Attachment_2__-_Ships_for_Navigation_in_Ice.pdf

RULES FOR

CLASSIFICATION OF

SHIPS

NEWBUILDINGS

SPECIAL SERVICE AND TYPE

ADDITIONAL CLASS

PART 5 CHAPTER 1

SHIPS FOR NAVIGATION IN ICE

JULY 2009

CONTENTS PAGE

Sec. 1 General Requirements Sec. 2 Basic Ice Strengthening Sec. 3 Ice Strengthening for the Northern Baltic Sec. 4 Vessels for Arctic and Ice Breaking Service Sec. 5 Sealers Sec. 6 Winterization Sec. 7 DAT(-X°C) Sec. 8 IACS Unified Requirements For Polar Ships (Tentative Rules) App. A Guidelines for Strength Analysis of the Propeller Blade using Finite Element Method

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CHANGES IN THE RULES

General The present edition of the rules includes additions and amendments approved by the Board as of June 2009 and supersedes the January 2009 edition of the same chapter.

The rule changes come into force as indicated below.

This chapter is valid until superseded by a revised chapter. Supple-ments will not be issued except for an updated list of minor amend-ments and 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 chap-ters printed Pt.0 Ch.1 Sec.1 to ensure that the chapter is current.

Main changes coming into force 1 January 2010

• Sec.2 Basic Ice Strengthening

— Sub-section element C200 “Design of propeller and propeller shaft” has been amended as a consequence of changes to Sec.3.

• Sec.3 Ice Strengthening for Northern Baltic

— Sub-section element A400 “Documentation requirements” has been amended.

— New design loads for propeller and shafting have been intro-duced and Sub-section J “Propulsion Machinery” has been com-pletely revised.

• Sec.4 Vessels for Arctic and Ice Breaking Service

— Item A401 has been amended as a consequence of changes to

Sec.2 and Sec.3.

• Sec.6 Winterization

— Item C402 has been amended giving an opening to use the dam-age extent description from MSC/Circ. 1056.

• App.A Guidelines for Strength Analysis of the Propeller Blade using Finite Element Method

— This new guideline has been introduced as a consequence of the above changes.

Corrections and Clarifications In addition to the above stated rule requirements, a number of correc-tions and clarifications have been made in the existing rule text.

Comments to the rules may be sent by e-mail 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 http://www.dnv.com

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Rules for Ships, July 2009 Pt.5 Ch.1 Contents – Page 3

CONTENTS

SEC. 1 GENERAL REQUIREMENTS

A. Classification A 100 Application A 200 Class notations

B. Definitions B 100 Symbols B 200 Upper (UIWL) and Lower (LIWL) Ice

Waterlines

C. Documentation C 100 General

D. Marking and on Board Documentation D 100 General

SEC. 2 BASIC ICE STRENGTHENING

A. General A 100 Classification

B. Structural Requirements for the Class Notation ICE-C B 100 General B 200 Plating B 300 Framing B 400 Stringers and web frames B 500 Weld connections B 600 Rudder and steering arrangement B 700 Stem

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

D. Requirements for the Class Notation ICE-E D 100 General D 200 Plating D 300 Framing D 400 Stem

SEC. 3 ICE STRENGTHENING FOR THE

NORTHERN BALTIC

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

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

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

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

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

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

G. Bilge Keels G 100 Arrangement

H. Special Arrangement and Strengthening Forward

H 100 Stem, baltic ice strengthening H 200 Arrangements for towing

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

J. Propulsion Machinery J 100 Engine output J 200 Materials J 300 Design loads for propeller and shafting J 400 Design loads J 500 Design loads on propeller blades J 600 Axial design loads for open and ducted propellers J 700 Torsional design loads J 800 Blade failure load J 900 Design principle J 1000 Propeller blade design J 1100 Propeller bossing and CP mechanism J 1200 Propulsion shaft line J 1300 Design of shaft line components not specifically mentioned in FSICR J 1400 Azimuting main propulsors and other thrusters J 1500 Alternative design

K. Miscellaneous Machinery Requirements K 100 Starting arrangements K 200 Sea inlet and cooling water systems K 300 Ballast system

