DNV Ship rules Pt.5 Ch.1 - Ships for Navigation in Ice

RULES FORCLASSIFICATION OF

SHIPS

NEWBUILDINGS

SPECIAL SERVICE AND TYPEADDITIONAL CLASS

PART 5 CHAPTER 1

SHIPS FOR NAVIGATION IN ICEJANUARY 2003

CONTENTS PAGE

Sec. 1 General Requirements ................................................................................................................ 5Sec. 2 Basic Ice Strengthening.............................................................................................................. 6Sec. 3 Ice Strengthening for the Northern Baltic .................................................................................. 8Sec. 4 Vessels for Arctic and Ice Breaking Service ........................................................................... 19Sec. 5 Sealers ..................................................................................................................................... 37

This is a re-print with the relevant amendments and corrections, shown in the current Pt.0 Ch.1 Sec.3, inserted into the body of the text.

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Veritasveien 1, N-1322 Høvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11

CHANGES IN THE RULES

General

The present edition of the rules includes additions and amendmentsdecided by the Board in March 2003 and supersedes the January 2001edition of the same chapter.

The rule changes come into force 1 July 2003.

This chapter is valid until superseded by a revised chapter. Supple-ments will not be issued except for minor amendments and an updatedlist of corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 is normallyrevised in January and July each year.

Revised chapters will be forwarded to all subscribers to the rules.Buyers of reprints are advised to check the updated list of rule chap-ters printed in Pt.0 Ch.1 Sec.1 to ensure that the chapter is current.

Main changes

• Sec.3 Ice Strengthening for the Northern Baltic

— Implements the new Finnish-Swedish Ice Class Rules, publishedin Bulletin No. 13/1.10.2002 from the Finnish Maritime Admin-istration (FMA).

— The new Finnish-Swedish Ice Class Rules entered into force on1 October 2002 and will be applied to ships of which the keel islaid or which is at similar stage of construction on or after 1 Sep-tember 2003.

— The new rules contain new minimum output requirements forpropulsion for the Ice Classes: ICE-1C and ICE-1B based onship’s resistance in channels with brash ice, which was intro-duced in the 2001 rules for Ice Classes ICE-1A and ICE-1A*,and which have now been amended. The amendments include,amongst others, validity ranges for certain “ship parameters”used in the calculation of ice resistance.

— FMA’s requirement in their Bulletin No. 16/27.11.2002 give the“minimum engine output” in the Class Certificate, this has alsobeen included into these rules.

— Structural strength requirements have also been amended, result-ing in a slightly thicker ice belt for longitudinally framed ships.

— In addition, DNV have included an amendment where framesperpendicular to the shell, which are of unsymmetrical profiles,are to have tripping preventions at a distance not exceeding 2.6meters (not included in FMA amendments).

— Item J304 has been amended to take into account the differencein the “material factor” between stainless steel and other materi-als.

Corrections and Clarifications

In addition to the above stated rule requirements, a number of detect-ed errors, corrections and clarifications have been made in the exist-ing rule text.

Comments to the rules may be sent by e-mail to [email protected] subscription orders or information about subscription terms, please use [email protected] information about DNV and the Society's services is found at the Web site http://www.dnv.com

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Rules for Ships, January 2003 Pt.5 Ch.1 Contents –

CONTENTS

SEC. 1 GENERAL REQUIREMENTS .......................... 5

A. Classification..........................................................................5A 100 Application........................................................................5A 200 Class notations ..................................................................5

B. Definitions ..............................................................................5B 100 Symbols.............................................................................5B 200 Terms ................................................................................5

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

SEC. 2 BASIC ICE STRENGTHENING ....................... 6

A. General...................................................................................6A 100 Classification.....................................................................6

B. Hull Arrangement and Scantlings .......................................6B 100 Shell plating ......................................................................6B 200 Ordinary frames ................................................................6B 300 Intermediate ice frames.....................................................6B 400 Ice stringer.........................................................................6B 500 Weld connections..............................................................6B 600 Sternframe and rudder ......................................................6

C. Machinery..............................................................................7C 100 Output of propulsion machinery .......................................7C 200 Design of propeller and propeller shaft ............................7C 300 Sea suctions and discharges ..............................................7

SEC. 3 ICE STRENGTHENING FOR THE NORTHERN BALTIC ......................................... 8

A. General...................................................................................8A 100 Classification.....................................................................8A 200 Assumptions......................................................................8A 300 Definitions.........................................................................8A 400 Documentation ..................................................................8

B. Design Loads .........................................................................9B 100 Height of load area............................................................9B 200 Ice pressure .......................................................................9

C. Shell Plating ...........................................................................9C 100 Vertical extension of ice strengthening.............................9C 200 Plate thickness in the ice belt ..........................................10

D. Frames..................................................................................10D 100 Vertical extension of ice framing....................................10D 200 Transverse frames ...........................................................10D 300 Longitudinal frames ........................................................11D 400 Structural details .............................................................11

E. Ice Stringers ........................................................................12E 100 Stringers within the ice belt ............................................12E 200 Stringers outside the ice belt ...........................................12E 300 Deck strips ......................................................................12

F. Web Frames........................................................................12F 100 Design load .....................................................................12F 200 Section modulus and shear area ......................................12

G. Bilge Keels............................................................................13G 100 Arrangement....................................................................13

H. Special Arrangement and Strengthening Forward..........13H 100 Stem, baltic ice strengthening .........................................13H 200 Arrangements for towing ................................................13

I. Special Arrangement and Strengthening Aft ...................14I 100 Stern ................................................................................14I 200 Rudder and steering arrangements .................................14

J. Machinery............................................................................14J 100 Engine output ..................................................................14J 200 Design loads for propeller and shafting ..........................16

J 300 Propeller ..........................................................................16J 400 Shafting ...........................................................................17J 500 Thrust bearing and reduction gear .................................17J 600 Miscellaneous machinery requirements..........................18

SEC. 4 VESSELS FOR ARCTIC AND ICE BREAKING SERVICE ........................................................... 19

A. General ................................................................................ 19A 100 Classification ..................................................................19A 200 Scope...............................................................................19A 300 Design principles and assumptions.................................19A 400 Definitions.......................................................................20A 500 Documentation................................................................21

B. Materials and Corrosion Protection................................. 22B 100 Design temperatures........................................................22B 200 Structural categories........................................................23B 300 Selection of steel grades..................................................23B 400 Coatings ..........................................................................24B 500 Corrosion additions.........................................................24B 600 Equipment .......................................................................24

C. Ship Design and Arrangement.......................................... 24C 100 Hull form.........................................................................24C 200 Appendages.....................................................................24C 300 Mooring equipment.........................................................24

D. Design Loads ...................................................................... 24D 100 Ice impact forces on the bow ..........................................24D 200 Beaching forces...............................................................25D 300 Ice compression loads amidships....................................25D 400 Local ice pressure ...........................................................25D 500 Accelerations...................................................................26

E. Global Strength .................................................................. 26E 100 General ............................................................................26E 200 Longitudinal strength ......................................................26E 300 Transverse strength amidships........................................27E 400 Overall strength of substructure in the foreship..............27

F. Local Strength .................................................................... 28F 100 General ............................................................................28F 200 Plating .............................................................................28F 300 Longitudinal stiffeners ....................................................28F 400 Other stiffeners................................................................29F 500 Girders ............................................................................29

G. Rudders, Propeller Nozzles and Steering Gears ............. 30G 100 General ............................................................................30G 200 Ice loads on rudders ........................................................30G 300 Rudder scantlings............................................................31G 400 Ice loads on propeller nozzles.........................................31G 500 Propeller nozzle scantlings .............................................31G 600 Steering gear ...................................................................31

H. Welding ............................................................................... 31H 100 General ............................................................................31H 200 External welding .............................................................31H 300 Fillet welds and penetration welds subject to

high stresses ....................................................................31

I. Machinery Systems ............................................................ 32I 100 Pneumatic starting arrangement......................................32I 200 Sea inlets and discharges ................................................32I 300 Sea cooling water arrangements .....................................32I 400 Ballast system .................................................................32

J. Propulsion Machinery and Propellers ............................. 32J 100 General ............................................................................32J 200 Engine output ..................................................................32J 300 Determination of ice torque ............................................33J 400 Propeller ..........................................................................33J 500 Shafting ...........................................................................33J 600 Thrust bearing .................................................................34J 700 Reduction gear ...............................................................34

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Rules for Ships, January 2003Pt.5 Ch.1 Contents –

J 800 Flexible couplings and clutches ......................................34J 900 Fixed shaft couplings ......................................................35J 1000 Propeller fitting ...............................................................35J 1100 Spare parts.......................................................................35

K. Thrusters ............................................................................. 35K 100 General ............................................................................35K 200 Shafting ...........................................................................35K 300 Reduction gear ................................................................35K 400 Propeller ..........................................................................35

L. Stability and Watertight Integrity ................................... 35L 100 Application......................................................................35L 200 Definitions.......................................................................35L 300 Documentation ................................................................35L 400 Requirements for intact stability .....................................35L 500 Requirements for damage stability .................................36L 600 Requirements for beaching stability ...............................36L 700 Requirements to watertight integrity...............................36

SEC. 5 SEALERS .......................................................... 37

A. General.................................................................................37A 100 Classification...................................................................37A 200 Hull form.........................................................................37

B. Strength of Hull and Superstructures...............................37B 100 Ship's sides and stem.......................................................37B 200 Superstructures................................................................37

C. Sternframe, Rudder and Steering Gear ...........................37C 100 Design rudder force.........................................................37C 200 Protection of rudder and propeller ..................................37

D. Anchoring and Mooring Equipment.................................37D 100 General ............................................................................37

E. Machinery............................................................................37E 100 Output of propulsion machinery .....................................37E 200 Thrust bearing, reduction gear, shafting and propeller ...37E 300 Machinery systems..........................................................37

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Rules for Ships, January 2003 Pt.5 Ch.1 Sec.1 –

SECTION 1GENERAL REQUIREMENTS

A. Classification

A 100 Application101 The rules in this chapter apply to vessels occasionally orprimarily intended for navigation in waters with ice conditions.The requirements are to be regarded as supplementary to thosegiven for the assignment of main class.

A 200 Class notations201 Vessels complying with relevant additional require-ments of this chapter will be assigned one of the followingclass notations:

B. Definitions

B 100 Symbols101 General

L = rule length in m *)B = rule breadth in m *)D = rule depth in m *)T = rule draught in m *)∆ = rule displacement in t *)CB = block coefficient *)∆f = displacement in t in fresh water (density 1.0 t/m3) at ice

class draught

Ps = maximum continuous output of propulsion machineryin kW

s = stiffener spacing in m measured along the plating be-tween ordinary and/or intermediate stiffeners

s0 = spacing in m of ordinary main framesss = 0.48 + 0.002 L

(m) maximum 0.61 m forward of the collision bulk-head and abaft the afterpeak bulkhead

l = stiffener span in m measured along the top flange ofthe member. For definition of span point, see Pt.3 Ch.1Sec.3 C100

S = girder span in m. For definition of span point, see Pt.3Ch.1 Sec.3 C100.

σF = minimum upper yield stress of material in N/mm2

NV-NS-steel may be taken as having σF = 235 N/mm2

g0 = standard acceleration of gravity (≈ 9.81 m / s2).

*) For details see Pt.3 Ch.1.

B 200 Terms

201 Load waterline, LWL:

The waterline corresponding to winter load line. For shipstrading in the Baltic during winter at summer load line, the icestrengthening is to be based on the summer load line, see alsoSec.3 A300.

202 Ballast waterline, BWL:

To be determined in such a way that the propeller, if possible,is completely submerged, see also Sec.3 A300.

C. Documentation

C 100 General

101 Details related to additional classes regarding design, ar-rangement and strength are in general to be included in theplans specified for the main class.

102 Additional documentation not covered by the main classare specified in appropriate sections of this chapter.

Table A1 Class notationsNotation ReferenceICE-C (See Sec.2)ICE-1A*F ICE-1A* ICE-1A ICE-1B ICE-1C

(See Sec.3)

ICE - 05(or - 10 or - 15)POLAR - 10(or - 20 or - 30)Icebreaker

(See Sec.4)

Sealer (See Sec.5)

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Rules for Ships, January 2003Pt.5 Ch.1 Sec.2 –

SECTION 2BASIC ICE STRENGTHENING

A. General

A 100 Classification

101 The requirements in this section apply to passenger andcargo vessels intended for service in waters with light ice con-ditions.

102 Vessels built in compliance with the following require-ments may be given the class notation ICE-C.

103 In cases where the structural requirements of Sec.3(ICE-1C) give smaller scantlings than Sec.2, Sec.3 may be ap-plied.

104 Vessels with longitudinal framing are to have scantlingsfor plating and longitudinals as for class notation ICE-1C, us-ing 0.9 times the ice pressure as given in Sec.3. The extent ofice strengthening is to be as specified in B100 and B300.

B. Hull Arrangement and Scantlings

B 100 Shell plating

101 From stem to a distance B abaft F.P. and within a belt ex-tending vertically from 0.5 m above LWL to 0.5 m belowBWL, the shell plating thickness is not to be less than:

t = 6 + 0.11 L + ∆ t (mm), maximum 25 mm

∆ t = 20 (so − ss) (mm), minimum zero.

102 Abaft the area mentioned in 101, the shell plating thick-ness within the specified ice belt may be gradually reduced tonormal thickness at the position where the waterlines attaintheir full breadth.

B 200 Ordinary frames

201 Ordinary frames in fore peak are to have a section mod-ulus not less than:

Z = 0.25 L T (cm3)

The distance between ordinary frames in fore peak is not to ex-ceed 0.61 m.

202 From collision bulkhead to 1.5 B abaft F.P., the sectionmodulus of ordinary main frames is not to be less than:

Z = 0.4 L so T (cm3)

B 300 Intermediate ice frames

301 In the region from stem to 1.5 B abaft F.P., intermediateframes are to be fitted. The intermediate ice frames are to ex-tend from 0.62 m above LWL to 1.0 m below BWL.

Bottom plating forward situated less than 0.5 m below BWL isto have intermediate stiffening between floors. Intermediateice frames may be omitted, if the spacing of the ordinaryframes is not exceeding:

— 0.37 m forward of collision bulkhead— (0.288 + 0.0012 L), maximum 0.42 m abaft collision bulk-

head.

302 The intermediate ice frames are to have a section modu-lus not less than:

— forward of collision bulkhead:

— abaft collision bulkhead:

The required section modulus of intermediate frames forwardof the collision bulkhead is based on a frame span equal to 2 m.For different spans, the requirement is modified in direct pro-portion. Intermediate frames need in no case have a sectionmodulus larger than 75% of that of the ordinary frames.

303 The ends of intermediate ice frames are to be connectedto horizontal carlings between ordinary frames. These carlingsare not to form a continuous stringer. Where intermediate iceframes extend to a deck or inner bottom, it may have snipedends. Acceptable types of intermediate frame ends are shownin Fig. 1.

Fig. 1Acceptable types of intermediate frame ends

B 400 Ice stringer

401 In single deck ships, an ice stringer is to be fitted 0.2 to0.3 m below LWL from stem to a distance 2 B abaft F.P.

Forward of the collision bulkhead, the ice stringer is to be agirder with scantlings as an ordinary girder on the ship's side.Abaft the collision bulkhead, the ice stringer is to consist of aseries of tripping brackets fitted to the frames.

B 500 Weld connections

501 Weld connections to shell in fore peak are to be doublecontinuous.

B 600 Sternframe and rudder

601 The section modulus of sternframe, rudder horn and solepiece is to be 7.5% greater than required for the main class.

602 Scantlings of rudders, rudder stocks and rudder shaftsare to be based on a rudder force 25% greater than a design val-ue calculated according to Pt.3 Ch.3 Sec.2 D101, with k1 = k2= 1.0 irrespective of condition, rudder profile type and arrange-ment.

