Tank Coatings Condition Guide - (2004) [PDF]

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First published by Lloyd’s Register, 2004 © Lloyd’s Register, 2004



Lloyd’s Register, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as the ‘Lloyd's Register Group’. The Lloyd's Register Group assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Lloyd's Register Group entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.



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Contents 1. 2. 3. 4. 5. 6. 7. 8.



Introduction How to Use This Guide Marine Coatings Ballast Tank Coatings Ballast Tank Periodical Survey Requirements IACS Method for Assessment of Coating Condition Basic Assessment Tools Coating Condition Examples



4 6 7 9 12 14 21 31



Annex A Inspection of Ballast Tanks Annex B Hot Spots for Corrosion and Other Common Defects Annex C Nomenclature Annex D Coating Condition Assessment Report



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1. Introduction This guide has been produced to supplement the Lloyd’s Register Group’s (hereinafter Lloyd’s Register) Hull Planned Maintenance Scheme Distance Learning Program. It is intended to assist Ship’s Staff in the assessment of tank, hold and space coatings of existing ships for the purpose of determining compliance with the Rules and Regulations for the Classification of Ships. However, it should be stressed that this guide does not itself form part of the Rules and Regulations for the Classification of Ships and is offered for guidance purposes only. Notwithstanding the contents of this guide, users are reminded that, in accordance with the Rules and Regulations for the Classification of Ships, any damage, defect, breakdown or grounding, which could invalidate the conditions for which a class has been assigned, is to be reported to Lloyd’s Register without delay. It will be understood that the task of assessing any tank coating involves a high degree of subjectivity. This guide can only assist in that assessment process by offering examples of typical coatings and their assessments for use as a reference. More detailed guidance on the assessment of protective coating condition together with information on inspection processes and techniques as well as examples of typical structural defects is included in the Hull Planned Maintenance Scheme Training Course Distance Learning Program CD ROM to which this guide is a supplement.



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Lloyd’s Register’s Hull Planned Maintenance Scheme is an alternative route to classification compliance for ship’s hull structure through alignment of classification requirements with an Operator’s existing hull inspection and maintenance programmes. The Hull Planned Maintenance Scheme is only applicable to the following ship types: • • • • • • •



LNG Carriers LPG Carriers Container Ships RO-RO Cargo/Vehicle Carriers Passenger/RO-RO Cargo/Ferries Passenger Ships Specialist ship types (e.g. Cable Layers, etc. and selected Naval Vessels not covered by the Rules and Regulations for the Classification of Naval Ships) • Floating Offshore Installations (e.g. FSOs, FPSOs and other floating ship-type structures covered by the Rules and Regulations for the Classification of a Floating Offshore Installation at a Fixed Location) The information contained within this guide may generally be applied to all ship types, irrespective of their eligibility under the Hull Planned Maintenance Scheme or to any reference to a specific ship type. For further details regarding the Hull Planned Maintenance Scheme, or other maintenance management services provided by Lloyd’s Register, please contact the Classification Group, London at the address shown at the back of this guide.



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2. How to Use This Guide Current regulations require an overall assessment to be made of each individual tank, hold or space and its coating condition assigned a single rating of GOOD, FAIR or POOR. In making any assessment the overall coating condition assigned may need to take into account varying coating conditions in different parts of the tank, hold or space in arriving at an overall single rating. Where there are significant differences in the condition of the coating in different parts of the tank, hold or space these areas should be assessed separately. It is recognised that there is a high degree of subjectivity in making an assessment of coating condition based on visual estimations of percentage areas of breakdown. This guide includes a number of basic tools and representations to make this task simpler. An area determination matrix and an assessment scale for breakdown are provided. A number of representative elements of typical ship’s structures are given to show corresponding percentages of breakdown. Photographs showing various coating conditions are offered as examples to highlight how assessment of elements of the structure are brought together to reach an overall coating condition rating. Coating deterioration and corrosion in general is often linked to inherent or consequential structural defects and the presence of any such defects should always be identified when making coating assessments. An annex to this guide contains useful information on identifying typical areas of ship’s structure liable to corrosion or other common defects. © Lloyd’s Register, 2004



