Guidelines on Corrosion Resistant Steel for COT December 2010 Nippon Kaiji Kyokai
- Attention is drawn to the possibility that some portions of these Guidelines may unintentionally conflict with certain patent rights, application for a patent that has been made public, utility model rights or applications for utility model registration that have been made public which have technical properties. - ClassNK shall bear no responsibility whatsoever for identifying such patent rights, application for any patent that have been made public, utility model rights or applications for utility model registration that have been made public. Copyright 2010 ClassNK All rights reserved
Introduction With unprecedented growth in the transportation of oil by sea, pollution of the marine environment from oil spills and other disasters have become international issues of ever increasing concern. As a result, various kinds of ship construction rules and survey rules have been enhanced, such as requirements for double hull tankers and enhanced survey programs. Global standardization related to preventing corrosion in ship structures, including more stringent coating standards for ballast tanks, has progressed, and corrosion prevention standards for cargo oil tanks of crude oil tankers (hereafter referred to as COT ) are now being debated. In Japan, the SR242 Research Committee was established at the Shipbuilding Research Association of Japan in 1999, and wide-ranging studies were conducted for a period of three years on corrosion issues of COT. The studies culminated in the clarification of the corrosive environment and corrosion mechanisms in COT. Based on the findings of these studies, major Japanese steel manufacturers started technical development work aimed at reducing corrosion in COT, and developed corrosion resistant steel for COT possessing excellent corrosion resistant performance characteristics to resist the corrosive environment of COT. Under these conditions, relevant SOLAS amendments reinforcing measures for corrosion prevention of COT were adopted at the 87 th session of the Maritime Safety Committee (MSC) held in May 2010. At the same time, the Performance Standard for Protective Coatings for Cargo Oil Tanks of Crude Oil Tankers (IMO resolution MSC.288 (87)) and the Performance Standard for Alternative Means of Corrosion Protection for Cargo Oil Tanks of Crude Oil Tankers (IMO resolution MSC.289 (87)) were adopted. That is to say, performance standards for corrosion resistant steel for use in COT were incorporated as an alternative means of corrosion protection. These guidelines describe in detail the applicable procedures including applicable members and type approval, construction work and inspection procedures during construction, and operational methods after the ship enters service for corrosion resistant steel for COT prescribed in the Performance Standard for Alternative Means of Corrosion Protection for Cargo Oil Tanks of Crude Oil Tankers (IMO resolution MSC.289 (87)). The Society hope that these guidelines will promote the application of corrosion resistant steel for COT and contribute to greater safety at sea and the prevention of pollution of the sea.
Guidelines on Corrosion Resistant Steel for COT Table of Contents Chapter 1 Scope of the Guidelines 1 1.1 Application 1 Chapter 2 Conventions Related to Corrosion Protection of COT 2 2.1 Conventions 2 2.2 Applicable ships 2 Chapter 3 Explanation of Terms 3 3.1 Terminology 3 Chapter 4 Applicable Members 4 4.1 Areas of application of corrosion resistant steel 4 4.2 Combination of corrosion protection methods 5 Chapter 5 Applicable Procedure 7 5.1 Procedure applicable to new ships 7 5.2 Procedure applicable to ships in service 7 Chapter 6 Technical File 9 6.1 Approval of Technical File 9 6.2 Content of Technical File 9 Chapter 7 Requirements for Corrosion Protection of Appurtenances 11 7.1 Permanent means of access provided for inspection not integral to the ship s structure 11 7.2 Access arrangements integral to the ship s structure 12 7.3 Supporting members, etc. 12 7.4 Attachments during work 12 Chapter 8 Type Approval 13 8.1 Approval 13 8.2 Type Approval Certificate 13 Chapter 9 Welding Work 14 9.1 Welding consumables 14 9.2 Approval of welding procedure 14 9.3 Welding work standards 14 -I-
Chapter 10 Surveys 15 10.1 Product inspection 15 10.2 Survey during the construction stage 15 APPENDIX [1-1] Supplement to Corrosion Resistance Test Procedure 16 APPENDIX [1-2] Judgment Criteria for Results of Corrosion Resistance Tests of Welded Joints 19 APPENDIX [1-3] Standard Format for Results of Corrosion Resistance Tests 21 APPENDIX [2] Type Approval Procedure for Corrosion Resistant Steel 23 APPENDIX [3-1] Special Requirements for Product Tests of Corrosion Resistance 32 APPENDIX [3-2] Handling of Alternative to Product Tests of Corrosion Resistance by Controlling Chemical Composition 34 ANNEX PERFORMANCE STANDARD FOR ALTERNATIVE MEANS OF CORROSION PROTECTION FOR CARGO OIL TANKS OF CRUDE OIL TANKERS -II-
Guidelines on Corrosion Resistant Steel for COT Chapter 1 Scope of the Guidelines 1.1 Application These guidelines apply to corrosion resistant steel for COT (hereafter referred to as corrosion resistant steel ) when such steel is used as the corrosion protection method specified in Regulation 3-11, Part A-1, Chapter II-1 of the SOLAS Convention (Corrosion protection of cargo oil tanks of crude oil tankers). -1-
Chapter 2 Conventions Related to Corrosion Protection of COT 2.1 Conventions 2.1.1 SOLAS Convention Regulation 3-11, Part A-1, Chapter II-1 of the SOLAS Convention requires the following: (1) Appropriate corrosion protection measures are to be adopted during construction of the COT that satisfy the requirements of section 2.2 below. (2) Coating is to be applied in accordance with the Performance Standard for Protective Coatings for COT (MSC.288(87)). (3) When corrosion protection methods other than coating are used, the corrosion protection methods are to be in accordance with Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289 (87)). 2.1.2 Performance Standard for Protective Coatings for COT (MSC.288(87)) The official name of the standard adopted by IMO Resolution MSC.288(87) is the Performance Standard for Protective Coatings for Cargo Oil Tanks of Crude Oil Tankers. This standard specifies requirements for performance of coatings for COT, applicable procedures, records to be maintained, and other related details. 2.1.3 Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) The official name of this standard adopted by IMO Resolution MSC.289(87) is the Performance Standard for Alternative Means of Corrosion Protection for Cargo Oil Tanks of Crude Oil Tankers. This standard specifies the minimum requirements when corrosion protection methods of COT other than coating are used. Annex to this standard includes Performance Standard for Corrosion Resistant Steel, which specifies requirements such as performance, application, records to be maintained, etc., for corrosion resistant steel. 2.2 Applicable ships 2.2.1 Corrosion protection measures by coating or by use of corrosion resistant steel, etc. are to be adopted in the cargo oil tanks of crude oil tankers having a deadweight capacity of 5,000 tons or above when any of the conditions (1) to (3) below apply. (1) Ships for which the building contract is placed on or after 1 January 2013; (2) Ships for which keels are laid or at a similar stage of construction on or after 1 July 2013, in the absence of a building contract; or (3) Ships delivered on or after 1 January 2016. 2.2.2 The following ships may be exempted: (1) Combination carriers as defined in Regulation 1, Annex I of MARPOL 73/78 (excluding combination carriers designed for loading only crude oil in the cargo holds); (2) Chemical tankers as defined in Regulation 1, Annex II of MARPOL 73/78 (including chemical tankers approved for carrying oil); and (3) Product carriers not carrying crude oil. -2-
Chapter 3 Explanation of Terms 3.1 Terminology The definitions given below are used in these guidelines. Crude oil tanker means an oil tanker engaged in the trade of carrying crude oil and complying with items 1.11.1 or 1.11.4 of the IOPP Certificate (Form B). Corrosion resistant steel means rolled steel for hull having corrosion resistance. Corrosion resistant steel is to satisfy all the conditions (1) to (3) below in order to comply with these Guidelines. (1) Chemical composition and mechanical properties satisfy the requirements of rolled steel for hull in the Rules for the Survey and Construction of Steel Ships. (2) Elements to be added for improving the corrosion resistance and for which content is not specified in (1) above are to be generally within 1%. (3) Does not initiate problematic galvanic corrosion with conventional steel in the COT environment. Corrosion resistance means the ability to not corrode easily in the COT environment. Conventional steel means conventional rolled steel for hull no giving any special consideration to corrosion resistance. Corrosion Resistant Steel Technical File (hereafter referred to as the Technical File ) means a document stating items related to corrosion resistant steel used during construction and repairs, which is to be stored on board the ship. Type approval means the certification given to manufacturer for complying with the requirements of approved product as specified in the relevant regulations for the relevant corrosion resistant steel after the examinations, tests and inspections stated in the performance standard of corrosion resistant steel and in these Guidelines have been carried out. In this case, approval of manufacturing process of the relevant steel plate is also included. Approval of welding procedure means approval of the work procedure during welding of the steel. Welding work standards means workmanship accuracy standards including welding work left to the discretion of the Society, such as, for instance, the Japan Shipbuilding Quality Standard (JSQS) of the Japan Society of Naval Architects and Ocean Engineers, and the Shipbuilding And Repair Quality Standard (SARQS) of IACS. Design of experiment refers to the test techniques based on statistical techniques, and used for planning the efficient way that a test is conducted in when the analysis object consists of many parameters. -3-