ZL

2

160--------- 10+

=

so

ss---- (cm

3 )

ZL

2

100--------- 20+

=

so

ss---- (cm

3 )

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C. Machinery

C 100 Output of propulsion machinery

101 The maximum continuous output is generally not to beless than:

Ps = 0.73 L B (kW)

For ships with a bow specially designed for navigation in ice,a reduced output may be accepted. In any case, the output is notto be less than:

Ps = 0.59 L B (kW)

102 If the ship is fitted with a controllable pitch propeller, theoutput may be reduced by 10%.

103 For ships with steam turbines, the astern power is not tobe less than 70% of the forward power.

C 200 Design of propeller and propeller shaft

201 Relevant criteria in Sec.3 are to be applied, assuming theice torque in Nm:

TICE= 35 200 R2 for open propellers

TICE= 35 200 R2 (0.9 − 0.0622 R-0.5) for ducted propellers

R = propeller radius (m).

202 The propeller shaft diameter need not exceed 1.05 timesthe rule diameter given for main class, irrespective of the di-mension derived from Sec.3.

C 300 Sea suctions and discharges301 The sea cooling water inlet and discharge for main andauxiliary engines are to be so arranged so that blockage ofstrums and strainers by ice is prevented. In addition to require-ments in Pt.4 Ch.1 and Ch.6 the requirements in 302 and 303are to be complied with.

302 One of the sea cooling water inlet sea chests is to be sit-uated near the centre line of the ship and well aft. At least oneof the sea chests is to be sufficiently high to allow ice to accu-mulate above the pump suctions.

303 A full capacity discharge branched off from the coolingwater overboard discharge line is to be connected to at leastone of the sea inlet chests. At least one of the fire pumps is tobe connected to this sea chest or to another sea chest with de-icing arrangements.

Guidance note:Heating coils may be installed in the upper part of the seachest(s). Arrangement using ballast water for cooling purposes isrecommended but will not be accepted as a substitute for sea inletchest arrangement as described above.

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

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SECTION 3ICE STRENGTHENING FOR THE NORTHERN BALTIC

A. General

A 100 Classification

101 The requirements in this section apply to vessels forservice in the northern Baltic in winter or areas with similar iceconditions.

102 Vessels built in compliance with the following require-ments may be given one of the class notations ICE-1A*, ICE-1A, ICE-1B or ICE-1C whichever is relevant.

Guidance note:The ice class requirements are considered to meet the Finnish-Swedish Ice Class Rules 01 October 2002 for correspondingclasses.

Revision of these rules concern propulsion power and structuralstrength and applies to ships of which the keel is laid, or which isat a similar stage of construction on or after 1 September 2003.


103 Vessels built in compliance with the requirements rele-vant for class ICE-1A* and with the additional requirementsgiven below may acquire the class notation ICE-1A*F.

Guidance note:The additional ice class ICE-1A*F is recommended applied tovessels with relatively high engine power designed for regulartraffic in the northern Baltic and other relevant areas, normallyoperating according to rather fixed timetables irrespective of iceconditions and to a certain degree independent of ice breaker as-sistance.


A 200 Assumptions

201 The method for determining the hull scantlings is basedon certain assumptions concerning the nature of the ice load onthe structure. These assumptions rest on full scale observationsmade in the northern Baltic.

202 The formulae given for plating, stiffeners and girders arebased on special investigations as to the distribution of iceloads from plating to stiffeners and girders as well as redistri-bution of loads on stiffeners and girders. Special values havebeen given for distribution factors and certain assumptionshave been made regarding boundary conditions.

203 For the formulae and values given in this section for thedetermination of the hull scantlings more sophisticated meth-ods may be substituted subject to special approval.

204 If scantlings derived from these regulations are less thanthose required for an unstrengthened ship, the latter shall beused.

205 The frame spacing and spans defined in the followingtext are normally assumed to be measured in a vertical planeparallel to the centreline of the ship. However, if the ship’s sidedeviates more than 20° from this plane, the frame distances andspans shall be measured along the side of the ship.

206 Assistance from icebreakers is normally assumed whennavigating in ice bound waters.

A 300 Definitions

301 Maximum draught amidships

The maximum ice class draught amidships shall be the draughton the Fresh Water Load Line in Summer. If the ship has a tim-ber load line, the Fresh Water Timber Load Line in Summershall be used.

302 Maximum and minimum draught fore and aft

The maximum and minimum ice class draughts fore and aftshall be determined and stated in the classification certificate.

The line defined by the maximum draughts fore, amidshipsand aft will henceforth be referred to as LWL. The line may bea broken line. The line defined by the minimum draughts foreand aft will be referred to as BWL.

The draught and trim, limited by the LWL, must not be exceed-ed when the ship is navigating in ice. The salinity of the seawater along the intended route is to be taken into account whenloading the ship. Filling of ballast tanks may be necessary toload the ship to the BWL. Any ballast tanks situated fully orpartly above the BWL adjacent to the ship's shell are to beequipped with anti-freezing device(s) to prevent the waterfrom freezing, see J603. In determining the BWL, regard shallbe paid to the need for ensuring a reasonable degree of ice go-ing capability in ballast. The propeller shall be fully sub-merged, if possible entirely below the ice. The minimumforward draught shall be at least:

(2 + 0.00025 ∆f) ho (m)

but need not exceed 4 ho where

∆f = displacement of the ship (t) on the maximum ice classdraught according to 301

ho = ice thickness according to B101.

303 Ice belt regions

The ice belt is divided into regions as follows (see also Fig.1):

Forward region: From the stem to a line parallel to and 0.04 Laft of the forward borderline of the part of the hull where thewaterlines run parallel to the centre line. For ice classes ICE-1A*F, ICE-1A* and ICE-1A the overlap of the borderlineneed not exceed 6 m, for ice classes ICE-1B and ICE-1C thisoverlap need not exceed 5 m.

Midship region: From the aft boundary of the Forward regionto a line parallel to and 0.04 L aft of the aft borderline of thepart of the hull where the waterlines run parallel to the centreline. For ice classes ICE-1A*F, ICE-1A* and ICE-1A theoverlap of the borderline need not exceed 6 m, for ice classesICE-1B and ICE-1C this overlap need not exceed 5 m.

Aft region: From the aft boundary of the Midship region to thestern.

A 400 Documentation

401 LWL and BWL are to be indicated on the shell expan-sion plan together with the lines separating the forward, amid-ships and aft regions of the ice belt. The machinery,displacement, ∆f, and the output of propulsion machinery, Ps,are to be stated on the shell expansion and/or the framing plan.

DNV Ice Class notation Equivalent Finnish-Swedish Ice Class

ICE-1A* 1A SuperICE-1A 1AICE-1B 1BICE-1C 1C

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Fig. 1Ice belt regions

B. Design Loads

B 100 Height of load area101 An ice strengthened ship is assumed to operate in opensea conditions corresponding to a level ice thickness not ex-ceeding ho. The design height (h) of the area actually under icepressure at any particular point of time is, however, assumed tobe only a fraction of the ice thickness. The values for ho and hare given in the following table.

B 200 Ice pressure201 The design ice pressure (based on a nominal ice pressureof 5 600 kN/m2) is determined by the formula:

p = 5 600 cd c1 ca (kN/m2)

cd = a factor which takes account of the influence of the sizeand engine output of the ship. It is calculated by theformula:

a and b are given in Table B2.

∆f = displacement (t) as defined in A302Ps = machinery output (kW) as defined in J101c1 = a factor which takes account of the probability that the

design ice pressure occurs in a certain region of thehull for the ice class in question.

The value of c1 is given in Table B3:

For ice class ICE-1A*F an additional lower forward ice belt(see C102) is defined with factor c1 = 0.20.

ca = a factor which takes account of the probability that thefull length of the area under consideration will be un-der pressure at the same time. It is calculated by theformula:

la is to be taken as given in Table B4.

C. Shell Plating

C 100 Vertical extension of ice strengthening101 The vertical extension of the ice belt (see Fig.1) is not tobe less than given in Table C1.

102 In addition the following areas shall be strengthened:

Fore foot: For ice class ICE-1A* and ICE-1A*F the shell plat-ing below the ice belt from the stem to a position five mainframe spaces abaft the point where the bow profile departsfrom the keel line shall have at least the thickness required inthe ice belt in the midship region, calculated for the actualframe spacing.

Upper forward ice belt: For ice classes ICE-1A* and ICE-1Aon ships with an open water service speed equal to or exceed-ing 18 knots, the shell plate from the upper limit of the ice beltto 2 m above it and from the stem to a position at least 0.2 Labaft the forward perpendicular, is to have at least the thick-ness required in the ice belt in the midship region, calculatedfor the actual frame spacing.

Guidance note:A similar strengthening of the bow region is advisable also for aship with a lower service speed, when it is, e.g. on the basis of themodel tests, evident that the ship will have a high bow wave.


For ice class ICE-1A*F the upper forward ice belt is to be tak-

Table B1 Values of ho and h Ice class ho (m) h (m)ICE-1A*ICE-1AICE-1BICE-1C

1.0 0.8 0.6 0.4

0.350.300.250.22

Table B2 Values of a and bRegion

Forward Midship and aftk ≤ 12 k > 12 k ≤ 12 k > 12

a 30 6 8 2b 230 518 214 286

cd ak b+1000

---------------=

k∆fPs

1000---------------=

Table B3 Values of c1

Ice classRegion

Forward Midship AftICE-1A* 1.0 1.0 0.75ICE-1A 1.0 0.85 0.65ICE-1B 1.0 0.70 0.45ICE-1C 1.0 0.50 0.25

Table B4 Values of laStructure Type of framing la

Shell transverse frame spacing

longitudinal 2 x frame spacing

Framestransverse frame spacing

longitudinal span of frameIce stringer span of stringerWeb frame 2 x web frame spacing

Table C1 Vertical extension of ice beltIce class Above LWL (m) Below BWL (m)ICE 1A*ICE 1AICE 1BICE 1C

0.60.50.40.4

0.750.60.50.5

ca

47 5la–

44------------------- , maximum 1.0, minimum 0.6=

DET NORSKE VERITAS


en 3 m above the normal ice belt, extending within the forwardregion.

Lower forward ice belt: For ice class ICE-1A*F a lower for-ward ice belt below the normal ice belt is defined covering theforward region aft of the forefoot and down to the lower turnof bilge.

103 Sidescuttles are not to be situated in the ice belt. If theweather deck in any part of the ship is situated below the upperlimit of the ice belt (e.g. in way of the well of a raised quarterdeck), the bulwark is to be given at least the same strength asis required for the shell in the ice belt. The strength of the con-struction of the freeing ports is to meet the same requirements.

C 200 Plate thickness in the ice belt201 For transverse framing the thickness of the shell platingis to be determined by the formula:

For longitudinal framing the thickness of the shell plating is tobe determined by the formula:

p PL = 0.75 pp = as given in B200.

x1 =

x2 =

= 1.4 − 0.4 (h/s); when 1 ≤ h/s < 1.8 = 0.35 + 0.183 (h/s) for 1.8 ≤ h/s < 3 = 0.9 for h/s > 3h = as given in B100σ F = yield stress of the material (N/mm2)tc = increment for abrasion and corrosion (mm); normally

2 mm. If a special surface coating, by experienceshown capable to withstand the abrasion of ice, is ap-plied and maintained, lower values may be approved.

202 For ice class ICE-1A*F the following additional re-quirements are given:

— bottom plating in the forward region (below the lower for-ward ice belt defined in 102) is to have a thickness not lessthan:

— side and bottom plating in the aft region below the ice beltis to have a thickness not less than:

D. Frames

D 100 Vertical extension of ice framing

101 The vertical extension of the ice strengthening of theframing is to be at least as given in Table D1:

Where an upper forward ice belt is required (see C102), the icestrengthened part of the framing is to be extended at least to thetop of this ice belt.

102 Where the ice strengthening would go beyond a deck ora tank top by not more than 250 mm, it can be terminated atthat deck or tank top.

D 200 Transverse frames

201 The section modulus of a main or intermediate trans-verse frame is to be calculated by the formula:

p = ice pressure as given in B200h = height of load area as given in B100

mt =

mo = values as given in Table D2.

t 21.1sx1 p PL

σ F------------------ tc (mm)+=

t 21.1sp PL

x2σF

------------ tc (mm)+=

1.3 4.2

h s⁄ 1.8+( )2---------------------------------– , maximum 1.0

0.60.4h s⁄( )

---------------- , when h/s 1≤+

t 0.7 s 0.8+( ) 235Lσ F

------------- (mm), minimum 12 mm=

Table D1 Vertical extension of ice strengthening of the framingIce class Region Above LWL

(m)Below BWL

(m)

ICE- 1A*Fforward 1.2

to double bot-tom or below top of floors

midship 1.2 1.6aft 1.2 1.2

ICE-1A*

from stem to 0.3 L abaft it 1.2

to double bot-tom or below top of floors

abaft 0.3 L from stem 1.2 1.6

midship 1.2 1.6aft 1.2 1.2

ICE-1A, 1B, 1C

from stem to 0.3 L abaft it 1.0 1.6

abaft 0.3 L from stem 1.0 1.3

midship 1.0 1.3aft 1.0 1.0

t 0.6 s 0.8+( ) 235Lσ F

------------- (mm), minimum 10 mm=

Zp s h lmtσ F---------------10

3 cm

3( )=

7mo

7 5h l⁄–------------------------

DET NORSKE VERITAS


The boundary conditions are those for the main and intermedi-ate frames. Possible different conditions for main and interme-diate frames are assumed to be taken care of by interactionbetween the frames and may be calculated as mean values.Load is applied at mid span.

If the ice belt covers less than half the span of a transverseframe, (b < 0.5 l) the following modified formula may be usedfor the section modulus:

b = distance in m between upper or lower boundary of theice belt and the nearest deck or stringer within the icebelt.

Where less than 15% of the span, l, of the frame is situatedwithin the ice-strengthening zone for frames as defined inD101, ordinary frame scantlings may be used.

202 Upper end of transverse framing

1) The upper end of the strengthened part of a main frame andof an intermediate ice frame is to be attached to a deck oran ice stringer (see E).

2) Where an intermediate frame terminates above a deck oran ice stringer which is situated at or above the upper limitof the ice belt (see C100) the part above the deck or string-

er may have the scantlings required for an unstrengthenedship and the upper end be connected to the adjacent mainframes by a horizontal member of the same scantlings asthe main frame. Such an intermediate frame can also beextended to the deck above and if this is situated more than1.8 metre above the ice belt the intermediate frame neednot be attached to that deck, except in the Forward region.

203 Lower end of transverse framing

1) The lower end of the strengthened part of a main frame andof an intermediate ice frame is to be attached to a deck,tank top or ice stringer (see E).

2) Where an intermediate frame terminates below a deck,tank top or ice stringer which is situated at or below thelower limit of the ice belt (see C100), the lower end to beconnected to the adjacent main frames by a horizontalmember of the same scantlings as the frames.

D 300 Longitudinal frames301 The section modulus of a longitudinal frame is to be cal-culated by the formula:

The shear area of a longitudinal frame is to be:

These formulae assume that the longitudinal frame is attachedto supporting structure by brackets as required in 401.

x3 = factor which takes account of the load distribution toadjacent frames:

x3 = (1 − 0.2 h/s)

x4 = factor which takes account of the concentration of loadto the point of support:

x4 = 0.6

p = ice pressure as given in B200h = height of load area as given in B100m1 = boundary condition factor; m1= 13.3 for a continuous

beam. Where the boundary conditions deviate signifi-cantly from a continuous beam, a smaller factor maybe required.

Normally m1 = 12 is to be used for longitudinals, tak-ing into account load variations between adjacentspans.

D 400 Structural details401 Within the ice strengthened area all frames are to be ef-fectively attached to all supporting structures by brackets.Frames crossing supporting structures such as web frames orstringers are to be connected to these structures on both sides(by collar plates or lugs in way of cut-outs).

402 For ice class ICE-1A*F and ICE-1A*, for ice class ICE-1A in the forward and midship regions and for ice classes ICE-1B and ICE-1C in the forward region, the following shall ap-ply in the ice strengthened area:

1) Frames which are not at a straight angle to the shell are tobe supported against tripping by brackets, intercostals,stringers or similar at a distance preferably not exceeding1.3 m.Frames perpendicular to shell which are of unsymmetricalprofiles are to have tripping preventions at a distance notexceeding 2.6 m.