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3. Marine Coatings Coatings or paints are applied to ship’s structure to protect the steel from potential corrosion from salt water and cargoes. It is strongly recommended that protective coatings1 are well maintained while the ship is in service. This will reduce corrosion rates, so maintaining the strength of the ship’s structure both locally and overall. At the time of new construction, it is a Classification requirement that the following areas are to have an efficient protective coating - epoxy or equivalent - applied in accordance with the manufacturer’s recommendations. • All salt water ballast spaces having boundaries formed by the hull envelope (all ships) • Underwater part of the hull in way of the waterline2 The ship operator can decide to include any other requirements for the protective coating of other structural areas and spaces 3 in their new build specification. However, it is a mandatory requirement that a protective coating be applied to the cargo hold structure on bulk carriers.



A Protective Coating is usually to be a hard coating. Other systems (e.g. soft coatings) may be considered as alternatives provided they are applied and properly maintained in compliance with the manufacturer’s specification. 2 Anti-fouling paints are used to coat the bottom of ships to prevent sea-life attaching itself to the hull, thereby slowing down the ship and increasing fuel consumption. Generally the entire submerged zone will be painted. The IMO Convention on the Control of Harmful Anti-fouling Systems on Ships provides additional criteria on this matter. 3 Spaces are separate compartments such as holds and tanks. 1



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The importance of maintaining the original protective coating cannot be over emphasised. Failure to reinstate the original protective coating following deterioration, damage or structural repairs will result in accelerated corrosion of the unprotected structure. This is especially important where structural repairs have been carried out involving the addition or replacement of steel. Further details on the requirements for protective coatings can be found in: • Lloyd’s Register: - Rules and Regulations for the Classification of Ships • Lloyd’s Register: - List of Paints, Resins, Reinforcements and Associated Material • International Association of Classification Societies: - Unified Requirements • Royal Institute of Naval Architects: - Guidelines for the Selection, Application and Maintenance of Corrosion Systems of Ships Ballast Tanks • Tanker Structures Co-operative Forum: - Guidelines for Ballast Tanks Coating Systems and Surface Preparation • Tanker Structures Co-operative Forum: - Condition Evaluation & Maintenance of Tanker Structures



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4. Ballast Tank Coatings Lloyd’s Register’s Rules and Regulations for the Classification of Ships, Part 3, Chapter 2 requires that all salt water ballast tank4 walls, which form a boundary with the hull wall, must have an efficient anti-corrosion coating - ‘epoxy or equivalent’, applied at the time of construction. Generally, a convertible coating (i.e. hard 5 ) is preferred. However, there are acceptable non-convertible types such as the vinyl tars. Ideally, ballast tank coatings should be water repellent, exhibit low water absorption, be as flexible and tough as possible, and light in colour to allow the easier identification of defects during inspection. A properly applied, modern, epoxy ballast tank coating system, of inhibitive or zinc primer and top coats to 250 microns thickness, should give a 10 year life. For additional corrosion control, ballast tank coatings can be supported by sacrificial cathodic protection. Lloyd’s Register produces a list of Recognised Corrosion Control Coatings for tanks. To obtain Recognised status the coating must have either: (a) 2 years minimum satisfactory service experience, (b) satisfactory performance during specific laboratory tests carried out for not less than 1 year, or A Ballast Tank is a tank which is used solely for salt-water ballast. A tank which is used for both cargo and salt-water ballast will be treated as a salt-water ballast tank when substantial corrosion has been found in that tank 5 Hard Coating - A coating which chemically converts during its curing process, normally used for new construction, or non-convertible air drying coating which may be used for maintenance purposes. Hard coating can be either organic or inorganic and defines most typical marine coating such as those based on epoxy, coal tar epoxy, polyurethane, chlorinated rubber, vinyl, zinc epoxy, zinc silicate. 4



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(c)



passed recognised qualification tests.