L. Guidelines for Strength Analysis of the Propeller Blade using Finite Element Method

SEC. 4 VESSELS FOR ARCTIC AND

ICE BREAKING SERVICE

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

B. Materials and Corrosion Protection B 100 Design temperatures B 200 Selection of steel grades B 300 Coatings B 400 Corrosion additions

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

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

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

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

DET NORSKE VERITAS

Pt.5 Ch.1 Contents – Page 4 G. Hull Appendages and Steering Gears G 100 General G 200 Ice loads on rudders G 300 Rudder scantlings G 400 Ice loads on propeller nozzles G 500 Propeller nozzle scantlings G 600 Steering gear G 700 Podded propulsors and azimuth thrusters

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

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

J. Propulsion Machinery and Propellers J 100 General J 200 Engine output J 300 Determination of ice torque and loads J 400 Propeller J 500 Propulsion shaft line reinforcement

K. Thrusters K 100 General K 200 Propulsion thrusters K 300 Other thrusters

L. Stability and Watertight Integrity L 100 Application L 200 Documentation L 300 Requirements for intact stability L 400 Requirements for damage stability L 500 Requirements to watertight integrity

SEC. 5 SEALERS

A. General A 100 Classification A 200 Hull form

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

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

D. Anchoring and Mooring Equipment D 100 General

E. Machinery E 100 Output of propulsion machinery E 200 Thrust bearing, reduction gear, shafting and propeller ...48 E 300 Machinery systems

SEC. 6 WINTERIZATION

A. General A 100 Classification A 200 Documentation A 300 Definitions

B. Requirements for WINTERIZED BASIC B 100 Arrangements, anti-icing and de-icing B 200 Special equipment B 300 Power generator capacity

C. Additional Requirements for Class Notation WINTERIZED COLD (t1, t2)

C 100 General C 200 de-icing requirements C 300 Ship arrangement - Ice strengthening of hull, rudder, steering gear, propeller and propeller shaft C 400 Stability and Watertight Integrity

C 500 Hull material C 600 Materials for equipment C 700 Testing of equipment

D. Additional Requirements for Class Notation

WINTERIZED ARCTIC (.. , ..)

D 100 General D 200 Ice strengthening and propulsion D 300 Enhanced oil pollution prevention D 400 Miscellaneous

SEC. 7 DAT(-X°C)

A. General A 100 Classification A 200 Documentation A 300 Definitions

B. Material Selection B 100 Structural categories B 200 Selection of steel grades

SEC. 8 IACS UNIFIED REQUIREMENTS FOR

POLAR SHIPS (TENTATIVE RULES)

A. General A 100 Application A 200 Polar classes A 300 Documentation A 400 Ship design and arrangement A 500 Design principles – hull areas A 600 System design

B. Design Ice Loads – Hull B 100 General B 200 Glancing impact load characteristics B 300 Bow area B 400 Hull areas other than the bow B 500 Design load patch B 600 Pressure within the design load patch B 700 Hull area factors

C. Local Strength Requirements C 100 Shell plate requirements C 200 Framing general C 300 Framing – Transversely framed side structures and bottom structures C 400 Framing – Side longitudinals (longitudinally framed ships) C 500 Framing – web frame and load carrying stringers C 600 Framing – Structural stability C 700 Plated structures C 800 Stem and stern frames C 900 End Connections for framing members

D. Longitudinal Strength D 100 Application D 200 Design Vertical Ice Force at the Bow D 300 Design Vertical Shear Force D 400 Design Vertical Ice Bending Moment D 500 Longitudinal Strength Criteria

E. Appendages E 100 General E 200 Rudders E 300 Ice forces on rudder E 400 Rudder scantlings E 500 Ice loads on propeller nozzles E 600 Propeller nozzle scantlings E 700 Podded propulsors and azimuth thrusters

F. Direct Calculations F 100 General

G. Welding G 100 General G 200 Minimum weld requirements

H. Materials and Corrosion Protection H 100 Corrosion/abrasion additions and steel renewal H 200 Hull materials

Pt.5 Ch.1 Contents – Page 5 H 300 Materials in machinery components exposed to sea water

H 400 Materials in machinery components exposed to sea water temperatures

H 500 Materials in machinery components exposed to low air temperature

I. Ice Interaction Loads – Machinery I 100 Propeller ice interaction I 200 Ice class factors I 300 Design ice loads for open propeller I 400 Design Ice Loads for Ducted Propeller I 500 Load distribution for blade loads I 600 Design ice loads for propulsion line I 700 Machinery fastening loading conditions