Table D2 Values of mo

Boundary condi-tion

mo Example

7 Frames in a bulk carrier with top wing tanks

6 Frames extending from the tank top to a single deck

5.7 Continuous frames between several decks or stringers

5 Frames extending between two decks only

Zps h b l b–( )2

σF l2

---------------------------------- 103 cm

3( )=

Zx3 x4 p h l

2

m1σF-------------------------- 10

3 cm

3( )=

A8.7 x3p h l

σF------------------------- cm

2( )=

DET NORSKE VERITAS


2) Frames and girder webs are to be attached to the shell bydouble continuous welds. No scalloping is allowed (ex-cept when crossing shell plate butts).

3) The web thickness of the frames is to be at least one halfof the thickness of the shell plating and at least 9 mm.Where there is a deck, tank top or bulkhead in lieu of aframe the plate thickness of this is to be as above, to adepth corresponding to the height of adjacent frames.

E. Ice Stringers

E 100 Stringers within the ice belt101 The section modulus of a stringer situated within the icebelt (see C100) is to be calculated by the formula:

The shear area is not to be less than:


The product p h is not to be taken as less than 300l = span of stringer (m)m1 = boundary condition factor as given in D301.

E 200 Stringers outside the ice belt201 The section modulus of a stringer situated outside the icebelt but supporting ice strengthened frames is to be calculatedby the formula:

The shear area is not to be less than:


The product p h is not to be taken as less than 300.

l = span of stringer (m)m1 = boundary condition factor as given in D301 ls = the distance to the adjacent ice stringer(m)hs = the distance to the ice belt (m).

E 300 Deck strips301 Narrow deck strips abreast of hatches and serving as icestringers are to comply with the section modulus and shear arearequirements in 100 and 200 respectively. In the case of verylong hatches the lower limit of the product p h may be reducedto 200.

302 Regard shall be paid to the deflection of the ship's sidesdue to ice pressure in way of very long hatch openings, whendesigning weatherdeck hatch covers and their fittings.

F. Web Frames

F 100 Design load

101 The load transferred to a web frame from an ice stringeror from longitudinal framing shall be calculated by the formu-la:

F = p h s (kN)

p = ice pressure as given in B200, when calculating factorca, however, la is to be taken as 2 s

h = height in m of load area as given in B100

The product ph is not to be taken less than 300.

s = web frame spacing in m

In case the supported stringer is outside the ice belt, the load Fmay be multiplied by:

as given in E201.

Fig. 2Web frame

F 200 Section modulus and shear area

201 For a web frame simply supported at the upper end andfixed at the lower end (see Fig.2), the section modulus require-ment is given by:

M = maximum calculated bending moment under the loadF, as given in 101

γ = as given in Table F1A = required shear area from 202Aa = actual cross sectional area of web plate.

202 With boundary conditions as given in 201, the shear areaof a web frame is given by:

Q = maximum calculated shear force under the load F, asgiven in 101

α = factor given in Table F1Af = cross sectional area of free flangeAw = cross sectional area of web plate.

Z0.9 p h l

2

m1σ F--------------------- 10

3 cm

3( )=

A7.8 p h l

σ F------------------- cm

2( )=

Z0.95 p h l

2

m1σ F------------------------ 1

hs

ls-----–

10

3 cm

3( )=

A8.2 p h l

σ F------------------- 1

hs

ls-----–

cm

2( )=

1hs

ls-----–

ZMσF------ 1

1 γ AAa------

2

–

--------------------------103 (cm

3 )=

A17.3α Q

σF-------------------- (cm

2 )=

DET NORSKE VERITAS


203 For other web frame configurations and boundary con-ditions than given in 201, a direct stress calculation should beperformed.

The concentrated load on the web frame is given in 101.

The point of application is in each case to be chosen in relationto the arrangement of stringers and longitudinal frames so as toobtain the maximum shear and bending moments.

Allowable stresses are as follows:

— shear stress:

— bending stress:

— equivalent stress:

G. Bilge Keels

G 100 Arrangement

101 The connection of bilge keels to the hull are to be so de-signed that the risk of damage to the hull, in case a bilge keelis ripped off, is minimised.

102 To limit damage when a bilge keel is partly ripped off, itis recommended that bilge keels are cut up into several shorterindependent lengths.

103 For class ICE-1A*F bilge keels are normally to beavoided and should be replaced by roll-damping equipment.Specially strengthened bilge keels may be considered.

H. Special Arrangement and Strengthening For-ward

H 100 Stem, baltic ice strengthening

101 The stem may be made of rolled, cast or forged steel orof shaped steel plates. A sharp edged stem (see Fig.3) improvesthe manoeuvrability of the ship in ice and is recommended par-ticularly for smaller ships with length less than 150 m.

Fig. 3Welded stem

102 The plate thickness of a shaped plate stem and in thecase of a blunt bow, any part of the shell which forms an angleof 30° or more to the centre line in a horizontal plane, is to becalculated according to the formulae in C200 assuming that:

s = spacing of elements supporting the plate (m)pPL = p (see B200).

la = spacing of vertical supporting elements (m).

For class ICE-1A*F the front plate and upper part of the bulband the stem plate up to a point 3.6 m above LWL (lower partof bow door included) is to have a minimum thickness of:

c = 2.3 for the stem plate = 1.8 for the bulb plating.

The width of the increased bulb plate is not to be less than 0.2b on each side of the centre line, b being the breadth of the bulbat F.P.

103 The stem and the part of a blunt bow defined above areto be supported by floors or brackets spaced not more than 0.6m apart and having a thickness of at least half the plate thick-ness. The reinforcement of the stem is to be extend from thekeel to a point 0.75 m above LWL or, in case an upper forwardice belt is required (C102) to the upper limit of this.

H 200 Arrangements for towing

201 A mooring pipe with an opening not less than 250 by300 mm, a length of at least 150 mm and an inner surface radi-us of at least 100 mm is to be fitted in the bow bulwark at thecentre line.

202 A bitt or other means for securing a towline, dimen-sioned to stand the breaking force of the towline of the ship isto be fitted.

203 On ships with a displacement not exceeding 30 000 tonsthe part of the bow which extends to a height of at least 5 mabove the LWL and at least 3 m aft of the stem, is to bestrengthened to take the stresses caused by fork towing. Forthis purpose intermediate frames are to be fitted and the fram-ing shall be supported by stringers or decks.

204 It shall be noted that for ships of moderate size (displace-ment not exceeding 30 000 tons) fork towing in many situa-tions is the most efficient way of assisting in ice. Ships with abulb protruding more than 2.5 m forward of the forward per-pendicular are often difficult to tow in this way. The adminis-trations reserve the right to deny assistance to such ships if thesituation so warrants.

τ σF 3⁄=

σb σF=

σc σb2

3τ2+ σF= =

Table F1 Values of α and γ

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

α 1.5 1.23 1.16 1.11 1.09 1.07 1.06 1.05 1.05 1.04 1.04

γ 0 0.44 0.62 0.71 0.76 0.80 0.83 0.85 0.87 0.88 0.89

Af

Aw--------

t c 235Lσf

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

DET NORSKE VERITAS


I. Special Arrangement and Strengthening Aft

I 100 Stern

101 The introduction of new propulsion arrangements withazimuthing thrusters or “podded” propellers, which provide animproved manoeuvrability, will result in increased ice loadingof the aft region and stern area. This fact should be consideredin the design of the aft/stern structure.

102 An extremely narrow clearance between the propellerblade tip and the stern frame is to be avoided as a small clear-ance would cause very high loads on the blade tip.

103 On twin and triple screw ships the ice strengthening ofthe shell and framing is to be extended to the double bottom for1.5 metre forward and aft of the side propellers.

104 Shafting and stern tubes of side propellers are normallyto be enclosed within plated bossings. If detached struts areused, their design, strength and attachment to the hull are to beduly considered.

For class ICE-1A*F the skin plating of propeller shaft bossingsis not to be less than:

105 A wide transom stern extending below the LWL will se-riously impede the capability of the ship to run astern in ice,which is most essential. Therefore a transom stern is not to beextended below the LWL if this can be avoided. If unavoida-ble, the part of the transom below the LWL is to be kept as nar-row as possible. The part of a transom stern situated within theice belt is to be strengthened as for the midship region.

I 200 Rudder and steering arrangements

201 The scantlings of rudder, rudder post, rudder stock, pin-tles, steering gear etc. as well as the capacity of the steeringgear are to be determined according to the rules. The maximumservice speed of the ship to be used in these calculations is,however, not to be taken less than that stated below:

If the actual maximum service speed of the ship is higher, thatspeed is to be used.

When calculating the rudder force according to the formulagiven in Pt.3 Ch.3 Sec.2 D and with the speed V in ahead con-dition as given above, the factors k1 = k2 = 1.0 irrespective ofcondition, rudder profile type or arrangement. In the asterncondition half the speed values is to be used.

202 For the ice classes ICE-1A* and ICE-1A the rudderstock and the upper edge of the rudder is to be protectedagainst ice pressure by an ice knife or equivalent means.

Guidance note:

Upper forward part of rudder and forward part of rudder hornshould be protected against abrasion by a special coating or in-crease in thickness.


203 For ice classes ICE-1A* and ICE-1A due regard is to bepaid to the excessive loads caused by the rudder being forcedout of the midship position when backing into an ice ridge.

204 Relief valves for hydraulic pressure are to be effective.The components of the steering gear are to be dimensioned tostand the yield torque of the rudder stock. Where possible rud-der stoppers working on the blade or rudder head are to be fit-ted.

205 Parts of rudder within the ice belt are to have local thick-ness at least equivalent to the side shell in the afterbody.

J. Machinery

J 100 Engine output

101 Definition of engine output

The engine output PS is the maximum output the propulsionmachinery can continuously deliver to the propeller(s). If theoutput of the machinery is restricted by technical means or byany regulations applicable to the ship, PS shall be taken as therestricted output.

102 Documentation on board

Minimum engine output corresponding to the ice class shall begiven in the Classification Certificate.

103 Required engine output for ice classes

Definitions

The dimensions of the ship and some other parameters are de-fined below:

L = length of the ship between the perpendiculars (m)LBOW = length of the bow (m), Fig.4L PAR = length of the parallel midship body (m), Fig.4B = maximum breadth of the ship (m)T = actual ice class draughts of the ship (m) according to

A301A wf = area of the waterline of the bow (m2), Fig.4α = the angle of the waterline at B/4 (°), Fig.4ϕ1 = the rake of the stem at the centreline (°), Fig.4ϕ2 = the rake of the bow at B/4 (°), Fig.4DP = diameter of the propeller or outer diameter of nozzle

for the nozzle propeller, maximum 1.2 times propel-ler diameter (m)

HM = thickness of the brash ice in mid channel (m)HF = thickness of the brash ice layer displaced by the bow

(m).

Range of validity

The range of validity of the formulae for powering require-ments in 104 is presented in Table J1. When calculating the pa-rameter DP/T, T shall be measured at LWL.

If the ship’s parameter values are beyond the ranges defined inTable J1, other methods for determining RCH shall be used asdefined in 105.

Table I1 Maximum service speedIce class Maximum service speedICE-1A*ICE-1AICE-1BICE-1C

20 knots18 knots16 knots14 knots

t 0.9 s 0.8+( ) 235Lσf

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

Table J 1 Parameter validity rangeParameter Minimum Maximumα [degrees] 15 55ϕ1 [degrees] 25 90ϕ2 [degrees] 10 90L [m] 65.0 250.0B [m] 11.0 40.0T [m] 4.0 15.0LBOW/L 0.15 0.40LPAR/L 0.25 0.75DP /T 0.45 0.75Awf /(L*B) 0.09 0.27

DET NORSKE VERITAS


Fig. 4Definitions

104 The engine output requirement shall be calculated forfollowing two draughts:

— the maximum draught amidship referred to as LWL and— the minimum draught referred to as BWL, as defined in

A302.

In the calculations the ship's parameters which depend on thedraught are to be determined at the appropriate draught, but Land B are to be determined only at the LWL. The engine outputshall not be less than the greater of these two outputs.

The engine output PS shall not be less than that determined bythe formulae and in no case less than given in Table J3:

Guidance note:“New ships” – see A102 Guidance note.For “existing ICE-1A and ICE-1A* ships” see Pt.7 Ch.1 Sec.6 F.


RCH is the resistance in Newton of the ship in a channel withbrash ice and a consolidated layer:

Cµ = 0.15 cosϕ2 + sinψ sinα ≥ 0.45Cψ = 0.047ψ − 2.115 and 0 if ψ ≤ 45°HF = 0.26 + (HMB)0.5

HM = 1.0 for ICE-1A and ICE-1A*= 0.8 for ICE-1B= 0.6 for ICE-1C

C1 and C2 take into account a consolidated upper layer of thebrash ice and can be taken as zero for ice class ICE-1A, ICE-1B and ICE-1C.

For ice class ICE-1A*:

For a ship with a bulbous bow, ϕ1 shall be taken as 90°.

f1 = 23 (N/m2)f2 = 45.8 (N/m)f3 = 14.7 (N/m)f4 = 29 (N/m2)g1 = 1 530 (N)g2 = 170 (N/m)g3 = 400 (N/m1.5)C3 = 845 (kg/(m2s2))C4 = 42 (kg/(m2s2))C5 = 825 (kg/s2)

Table J2 Value of factor Ke

Propeller type or machinery

Numbers of propellers

Controllable pitch propeller or electric or hydraulic propulsion

machinery

Fixed pitch propeller

1 propeller 2.03 2.262 propellers 1.44 1.63 propellers 1.18 1.31

Table J3 Minimum engine output PS

ICE-1A, ICE-B and ICE-C 1 000 kWICE-1A* 2 800 kW

PS Ke

RCH

1000------------

DP-----------------

32---

(kW)=

RCH C1 C2 C3Cµ HF HM+( )2 B CψHF+( )

C4LPARHF2

C5LT

B2

------- 3Awf

L---------- (N)+

+ + +=

C1 f1

BLPAR

2TB---- 1+

-------------------- 1 0.021ϕ1+( ) f2B f3LBOW f4BLBOW+ +( )+=

C2 1 0.063ϕ1+( ) g1 g2B+( ) g3 1 1.2TB----+

B

2

L-------+=

ψ arctanϕ2tan

αsin--------------

=

The following shall apply: 20LT

B2

------- 3

5≥ ≥

DET NORSKE VERITAS


105 Other methods of determining Ke or RCH

For an individual ship, in lieu of the Ke or RCH values definedin Table J2 and 104, the use of Ke or RCH values based on moreexact calculations or values based on model tests may be ap-proved. Such approval will be given on the understanding thatit can be revoked if experience of the ship’s performance inpractice motivates this.

The design requirement for ice classes shall be a minimumspeed of 5 knots in the following brash ice channels (see TableJ4):

J 200 Design loads for propeller and shafting201 The formulae for scantlings are based on the followingloads:

To = mean torque of propulsion engine at maximum con-tinuous rating in Nm

(If multi-engine plant, To is the mean torque in anactual branch or after a common point. To is alwaysreferred to engine r.p.m.)

Tho = mean propeller thrust in N at maximum continuousspeed

R = as given in 301.Tice = ice torque in Nm (referred to propeller r.p.m.) and

found from Table J5.

J 300 Propeller301 The particulars governing the requirements for scant-lings are:

R = propeller radius (m)Hr = pitch in m at radius in questionθ = rake in degrees at blade tip (backward rake positive)Z = number of bladest = blade thickness in mm at cylindrical section consid-

eredt0.25 = t at 0.25 Rt0.35 = t at 0.35 Rt0.6 = t at 0.6 Rcr = blade width in m at cylindrical section consideredc0.25 = cr at 0.25 Rc0.35 = cr at 0.35 Rc0.6 = cr at 0.6 Ru = gear ratio:

If the shafting system is directly coupled to engine, u = 1.

no = propeller speed at maximum continuous output, forwhich the machinery is to be approved, in revolutionsper minute.

302 Propellers are to be of steel or bronze as specified forpropeller castings in Pt.2 Ch.2.

303 Moderately or highly skewed propellers will be espe-cially considered with respect to scantlings.

304 The blade thickness of the cylindrical sections at 0.25 R(fixed pitch propellers only) and at 0.35 R is not to be less than:

The thickness at 0.6 R is not to be less than:

U1 and U2 = material constants to be taken as given in Pt.4Ch.5 Sec.1 Table B1.