Chapter 4 Applicable Members 4.1 Areas of application of corrosion resistant steel 4.1.1 The areas of application of corrosion resistant steel in COT are as given below (refer to Fig. 4.1). (1) Deckhead with complete internal structures, including brackets connecting to longitudinal and transverse bulkheads. In tanks of a ring frame girder construction, the underdeck transverse framing is to be protected down to level of the first tripping bracket below the upper faceplate. (2) Longitudinal and transverse bulkheads to be protected to the uppermost means of access level. The uppermost means of access and its supporting brackets are to be fully protected. (3) On cargo tank bulkheads without an uppermost means of access, the protection is to extend to 10% of the tank s height at the centerline but need not extend more than 3 m down from the deck. (4) Flat inner bottom and all structures to a height of 0.3 m above the inner bottom are to be protected. Remarks: The areas of application of corrosion resistant steel are the same as the areas of corrosion protection given in the Performance Standard for Protective Coatings for COT (MSC.288(87)). 4.1.2 Structural members in which corrosion resistant steel is not used in those areas noted in paragraph 4.1.1 above are to satisfy the Performance Standard for Protective Coatings for COT (MSC.288(87)). Fig. 4.1 Areas of application of corrosion resistant steel -4-
3m 0.1H (H =Tank height at ship centerline) :Extent of corrosion protection C L C L Fig. 4.2 Areas of application when uppermost means of access has not been provided 4.2 Combination of corrosion protection methods 4.2.1 Members in the COT that require protection measures against corrosion may be divided into types (a) and (b) as follows: (a) Lower surface of strength deck and surrounding structures, and (b) Upper surface of inner bottom plating and surrounding structures. 4.2.2 Different methods of corrosion protection (coating and corrosion resistant steel) may be adopted for (a) and (b) above. Moreover, a combination of different corrosion protection methods may be used for each of the members in (a) and (b). 4.2.3 Acceptable combinations of corrosion protection methods are shown in Table 4.1. Table 4.1 Acceptable combinations of corrosion protection methods for COT Member Lower surface of strength deck (a) Upper surface of inner bottom plating (b) Case 1 Corrosion resistant steel (Brand A) * Corrosion resistant steel (Brand A) * Corrosion protection method Case 2 Coating Corrosion resistant steel (Brand B) * Case 3 Corrosion resistant steel (Brand C) * Coating Case 4 Corrosion resistant steel (Brand D) * Corrosion resistant steel (Brand E) * *:Corrosion resistant steel and coating may be used in the same member. 4.2.4 If different corrosion protection methods (coating and corrosion resistant steel) are selected for either (a) or (b), the selected procedure for each member is to comply with the performance standards and the relevant Guidelines. 4.2.5 The corrosion resistant steel to be used in the above methods is to be type approved by the -5-
Society. 4.2.6 If corrosion resistant steels of a different brand (brand: name of corrosion resistant steel indicated on the Type Approval Certificate) are used in the same member, the welded part and appropriate width from the welded part of the corrosion resistant steels are to be coated. However, the above provision does not apply if corrosion resistance of the different corrosion resistant steels and their welded parts is found to be acceptable, based on appropriate test results and technical data. 4.2.7 The corrosion resistance is found to be acceptable in paragraph 4.2.6 above, means that each combination of welding consumable used in welded joints and different corrosion resistant steels has been tested and the test results of corrosion resistance have been found to be satisfactory. 4.2.8 When corrosion resistant steel and conventional steel are used together in an area where corrosion protection is necessary, conventional steel is to be coated in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)) and the relevant guidelines. Coating is to be extended to the corrosion resistant steel side to an appropriate distance from the welded part. 4.2.9 If welding consumables whose brands are not indicated on the Type Approval Certificate of corrosion resistant steel are used for the welding work of the corrosion resistant steel, the welded part and an appropriate width from the welded part of the corrosion resistant steel are to be coated in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)) and the relevant Guidelines. -6-
5.1 Procedure applicable to new ships Chapter 5 Applicable Procedure 5.1.1 Figure 5.1 shows an overview of the procedure applicable to corrosion resistant steel. The main requirements are as follows: (1) Corrosion resistant steel type approved by the Society is to be used. (2) Welding work is to be implemented according to the approved welding procedure. (3) The correct use of corrosion resistant steel is verified by sampling inspection and block inspection. (4) The shipbuilder is to prepare a Technical File after the construction work has been completed, and submit it to the Society for approval. (5) The approved Technical File is to be maintained onboard the ship. 5.1.2 If any of the items in 5.1.1(1) to 5.1.1(5) above do not comply with Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) and these Guidelines, the Society s surveyor notifies the steel manufacturer and the shipbuilder immediately, and confirm the correction method to be followed and its completion. 5.2 Procedure applicable to ships in service 5.2.1 If the repair method is described in the Technical File, repairs are to be carried out in accordance with the said method. 5.2.2 If corrosion resistant steel or coated member is to be replaced, a corrosion protection method same to the one used during construction is recommended. 5.2.3 If corrosion resistant steel is to be used during repairs, use of the corrosion resistant steel of the same brand as that used during construction is recommended. 5.2.4 If conventional steel is used in a corrosion resistant steel member that is to be replaced, coating is to be applied to the conventional steel. In this case, it is recommended that the coating complies with Performance Standard for Protective Coatings for COT (MSC.288(87)) or the relevant Guidelines. The range of coating is to extend to an appropriate length from the replaced part and welded part. 5.2.5 The application of welding consumables to be used is to be confirmed through the latest Type Approval Certificate of the relevant corrosion resistant steel to ensure conformity (brands of the welding consumables are indicated on the Type Approval Certificate). 5.2.6 If the welding consumables applicable to the corrosion resistant steel cannot be used, the welded part and an appropriate length from the welded part are both to be coated. -7-
NK Shipbuilder Steel manufacturer Shipping company Type Approval of corrosion resistant steel Confirm application documents Witness approval test Application Approval Prepare application Conduct approval test Drawing approval Prepare application drawings Location for using corrosion resistant steel Brand of corrosion resistant steel Welding consumables used Provide technical data Conforms to these Guidelines? No Correct YES Approve Order corrosion resistant steel Manufacture corrosion resistant steel Product test Store test certificate Store test certificate Supply corrosion resistant steel Inspection Use of approved corrosion resistant steel Use of approved work procedures Problem? YES Correct Specify Check Construction work (Work according to validated procedures, such as welding procedures, etc.) Completion of work Examine Submit Prepare Technical File Conforms to these Guidelines? YES No Specify corrections Approve Place onboard the ship Maintain onboard the ship Fig. 5.1 Overview of procedures applicable to use of corrosion resistant steel -8-