Similarly, a list of Provisionally Recognised Corrosion Control Coatings is produced and includes those coatings that are undergoing service experience qualification to obtain full recognition. The List of Maintenance Coatings for salt water ballast tanks can be located in Chapter 5 of the Lloyd’s Register List of Paints, Resins, Reinforcements and Associated Materials. Laboratory test data is submitted by the manufacturer to support the application for recognition to ‘make a case’. Lloyd’s Register does not specify such tests. The maintenance coatings can usually be applied on surfaces that have not been prepared to the same quality as by abrasive blasting. Some maintenance coatings are formulated around animal fats, lanolin etc. These are the soft 6 , non-oxidizable type and, in according with Lloyd’s Register’s Rules and Regulations for the Classification of Ships, and IACS Regulations, are subject to examination at Annual Survey. Care is often needed with soft maintenance coatings when used in conjunction with cathodic protection due to saponification7. Care is also required during inspections or surveys to avoid damage or removal of the soft maintenance coating. Application of soft coatings in ballast tanks by floatation8 is not permitted.



Soft Coating - A coating that remains soft so that it wears off at low mechanical impact or when touched; often based on oils (vegetable or petroleum) or lanolin (sheep wool grease). Application of soft coating generally does not allow relaxation of the extent of periodical hull survey requirements of ballast tanks. 7 Saponification - To convert into soap by treating with an alkali. 8 i.e. Float Coats. 6



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Other maintenance coatings are deemed semi-hard9 and do not require annual survey. These coatings may be based on bitumen, in combination with vinyl or vinyl tar, and other petroleum refining byproducts. There are also conversion coatings10 that react with pre-rusted surfaces. The main difficulty with conversion coatings is the specifying of the correct degree of rusting – and guaranteeing the satisfactory removal of hard scale. Maintenance Coatings are given the following classifications: Class 1: Class 2:



A coating that has proven corrosion protection for 3 years minimum. A coating that is undergoing a 3 year qualification period to obtain Class 1 status.



It is important to remember that ballast tanks with coatings in POOR condition, repaired using Class 2 Maintenance coatings, and all ‘soft’ coatings, will be subject to examination at Annual Survey by Lloyd’s Register Surveyors.



Semi-hard Coating - A coating that dries or converts in such a way that it stays flexible although hard enough to touch and walk upon. Application of semi-hard coating may, under certain conditions, allow relaxation of the extent of periodical hull survey requirements of ballast tanks. 10 i.e. Hard Coatings. 9



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5. Ballast Tank Periodical Survey Requirements Lloyd’s Register’s Rules and Regulations for the Classification of Ships, Part 1, Chapter 2 requires that ballast tanks be surveyed periodically for coating breakdown and corrosion. Coating condition is defined as follows:



GOOD



FAIR POOR



condition with only minor spot rusting affecting not more than 20 per cent of areas under consideration, e.g. on a deck transverse, side transverse, on the total area of platings and stiffeners on the longitudinal structure between these components, etc. condition with local breakdown at edges of stiffeners and weld connections and/or light rusting over 20 per cent or more of areas under consideration. condition with general breakdown of coating over 20 per cent or more of areas or hard scale at 10 per cent or more of areas under consideration.



The following sections and examples provide guidance in assessing tank condition. Further Details can also be found in the Tanker Structure Co-operative Forum guide - Condition Evaluation & Maintenance of Tanker Structures. Coatings determined to be in POOR condition, and not repaired, will affect the frequency of future survey inspections of that tank. Steel with POOR coating condition will corrode at an accelerated rate compared to those areas with a GOOD coating condition. This may result in © Lloyd’s Register, 2004



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locally corroded structure or general corrosion depending on the extent of coating breakdown. Operators of ships with tanks assessed in FAIR condition are recommended to repair the areas of coating breakdown to return the tank to GOOD condition. Annual Survey examination of tanks is required for: • Tanks not provided with a protective coating at the time of construction. • Tanks previously with coatings in a POOR condition that have not been repaired. • Tanks having Class 2 or ‘Soft’ maintenance coatings. • Tanks where a previous Survey has identified substantial corrosion11. Intermediate Survey examination of tanks is as per the Annual Survey requirements plus: • General examination of tanks previously assessed GOOD or FAIR. Discretionary thickness measurements. • All tanks on ships greater than 10 years of age. Special Survey examination of tanks is as per the Intermediate Survey requirements plus: • All ballast and peak tanks. • Other tanks as per Lloyd’s Register’s Rules and Regulations for the Classification of Ships, Part 1, Chapter 3.