For fixed blade propellers

For controllable pitch propellers

K4 = ki Z Tice sinα C1, C2, C3, C4 = as given in Table J6.

A = q0 + q1 d + q2 d2 + q3 d3

q0, q1, q2, q3 = as given in Table J7.

d =

d =

ki = 96 at 0.25 R = 92 at 0.35 RKMat = 1.0 for stainless steel propellers = 0.8 for other materials

sin α =

=

K1 as given above is only valid for propulsion by diesel en-gines (by about zero speed, it is assumed 85% thrust and 75%torque for fixed blade propellers and 125% thrust and 100%torque for controllable pitch propellers).

For turbine, diesel-electric or similar propulsion machinery K1will be considered in each particular case.

The thickness of other sections is governed by a smooth curve

Table J4 Values of HM

Ice class HMICE-1A* 1.0 m and a 0.1 m thick consolidated layer of iceICE-1A 1.0 mICE-1B 0.8 mICE-1C 0.6 m

Table J5 Values of Tice

Ice class Open propeller Ducted propellerICE-1A* 84 000 R2 62 400 R2

ICE-1A 62 400 R2 52 000 R2

ICE-1B 52 000 R2 47 600 R2

ICE-1C 47 600 R2 42 800 R2. R > 3 m40 400 R2. R < 1.5 m 1)

1) For 1.5 m < R < 3 m, Tice may be found by linear interpolation.

uengine r.p.m.

propeller r.p.m.--------------------------------------------=

t C1

2RK1 U2C4 0.2+( ) K4+

Zcr K( Mat U1 U2Sr )–------------------------------------------------------------- (mm)=

t t0.35

0.45c0.35

c0.6----------------------- (mm)=

Sr = 2Rno

100-------------

2C2θ C3+( )

K1 = A1d T ho0.85 A2+

0.75uTo

R---------------------

K1 = A1d T ho1.25 A2

uTo

R---------+

2πRHr

----------- for fixed blade propellers

2πR0.7Hr-------------- for controllable pitch propellers

4

d2

16+

---------------------- at 0.25 R

2.86

d2

8.18+

--------------------------- at 0.35 R

DET NORSKE VERITAS


connecting the above section thicknesses.

305 The blade tip thickness at the radius 0.95 R is not to beless than given by the following formulae:

For ICE-1A*:

For ICE-1A, ICE-1B or ICE-1C

σb = ultimate tensile strength in N/mm2 of propeller bladematerial.

The thickness of the blade edge and the propeller tip is not tobe less than 50% of minimum t as given above, measured at1.25 t from the edge or tip, respectively. For controllable pitchpropellers where the direction of rotation is not reversible, thisrequirement only applies to the leading edge and propeller tip.

306 If found necessary by the torsional vibration calcula-tions, minor deviations from the dimensions given in 304 and305 may be approved upon special consideration.

307 The section modulus of the blade bolt connection re-ferred to an axis tangentially to the bolt pitch diameter, is notto be less than:

σb = tensile strength of propeller blade material (N/mm2)σy = yield stress of bolt material (N/mm2)

The propeller blade foot is to have a strength (including stressconcentration) not less than that of the bolts.

308 If a key is used for fitting of the propeller, the dimen-sions of the key are to be sufficient to transmit the full torqueincluding the ice torque, without exceeding the yield stressesin the materials.

309 If the propeller is bolted to the propeller shaft, the boltconnection is to have at least the same bending strength as thepropeller shaft.

The strength of the propeller shaft flange (including stress con-centration) is to be at least the same as the strength of the bolts.

J 400 Shafting

401 The diameter of the propeller shaft at the aft bearing isnot to be less than:

σb = tensile strength of propeller blade material (N/mm2)σy = yield strength of propeller shaft material (N/mm2)c0.35 = as defined in 301t0.35 = as defined in 301.

Between the aft and second aft bearing, the shaft may be even-ly tapered to 1.22 times the diameter of the intermediate shaft,as required for the main class.

Forward of the after peak bulkhead, the shaft may be evenly ta-pered down to 1.05 times the rule diameter of intermediateshaft, but not less than the actual diameter of the intermediateshaft.

402 The diameter of the intermediate shaft, as required forthe main class, is to be multiplied by the factor:

u = as defined in 301I = equivalent mass moment of inertia in kgm2 based on

torque of all parts on engine side of component underconsideration.

Masses rotating with engine speed to be transformedaccording to:

Iequiv = I actual u2

In propulsion systems with hydraulic or electromag-netic slip coupling, the masses in front of the couplingare not to be taken into consideration

It = equivalent mass moment of inertia of propulsion sys-tem in kgm2. (Masses in front of hydraulic or electro-magnetic slip coupling are not to be taken intoconsideration.)

Note that Km will have different values forward and aft of aflywheel or reduction gear.

J 500 Thrust bearing and reduction gear 501 The thrust bearing is to be dimensioned for a thrust ac-cording to:

502 Reduction gears are to satisfy the requirements given inPt.4 Ch.4 Sec.2 when KA in the formulae for σH and σF is sub-stituted by:

K1 = 1.0 for diesel engine driven plantsK1 = Tmax / T0 for electric motor driven plantsu = as defined in 301.I and It = as defined in 402.

Guidance note:It is advised that the sum of nominal torque and ice torque doesnot exceed 85% of the assumed static friction torque Tf of theclutch, i.e.:

Tf = static friction torque of the clutch in Nm.

Table J6 Values of C1, C2, C3, C4

r 0.25 R 0.35 R 0.6 RC1 0.278 0.258 0.150C2 0.026 0.025 0.020C3 0.055 0.049 0.034C4 1.38 1.48 1.69

Table J7 Values of q0, q1, q2, q3

R q0 q1 q2 q3

0.25 R A1A2

8.3063.80

0.370-4.500

-0.340-0.640

0.0300.0845

0.35 R A1A2

9.5557.30

-0.015-7.470

-0.339-0.069

0.03220.0472

0.6 R A1A2

14.6052.90

-1.720-10.300

-0.1030.667

0.02030.0

t 20 4R+( ) 490σb

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

t 15 4R+( ) 490σb

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

Wb 0.1 c0.35 t0.352 σb

σy------ cm

3( )=

dp 11.5σbC0.35t0.35

2

σy-------------------------------

13---

(mm)=

KM

1.25TiceI

uToIt------------------------

13---

, minimum 1.0=

Th 1.3Tho

Tice

R---------- (N)+=

KAice

TiceI

UT0It-------------- K1+=

To

TiceI

u It------------ 0.85Tf≤+

DET NORSKE VERITAS


It is advised that the sum of nominal torque and ice torque doesnot exceed 75% of the maximum allowable impact torque ofelastic couplings, i.e.:

Timpact = maximum allowable impact torque of the coupling inNm.

For couplings with emergency drive device, Timpact is to be takenas the static torque necessary for the device to become active (butnot above the allowable impact torque of the elastic coupling).

Normally, no reinforcement of crankshafts is considered neces-sary. In certain cases, especially with smaller engines (up to1 500 kW) with built-up crankshafts and flywheel at the forwardend, the sum of the maximum dynamic torque of the engine andthe impact torque

should not exceed 85% of friction torque of the shrink.


J 600 Miscellaneous machinery requirements

601 Starting arrangements

The capacity of the air receivers is to be sufficient to providewithout reloading not less than 12 consecutive starts of the pro-pulsion engine, if this has to be reversed for going astern, or 6consecutive starts if the propulsion engine do not have to be re-versed for going astern.

If the air receivers serve any other purposes than starting thepropulsion engine, they are to have additional capacity suffi-cient for these purposes.

The capacity of the air compressors are to be sufficient forcharging the air receivers from atmospheric to full pressure inone (1) hour, except for a ship with the ice class ICE-1A* if itspropulsion engine has to be reversed for going astern, in whichcase the compressors are to be able to charge the receivers inhalf an hour.

602 Sea inlet and cooling water systems.

The cooling water system is to be designed to ensure supply ofcooling water when navigating in ice. The sea cooling waterinlet and discharge for main and auxiliary engines is to be soarranged that blockage of strums and strainers is prevented.

For this purpose at least one cooling water inlet chest shall bearranged as follows:

1) The sea inlet is to be situated near the centre line of theship and well aft if possible. The inlet grids are to be spe-cially strengthened.

2) As a guidance for design the volume of the chest is to beabout one cubic metre for every 750 kW engine output ofthe ship including the output of the auxiliary engines nec-essary for the ship's service.

3) To allow for ice accumulation above the pump suction theheight of the sea chest is not to be less than:

Vs = volume of sea chest according to item 2.The suction pipe inlet is to be located not higher than hmin/3 from top of sea chest.

4) A pipe for discharge cooling water, allowing full capacitydischarge, is to be connected to the chest. Where the seachest volume and height specified in 2 and 3 are not com-plied with, the discharge is to be connected to both seachests. At least one of the fire pumps is to be connected tothis sea chest or to another sea chest with de-icing arrange-ments.

5) The area of the strum holes is to be not less than four (4)times the inlet pipe sectional area.

If there are difficulties in meeting the requirements of 2) and 3)above, two smaller chests may be arranged for alternating in-take and discharge of cooling water. The arrangement and sit-uation otherwise is to be as above.

Heating coils may be installed in the upper part of the chest ofchests.

Arrangements using ballast water for cooling purposes may beuseful as a reserve in ballast condition but can not be acceptedas a substitute for sea inlet chests as described above.

603 Ballast system

An arrangement to prevent freezing of the ballast water is to beprovided for in ballast tanks located fully or partly above theBWL, adjacent to the ship's shell, and needed to be filled foroperation in ice conditions according to A302. For this purposethe following ambient temperatures are to be taken as designconditions:

— Sea water temperature: 0°C— Air temperature: –10°C

Necessary calculations are to be submitted.

When a tank is situated partly above the BWL, an air-bubblingarrangement or a vertical heating coil, capable of maintainingan open hole in the ice layer, will normally be accepted.

The required heat-balance calculations may then be omitted.Guidance note:It is assumed that, before pumping of ballast water is com-menced, proper functioning of level gauging arrangements isverified and air pipes are checked for possible blockage by ice.


To

TiceI

u It------------ 0.75Timpact≤+

TiceI

u It------------

hmin 1.5 Vs3≥

DET NORSKE VERITAS


SECTION 4VESSELS FOR ARCTIC AND ICE BREAKING SERVICE

A. General

A 100 Classification 101 The requirements in this section apply to icebreakersand to passenger and cargo vessels intended to operate unas-sisted in ice-infested waters of sub-Arctic, Arctic and/or Ant-arctic regions.

102 Vessels intended for ice breaking as their main purposeand built in compliance with the following requirements maybe given one of the class notations Icebreaker ICE-05 (or -10 or -15) or Icebreaker POLAR-10 (or -20 or -30), which-ever is relevant.

Vessels built for another main purpose, while also intended forice breaking, may be given the additional class notation ICE-05 (or -10 or -15) or the notation POLAR-10 (or -20 or -30).

103 Arctic class vessels intended for special services whereintermediate ice condition values are relevant may, upon spe-cial consideration, be given intermediate notations (e.g. PO-LAR-25).

104 For POLAR class vessels the design ambient air tem-perature on which the classification has been based will be giv-en the special feature notation DAT(—x°C). The highesttemperatures to be applied for year round operations are statedin B100. For Arctic and/or Antarctic operations with area andseasonal restrictions higher design ambient air temperaturesmay be accepted as basis for the classification.

105 For vessels with the class notation Icebreaker, and forother POLAR class vessels the maximum operational speedon which the ramming design requirements have been basedwill be stated in the “Appendix to the classification certifi-cate”. The operational speed is in no case to be taken as smallerthan stated in 300 for the various class notations.

A 200 Scope201 The following matters are covered by the classification:

— materials in structures exposed to low ambient air temper-atures

— subdivision, intact and damage stability— hull girder longitudinal and transverse strength— local hull structures exposed to ice loads— rudders and steering gears— propellers and propulsion machinery— sea suctions for cooling water— air starting systems

Fig. 1Commonly used definitions of temperatures

MDHT Mean daily high (or maximum) temperatureMDAT Mean daily average temperatureMDLT Mean daily low (or minimum) temperatureMAMDHT Monthly average of MDHTMAMDAT Monthly average of MDATMAMDLT Monthly average of MDLTMEHT Monthly extreme high temperature (ever record-

ed)MELT Monthly extreme low temperature (ever record-

ed).

Mean: Statistical mean over observation period (at least 20years).

Average: Average during one day and night.

A 300 Design principles and assumptions301 Each class notation is related to a particular ice condition

DET NORSKE VERITAS


that the vessel is expected to encounter. Relevant design iceconditions are as given in Table A1. In case intermediate iceconditions are relevant (see 103), nominal ice strength is to berelated to the selected nominal ice thickness.

302 Vessels with the class notation Icebreaker, and otherPOLAR class vessels are expected to encounter pressure ridg-es and other ice features of significantly greater thickness thanthe average thicknesses specified in Table A1. Vessels with theclass notation POLAR only are assumed not to make repeatedramming attempts if the ice fails to break during the first (ac-cidental) ram unless the vessel's speed is kept well below thedesign ramming speed. Vessels with class notation Icebreak-er may make several consecutive attempts to break the ice atmaximum ramming speed. The design speed in ice infestedwaters when ramming may occur, VRAM, is to be specified bythe builder. In general this speed is not to be taken less than:

VRAM = VB + VH (m/s)

VB = specified continuous speed, when breaking maximumaverage ice thickness

VH = speed addition in thinner ice = hice (see Table A1).

In no case the design ramming speed is to be taken less than:

VRAM (minimum)

= 2.0 m/s (3.9 knots) for the notation POLAR-10 = 3.0 m/s (5.8 knots) for the notation POLAR-20 = 4.0 m/s (7.8 knots) for the notation POLAR-30.

For vessels with the class notation Icebreaker the minimumspeed is 2 m/s (3.9 knots) but not less than 1.5 times the speedspecified above when POLAR class notation is also specified.

303 For POLAR class notations steel grades in exposedstructures are to be based on ambient air temperatures lowerthan those generally anticipated for world wide operation. Thedesign temperature for exposed structures is defined as thelowest mean daily average air temperature in the area of oper-ation. This temperature is considered to be comparable withthe lowest monthly mean temperature in the area of operationminus 2°C. If operation is restricted to «summer» navigationthe lowest monthly mean temperature comparison may only beapplied to the warmer half of the month in question. For tem-perature definition, see 400 and Fig.1.

Steel grades in underwater hull structures are to be based on aminimum water temperature somewhat lower than expectedfor world wide operation.

304 For ICE class notations no special consideration for lowambient air temperatures are given unless specified by thebuilder.

A 400 Definitions

401 General symbols and terms are also given in Sec.1 B100.

402 Symbols

VRAM =design speed in m/s when ramming may occur, seealso 302

σice = nominal strength of ice in N/mm2, see Table A1hice = average ice thickness in m, see Table A1EKE = vessel's kinetic energy before ramming = 1/2 ∆ (VRAM)2 (kNm)a, γ = bow shape angles, see Fig.2CWL = vessel's water line area coefficient on LWLs = stiffener spacing in m, measured along the plating.

Stiffener web thickness may be deducted l = stiffener span in m, measured along the top flange of

the member.

The depth of stiffener on crossing panel may be de-ducted when deciding the span.

For curved stiffeners l may be taken as the chord lengthS = girder span in m. The web height of in-plane girders

may be deductedt = rule thickness of plating in mmtk = corrosion addition in mmtw = rule web thickness in mmZ = rule section modulus in cm3

AW = rule web area in cm2, defined as the web thicknesstimes the web height including thickness of flanges

A = rule cross-sectional area in cm2

σy = minimum upper yield stress of material in N/mm2.NV-NS-steel may be taken as having σy = 235 N/mm2

σ = nominal allowable bending stress in N/mm2 due to lat-eral pressure

τ = nominal allowable shear stress in N/mm2.

403 External structure is defined, with respect to design tem-perature, as the plating with stiffening to a distance of 0.5 me-tre from the shell plating, exposed decks and exposed sides andends of superstructure and deckhouses.

