INTERNATIONAL NAVAL SHIPS 2018

Transcription

1 GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS 2018 NOTICE NO. 3 July 2018 The following Rule Changes were approved by the ABS Rules Committee on 1 June 2018 and become EFFECTIVE AS OF 1 JULY (See for the consolidated version of the Guide for Building and Classing International Naval Ships 2018, with all Notices and Corrigenda incorporated.) Notes - The date in the parentheses means the date that the Rule becomes effective for new construction based on the contract date for construction, unless otherwise noted. (See 1-1-4/3.3 of the ABS Rules for Conditions of Classification (Part 1).) PART 3 CHAPTER 2 SECTION 1 HULL CONSTRUCTION AND EQUIPMENT HULL STRUCTURES AND ARRANGEMENTS LONGITUDINAL STRENGTH 5 Longitudinal Strength with Higher-Strength Materials (Revise Paragraph 3-2-1/5.3, as follows:) 5.3 Hull Girder Section Modulus (1 July 2018) When either the top or bottom flange of the hull girder, or both, is constructed of material other than mild steel, the section modulus, as obtained from 3-2-1/3.1 and 3-2-1/3.5, may be reduced by the factor Q. SM q = Q (SM) where Note: SM = section modulus as obtained from 3-2-1/3.5 Q = 0.78 for H32 strength steel Q = 0.72 for H36 strength steel Q = 0.68 (1) for H40 strength steel H32, H36, H40 = as specified in Section of the ABS Rules for Materials and Welding (Part 2) 1 The material factor for H40 may be taken as 0.66, provided that the hull structure is additionally verified for compliance with the requirements of: ABS Guide for SafeHull-Dynamic Loading Approach for Vessels ABS Guide for Spectral-Based Fatigue Analysis for Vessels (Following text remains unchanged.) ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

2 PART 3 CHAPTER 2 SECTION 7 HULL CONSTRUCTION AND EQUIPMENT HULL STRUCTURES AND ARRANGEMENTS BEAMS (Revise Subsection 3-2-7/5 and add new 3-2-7/Figures 2, 3, and 4, as follows:) 5 Deck Fittings Support Structures (1 July 2018) 5.1 General The strength of supporting hull structures in way of shipboard fittings used for mooring operations and/or towing operations as well as supporting hull structures of winches and capstans at the bow, sides and stern are to comply with the requirements of this section, where towing operations are defined as follows: Normal Towing Normal towing is the towing operations necessary for maneuvering in ports and sheltered waters associated with the normal operations of the vessel Other Towing For vessels not subject to SOLAS Regulation II-1/3-4 Paragraph 1 but fitted with equipment for towing by another vessel or a tug (e.g., such as to assist the vessel in case of emergency as given in SOLAS Regulation II-1/3-4 Paragraph 2), the requirements designated as other towing are to be applied to design and construction of those shipboard fittings and supporting hull structures. The requirements of this section do not apply to design and construction of shipboard fittings and supporting hull structures used for special towing services, as follows: Escort Towing. Towing service, in particular, for laden oil tankers or LNG carriers, required in specific estuaries. Its main purpose is to control the vessel in case of failures of the propulsion or steering system. Reference should be made to local escort requirements and guidance given by, for example, the Oil Companies International Marine Forum (OCIMF). Canal Transit Towing. Towing service for vessels transiting canals (e.g., the Panama Canal). Reference should be made to local canal transit requirements. Emergency Towing for Tankers. Towing service to assist tankers in case of emergency. For the emergency towing arrangements, vessels subject to SOLAS regulation II-1/3-4 Paragraph 1 are to comply with that regulation and resolution MSC.35(63) as amended. Shipboard fittings for mooring and/or towing, winches and capstans are to be located on stiffeners and/or girders, which are part of the deck construction so as to facilitate efficient distribution of the mooring and/or towing load. The same attention is to be paid to recessed bitts, if fitted, of their structural arrangements and strength of supporting structures. Other arrangements may be accepted (for chocks in bulwarks, etc.) provided the strength is confirmed adequate for the intended service. The requirements in this subsection are to be applied in conjunction with the requirements for mooring and towing equipment contained in Section Design Loads Unless greater safe working load (SWL) and/or safe towing load (TOW) of shipboard fittings is specified by the applicant (see 3-2-7/5.3.3), the minimum design load to be used is the greater values obtained from 3-2-7/5.3.1 or 3-2-7/5.3.2, whichever is applicable: Mooring Operations The minimum design load for shipboard fittings for mooring operations is the applicable value obtained from 3-2-7/5.3.1(a) or 3-2-7/5.3.1(b): 2 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

3 5.3.1(a) Mooring Line Force. The minimum design load applied to supporting hull structures for shipboard fittings is to be 1.15 times the minimum breaking strength of the mooring line according to 3-5-1/Table 2. See Notes 1 and 2 in 3-2-7/5.3.1(b) (b) Mooring Winch Force. The minimum design load applied to supporting hull structures for winches is to be 1.25 times the intended maximum brake holding load, where the maximum brake holding load is to be assumed not less than 80% of the minimum breaking strength of the mooring line according to 3-5-1/Table 2. See Notes 1 and 2. For supporting hull structures of capstans, 1.25 times the maximum hauling-in force is to be taken as design load. Notes: 1 If not otherwise specified by Section 3-5-1, side projected area including that of deck cargoes as given by the loading manual is to be taken into account for selection of mooring lines and the loads applied to shipboard fittings and supporting hull structure. 2 The increase of the minimum breaking strength for synthetic ropes according to 3-5-1/19.7 needs not to be taken into account for the loads applied to shipboard fittings and supporting hull structure Towing Operations The minimum design load for shipboard fittings for towing operations is the applicable value obtained from 3-2-7/5.3.2(a) through 3-2-7/5.3.2(c), as applicable (a) Normal Towing Operations times the intended maximum towing load (e.g., static bollard pull) as indicated on the towing and mooring arrangements plan (b) Other Towing Service. The minimum breaking strength of the tow line according to the 3-5-1/Table 3 for each equipment number (EN). EN is the corresponding value used for determination of the vessel s equipment. (See Notes 1 and 2) Notes: 1 Side projected area including that of deck cargoes as given by the loading manual is to be taken into account for selection of towing lines and the loads applied to shipboard fittings and supporting hull structure. 2 The increase of the minimum breaking strength for synthetic ropes according to 3-5-1/19.7 needs not to be taken into account for the loads applied to shipboard fittings and supporting hull structure (c) For fittings intended to be used for, both, normal and other towing operations, the greater of the design loads according to 3-2-7/5.3.2(a) and 3-2-7/5.3.2(b) Application of Design Loads The design load is to be applied to fittings in all directions that may occur by taking into account the arrangement shown on the towing and mooring arrangements plan. Where the towing line takes a turn at a fitting, the total design load applied to the fitting is equal to the resultant of the design loads acting on the line, see 3-2-7/Figure 1 below. However, in no case does the design load applied to the fitting need to be greater than twice the design load on the line. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

4 FIGURE 1 Application of Design Loads Design Load on Line Design Load on Fitting (Not more than 2 times design load on line) Design Load on Line Fitting When a specific SWL is applied for a shipboard fitting at the request of the applicant, by which the design load will be greater than the above minimum values, the strength of the supporting hull structures is to be designed for an increased load in accordance with the appropriate SWL/design load relationship given by 3-2-7/5.3 and 3-5-1/ When a safe towing load, TOW, greater than that determined according to 3-5-1/ is requested by the applicant, the design load is to be increased in accordance with the appropriate TOW/design load relationship given by 3-2-7/5.3 and 3-5-1/ Supporting Structures Arrangement and Applied Design Load The design load applied to supporting hull structure for mooring operations and towing operations is to be in accordance with 3-2-7/5.3.1 and 3-2-7/5.3.2, respectively. The arrangement of reinforced members beneath shipboard fittings, winches, and capstans is to consider any variation of direction (horizontally and vertically) of the mooring forces acting upon the shipboard fittings, see 3-2-7/Figure 2 for a sample arrangement. Proper alignment of fitting and supporting hull structure is to be verified. FIGURE 2 Sample Arrangement (1 July 2018) Reinforcing members beneath shipboard fittings Fitting on deck (e.g., bollard, chock) Main hull structure (e.g., web frames, deck stiffeners) 4 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

5 5.5.2 Line Forces The acting point of the mooring and/or towing force on shipboard fittings is to be taken at the attachment point of a mooring line or a towing line, as applicable and as described below (a) Mooring Operations. The acting point of the mooring force on shipboard fittings is to be taken at the attachment point of a mooring line or at a change in its direction. For bollards and bitts the attachment point of the mooring line is to be taken 4 / 5 of the tube height above the base, see a) in 3-2-7/Figure 3 below. If fins are fitted to the bollard tubes to keep the mooring line as low as possible, the attachment point of the mooring line may be taken at the location of the fins, see b) in 3-2-7/Figure 3 below. FIGURE 3 Attachment Point of Mooring Line (1 July 2018) Design Load on Line a) H H4/5 b) 5.5.2(b) Towing Operations. The acting point of the towing force on shipboard fittings is to be taken at the attachment point of a towing line or at a change in its direction. For bollards and bitts the attachment point of the towing line is to be taken not less than 4 / 5 of the tube height above the base, see 3-2-7/Figure 4 below. FIGURE 4 Attachment Point of Towing Line (1 July 2018) Design Load on Line H H4/5 Eye Splice ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