Substantial Corrosion is wastage of individual plates and stiffeners in excess of 75 per cent of allowable margins, but within acceptable limits. 11



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6. IACS Method for Assessment of Coating Condition A development of the single overall coating condition rating is being considered by the International Association of Classification Societies (IACS) to bring assessment in line with IMO Resolution A.744 (18) and IACS Unified Requirement Z10. This methodology divides the tank, hold or space into a number of “areas under consideration”, the number being dependent on the type of tank being assessed. By dividing the tank into smaller assessment areas it is possible to recognise different coating breakdown and corrosion patterns in corresponding areas of the tank. These areas are sized to allow easy examination and evaluation whilst not being so small as to be structurally insignificant. This more detailed assessment of coating condition differs from the single overall coating condition rating by not averaging the assessment of the individual areas under consideration. In this method the area under consideration with the poorest coating condition will determine any requirement to carry out further inspections at subsequent Annual Surveys. Areas for consideration are detailed as follows: 1 Wing Ballast Tanks (30 areas) 2 Double Bottom Ballast tanks (3 areas) 3 Double Hull Side Tanks (3 areas) 4 Fore Peak Ballast tanks (3 areas) 5 After Peak Tanks (2 areas) © Lloyd’s Register, 2004



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The same principles can be applied to other tanks holds and spaces, e.g. assessment for a centre cargo oil tank or a deep tank will follow the method for a wing ballast tank. The following diagrams show a schematic way to depict and record the coating condition found for each area under consideration. In Figure 1.1 the tank area grid for a wing ballast tank has been partially completed indication areas of G (GOOD) or F (FAIR) rating. Annex D of this guide contains further copies of these schematic diagrams that can be used to record the condition of coatings during actual inspections using a soft pencil or water washable ink pen.



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Fig. 1.1 WING BALLAST TANK



G F F F G G



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G



G



G



G



G F



G



G



G



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Fig. 1.2 DOUBLE BOTTOM BALLAST TANK



KEY:



Aft area



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Middle area



Forward area



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Fig. 1.3 DOUBLE HULL SIDE TANK



KEY:



Upper area



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Middle area



Lower area



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Fig. 1.4 FORE PEAK TANK



KEY:



Upper area



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Middle area



Lower area



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Fig. 1.5 AFT PEAK TANK



KEY:



Upper area



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Lower area



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7. Basic Assessment Tools The following pages contain basic graphical tools to assist with coating condition assessment. These tools should be used as appropriate to assist in determining percentage of total area subject to coating breakdown. Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 2.7 Figure 2.8 Figure 2.9 Figure 2.10



Area Determination Assessment Scale for Breakdown 1% Breakdown shown for typical ship structures 2% Breakdown shown for typical ship structures 5% Breakdown shown for typical ship structures 10% Breakdown shown for typical ship structures 15% Breakdown shown for typical ship structures 20% Breakdown shown for typical ship structures Determination of Coating Conditions Comparison of Common Rust Scales



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Fig. 2.1 AREA DETERMINATION



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Fig. 2.2 ASSESSMENT SCALE FOR BREAKDOWN



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Fig.2.3 1.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig. 2.4 2.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig 2.5 5.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig. 2.6 10.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig. 2.7 15.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig. 2.8 20.0 % BREAKDOWN SHOWN FOR TYPICAL SHIP STRUCTURES © Lloyd’s Register, 2004



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Fig. 2.9 DEFINITION OF COATING CONDITIONS Rating/Condition Spot Rust Light Rust Edges Weld Hard Scale General Breakdown