J. Design – Machinery J 100 Design principle J 200 Blade design J 300 Fatigue design J 400 CP mechanism J 500 Shaft and components J 600 Azimuting Main Propulsion

J 700 Steering system J 800 Prime movers J 900 Auxiliary systems J 1000 Sea inlets, cooling water systems and ballast tanks J 1100 Ballast tanks J 1200 Ventilation systems J 1300 Alternative design

K. Stability and Watertight Integrity K 100 General

APP. A GUIDELINES FOR STRENGTH ANALYSIS

OF THE PROPELLER BLADE USING FINITE

ELEMENT METHOD

A. Guidelines for Strength Analysis of the Propeller Blade using Finite Element Method

A 100 Requirements for FE model A 200 Good engineering practice for FE analysis A 300 Boundary conditions A 400 Applied pressure loads

Pt.5 Ch.1 Contents – Page 6

Pt.5 Ch.1 Sec.1 – Page 7

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 shall be regarded as supplementary to those given for the assignment of main class.

A 200 Class notations 201 Vessels complying with relevant additional require-ments of this chapter will be assigned one of the following class notations:

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 *) Δ = rule displacement in t *) CB = block coefficient *) Δf = displacement in t in fresh water (density 1.0 t/m3) at ice class draught Ps = maximum continuous output of propulsion machinery in kW s = stiffener spacing in m measured along the plating be-tween ordinary and/or intermediate stiffeners l = 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

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

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

For NV-NS-steel and HS-steel, σF to be taken as given in Pt.3 Ch.1 Sec.2 B201 and Pt.3 Ch.2 Sec.2 B201.

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

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

B 200 Upper (UIWL) and Lower (LIWL) Ice Waterlines 201 The upper ice waterline, (UIWL) shall be the deepest waterline at which the ship is intended to operate in ice irrespective of water salinity. The line may be knuckled.

202 The lower ice waterline, (LIWL) shall be the lowest waterline at which the ship is intended to operate in ice.

203 All design loading conditions in ice, including trim, shall be within the draught envelope limited by the UIWL and LIWL. The lower ice waterline should further be determined with due regard to the vessel's ice-going capability in the bal-last loading conditions (e.g. propeller submergence). See also Sec.3 B.

(IACS UR I 1.3)

C. Documentation C 100 General 101 Details related to additional classes regarding design, ar-rangement 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.

D. Marking and on Board Documentation D 100 General 101 The maximum and minimum ice class draughts fore, amidships and aft shall be indicated in the “Appendix to the Classification Certificate”.

102 If the “Summer Load Line” in fresh water is located at a higher level than the UIWL, the ice class notation shall explic-itly include the maximum amidships draughts.

For such ships, the ship sides shall be provided with a warning triangle and with ice class draught marks at the maximum per-missible amidships draught, see Fig.1.

Table A1 Class notations Notation Reference

ICE-C

ICE-E (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)

WINTERIZED BASIC

WINTERIZED COLD (t1, t2) WINTERIZED ARCTIC (t1, t2)

(See Sec.6)

Sealer (See Sec.5) DAT(-X°C) (See Sec.7)

PC-1

PC-2

PC-3

PC-4

PC-5

PC-6

PC-7

Icebreaker

(See Sec.8)

Pt.5 Ch.1 Sec.1 – Page 8 Fig. 1 Ice class draught marking

Marking requirements:

1) The ice class draught marking “ICE” shall indicate the maximum ice class draught.

2) The bottom of the warning triangle shall be located at the height 1 000 mm above Summer Fresh Water Load Line, but not higher than the deck line. The sides of the triangle shall be 300 mm in length.

3) The ice class draught mark shall be located 540 mm abaft the centre of the load line ring or 540 mm abaft the vertical line of the timber load line mark, if applicable.

4) The ice marks and letters shall be cut out of 5 - 8 mm plate and then welded to the ship's side. The marks and letters shall be painted in a red or yellow reflecting colour in or-der to make the marks and figures plainly visible even in ice conditions.

5) The dimensions of all letters shall be the same as those used in the load line mark.

6) For vessels not having load line markings, the warning tri-angle and ice draught mark shall be vertically aligned with the draught mark. The warning triangle shall be placed 1 000 mm above the draught mark, but in no case above the deck line.

