SHIPS FOR NAVIGATION IN ICE

Transcription

1 RULES FOR CLASSIFICATION OF SHIPS NEWBUILDINGS SPECIAL SERVICE AND TYPE ADDITIONAL CLASS PART 5 CHAPTER 1 SHIPS FOR NAVIGATION IN ICE JANUARY 2003 CONTENTS PAGE Sec. 1 General Requirements... 5 Sec. 2 Basic Ice Strengthening... 6 Sec. 3 Ice Strengthening for the Northern Baltic...8 Sec. 4 Vessels for Arctic and Ice Breaking Service Sec. 5 Sealers 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. Veritasveien 1, N-1322 Høvik, Norway Tel.: Fax:

2 CHANGES IN THE RULES General The present edition of the rules includes additions and amendments decided by the Board in March 2003 and supersedes the January 2001 edition of the same chapter. The rule changes come into force 1 July This chapter is valid until superseded by a revised chapter. Supplements will not be issued except for minor amendments and an updated list of corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 is normally revised in January and July each year. Revised chapters will be forwarded to all subscribers to the rules. Buyers of reprints are advised to check the updated list of rule chapters 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, published in Bulletin No. 13/ from the Finnish Maritime Administration (FMA). The new Finnish-Swedish Ice Class Rules entered into force on 1 October 2002 and will be applied to ships of which the keel is laid or which is at similar stage of construction on or after 1 September The new rules contain new minimum output requirements for propulsion for the Ice Classes: ICE-1C and ICE-1B based on ship s resistance in channels with brash ice, which was introduced 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/ give the minimum engine output in the Class Certificate, this has also been included into these rules. Structural strength requirements have also been amended, resulting in a slightly thicker ice belt for longitudinally framed ships. In addition, DNV have included an amendment where frames perpendicular to the shell, which are of unsymmetrical profiles, are to have tripping preventions at a distance not exceeding 2.6 meters (not included in FMA amendments). Item J304 has been amended to take into account the difference in the material factor between stainless steel and other materials. Corrections and Clarifications In addition to the above stated rule requirements, a number of detected errors, corrections and clarifications have been made in the existing rule text. Comments to the rules may be sent by to rules@dnv.com For subscription orders or information about subscription terms, please use distribution@dnv.com Comprehensive information about DNV and the Society's services is found at the Web site Det Norske Veritas Computer Typesetting (FM+SGML) by Det Norske Veritas Printed in Norway If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas.

3 Pt.5 Ch.1 Contents Page 3 CONTENTS SEC. 1 GENERAL REQUIREMENTS... 5 A. Classification...5 A 100 Application...5 A 200 Class notations...5 B. Definitions...5 B 100 Symbols...5 B 200 Terms...5 C. Documentation...5 C 100 General...5 SEC. 2 BASIC ICE STRENGTHENING... 6 A. General...6 A 100 Classification...6 B. Hull Arrangement and Scantlings...6 B 100 Shell plating...6 B 200 Ordinary frames...6 B 300 Intermediate ice frames...6 B 400 Ice stringer...6 B 500 Weld connections...6 B 600 Sternframe and rudder...6 C. Machinery...7 C 100 Output of propulsion machinery...7 C 200 Design of propeller and propeller shaft...7 C 300 Sea suctions and discharges...7 SEC. 3 ICE STRENGTHENING FOR THE NORTHERN BALTIC... 8 A. General...8 A 100 Classification...8 A 200 Assumptions...8 A 300 Definitions...8 A 400 Documentation...8 B. Design Loads...9 B 100 Height of load area...9 B 200 Ice pressure...9 C. Shell Plating...9 C 100 Vertical extension of ice strengthening...9 C 200 Plate thickness in the ice belt...10 D. Frames...10 D 100 Vertical extension of ice framing...10 D 200 Transverse frames...10 D 300 Longitudinal frames...11 D 400 Structural details...11 E. Ice Stringers...12 E 100 Stringers within the ice belt...12 E 200 Stringers outside the ice belt...12 E 300 Deck strips...12 F. Web Frames...12 F 100 Design load...12 F 200 Section modulus and shear area...12 G. Bilge Keels...13 G 100 Arrangement...13 H. Special Arrangement and Strengthening Forward...13 H 100 Stem, baltic ice strengthening...13 H 200 Arrangements for towing...13 I. Special Arrangement and Strengthening Aft...14 I 100 Stern...14 I 200 Rudder and steering arrangements...14 J. Machinery...14 J 100 Engine output...14 J 200 Design loads for propeller and shafting...16 J 300 Propeller...16 J 400 Shafting...17 J 500 Thrust bearing and reduction gear...17 J 600 Miscellaneous machinery requirements...18 SEC. 4 VESSELS FOR ARCTIC AND ICE BREAKING SERVICE A. General A 100 Classification...19 A 200 Scope...19 A 300 Design principles and assumptions...19 A 400 Definitions...20 A 500 Documentation...21 B. Materials and Corrosion Protection B 100 Design temperatures...22 B 200 Structural categories...23 B 300 Selection of steel grades...23 B 400 Coatings...24 B 500 Corrosion additions...24 B 600 Equipment...24 C. Ship Design and Arrangement C 100 Hull form...24 C 200 Appendages...24 C 300 Mooring equipment...24 D. Design Loads D 100 Ice impact forces on the bow...24 D 200 Beaching forces...25 D 300 Ice compression loads amidships...25 D 400 Local ice pressure...25 D 500 Accelerations...26 E. Global Strength E 100 General...26 E 200 Longitudinal strength...26 E 300 Transverse strength amidships...27 E 400 Overall strength of substructure in the foreship...27 F. Local Strength F 100 General...28 F 200 Plating...28 F 300 Longitudinal stiffeners...28 F 400 Other stiffeners...29 F 500 Girders...29 G. Rudders, Propeller Nozzles and Steering Gears G 100 General...30 G 200 Ice loads on rudders...30 G 300 Rudder scantlings...31 G 400 Ice loads on propeller nozzles...31 G 500 Propeller nozzle scantlings...31 G 600 Steering gear...31 H. Welding H 100 General...31 H 200 External welding...31 H 300 Fillet welds and penetration welds subject to high stresses...31 I. Machinery Systems I 100 Pneumatic starting arrangement...32 I 200 Sea inlets and discharges...32 I 300 Sea cooling water arrangements...32 I 400 Ballast system...32 J. Propulsion Machinery and Propellers J 100 General...32 J 200 Engine output...32 J 300 Determination of ice torque...33 J 400 Propeller...33 J 500 Shafting...33 J 600 Thrust bearing...34 J 700 Reduction gear...34