6 5.5.3 Allowable Stresses Allowable stresses under the design load conditions as specified in 3-2-7/5.3 are as follows: 5.7 Scantlings 5.5.3(a) For strength assessment with beam theory or grillage analysis: Normal stress: 100% of the specified minimum yield point of the material Shearing stress: 60% of the specified minimum yield point of the material Normal stress is the sum of bending stress and axial stress with the corresponding shearing stress acting perpendicular to the normal stress. No stress concentration factors being taken into account (b) For strength assessment with finite element analysis: Equivalent stress: 100% of the specified minimum yield point of the material. For strength calculations by means of finite elements, the geometry is to be idealized as realistically as possible. The ratio of element length to width is not to exceed 3. Girders are to be modelled using shell or plane stress elements. Symmetric girder flanges may be modelled by beam or truss elements. The element height of girder webs is not to exceed one-third of the web height. In way of small openings in girder webs the web thickness is to be reduced to a mean thickness over the web height. Large openings are to be modelled. Stiffeners may be modelled by using shell, plane stress, or beam elements. Stresses are to be read from the center of the individual element. For shell elements the stresses are to be evaluated at the mid plane of the element Net Scantlings The net minimum scantlings of the supporting hull structure are to comply with the requirements given in 3-2-7/5.5. The net thicknesses, t net, are the member thicknesses necessary to obtain the above required minimum net scantlings. The required gross thicknesses are obtained by adding the total corrosion additions, t c, given in 3-2-7/5.7.2 and, where applicable, the wear allowance, t w, given in 3-2-7/5.7.3 to t net Corrosion Addition The corrosion addition, t c, is not to be less than the following values: For the supporting hull structure, according to 7-A-4/Table 1 of the ABS Rules for Survey After Construction (Part 7) for the surrounding structure. For pedestals and foundations on deck which are not part of a fitting according to an accepted industry standard, 2.0 mm (0.08 in.). For shipboard fittings not selected from an accepted industry standard, 2.0 mm (0.08 in.) Wear Allowance In addition to the corrosion addition given in 3-2-7/5.7.2 the wear allowance, t w, for shipboard fittings not selected from an accepted industry standard is not to be less than 1.0 mm (0.04 in.), added to surfaces which are intended to regularly contact the line. 6 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

7 PART 3 CHAPTER 2 SECTION 18 HULL CONSTRUCTION AND EQUIPMENT HULL STRUCTURES AND ARRANGEMENTS PROTECTIVE COATINGS 5 Corrosion Protection of Steel (Revise Paragraph /5.1, as follows:) 5.1 All Spaces (1 July 2018) Unless otherwise approved, all steel surfaces are to be suitably protected by an efficient corrosion prevention system, such as protective coatings and/or cathodic protection as applicable. For more details, refer to the ABS Guidance Notes on Cathodic Protection of Ships and the ABS Guidance Notes on the Application and Inspection of Marine Coating Systems. PART 3 CHAPTER 5 SECTION 1 HULL CONSTRUCTION AND EQUIPMENT EQUIPMENT ANCHORING, MOORING, AND TOWING EQUIPMENT 1 General (1 July 2018) (Revise Subsection 3-5-1/1, as follows:) All naval vessels are to have a complete equipment set of anchor(s) and chains. The letter Á placed after the symbols of classification in the Record, thus: À A1 Á, will signify that the equipment of the vessel is in compliance with the requirements of this Guide, and tested in accordance with 3-5-1/7, or with requirements, which have been specially approved for the particular service. Cables which are intended to form part of the equipment are not to be used as deck chains when the vessel is launched. The inboard ends of the cables of the bower anchors are to be secured by efficient means (see 3-5-1/15). Anchors and their cables are to be connected and positioned, ready for use. Means are to be provided for stopping each cable as it is paid out, and the windlass should be capable of heaving in either cable. Suitable arrangements are to be provided for securing the anchors and stowing the cables. See 3-5-1/16. Equipment Number calculations for unconventional vessels with unique topside arrangements or operational profiles may be specially considered. Such consideration may include accounting for additional wind areas of widely separated deckhouses or superstructures in the equipment number calculations or equipment sizing based on direct calculations. However, in no case may direct calculations be used to reduce the equipment size to be less than that required by 3-5-1/3. The strength of supporting hull structures in way of shipboard fittings used for mooring operations and towing operations as well as supporting hull structures of winches and capstans at the bow, sides, and stern are to comply with the requirements of 3-2-7/5. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

8 3 Calculation of EN (1 July 2018) (Revise Subsection 3-5-1/3, as follows:) The basic Equipment Number (EN) is to be obtained from the following equation for use in determining required equipment. where EN = k 2/3 + m(ba + Σbh) + na k = 1.0 (1.0, 1.012) m = 2 (2, 0.186) n = 0.1 (0.1, ) = molded displacement, in metric tons (long tons), at the summer load waterline. B = molded breadth, as defined in 3-1-1/3.3, in m (ft) a = freeboard, in m (ft), from the light waterline amidships. b = breadth, in m (ft), of the widest superstructure or deckhouse on each tier. h = effective height, in m (ft), from the Summer Load waterline to the top of the uppermost house; for the lowest tier h is to be measured at centerline from the upper deck or from a notional deck line where there is local discontinuity in the upper deck, as shown in 3-5-1/Figure 1A h 1, h 2, h 3,... as shown in 3-5-1/Figure 1A. In the calculation of h, sheer and trim may be neglected. h 1, h 2, h 3 = height, in m (ft), on the centerline of each tier of houses having a breadth greater than B/4. A = side-projected area, in m 2 (ft 2 ), of the hull, superstructure and houses above the summer load waterline which are within the Rule length. Superstructures or deck houses having a breadth at any point no greater than 0.25B may be excluded. Screens and bulwarks more than 1.5 m (4.9 ft) in height are to be regarded as parts of houses when calculating h and A. The height of the hatch coamings and that of any deck cargo, such as containers, may be disregarded when determining h and A, except as specified by 3-5-1/19.3 for mooring lines. With regard to determining A, when a bulwark is more than 1.5 m (4.9 ft) high, the area shown below as A 2 should be included in A. 1.5 m (4.9 ft) A 2 F.P. 8 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

9 (Revise 3-5-1/Figure 1, as follows:) FIGURE 1 Effective Heights of Deck Houses (1 July 2018) h3 h2 h1 a A B Summer Load Waterline B/8 h 3 h 2 Notional Deck Line h 1 Upper Deck a Summer Load Waterline 11 Windlass Support Structure and Cable Stopper 11.3 Support Structure Operating Loads (Revise Item 3-5-1/11.3.1(c), as follows:) (c) Allowable Stress (1 July 2018). The allowable stresses for the structures supporting the windlass and cable stopper are as follows: Normal stress: 100% of the specified minimum yield stress of the material Shear stress: 60% of the specified minimum yield stress of the material (Add new Item 3-5-1/11.3.1(d), as follows:) (d) The net minimum scantlings of the supporting hull structure are to comply with the requirements given in 3-5-1/11.3.1(c). The required gross scantlings are determined according to 3-2-7/5.7. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

10 Sea Loads (Revise Item 3-5-1/11.3.2(d), as follows:) (d) Allowable Stress (1 July 2018) i) Bolts. The safety factor against bolt proof strength is to be not less than 2.0. ii) iii) Supporting Structures. The allowable stresses for the above deck framing and the hull structure supporting the windlass and chain stopper are as follows: Normal stress: 100% of the specified minimum yield stress of the material Shear stress: 60% of the specified minimum yield stress of the material The net minimum scantlings of the supporting hull structure are to comply with the requirements given in 3-5-1/11.3.2(d)ii). The required gross scantlings are determined according to 3-2-7/5.7. (Renumber Subsection 3-5-1/15 as 3-5-1/14.) (Add new Subsections 3-5-1/15 and 3-5-1/16, as follows:) 15 Securing of the Inboard Ends of Chain Cables (1 July 2018) Arrangements are to be provided for securing the inboard ends of the bower anchor chain cables. The chain cables are to be secured to structures by a fastening able to withstand a force not less than 15% nor more than 30% of the breaking load of the chain cable. The fastening is to be provided with a mean suitable to permit, in case of emergency, an easy slipping of the chain cables to sea, operable from an accessible position outside the chain locker. 16 Securing of Stowed Anchors (1 July 2018) Arrangements are to be provided for securing the anchors and stowing the cables. To hold the anchor tight in against the hull or the anchor pocket, respectively, anchor lashings (e.g., a devil s claw ) are to be fitted. Anchor lashings are to be designed to resist a load at least corresponding to twice the anchor mass plus 10 m (32.8 ft) of cable without exceeding 40% of the yield strength of the material. (Revise Subsection 3-5-1/17, as follows:) 17 Bollard, Fairlead and Chocks (1 July 2018) 17.1 General The arrangements and details of shipboard fittings used for mooring operations and/or towing operations at bow, sides and stern are to comply with the requirements of this section. The requirements for the supporting structures of these fittings are specified in 3-2-7/ Shipboard Fittings The size of shipboard fittings is to be in accordance with recognized standards (e.g., ISO Ships and marine technology Ship s mooring and towing fittings Welded steel bollards for sea-going vessels) or comply with the requirements given in 3-5-1/ and 3-5-1/ For shipboard fittings not in accordance with recognized standard the corrosion addition, t c, and the wear allowance, t w, given in 3-2-7/5.7, respectively, are to be considered. The design load used to assess shipboard fittings and their attachments to the hull are to be in accordance with the requirements as specified in 3-2-7/5. 10 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