ICE

ICE

Pt.5 Ch.1 Sec.2 – Page 9

SECTION 2

BASIC ICE STRENGTHENING

A. General A 100 Classification 101 The requirements in this section apply to vessels intend-ed for service in waters with light ice conditions.

The requirements in D for class notation ICE-E are intended for light localised drift ice in mouths of rivers and coastal are-as.

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

103 Vessels built in compliance with the requirements in D may be given the class notation ICE-E.

B. Structural Requirements for the Class Nota-tion ICE-C

B 100 General 101 The requirements for the forward ice belt region, as de-fined in Sec.3 Fig.1, for sub-section elements 200 - 700, shall be in accordance with Sec.3 as follows:

— In Table B1, the value of ho and h shall be as given for

ICE-1C.

— The ice pressure shall be determined in accordance with Sec.3 B200, where the factor c1, as given in Table B3, is taken as being equal to 0.55.

— Vertical extension of the ice belt plating and framing shall be:

Plating: 0.5 m above UIWL and 0.5 m below LIWL Framing: 0.62 m above UIWL and 1.0 m below LIWL.

B 200 Plating 201 In the forward ice belt region as defined in 101, the shell plate thickness shall be as given in Sec.3 C.

B 300 Framing 301 In the forward ice belt region as defined in 101, the frames shall be as given in Sec.3 D100 - D300.

In addition, the following shall apply:

1) Frames shall be effectively attached to all supporting structures. Transverse and longitudinal frames crossing support structures shall be connected to these with lugs.

Alternatively, top stiffener in combination with lug may be used. The upper end of intermediate frames may be sniped at a stringer or deck provided the ice belt covers not more than 1/3 of the span.

2) Frames where the angle between the web and the shell is less than 75 degrees shall be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding 2.5 m.

Transverse frames perpendicular to shell which are of un-symmetrical profiles shall have tripping preventions if the span is exceeding 4.0 m.

3) The web thickness of the frames shall be at least one half of the thickness of the shell plating. Where there is a deck, tank top, bulkhead, web frame or stringer in lieu of a frame, at least one half of the thickness of shell plating shall be kept to a depth of not less than 0.0025 L, minimum

0.2 m.

B 400 Stringers and web frames 401 Stringers situated inside and outside the ice belt shall be as given in Sec.3 E100 - E200. Web frames shall be as given in Sec.3 E200 - F200. The product p·h shall not be taken less than 200.

B 500 Weld connections 501 Weld connections to shell in fore peak shall be double continuous.

B 600 Rudder and steering arrangement 601 The rudder and steering arrangement shall comply with Sec.3 I200, given that the maximum service speed of the vessel is not taken less than 14 knots.

B 700 Stem 701 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60 degrees or more to the centreline in a horizontal plane shall comply with Sec.3 H102 up to 600 mm above UIWL.

C. Machinery C 100 Output of propulsion machinery 101 The maximum continuous output is generally not to be less 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 shall not be less than:

Ps = 0.59 L B (kW) 102 If the ship is fitted with a controllable pitch propeller, the output may be reduced by 25%.

C 200 Design of propeller and propeller shaft 201 The formulae for scantlings are based on the following loads:

To = mean torque of propulsion engine at maximum contin-uous rating in Nm.

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

Tho = mean propeller thrust in N at maximum continuous speed

R = as given in 202 Tice = ice torque in Nm (referred to propeller r.p.m.)

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

Skewed propellers will be especially considered with respect to the risk of blade bending at outer radii if fsk exceeds 1.15 (see 204).

202 The particulars governing the requirements for propeller scantlings are:

R = propeller radius (m) Hr = pitch in m at radius in question θ = rake in degrees at blade tip (backward rake positive) Z = number of blades

Pt.5 Ch.1 Sec.2 – Page 10 t = blade thickness in mm at cylindrical section consid-ered t0.25 = t at 0.25 R t0.35 = t at 0.35 R t0.6 = t at 0.6 R cr = blade width in m at cylindrical section considered c0.25 = cr at 0.25 R c0.35 = cr at 0.35 R c0.6 = cr at 0.6 R e = distance between skew line and generatrix in m at cy-lindrical section considered, positive when skew line is forward of generatrix.

e0.6 = e at 0.6 R e1.0 = e at 1.0 R u = gear ratio:

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

no = propeller speed at maximum continuous output, for which the machinery shall be approved, in revolutions per minute.