Chapter 6 Technical File 6.1 Approval of Technical File The shipbuilder is to prepare and submit to the Society at least three copies of the Technical File (one each for the ship, the Branch Office, and the Head Office) to be provided onboard the ship finally after receiving approval. If the applicable corrosion protection method varies for different members, approval is to be received for the Technical File for corrosion protection method for each member separately. 6.2 Content of Technical File A description of each item to be included in the Technical File is as given below. 6.2.1 Records during construction 6.2.1.1 Copy of Type Approval Certificate The copy of the Type Approval Certificate included in the Technical File is to include a copy of the Particulars of Approval. 6.2.1.2 Technical Data (1) Welding consumables (i) Brand of welding consumables used (including welding method) (ii) Main locations where consumables are used (2) Repair method To be described when specially recommended by the manufacturer of corrosion resistant steel. Description of general repair methods other than the above should preferably be described. 6.2.1.3 Usage records (1) Areas of use of corrosion resistant steel The areas coated in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)) may be excluded. (2) Brand of corrosion resistant steel and plate thickness (nominal thickness) (1) and (2) above may be substituted by the information given in the hull-related approved drawings. However, the brand of each corrosion resistant steel is to be indicated in the drawings included in the Technical File. The test certificates and actual measured values of plate thickness of each corrosion resistant steel, and individual welding conditions need not be included. 6.2.2 Records after ship enters service 6.2.2.1 Overview of repairs to COT in which corrosion resistant steel is used (1) Areas of repair work (2) Repair method (replacement by corrosion resistant steel or coating) (3) Records of the brand of corrosion resistant steel used, plate thickness and welding consumables (brand name and welding method) if corrosion resistant steel is used (4) Records in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)), if coating is used -9-
6.2.2.2 Repairs that require records to be maintained as mentioned in paragraph 6.2.2.1 above include the following: (1) Replacement by corrosion resistant steel (2) Application of coating on members in which corrosion resistant steel is used (including cases where corrosion resistant steel is replaced with conventional steel and coating) *1 (3) Repairs of pitted parts or areas by overlay welding *2 *1 *2 Coatings of parts in which corrosion resistant steel has been used during construction are to be recorded in the Corrosion Resistant Steel Technical File even if coatings have been applied to the parts at a later stage. In such cases, the coating records need not be included in the Coating Technical File. Repairs of pitted parts or areas by overlay welding means building up the weld in the pitted part or area to compensate for the reduction in plate thickness due to pitting. The wastage limit of the pitted part or area is to be as deemed appropriate by the Surveyor. However, the standard value of the permissible wastage amount is to be taken as about 40% of the original thickness. When repairs by welding are to be carried out, welding consumables verified as appropriate for the relevant corrosion resistant steel are to be used. The full depth of the pitting is to be filled up by the weld metal. If welding materials that have not been verified as compliant materials are to be used, an appropriate range around the repaired part is to be coated suitably after the repairs. 6.2.2.3 Plate thickness records during periodical surveys are to be stored in files specified by the Society; they need not be recorded in the Technical File. -10-
Chapter 7 Requirements for Corrosion Protection of Appurtenances 7.1 Permanent means of access provided for inspection not integral to the ship s structure 7.1.1 The phrase those portions of permanent means of access provided for inspection within the area specified in subsection 3.4 that are not integral to the ship s structure in paragraph 3.3.2 of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) refers to permanent means of access provided for inspection (hereafter referred to as means of access ) such as those listed below that are not integral to the ship s structure. - Ladders - Rails - Independent platforms - Steps 7.1.2 Appropriate corrosion protection measures are to be adopted for means of access mentioned in paragraph 7.1.1 above included in sub-paragraph 4.1.1(2) in the area of corrosion protection. When a coating is used, the requirements of Performance Standard for Protective Coatings for COT (MSC.288(87)) are recommended. When corrosion resistant steel is used, in principle, a corrosion resistant steel of a same brand as used in the main structure, is to be used. Other corrosion protection measures are to be left to the discretion of the Society. 7.1.3 If the means of access (conventional steel) in paragraph 7.1.2 above is fitted by welding to the corrosion resistant steel, corrosion protection measures for the welded part on the corrosion resistant steel and for an appropriate distance from the welded part are to be adopted. In this case, coating in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)) for the relevant range is recommended (see Fig. 7.1). Corrosion resistant steel Corrosion resistant steel :Uppermost means of access (conventional steel) :Coating area Fig. 7.1 Range of coating in case of welding the uppermost means of access and corrosion resistant steel 7.1.4 If means of access (conventional steel) in the corrosion protection area given in section 4.1, other than given in paragraph 7.1.2 above is welded with welding consumables that are not indicated on the Type Approval Certificate of the corrosion resistant steel, then it is recommended that the welded part and an appropriate range from the welded part on the corrosion resistant steel be coated in accordance with Fig. 7.2. -11-
Corrosion resistant steel Corrosion resistant steel :Means of access (conventional steel) :Recommended coating area Fig. 7.2 Range of coating in case of means of access other than the uppermost means of access is welded with corrosion resistant steel 7.1.5 If corrosion protection measures other than corrosion resistant steel or coating in accordance with Performance Standard for Protective Coatings for COT (MSC.288(87)) are applied in paragraphs 7.1.2 to 7.1.4 above, the performance of the corrosion resistant steel of the surrounding structure is not to be impaired. 7.2 Access arrangements integral to the ship s structure 7.2.1 The phrase Access arrangements that are integral to the ship structure in paragraph 3.2.2 of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) means access arrangements integral to the ship structure such as the items mentioned below, for move in the COT. - Stiffeners and girders with increased depth for walkways 7.2.2 Appropriate corrosion protection measures are to be adopted for access arrangement given in paragraph 7.2.1. If coating is applied, the provisions of Performance Standard for Protective Coatings for COT (MSC.288(87)) are to be followed. If corrosion resistant steel is used, in principle, corrosion resistant steel of the same brand as that used in the hull structure, is to be used. 7.3 Supporting members, etc. It is recommended that pipes and supporting members for measuring equipment or outfitting items that are not strength members of the hull be protected either by coating or by use of corrosion resistant steel in accordance with the provisions of paragraph 7.1.4. 7.4 Attachments during work In the case of attachments (conventional steel) used only during construction work such as hanging pieces, if welding consumables which are not indicated on the Type Approval Certificate are used, it is recommended that the welded part and an appropriate range of distance from the welded part are coated in accordance with Fig. 7.3. Hanging piece (conventional steel) Trace of removed hanging piece (conventional steel) Corrosion-resistant steel Fig. 7.3 Range of coating when attachments during work are welded to corrosion resistant steel -12-
8.1 Approval Chapter 8 Type Approval 8.1.1 The Society s approval is not needed for a testing organization of corrosion resistant steel, but the testing organization is to be one that has adequate capability to conduct tests and the appropriate facilities for doing so. A surveyor of the Society is to be present at appropriate timings for the approval tests. 8.1.2 Details regarding the Society s type approval procedure for corrosion resistant steel are described in APPENDIX [2]. 8.1.3 The Type Approval Certificate is valid for a period of 5 years from the date of approval. In case when the renewal of approval is carried out, period of validity will be 5 years from the next day after the expiry date of the previous validity. 8.1.4 The provisions for applying for renewal of approval are to be in accordance with 1.5.3 in Chapter 1, Part 1 of the Guidance for the Approval and Type Approval of Materials and Equipment for Marine Use. 8.1.5 Test items in case of additions of applicable welding consumables are to be subjected to corrosion resistance tests for the welded joints specified in Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)). 8.2 Type Approval Certificate 8.2.1 The Type Approval Certificate for approved corrosion resistant steel is to include the following items: (1) Brand and certificate number (2) Manufacturer (3) Chemical composition range (additive elements to improve corrosion resistance) (4) Maximum thickness (5) Steelmaking process (6) Casting process (7) Rolling method and heat treatment process (8) Applicable welding consumables and welding method (9) Applicable areas (strength deck or inner bottom plating or both) (10) Period of validity of approval 8.2.2 Sample forms of the Type Approval Certificate and the Particulars of Approval are shown as attachment 2 in APPENDIX [2] of these Guidelines. -13-