GOOD Minor Minor



FAIR



POOR



>20 %



20 %



Minor Minor



20 %



Note: The lowest rating within any category shall govern the final rating Fig. 2.10 COMPARISON OF COMMON RUST SCALES ISO Ri 0 Ri 1 R1 2 Ri 3 Ri 4 Ri 5



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European Re 0 Re 1 Re 2 Re 3 Re 5 Re 7



ASTM D 610 Rusted Area 10 0% 9 0.05 % 7 0.5 % 6 1% 4 8% 1 to 2 40 to 50 %



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8. Coating Condition Examples The following pages show examples of tank coatings in various conditions. An assessment of the coating condition is provided in two parts. An overall rating of the coating condition is given as GOOD, FAIR or POOR whilst a % Breakdown is provided for each category of structure to highlight areas of particular interest or concern. These examples are taken from the Tanker Structures Co-operative Forum’s guide - Condition Evaluation & Maintenance of Tanker Structures published by Witherby’s and reproduced here with kind permission. The examples mostly show assessment of tank coatings on typical tanker structures, however, it will be understood that the principles of assessing tank coating condition does not differ between ship types and may be equally applied to bulk carriers, container ships, general cargo ships, etc.



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 1



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



Ship Type: Structure: Age: Note:



Oil Tanker Centre Cargo Oil Tank @ New Construction



General Breakdown



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 2



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



Ship Type: Structure: Age: Note:



Oil Tanker Side Cargo Oil Tank @ SSI



General Breakdown



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 3



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



Ship Type: Structure: Age: Note:



Bulk carrier Cargo Hold Side Shell Approx. 1% breakdown



General Breakdown



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 4



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Side Water Ballast Tk @ SSII Some edge and horizontal surface paint breakdown



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 5



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Tank has been repaired previously, breakdown at underside of corrugation – thinner film thickness



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Category Detail



% Breakdown



Overall Rating



EXAMPLE 6



Coating Condition



GOOD



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



GOOD close to FAIR Renewed anodes visible



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 7



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Underdeck Some hard scale at undersides of longitudinal edges Less than 10% breakdown



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 8



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Oil Tanker Side Water Ballast Tk Start of general ballast tank breakdown



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 9



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Oil Tanker Cargo Oil Tank Start of breakdown at underdeck area



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 10



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Chemical Tanker Aft Chemical Cargo Tk Some local breakdown greater than 20%. Repair would be recommended White areas are zinc metal primer



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 11



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Oil Tanker Cargo Tk Longl Bhd Spot rusting and horizontal weld stripe coat



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 12



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Aft Peak Tank FAIR close to POOR Coating colour change during drying – lighter



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 13



FAIR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Repair recommended as close to general breakdown



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 14



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Locally POOR with peeling and scale



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 15



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



Ship Type: Structure: Age: Note:



SSIII or SSIV General breakdown



General Breakdown



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 16



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Underdeck General breakdown of deck underside and longitudinals



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 17



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure Age: Note:



Side Water Ballast Tk Excessive diminution of structure Plate marked up for repair



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 18



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Excessive diminution of structure and scale



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Category Detail



% Breakdown



Overall Rating Coating Condition



EXAMPLE 19



POOR



Spot Rust



Light Rust



Edges



Weld



Hard Scale



General Breakdown



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Ship Type: Structure: Age: Note:



Excessive diminution of structure, cracking and buckling of longitudinal structure



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Annex A Inspection of Ballast Tanks Many defects are considered to be common and can be found on whichever ship type is being examined. Ballast tanks on all ship types will experience typical problems. These being: • Fractures and deformations • Corrosion • Fatigue fractures