203 Propellers and propeller parts (defined in Pt.4 Ch.5 Sec.1 A103) shall be of steel or bronze as specified in Pt.2 Ch.2. Nodular cast iron of Grade NV 1 and NV 2 may be used for relevant parts in CP-mechanism. Other type of nodular cast iron with elongation ≥ 12% may be accepted upon special con-sideration for same purposes.

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

The thickness at 0.6 R shall not be less than:

U1 and U2 = material constants to be taken as given in Pt.4 Ch.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 C1.

A = q0 + q1 d + q2 d2 + q3 d3 q0, q1, q2, q3 = as given in Table C2.

d = d = ki = 96 at 0.25 R = 92 at 0.35 R KMat = 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 pitch propellers and 125% thrust and 100% torque for controllable pitch propellers).

For turbine, diesel-electric or similar propulsion machinery K1 will be considered in each particular case.

Guidance note:

K1 may be calculated for other than diesel driven propellers by replacing the constants 0.85 by 1.1 and 0.75 by 1.0 for FP provid-ed that maximum torque of the driving engine is limited to 100% of the nominal torque. If driving torque exceeds 100%, the torque constant 1.0 shall be multiplied by the ratio Tmax/To and corre-sponding thrust value (Tho times constant) calculated based on the actual maximum torque.

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

The thickness of other sections is governed by a smooth curve connecting the above section thicknesses.

205 If found necessary by the torsional vibration calcula-tions, minor deviations from the dimensions given in 204 may be approved upon special consideration.

206 The section modulus of the blade bolt connection re-ferred to an axis tangentially to the bolt pitch diameter, shall not be less than:

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

The propeller blade foot shall have a strength (including stress concentration) not less than that of the bolts.

207 Fitting of the propeller to the shaft is given in Pt.4 Ch.4 Sec.1 as follows:

— flanged connection in B300

— keyless cone connection in B400 t C1

2RK1 U2C4 0.2+( ) K4+

Zcr K( Mat U1 U2Sr )– ------------------------------------------------------------- (mm)= t t0.35

0.45 fsk c0.35⋅ ⋅ c0.6 --------------------------------------- (mm)=

0.16.0 sk R ee

1f ⎟

Sr = 2Rno

C2θ C3+( )

K1 = A1d T ho0.85 A2+ 0.75uTo

R

K1 = A1d T ho1.25 A2 uTo R

2πR Hr

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

Table C1 Values of C1, C2, C3, C4 r 0.25 R 0.35 R 0.6 R

C1 0.278 0.258 0.150 C2 0.026 0.025 0.020 C3 0.055 0.049 0.034 C4 1.38 1.48 1.69

Table C2 Values of q0, q1, q2, q3 R q0 q1 q2 q3

0.25 R A1

A2

8.30 63.80

0.370 -4.500

-0.340 -0.640

0.030 0.0845

0.35 R A1

A2

9.55 57.30

-0.015 -7.470

-0.339 -0.069

0.0322 0.0472

0.6 R A1

A2

14.60 52.90

-1.720 -10.300

-0.103 0.667

0.0203 0.0

2π R 0.7Hr -------------- for controllable pitch propellers d2 16+

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

2.86 d2 8.18+

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

Wb 0.1 c0.35 t0.35 2 σb σy ------ cm3( )=

Pt.5 Ch.1 Sec.2 – Page 11

— keyed cone connection in B500.

(Considering 0°C seawater temperature) If the propeller is bolted to the propeller shaft, the bolt connec-tion shall have at least the same bending strength as the propel-ler shaft.

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

208 The propeller shaft diameter need not exceed 1.05 times the rule diameter given for main class, irrespective of the di-mension required below.

The diameter of the propeller shaft at the aft bearing shall not 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 202 t0.35 = as defined in 202.

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 intermediate shaft, but not less than the actual diameter of the intermediate shaft.

C 300 Sea suctions and discharges 301 The sea cooling water inlet and discharge for main and auxiliary engines shall be so arranged so that blockage of strums and strainers by ice is prevented. In addition to require-ments in Pt.4 Ch.1 and Ch.6 the requirements in 302 and 303 shall be complied with.