Chapter 9 Welding Work 9.1 Welding consumables The welding consumables of the brand stated in the Type Approval Certificate for corrosion resistant steel are to be used. If welding consumables other than the above are used, the provision of Sec. 4.2.9 is to apply. 9.2 Approval of welding procedure An approved welding procedure and its specifications for rolled steel for hull are to be used for welding work [as appropriate to the grades (excluding subscripts related to corrosion resistance) and plate thickness of corrosion resistant steel to be used, welding consumables, welding position, etc.] of corrosion resistant steel. 9.3 Welding work standards Welding work standards accepted for conventional steel may be used. -14-
10.1 Product inspection Chapter 10 Surveys 10.1.1 Product inspection of corrosion resistance is to be carried out as described below. (1) Product inspection of corrosion resistance is to be conducted in accordance with APPENDIX [3-1]: Special Requirements for Product Tests of Corrosion Resistance. (2) If the Society has approved beforehand that the effect of all elements intentionally added or controlled for improving corrosion resistant performance has been quantitatively clarified by technical data in accordance with the provisions of APPENDIX [3-2], then sub-paragraph (1) above can be substituted after verifying that the chemical composition of ladle furnace are within the range of controls of the approved chemical composition. 10.1.2 At least the items below are to be included in the test certificate: (1) Order or order number and ship s name or ship's number (2) Identification number or mark and brand (3) Manufacturer's name (4) Grade (5) Chemical composition (if the alternative method of 10.1.1(2) is used, test values of added or controlled elements for improving corrosion resistance) (6) Carbon equivalent (7) Mechanical test results (8) Heat treatment conditions 10.2 Survey during the construction stage 10.2.1 The Society s surveyor is to confirm the test certificate of corrosion resistant steel to be used during the construction stage, and verify that corrosion resistant steel has been used at the appropriate locations. 10.2.2 The verification in 10.2.1 is to be implemented periodically, and the frequency is to be determined considering the quality control status of each shipyard. However, if some deficiency is found, the Society is to formulate the necessary measures separately in consultation with the shipyard or the manufacturer of the corrosion resistant steel with regard to the inspection method, inspection frequency and countermeasures to be taken with respect to the deficient location. -15-
APPENDIX [1-1] Supplement to Corrosion Resistance Test Procedure 1 Corrosion resistance tests of corrosion resistant steel for strength deck 1.1 Corrosion resistance tests of corrosion resistant steel for strength deck specified in Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) are to be implemented in accordance with the attached Appendix of Annex to the said performance standard (hereafter referred to as the Appendix in this APPENDIX). This section has been prepared as a supplement for testing personnel; if a different test procedure is used, the approval of the Society is to be obtained beforehand. (1) Test specimens are to consist of corrosion resistant steel and conventional steel for comparison with it. Each test specimen is to be sampled from the surface of the steel. The conventional steel is to have a composition satisfying Table 1 of Appendix. (2) Twenty test specimens of corrosion resistant steel and 5 test specimens of conventional steel are to be taken in the sizes described in sub-paragraph 2.1.1.5 of Appendix. The surfaces of these specimens are to be sanded to #600. After sanding, the length, width and thickness of each specimen are to be measured using digital calipers or a micrometer, and the initial weight is to be measured to an accuracy of 0.1 mg. (3) Non-test surfaces of the specimens (rear surface and end surfaces) are to be sealed by tape or paint. Tape or paint that can withstand the test environment (environment that includes H 2 S and SO 2 ) over the long term should be selected for use. (4) All the test specimens are to be installed at the same distance from the gas outlet as shown in Fig. 2 of Appendix. Each test specimen is to be fitted to the holder just before the start of the test. (5) Each test specimen is to be controlled so that the temperature pattern shown in sub-paragraph 2.1.1.9 of Appendix is obtained. A control method such as the constant temperature bath shown in Fig. 2 of Appendix may be used, or control by circulating water may be used. (6) The temperature of each test specimen and the temperature of the distilled water used are to be checked before the test to confirm that they are appropriately controlled. (7) Since gases such as H 2 S and SO 2 are being used, the tests should always be conducted in an area with good ventilation. (8) The gases to be used are to consist of two types: 8±2% O 2-26±4% CO 2-200±20 ppm SO 2 - bal.n 2 and 1,000±100 ppm H 2 S - bal.n 2. Equal quantities of these gases are to be mixed just before the test tank and then blown into the test tank. (9) The gas flow rates up to 24 hours before the start of the test are to be 100 cc/min. or more, and subsequently, are to be 20 cc/min. or more. (10) Each test specimen is to be removed after replacing the space in the test tank by N 2. (11) After the test, the corrosion products are to be removed from the test -16-
specimen using a cutter knife or other means, and then the residual corrosion products are to be removed by chemical means. The removal of corrosion products can be accomplished by methods such as those described in ISO 8407. (12) The weight of each test specimen after removal of corrosion products is to be measured, and the corrosion loss and ECL are to be determined according to the procedure described in 2.1.2 of Appendix. 2 Corrosion resistance tests of corrosion resistant steel for inner bottom plating 2.1 The corrosion resistance tests of corrosion resistant steel used in the construction of inner bottom plating specified in Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) are to be conducted in accordance with Appendix. This section has been prepared as a supplement for testing personnel; if a different testing procedure is used, then the approval of the Society is to be obtained beforehand. (1) The test period, number and size of the test specimens, are to be in accordance with paragraph 2.2.1 of Appendix. (2) The edges of the hole (dia. 2 mm) for suspending the test specimen should preferably be rounded after making the hole. (3) Digital calipers or a micrometer are to be used to measure the dimensions of the test specimens. The length, breadth and thickness of the test specimens are to be measured in millimeters up to an accuracy of 2 digits after the decimal point. (4) The weight of the test specimen before the test is to be measured to an accuracy of 0.1 mg. (5) Before the test, and just before conducting the immersion test, all surfaces of the test specimen are to be sanded using emery paper No. 600, washed with ethanol, dried using a blower, and placed in a beaker containing acetone. (6) After step (5), the beaker with the test specimen should be placed in an ultrasonic cleaner to degrease it. Later, it should be removed, washed in ethanol, and dried using a blower. (7) Mixing solutions and test method (for instance, when a 1-liter beaker is used) (a) Mix 15.0 ml of 6-N hydrochloric acid in 1000 ml of pure water, add 113.0 g of sodium chloride, and take the required amount of the solution (about 3 liters is required for each base metal test specimen, or about 7 liters is required for each welded part test specimen). (Example of reagent brand) * 6N hydrochloric acid: Wako Pure Chemical Industries Ltd., 6N hydrochloric acid for analysis (Code: 084-05425; 500 mm) * Pure water: Wako Pure Chemical Industries Ltd., Distilled water (Code: 041-16786) * Sodium chloride: Wako Pure Chemical Industries Ltd., Special Grade (Code: 191-01665; 500g) (b) Prepare the solution only once; maintain the solution to be replaced at a temperature of 30 C. (c) To check ph, take a small quantity of the test solution prepared as mentioned above (say 10 ml each), and take each sample quantity diluted 10 times and 100 times with pure water. Use a ph meter to confirm that -17-