4 Pt.5 Ch.1 Contents Page 4 J 800 Flexible couplings and clutches...34 J 900 Fixed shaft couplings...35 J 1000 Propeller fitting...35 J 1100 Spare parts...35 K. Thrusters...35 K 100 General...35 K 200 Shafting...35 K 300 Reduction gear...35 K 400 Propeller...35 L. Stability and Watertight Integrity L 100 Application...35 L 200 Definitions...35 L 300 Documentation...35 L 400 Requirements for intact stability...35 L 500 Requirements for damage stability...36 L 600 Requirements for beaching stability...36 L 700 Requirements to watertight integrity...36 SEC. 5 SEALERS A. General...37 A 100 Classification...37 A 200 Hull form...37 B. Strength of Hull and Superstructures...37 B 100 Ship's sides and stem...37 B 200 Superstructures...37 C. Sternframe, Rudder and Steering Gear...37 C 100 Design rudder force...37 C 200 Protection of rudder and propeller...37 D. Anchoring and Mooring Equipment...37 D 100 General...37 E. Machinery...37 E 100 Output of propulsion machinery...37 E 200 Thrust bearing, reduction gear, shafting and propeller...37 E 300 Machinery systems...37

5 Pt.5 Ch.1 Sec.1 Page 5 SECTION 1 GENERAL REQUIREMENTS A. Classification A 100 Application 101 The rules in this chapter apply to vessels occasionally or primarily intended for navigation in waters with ice conditions. The requirements are to be regarded as supplementary to those given for the assignment of main class. A 200 Class notations 201 Vessels complying with relevant additional requirements of this chapter will be assigned one of the following class notations: Table A1 Class notations Notation ICE-C ICE-1A*F ICE-1A* ICE-1A ICE-1B ICE-1C ICE - 05(or - 10 or - 15) POLAR - 10(or - 20 or - 30) Icebreaker Sealer Reference (See Sec.2) (See Sec.3) (See Sec.4) (See Sec.5) B. Definitions B 100 Symbols 101 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 *) C B block coefficient *) f displacement in t in fresh water (density 1.0 t/m 3 ) at ice class draught P s s s 0 s s l S maximum continuous output of propulsion machinery in kw stiffener spacing in m measured along the plating between ordinary and/or intermediate stiffeners spacing in m of ordinary main frames L (m) maximum 0.61 m forward of the collision bulkhead and abaft the afterpeak bulkhead stiffener span in m measured along the top flange of the member. For definition of span point, see Pt.3 Ch.1 Sec.3 C100 girder span in m. For definition of span point, see Pt.3 Ch.1 Sec.3 C100. σ F minimum upper yield stress of material in N/mm 2 NV-NS-steel may be taken as having σ F 235 N/mm 2 g 0 standard acceleration of gravity ( 9.81 m / s 2 ). *) For details see Pt.3 Ch.1. B 200 Terms 201 Load waterline, LWL: The waterline corresponding to winter load line. For ships trading in the Baltic during winter at summer load line, the ice strengthening is to be based on the summer load line, see also Sec.3 A 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, arrangement and strength are in general to be included in the plans specified for the main class. 102 Additional documentation not covered by the main class are specified in appropriate sections of this chapter.