11 Mooring Operations Shipboard fittings may be selected from a recognized national or international standard. The Safe Working Load (SWL) is to be suitable for mooring lines with a minimum breaking strength that is not less than that according to 3-5-1/Table 2 (see Notes in 3-2-7/5.3.1). Mooring bitts (double bollards) are to be chosen for the mooring line attached in figure-of-eight fashion if the industry standard distinguishes between different methods to attach the line (i.e., figure-of-eight or eye splice attachment). When the shipboard fitting is not selected from an accepted industry standard, the strength of the fitting and of its attachment to the vessel is to be in accordance with requirements related to mooring in 3-2-7/5.3 and 3-2-7/5.5. Mooring bitts (double bollards) are required to resist the loads caused by the mooring line attached in figure-of-eight fashion, see Note. For strength assessment beam theory or finite element analysis using net scantlings is to be applied, as appropriate. Corrosion additions are to be as defined in 3-2-7/ A wear down allowance is to be included as defined in 3-2-7/ Consideration may be given to accepting load tests as alternative to strength assessment by calculations. Note: With the line attached to a mooring bitt in the usual way (figure-of-eight fashion), either of the two posts of the mooring bitt can be subjected to a force twice as large as that acting on the mooring line. Disregarding this effect, depending on the applied industry standard and fitting size, overload may occur Towing Operations Shipboard fittings may be selected from a recognized industry standard and are to be at least based on the following loads: i) For normal towing operations, the intended maximum towing load (e.g., static bollard pull) as indicated on the towing and mooring arrangements plan, ii) iii) For other towing service, the minimum breaking strength of the tow line according to 3-5-1/Table 3 [see Notes in 3-2-7/5.3.2(b)], For fittings intended to be used for, both, normal and other towing operations, the greater of the loads according to i) and ii). Towing bitts (double bollards) may be chosen for the towing line attached with eye splice if the industry standard distinguishes between different methods to attach the line (i.e., figure-of-eight or eye splice attachment). When the shipboard fitting is not selected from an accepted industry standard, the strength of the fitting and of its attachment to the vessel is to be in accordance with requirements related to towing in 3-2-7/5.3 and 3-2-7/5.5. Towing bitts (double bollards) are required to resist the loads caused by the towing line attached with eye splice. For strength assessment beam theory or finite element analysis using net scantlings is to be applied, as appropriate. Corrosion additions are to be as defined in 3-2-7/ A wear down allowance is to be included as defined in 3-2-7/ Consideration may be given to accepting load tests as alternative to strength assessment by calculations Safe Working Load (SWL) and Towing Load (TOW) The requirements on SWL apply for a single post basis (no more than one turn of one cable) Mooring Operations i) The Safe Working Load (SWL) is the load limit for mooring purpose. ii) iii) iv) Unless a greater SWL is requested by the applicant according to 3-2-7/5.3.3, the SWL is not to exceed the minimum breaking strength of the mooring line according to 3-5-1/Table 2, see Notes in 3-2-7/ The SWL, in tonnes, of each shipboard fitting is to be marked (by weld bead or equivalent) on the fittings used for mooring. For fittings intended to be used for both, mooring and towing, TOW, in tonnes, according to 3-5-1/ is to be marked in addition to SWL. The above requirements on SWL apply for the use with no more than one mooring line. v) The towing and mooring arrangements plan mentioned in 3-5-1/17.7 is to define the method of use of mooring lines. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

12 Towing Operations i) The Safe Towing Load (TOW) is the load limit for towing purpose. ii) iii) iv) TOW used for normal towing operations is not to exceed 80% of the design load per 3-2-7/5.3.2(a). TOW used for other towing operations is not to exceed 80% of the design load according to 3-2-7/5.3.2(b). For fittings used for both normal and other towing operations, the greater of the safe towing loads according to ii) and iii) is to be used. v) For fittings intended to be used for both towing and mooring, the requirements in 3-2-7/5 and 3-5-1/17 applicable to mooring are to be applied relative to mooring operations. vi) vii) viii) TOW, in tonnes, of each shipboard fitting is to be marked (by weld bead or equivalent) on the fittings used for towing. For fittings intended to be used for both towing and mooring, SWL, in tonnes, according to 3-5-1/ is to be marked in addition to TOW. The above requirements on TOW apply for the use with no more than one line. If not otherwise chosen, for towing bitts (double bollards) TOW is the load limit for a towing line attached with eye-splice. The towing and mooring arrangements plan mentioned in 3-5-1/17.7 is to define the method of use of towing lines Marking and Plan (a) Marking. The SWL of each shipboard fitting is to be marked (by weld bead or equivalent) on the fittings used for towing/mooring (b) Plan. The towing and mooring arrangements plan mentioned in 3-5-1/17.7 is to define the method of use of mooring lines and/or towing lines Towing and Mooring Arrangements Plan The SWL and TOW for the intended use for each shipboard fitting is to be noted in the towing and mooring arrangements plan available on board for the guidance of the Master. Information provided on the plan is to include in respect of each shipboard fitting: Location on the vessel; Fitting type; SWL and TOW; Purpose (mooring/harbor towing/other towing); and Manner of applying towing or mooring line load including limiting fleet angles. The above information is to be incorporated into the pilot card in order to provide the pilot proper information on harbor/other towing operations. In addition, the towing and mooring arrangement plan is to include the following general information: The arrangement of mooring lines showing number of lines (N); The minimum breaking strength of each mooring line (MBL); The acceptable environmental conditions as given in 3-5-1/ for the recommended minimum breaking strength of mooring lines for vessels with Equipment Number EN > 2000: - 30 second mean wind speed from any direction (v W or v W * according to 3-5-1/19.3.2) - Maximum current speed acting on bow or stern (±10 ) 12 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

13 (Revise Subsection 3-5-1/19, as follows:) 19 Mooring and Towing Equipment (1 July 2018) Except as indicated in 3-5-1/17.7, hawsers, towlines, and requirements for associated equipment and arrangements as described in in 3-5-1/19.9 and 3-5-1/19.11 are not required as a condition of classification. The hawsers and towlines listed in 3-5-1/Table 2 and 3-5-1/Table 3 are intended as a minimum guide Mooring Lines The mooring lines for vessels with Equipment Number EN of less than or equal to 2000 are given in 3-5-1/ For other vessels, the mooring lines are given in 3-5-1/ The Equipment Number EN is to be calculated in compliance with 3-5-1/3. Deck cargo as given by the loading manual should be included for the determination of side-projected area A Mooring Lines for Vessels with EN 2000 The minimum mooring lines for vessels having an Equipment Number EN of less than or equal to 2000 are given in 3-5-1/Table 2 is intended as a guide. For vessels having an A/EN ratio greater than 0.9 for SI or MKS units (9.7 for US units), the number of hawsers given in 3-5-1/Table 2 is to be increased by the number given below: SI Units MKS Units A/EN Ratio U.S. Units Increase number of hawsers by Above 0.9 up to 1.1 above 9.7 up to Above 1.1 up to 1.2 above 11.8 up to above 1.2 above Mooring Lines for Vessels with EN > 2000 The minimum strength and number of mooring lines for vessels with an Equipment Number EN > 2000 are given in 3-5-1/19.3.2(a) and 3-5-1/19.3.2(b), respectively, and is intended as a guide. The length of mooring lines is given by 3-5-1/ The strength of mooring lines and the number of head, stern, and breast lines (see Note below defining head, stern, and breast lines) for vessels with an Equipment Number EN > 2000 are based on the side-projected area A 1. Side projected area A 1 should be calculated similar to the sideprojected area A according to 3-5-1/3 but considering the following conditions: For oil tankers, chemical tankers, bulk carriers, and ore carriers the lightest ballast draft is to be considered for the calculation of the side-projected area A 1. For other vessels the lightest draft of usual loading conditions is to be considered if the ratio of the freeboard in the lightest draft and the full load condition is equal to or above two. Usual loading conditions are loading conditions as given by the trim and stability booklet that are expected to regularly occur during operation and, in particular, that exclude light weight conditions, propeller inspection conditions, etc. Wind shielding of the pier may be considered for the calculation of the side-projected area A 1 unless the vessel is intended to be regularly moored to jetty type piers. A height of the pier surface of 3 m (9.8 ft) over waterline may be assumed (i.e., the lower part of the sideprojected area with a height of 3 m (9.8 ft) above the waterline) for the considered loading condition and may be disregarded for the calculation of the side-projected area A 1. Deck cargo as given by the loading manual is to be included for the determination of sideprojected area A 1. Deck cargo may not need to be considered if a usual light draft condition without cargo on deck generates a larger side-projected area A 1 than the full load condition with cargo on deck. The larger of both side-projected areas is to be chosen as side-projected area A 1. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

14 The mooring lines as given here under are based on a maximum current speed of 1.0 m/s (3.3 ft/s) and the following maximum wind speed v w, in m/s (ft/s): v w = (A ) m/s for passenger vessels, ferries, and car carriers with 2000 m 2 < A m 2 = 21.0 m/s for passenger vessels, ferries, and car carriers with A 1 > 4000 m 2 = 25.0 m/s for other vessels = (A ) ft/s for passenger vessels, ferries, and car carriers with ft 2 < A ft 2 = 68.9 ft/s for passenger vessels, ferries, and car carriers with A 1 > ft 2 = 82.0 ft/s for other vessels The wind speed is considered representative of a 30 second mean speed from any direction and at a height of 10 m (32.8 ft) above the ground. The current speed is considered representative of the maximum current speed acting on bow or stern (±10 ) and at a depth of one-half of the mean draft. Furthermore, it is considered that vessels are moored to solid piers that provide shielding against cross current. Additional loads caused by, e.g., higher wind or current speeds, cross currents, additional wave loads, or reduced shielding from non-solid piers may need to be particularly considered. Furthermore, it should be observed that unbeneficial mooring layouts can considerably increase the loads on single mooring lines. Note: The following is defined with respect to the purpose of mooring lines, see also figure below: Breast Line: A mooring line that is deployed perpendicular to the vessel, restraining the vessel in the off-berth direction. Spring Line: A mooring line that is deployed almost parallel to the vessel, restraining the vessel in the fore or aft direction. Head/Stern Line: A mooring line that is oriented between longitudinal and transverse direction, restraining the vessel in the off-berth and in fore or aft direction. The amount of restraint in the fore or aft and off-berth directions depends on the line angle relative to these directions. Stern Line Breast Line Spring Lines Breast Line Head Line (a) Minimum Breaking Strength. The minimum breaking strength, in kn (kgf, lbf), of the mooring lines should be taken as: MBL = 0.1 A kn MBL = A kgf MBL = A lbf 14 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