each of these diluted solutions satisfies the following conditions. * ph of solution diluted 10 times: 2.1 ±0.2 * ph of solution diluted 100 times: 3.1 ±0.2 Note: Use an accurate ph meter that has been correctly calibrated. The measurement is to be performed after dilution; this is because variations in reading using the ph meter can occur since the ph of the stock solution may be too low. (d) To prevent evaporation of the solution, cover the mouth of the beaker using PARAFILM (laboratory film), or some other suitable means. (e) Place the beaker in a constant temperature bath maintained at 30 C, and maintain its temperature at 30 C. (f) Take out the beaker, remove the laboratory film, and stretch a wire (covered by plastic, etc.) over the mouth of the beaker so that the test specimen can be suspended at the center of the beaker. (g) Pass a chemically-resistant string (such as a fishing line) through the hole in the test specimen. Adjust the length of the string such that the test specimen is immersed at the center of the solution in the beaker, and tie it to the wire stretched at the mouth of the beaker. (h) After immersing the test specimen for 24 hours, remove it, and transfer it to the next beaker containing the solution maintained at the specific temperature. (i) After a specific amount of time described in Appendix has elapsed, remove the test specimen, wash it with water using sponge, etc., clean it in ethanol, and dry it using a blower. Then measure the weight of the specimen using the same weighing scale to an accuracy of 0.1 mg. -18-
APPENDIX [1-2] Judgment Criteria for Results of Corrosion Resistance Tests of Welded Joint 1 Judgment criteria for results of corrosion resistance test of welded joint 1.1 Use niter solution (for example, nitric acid 1.5 ml, alcohol (methyl, ethyl or amyl) 100 ml) to corrode the cross section so that the boundary of the weld metal and base metal (including the Heat Affected Zone) can be distinguished, and then take a 1000X microphotograph. If judgment is difficult at 1000X magnification, microphotographs taken at additional magnifications of 25X, 100X or 500X may be used. 1.2 Test specimens with abnormal corrosion during the test may be excluded from judgment. In this case, it will be necessary to retest the same number of specimens as the number of specimens that have been excluded. 1.3 Figure A1-2.1 shows an example of the photograph used for judging the test results of the welded part (example of corrosion resistant steel for inner bottom plating, no step) -19-
Fig. A1-2.1 Example of photo for judging the results of corrosion resistance tests of welded part (example of corrosion resistant steel for inner bottom plating, no step) -20-
APPENDIX [1-3] Standard Format for Results of Corrosion Resistance Tests 1 Test results of corrosion resistant steel for strength deck 1.1 The following items are to be included in the results of corrosion resistance test of corrosion resistant steel for the strength deck: (1) Test location (2) Test date (3) Standard (4) Plate thickness (5) Test report number (6) Signature of surveyor witnessing test 1.2 In addition to 1.1 above, the following items are to be included in the test results of base metal: (1) Test specimen number (2) Size of test specimen before the test (thickness, width, length) (3) Results of weight measurements before and after the test (4) Concentration of gases used (O 2, CO 2, SO 2, H 2 S, N 2 ) (5) Test start time, test completion time (6) Testing period (7) Corrosion loss (CL C, CL 21, CL 49, CL 77, CL 98 ) (8) A value, B value, ECL (9) Judgment of results (10) Remarks (11) Name of person witnessing the test, time and signature (before test and after test) 1.3 In addition to 1.1 above, the following items are to be included in the test results of weld joint: (1) Test specimen number (2) Size of test specimen before the test (thickness, width, length) (3) Brand of welding consumable (4) Welding conditions (5) Concentration of gases used (O 2, CO 2, SO 2, H 2 S, N 2 ) (6) Test start time, test completion time (7) Testing period (8) Photographs (photographs showing external view and corrosion of cross section) (9) Judgment on the existence of step (10) Judgment of results (11) Remarks (12) Name of person witnessing the test, time and signature (before test and after test) 2 Test results of corrosion resistant steel for inner bottom plating 2.1 The following items are to be included in the results of corrosion resistance test of -21-
corrosion resistant steel for the inner bottom plating: (1) Test location (2) Test date (3) Standard (4) Plate thickness (5) Test report number (6) Signature of surveyor witnessing test 2.2 In addition to 2.1 above, the following items are to be included in the test results of base metal: (1) Test specimen number (2) Size of test specimen before the test (thickness, width, length) (3) Results of weight measurements before and after the test (4) Results of measurement of ph of solution before the test (for dilution of 10 times and 100 times) (5) Start time of immersion, completion time of immersion (6) Immersion time (7) Corrosion rate (mm/y) (8) Photographs of external view after test (9) Confirmation of statistical normality of results: refer to Figure 5 of Appendix of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) (10) Judgment of results (11) Remarks (12) Name of person witnessing the test, time and signature (before test and after test) 2.3 In addition to 2.1 above, the following items are to be included in the test results of weld joint: (1) Test specimen number (2) Size of test specimen before the test (thickness, width, length) (3) Brand name of welding consumable (4) Welding conditions (5) Results of measurement of ph of solution before the test (for dilution of 10 times and 100 times) (6) Start time and completion time of immersion (7) Immersion time (8) Photographs (photographs showing external view and corrosion of cross section) (9) Judgment on existence of step (10) Judgment of results (11) Remarks (12) Name of person witnessing the test, time and signature (before test and after test) -22-
APPENDIX [2] Type Approval Procedure for Corrosion Resistant Steel 1 Application for approval A manufacturer who applies for type approval of corrosion resistant steel to the Society is to enter the relevant items in one copy of the approval application (Attachment ), and submit it together with the documents specified in 1.2.2-1 in Chapter 1, Part 1 of Guidance for the Approval and Type Approval of Materials and Equipment for Marine Use, and three sets each of the following documents: (a) Corrosion resistance test plan (b) Technical data related to product tests for confirming corrosion resistance (c) Product test procedure and criteria for passing test (d) Test results or technical data showing that the corrosion resistant steel does not cause any problematic galvanic corrosion with conventional steel in the COT environment 2 Approval of test plan 2.1 The Society will examine the approval test plan submitted according to section 1 above, and where deemed appropriate, the plan will be approved and returned to the manufacturer. 2.2 The approval test items for corrosion resistant steel are as given in paragraphs 2.2.1 to 2.2.3 below. 2.2.1 Tests to confirm the performance of rolled steel for hull specified in 1.4 in Chapter 1, Part 1 of Guidance for the Approval and Type Approval for Materials and Equipment for Marine Use. 2.2.2 Tests to confirm that weldability is equivalent to that of conventional steel shown in Table A2.1. However, these tests may not be conducted again if they form part of the requirements of paragraph 2.2.1. The welding consumables used in the tests shown in Table A2.1 are to be welding consumables for mild steel or high tensile steel. They may be different from the welding consumables used in the corrosion resistance tests of paragraph 2.2.3. 2.2.3 Corrosion resistance test specified in Appendix of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)). -23-