404 Temperature terms (see also Fig.1):

Design temperature is a reference temperature used as a crite-rion for the selection of steel grades.

Mean daily average temperature is the statistical mean aver-age temperature for a specific calendar day, based on a number

of years of observations (= MDAT).

Monthly mean temperature is the average of the mean dailytemperature for the month in question (= MAMDAT).

Lowest mean daily temperature is the lowest value on the an-nual mean daily temperature curve for the area in question. Forseasonally restricted service the lowest value within the time ofoperation applies.

Lowest monthly mean temperature is the monthly mean tem-perature for the coldest month of the year.

Table A1 Ice conditionsClass notation Type of ice encountered Nominal ice strength

σice(N/mm2)

Nominal ice thickness

hice (m)

Limiting impact conditions

ICE-05 ICE-10 ICE-15

Winter ice with pressure ridges4.2 5.6 7.0

0.5 1.0 1.5

No ramming anticipated

POLAR-10 POLAR-20 POLAR-30

Winter ice with pressure ridges and multi-year ice-floes and glacial ice inclusions

7.0 8.5 10.0

1.0 2.0 3.0

Accidental ramming

Icebreaker As above As above As above Repeated ramming

DET NORSKE VERITAS


Fig. 2Bow shape angles

405 The hull structure (shell plating with stiffening) to be re-inforced against local ice loads is divided into 6 different areas.The areas are defined as follows (see also Fig.3):

Bow area

Longitudinally from stem to a line parallel to and 0.04 L aft ofthe border line of flat side of hull forward. If the hull breadth isincreased over a limited length forward of the flat side the bowarea need normally not extend aftwards beyond the widest sec-tion of each waterline.

The bow area need not extend aftwards beyond 0.3 L from theforward perpendicular.

Vertically from a line defined by a distance zlm below BWL(aft) and the intersection between the keel line and the stemline (forward) to a line defined by the distances zua (aft) and zuf(forward) above LWL. For ships with an ice knife fitted, theline of the lower vertical extension may be drawn to a point0.04 L aft of the upper end of the knife and further down to thebase line (see also Fig.3).

Fig. 3Extension of bow area

Stem area

The part of the bow area between the stem line and a line 0.06L aft of the stem line or 0.125 B outboard from the centre line,whichever is first reached.

Vertically from a line defined by a distance zla below BWL, toa line defined by a distance zua above LWL.

Bow side area

The part of the bow area not defined as the stem area.

Midship area

Longitudinally from the bow area to a line parallel to and 0.04L forward of the border line of flat side of hull aft, or to a line

0.2 L aft of amidships, whichever is the aftermost.

Vertically from a line defined by a distance zlm below BWL,to a line defined by a distance zua above LWL.

Bottom area

Longitudinally aft of 0.3 L from F.P. and transversely over theflat bottom including deadrise. For ships with bow ice knife,the bottom area may be extended forward to the ice knife.

Lower bow transition area

Transition area between the stem area and the side/bottom ar-eas.

Stern area

Longitudinally from the midship area and the lower transitionarea to the stern.

Vertically from a line defined by a distance zla below BWL, toa line defined by a distance zua above LWL.

Upper transition area

Over the full length of the vessel.

Above the bow/midship/stern areas a distance of zut.

LWL and BWL are defined in Sec.1 B200.

Values of zla, zlm, zua, zuf and zut are given for various class no-tations in Table A2.

A 500 Documentation

501 LWL and BWL as well as the border line of flat side areto be indicated on the shell expansion plan together with the icereinforced areas as given in Fig.4.

502 Maximum design ramming speed (VRAM) in ice infestedwaters as well as design speed for continuous ice breaking op-erations (VB) are to be stated on the midship section plan forships with class notations POLAR or Icebreaker.

503 For documentation in connection with stability and wa-tertight integrity, see L300.

504 Applicable special limitations to the operation of thevessel in ice infested waters are to be stated in the ship's load-ing manual, see Pt.3 Ch.1 Sec.1 C100.

Possible limitations are:

— allowable draughts, maximum and minimum— loading conditions with respect to strength and stability— ambient temperature— design speed— instruction for filling of ballast tanks

505 Where ice exposed plating is fitted with a special wearaddition, the plate thickness including wear addition is to begiven on the shell expansion plan in addition to the net thick-ness required by the rules.

F.P. 1 m

α

γ

BUTTOCK

STEM LIN

E

BASE LINE

LW L

LW L

CENTRE LINE

Z ua

Z lm

Z uf

LWLBWL

0.3 L0.04 L

Table A2 Vertical extent of ice reinforced areasClass notation Parameters for vertical extent (m)

zla zlm1) zua zuf zut

ICE-05 ICE-10 ICE-15

1.7 2.2 4.6

1.1 1.6 3.7

0.8 1.0 1.9

1.3 1.6 2.5

0.3 0.5 0.7

POLAR-10 POLAR-20 POLAR-30

2.9 6.0

11.9

2.3 4.6 9.2

1.4 2.8 5.5

1.9 3.7 7.4

0.5 1.0 1.9

1) zlm (maximum) = the vertical distance from the BWL to the point on the frame contour amidships where the tangent is at 45 degrees.

DET NORSKE VERITAS


Fig. 4Ice reinforced areas

B. Materials and Corrosion Protection

B 100 Design temperatures101 Steel grades to be used in hull structural members areto be determined based on the design temperature for the struc-ture in question.

102 For external structures above BWL the design tempera-ture may normally be taken as the lowest mean daily averageair temperature in the area of operation. Unless a service re-striction notation is also given, limiting the navigation to spec-

ified areas and/or time of year, the design temperature is not tobe taken higher than in accordance with Table B1.

BORDER LINE O F FLAT SIDE( at LW L )

LO W ER TURN O F THE BILG E

BO RDER LINE O F FLAT SIDE

TRANSITION S IDE/BO TTOM

UPPERTRANSITIONAREA

STERN AREA

BOW AREA

BO TTOMAREA

M IDSHIP AREA

LO W ER BOWTRANSITION AREA

0.04L0.06L(m ax.)

0.3L

0.04L

0.2LA.P.

zut

z la

zua

z la

z lm zua

zut

zufLW L

BW L

F.P.

0.125B(max.)

Table B1 Design temperature for exposed structures

Class notation Design temperatureCorresponding ex-treme low tempera-

turePOLAR-10 - 30°C ( - 50°C)POLAR-20 - 35°C ( - 55°C)POLAR-30 - 40°C ( - 60°C)

DET NORSKE VERITAS


B 200 Structural categories

201 Structural strength members or areas are classified in 4different classes for the purpose of selecting required materialgrades. The classes are generally described as follows:

Class IV:

— Strakes in the strength deck and shell plating amidships in-tended as crack arrestors.

— Highly stressed elements in way of longitudinal strengthmember discontinuities.

Class III:

— Plating chiefly contributing to the longitudinal strengthamidships.

— Appendages of importance for the main functions of thevessel.

— Foundations and support structures for heavy machineryand equipment.

Class II:

— Structures contributing to longitudinal and/or transversehull girder strength in general.

— Structures for subdivisions.— Structures for cargo, bunkers and ballast containment.— Internal members (stiffeners, girders) on plating exposed

to external low temperatures where class III and IV is re-quired.

Class I:

— Local members in general unless upgraded due to specialconsiderations of loading rate, level and type of stress,stress concentrations and load transfer points and/or con-sequences of failure.

202 Hull girder plating in vessels of conventional design isnormally classified as specified in Table B2. Single strakes re-quired to be of class IV or of grade NV E/EH are to havebreadths not less than (800+5 L) mm, maximum 1 800 mm.

203 The material class requirement may be reduced by oneclass for:

— laterally loaded plating having a thickness exceeding 1.25times the requirement according to design formulas,

— laterally loaded stiffeners and girders having section mod-ulus exceeding 1.5 times the requirement according to de-sign formulas

204 Structural materials for stern frames, rudder horns, rud-ders and shaft brackets are not to be of lower grades than cor-responding to class III.

B 300 Selection of steel grades

301 Plating materials for various structural categories as de-fined in 200 of exposed members above the ballast waterlineof vessels with class notation POLAR are not to be of lowergrades than obtained from Fig.5 using design temperatures asdefined in 100.

Plating materials of non-exposed members and of vessels withclass notation ICE are not to be of lower grade than obtainedaccording to Pt.3 Ch.1 Sec.2 B200, Table B1.

Fig. 5Required steel grades

302 Steels for hull plating are to satisfy the requirements inPt.2.

Materials deviating from those specified in Pt.2 may be accept-ed as equivalent subject to consideration in each separate case.Charpy-V impact energy levels equivalent to those given in

Table B2 Classification of longitudinal and transverse strength members, platingStructural member Within 0.2 L

aft of amid-ships and 0.3 L forward of amidships

Elsewhere

Deck plating exposed to weather, in general

Side plating

Longitudinal bulkhead plating, in general

Transverse bulkhead plating

II II

Bottom plating including keel plate

Strength deck plating 2)

Continuous longitudinal members above strength deck excluding lon-gitudinal hatch coamings

Upper strake in longitudinal bulk-head

Upper strake in top wing tank

III 5) II

Sheer strake at strength deck6)

Stringer plate in strength6) deck

Deck strake at longitudinal bulk-head 1)

Bilge strake 3)

Continuous longitudinal hatch coamings7)

IV III 4)

1) In ships with breadth exceeding 70 m at least three deck strakes are to be class IV amidships.

2) Plating at corners of large hatch openings is to be specially considered. Class IV is to be applied in positions where high local stresses may occur.

3) May be of class III amidships in ships with a double bottom over the full breadth and with length less than 150 m.

4) May be class II outside 0.6 L amidships.

5) May be class II if relevant midship section modulus as built is not less than 1.5 times the rule midships section modulus, and the excess is not credited in local strength calculations.

6) Not to be less than grade NV E/EH in ships with length ex-ceeding 250 m.

7) Not to be less than grade NV D/DH.

DET NORSKE VERITAS


Pt.2 are shown in Fig.6.Guidance note:The manganese contents of normal strength steel and highstrength steel should not exceed 1.2%.


Fig. 6CVN test results equivalent to NV specifications

B 400 Coatings

401 Wear resistant coating is assumed used for the externalsurfaces of plating in ice reinforced areas.

B 500 Corrosion additions

501 Hull structures are in general to be given a corrosion ad-dition tk as required by the main class, see Table B3.

B 600 Equipment

601 Structural materials in windlasses (when exposed) are tobe of class III. Design temperature to be −20°C for POLARclass notations, 0°C elsewhere.

C. Ship Design and Arrangement

C 100 Hull form

101 The bow is to be shaped so that it can break level ice ef-fectively and at continuous speed, up to a thickness as indicat-ed in Table A1 for the various class notations.

102 Vessels with class notation Icebreaker, and other PO-LAR class vessels are to have a bow shape so that the bow willride up on the ice when encountering pressure ridges or similarice features that will not break on the first ramming.

103 The stern is to be shaped so that it can displace broken

ice effectively when the vessel is going ahead.

104 Masts, rigging, superstructures, deck houses and otheritems on deck are to be designed and arranged so that excessiveaccumulation of ice is avoided. The rigging is to be kept at aminimum, and the surfaces of erections on deck are to be aseven as possible.

105 Weathertight doors are to be suitably designed for use inlow temperature environment with respect to:

— strength of cleats and the choice of steel with adequateductility

— flexibility of packing material— ease of maintenance, e.g. interior accessible grease fittings— ease of operations, e.g. low weight and preference to cen-

tral handwheel operated cleats.

106 Air pipe closures are to be designed so that icing orfreezing will not make them inoperable.

107 Freeing ports are to be designed so that blocking by iceis avoided as far as possible and so that they are easily acces-sible for removal of ice should blocking occur.

C 200 Appendages201 In vessels with class notation Icebreaker and in otherPOLAR class vessels an ice knife may be required forward toavoid excessive beaching and submersion of the deck aft. Thisrequirement will be based on consideration of design speedand freeboard, and may result in additional requirements re-garding accelerations and strength.

202 Ice horns are to be fitted directly abaft each rudder insuch a manner that:

— the upper edge of the rudder is protected within two de-grees to each side of midposition when going astern, and

— ice is prevented from wedging between the top of the rud-der and the vessel's hull.

C 300 Mooring equipment301 The housing arrangement for anchors is to be designedso that possible icing will not prevent the anchor from fallingwhen released.

D. Design Loads

D 100 Ice impact forces on the bow101 The vertical design force component due to head onramming (not applicable to vessels with class notation ICE on-ly) is given by:

P ZR = PR FEL (kN)

Table B3 Corrosion addition tk

Compartment Structure

Shell plating (mm)

Internal struc-ture (mm)

Ballast tank 1.0 1.5Dry cargo hold which may be used as ballast tank 0.5 1.0

Dry compartment 0.0 0.0

PR = 28CREIMP

γtan--------------------

0.6σice αtan( )0.4

in general

For spoon bows: αtan 1.2B

0.1

γcos---------------=

EIMP = EKE

γ2tan

γ 2.5+2

tan---------------------------

FEL = EIMP

EIMP CLPR2

+------------------------------------

CL = L

3

3 1010

IV×--------------------------

DET NORSKE VERITAS


CR = 1 for the class notation POLAR only = 2 for the class notation Icebreaker EKE, σice, α and γ as defined in A400.

L as defined in Sec.1 B100.

IV = moment of inertia in m4 about the horizontal neutral axisof the midship section.

102 The total design force normal to the shell plating in thebow area due to an oblique impact with an ice feature is givenby:

PZR = vertical ramming load as given in 101

L and B as defined in Sec.1 B100.

EKE, σice, α and γ as defined in A400.

D 200 Beaching forces

201 The vertical design force resulting from beaching on alarge ice feature (not applicable to vessels with class notationICE only) is in general given by:

GB =

kb = 2 go (1 − rfw)rfw = reduction factor due to energy lost in friction and

waves = 0.3.

EKE, σice, CWL, γ and α as defined in A400.

L, B and go as defined in Sec.1 B100.

202 For vessels with vertical ram bow the vertical designforce in beaching need not be taken larger than:

X = horizontal distance from FPICE to centre of ver-tical ram bow in m

FPICE = intersection point of stem line and deepest ice-breaking waterline

C WL = waterline area coefficient.

L and B as defined in Sec.1 B100.

D 300 Ice compression loads amidships

301 All vessels are to withstand line loads acting simultane-ously in the horizontal plane at the water level on both sides ofthe hull. These loads are assumed to arise when a vessel istrapped between moving ice floes.

302 The design line loads are to be taken as:

hice = average ice thickness as defined in A400

β = angle of outboard flare at the waterlevel. Need not tobe taken as less than 10 degrees.

D 400 Local ice pressure401 All vessels are to withstand local ice pressure as definedfor the different ice class notations and as applied to the differ-ent ice reinforced areas. The design pressure is to be appliedover a corresponding contact area reflecting the type of load inquestion.

402 The basic ice pressure is in general to be taken as:

po = 1 000 FA σice (kN/m2)

FA = correction factor for ice reinforced area in question = 1.0 for bow and stem area in general. = 1.3 for stem area in ships with wedge-shaped bows and

class notation POLAR or Icebreaker. For other bowtypes the factor will be specially considered

= 0.6 for midship area in general = 0.5 for midship area if ship breadth in bow area larger

than ship breadth in midship area = 0.6 for stern area in general = 0.8 for stern area in ships with class notation Ice-

breaker = 0.25 for bottom area.

FA = 1.0 for stern area in ships with the class notation: Icebreaker, fitted with pod and or thruster propulsion units.

For the lower transition areas 2/3 of the FA-value for the adja-cent area above may be used.

For the upper transition area half the FA-value for adjacent ar-eas to be used.

σice as defined in A400.

403 The design pressure is in general to be taken as:

p = FB po (m2)

FB = correction factor for size of design contact area AC

=

=

AC = ho w (m2)ho = h in general = s, maximum for longitudinals = l, maximum for non-longitudinal frames = 1.4 l, maximum for connection area of non-longitudi-

nal frames = S, maximum for girders supporting longitudinals = l, maximum for stringers supporting non-longitudinal

framesh = effective height of contact area in m = 0.4 hice (m) in general = 0.8 hice (m) in stem area in general

=

in stem area for vessels with class notation POLAR orIcebreaker

= 0.8 hstem (m) in bow area outside stem areahstem = h as given for stem area.