15 The minimum breaking strength may be limited to 1275 kn (130,000 kgf, 286,600 lbf). However, in this case the moorings are to be considered as not sufficient for environmental conditions given by 3-5-1/ For these vessels, the acceptable wind speed v w *, in m/s, can be estimated as follows: MBL* 21 v w 2 MBL for v w in m/s where 68.9 MBL* v w 2 MBL for v w in ft/s v w = wind speed as per 3-5-1/ MBL* = MBL = breaking strength of the mooring lines intended to be supplied breaking strength according to the above formula However, the minimum breaking strength should not be taken less than corresponding to an acceptable wind speed of 21 m/s (68.9ft/s): If lines are intended to be supplied for an acceptable wind speed v w * higher than v w as per 3-5-1/19.3.2, the minimum breaking strength should be taken as: w v MBL* = v w 2 MBL (b) Number of Mooring Lines. The total number of head, stern, and breast lines (see Note in 3-5-1/19.3.2) should be taken as: n = A for A 1 in m 2 n = A for A 1 in ft 2 For oil tankers, chemical tankers, bulk carriers, and ore carriers the total number of head, stern, and breast lines should be taken as: n = A for A 1 in m 2 n = A for A 1 in ft 2 The total number of head, stern, and breast lines should be rounded to the nearest whole number. The number of head, stern, and breast lines may be increased or decreased in conjunction with an adjustment to the strength of the lines. The adjusted strength, MBL*, should be taken as: where MBL* = 1.2 MBL n/n* MBL MBL* = MBL n/n* for increased number of lines for reduced number of lines n* = increased or decreased total number of head, stern and breast lines n = number of lines for the considered vessel type as calculated by the above formulas without rounding. Similarly, the strength of head, stern, and breast lines may be increased or decreased in conjunction with an adjustment to the number of lines. The total number of spring lines (see Note in 3-5-1/19.3.2) is not to be taken as less than: Two lines, where EN < 5000 Four lines, where EN 5000 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

16 The strength of spring lines is to be the same as that of the head, stern, and breast lines. If the number of head, stern, and breast lines is increased in conjunction with an adjustment to the strength of the lines, the number of spring lines is to be likewise increased, but rounded up to the nearest even number Length of Mooring Lines The length of mooring lines for vessels with EN of less than or equal to 2000 may be taken from 3-5-1/Table 2. For vessels with EN > 2000 the length of mooring lines may be taken as 200 m (109 fathoms). The lengths of individual mooring lines may be reduced by up to 7% of the above given lengths, but the total length of mooring lines should not be less than would have resulted had all lines been of equal length Tow Line The tow lines are given in 3-5-1/Table 3 and are intended as a vessel s own tow line of a vessel being towed by a tug or other vessel. For the selection of the tow line from 3-5-1/Table 3, the Equipment Number (EN) is to be taken according to 3-5-1/ Mooring and Tow Line Construction Tow lines and mooring lines may be of wire, natural fiber, or synthetic fiber construction or of a mixture of wire and fiber. For synthetic fiber ropes it is recommended to use lines with reduced risk of recoil (snapback) to mitigate the risk of injuries or fatalities in the case of breaking mooring lines. Notwithstanding the requirements given in 3-5-1/19.3 and 3-5-1/19.5, no fiber rope is to be less than 20 mm (0.79 in) in diameter. For polyamide ropes, the minimum breaking strength is to be increased by 20% and for other synthetic ropes by 10% to account for strength loss due to, among others, aging and wear Mooring Winches Each winch is to be fitted with brakes with a holding capacity sufficient to prevent unreeling of the mooring line when the rope tension is equal to 80% of the minimum breaking strength of the rope as fitted on the first layer. The winch is to be fitted with brakes that will allow for the reliable setting of the brake rendering load For powered winches the maximum hauling tension which can be applied to the mooring line (the reeled first layer) is not be less than 1/4.5 times, nor be more than 1 / 3 times the rope's minimum breaking strength. For automatic winches, these figures apply when the winch is set to the maximum power with automatic control. For powered winches on automatic control, the rendering tension that the winch can exert on the mooring line (the reeled first layer) is not to exceed 1.5 times, nor be less than 1.05 times the hauling tension for that particular power setting of the winch. The winch is to be marked with the range of rope strength for which it is designed Mooring and Towing Arrangement Mooring Arrangement Mooring lines in the same service (e.g. breast lines, see Note in 3-5-1/19.3.2) should be of the same characteristic in terms of strength and elasticity. As far as possible, a sufficient number of mooring winches are to be fitted to allow for all mooring lines to be belayed on winches. This allows for an efficient distribution of the load to all mooring lines in the same service and for the mooring lines to shed load before they break. If the mooring arrangement is designed such that mooring lines are partly to be belayed on bitts or bollards, these lines are considered to be not as effective as the mooring lines belayed on winches. 16 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

17 Mooring lines are to have a lead as straight as is practicable from the mooring drum to the fairlead. At points of change in direction, sufficiently large radii of the contact surface of a rope on a fitting are to be provided to minimize the wear experienced by mooring lines and as recommended by the rope manufacturer for the rope type intended to be used Towing Arrangement Towing lines, in general, should be led through a closed chock. The use of open fairleads with rollers or closed roller fairleads is to be avoided. For towing purposes, at least one chock is to be provided close to centerline of the vessel forward and aft. It is also beneficial to provide additional chocks on port and starboard side at the transom and at the bow. Towing lines are to have a straight lead from the towing bitt or bollard to the chock. For the purpose of towing, bitts or bollards serving a chock are to be located slightly offset and, as far as practicable, a distance of at least 2 m (6.6 ft) away from the chock, see figure below: 2 m (6.6 ft) Towing Bitt Offset Towing Chock As far as practicable, warping drums are to be positioned not more than 20 m (65.6 ft) away from the chock, measured along the path of the line. Attention is to be given to the arrangement of the equipment for towing and mooring operations in order to prevent interference of mooring and towing lines as far as practicable. It is beneficial to provide dedicated towing arrangements separate from the mooring equipment. For all vessels it is recommended to provide towing arrangements fore and aft of sufficient strength for other towing service as defined in 3-2-7/5. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

18 SI, MKS Units (Revise 3-5-1/Table 1, as follows:) TABLE 1 Equipment for Self-propelled Ocean-going Vessels (1 July 2018) The weight per anchor of bower anchors given in 3-5-1/Table 1 is for anchors of equal weight. The weight of individual anchors may vary 7% plus or minus from the tabular weight provided that the combined weight of all anchors is not less than that required for anchors of equal weight. The total length of chain required to be carried on board, as given in 3-5-1/Table 1, is to be reasonably divided between the two bower anchors. Equipment Numeral Stockless Bower Anchors Mass per Anchor, kg Normal- Strength Steel (Grade 1), mm Chain Cable Stud Link Bower Chain Diameter High-Strength Steel (Grade 2), mm Extra High- Strength Steel (Grade 3), mm Equipment Number* Number Length, m UA UA UA UA UA UA UA UA UA UA UA UA U U U U U U U U U U U U U U U U U U U U U U U U U ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

19 SI, MKS Units Equipment Numeral TABLE 1 (continued) Equipment for Self-propelled Ocean-going Vessels (1 July 2018) Stockless Bower Anchors Mass per Anchor, kg Normal- Strength Steel (Grade 1), mm Chain Cable Stud Link Bower Chain Diameter High-Strength Steel (Grade 2), mm Extra High- Strength Steel (Grade 3), mm Equipment Number* Number Length, m U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U ** For intermediate values of equipment number use equipment complement in sizes and weights given for the lower equipment number in the table. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

20 US Units TABLE 1 Equipment for Self-propelled Ocean-going Vessels (1 July 2018) The weight per anchor of bower anchors given in 3-5-1/Table 1 is for anchors of equal weight. The weight of individual anchors may vary 7% plus or minus from the tabular weight provided that the combined weight of all anchors is not less than that required for anchors of equal weight. The total length of chain required to be carried on board, as given in 3-5-1/Table 1, is to be reasonably divided between the two bower anchors. Equipment Numeral Stockless Bower Anchors Mass per Anchor, pounds Normal-Strength Steel (Grade 1), inches Chain Cable Stud Link Bower Chain Diameter High-Strength Steel (Grade 2), inches Extra High- Strength Steel (Grade 3), inches Equipment Number* Number Length, fathoms UA / 2 UA / 2 UA / 2 UA ½ UA / 16 1/ 2 UA / 16 1/ 2 UA / 8 9/ 16 UA / 8 9/ 16 UA / 16 5/ 8 UA / 16 5/ 8 UA / 4 11/ 16 UA / 16 11/ 16 U / 8 3/ 4 U / 16 13/ 16 U / 8 13/ 16 U / 8 15/ 16 7/ 8 U / / 16 U / / 8 15/ 16 U / / 16 1 U / / / 8 U / / / 16 U / / / 16 U / / / 4 U / / / 16 U / / / 16 U / / / 16 U / / 2 U / / / 16 U / / / 8 U / / / 4 U / / 16 U / / / 16 U / / / 8 U / / 16 2 U / / 16 2 U / / / 16 U / / / 8 20 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