6 Pt.5 Ch.1 Sec.2 Page 6 SECTION 2 BASIC ICE STRENGTHENING A. General A 100 Classification 101 The requirements in this section apply to passenger and cargo vessels intended for service in waters with light ice conditions. 102 Vessels built in compliance with the following requirements 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 applied. 104 Vessels with longitudinal framing are to have scantlings for plating and longitudinals as for class notation ICE-1C, using 0.9 times the ice pressure as given in Sec.3. The extent of ice 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 extending vertically from 0.5 m above LWL to 0.5 m below BWL, the shell plating thickness is not to be less than: t L + t (mm), maximum 25 mm L 2 abaft collision bulkhead: Z (cm 3 ) 160 L 2 The required section modulus of intermediate frames forward of the collision bulkhead is based on a frame span equal to 2 m. For different spans, the requirement is modified in direct proportion. Intermediate frames need in no case have a section modulus larger than 75% of that of the ordinary frames. 303 The ends of intermediate ice frames are to be connected to horizontal carlings between ordinary frames. These carlings are not to form a continuous stringer. Where intermediate ice frames extend to a deck or inner bottom, it may have sniped ends. Acceptable types of intermediate frame ends are shown in Fig. 1. s o s s s o Z (cm 3 ) 100 s s t 20 (s o s s ) (mm), minimum zero. 102 Abaft the area mentioned in 101, the shell plating thickness within the specified ice belt may be gradually reduced to normal thickness at the position where the waterlines attain their full breadth. B 200 Ordinary frames 201 Ordinary frames in fore peak are to have a section modulus not less than: Z 0.25 L T (cm 3 ) The distance between ordinary frames in fore peak is not to exceed 0.61 m. 202 From collision bulkhead to 1.5 B abaft F.P., the section modulus of ordinary main frames is not to be less than: Z 0.4 L s o T (cm 3 ) B 300 Intermediate ice frames 301 In the region from stem to 1.5 B abaft F.P., intermediate frames are to be fitted. The intermediate ice frames are to extend from 0.62 m above LWL to 1.0 m below BWL. Bottom plating forward situated less than 0.5 m below BWL is to have intermediate stiffening between floors. Intermediate ice frames may be omitted, if the spacing of the ordinary frames is not exceeding: 0.37 m forward of collision bulkhead ( L), maximum 0.42 m abaft collision bulkhead. 302 The intermediate ice frames are to have a section modulus not less than: forward of collision bulkhead: Fig. 1 Acceptable types of intermediate frame ends B 400 Ice stringer 401 In single deck ships, an ice stringer is to be fitted 0.2 to 0.3 m below LWL from stem to a distance 2 B abaft F.P. Forward of the collision bulkhead, the ice stringer is to be a girder with scantlings as an ordinary girder on the ship's side. Abaft the collision bulkhead, the ice stringer is to consist of a series of tripping brackets fitted to the frames. B 500 Weld connections 501 Weld connections to shell in fore peak are to be double continuous. B 600 Sternframe and rudder 601 The section modulus of sternframe, rudder horn and sole piece is to be 7.5% greater than required for the main class. 602 Scantlings of rudders, rudder stocks and rudder shafts are to be based on a rudder force 25% greater than a design value calculated according to Pt.3 Ch.3 Sec.2 D101, with k 1 k irrespective of condition, rudder profile type and arrangement.

7 Pt.5 Ch.1 Sec.2 Page 7 C. Machinery C 100 Output of propulsion machinery 101 The maximum continuous output is generally not to be less than: P s 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 not to be less than: P s 0.59 L B (kw) 102 If the ship is fitted with a controllable pitch propeller, the output may be reduced by 10%. 103 For ships with steam turbines, the astern power is not to be 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 the ice torque in Nm: T ICE R 2 for open propellers T ICE R 2 ( R -0.5 ) for ducted propellers R propeller radius (m). 202 The propeller shaft diameter need not exceed 1.05 times the rule diameter given for main class, irrespective of the dimension derived from Sec.3. C 300 Sea suctions and discharges 301 The sea cooling water inlet and discharge for main and auxiliary engines are to be so arranged so that blockage of strums and strainers by ice is prevented. In addition to requirements in Pt.4 Ch.1 and Ch.6 the requirements in 302 and 303 are to be complied with. 302 One of the sea cooling water inlet sea chests is to be situated near the centre line of the ship and well aft. At least one of the sea chests is to be sufficiently high to allow ice to accumulate above the pump suctions. 303 A full capacity discharge branched off from the cooling water overboard discharge line is to be connected to at least one of the sea inlet chests. At least one of the fire pumps is to be connected to this sea chest or to another sea chest with deicing arrangements. Guidance note: Heating coils may be installed in the upper part of the sea chest(s). Arrangement using ballast water for cooling purposes is recommended but will not be accepted as a substitute for sea inlet chest arrangement as described above. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e---