Table A2.1 Test Items, Methods and Judgment Criteria to Confirm Weldability Test Item Test Method Judgment Criteria y-groove weld According to JIS Z3158 or To be as deemed cracking test equivalent method appropriate by the Society. Weldability The value of maximum Maximum According to JIS Z3101 or hardness is not to be over hardness test equivalent method 350. According to JIS G0553 or To be as deemed Macro test equivalent method appropriate by the Society. Weld joint characteristics Butt welding tensile test Butt welding bending test Butt welding Charpy impact test Welding hardness test 2.3 Test samples are to be as given below. According to the provisions of "Guidance for the Approval and Type Approval for Materials and Equipment for Marine Use According to the provisions of Chapter 4, Part M of the Rules for the Survey and Construction of Steel Ships According to the provisions of Chapter 4, Part M of the Rules for the Survey and Construction of Steel Ships According to the provisions of "Guidance for the Approval and Type Approval for Materials and Equipment for Marine Use According to the provisions of Chapter 4, Part M of the Rules for the Survey and Construction of Steel Ships According to the provisions of Chapter 4, Part M of the Rules for the Survey and Construction of Steel Ships According to the provisions of Chapter 4, Part M of the Rules for the Survey and Construction of Steel Ships The value of maximum hardness is not to be over 350. 2.3.1 Tests are to be conducted for corrosion resistant steel of typical chemical composition after referring to technical data related to product tests for confirming corrosion resistance of section 1.(b) above. 2.3.2 If an alternative to product test of corrosion resistance by controlling the chemical composition according to the provisions of APPENDIX [3-2] is used, then a test sample that makes it possible to confirm the validity of the control range (upper limit, lower limit) of the elements which are added for improving the corrosion resistance by the data submitted to prove the control range is to be used. Further, the number of the specimens tested is to be increased, if necessary. 2.3.3 In addition to paragraph 2.3.2 above, the Society may require additional tests in the following cases: -24-
(1) When the Society determines that since the control range is set by the theoretically analysis of each element based on existing data, the number of corrosion resistance tests conducted in accordance with Appendix of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)) is too few to adequately confirm the validity of the control range of chemical composition; (2) When the Society determines that the data of the corrosion resistance test result obtained for setting the control range of chemical composition varies too widely; (3) When the Society determines that the validity of the corrosion resistance test result for setting the control range of chemical composition is insufficient, or has some flaws; (4) When the Society s surveyor has not attended the corrosion resistance tests for setting the control range of chemical composition, and the Society determines that additional testing is necessary in order to confirm the validity of the test result data; and (5) When the Society determines that it is necessary, other than cases (1)~(4) above. Remarks: The chemical composition of the corrosion resistant steel is to be within the range specified for rolled steel for hull. Elements to be added for improving the corrosion resistance and for which content is not specified are to be generally within 1%. 3 Confirmation of Manufacturing and Quality Control Procedure The Society may carry out surveys of the actual situation of the manufacturing plant or others on the basis of the data submitted according to the requirement of section 1 above as deemed necessary. In this case, the manufacturer is to provide the necessary information related to this survey. The time of the survey is to correspond, as a rule, to either the time of rolling of the corrosion resistant steel or the time when the approval test is carried out. 4 Carrying out the approval test The manufacturer is to carry out the approval test in accordance with the approved test plan. 5 Attendance of the Society s Surveyor for Test The Society s Surveyor is to be present, as a rule, when the test samples for the approval test are being identified and when the approval test is being carried out. 6 Test results After completion of the approval test, the manufacturer is to produce the report of the approval test and is to submit 3 copies to the Society (branch office concerned) upon receiving confirmation of its content by the Society s Surveyor. The test report is to be appended with work records relating to steel making, ingot-making (casting), rolling and heat treatment of the test samples. The standard format for results of corrosion resistance test is according to APPENDIX [1-3]. The test results are for tests of corrosion resistant steel manufactured at the said plant. -25-
7 Approval The Society will grant type approval for corrosion resistant steel which have been deemed appropriate based on the data submitted according to the provisions of section 1-6 above. In this case, the Type Approval Certificate containing the manufacturer s name and period of validity of the certificate will be issued. The approval items, etc., will be entered in the Particulars of Approval (See attachment ). -26-
Attachment1 Application for type approval of corrosion resistant steel for COT Nippon Kaiji Kyokai. Branch Date: (Name of branch office) (Manufacturer s Doc. No.) (Date of application) (Address) (Manufacturer) (Department and Person in charge) (Tel. No. and Fax. No.) We hereby request type approval of corrosion resistant steel for COT described hereunder in accordance with the requirements in 1.2, Part K of the Rules for the Survey and Construction of Steel Ships. 1. Name of works 2. Brands (Example: XXCR1) 3. Material grade (Example: KD36-RCW) 4. Areas of application (Example: Strength deck and inner bottom plating) 5. Deoxidation practice (Example: Fine grained killed steel) 6. System of constituents (Example: Si-Mn-Al-Ni) 7. Control range of Chemical composition (Additive elements for ensuring corrosion resistance) (Example) Ni (Example) 0.2 to 0.4% 8. Heat treatment (Example: Thermo-Mechanical Controlled Processing (TMCP)) 9. Plate thickness for approval (Example: Max. plate thickness: 25 mm) 10. Steel making process (Example: Basic oxygen furnace steelmaking process) 11. Steel casting process (Example: Continuous casting) 12. Welding consumable (Example: BT-999 (Manufacturer: Nippon Welding & Eng. Co., Ltd.) 13. Welding method (Example: Submerged arc automatic welding) 14. Miscellaneous 15. Date for factory inspection 16. Date for selection of test samples 17. Date for approval test 18. Submitted documents (a) Approval test plan 3 copies (b) Technical data 3 copies -27-
Attachment2 Certificate No. NKR-xxxROL TYPE APPROVAL FOR CORROSION RESISTANT STEEL This is to certify that Xxxx Steel Co., Ltd. Yyyy Works Chiyoda, Tokyo Japan has been approved for type and manufacturing process by NIPPON KAIJI KYOKAI in accordance with the requirements of IMO Resolution MSC.289(87) Performance Standard for Alternative Means of Corrosion Protection for Cargo Oil Tanks of Crude Oil Tankers, 1.2, Part K of the Society's "Rules for the Survey and Construction of Steel Ships" and Chapter 1, Part 1 of the Society s Guidance for the Approval and Type Approval of Materials and Equipment for Marine Use. The details of approval conditions to which this approval applies are given in the PARTICULARS OF APPROVAL listed on the reverse of this certificate. On this effects, products for ships classed with the Society are to be manufactured, tested and inspected in compliance with the relevant Rules and Guidelines of the Society. This certificate is valid until the xxth day of December 2015. Issued at Tokyo on the xxth day of December 2010. Initial Approval Date: xxth December 2010 XXXXXX General Manager Material and Equipment Department -28-
List of PARTICULARS OF APPROVAL Ref. No. Date 1. 10EWxxxxROL xx DEC. 2010-29-
No.: 10EWxxxxROL Date: xx December 2010 PARTICULARS OF APPROVAL Type Approval Condition for Corrosion Resistant Steels 1. Manufacturer: Xxxx Steel Co., Ltd. Yyyy Works 2. Kind of Product : Steel Plates 3. Applicable Area : Strength Deck and Inner Bottom 4. Grade: KA32-RCW 5. Brand: XXCR1 6. Deoxidation Practice: Fine-grained Killed 7. System of Constituents: Si-Mn-Al-Ni 8. Maximum Thickness: 50 mm 9. Heat Treatment: TMCP (Thermo-Mechanical Controlled Processing) 10. Steel Making Process: Basic Oxygen Furnace 11. Casting Process: Continuous Casting 12. Standard: According to Table 1 in addition to Part K of the Rules Table 1 : Chemical Composition to confirm corrosion resistance (%) Max. Min. -30-
No.: 10EWxxxxROL Date: xx December 2010 13. Test Certificate: The items given in (a) and (b) below are to be recorded, in addition to the items specified in Part K of the Rules. (a) TMCP as a heat treatment condition (b) Test result of chemical composition specified in Table 1 14. Welding Method and See Table 2. Welding Consumables: Table 2 : Welding Method and Welding Consumables Welding Consumables Welding Method XXXXXXX General Manager Material and Equipment Department -31-
1 Scope APPENDIX [3-1] Special Requirements for Product Tests of Corrosion Resistance 1.1 These requirements apply to corrosion resistant steel specified in these guidelines. 1.2 The types of steel that can be applied with these requirements are steel plates and steel flats. 1.3 If the Society deems appropriate, these requirements can be applied to steels other than mentioned in paragraph 1.2 above. 2 Corrosion-resistant performance, etc. 2.1 The required corrosion resistance is to be confirmed to ensure that it satisfies the specified judgment criteria from the corrosion resistance tests using test samples taken from the product. 2.2 The corrosion resistance test method and judgment criteria are to be in accordance with Appendix of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)). 3 Selection of test samples 3.1 One test sample is to be taken from steel belonging to the same charge. 3.2 The sampling position of the test sample is to be left to the discretion of the Society. 4 Sampling of test specimens 4.1 The dimensions, shape and number of samples of test specimen to be taken, are to be in accordance with Appendix of Annex to Performance Standard for Alternative Means of Corrosion Protection for COT (MSC.289(87)). 4.2 The sampling position of the test specimen (direction corresponding to direction of rolling, sampling position in the plate thickness direction, etc.) is to be left to the discretion of the Society. 5 Re-tests 5.1 If the specified judgment criteria have not been satisfied in the tests, one test sample may be taken from the same charge, and re-tested. In this case, if the average value of the tests has satisfied the judgment criteria, then all the steels belonging to the same charge may be accepted. 5.2 If the provisions of paragraph 5.1 above have not been complied with, the steels from which the test specimen was sampled are to be treated as having failed. However, at the -32-