POI

PZRFSIDE

γcos------------------------- (kN)=

FSIDE = 1.9

αtan( )0.4-----------------------

σice

EKE----------

0.05 in general

α = 1tan .2B

0.1

γcos--------------- for spoon shaped bows

PZB GB kbEKELB (kN)=

CWL CWL 0.5–( )CWL 1+( )

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

PZB

10.6CWLBLX γtan

1 15 0.55 X L⁄( )–[ ]2+

------------------------------------------------------ (kN)=

q165

βsin----------- hice( )1.5

(kN/m)=

0.58

AC( )0.5------------------- for AC 1.0 m

2≤

0.58

AC( )0.15---------------------- for AC 1.0 m

2>

P645σice-------------------

0.6 γ α2

tan+2

tanαtan

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

0.5

DET NORSKE VERITAS


For spoon bows:

P = the largest of PZR and PZB as given in D100 and D200.w = critical width of contact area in m = l for longitudinals = s for non-longitudinal frames = 1.4 l for connection area for longitudinals = l for vertical girders supporting longitudinal main

frames = S for stringers supporting vertical main frames.

l, S, α and γ as defined in A400.

The relations are illustrated in Fig.7.

Fig. 7Design contact areas

D 500 Accelerations501 Substructures, equipment and supporting structures areto withstand accelerations arising as a result of impacts withice features.

502 The combined vertical acceleration at any point alongthe hull girder (not applicable to vessels with class notationICE only) may be taken as:

FX = 1.3 at F.P. = 0.1 at midships = 0.4 at A.P.

Linear interpolation is to be applied between specified posi-tions.

PZR as derived in 100.

∆ as defined in Sec.1 B100.

av does not include the acceleration of gravity.

503 The combined transverse acceleration at any point alongthe hull girder may be taken as:

FX = 1.5 at F.P. = 0.25 at midships = 0.5 at A.P.

Linear interpolation is to be applied between specified posi-tions.

POI as derived in 100.


504 The maximum longitudinal acceleration is taken to bethe same at any point along the hull girder.

ϕ = maximum friction angle (between steel and ice), nor-mally taken as 10°

H = distance in m from lowest waterline to position consid-ered.

PZR as derived in 100.


γ as defined in A400.

E. Global Strength

E 100 General

101 Hull girder shear forces and bending moments as stipu-lated in this subsection are to be combined with relevant still-water conditions as stipulated for the main class. Wave loadconditions as stipulated for the main class need not be regardedas occurring simultaneously with the shear forces and bendingmoments resulting from ramming and beaching.

102 The shear forces and bending moments are to be regard-ed as the design values at probability level equivalent to themaximum load in a service life of 20 years.

103 In addition to the maximum stress requirements given inthis subsection, individual elements are to be checked with re-spect to buckling under the ramming and beaching load condi-tions, according to accept criteria as stipulated for the mainclass.

E 200 Longitudinal strength

201 The following requirements are applicable to vesselswith class notation Icebreaker and other POLAR class ves-sels (i.e. not to vessels with class notation ICE only).

202 The design vertical shear force at any position of the hullgirder due to ramming and/or beaching is given by:

QICE = kiq P (kN)

k iq = 0.4 at F.P. = 1.0 between 0.05 L and 0.1 L from F.P. = 0.4 between 0.7 L and 0.2 L from A.P. = 0.0 at A.P.

Between specified positions kiq is to be varied linearly. Valuesof kiq may also be obtained from Fig.8.

P = PZR as given in D100 or = PZB as given in D200, whichever is the greater.

The thickness requirements for side shell and possible longitu-dinal bulkhead platings are to be calculated for different cargoand ballast conditions as stipulated in Pt.3 Ch.1 Sec.5 D replac-ing QW with QICE as calculated above.

αtan 1.2B

0.1

γcos---------------=

ICESHEET

VERTICAL GIRDERS

h ice

W

h

LONGITUDINAL STRINGERS

l l

S

av

2.5PZR

∆------------------ FX m s

2⁄( )=

at

3POI

∆------------ FX m s

2⁄( )=

al

1.1PZR γ φ+( )tan

∆--------------------------------------------

7PZRH

∆L------------------ m s

2⁄( )+=

DET NORSKE VERITAS


Fig. 8Distribution of vertical shear force due to ramming and beaching

Fig. 9Distribution of vertical bending moment due to ramming

Fig. 10Distribution of vertical bending moment due to beaching

203 The design vertical sagging bending moment at any po-sition of the hull girder due to ramming and/or beaching is giv-en by:

MICE S = 0.25 kim P L (kNm)

k im = 0.0 at F.P. and A.P. = 1.0 between 0.25 L from F.P. to 0.35 L from A.P. for

ramming load condition = 1.0 between 0.3 L and 0.5 L from F.P. for beaching

load condition.

Between specified positions kim is to be varied linearly. Valuesof kim may also be obtained from Fig.9 and Fig.10 for rammingand beaching load conditions respectively.

P = P ZR or PZB as given in D100 or D200 for ramming andbeaching load conditions respectively.

L as defined in Sec.1 B100.

204 The design vertical hogging bending moment at any po-sition of the hull girder due to vibration following the initialramming is given by:

MICE H = 0.6 MICE SR (kNm)

MICE SR = as given in 203 for ramming load condition.

205 The section modulus requirement about the transverseneutral axis is given by:

MS = design stillwater bending moments according toPt.3 Ch.1 Sec.5 B

MICE = design bending moment due to ramming and/orbeaching, see 203 and 204.

The most unfavourable combinations of stillwater and ram-ming/beaching bending moments are to be applied.

f1 = material factor depending on material strength group = 1.00 for NV-NS steel = 1.08 for NV-27 steel = 1.28 for NV-32 steel = 1.39 for NV-36 steel.

For steel other than NV steel the factor f1 may generally be tak-en as:

σy = yield stress as defined in A400.

206 The buckling strength of longitudinal strength membersin bottom, side and deck as well as longitudinal bulkheads sub-ject to compressive and/or shearing loads is to be checked ac-cording to Pt.3 Ch.1 Sec.14.

E 300 Transverse strength amidships301 The line loads specified in D300 are to be applied at dif-ferent water levels including LWL and BWL as found neces-sary depending on the structural arrangement of the vessel.

302 The line loads are to be applied over one full hold/tanklength or as found necessary to assess the structural strength oftransverse bulkheads and decks supporting the ice reinforcedregions.

303 The calculations of transverse strength amidships are tobe based on the most severe realistic combination of ice com-pression loads and static load conditions.

304 Recognised structural idealisation and calculation meth-ods are to be applied. Effects to be considered are indicated inPt.3 Ch.1 Sec.13 D200.

305 The calculated stresses are not to exceed allowablestresses as stipulated in Pt.3 Ch.1 Sec.13 B400.

E 400 Overall strength of substructure in the foreship401 The total impact forces as stipulated in D100 may havea decisive effect on primary structural systems in the foreship.The loads are assumed to be evenly distributed in such a man-ner that local pressures will not exceed those stipulated for lo-cal members directly exposed to the load as given in D402.

402 The design ramming load (not applicable to vessels withclass notation ICE only) taken as

PZR/cosγis to be applied with its center on the stem line at the water line

ZMS MICE+

180f1----------------------------10

3 cm

3( )=

f1

σy

235---------

0.75=

DET NORSKE VERITAS


forward. The most unfavourable design draught forward is tobe assumed with regard to positioning of the load.

403 The design bow side impact load taken as POI should bepositioned at various positions within bow side area consid-ered critical for the overall strength of the substructure.

Such parts of the bow side area which are aft of the border lineof the flat side need normally not be considered with respect toPOI.

404 Recognised structural idealisation and calculation meth-ods are to be applied. Effects to be considered are indicated inPt.3 Ch.1 Sec.13 D200.

405 The equivalent stress as defined in Pt.3 Ch.1 Sec.13B400 is not to exceed 235 f1. This is normally achieved forgirder type members when the bending stress is not exceeding210 f1 and the mean shear stress over a web cross-section is notexceeding 110 f1 with f1 as defined in 205.

F. Local Strength

F 100 General101 The requirements in this subsection apply to membersthat may be directly exposed to local ice pressure.

102 The buckling strength of web plates and face plates ingirders and stringers subject to ice loads is to be checked ac-cording to methods given in Pt.3 Ch.1 Sec.14 or equivalent.

103 In curved regions of ice exposed plating, the stiffening isnormally to be in the direction of the maximum curvature.

104 Framing in ice reinforced areas are in general to havesymmetrical cross—section with the web to the extent possiblepositioned at right angle to the plane of the plate. The bendingefficiency and tripping capacity of frames are to be document-ed by calculations according to recognised methods as consid-ered necessary.

105 Ice exposed knuckles are in general to be supported bycarlings or equivalent structures.

106 Plate fields adjacent to stem and possible knuckles in theforward shoulder are to be supported so as to be of squareshape or otherwise locally strengthened to equivalent standard.

F 200 Plating201 The thickness of plating exposed to patch load is gener-ally not to be less than:

ka = aspect ratio factor for plate field = 1.1 − 0.25 s/ l, maximum 1.0, minimum 0.85kw = influence factor for narrow strip of load (perpendicu-

lar to s)

= , maximum 1.0

mp = bending moment factor = f(b/s), see Table F1 (taking r as b/s)a = s in general = ho for transversely stiffened panelsho = h, see D400 = s, whichever is the smallerb = s in general = ho for longitudinally stiffened platingpo = basic ice pressure in kN/m2 as calculated in D400tk = corrosion addition as given in B500.

s, l and σy as defined in A400.

F 300 Longitudinal stiffeners301 Stiffeners in the bow-, midship- and stern ice reinforcedareas which are largely parallel to the waterline are defined aslongitudinals.

302 The web sectional area of stiffeners in ice reinforced ar-eas is not to be less than:

and the web thickness is not to be less than:

for flanged profiles.

The section modulus is not to be less than:

The stiffener connection area ao as defined in Pt.3 Ch.1 Sec.12C400 is not to be less than:

ho = h, see D400 = s, whichever is smallerhw = height of web in mmpo = basic ice pressure in kN/m2 as calculated in D400τ = 110 f1σ = 210 f1ts = shell plate thickness in mm.


AK = tk hw 10 -2 (cm2)wk = section modulus corrosion factor, see Pt.3 Ch.1 Sec.3

C1004c = factor as given in Table C4 of Pt.3 Ch.1 Sec.12 C400.α = 0.5 for AC ≤ 1.0

t 23kas

0.75

ho0.25

---------------kwpo

mpσy------------- tk (mm)+=

1.34.2

a s⁄ 1.8+( )2-------------------------------–

Table F1 Parameters for local strength formulas (general application)

r mp me0.05 27.4 112.200.10 14.25 58.740.15 9.87 40.670.20 7.69 31.710.25 6.40 26.400.30 5.57 22.890.35 4.95 20.800.40 4.50 18.630.45 4.09 17.290.50 3.77 16.220.60 3.31 14.740.70 3.02 13.830.80 2.83 13.280.90 2.72 12.991.00 2.68 12.90

For intermediate values of r the parameters may be obtained by linear interpolation.

AW

3.7 l 0.5s–( ) h o1 α–

po

τ β lα

sin----------------------------------------------------- AK cm

2( )+=

tw 1.5po

σy βsin-----------------

0.67 hwho

ts------------

0.33tk (mm)+=

Z41ho

1 α–l2 α–

powk

σ βsin----------------------------------------------- cm

3( )=

a010cPτ βsin---------------

6.5 c h01 α–

l 0.5s–( )p0

τ β 1.4l( )αsin

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

DET NORSKE VERITAS


= 0.15 for AC > 1.0AC = as defined in D403β = angle of web with shell plating.

F 400 Other stiffeners401 The web sectional area is not to be less than:

and the web thickness is not to be less than:

for flanged profiles.

The section modulus is not to be less than:

The connection area ao as defined in Pt.3 Ch.1 Sec.12 C400 isnot to be less than:

ks =

= 0.69 minimum

C1 = arm length of bracket in mho = h, see D400 = l, whichever is the smallerh1 = h = 1.4 l, whichever is the smallerhw = web height in mmme = bending moment factor = f (ho/ l), see Table F1 (taking r=ho/ l) in general

=

for stiffener with simply supported ends

po = basic ice pressure in kN/m2, see D400τ = 110 f1σ = 210 f1 in general = 190 f1 when both ends are simply supportedts = shell plate thickness in mm.


AK = tk hw 10-2 (cm2)wk = section modulus corrosion factor, see Pt.3 Ch.1 Sec.3

C1004c = factor as given in Table C4 of Pt.3 Ch.1 Sec.12 C400α = 0.5 for AC ≤ 1.0 = 0.15 for AC > 1.0

AC = as given in D403β = angle of web with shell plating.

F 500 Girders

501 Within ice reinforced areas, girder structures supportingshell stiffeners are to be considered for ice loading. The iceload area to be applied for the girder system will depend on thestructure considered, its position and orientation etc. The icepressure load and load area are generally to be taken as givenin D403.

502 For girders being part of a complex system of primarystructures, analysis by direct calculation may be required. Forsuch girder structures in the foreship, the requirements given inE400 apply.

503 The following requirements apply to evenly spaced gird-ers for which the ends may be considered as fixed, simply sup-ported or constrained due to repetitive continuation of thegirder beyond the support. The stiffness of supported members(frames or longitudinals) is assumed to be much smaller thanthe stiffness of the girder considered.

The web sectional area at any point along a girder is not to beless than:

and the section modulus is not to be less than:

ks = shear factor, see Table F2 (taking r as (a+s)/S)s = spacing of secondary members in mme = bending moment factor = f(a/S) in case of a continuous member, see Table F1

(taking r as a/S)

= in case of fixed ends

= in case of simply supported ends

a = S in general = ho, maximum for girders supporting longitudinalsb = l in general = ho, maximum for girders supporting non-longitudinal

framesho = h, see D400po = basic ice pressure in kN/m2 as given in D400τ = 110 f1σ = 210 f1 in general = 190 f1 when both ends are simply supportedα = 0.5 for AC ≤ 1.0 = 0.15 for AC > 1.0AC = as given in D403β = angle of web with shell plating.

l and S as defined in A400.

AW

5.8ks hos( )1 α–l 0.5s–( )po

τ l βsin------------------------------------------------------------------- AK (cm

2 )+=

tw 1.5po

σy βsin-----------------

0.67 hws

ts---------

0.33tk (mm)+=

Z520l

2s

1 α–powk

meσ hoα βsin

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

a0

5.8cs1 α–

1 0.1h1

2

l2

--------–

l 0.5s–( )ho1 α–

po

τl βsin--------------------------------------------------------------------------------------------------- cm

2( )=

1 0.5C1 0.5ho+( )3

l3

---------------------------------- 1.5C1 0.5ho+( )2

l2

----------------------------------–+

8

2ho

l-----–

ho

l-----

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

AW

5.8 ks a b po

τ β ACα

sin----------------------------- AK cm

2( )+=

Z550S

2bpowk

meσ β ACα

sin----------------------------------- =

24

3aS---

–

2

a

S---

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

8

2aS---

–

a

S---

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

DET NORSKE VERITAS


AK and wk, see 302.

G. Rudders, Propeller Nozzles and Steering Gears

G 100 General101 Sternframes, rudders, propeller nozzles and steeringgears are in general to be designed according to the rules givenin Pt.3 Ch.3 Sec.2.

102 Additional requirements for ice reinforced vessels aregiven in the following. For vessels with rudders which are notlocated behind the propeller, special consideration will bemade with respect to the longitudinal ice load.

103 Plating materials in rudders, propeller nozzles and rud-der horns are to be in accordance with B. Forged or cast mate-rials in structural members subject to lower designtemperatures than –10°C according to B100 are to be impacttested as stipulated in Pt.2 Ch.2 Sec.5 and Sec.7, respectively.