8 Pt.5 Ch.1 Sec.3 Page 8 SECTION 3 ICE STRENGTHENING FOR THE NORTHERN BALTIC A. General A 100 Classification 101 The requirements in this section apply to vessels for service in the northern Baltic in winter or areas with similar ice conditions. 102 Vessels built in compliance with the following requirements 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 corresponding classes. DNV Ice Class notation ICE-1A* ICE-1A ICE-1B ICE-1C Equivalent Finnish-Swedish Ice Class 1A Super 1A 1B 1C Revision of these rules concern propulsion power and structural strength and applies to ships of which the keel is laid, or which is at a similar stage of construction on or after 1 September e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e Vessels built in compliance with the requirements relevant for class ICE-1A* and with the additional requirements given below may acquire the class notation ICE-1A*F. Guidance note: The additional ice class ICE-1A*F is recommended applied to vessels with relatively high engine power designed for regular traffic in the northern Baltic and other relevant areas, normally operating according to rather fixed timetables irrespective of ice conditions and to a certain degree independent of ice breaker assistance. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- A 200 Assumptions 201 The method for determining the hull scantlings is based on certain assumptions concerning the nature of the ice load on the structure. These assumptions rest on full scale observations made in the northern Baltic. 202 The formulae given for plating, stiffeners and girders are based on special investigations as to the distribution of ice loads from plating to stiffeners and girders as well as redistribution of loads on stiffeners and girders. Special values have been given for distribution factors and certain assumptions have been made regarding boundary conditions. 203 For the formulae and values given in this section for the determination of the hull scantlings more sophisticated methods may be substituted subject to special approval. 204 If scantlings derived from these regulations are less than those required for an unstrengthened ship, the latter shall be used. 205 The frame spacing and spans defined in the following text are normally assumed to be measured in a vertical plane parallel to the centreline of the ship. However, if the ship s side deviates more than 20 from this plane, the frame distances and spans shall be measured along the side of the ship. 206 Assistance from icebreakers is normally assumed when navigating in ice bound waters. A 300 Definitions 301 Maximum draught amidships The maximum ice class draught amidships shall be the draught on the Fresh Water Load Line in Summer. If the ship has a timber load line, the Fresh Water Timber Load Line in Summer shall be used. 302 Maximum and minimum draught fore and aft The maximum and minimum ice class draughts fore and aft shall be determined and stated in the classification certificate. The line defined by the maximum draughts fore, amidships and aft will henceforth be referred to as LWL. The line may be a broken line. The line defined by the minimum draughts fore and aft will be referred to as BWL. The draught and trim, limited by the LWL, must not be exceeded when the ship is navigating in ice. The salinity of the sea water along the intended route is to be taken into account when loading the ship. Filling of ballast tanks may be necessary to load the ship to the BWL. Any ballast tanks situated fully or partly above the BWL adjacent to the ship's shell are to be equipped with anti-freezing device(s) to prevent the water from freezing, see J603. In determining the BWL, regard shall be paid to the need for ensuring a reasonable degree of ice going capability in ballast. The propeller shall be fully submerged, if possible entirely below the ice. The minimum forward draught shall be at least: ( f ) h o (m) but need not exceed 4 h o where f displacement of the ship (t) on the maximum ice class draught according to 301 h o ice thickness according to B 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 L aft of the forward borderline of the part of the hull where the waterlines run parallel to the centre line. For ice classes ICE- 1A*F, ICE-1A* and ICE-1A the overlap of the borderline need not exceed 6 m, for ice classes ICE-1B and ICE-1C this overlap need not exceed 5 m. Midship region: From the aft boundary of the Forward region to a line parallel to and 0.04 L aft of the aft borderline of the part of the hull where the waterlines run parallel to the centre line. For ice classes ICE-1A*F, ICE-1A* and ICE-1A the overlap of the borderline need not exceed 6 m, for ice classes ICE-1B and ICE-1C this overlap need not exceed 5 m. Aft region: From the aft boundary of the Midship region to the stern. A 400 Documentation 401 LWL and BWL are to be indicated on the shell expansion plan together with the lines separating the forward, amidships and aft regions of the ice belt. The machinery, displacement, f, and the output of propulsion machinery, P s, are to be stated on the shell expansion and/or the framing plan.

9 Pt.5 Ch.1 Sec.3 Page 9 The value of c 1 is given in Table B3: Fig. 1 Ice belt regions B. Design Loads B 100 Height of load area 101 An ice strengthened ship is assumed to operate in open sea conditions corresponding to a level ice thickness not exceeding h o. The design height (h) of the area actually under ice pressure at any particular point of time is, however, assumed to be only a fraction of the ice thickness. The values for h o and h are given in the following table. Table B1 Values of h o and h Ice class h o (m) h (m) ICE-1A* ICE-1A ICE-1B ICE-1C B 200 Ice pressure 201 The design ice pressure (based on a nominal ice pressure of kn/m 2 ) is determined by the formula: p c d c 1 c a (kn/m 2 ) c d a factor which takes account of the influence of the size and engine output of the ship. It is calculated by the formula: f P s k a and b are given in Table B2. Table B2 Values of a and b Region Forward Midship and aft k 12 k > 12 k 12 k > 12 a b f P s c 1 c d ak + b displacement (t) as defined in A302 machinery output (kw) as defined in J101 a factor which takes account of the probability that the design ice pressure occurs in a certain region of the hull for the ice class in question. Table B3 Values of c 1 Ice class Region Forward Midship Aft ICE-1A* ICE-1A ICE-1B ICE-1C For ice class ICE-1A*F an additional lower forward ice belt (see C102) is defined with factor c c a a factor which takes account of the probability that the full length of the area under consideration will be under pressure at the same time. It is calculated by the formula: 47 5l a c a , maximum 1.0, minimum l a is to be taken as given in Table B4. Table B4 Values of l a Structure Type of framing l a Shell transverse frame spacing longitudinal 2 x frame spacing Frames transverse frame spacing longitudinal span of frame Ice stringer span of stringer Web frame 2 x web frame spacing C. Shell Plating C 100 Vertical extension of ice strengthening 101 The vertical extension of the ice belt (see Fig.1) is not to be less than given in Table C1. Table C1 Vertical extension of ice belt Ice class Above LWL (m) Below BWL (m) ICE 1A* ICE 1A ICE 1B ICE 1C In addition the following areas shall be strengthened: Fore foot: For ice class ICE-1A* and ICE-1A*F the shell plating below the ice belt from the stem to a position five main frame spaces abaft the point where the bow profile departs from the keel line shall have at least the thickness required in the ice belt in the midship region, calculated for the actual frame spacing. Upper forward ice belt: For ice classes ICE-1A* and ICE-1A on ships with an open water service speed equal to or exceeding 18 knots, the shell plate from the upper limit of the ice belt to 2 m above it and from the stem to a position at least 0.2 L abaft the forward perpendicular, is to have at least the thickness required in the ice belt in the midship region, calculated for the actual frame spacing. Guidance note: A similar strengthening of the bow region is advisable also for a ship with a lower service speed, when it is, e.g. on the basis of the model tests, evident that the ship will have a high bow wave. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- For ice class ICE-1A*F the upper forward ice belt is to be tak-

