.

Auxiliary gear need not be fitted when the ship is providedwith:

two rudders, each with its own steering gear and capableof steering the vessel with any one of the rudders out of op-eration, or

fitted with an approved alternative means of steering, suchas azimuth thruster, capable of steering the vessel with therudder out of operation and provided with approved re-mote control from the bridge or

for non-propelled vessels.

105 In every oil carrier, chemical carrier or liquefied gas car-rier of 10 000 tons gross tonnage and upwards and in every oth-er ship of 70 000 tons gross tonnage and upwards, the mainsteering gear shall comprise two or more identical power unitscomplying with the requirements in 104.106 Steering gears for over-balanced rudders, which are sub-ject to C108, are to be designed to prevent a sudden turn of rud-der in case of loss of steering gear torque due to a single failurein the steering gear power or control systems, inclusive failurein power supply.107 Main and auxiliary steering gear power units shall be:

a) arranged to restart automatically when power is restoredafter a power failure

b) capable of being brought into operation from a position onthe navigating bridge. In the event of a power failure toany one of the steering gear power units, an audible andvisual alarm shall be given on the navigating bridge

c) arranged so that transfer between units can be readily ef-fected.

108 Where the steering gear is so arranged that more thanone system (either power or control) can be simultaneously op-erated, the risk of hydraulic locking caused by a single failureis to be considered.

Guidance note:The hydraulic locking is a phenomenon which may be experi-enced when two hydraulic systems (usually identical) worksagainst each other.


109 Steering gears are to be mounted on substantial seatings,which will effectively transmit the rudder torque to the hullstructure. Deck plating under rudder carrier is to be of substan-tial thickness. Prior to installation all welding near the seatingshave to be completed. The deck underneath is to be efficientlysupported to take the weight of steering gear and rudder withrudder stock.110 Suitable stopping arrangements are to be provided forthe rudder. The stoppers may be an integral part of the rudderactuator. Power cut-out to the actuator is to operate at a smallerangle of helm than those for the rudder, and are to be synchro-nised with the gear itself and not with the control system.111 Steering gears, other than of the hydraulic type, will beaccepted provided the standards are considered equivalent tothe requirements of this section.112 The steering gear compartment shall be:

a) readily accessible and, as far as practicable, separatedfrom machinery spaces

b) provided with suitable arrangements to ensure working ac-cess to steering gear machinery and controls.These arrangements shall include handrails and gratings orother non-slip surfaces to ensure suitable working condi-tions in the event of hydraulic fluid leakage.

(SOLAS reg. II-1/29.13)113 Electrical power units are to be placed on elevated plat-forms in order to avoid water splash.114 A means of communication according to Pt.4 Ch.12Sec.2 B101 is to be provided.

J 200 Power actuating system, general requirements201 Rudder actuators other than those covered by the IMOGuidelines for non-duplicated rudder actuators, see Appen-dix A, are to be designed in accordance with the relevant re-quirements of Pt.4 Ch.7 for Class I pressure vessels(notwithstanding any exemptions for hydraulic cylinders).202 Accumulators, if fitted, are to comply with the relevantrequirements of Pt.4 Ch.7.203 The welding details and welding procedures are to beapproved. All welded joints within the pressure boundary of arudder actuator or connecting parts transmitting mechanicalloads are to be full penetration type or of equivalent strength.204 The construction is to be such as to minimise local con-centrations of stress.205 The design pressure for calculations to determine thescantlings of piping and other steering gear components sub-jected to internal hydraulic pressure shall be at least 1,25 timesthe maximum working pressure under the operational condi-tions specified in 102 b) taking into account any pressurewhich may exist in the low pressure side of the system. Fatiguecriteria may be applied for the design of piping and compo-nents, taking into account pulsating pressures due to dynamicloads (see Appendix A).206 The permissible primary general membrane stress sub-ject to 205 is not to exceed the lower of the following values:

b = specified minimum tensile strength of material at am-bient temperature

y = specified minimum yield stress or 0,2 per cent proofstress of the material, at ambient temperature.

bA------ or

yB------


DET NORSKE VERITAS

A and B are given by the following table:

207 Special consideration is to be given to the suitability ofany essential component which is not duplicated. Any such es-sential component shall, where appropriate, utilise anti-frictionbearings such as ball bearings, roller bearings or sleeve bear-ings which shall be permanently lubricated or provided withlubrication fittings.208 All steering gear components transmitting mechanicalforces to the rudder stock, which are not protected againstoverload by structural rudder stops or mechanical buffers, areto have a strength at least equivalent to that of the rule rudderstock in way of the tiller.209 Oil seals between non-moving parts, forming part of theexternal pressure boundary, should be of the metal upon metaltype or of an equivalent type.210 Oil seals between moving parts, forming part of the ex-ternal pressure boundary, should be duplicated, so that the fail-ure of one seal does not render the actuator inoperative.Alternative arrangements providing equivalent protectionagainst leakage may be accepted.211 Hydraulic power operated steering gears are to be pro-vided with:

a) arrangements to maintain the cleanliness of the hydraulicfluid taking into consideration the type and design of thehydraulic system

b) a fixed storage tank having sufficient capacity to rechargeat least one power actuating system including the reser-voir, where the main steering gear is required to be poweroperated. The storage tank is to be permanently connectedby piping in such a manner that the hydraulic systems canbe readily recharged from a position within the steeringgear compartment and provided with a contents gauge.

212 Hydraulic power supply for steering gear is not to beused for other purposes.

J 300 Piping systems, relief valve arrangements301 Piping, joints, valves, flanges and other fittings are tocomply with the requirements of Pt.4 Ch.6. Power piping is tocomply with requirements to class I pipes. The design pressureis to be in accordance with 205.302 For all vessels with non-duplicated actuators, isolatingvalves, directly fitted on the actuator, are to be provided at theconnection of pipes to the actuator.303 Main and auxiliary steering gear are to be provided withseparate hydraulic power supply pipes. When main steeringgear is arranged in accordance with 104, each hydraulic powerunit is to be provided with separate power pipes. Interconnec-tions between power pipes are to be provided with quick oper-ating isolating valves.304 Arrangements for bleeding air fr

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