21 US Units TABLE 1 (continued) Equipment for Self-propelled Ocean-going Vessels (1 July 2018) Stockless Bower Anchors Chain Cable Stud Link Bower Chain Diameter Equipment Numeral Equipment Number* Number Mass per Anchor, pounds Length, fathoms Normal-Strength Steel (Grade 1), inches High-Strength Steel (Grade 2), inches U / / / 16 U / / 16 U / / / 8 U / / / 16 U / / / 2 Extra High- Strength Steel (Grade 3), inches U / / 8 U / / / 16 U / / / 4 U / / / 8 U / / 16 3 U / / / 16 U / / 16 U / / / 16 U / / / 16 U / / / 16 U / / / 16 U / / 16 U / / / 8 U / / / 4 U / / / 8 U / / 8 U / / / 16 U / / 8 4 U / / 4 U / / 8 U / 2 U / / 8 U / / 4 U / 8 5 U / / 8 U / 8 U / 8 U / 8 U / 4 U U / 8 U / 8 ** For intermediate values of equipment number use equipment complement in sizes and weights given for the lower equipment number in the table. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

22 (Delete existing 3-5-1/Table 2 and add new 3-5-1/Tables 2 and 3, as follows:) TABLE 2 Mooring Lines for Self-propelled Ocean-going Vessels with EN 2000 (1 July 2018) Equipment Number Exceeding Not Exceeding Number Minimum Length of Each Line * Mooring Lines Minimum Breaking Strength (m) (fathoms) (kn) (kgf) (lbf) * 3-5-1/ is to be observed. 22 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

23 TABLE 3 Tow Lines for Self-propelled Ocean-going Vessels (1 July 2018) Equipment Number Tow Line Exceeding Not Exceeding Minimum Length Minimum Breaking Strength (m) (ft) (kn) (kgf) (lbf) ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

24 PART 4 CHAPTER 1 SECTION 1 VESSEL SYSTEMS AND MACHINERY GENERAL CLASSIFICATION OF MACHINERY 7 Miscellaneous Requirements for Machinery 7.5 Astern Propulsion Power (2005) (Revise Subparagraph 4-1-1/7.5.1, as follows:) General (1 July 2018) Sufficient power for going astern is to be provided to secure proper control of the vessel in all normal circumstances. The astern power of the main propelling machinery is to be capable of maintaining in free route astern at least 70% of the ahead rpm corresponding to the maximum continuous ahead power. For main propulsion systems with reversing gears, controllable pitch propellers or electric propulsion drive, running astern is not to lead to overload of the propulsion machinery. Main propulsion systems are to undergo tests to demonstrate the astern response characteristics. The tests are to be carried out at least over the maneuvering range of the propulsion system and from all control positions. A test plan is to be provided by the yard and accepted by the surveyor. If specific operational characteristics have been defined by the manufacturer these shall be included in the test plan. The ability of the machinery, including the blade pitch control system of controllable pitch propellers, to reverse the direction of thrust of the propeller in sufficient time, and so to bring the vessel to rest within a reasonable distance from maximum ahead service speed, is to be demonstrated and recorded during trials. PART 4 CHAPTER 2 SECTION 1 VESSEL SYSTEMS AND MACHINERY PRIME MOVERS DIESEL ENGINES 1 General (Revise Paragraph 4-2-1/1.1, as follows:) 1.1 Application (1 July 2018) Diesel engines having a rated power of 100 kw (135 hp) and over, intended for propulsion and for auxiliary services essential for propulsion, maneuvering and safety (see 4-1-1/1.3) of the vessel, are to be designed, constructed, tested, certified and installed in accordance with the requirements of this section. Diesel engines having a rated power of less than 100 kw (135 hp) are not required to comply with the provisions of this Section but are to be designed, constructed and equipped in accordance with good commercial and marine practice. Acceptance of such engines will be based on manufacturer s affidavit, verification of engine nameplate data, and subject to a satisfactory performance test after installation conducted in the presence of the Surveyor. Diesel engines having a rated power of 100 kw (135 hp) and over, intended for services considered not essential for propulsion, maneuvering and safety, are not required to be designed, constructed and certified by ABS in accordance with the requirements of this section. They are to comply with safety features, such as crankcase explosion relief valve, overspeed protection, etc., as provided in 4-2-1/7, as applicable. After installation, they are subject to a satisfactory performance test conducted in the presence of the Surveyor. 24 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

25 Piping systems serving diesel engines, such as fuel oil, lubricating oil, cooling water, starting air, crankcase ventilation and exhaust gas systems are addressed in Section 4-6-5; hydraulic and pneumatic systems are addressed in Section Requirements for turbochargers are provided in Section Additional requirements for dual fuel and gas internal combustion engines are provided in Sections 5C-8-16 and 5C of the Steel Vessel Rules. Additional requirements for exhaust emission abatement equipment connected to internal combustion engines or boilers are provided in the ABS Guide for Exhaust Emission Abatement. 1.9 Plans and Particulars to be Submitted (Revise Subparagraph 4-2-1/1.9.4, as follows:) Materials (1 July 2018) Crankshaft material: Material designation Mechanical properties of material (tensile strength, yield strength, elongation (with length of specimen), reduction of area, impact energy) Type of forging (open die forged (free form), continuous grain flow forged, close die forged (drop-forged), etc., with description of the forging process) Crankshaft heat treatment Crankshaft surface treatment Surface treatment of fillets, journals and pins (induction hardened, flame hardened, nitrided, rolled, shot peened, etc., with full details concerning hardening). For calculation of surface treated fillets and oil bore outlets see Appendix 4-2-1A9. Hardness at surface Hardness as a function of depth, mm (in.) Extension of surface hardening Material specifications of other main parts 5 Design 5.9 Crankshafts Evaluation of Stress Concentration Factors (Revise Item 4-2-1/5.9.4(a), as follows:) 5.9.4(a) General (1 July 2018). The stress concentration factors are evaluated by means of the equations in 4-2-1/5.9.4(b), 4-2-1/5.9.4(c) and 4-2-1/5.9.4(d) applicable to the fillets and crankpin oil bore of solid forged web-type crankshafts and to the crankpin fillets of semi-built crankshafts only. The stress concentration factor equations concerning the oil bore are only applicable to a radially drilled oil hole. Where the geometry of the crankshaft is outside the boundaries of the analytical stress concentration factors (SCF) the calculation method detailed in Appendix 4-2-1A7 may be undertaken. All crank dimensions necessary for the calculation of stress concentration factors are shown in 4-2-1/Figure 5. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

26 The stress concentration factors for bending (α B, β B ) are defined as the ratio of the maximum equivalent stress (Von Mises) occurring in the fillets under bending load to the nominal bending stress related to the web cross-section (see Appendix 4-2-1A2). The stress concentration factor for compression (β Q ) in the journal fillet is defined as the ratio of the maximum equivalent stress (Von Mises), occurring in the fillet due to the radial force, to the nominal compressive stress related to the web cross-section. The stress concentration factors for torsion (α T, β T ) are defined as the ratio of the maximum equivalent shear stress, occurring in the fillets under torsional load, to the nominal torsional stress related to the axially bored crankpin or journal cross-section (see Appendix 4-2-1A3. The stress concentration factors for bending (γ B ) and torsion (γ T ) are defined as the ratio of the maximum principal stress, occurring at the outlet of the crankpin oil-hole under bending and torsional loads, to the corresponding nominal stress related to the axially bored crankpin cross section (see Appendix 4-2-1A3). When reliable measurements and/or calculations are available, which can allow direct assessment of stress concentration factors, the relevant documents and their analysis method is to be submitted in order to demonstrate their equivalence with the Rules. This is always to be performed when dimensions are outside of any of the validity ranges for the empirical formulae presented in 4-2-1/5.9.4(b), 4-2-1/5.9.4(c) and 4-2-1/5.9.4(d). Appendices 4-2-1A7 and 4-2-1A10 describe how FE analyses can be used for the calculation of the stress concentration factors. Care should be taken to avoid mixing equivalent (Von Mises) stresses and principal stresses. (Revise Subparagraph 4-2-1/5.9.7, as follows:) Calculation of Fatigue Strength (1 July 2018) (Preceding text is unchanged.) When a surface treatment process is applied, it must be specially approved. Guidance for calculation of surface treated fillets and oil bore outlets is presented in Appendix 4-2-1A9. These equations are subject to the following conditions: Surfaces of the fillet, the outlet of the oil bore and inside the oil bore (down to a minimum depth equal to 1.5 times the oil bore diameter) shall be smoothly finished. For calculation purposes R H, R G or R X are to be taken as not less than 2 mm. As an alternative, the fatigue strength of the crankshaft can be determined by experiment based either on full size crank throw (or crankshaft) or on specimens taken from a full size crank throw. For evaluation of test results, see Appendix 4-2-1A8. 7 Engine Appurtenances (Revise Paragraph 4-2-1/7.7, as follows:) 7.7 Materials other than Steel on Engine, Turbine and Gearbox Installations (1 July 2018) Materials other than steel may be assessed in relation to the risk of fire associated with the component and its installation. The use of materials other than steel is considered acceptable for the following applications: i) Internal pipes which cannot cause any release of flammable fluid onto the machinery or into the machinery space in case of failure, or 26 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