manufacturer s option, if steel plates not exceeding 50 tons are taken as one lot from the remaining steel belonging to the same charge, and one test sample is taken from each lot, the specified tests may be conducted again for each lot. If the results of the tests satisfy the judgment criteria, then all the steels included in that lot may be accepted. 6 Markings 6.1 Steel plates that have complied with these requirements will be indicated by adding letters to the end of the grade of steel as shown in Table A3-1.1. (Example of indication: KA36-RCB) Table A3-1.1 Indication Method According to Corrosion Resistance Properties of Each Type of Corrosion Resistant Steel Type of steel Type of corrosion resistant steel Distinguishing letters Rolled steel for hull For strength deck For inner bottom plating For both strength deck and inner bottom plating RCU RCB RCW -33-
APPENDIX [3-2] Handling of Alternative to Product Tests of Corrosion Resistance by Controlling Chemical Composition 1 Setting the control range of chemical composition 1.1 The manufacturer is to keep ready the data adequate for proving the validity of the control range (upper and lower limits) for all additive elements that the manufacturer has intentionally added or is controlling to improve corrosion resistance, and is to receive the Society's approval for this validity. 1.2 The effect of each element may be evaluated by using sufficient corrosion resistance tests whose combination of additive elements is considered by design of experiments, etc. Also, using the evaluation results, the control range given by the parameters determined by the equation of the correlation between each chemical composition and corrosion-resistant performance may be used. 1.3 The corrosion resistance test is to be conducted in accordance with Appendix of Annex to Performance Standard for the Alternative Means of Corrosion Protection for COT (MSC.289(87)). 1.4 In addition to products manufactured on a production line, test materials manufactured using testing equipment may be used as steels to be tested. 1.5 The Society may attend the corrosion resistance test described section 1.1 above for keeping data ready, if necessary. 1.6 When the Society determines that the data of section 1.1 above is insufficient because the number of corrosion resistance tests for setting the control range of chemical composition is too few, or the corrosion resistance test result varies too widely, the data adding to section 1.1 above or the additional corrosion resistant test at the type approval test according to paragraph 2.2.3 of APPENDIX [2] is required. 2 Product test of corrosion resistance by controlling chemical composition 2.1 The chemical composition of a particular steel can be verified to be within the control range mentioned above by ladle analysis, and thus, the corrosion resistance test can be substituted. -34-
ANNEX PERFORMANCE STANDARD FOR ALTERNATIVE MEANS OF CORROSION PROTECTION FOR CARGO OIL TANKS OF CRUDE OIL TANKERS 1 PURPOSE This Standard provides technical requirements for the minimum standard for means of corrosion protection or utilization of corrosion resistant material other than protective coating to be used for cargo oil tanks during construction of crude oil tankers. 2 DEFINITION 2.1 Alternative means is a means that is not a utilization of protective coating applied according to the Performance standard for protective coating for cargo oil tanks of crude oil tankers (resolution MSC.288(87)). 2.2 Corrosion resistant steel is steel whose corrosion resistance performance in the bottom or top of the internal cargo oil tank is tested and approved to satisfy the requirements in this Standard in addition to other relevant requirements for ship material, structure strength and construction. 2.3 Target useful life is the target value, in years, of the durability for which the means of corrosion protection or utilization of corrosion resistance material is designed. 3 APPLICATION 3.1 As of the date of the development of this Standard, corrosion resistant "steel" is the only recognized possible means for corrosion protection or utilization of corrosion resistant material to maintain the required structural integrity for 25 years, as an alternative to protective coating. If corrosion resistant steel is to be used as alternative means, it shall comply with the Performance Standard for corrosion resistant steel as set out in the annex. 3.2 When a novel type of alternative means to which the provisions in the annex are not applicable has been developed, and recognized by the Organization, a specific performance standard including testing procedure(s) should be developed by the Organization by adding a new annex to this Standard, taking into account experience gained through field tests for the novel prototype alternative conducted in accordance with SOLAS regulation II-1/3-11.4. -35-
ANNEX PERFORMANCE STANDARD FOR CORROSION RESISTANT STEEL 1 PURPOSE This Standard provides technical requirements for the minimum standard for corrosion resistant steel to be used for cargo oil tanks during construction of new crude oil tankers. 2 GENERAL PRINCIPLES 2.1 The ability of the corrosion resistant steel to reach its target useful life depends on the type of steel, application and survey. All these aspects contribute to the good performance of corrosion resistant steel. 2.2 Technical File 2.2.1 Documents and information stipulated in 2.2.3 and 2.2.4 shall be documented in the Technical File. The Technical File shall be verified by the Administration. 2.2.2 The Technical File shall be kept on board and maintained throughout the life of the ship. 2.2.3 New construction stage The Technical File shall contain at least the following items relating to this Standard and shall be delivered by the shipyard at new ship construction stage:.1 copy of a Type Approval Certificate;.2 technical data, including:.2.1 approved welding methods and welding consumables; and.2.2 repairing methods recommended by the manufacturer (if any); and.3 records of the application, including:.3.1 applied actual space and area of each compartment; and.3.2 applied product and its thickness. 2.2.4 In-service maintenance, repair and partial renewal In-service maintenance, repair and renewal activities shall be recorded in the Technical File. 3 CORROSION RESISTANT STEEL STANDARD 3.1 Performance standard -36-
This Standard is based on specifications and requirements which intend to provide a target useful life of 25 years, which is considered to be the time period, from initial application, over which the thickness diminution of the steel is intended to be less than the diminution allowance and watertight integrity is intended to be maintained in cargo oil tanks. The actual useful life will vary, depending on numerous variables including actual conditions encountered in service. 3.2 Standard application Corrosion resistant steel for cargo oil tanks applied to the area specified in 3.4 during the construction of crude oil tankers shall at least comply with the requirements in this standard and this should be considered as a minimum. 3.3 Special application 3.3.1 This Standard covers corrosion resistant steel requirements for ship s steel structures. It is noted that other independent items are fitted within the tanks to which measures are applied to provide protection against corrosion. 3.3.2 It is recommended that this Standard or the Performance standard for protective coating for cargo oil tanks is applied, to the extent possible, to those portions of permanent means of access provided for inspection within the area specified in 3.4 that are not integral to the ship s structure, such as rails, independent platforms, ladders, etc. Other equivalent methods of providing corrosion protection for the non-integral items may also be used, provided they do not impair the performance of the corrosion resistant steel of the surrounding structure. Access arrangements that are integral to the ship structure, such as increased stiffener depths for walkways, stringers, etc., are to fully comply with this Standard or the Performance standard for protective coating for cargo oil tanks, when located within the areas specified in 3.4. 3.3.3 It is also recommended that supports for piping, measuring devices, etc., be provided with corrosion protection in accordance with the non-integral items indicated in 3.3.2. 3.4 Area of application The following areas are the minimum areas that shall be protected according to this Standard:.1 Deckhead with complete internal structure, including brackets connecting to longitudinal and transverse bulkheads. In tanks with ring frame girder construction the underdeck transverse framing to be protected down to level of the first tripping bracket below the upper faceplate..2 Longitudinal and transverse bulkheads to be protected to the uppermost means of access level. The uppermost means of access and its supporting brackets to be fully protected..3 On cargo tank bulkheads without an uppermost means of access the protection to extend to 10% of the tanks height at centreline but need not extend more than 3 m down from the deck..4 Flat inner bottom and all structure to height of 0.3 m above inner bottom to be -37-