10 Pt.5 Ch.1 Sec.3 Page 10 en 3 m above the normal ice belt, extending within the forward region. Lower forward ice belt: For ice class ICE-1A*F a lower forward ice belt below the normal ice belt is defined covering the forward region aft of the forefoot and down to the lower turn of bilge. 103 Sidescuttles are not to be situated in the ice belt. If the weather deck in any part of the ship is situated below the upper limit of the ice belt (e.g. in way of the well of a raised quarter deck), the bulwark is to be given at least the same strength as is required for the shell in the ice belt. The strength of the construction of the freeing ports is to meet the same requirements. C 200 Plate thickness in the ice belt 201 For transverse framing the thickness of the shell plating is to be determined by the formula: x t 21.1s 1 p PL + t σ c (mm) F For longitudinal framing the thickness of the shell plating is to be determined by the formula: p PL t 21.1s t x 2 σ c (mm) F p PL 0.75 p p as given in B x ( h s + 1.8) 2, maximum x ( h s), when h/s (h/s); when 1 h/s < (h/s) for 1.8 h/s < for h/s > 3 h as given in B100 σ F yield stress of the material (N/mm 2 ) t c increment for abrasion and corrosion (mm); normally 2 mm. If a special surface coating, by experience shown capable to withstand the abrasion of ice, is applied and maintained, lower values may be approved. 202 For ice class ICE-1A*F the following additional requirements are given: bottom plating in the forward region (below the lower forward ice belt defined in 102) is to have a thickness not less than: t 0.7( s + 0.8) 235L (mm), minimum 12 mm σ F side and bottom plating in the aft region below the ice belt is to have a thickness not less than: t 0.6( s + 0.8) D. Frames D 100 Vertical extension of ice framing 101 The vertical extension of the ice strengthening of the framing is to be at least as given in Table D1: Table D1 Vertical extension of ice strengthening of the framing Ice class Region Above LWL (m) Below BWL (m) ICE- 1A*F forward 1.2 to double bottom or below top of floors midship aft from stem to to double bottom or below 0.3 L abaft it 1.2 top of floors ICE-1A* abaft 0.3 L from stem midship aft from stem to 0.3 L abaft it ICE-1A, 1B, 1C L (mm), minimum 10 mm σ F abaft 0.3 L from stem midship aft Where an upper forward ice belt is required (see C102), the ice strengthened part of the framing is to be extended at least to the top of this ice belt. 102 Where the ice strengthening would go beyond a deck or a tank top by not more than 250 mm, it can be terminated at that deck or tank top. D 200 Transverse frames 201 The section modulus of a main or intermediate transverse frame is to be calculated by the formula: Z pshl m t σ F ( cm 3 ) p ice pressure as given in B200 h height of load area as given in B100 m t 7m o 7 5h l m o values as given in Table D2.

11 Pt.5 Ch.1 Sec.3 Page 11 Table D2 Values of m o Boundary condition m o Example Frames in a bulk carrier with top wing tanks Frames extending from the tank top to a single deck Continuous frames between several decks or stringers 1) The upper end of the strengthened part of a main frame and of an intermediate ice frame is to be attached to a deck or an ice stringer (see E). 2) Where an intermediate frame terminates above a deck or an ice stringer which is situated at or above the upper limit of the ice belt (see C100) the part above the deck or stringer may have the scantlings required for an unstrengthened ship and the upper end be connected to the adjacent main frames by a horizontal member of the same scantlings as the main frame. Such an intermediate frame can also be extended to the deck above and if this is situated more than 1.8 metre above the ice belt the intermediate frame need not 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 and of 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 the lower limit of the ice belt (see C100), the lower end to be connected to the adjacent main frames by a horizontal member of the same scantlings as the frames. D 300 Longitudinal frames 301 The section modulus of a longitudinal frame is to be calculated by the formula: Z x 3 x 4 phl m 1 σ F ( cm 3 ) The shear area of a longitudinal frame is to be: These formulae assume that the longitudinal frame is attached to supporting structure by brackets as required in x 3 phl A ( cm 2 ) σ F 5 Frames extending between two decks only x 3 factor which takes account of the load distribution to adjacent frames: x 3 (1 0.2 h/s) The boundary conditions are those for the main and intermediate frames. Possible different conditions for main and intermediate frames are assumed to be taken care of by interaction between 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 transverse frame, (b < 0.5 l) the following modified formula may be used for the section modulus: b Z ps h b ( l b) σ F l ( cm 3 ) distance in m between upper or lower boundary of the ice belt and the nearest deck or stringer within the ice belt. Where less than 15% of the span, l, of the frame is situated within the ice-strengthening zone for frames as defined in D101, ordinary frame scantlings may be used. 202 Upper end of transverse framing x 4 p h m 1 factor which takes account of the concentration of load to the point of support: x ice pressure as given in B200 height of load area as given in B100 boundary condition factor; m for a continuous beam. Where the boundary conditions deviate significantly from a continuous beam, a smaller factor may be required. Normally m 1 12 is to be used for longitudinals, taking into account load variations between adjacent spans. D 400 Structural details 401 Within the ice strengthened area all frames are to be effectively attached to all supporting structures by brackets. Frames crossing supporting structures such as web frames or stringers 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 apply in the ice strengthened area: 1) Frames which are not at a straight angle to the shell are to be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 1.3 m. Frames perpendicular to shell which are of unsymmetrical profiles are to have tripping preventions at a distance not exceeding 2.6 m.