27 ii) iii) Components that are only subject to liquid spray on the inside when the machinery is running, such as machinery covers, rocker box covers, camshaft end covers, inspection plates and sump tanks. It is a condition that the pressure inside these components and all the elements contained therein is less than 0.18 N/mm 2 and that wet sumps have a volume not exceeding 100 liters (26.4 gallons), or Components attached to machinery which satisfy fire test criteria according to standard ISO 19921:2005/19922:2005 or other standards acceptable to the appropriate administration of the vessel s registry, and which retain mechanical properties adequate for the intended installation Aluminum and aluminum alloys may be considered for use in filters attached to engines where; either the engine installation is fitted with an effective fixed local application fire-extinguishing system in compliance with 4-7-2/1.11.2, or where the engine installation has a power rating not greater than 375 kw (500 hp). See also 4-6-2/ Testing, Inspection and Certification of Diesel Engines 13.9 Shop Tests of Internal Combustion, I.C. Engines (1 July 2016) (Revise Subparagraph 4-2-1/13.9.4, as follows:) Engines Driving Generators for Auxiliary Purposes (1 July 2018) Engines intended for driving vessel service generators and emergency generators, are to be tested as specified in 4-2-1/ After running on the test bed, the fuel delivery system of the engine is to be adjusted so that an overload power of 110% of the rated power can be supplied. Due regard is to be given to service conditions after installation on board and to the governor characteristics including the activation of generator protective devices. See also 4-2-1/7.5.1(b) for governor characteristics associated with power management systems. PART 4 CHAPTER 2 SECTION 1 (Add new Appendix 4-2-1A8, as follows:) VESSEL SYSTEMS AND MACHINERY PRIME MOVERS APPENDIX 8 GUIDANCE FOR EVALUATION OF FATIGUE TESTS (1 July 2018) 1 Introduction Fatigue testing can be divided into two main groups; testing of small specimens and full-size crank throws. Testing can be made using the staircase method or a modified version thereof which is presented in this document. Other statistical evaluation methods may also be applied. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

28 1.1 Small Specimen Testing For crankshafts without any fillet surface treatment, the fatigue strength can be determined by testing small specimens taken from a full-size crank throw. When other areas in the vicinity of the fillets are surface treated introducing residual stresses in the fillets, this approach cannot be applied. One advantage of this approach is the rather high number of specimens which can be then manufactured. Another advantage is that the tests can be made with different stress ratios (R-ratios) and/or different modes (e.g., axial, bending and torsion), with or without a notch. This is required for evaluation of the material data to be used with critical plane criteria. 1.3 Full-size Crank Throw Testing For crankshafts with surface treatment the fatigue strength can only be determined through testing of full size crank throws. For cost reasons, this usually means a low number of crank throws. The load can be applied by hydraulic actuators in a 3- or 4-point bending arrangement, or by an exciter in a resonance test rig. The latter is frequently used, although it usually limits the stress ratio to R = 1. 3 Evaluation of Test Results 3.1 Principles Prior to fatigue testing the crankshaft must be tested as required by quality control procedures (e.g., for chemical composition, mechanical properties, surface hardness, hardness depth and extension, fillet surface finish, etc.). The test samples should be prepared so as to represent the lower end of the acceptance range (e.g., for induction hardened crankshafts this means the lower range of acceptable hardness depth, the shortest extension through a fillet, etc.). Otherwise the mean value test results should be corrected with a confidence interval: a 90% confidence interval may be used both for the sample mean and the standard deviation. The test results, when applied in 4-2-1/5.9, are to be evaluated to represent the mean fatigue strength, with or without taking into consideration the 90% confidence interval as mentioned above. The standard deviation should be considered by taking the 90% confidence into account. Subsequently the result to be used as the fatigue strength is then the mean fatigue strength minus one standard deviation. If the evaluation aims to find a relationship between (static) mechanical properties and the fatigue strength, the relation must be based on the real (measured) mechanical properties, not on the specified minimum properties. The calculation technique presented in 4-2-1A8/11 was developed for the original staircase method. However, since there is no similar method dedicated to the modified staircase method the same is applied for both. 5 Small Specimen Testing In this connection, a small specimen is considered to be one of the specimens taken from a crank throw. Since the specimens shall be representative for the fillet fatigue strength, they should be taken out close to the fillets, as shown in 4-2-1A8/Figure 1. It should be made certain that the principal stress direction in the specimen testing is equivalent to the full-size crank throw. The verification is recommended to be done by utilizing the finite element method. The (static) mechanical properties are to be determined as stipulated by the quality control procedures. 28 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

29 FIGURE 1 Specimen Locations in a Crank Throw (1 July 2018) 5.1 Determination of Bending Fatigue Strength It is advisable to use un-notched specimens in order to avoid uncertainties related to the stress gradient influence. Push-pull testing method (stress ratio R = 1) is preferred, but especially for the purpose of critical plane criteria other stress ratios and methods may be added. In order to ensure principal stress direction in push-pull testing to represent the full-size crank throw principal stress direction and when no further information is available, the specimen shall be taken in 45 degrees angle as shown in 4-2-1A8/Figure 1. i) If the objective of the testing is to document the influence of high cleanliness, test samples taken from positions approximately 120 degrees in a circumferential direction may be used. See 4-2-1A8/Figure 1. ii) If the objective of the testing is to document the influence of continuous grain flow (cgf) forging, the specimens should be restricted to the vicinity of the crank plane. 5.3 Determination of Torsional Fatigue Strength i) If the specimens are subjected to torsional testing, the selection of samples should follow the same guidelines as for bending above. The stress gradient influence has to be considered in the evaluation. ii) If the specimens are tested in push-pull and no further information is available, the samples should be taken out at an angle of 45 degrees to the crank plane in order to ensure collinearity of the principal stress direction between the specimen and the full-size crank throw. When taking the specimen at a distance from the (crank) middle plane of the crankshaft along the fillet, this plane rotates around the pin center point making it possible to resample the fracture direction due to torsion (the results are to be converted into the pertinent torsional values). 5.5 Other Test Positions If the test purpose is to find fatigue properties and the crankshaft is forged in a manner likely to lead to cgf, the specimens may also be taken longitudinally from a prolonged shaft piece where specimens for mechanical testing are usually taken. The condition is that this prolonged shaft piece is heat treated as a part of the crankshaft and that the size is so as to result in a similar quenching rate as the crank throw. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

30 When using test results from a prolonged shaft piece, it must be considered how well the grain flow in that shaft piece is representative for the crank fillets. 5.7 Correlation of Test Results The fatigue strength achieved by specimen testing shall be converted to correspond to the full-size crankshaft fatigue strength with an appropriate method (size effect). When using the bending fatigue properties from tests mentioned in this section, it should be kept in mind that successful continuous grain flow (cgf) forging leading to elevated values compared to other (non cgf) forging, will normally not lead to a torsional fatigue strength improvement of the same magnitude. In such cases it is advised to either carry out also torsional testing or to make a conservative assessment of the torsional fatigue strength (e.g., by using no credit for cgf). This approach is applicable when using the Gough Pollard criterion. However, this approach is not recognized when using the von Mises or a multiaxial criterion such as Findley. If the found ratio between bending and torsion fatigue differs significantly from 3, one should consider replacing the use of the von Mises criterion with the Gough Pollard criterion. Also, if critical plane criteria are used, it must be kept in mind that cgf makes the material inhomogeneous in terms of fatigue strength, meaning that the material parameters differ with the directions of the planes. Any addition of influence factors must be made with caution. If for example a certain addition for clean steel is documented, it may not necessarily be fully combined with a K-factor for cgf. Direct testing of samples from a clean and cgf forged crank is preferred. 7 Full Size Testing 7.1 Hydraulic Pulsation A hydraulic test rig can be arranged for testing a crankshaft in 3-point or 4-point bending as well as in torsion. This allows for testing with any R-ratio. Although the applied load should be verified by strain gauge measurements on plain shaft sections for the initiation of the test, it is not necessarily used during the test for controlling load. It is also pertinent to check fillet stresses with strain gauge chains. Furthermore, it is important that the test rig provides boundary conditions as defined in 4-2-1A7/5.1 to 4-2-1A7/5.5. The (static) mechanical properties are to be determined as stipulated by the quality control procedures. 7.3 Resonance Tester A rig for bending fatigue normally works with an R-ratio of 1. Due to operation close to resonance, the energy consumption is moderate. Moreover, the frequency is usually relatively high, meaning that 107 cycles can be reached within some days A8/Figure 2 shows a layout of the testing arrangement. The applied load should be verified by strain gauge measurements on plain shaft sections. It is also pertinent to check fillet stresses with strain gauge chains. 30 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

31 FIGURE 2 An Example of Testing Arrangement of the Resonance Tester for Bending Loading (1 July 2018) Clamping around the journals must be arranged in a way that prevents severe fretting which could lead to a failure under the edges of the clamps. If some distance between the clamps and the journal fillets is provided, the loading is consistent with 4-point bending and thus representative for the journal fillets also. In an engine, the crankpin fillets normally operate with an R-ratio slightly above 1 and the journal fillets slightly below 1. If found necessary, it is possible to introduce a mean load (deviate from R = 1) by means of a spring preload. A rig for torsion fatigue can also be arranged as shown in 4-2-1A8/Figure 3. When a crank throw is subjected to torsion, the twist of the crankpin makes the journals move sideways. If one single crank throw is tested in a torsion resonance test rig, the journals with their clamped-on weights will vibrate heavily sideways. This sideway movement of the clamped-on weights can be reduced by having two crank throws, especially if the cranks are almost in the same direction. However, the journal in the middle will move more. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

32 FIGURE 3 An Example of Testing Arrangement of the Resonance Tester for Torsion Loading with Double Crank Throw Section (1 July 2018) Since sideway movements can cause some bending stresses, the plain portions of the crankpins should also be provided with strain gauges arranged to measure any possible bending that could have an influence on the test results. Similarly, to the bending case the applied load shall be verified by strain gauge measurements on plain shaft sections. It is also pertinent to check fillet stresses with strain gauge chains as well. 7.5 Use of Results and Crankshaft Acceptability In order to combine tested bending and torsion fatigue strength results in calculation of crankshaft acceptability, see 4-2-1/5.9.8, the Gough-Pollard approach can be applied for the following cases: Related to the crankpin diameter: Q = 32 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