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

303 A full capacity discharge branched off from the cooling water overboard discharge line shall be connected to at least one of the sea inlet chests. At least one of the fire pumps shall be 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 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.

D. Requirements for the Class Notation ICE-E D 100 General 101 The requirements for the forward ice belt region, as de-fined in Sec.3 Fig.1, shall, for sub-section elements 200 - 400, be in accordance with Sec.3 as follows:

— In Table B1, the value of ho and h shall be as given for

ICE-1C.

— The ice pressure shall be determined in accordance with Sec.3 B200 where:

- For determination of k, the machinery output, Ps need not be taken >750 kW.

- The factor c1, as given in Table B3, shall be taken as equal to 0.3.

D 200 Plating 201 In the forward ice belt region, as defined in 101, the shell plate thickness shall be as given in Sec.3 C.

202 The vertical extension of the ice strengthening, as given in Sec.3 C100, shall be as given for notation ICE-C.

D 300 Framing 301 In the forward ice belt region as defined in 101, the frames shall be as given in Sec.3 D100 - D300.

302 The framing shall extend vertically not less than 0.62 m above the UIWL and 1.0 m below the LIWL.

303 For the forward ice belt region tripping brackets shall be fitted as given in B301.

D 400 Stem 401 The plate thickness of a shaped plate stem and any part of the bow which forms an angle of 60 degrees or more to the centreline in a horizontal plane shall comply with Sec.3 H102 up to 600 mm above UIWL.

dp 11.5 σbC0.35t0.35 σy

(mm)=

Pt.5 Ch.1 Sec.3 – Page 12

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 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 DNV ice classes are accepted as equivalent to the Finnish- Swedish ice classes. (Extract of the Finnish Maritime Adminis-tration Bulletin No. 16/27.11.2002).

Revision of the Finnish-Swedish Ice Class Rules of 1 October 2002 concern propulsion power and structural strength and ap-plies to ships of which the keel is laid, or which is at a similar stage of construction on or after 1 September 2003, and was im-plemented into the DNV rules in January 2003.

103 Vessels built in compliance with the requirements rele-vant 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 as-sistance.

A 200 Assumptions 201 The method for determining the hull scantlings, engine output and other properties are based on certain assumptions concerning the nature of the ice load on the structure and oper-ation of the ship as described in the Finnish-Swedish Ice Class Rules. 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 redistri-bution 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 meth-ods 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 Extent of ice strengthening The extent of the ice strengthening is determined from the Up-per Ice Water Line (UIWL) and the Lower Ice Water Line (LI- WL), which defines the extreme draughts, see Sec.1.

302 Transit in ballast condition The minimum forward draught shall be at least:

(2 + 0.00025 Δf) ho (m) but need not exceed 4 ho where

Δf = displacement of the ship (t) on the maximum ice class draught according to 301 ho = ice thickness according to Table B1.

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 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 requirements 401 Document requirements are shown in Table A2. For a full definition of the documentation types, see Pt.0 Ch.3

DNV Ice Class notation Equivalent Finnish-Swedish Ice Class

ICE-1A* 1A Super

ICE-1A 1A

ICE-1B 1B

ICE-1C 1C

Table A1 Operation of the ship

ICE-1A* normally capable of navigating in difficult ice conditions without the assistance of icebreakers

ICE-IA

capable of navigating in difficult ice conditions, with the assistance of icebreakers when neces-sary

ICE-IB

capable of navigating in moderate ice condi-tions, with the assistance of icebreakers when necessary

ICE-IC

capable of navigating in light ice conditions, with the assistance of icebreakers when neces-sary

Pt.5 Ch.1 Sec.3 – Page 13 402 UIWL and LIWL shall 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, Δf, and the output of propulsion machinery, Ps, shall be stated on the shell expansion and/or the framing plan.

Fig. 1 Ice belt regions

403 For a full definition of the documentation types, see Pt.0 Ch.3.

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 ex-ceeding ho. 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 ho and h are given in the following table.

B 200 Ice pressure 201 The design ice pressure (based on a nominal ice pressure of 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 size and engine output of the ship. It is calculated by the formula:

a and b are given in Table B2.