protected. Figure 1 3.5 Basic requirements The requirements for corrosion resistant steel to be applied at ship construction for cargo tanks in crude oil tankers meeting the performance standard specified in 3.1 are to use approved corrosion resistant steels according to the conditions specified in the Type Approval Certificate and the Technical File to protect the area of application indicated in 3.4. 4 APPROVAL 4.1 Corrosion resistant steel shall be tested according to the appendix, or equivalent, for approval. The corrosion resistant steel tested prior to entry into force of this Standard may be accepted, provided that the steel is tested according to the test procedure in the appendix, or equivalent. 4.2 Results from prequalification tests (4.1) of the corrosion resistant steel shall be documented, and a Type Approval Certificate shall be issued if found satisfactory by the Administration. 4.3 The Type Approval Certificate shall include following information:.1 product name and identification mark and/or number;.2 materials, components and corrosion resistance process of the steel;.3 steel thickness;.4 welding methods and welding consumables; and -38-
.5 applicable area (upper and/or inner bottom plate). 5 INSPECTION AND VERIFICATION REQUIREMENTS To ensure compliance with this Standard, the Administration shall carry out survey(s) during the construction process and verify that approved corrosion resistant steel has been applied to the area required. -39-
APPENDIX TEST PROCEDURES FOR QUALIFICATION OF CORROSION RESISTANT STEEL FOR CARGO TANKS IN CRUDE OIL TANKERS 1 Scope These Procedures provide details of the test procedure referred to in 4.1 of this Standard. 2 Testing Corrosion resistant steel shall be verified by the following tests. 2.1 Test on simulated upper deck conditions 2.1.1 Test condition Tests on simulated upper deck conditions in cargo oil tank (COT) shall satisfy each of the following conditions:.1 Corrosion resistant steel and conventional steel shall be tested at the same time..2 The chemical composition of conventional steel shall comply with the requirements of table 1. The mechanical properties of the test specimen should be representative of steel used in its intended shipboard application. Table 1 Chemical composition for conventional steel (%) C Mn Si P S 0.13-0.17 1.00-1.20 0.15-0.35 0.010-0.020 0.002-0.008 Al(acid soluble min) Nb max. V max. Ti max. Nb+V+Ti max. 0.015 0.02 0.10 0.02 0.12 Cu max. Cr max. Ni max. Mo max. Others max. 0.1 0.1 0.1 0.02 0.02(each).3 The tests for corrosion resistant steel shall be carried out for 21, 49, 77 and 98 days. The tests for conventional steel shall be carried out for 98 days. The tests for welded joints shall be carried out for 98 days..4 There are to be five test pieces for each test period..5 The size of each test piece is 25 ± 1 mm x 60 ± 1 mm x 5 ± 0.5 mm. The surface of the test piece shall be polished with an emery paper #600. The size of the test piece for a welded joint is 25 ± 1 mm x 60 ± 1 mm x 5 ± 0.5 mm, including 15 ± 5 mm width of the weld metal part..6 The surface of the test piece, except for the tested surface, shall be protected from -40-
corrosive environment in order not to affect the test results..7 The test apparatus consists of a double chamber, and the temperature of the outer chamber is to be controlled..8 Simulating the condition of the actual upper deck, the test cycle runs with distilled water and simulated COT gas (4 ± 1% O2-13 ± 2% CO2-100 ± 10 ppm SO2-500 ± 50 ppm H2S - 83 ± 2% N2). A sufficient distance between the surface of the test piece and the distilled water is to be kept to avoid splashing of distilled water. The minimum gas flow rate is 100 cc per minute for the first 24 h and 20 cc per minute after 24 h..9 The test pieces shall be heated for 19 ± 2 h at 50 ± 2 C and 3 ± 2 h at 25 ± 2 C and the transition time is to be at least 1 h. The time for 1 cycle is 24 h. The temperature of the distilled water is to be kept at not higher than 36 C, while the temperature of the test pieces is 50 C. Figure 1 - Test piece of this test Figure 2 - An example of simulated corrosion test apparatus for upper deck 2.1.2 Test results of base metal Prior to the testing, the following measured data shall be reported:.1 size and weight of the test piece; and, after the testing, the following measured data shall be reported:.2 weight loss (difference between initial weight and weight after testing) of conventional steel (WC) and corrosion resistant steel (W21, W49, W77 and W98); -41-
.3 corrosion loss of conventional steel (CLC) and corrosion resistant steel (CL21, CL49, CL77 and CL98), calculated by the following formulae: 10 WC CLC ( mm) S D 10 W21 CL21( mm) S D 10 W49 CL49( mm) S D 10 W77 CL77( mm) S D 10 W98 CL98( mm) S D whereby: WC: weight loss of conventional steel (g) (average of five test pieces) W21: weight loss of corrosion resistant steel after 21 days (g) (average of five test pieces) W49: weight loss of corrosion resistant steel after 49 days (g) (average of five test pieces) W77: weight loss of corrosion resistant steel after 77 days (g) (average of five test pieces) W98: weight loss of corrosion resistant steel after 98 days (g) (average of five test pieces) S: surface area (cm 2 ) D: density (g/cm 3 ). The test is considered to be carried out appropriately if CLC is between 0.05 and 0.11 (corrosion rate is between 0.2 and 0.4 mm/year). The concentration of H2S in simulated COT gas may be increased for adjusting CLC;.4 coefficients A and B of corrosion resistant steel, calculated from the test results for 21, 49, 77 and 98 days by least square method. Corrosion loss of corrosion resistant steel is described as follows: CL A t B A(mm) and B: coefficient -42-
t: test period(days);.5 estimated corrosion loss after 25 years (ECL) calculated by the following formula: B ECL(mm) = A ( 25 365). 2.1.3 Test results of welded joint The surface boundary between base metal and weld metal shall be observed by microscope at 1,000 times magnification. 2.1.4 Acceptance criteria The test results based on provisions of 2.1.2 and 2.1.3 shall satisfy the following criteria:.1 ECL(mm) 2 (for base metal); and.2 no discontinuous surface (e.g., step) between the base metal and weld metal (for welded joint). 2.1.5 Test report The test report shall include the following information:.1 name of the manufacturer;.2 date of tests;.3 chemical composition and corrosion resistant process of steel;.4 test results according to 2.1.2 and 2.1.3; and.5 judgement according to 2.1.4. 2.2 Test on simulated inner bottom conditions 2.2.1 Test condition Tests on simulated inner bottom conditions in cargo oil tanks (COT) should satisfy each of the following conditions:.1 The test shall be carried out for 72 h for base metal, and 168 h for welded joint..2 There are to be at least five test pieces of corrosion resistant steel for base metal and welded joint, respectively. For comparison, at least five test pieces of base metal of conventional steel should be tested in the same condition..3 The size of each test piece is 25 ± 1 mm x 60 ± 1 mm x 5 ± 0.5 mm for a specimen with base metal only, and is 25 ± 1 mm x 60 ± 1 mm x 5 ± 0.5 mm for a specimen -43-
with welded joint including 15 ± 5 mm width of weld metal part as shown in figure 3. The surface of the test pieces shall be polished with an emery paper #600, except a hole for hanging..4 The samples are hung in a solution from a fishing line (0.3 mm to 0.4 mm in diameter, made of nylon) to avoid crevice-like and/or localized corrosion. An example of a corrosion test configuration is shown in figure 4..5 The test solution contains 10 mass% NaCl and its ph is 0.85 adjusted by HCl solution. The test solution should be changed to a new one every 24 h to minimize ph change of the test solution. The volume of the solution is more than 20 cc/cm 2 (surface area of test piece). The temperature of the test solution is to be kept at 30 ± 2 C. Figure 3 - Test piece for this test Figure 4 - Simulated corrosion test apparatus for inner bottom 2.2.2 Test results of base metal Prior to the testing, the following data shall be measured and reported:.1 size and weight of test piece; and, after the testing, the following measured data shall be reported: -44-