12 Pt.5 Ch.1 Sec.3 Page 12 2) Frames and girder webs are to be attached to the shell by double continuous welds. No scalloping is allowed (except when crossing shell plate butts). 3) The web thickness of the frames is to be at least one half of the thickness of the shell plating and at least 9 mm. Where there is a deck, tank top or bulkhead in lieu of a frame the plate thickness of this is to be as above, to a depth corresponding to the height of adjacent frames. E. Ice Stringers E 100 Stringers within the ice belt 101 The section modulus of a stringer situated within the ice belt (see C100) is to be calculated by the formula: Z 0.9p h l ( cm 3 ) m 1 σ F The shear area is not to be less than: 7.8 p hl A ( cm 2 ) σ F p ice pressure as given in B200 h height of load area as given in B100 The product p h is not to be taken as less than 300 l span of stringer (m) m 1 boundary condition factor as given in D301. E 200 Stringers outside the ice belt 201 The section modulus of a stringer situated outside the ice belt but supporting ice strengthened frames is to be calculated by the formula: 0.95 p h l 2 h Z s m 1 σ F l s The shear area is not to be less than: A ( cm 3 ) p h l σ ( cm 2 ) F l s p ice pressure as given in B200 h height of load area as given in B100 The product p h is not to be taken as less than 300. l span of stringer (m) m 1 boundary condition factor as given in D301 l s the distance to the adjacent ice stringer(m) h s the distance to the ice belt (m). E 300 Deck strips 301 Narrow deck strips abreast of hatches and serving as ice stringers are to comply with the section modulus and shear area requirements in 100 and 200 respectively. In the case of very long hatches the lower limit of the product p h may be reduced to Regard shall be paid to the deflection of the ship's sides due to ice pressure in way of very long hatch openings, when designing weatherdeck hatch covers and their fittings. h s F. Web Frames F 100 Design load 101 The load transferred to a web frame from an ice stringer or from longitudinal framing shall be calculated by the formula: F p h s (kn) p h ice pressure as given in B200, when calculating factor c a, however, l a is to be taken as 2 s 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 F may be multiplied by: as given in E201. Fig. 2 Web frame F 200 Section modulus and shear area 201 For a web frame simply supported at the upper end and fixed at the lower end (see Fig.2), the section modulus requirement is given by: Z M σ F M maximum calculated bending moment under the load F, as given in 101 γ as given in Table F1 A required shear area from 202 A a actual cross sectional area of web plate. 202 With boundary conditions as given in 201, the shear area of a web frame is given by: h s l s γ A 10 3 (cm 3 ) A a α Q A (cm 2 ) σ F Q maximum calculated shear force under the load F, as given in 101 α factor given in Table F1 A f cross sectional area of free flange A w cross sectional area of web plate.

13 Pt.5 Ch.1 Sec.3 Page For other web frame configurations and boundary conditions than given in 201, a direct stress calculation should be performed. The concentrated load on the web frame is given in 101. The point of application is in each case to be chosen in relation to the arrangement of stringers and longitudinal frames so as to obtain the maximum shear and bending moments. Allowable stresses are as follows: shear stress: bending stress: equivalent stress: τ σ F 3 σ b σ F 2 σ c σ b + 3τ 2 σ F Table F1 Values of α and γ A f A w α γ G. Bilge Keels G 100 Arrangement 101 The connection of bilge keels to the hull are to be so designed that the risk of damage to the hull, in case a bilge keel is ripped off, is minimised. 102 To limit damage when a bilge keel is partly ripped off, it is recommended that bilge keels are cut up into several shorter independent lengths. 103 For class ICE-1A*F bilge keels are normally to be avoided and should be replaced by roll-damping equipment. Specially strengthened bilge keels may be considered. H. Special Arrangement and Strengthening Forward H 100 Stem, baltic ice strengthening 101 The stem may be made of rolled, cast or forged steel or of shaped steel plates. A sharp edged stem (see Fig.3) improves the manoeuvrability of the ship in ice and is recommended particularly for smaller ships with length less than 150 m. Fig. 3 Welded stem 102 The plate thickness of a shaped plate stem and in the case of a blunt bow, any part of the shell which forms an angle of 30 or more to the centre line in a horizontal plane, is to be calculated according to the formulae in C200 assuming that: s spacing of elements supporting the plate (m) p PL p (see B200). l a spacing of vertical supporting elements (m). For class ICE-1A*F the front plate and upper part of the bulb and the stem plate up to a point 3.6 m above LWL (lower part of bow door included) is to have a minimum thickness of: c t c L (mm) σ f 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 0.2 b on each side of the centre line, b being the breadth of the bulb at F.P. 103 The stem and the part of a blunt bow defined above are to be supported by floors or brackets spaced not more than 0.6 m apart and having a thickness of at least half the plate thickness. The reinforcement of the stem is to be extend from the keel to a point 0.75 m above LWL or, in case an upper forward ice 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 by 300 mm, a length of at least 150 mm and an inner surface radius of at least 100 mm is to be fitted in the bow bulwark at the centre line. 202 A bitt or other means for securing a towline, dimensioned to stand the breaking force of the towline of the ship is to be fitted. 203 On ships with a displacement not exceeding tons the part of the bow which extends to a height of at least 5 m above the LWL and at least 3 m aft of the stem, is to be strengthened to take the stresses caused by fork towing. For this purpose intermediate frames are to be fitted and the framing shall be supported by stringers or decks. 204 It shall be noted that for ships of moderate size (displacement not exceeding tons) fork towing in many situations is the most efficient way of assisting in ice. Ships with a bulb protruding more than 2.5 m forward of the forward perpendicular are often difficult to tow in this way. The administrations reserve the right to deny assistance to such ships if the situation so warrants.