104 The rudder stock and upper edge of the rudder are to beeffectively protected against ice pressure.

105 Aft of the rudder an ice knife with depth minimum = 0.8hice or an equivalent arrangement is to be arranged.

106 Exposed seals for rudder stock are assumed to be de-signed for the given environmental conditions such as:

— ice formation— specified design temperature.

G 200 Ice loads on rudders201 An ice load area is defined on the rudder with a lengthequal to the length of the rudder profile lr and height equal tothe effective ice load height (h). The general design rudderforce (FR) is given by the following formula:

FR = 0.2 (h lr)0.85 K po (kN)

K =

z = distance from rudder bottom to centre of the assumedice load area in m

zbl = distance from rudder bottom to the ballast waterline inm

L = as defined in Sec.1 B100po = as given in D400.

The rudder force FR gives rise to a rudder torque (MTR) and abending moment in the rudder stock (MB), which both willvary depending on the position of the assumed ice load area,and on the rudder type and arrangement used.

In general the load giving the most severe combination of FR,MTR and MB with respect to the structure under considerationis to be applied in a direct calculation of the rudder structure.

The design value of MTR is given by:

M TR = FR (0.6 l r − XF) (kNm)

= 0.15 FR l r minimum

XF = longitudinal distance in m from the leading edge of therudder to the centre line of the rudder stock.

In lieu of direct calculation design values of MB and FR, appli-cable for the rudder stock diameter at the lower end, may nor-mally be taken as:

Spade rudders:

FR = 0.2 ( h l r)0.85 po (kN)

MB = FR HB (kNm)

Semi spade rudders:

FR = 0.2 ( h l r)0.85 po (kN)

MB = 0.5 FR HP (kNm)

Balanced rudders:

MB = 0.25 FR HH (kNm)

HB = distance (m) from lower end of rudder to middle ofneck bearing

HP = distance (m) from lower end of rudder to middle ofpintle bearing

HH = distance (m) from centre of heel bearing to centre ofneck bearing

h = as given in D403.

202 An additional ice load area is defined on the uppermostpart of the rudder including ice knife with a length equal to therudder (including ice knife) ( lr) and height below the hullequal to the nominal ice height (hice). This gives rise to a force(F) given by:

F = k p hice l r (kN)

p = design ice pressure in kN/m2 in stern area as given inD400

k = 0.7 in general = 1.0 for vessels with class notations POLAR or Ice-

breaker.

The force F is to be divided between rudder and ice knife ac-cording to their support position. The force acting on the iceknife may generally be taken as:

X = distance from leading edge of rudder to point of attackof the force F

Table F2 Shear factor ks

r

0.0 1.00 1.00 1.000.1 0.99 0.99 0.950.2 0.96 0.98 0.900.3 0.92 0.96 0.850.4 0.87 0.93 0.800.5 0.81 0.89 0.750.6 0.75 0.85 0.700.7 0.69 0.80 0.650.8 0.62 0.74 0.600.9 0.56 0.69 0.551.0 0.50 0.63 0.501.1 0.5-0.05 i 0.63-0.06 i 0.5-0.05 i1.2 0.5-0.10 i 0.63-0.12 i 0.5-0.10 i1.3 0.5-0.15 i 0.63-0.18 i 0.5-0.15 i1.4 0.5-0.20 i 0.63-0.24 i 0.5-0.20 i1.5 0.5-0.25 i 0.63-0.30 i 0.5-0.25 i

i = b/2s. maximum = 1.0

1z

zbl 0.01L–----------------------------+

FR 0.2 hlr( )0.851

HB

2zbl 0.02L–-------------------------------+

po (kN)=

FK

F X XF–( )XK XF–( )

--------------------------=

DET NORSKE VERITAS


= 0.5 l r (m) minimum = 0.67 l r (m) maximumXK = distance in m from leading edge of rudder to centre of

ice knife.

G 300 Rudder scantlings301 The scantlings of rudders, rudder stocks and shafts, pin-tles, rudder horns and rudder actuators are to be calculatedfrom the formulae given in Pt.3 Ch.3 Sec.2, inserting the rud-der torque MTR, bending moments MB and rudder force FR asgiven in 201, all reduced by factor 0.7.

302 Provided an effective torque relief arrangement is in-stalled for the steering gear, and provided effective ice stop-pers are fitted, the design rudder torque need not be takengreater than:

M TR = MTRO

MTRO =steering gear relief torque in kNm.

303 For rudder plating the ice load thickness is to be calcu-lated as given in F200 using the design ice pressure as givenfor the stern area reduced linearly to half value at the lower endof the rudder.

304 Scantlings of rudder, rudder stock, rudder horn, rudderstoppers and ice knife as applicable are also to be calculated forthe rudder force given in 202 acting on the rudder and iceknife, with respect to bending and shear. Allowable stresses asgiven in F400.

G 400 Ice loads on propeller nozzles401 A transverse ice load area positioned at the level of thenozzle center is defined on the nozzle with a length equal to thenozzle length and a height equal to the ice load height h givenby:

h = 0.8 hice in general = 0.6 hice for nozzle directly inside of protecting struc-

tures, e.g. other nozzle or propeller.

402 The following two alternative longitudinal ice load areasare to be considered:

— an area positioned at the lower edge of the nozzle with awidth equal to 0.65 D and a height equal to the height ofthe nozzle profile

— an area on both sides of the nozzle at the propeller shaftlevel, with a transverse width equal to the height of thenozzle profile and with a height equal to 0.35 D. Bothsymmetric and asymmetric loading are to be checked.

D = nozzle diameter.

403 The design ice pressure p (in kN/m2) for the stern areaas given in D400 is to be assumed for the ice load areas speci-fied under 401 and 402 giving rise to a force (F) given by:

F = k p A (kN)

A = ice load area as defined in 401 and 402k = 0.7 in general = 1.0 for vessels with class notations POLAR or Ice-

breaker.

G 500 Propeller nozzle scantlings501 The scantlings of the propeller nozzle and its supports inthe hull are to be calculated for the ice loads given in 400, withstresses not exceeding allowable values given in F400. Fornozzle plating the ice load thickness is to be taken as given inF200 using the design ice pressure as given for the stern area.

G 600 Steering gear601 The main steering gear is to be capable of putting therudder over from 35° on one side to 30° on the other side in 20

seconds, when the vessel is running ahead at maximum servicespeed (corresponding to MCR) and at deepest ice draught.

602 For the additional class notation Icebreaker the abovetime is not to exceed 15 seconds.

603 The effective holding torque of the rudder actuator, atsafety valve set pressure, is to be capable of holding the rudderin the preset position, when backing in ice, unless arranged inaccordance with 302 and 604.

The holding torque means the rudder torque the actuator is ca-pable to withstand before the safety valve discharges.

The holding torque need normally not exceed the values givenin Table G1.

MTR = as given in 201.

604 The torque relief arrangement, when installed, shall pro-vide protection against excessive rudder ice peak torque, e.g.when backing towards ice ridges.

The arrangement is to be such that steering capability is eithermaintained or speedily regained after activation of such ar-rangement.

605 All hydraulic rudder actuators are to be protected bymeans of relief valves. Discharge capacity at set pressure is notto be less than given in Table G2.

606 Where practicable rudder stoppers working on the rud-der blade or head are to be fitted.

H. Welding

H 100 General101 The requirements in this subsection apply to membersthat may be directly exposed to local ice pressure and supportstructures for these. Otherwise weld dimensions are to be in ac-cordance with the rules for main class.

H 200 External welding201 The welding of ice strengthened external plating to stiff-eners and to webs and bulkheads fitted in lieu of stiffeners is inany case to have a double continuous weld with throat thick-ness which is not less than:

σ = 210 fwfw = material factor for weld deposit

=

σ fw = yield strength in N/mm2 of weld deposit.

H 300 Fillet welds and penetration welds subject to high stresses301 In structural parts where high tensile stresses due to localice load act through an intermediate plate, the throat thicknessof double continuous welds is not to be less than given by Pt.3

Table G1 Values of holding torqueICE-05 to -15 POLAR-10 to -30 Icebreaker

0.5 MTR 0.75 MTR MTR

Table G2 Relief valve discharge capacityICE-05 to -15 POLAR-10 to

-30Icebreaker

Rudder speed (degrees/s)

4.5 5 6.5

t0.75 s po

σ------------------------- 0.5tk (mm)+=

σfw

235---------

0.75

DET NORSKE VERITAS


Ch.1 Sec.12 C202, with σ = 0.77 σi.

σi = calculated maximum tensile stress in abutting plate dueto ice load in N/mm2.

302 Where high shear stresses in web plates due to local iceload, double continuous boundary fillet welds are to havethroat thickness not less than given by Pt.3 Ch.1 Sec.12 C302with τ = 0.77 τi.

τi = calculated maximum shear stress due to ice load in N/mm2.

I. Machinery Systems

I 100 Pneumatic starting arrangement101 In addition to the requirements given in Pt.4 Ch.6 Sec.5for a vessel having a propulsion engine(s), which has to be re-versed for going astern, the compressors are to have the capac-ity to charge the receivers in half an hour.

I 200 Sea inlets and discharges201 The sea cooling water inlet and discharge for main andauxiliary engines is to be so arranged that blockage of strumsand strainers by ice is prevented.

In addition, the requirements in Pt.4 Ch.6 Sec.5 B302 andB303 are to be complied with.

202 At least one of the sea chests is to be sufficiently high toallow ice to accumulate above the pump suctions and coolingwater tank inlet, arranged as follows:

1) The sea inlet is to be situated near the centre line of theship and well aft if possible. The inlet grids are to be spe-cially strengthened.

2) As a guidance for design the volume of the chest is to beabout one cubic metre for every 750 kW engine output ofthe ship including the output of the auxiliary engines nec-essary for the ship's service.

3) To allow for ice accumulation above the pump suction theheight of the sea chest is not to be less than:

Vs =volume of sea chest according to item 2.The suction pipe inlet is to be located not higher than hmin/3 from top of sea chest.

4) The area of the strum holes is to be not less than four (4)times the inlet pipe sectional area.

Heating coils may be installed in the upper part of the chests.

203 A full capacity discharge branched off from the coolingwater overboard discharge line is to be connected to the seachests. At least one of the fire pumps is to be connected to thissea chest or to another sea chest with de-icing arrangement.

I 300 Sea cooling water arrangements301 The sea cooling water inlets and discharges for main andauxiliary engines are to be connected to a cooling water doublebottom tank having direct supply from the sea chests. Thecross-sectional area of the supply line between each sea chestand the cooling water tank is to be twice that of all pump suc-tions connected to the tank.

302 Vessels with the class notation Icebreaker or POLARare to comply with 303 to 307.

303 The cooling water tank volume in m3 is to be at least0.01 times the output in kW of the main and auxiliary engines.

304 The sea water suction line strainers required in Pt.4 Ch.6

Sec.5 are to be arranged outstream from the cooling water tank.

305 The sea water cooling pumps are to be of the self-prim-ing type or connected to a central priming system.

306 The sea water cooling and ballast piping is to be ar-ranged so that water in the cooling water tank can be circulatedthrough the ballast tanks for the purpose of spare cooling ca-pacity in the case of blocked sea chests.

307 Arrangements providing additional cooling capacityequivalent to that specified in 301 through 306 may be consid-ered.

I 400 Ballast system401 Arrangement to prevent freezing is to be provided forballast tanks where found necessary.

Guidance note:Double bottom tanks are normally not required to be providedwith arrangement to prevent freezing.


J. Propulsion Machinery and Propellers

J 100 General101 Special cold climate environmental conditions are to betaken into consideration in machinery design.

102 In general, materials used in propellers, propeller shaftsand other components exposed to sea temperature are subjectto Charpy V-notch impact testing at —10°C. The impact ener-gy is not to be less than 4/5 of that required at 20°C, minimum20 J.

103 Grey cast iron is normally not accepted for componentssubject to ice shocks, as e.g. thrust bearing housings.

104 Shafting systems equipped with specially designed me-chanical torque limiting devices are subject to special consid-eration. Such devices, when accepted, are to comply withredundancy type R2 in Pt.4 Ch.1 Sec.1 B108.

The torque limit is normally not less than 1.5 KA TO .

For KA and TO, see 500.

105 Ice induced vibrations (repetitive ice chocks) in theshafting system are to be considered.

Forced torsional vibration calculations are to include an evalu-ation of transient vibrations excited by ice on the propeller.

106 For non-reversible machinery plants, special means areto be provided for reversing the propellers stuck in ice.

J 200 Engine output201 The maximum continuous output of propulsion machin-ery is not to be less than:

P = 1.5 cs cp I N B [ 1 + 1.6 T + 27 (0.1 I N / T0.25)0.5 ] (kW)

cs = 1.0 for vessels with conventional «icebreaker stem» = 0.9 + γ / 200; minimum 1.0, but need not exceed 1.2cp = 1.0 for controllable pitch propeller = 1.1 for fixed pitch propellerIN = ice class number (figure added to class notation)B = moulded breadth at waterline (m), local increase in

way of stem area is normally not to be taken into ac-count

T = rule draught (m)γ = stem angle (see Fig.2).

202 When the vessel is provided with special means whichwill improve her performance in ice (e.g. air bubbling system),the input rating of machinery used for such purpose may beadded to the actual rating of propulsion machinery.

hmin 1.5 Vs3≥

DET NORSKE VERITAS


The propeller rating is, however, not to be less than 85% of thatrequired in 201.

203 When the vessel is provided with a nozzle of efficientdesign, a reduction of required engine output corresponding toincrease of thrust in ice conditions will be considered. The re-duction is, however, not to exceed 20% of required output in201 and 202.

204 Additional reduction of the required output may be con-sidered for a vessel having design features improving her per-formance in ice conditions. Such features are to bedocumented, either by means of model tests or full scale meas-urements.

It is understood that such approval can be revoked, if experi-ence motivates it.

J 300 Determination of ice torque

301 Ice torque (TICE), used for determination of scantlings inpropellers and shafting systems, is to be taken as follows:

TICE = m D2 (kNm)

The factor m is given in Table J1 as function of ice class:

D = propeller diameter in m.

302 For propellers running in nozzles of satisfactory design,the ice torque will be considered based on on submitted docu-mentation, e.g. measurements carried out on similar vessels.

However, if nothing else is documented, the following may beused:

TICE = (0.9 - 0.01 m D-0.5) m D2 (kNm)

Large fragments of ice are not to have free access into or to-wards the front of the nozzle.

J 400 Propeller

401 The blade scantling requirements given in Sec.3 apply,except as given below. In calculations involving the ice torque,TICE according to 300 is to be applied.

Propeller blade scantlings of martensitic — austenitic and fer-ritic — martensitic stainless steel may be specially considered.

402 Arrangement of propellers in ice classes ICE-15 andPOLAR-10 to -30 is to be such that large fragments of ice donot have free access into the front of the propeller disc within0.7 radius.

403 The blade tip thickness at the radius 0.95 R is not to beless than:

D and σb as given in 404.

σb is not to be taken higher than 2.5 σy.

For propellers running in nozzles blade tip thickness smallerthan above may be accepted. The tip thickness, however, is notto be less than 3/4 of the above value.

The thickness at the blade edges and the tip to be as determinedin Sec.3.

404 The fitting of the propeller blades and the pitch controlmechanism is to withstand a design static load not less than:

This load is to be applied on the blade at a radius 0.9 R and atan offset from blade centre axis of 2/3 le.

σn = 0.37 σb + 0.6 σyσb = ultimate tensile strength of the blade (N/mm2)σy = the blade yield stress or 0.2% offset point (N/mm2)cr = the length of the blade section at RR radius (mm)tr = the corresponding thickness (mm)D = propeller diameter (m)R = D/2 (m)RR = radius to a blade section taken at the termination of the

blade root fillet (rounded upwards to the nearest R/20),ref. cr and tr (m)

le = distance from axis of rotation of the blade to the lead-ing or trailing edge, whichever is the greater, at a radi-us of 0.9 R.

405 Propeller blade bolts are to have a section modulus, re-ferred to an axis tangential to the bolt pitch diameter, not lessthan:

S = 1.0 for CP-propellers = 1.25 for FP-propellersσy = yield stress of bolt material (N/mm2)RB = radius to bolt plan (m).

cr, tr and σn as given in 404.