Δf = displacement (t) as defined in A302 Ps = machinery output (kW) as defined in J101 c1 = 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 A2 Document requirements Object Documentation type Additional description For approval (AP) or

For information (FI)

Ship hull H060 – Shell expansion drawing

UIWL and LIWL shall be indicated together with the lines separating the forward, amidships and aft regions of the ice belt, see 402.

AP

Ship Z100 – Specification Displacement, machinery type, propulsion power. FI

Propulsion line C040 – Design analysis Applicable if a first blade order torsional resonance is within operational speed range +/- 20%. Torsional vibration analysis of ice torque response.

AP

Propeller blades C040 – Design analysis Final element analysis of blade stresses introduced by ice loads. AP

Propulsion system C040 – Design analysis Applicable for alternative designs, not applying loads defined in the rules. Comprehensive design analysis of entire system. AP

Table B1 Values of ho and h Ice class ho (m) h (m)

ICE-1A*

ICE-1A

ICE-1B

ICE-1C

1.0 0.8 0.6 0.4

0.35 0.30 0.25 0.22

Table B2 Values of a and b Region

Forward Midship and aft k ≤ 12 k > 12 k ≤ 12 k > 12 a 30 6 8 2 b 230 518 214 286 cd ak b+ k ΔfPs

Pt.5 Ch.1 Sec.3 – Page 14 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 the full length of the area under consideration will be under pressure at the same time. It is calculated by the formula:

la shall be taken as given in Table B4.

C. Shell Plating C 100 Vertical extension of ice strengthening 101 The vertical extension of the ice belt (see Fig.1) shall not be 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 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 exceed-ing 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, shall have at least the thick-ness 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.

For ice class ICE-1A*F the upper forward ice belt shall be taken 3 m above the normal ice belt, extending within the forward region.

Lower forward ice belt: For ice class ICE-1A*F a lower for-ward 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 shall not 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 shall be given at least the same strength as is required for the shell in the ice belt. The strength of the con-struction of the freeing ports shall meet the same requirements.

C 200 Plate thickness in the ice belt 201 For transverse framing the thickness of the shell plating shall be determined by the formula:

For longitudinal framing the thickness of the shell plating shall be determined by the formula:

p PL = 0.75 p p = 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 > 3 h = as given in B100 σ F = yield stress of the material (N/mm2) tc = 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 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) shall have a thickness not less than:

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

Table B3 Values of c1

Ice class Region

Forward Midship Aft

ICE-1A* 1.0 1.0 0.75

ICE-1A 1.0 0.85 0.65

ICE-1B 1.0 0.70 0.45

ICE-1C 1.0 0.50 0.25

Table B4 Values of la Structure Type of framing la

Shell transverse frame spacing longitudinal 2 × frame spacing

Frames transverse frame spacing longitudinal span of frame Ice stringer span of stringer Web frame 2 × web frame spacing

Table C1 Vertical extension of ice belt Ice class Above UIWL (m) Below LIWL (m)

ICE-1A*

ICE-1A

ICE-1B

ICE-1C

0.6 0.5 0.4 0.4

0.75 0.6 0.5 0.5 ca 47 5la–

-------------------, maximum 1.0, minimum 0.6= t 21.1s x1 p PL σ F

------------------ tc (mm)+= t 21.1s p PL x2σ F ------------ tc (mm)+=

1.3 4.2 h s⁄ 1.8+( )2 ---------------------------------– , maximum 1.0

0.6 0.4 h s⁄( )

---------------- , when h/s 1≤+ t 0.7 s 0.8+( ) 235L σ F

------------- (mm), minimum 12 mm= t 0.6 s 0.8+( ) 235L σ F

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

Pt.5 Ch.1 Sec.3 – Page 15 D. Frames D 100 Vertical extension of ice framing 101 The vertical extension of the ice strengthening of the framing shall be at least as given in Table D1:

Where an upper forward ice belt is required (see C102), the ice strengthened part of the framing shall 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 trans-verse frame shall be calculated by the formula:

p = ice pressure as given in B200 h = height of load area as given in B100 mt = mo = values as given in Table D2.