33 where σ DWCT = fatigue strength by bending testing τ DWCT = fatigue strength by torsion testing Related to crankpin oil bore: where Q = σ DWOT = σ σ BO DWOT 2 τ + τ TO DWOT 2 1 fatigue strength by bending testing τ DWOT = fatigue strength by torsion testing Related to the journal diameter: where Q = σ σ BG DWJT 2 τ + τ G DWJT 2 1 σ DWJT = fatigue strength by bending testing τ DWJT = fatigue strength by torsion testing In case increase in fatigue strength due to the surface treatment is considered to be similar between the above cases, it is sufficient to test only the most critical location according to the calculation where the surface treatment had not been taken into account. 9 Use of Existing Results for Similar Crankshafts For fillets or oil bores without surface treatment, the fatigue properties found by testing may be used for similar crankshaft designs providing: i) Material: ii) iii) Similar material type Cleanliness on the same or better level The same mechanical properties can be granted (size versus hardenability) Geometry: Difference in the size effect of stress gradient is insignificant or it is considered Principal stress direction is equivalent. See 4-2-1A8/5. Manufacturing: Similar manufacturing process Induction hardened or gas nitrited crankshafts will suffer fatigue either at the surface or at the transition to the core. The surface fatigue strength as determined by fatigue tests of full size cranks, may be used on an equal or similar design as the tested crankshaft when the fatigue initiation occurred at the surface. With the similar design, it is meant that a similar material type and surface hardness are used and the fillet radius and hardening depth are within approximately ± 30 % of the tested crankshaft. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

34 Fatigue initiation in the transition zone can be either subsurface, i.e. below the hard layer, or at the surface where the hardening ends. The fatigue strength at the transition to the core can be determined by fatigue tests as described above, provided that the fatigue initiation occurred at the transition to the core. Tests made with the core material only will not be representative since the tension residual stresses at the transition are lacking. Some recent research has shown that the fatigue limit can decrease in the very high cycle domain with subsurface crack initiation due to trapped hydrogen that accumulates through diffusion around some internal defect functioning as an initiation point. In these cases, it would be appropriate to reduce the fatigue limit by some percent per decade of cycles beyond 107. Based on the publication Metal Fatigue: Effects of Small Defects and Non-metallic Inclusions the reduction is suggested to be 5% per decade especially when the hydrogen content is considered to be high. 11 Calculation Technique 11.1 Staircase Method In the original staircase method, the first specimen is subjected to a stress corresponding to the expected average fatigue strength. If the specimen survives 107 cycles, it is discarded and the next specimen is subjected to a stress that is one increment above the previous (i.e., a survivor is always followed by the next using a stress one increment above the previous). The increment should be selected to correspond to the expected level of the standard deviation. When a specimen fails prior to reaching 107 cycles, the obtained number of cycles is noted and the next specimen is subjected to a stress that is one increment below the previous. With this approach, the sum of failures and run-outs is equal to the number of specimens. This original staircase method is only suitable when a high number of specimens are available. Through simulations it has been found that the use of about 25 specimens in a staircase test leads to a sufficient accuracy in the result Modified Staircase Method When a limited number of specimens are available, it is advisable to apply the modified staircase method. Here the first specimen is subjected to a stress level that is most likely well below the average fatigue strength. When this specimen has survived 107 cycles, this same specimen is subjected to a stress level one increment above the previous. The increment should be selected to correspond to the expected level of the standard deviation. This is continued with the same specimen until failure. Then the number of cycles is recorded and the next specimen is subjected to a stress that is at least 2 increments below the level where the previous specimen failed. With this approach, the number of failures usually equals the number of specimens. The number of run-outs, counted as the highest level where 107 cycles were reached, also equals the number of specimens. The acquired result of a modified staircase method should be used with care, since some results available indicate that testing a runout on a higher test level, especially at high mean stresses, tends to increase the fatigue limit. However, this training effect is less pronounced for high strength steels (e.g., UTS > 800 MPa). If the confidence calculation is desired or necessary, the minimum number of test specimens is Calculation of Sample Mean and Standard Deviation A hypothetical example of tests for 5 crank throws is presented further in the subsequent text. When using the modified staircase method and the evaluation method of Dixon and Mood, the number of samples will be 10, meaning 5 run-outs and 5 failures, i.e.: Number of samples: n = ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

35 Furthermore, the method distinguishes between: Less frequent event is failures C = 1 Less frequent event is run-outs C = 2 The method uses only the less frequent occurrence in the test results, i.e. if there are more failures than runouts, then the number of run-outs is used, and vice versa. In the modified staircase method, the number of run-outs and failures are usually equal. However, the testing can be unsuccessful (e.g., the number of run-outs can be less than the number of failures if a specimen with 2 increments below the previous failure level goes directly to failure). On the other hand, if this unexpected premature failure occurs after a rather high number of cycles, it is possible to define the level below this as a run-out. Dixon and Mood s approach, derived from the maximum likelihood theory, which also may be applied here, especially on tests with few samples, presented some simple approximate equations for calculating the sample mean and the standard deviation from the outcome of the staircase test. The sample mean can be calculated as follows: S a = S a0 + d when C = 1 A F 1 2 S a = S a0 + d when C = 2 A F The standard deviation can be found by: where F B A s = 1.62 d 2 F S a0 = lowest stress level for the less frequent occurrence d = stress increment F = f i A = i fi B = i 2 fi i = stress level numbering f i = number of samples at stress level i The formula for the standard deviation is an approximation and can be used when: F B A 2 F 2 > 0.3 and 0.5s < d < 1.5s If any of these two conditions are not fulfilled, a new staircase test should be considered or the standard deviation should be taken quite large in order to be on the safe side. If increment d is greatly higher than the standard deviation s, the procedure leads to a lower standard deviation and a slightly higher sample mean, both compared to values calculated ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

36 Respectively, if increment d is much less than the standard deviation s, the procedure leads to a higher standard deviation and a slightly lower sample mean Confidence Interval for Mean Fatigue Limit If the staircase fatigue test is repeated, the sample mean and the standard deviation will most likely be different from the previous test. Therefore, it is necessary to assure with a given confidence that the repeated test values will be above the chosen fatigue limit by using a confidence interval for the sample mean. The confidence interval for the sample mean value with unknown variance is known to be distributed according to the t-distribution (also called student s t-distribution) which is a distribution symmetric around the average. The confidence level normally used for the sample mean is 90%, meaning that 90% of sample means from repeated tests will be above the value calculated with the chosen confidence level A8/Figure 4 shows the t-value for (1 α) 100% confidence interval for the sample mean. FIGURE 4 Student s t-distribution (1 July 2018) If S a is the empirical mean and s is the empirical standard deviation over a series of n samples, in which the variable values are normally distributed with an unknown sample mean and unknown variance, the (1 α) 100% confidence interval for the mean is: P = 1 α The resulting confidence interval is symmetric around the empirical mean of the sample values, and the lower endpoint can be found as: S ax% = which is the mean fatigue limit (population value) to be used to obtain the reduced fatigue limit where the limits for the probability of failure are taken into consideration Confidence Interval for Standard Deviation The confidence interval for the variance of a normal random variable is known to possess a chi-square distribution with n 1 degrees of freedom. The confidence level on the standard deviation is used to ensure that the standard deviations for repeated tests are below an upper limit obtained from the fatigue test standard deviation with a confidence level A8/Figure 5 shows the chi-square for (1 α) 100% confidence interval for the variance. 36 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

37 FIGURE 5 Chi-square Distribution (1 July 2018) An assumed fatigue test value from n samples is a normal random variable with a variance of σ 2 and has an empirical variance s 2. Then a (1 α) 100% confidence interval for the variance is: P = 1 α A (1 α) 100% confidence interval for the standard deviation is obtained by the square root of the upper limit of the confidence interval for the variance and can be found by: S X% = This standard deviation (population value) is to be used to obtain the fatigue limit, where the limits for the probability of failure are taken into consideration. PART 4 CHAPTER 2 SECTION 1 (Add new Appendix 4-2-1A9, as follows:) VESSEL SYSTEMS AND MACHINERY PRIME MOVERS APPENDIX 9 GUIDANCE FOR EVALUATION OF FATIGUE TESTS (1 July 2018) 1 Introduction This Appendix deals with surface treated fillets and oil bore outlets. The various treatments are explained and some empirical formulae are given for calculation purposes. Conservative empiricism has been applied intentionally, in order to be on the safe side from a calculation standpoint. Measurements should be used if available. In the case of a wide scatter (e.g., for residual stresses) the values should be chosen from the end of the range that would be on the safe side for calculation purposes. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

38 3 Surface Treatment Surface treatment is a term covering treatments such as thermal, chemical or mechanical operations, leading to inhomogeneous material properties such as hardness, chemistry or residual stresses from the surface to the core. 3.1 Surface Treatment Methods The following list covers possible treatment methods and how they influence the properties that are decisive for the fatigue strength. Surface Treatment Methods and the Characteristics They Affect Treatment Method Induction hardening Nitriding Case hardening Die quenching (no temper) Cold rolling Stroke peening Shot peening Laser peening Ball coining Affecting Hardness and residual stresses Chemistry, hardness and residual stresses Chemistry, hardness and residual stresses Hardness and residual stresses Residual stresses Residual stresses Residual stresses Residual stresses Residual stresses It is important to note that since only induction hardening, nitriding, cold rolling and stroke peening are considered relevant for marine engines, other methods as well as combination of two or more of the above are not dealt with in this document. In addition, die quenching can be considered in the same way as induction hardening. 5 Calculation Principles The basic principle is that the alternating working stresses shall be below the local fatigue strength (including the effect of surface treatment) wherein non-propagating cracks may occur, see also 4-2-1A9/11.1 for details. This is then divided by a certain safety factor. This applies through the entire fillet or oil bore contour as well as below the surface to a depth below the treatment-affected zone (i.e., to cover the depth all the way to the core). Consideration of the local fatigue strength shall include the influence of the local hardness, residual stress and mean working stress. The influence of the giga-cycle effect, especially for initiation of subsurface cracks, should be covered by the choice of safety margin. It is of vital importance that the extension of hardening/peening in an area with concentrated stresses be duly considered. Any transition where the hardening/peening is ended is likely to have considerable tensile residual stresses. This forms a weak spot and is important if it coincides with an area of high stresses. Alternating and mean working stresses must be known for the entire area of the stress concentration as well as to a depth of about 1.2 times the depth of the treatment A9/Figure 1 indicates this principle in the case of induction hardening. The base axis is either the depth (perpendicular to the surface) or along the fillet contour. 38 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