The bolts are to have a design which minimises stress concen-trations in transition zones to threads and bolt head as well asin way of the threads, and reduces risk for plastic deformationsin the threads.

406 For all parts in the pitch control mechanism, which aresubject to variable ice loads, stress concentration is to be takeninto consideration.

407 The blade fitting and other parts in the pitch controlmechanism are to be designed to withstand all forces producedby the pitch control system at its maximum power. The forcesare to be assumed to act towards one blade at a time.

Guidance note:The pitch control mechanism shall be designed for the followingdynamic ice loads:

applied at the 0.9 radius perpendicular to the blade plane at therespective blade edges.Number of load cycles to be considered shall not be taken lessthan one million for ice classes ICE-05 to -15 and infinitive forPOLAR-10 to -30 and class notation Icebreaker. The designpressure of the hydraulic system shall not be taken less than twicethe pressure needed to produce the blade spindle torque based onthe above forces. The forces are assumed to act on one blade at atime only.


J 500 Shafting501 Symbols:

P = rated power (kW)np = propeller speed (rpm) at a rated power

Table J1 Values of mIce class m Icebreaker mICE-05 16 ICE-05 21ICE-10 21 ICE-10 30ICE-15 27 ICE-15 30POLAR 33 POLAR 40

t m 2D+( ) 490σb--------- (mm)=

FLE = TICE / 0.9 R (kN) at leading edge,F TE = - 0.5 FLE at trailing edge,

FICE 0.3σncrtr

2

D 0.9 RR R⁄–[ ]---------------------------------------10

6– (kN)=

WBS 0= .15 S cr tr2 σn

σy------

0.9 RB R⁄–

0.9 RR R⁄–----------------------------- mm

3( )

DET NORSKE VERITAS


TO = torque (kNm) in the actual componentTICE = ice torque (kNm) according to 300D = propeller diameter (m)u = gear ratio (if no reduction gear, or for components on

the propeller side of a reduction gear use u = 1)I = mass moment of inertia (kgm2) (referred to propeller

speed) of all rotating masses *) on the engine side ofthe actual component

IT = mass moment of inertia (kgm2) (referred to propellerspeed) of the entire *) rotating mass system

d = shaft diameter (mm)f = 560 / (σb + 160) material factorσb = ultimate tensile stress (N/mm2) of the shafting materialσy = yield or 0.2% proof stress of the shafting material

(N/mm2)σn = according to 404.

*) The system is «cut» in a hydrodynamic coupling, i.e. allmasses on the engine side of such a coupling are disregarded.

502 Application factor for diesel/turbine machinery:

503 Application factor for electric motor machinery or dieselmachinery with hydrodynamic torque converter:

1) Diesel engine with torque converter:

TTC max = transmitted torque through converter.

2) Electro motor drive:

Tmax = motor peak torque (steady state condition).

For electric motor machinery analysis of KA by means ofshock simulation technique is in general advised.

504 As an upper limit as well as substitute in lack of suffi-cient data of the plant, the following application factor may beused:

CA = 8.0 for diesel machinery with hydrodynamic coupling = 24 for diesel and turbine machinery = 32 for electric motor or diesel with hydrodynamic

torque converter to be specially consideredm = as given in 301.

For nozzle propellers the factor m may be reduced in accord-ance with 302.

Guidance note:The application factor KA, calculated from 504, is normally to beused in the predesign phase only. It is based on conservative as-sumptions of the mass relations and propeller diameter. Accord-ingly KA is normally exceeding considerably the KA-valuescalculated according to 502 and 503.


505 The diameter of the propeller shaft in way of aft bearingand at least a length 2.5 times the required diameter forward ofpropeller flange or hub, is not to be less than:

cr t2 = actual value of blade section considered at the termina-tion of the blade root fillet (rounded upwards to nearest1/20 of R).

σy refers to the shaft material.

σn refers to the blade material, see 404.

cr and t as given in 404.

The propeller shaft diameter may be evenly tapered to 1.15times the required intermediate shaft diameter between the aftbearing and the second aft bearing. Forward of this bearing thepropeller shaft diameter may be reduced to 1.05 times the re-quired diameter of the intermediate shaft (using material factorvalid for propeller shaft).

The propeller shaft flange thickness (propeller fitting) is to beat least 0.3 times the actual shaft diameter. The fillet radius isto be at least 0.125 times the actual shaft diameter.

506 The diameter of the intermediate shaft is not to be lessthan:

k = as given in Pt.4 Ch.4 Sec.1.

J 600 Thrust bearing601 Support and construction of the thrust bearing is to bedesigned to avoid excessive axial shaft movements caused byheavy axial forces when the propeller hits ice.

602 The thrust bearing shall have static strength designed fornot less than the nominal thrust plus the static ice force as de-fined in 404. The ice force is assumed to act in the axial direc-tion. Both forward and astern directions are to be considered.

603 The basic static load ratings of roller bearings are not tobe less than 2 times the load according to 602.

604 For calculation of the bearing pressures in the ice condi-tions, the following thrust force applies:

T HI = 1.1 TH + 0.25 FLE ± 0.75 FLE (kN)

F LE = according to 407TH = mean «bollard thrust» of the propeller or 1.25 times the

mean thrust at maximum continuous ahead speed, inkN.

605 Calculated lifetime (B10) of roller bearings is to be min-imum 40 000 h, by applying the load THI.

J 700 Reduction gear 701 The reduction gear is to meet the requirements in Pt.4Ch.4 Sec.2, utilizing the application factor KA in accordancewith 500.

702 Axial ice load according to 600, when applicable, is tobe considered with respect to bearing arrangement and stiff-ness of the gear housing.

J 800 Flexible couplings and clutches801 Clutches and flexible couplings are to be designed towithstand a torque of:

1.2 TO KA

without slipping or imposing excessive loading on the shaftingby reaching twist limits, or reaching the approved permissibleimpact torque of the elastic coupling.

KA 1TICE I

uTOIT----------------+=

KA 1TiceI

uT0It-------------

TTCmax

T0-------------------≤+=

KA

Tmax

TO------------

TICE I

uTOIT----------------+=

KA 1CAm

p0.6

np0.2

----------------------+=

dp 1.160.9σncrt

2

0.9 RR R⁄( )–[ ]σy---------------------------------------------

13---

(mm)=

dm 90kP f KA

npu----------------

13---

(mm)=

DET NORSKE VERITAS


802 The couplings are to withstand a low frequency ampli-tude:

0.5 (KA – 1) TO

at an average torque of:

0.5 TO (KA + 1)

which is not to exceed an approved nominal coupling torque.

J 900 Fixed shaft couplings

901 Shrink fit couplings are to have a safety against frictionslip of minimum 1.5. Both torque and axial force componentsare to be considered.

902 For calculation of torque and axial force components thefollowing applies:

T = TO KA (torque)

F = TH + 1.5 FLE (axial load, ahead)

F = 0.8 TH + FLE (axial load, astern)

The axial load F is to be applied on the propeller side of thethrust bearing.

TH and FLE according to 600 and 400.

KA is given in 502 to 504.

903 Key connections are to be able to transmit a torque:

T = 1.2 TO KA

without yielding.

J 1000 Propeller fitting

1001 Propeller fitting is to comply with the requirements in900 applying sea water temperature 0°C and safety factor 1.8.Maximum permissible stresses are to be in accordance withPt.4 Ch.5 Sec.1.

1002 A strong locking device is to be fitted on the propellernut.

1003 If the propeller is bolted to the propeller shaft, the boltconnection is to have at least the same bending strength as thepropeller shaft.

J 1100 Spare parts

1101 For single propulsion plants, a spare set of rubber ele-ments for each type of elastic coupling in the propulsion shaftline is to be kept onboard.

K. Thrusters

K 100 General

101 The following requirements apply to auxiliary thrusters.Azimuth thrusters, which are used for propulsion purpose, areto comply with the relevant requirements in J.

102 Steering gear for azimuth thrusters is to be designed towithstand all relevant ice loads. Both ice loads on propellernozzle (G400) and on propeller blade (J400) are to be consid-ered.

103 Special cold climate environmental conditions are to betaken into consideration in the thruster design.

104 In general, materials used in propellers, shafting andstructural parts exposed to sea water are subject to Charpy V-notch impact testing at –10°C. The impact energy is not to beless than 4/5 of that required at 20°C, minimum 20 J.

105 Means for heating and circulation of lubrication and hy-draulic oil are to be provided.

106 Requirements in Pt.4 Ch.5 Sec.3 apply with exceptions

and additional requirements given here.

K 200 Shafting

201 Maximum peak torque, which may occur due to ice inthe propeller, is to be taken into consideration.

202 The load F in 401 is to be considered for the propellershaft.

Maximum permissible equivalent stress is 80% of the yieldstress or 0.2% proof stress of materials.

K 300 Reduction gear

301 Application factor (KA) is to be taken as minimum 1.2.

K 400 Propeller

401 The propeller blade is to be designed to withstand a peakload, without exceeding 80% of blade material yield or 0.2%proof stress of:

T = maximum peak torque of prime mover (kNm)α0.85 = pitch angle at radius 0.85 RR = propeller radius (m).

The load F is assumed to apply at 0.85 R, perpendicular to theblade plane.

L. Stability and Watertight Integrity

L 100 Application

101 Vessels with class notation Icebreaker or POLAR areto comply with the requirements of Pt.3 Ch.3 Sec.9 as well asthe requirements of this subsection.

102 Definitions and general requirements related to damagestability approval for passenger ships are to be applied as far asapplicable.

L 200 Definitions

201 Symbols

Pzb =vertical beaching force, see D200.

202 Terms

Beaching lever = beaching moment divided by the vessel's dis-placement.

203 More definitions are given in Pt.3 Ch.3 Sec.9 A.

L 300 Documentation

301 Documentation for approval

— preliminary damage stability calculations— final damage stability calculations

(not required in case of approved limit curves, or if ap-proved lightweight data are not less favourable than esti-mated lightweight data).

302 Documentation for information

— internal watertight integrity plan.

303 Details of above documentation are given in Classifica-tion Note No. 20.1.

L 400 Requirements for intact stability

401 The initial metacentric height GM is not to be less than0.5 m.

FT

0.85R α0.85sin------------------------------------- (kN)=

DET NORSKE VERITAS


L 500 Requirements for damage stability501 The damage assumptions in 502 to 506 and the criteriain 507 and 508 are to be the basis of damage stability calcula-tions.

502 Maximum extent of side damage is given by:

503 Maximum extent of bottom damage is given by:

504 If damage of lesser extent than that specified above re-sults in a more severe condition, such lesser extent is to be as-sumed.

505 For pipes, ducts or tunnels situated within the assumedextent of damage, see 700.

506 The following permeability factors are to be assumed:

507 Damage criteria at the final stage of flooding:

— the final equilibrium waterline after damage is to be belowthe edge of any non-watertight opening

— the final equilibrium heel angle after damage is not to ex-ceed 15°. This may be increased to 17° if the deck edge isnot submerged

— residual stability criteria at final stage

— GZ after damage has at least 20° positive range be-yond equilibrium

— maximum GZ of at least 0.10 m within 20° beyond themaximum equilibrium position.

508 Damage criteria at the intermediate stages of flooding:

— the waterline after damage is to be below the edge of anynon-weathertight opening

— the heel angle after damage is not to exceed 25°. This maybe increased to 30° if the deck edge is not submerged

— residual stability criteria at intermediate stages

— GZ after damage has at least 10° positive range be-yond equilibrium

— maximum GZ of at least 0.05 m within 10° beyond themaximum equilibrium position.

509 A maximum allowable VCG curve with respect to dam-age stability is to be included in the stability manual. Other-wise the damage stability approval shall be limited to thepresented loading conditions.

L 600 Requirements for beaching stability

601 The vessel's stability is to be assessed when beaching ona large ice feature, assuming maximum allowable VCG. Theassumptions in 602 and 603 and criteria in 604 and 605 are tobe the basis of such assessment.

602 Centric beaching assumption:

The vertical beaching force PZB in D200 is to be assumed atthe F.P., 1.0 m below the waterline, at the longitudinal centreline of the vessel.

603 Eccentric beaching assumption:

The vertical beaching force PZB in D200 is to be assumed atthe F.P., 1.0 m below the waterline, 0.125 B off the longitudi-nal centre line of the vessel.

604 Centric beaching criteria:

— the GM is to be positive— the aft deck edge is not to be submerged.

However, for vessels built with an ice knife positioned in sucha way that the aft deck edge can not be submerged, the lattercriterion does not need to be considered.

605 Eccentric beaching criteria:

— the GM is to be positive— the beaching lever, calculated as 0.125 B x PZB/displace-

ment, is not to exceed 0.5 times the maximum GZ.

L 700 Requirements to watertight integrity

701 As far as practicable, tunnels, ducts or pipes which maycause progressive flooding in case of damage, are to be avoid-ed in the damage penetration zone. If this is not possible, ar-rangements are to be made to prevent progressive flooding tovolumes assumed intact. Alternatively, these volumes are to beassumed flooded in the damage stability calculations.

702 The scantlings of tunnels, ducts, pipes, doors, staircases,bulkheads and decks, forming watertight boundaries, are to beadequate to withstand pressure heights corresponding to thedeepest equilibrium waterline in damaged condition.

– longitudinal: 1/3 L2 /3 or 14.5 m whichever is less– vertical: 3.00 m– transverse: 1.50 m.

– longitudinal: 5.00 m– transverse: 3.00 m– vertical: 0.76 m.

– store rooms: 0.60– machinery spaces: 0.85– tanks and other spaces: 0.95– partially filled ballast tanks: consistent with minimum

tank content.

DET NORSKE VERITAS


SECTION 5SEALERS

A. General

A 100 Classification101 The requirements in this Section apply to vessels spe-cially built for catching.

102 Vessels built in compliance with the following require-ments may be given the class notation Sealer.

A 200 Hull form201 The hull form of the vessel is to be suitable for naviga-tion in pack ice and is to be such that the ship cannot be presseddown by ice. The sides of the hull are to be convex, with thegreatest breadth at the first continuous deck above the designwaterline. The angle between the tangent to the ship's side atthe deck and the vertical is not to be less than 5 degrees.

B. Strength of Hull and Superstructures

B 100 Ship's sides and stem101 The scantlings of shell plating, frames, girders and stemare at least to be as required for ice class ICE–05, see Sec.4.

B 200 Superstructures201 Side plating in superstructures is to have increasedthickness in an area extending not less than 1 m above the loadwaterline of the vessel or above deck if the vessel has no free-board mark. In the mentioned area the plate thickness forwardof 0.25 L from F.P. is not to be less than:

t = 10 + 0.08 L (mm)

Aft of 0.25 L from F.P. the plate thickness is not to be less than:

t = 7.5 + 0.06 L (mm)

202 Frames in superstructures in way of crew accommoda-tion are to have a section modulus at least 50% in excess of therequirement for main class. The frames are to have brackets atboth ends.

203 Intermediate frames with section modulus as for framesaccording to 202, are to be fitted in way of the strengthened

side plating stated in 201. The top of intermediate frames is tobe connected to a horizontal girder of same depth as the framesand with a flange area not less than 10 cm2. The horizontalgirder is to be attached to all side frames.

C. Sternframe, Rudder and Steering Gear

C 100 Design rudder force101 The scantlings are to be based on a rudder force 3 timesthe design rudder force for main class.

C 200 Protection of rudder and propeller201 Ice fins are to be fitted for protecting rudder and propel-ler.

D. Anchoring and Mooring Equipment

D 100 General101 The equipment may be as required for fishing vessels.

E. Machinery

E 100 Output of propulsion machinery101 The output is not to be less than 735 kW. If the vessel hasa controllable pitch propeller, the output requirement may bereduced by 10%.

E 200 Thrust bearing, reduction gear, shafting and pro-peller201 The scantlings are at least to be as required for class no-tation ICE–05, see Sec.4.

E 300 Machinery systems301 For requirements to sea inlets and cooling water system,see Sec.3 J602.

DET NORSKE VERITAS

DNV Ship rules Pt.5 Ch.1 - Ships for Navigation in Ice

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Transcript of DNV Ship rules Pt.5 Ch.1 - Ships for Navigation in Ice