14 Pt.5 Ch.1 Sec.3 Page 14 I. Special Arrangement and Strengthening Aft I 100 Stern 101 The introduction of new propulsion arrangements with azimuthing thrusters or podded propellers, which provide an improved manoeuvrability, will result in increased ice loading of the aft region and stern area. This fact should be considered in the design of the aft/stern structure. 102 An extremely narrow clearance between the propeller blade tip and the stern frame is to be avoided as a small clearance would cause very high loads on the blade tip. 103 On twin and triple screw ships the ice strengthening of the shell and framing is to be extended to the double bottom for 1.5 metre forward and aft of the side propellers. 104 Shafting and stern tubes of side propellers are normally to be enclosed within plated bossings. If detached struts are used, their design, strength and attachment to the hull are to be duly considered. For class ICE-1A*F the skin plating of propeller shaft bossings is not to be less than: t 0.9( s+ 0.8) 105 A wide transom stern extending below the LWL will seriously impede the capability of the ship to run astern in ice, which is most essential. Therefore a transom stern is not to be extended below the LWL if this can be avoided. If unavoidable, the part of the transom below the LWL is to be kept as narrow as possible. The part of a transom stern situated within the ice 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, pintles, steering gear etc. as well as the capacity of the steering gear are to be determined according to the rules. The maximum service speed of the ship to be used in these calculations is, however, not to be taken less than that stated below: Table I1 Maximum service speed Ice class Maximum service speed ICE-1A* 20 knots ICE-1A 18 knots ICE-1B 16 knots ICE-1C 14 knots 235L (mm). σ f If the actual maximum service speed of the ship is higher, that speed is to be used. When calculating the rudder force according to the formula given in Pt.3 Ch.3 Sec.2 D and with the speed V in ahead condition as given above, the factors k 1 k irrespective of condition, rudder profile type or arrangement. In the astern condition half the speed values is to be used. 202 For the ice classes ICE-1A* and ICE-1A the rudder stock and the upper edge of the rudder is to be protected against ice pressure by an ice knife or equivalent means. Guidance note: Upper forward part of rudder and forward part of rudder horn should be protected against abrasion by a special coating or increase in thickness. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e For ice classes ICE-1A* and ICE-1A due regard is to be paid to the excessive loads caused by the rudder being forced out 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 to stand the yield torque of the rudder stock. Where possible rudder stoppers working on the blade or rudder head are to be fitted. 205 Parts of rudder within the ice belt are to have local thickness at least equivalent to the side shell in the afterbody. J. Machinery J 100 Engine output 101 Definition of engine output The engine output P S is the maximum output the propulsion machinery can continuously deliver to the propeller(s). If the output of the machinery is restricted by technical means or by any regulations applicable to the ship, P S shall be taken as the restricted output. 102 Documentation on board Minimum engine output corresponding to the ice class shall be given in the Classification Certificate. 103 Required engine output for ice classes Definitions The dimensions of the ship and some other parameters are defined below: L length of the ship between the perpendiculars (m) L BOW length of the bow (m), Fig.4 L PAR length of the parallel midship body (m), Fig.4 B maximum breadth of the ship (m) T actual ice class draughts of the ship (m) according to A301 A wf area of the waterline of the bow (m 2 ), Fig.4 α the angle of the waterline at B/4 ( ), Fig.4 ϕ 1 the rake of the stem at the centreline ( ), Fig.4 ϕ 2 the rake of the bow at B/4 ( ), Fig.4 D P diameter of the propeller or outer diameter of nozzle for the nozzle propeller, maximum 1.2 times propeller diameter (m) H M thickness of the brash ice in mid channel (m) H F thickness of the brash ice layer displaced by the bow (m). Range of validity The range of validity of the formulae for powering requirements in 104 is presented in Table J1. When calculating the parameter DP/T, T shall be measured at LWL. Table J 1 Parameter validity range Parameter Minimum Maximum α [degrees] ϕ 1 [degrees] ϕ 2 [degrees] L [m] B [m] T [m] L BOW /L L PAR /L D P /T A wf /(L*B) If the ship s parameter values are beyond the ranges defined in Table J1, other methods for determining R CH shall be used as defined in 105.