39 FIGURE 1 Stresses as Functions of Depth, General Principles (1 July 2018) The acceptability criterion should be applied stepwise from the surface to the core as well as from the point of maximum stress concentration along the fillet surface contour to the web. 5.1 Evaluation of Local Fillet Stresses It is necessary to have knowledge of the stresses along the fillet contour as well as in the subsurface to a depth somewhat beyond the hardened layer. Normally, this will be found via FEA as described in Appendix 4-2-1A7. However, the element size in the subsurface range will have to be the same size as at the surface. For crankpin hardening only the small element size will have to be continued along the surface to the hard layer. If no FEA is available, a simplified approach may be used. This can be based on the empirically determined stress concentration factors (SCFs), as in 4-2-1/5.9.4 if within its validity range, and a relative stress gradient inversely proportional to the fillet radius. Bending and torsional stresses must be addressed separately. The combination of these is addressed by the acceptability criterion. The subsurface transition-zone stresses, with the minimum hardening depth, can be determined by means of local stress concentration factors along an axis perpendicular to the fillet surface. These functions α B-local and α T-local have different shapes due to the different stress gradients. The SCFs α B and α T are valid at the surface. The local α B-local and α T-local drop with increasing depth. The relative stress gradients at the surface depend on the kind of stress raiser, but for crankpin fillets they can be simplified to 2/R H in bending and 1/R H in torsion. The journal fillets are handled analogously by using R G and D G. The nominal stresses are assumed to be linear from the surface to a midpoint in the web between the crankpin fillet and the journal fillet for bending and to the crankpin or journal center for torsion. The local SCFs are then functions of depth t according to the following formula as shown in 4-2-1A9/Figure 2 for bending: α B-local = ( α 1) B 2 t H e R + 1 W 2 t 2 + S α B ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

40 FIGURE 2 Bending SCF in the Crankpin Fillet as a Function of Depth (1 July 2018) Note: The corresponding SCF for the journal fillet can be found by replacing R H with R G. and respectively for torsion in the following formula and 4-2-1A9/Figure 3: t t e R 2 αt D H T α T-local = ( ) 1 α FIGURE 3 Torsional SCF in the Crankpin Fillet as a Function of Depth (1 July 2018) Note: The corresponding SCF for the journal fillet can be found by replacing R H with R G and D with D G. 40 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

41 If the pin is hardened only and the end of the hardened zone is closer to the fillet than three times the maximum hardness depth, FEA should be used to determine the actual stresses in the transition zone. 5.3 Evaluation of Oil Bore Stresses Stresses in the oil bores can be determined also by FEA. The element size should be less than 1 / 8 of the oil bore diameter D o and the element mesh quality criteria should be followed as prescribed in Appendix 4-2-1A7. The fine element mesh should continue well beyond a radial depth corresponding to the hardening depth. The loads to be applied in the FEA are the torque see Appendix 4-2-1A7/5.1 and the bending moment, with four-point bending as in Appendix 4-2-1A7/5.3. If no FEA is available, a simplified approach may be used. This can be based on the empirically determined SCF from 4-2-1/5.9.4 if within its applicability range. Bending and torsional stresses at the point of peak stresses are combined as in 4-2-1/ FIGURE 4 Stresses and Hardness in Induction Hardened Oil Holes (1 July 2018) 4-2-1A9/Figure 4 indicates a local drop of the hardness in the transition zone between a hard and soft material. Whether this drop occurs depends also on the tempering temperature after quenching in the QT process. The peak stress in the bore occurs at the end of the edge rounding. Within this zone the stress drops almost linearly to the center of the pin. As can be seen from 4-2-1A9/Figure 4, for shallow (A) and intermediate (B) hardening, the transition point practically coincides with the point of maximal stresses. For deep hardening the transition point comes outside of the point of peak stress and the local stress can be assessed as a portion (1 2t H /D) of the peak stresses where t H is the hardening depth. ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

42 The subsurface transition-zone stresses (using the minimum hardening depth) can be determined by means of local stress concentration factors along an axis perpendicular to the oil bore surface. These functions γ B-local and γ T-local have different shapes, because of the different stress gradients. The stress concentration factors γ B and γ T are valid at the surface. The local SCFs γ B-local and γ T-local drop with increasing depth. The relative stress gradients at the surface depend on the kind of stress raiser, but for crankpin oil bores they can be simplified to 4/D o in bending and 2/D o in torsion. The local SCFs are then functions of the depth t: γ B-local = γ T-local = 5.5 Acceptability Criteria Acceptance of crankshafts is based on fatigue considerations; 4-2-1/5.9.8 compares the equivalent alternating stress and the fatigue strength ratio to an acceptability factor of Q 1.15 for oil bore outlets, crankpin fillets and journal fillets. This shall be extended to cover also surface treated areas independent of whether surface or transition zone is examined. 7 Induction Hardening Generally, the hardness specification shall specify the surface hardness range (i.e., minimum and maximum values), the minimum and maximum extension in or through the fillet and also the minimum and maximum depth along the fillet contour. The referenced Vickers hardness is considered to be HV0.5 ~ HV5. The induction hardening depth is defined as the depth where the hardness is 80% of the minimum specified surface hardness. FIGURE 5 Typical Hardness as a Function of Depth (1 July 2018) Note: The arrows indicate the defined hardening depth. Note the indicated potential hardness drop at the transition to the core. This can be a weak point as local strength may be reduced and tensile residual stresses may occur. In the case of crankpin or journal hardening only, the minimum distance to the fillet shall be specified due to the tensile stress at the heat-affected zone as shown in 4-2-1A9/Figure ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018

43 FIGURE 6 Residual Stresses along the Surface of a Pin and Fillet (1 July 2018) If the hardness-versus-depth profile and residual stresses are not known or specified, one may assume the following: i) The hardness profile consists of two layers (see 4-2-1A9/Figure 5): Constant hardness from the surface to the transition zone Constant hardness from the transition zone to the core material ii) Residual stresses in the hard zone of 200 MPa (compression) iii) Transition-zone hardness as 90% of the core hardness unless the local hardness drop is avoided iv) Transition-zone maximum residual stresses (von Mises) of 300 MPa tension If the crankpin or journal hardening ends close to the fillet, the influence of tensile residual stresses has to be considered. If the minimum distance between the end of the hardening and the beginning of the fillet is more than 3 times the maximum hardening depth, the influence may be disregarded. 7.1 Local Fatigue Strength Induction-hardened crankshafts will suffer fatigue either at the surface or at the transition to the core. The fatigue strengths, for both the surface and the transition zone, can be determined by fatigue testing of full size cranks as described in Appendix 4-2-1A8. In the case of a transition zone, the initiation of the fatigue can be either subsurface (i.e. below the hard layer) or at the surface where the hardening ends. Tests made with the core material only will not be representative since the tensile residual stresses at the transition are lacking. Alternatively, the surface fatigue strength can be determined empirically as follows where HV is the surface Vickers hardness. The following formula provides a conservative value, with which the fatigue strength is assumed to include the influence of the residual stress. The resulting value is valid for a working stress ratio of R = 1: σ Fsurface = (HV 400) MPa ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS

44 It has to be noted also that the mean stress influence of induction-hardened steels may be significantly higher than that for QT steels. The fatigue strength in the transition zone, without taking into account any possible local hardness drop, shall be determined by the equation introduced in 4-2-1/ For journal and respectively to crankpin fillet applies: where σ Ftransition,cpin = ± K (0.42 σ B ) Y Y = D G for journal fillet σ σ B 1 B X = D for crankpin fillet = D for oil bore outlet X = R G for journal fillet = R H for crankpin fillet = D o /2 for oil bore outlet The influence of the residual stress is not included in the above formula. For the purpose of considering subsurface fatigue, below the hard layer, the disadvantage of tensile residual stresses has to be considered by subtracting 20% from the value determined above. This 20% is based on the mean stress influence of alloyed quenched and tempered steel having a residual tensile stress of 300 MPa. When the residual stresses are known to be lower, also smaller value of subtraction shall be used. For lowstrength steels the percentage chosen should be higher. For the purpose of considering surface fatigue near the end of the hardened zone (i.e., in the heat-affected zone shown in 4-2-1A9/Figure 6), the influence of the tensile residual stresses can be considered by subtracting a certain percentage, in accordance with 4-2-1A9/Table 1, from the value determined by the above formula. TABLE 1 The Influence of Tensile Residual Stresses at a Given Distance from the End of the Hardening Towards the Fillet (1 July 2018) I. 0 to 1.0 of the max. hardening depth: 20% II. 1.0 to 2.0 of the max. hardening depth: 12% III. 2.0 to 3.0 of the max. hardening depth: 6% IV. 3.0 or more of the max. hardening depth: 0% 9 Nitriding The hardness specification shall include the surface hardness range (min and max) and the minimum and maximum depth. Only gas nitriding is considered. The referenced Vickers hardness is considered to be HV0.5. The depth of the hardening is defined in different ways in the various standards and the literature. The most practical method to use in this context is to define the nitriding depth t N as the depth to a hardness of 50 HV above the core hardness. The hardening profile should be specified all the way to the core. If this is not known, it may be determined empirically via the following formula: 44 ABS GUIDE FOR BUILDING AND CLASSING INTERNATIONAL NAVAL SHIPS. 2018