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 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 = 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

1) The upper end of the strengthened part of a main frame and of an intermediate ice frame shall 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 string-er 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

Table D1 Vertical extension of ice strengthening of the framing Ice class Region Above UIWL

(m) Below LIWL

(m)

ICE- 1A*F

forward 1.2 to double bottom or below top of floors midship 1.2 1.6 aft 1.2 1.2

ICE-1A*

from stem to

0.3 L abaft it 1.2

to double bottom or below top of floors abaft 0.3 L from stem 1.2 1.6 midship 1.2 1.6 aft 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 1.3 aft 1.0 1.0

Z p s h l mtσ F ---------------103 cm3( )=

7mo 7 5h l⁄–

Table D2 Values of mo Boundary condition 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

Z ps h b l b–( )2 σF l2 ---------------------------------- 103 cm3( )=

Pt.5 Ch.1 Sec.3 – Page 16

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 shall 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 shall be cal-culated by the formula:

The shear area of a longitudinal frame shall be:

These formulae assume that the longitudinal frame is attached to supporting structure as required in 401.

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

x3 = (1 − 0.2 h/s) x4 = factor which takes account of the concentration of load to the point of support:

x4 = 0.6 p = ice pressure as given in B200 h = height of load area as given in B100 m1 = boundary condition factor; m1 = 11 shall be used for continuous longitudinals. Where the boundary condi-tions deviate significantly from a continuous beam, a smaller factor may be required.

D 400 Structural details 401 Within the ice strengthened area all frames shall be ef-fectively attached to all supporting structures. Longitudinal or transverse frames crossing supporting structures, such as web frames or stringers, shall be connected to these structures on both sides (by collar plates or lugs in way of cut-outs).

Brackets or top stiffeners shall be fitted, in order to provide proper transfer of forces to supporting elements, as necessary.

Connection of non-continuous frames to supporting structures shall be made by brackets or similar construction. When a bracket is installed, it has to have at least the same thickness as the web plate of the frame, and the edge shall be appropriately stiffened against buckling.

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 shall be supported against tripping by brackets, intercostals, stringers or similar at a distance preferably not exceeding

1.3 m.

Transverse frames perpendicular to shell which are of un-symmetrical profiles shall have tripping preventions if the span is exceeding 4.0 m.

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

3) The web thickness of the frames shall be minimum 9 mm and at least one half of the shell plating requirement as giv-en by C201, where the yield stress, σF, shall not be taken larger than that given for the frame.

The frame spacing, s, need not be taken larger than 0.45 m.

Where there is a deck, tank top or bulkhead in lieu of a frame, the plate thickness of this shall 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) shall be calculated by the formula:

The shear area shall not be less than:

p = ice pressure as given in B200 h = height of load area as given in B100

The product p h shall not be taken as less than 300 l = span of stringer (m) m1 = 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 shall be calculated by the formula:

The shear area shall not be less than:

p = ice pressure as given in B200 h = height of load area as given in B100

The product p h shall not 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 strips 301 Narrow deck strips abreast of hatches and serving as ice stringers shall 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 200.

302 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.

Z x3 x4 p h l2 m1σF -------------------------- 103 cm3( )=

A

8.7 x3p h l σF ------------------------- cm2( )=

Z 0.9 p h l2 m1σ F --------------------- 103 cm3( )=

A 7.8 p h l σ F

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

Z 0.95 p h l2 m1σ F ------------------------ 1 hs ls

⎛ ⎞ 103 cm3( )=

A 8.2 p h l σ F

------------------- 1 hs ls

⎛ ⎞ cm2( )=

Pt.5 Ch.1 Sec.3 – Page 17 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 formu-la:

F = p h s (kN) p = ice pressure as given in B200, when calculating factor ca, however, la shall be taken as 2 s h = height in m of load area as given in B100

The product ph shall not 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 require-ment is given by:

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 Aa = 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:

Q = maximum calculated shear force under the load F, as given in 101 α = factor given in Table F1 Af = cross sectional area of free flange Aw = cross sectional area of web plate.

203 For other web frame configurations and boundary con-ditions 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:

G. Bilge Keels G 100 Arrangement 101 The connection of bilge keels to the hull shall be so de-signed 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 par-ticularly for smaller ships with length less than 150 m.

hs ls

Z M σF ------ 1

1 γ A Aa

⎛ ⎞ 2

--------------------------103 (cm3 )=

A 17.3α Q σF

-------------------- (cm2 )= τ σF 3⁄= σb σF= σc σb 2 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

Pt.5 Ch.1 Sec.3 – Page 18 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, shall be calculated according to…