15 Pt.5 Ch.1 Sec.3 Page 15 Fig. 4 Definitions 104 The engine output requirement shall be calculated for following 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 the draught are to be determined at the appropriate draught, but L and B are to be determined only at the LWL. The engine output shall not be less than the greater of these two outputs. The engine output P S shall not be less than that determined by the 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. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- Table J2 Value of factor K e Propeller type or machinery Numbers of propellers P S K e R CH D P Controllable pitch propeller or electric or hydraulic propulsion machinery Fixed pitch propeller 1 propeller propellers propellers Table J3 Minimum engine output P S ICE-1A, ICE-B and ICE-C ICE-1A* kw kw R CH is the resistance in Newton of the ship in a channel with brash ice and a consolidated layer: (kw) R CH C 1 + C 2 + C 3 C µ ( H F + H M ) 2 ( B+ C ψ H F ) + 2 C 4 L PAR H F C LT A wf + B (N) L C µ 0.15 cosϕ 2 + sinψ sinα 0.45 C ψ 0.047ψ and 0 if ψ 45 H F (H M B) 0.5 H M 1.0 for ICE-1A and ICE-1A* 0.8 for ICE-1B 0.6 for ICE-1C C 1 and C 2 take into account a consolidated upper layer of the brash ice and can be taken as zero for ice class ICE-1A, ICE- 1B and ICE-1C. For ice class ICE-1A*: BL PAR C 1 f T + ( ϕ 1 )( f 2 B + f 3 L BOW + f 4 BL BOW ) B C ( ϕ )( g + g B) g T B --- B L For a ship with a bulbous bow, ϕ 1 shall be taken as 90. f 1 23 (N/m 2 ) f (N/m) f (N/m) f 4 29 (N/m 2 ) g (N) g (N/m) g (N/m 1.5 ) C (kg/(m 2 s 2 )) C 4 42 (kg/(m 2 s 2 )) C (kg/s 2 ) tanϕ 2 ψ arctan sinα LT The following shall apply: B 2

16 Pt.5 Ch.1 Sec.3 Page Other methods of determining K e or R CH For an individual ship, in lieu of the K e or R CH values defined in Table J2 and 104, the use of K e or R CH values based on more exact calculations or values based on model tests may be approved. Such approval will be given on the understanding that it can be revoked if experience of the ship s performance in practice motivates this. The design requirement for ice classes shall be a minimum speed of 5 knots in the following brash ice channels (see Table J4): Table J4 Values of H M Ice class H M ICE-1A* 1.0 m and a 0.1 m thick consolidated layer of ice ICE-1A 1.0 m ICE-1B 0.8 m ICE-1C 0.6 m J 200 Design loads for propeller and shafting 201 The formulae for scantlings are based on the following loads: T o mean torque of propulsion engine at maximum continuous rating in Nm (If multi-engine plant, T o is the mean torque in an actual branch or after a common point. T o is always referred to engine r.p.m.) Th o mean propeller thrust in N at maximum continuous speed R as given in 301. T ice ice torque in Nm (referred to propeller r.p.m.) and found from Table J5. Table J5 Values of T ice Ice class Open propeller Ducted propeller ICE-1A* R R 2 ICE-1A R R 2 ICE-1B R R 2 ICE-1C R R 2. R > 3 m R 2. R < 1.5 m 1) 1) For 1.5 m < R < 3 m, T ice may be found by linear interpolation. J 300 Propeller 301 The particulars governing the requirements for scantlings are: R propeller radius (m) H r pitch in m at radius in question θ rake in degrees at blade tip (backward rake positive) Z number of blades t blade thickness in mm at cylindrical section considered t 0.25 t at 0.25 R t 0.35 t at 0.35 R t 0.6 t at 0.6 R c r blade width in m at cylindrical section considered c 0.25 c r at 0.25 R c 0.35 c r at 0.35 R c 0.6 c r at 0.6 R u gear ratio: If the shafting system is directly coupled to engine, u 1. n o u engine r.p.m propeller r.p.m. propeller speed at maximum continuous output, for which the machinery is to be approved, in revolutions per minute. 302 Propellers are to be of steel or bronze as specified for propeller castings in Pt.2 Ch Moderately or highly skewed propellers will be especially 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: U 1 and U 2 material constants to be taken as given in Pt.4 Ch.5 Sec.1 Table B1. S r For fixed blade propellers For controllable pitch propellers K 4 k i Z T ice sinα C 1, C 2, C 3, C 4 as given in Table J6. A q 0 + q 1 d + q 2 d 2 + q 3 d 3 q 0, q 1, q 2, q 3 as given in Table J7. d d 2πR for controllable pitch propellers 0.7H r k i 96 at 0.25 R 92 at 0.35 R K Mat 1.0 for stainless steel propellers 0.8 for other materials sin α 2RK t C 1 ( U 2 C ) + K Zc r ( K Mat U 1 U 2 S r ) (mm) 0.45c t t (mm) 2Rn o 2 ( C θ + C 3 ) K 1 A 1 dth o A 2 K 1 A 1 dth o 1.25 ut o + A R c uT o R 2πR for fixed blade propellers H r at 0.25 R d at 0.35 R d K 1 as given above is only valid for propulsion by diesel engines (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 K 1 will be considered in each particular case. The thickness of other sections is governed by a smooth curve