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Deformations Deformation of structure is caused by in-plane load, out-of -plane load or combined loads. Often, deformation is described as being either local or global deformation. Local deformation will normally be limited to one panel including stiffeners, while global deformation will affect a larger structural area including plating, beam, frame, girder, floor, etc. If a large deformation is caused due to small increase of the load, the process is called buckling. Impact loads or contact, and inadvertent overloading, often cause deformations. Damage due to bottom slamming and wave impact forces are, in general, found in the forward part of the hull (see figure A.1), although stern seas (pooping) have resulted in damage in way of the after part of the hull. In the case of damage due to contact with other objects, you should pay special attention to the fact that although damage to the shell plating may look small from the outboard side, in many cases the internal members are heavily damaged (see figure A.2). Permanent buckling may arise as a result of overloading, overall reduction in thickness due to corrosion, or contact damage. Elastic buckling will not be directly obvious but may be detected by coating damage, stress lines or shedding of scale. Buckling damage is often found in webs of web frames (see figure A.3) or floors. In many cases this is due to corrosion of webs and/or floors, too wide a spacing of stiffeners, or wrongly positioned lightening holes, manholes or slots in webs and/or floors. It should be noted that inadvertent overloading might cause significant damage. In general, however, major causes of damage are associated with excessive diminution of the steel thickness and contact damage (see figure A.4).



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Fig. A.1 Damage to forward bottom plating



Fig. A.2 Major damage to fore end © Lloyd’s Register, 2004



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Fig. A.2a Internal view of a fore end damage



Fig. A.3 Buckle in side shell web frame © Lloyd’s Register, 2004



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Fig. A.4 Very severe consequence of improper loading Material wastage In addition to being familiar with typical structural defects likely to be encountered during an inspection, you need to be aware of the various forms and possible location of material wastage, or corrosion, that may occur to the decks, cargo spaces, ballast tanks and other structural areas. General corrosion appears as a non-protective, friable rust which can occur uniformly on hold or tank internal surfaces that are uncoated. The rust scale continually breaks off, exposing fresh metal to corrosive attack (see figure A.5). Thickness diminution cannot usually be judged visually until excessive diminution has occurred. In coated tanks and holds corrosion takes place as the coatings start to breakdown. Figure A.6 shows a typical example of knifing where the coating has broken © Lloyd’s Register, 2004



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down on the edge of a flange. Failure to remove mill scale (see figure A.7) during construction of the ship can accelerate corrosion experienced in service. Severe general corrosion in all types of ships, usually characterised by heavy scale accumulation, can lead to extensive steel renewals (see figure A.8). Grooving corrosion is often found in or beside welds, especially in the heat-affected zone. A galvanic current, generated from the difference of the metallographic structure between the heat-affected zone and base metal, causes the corrosion (see figure A.9). Coating of the welds is generally less effective compared to other areas, due to rough surfaces which exacerbates the corrosion. The grooving corrosion may lead to stress concentrations and further accelerate the corrosion. Grooving corrosion may be found in the base material where coating has been scratched or the metal itself has been mechanically damaged. Pitting corrosion is often found in the bottom plating of ballast tanks. If a place is liable to have corrosion due to local breakdown of coating, pitting corrosion starts. Once started, it is exacerbated by galvanic current between the pit and other metal (see figure A.10).



Erosion which is caused by the effect of liquid, and abrasion caused by mechanical effect, may also be responsible for material wastage (see figure A.11).



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Fig. A.5 General corrosion



Fig. A.6 Knifing on edge of a flange © Lloyd’s Register, 2004



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Fig. A.7 Failure to remove mill scale at new construction can lead to sever corrosion problems



Fig. A.8 Heavy scale © Lloyd’s Register, 2004



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Fig. A.9 Grooving corrosion occurs in parent material that has had it’s metallographic structure altered by the welding process.



Fig. A.9a Grooving in a fillet weld © Lloyd’s Register, 2004



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5% Scattered



10 % Scattered



15 % Scattered



20 % Scattered



25 % Scattered



Fig. A.10 Assessment tool for pitting © Lloyd’s Register, 2004



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Fig. A.10a Pits in plating can rapidly grow and deepen



Fig. A.11 Erosion in the vicinity of a ballast suction bell-mouth © Lloyd’s Register, 2004



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Annex B Hot Spots for Corrosion and Other Common Defects The following pages contain sketches indicating typical ship structures susceptible to corrosion and other common defects. In addition to hot spots, also look for evidence of general coating breakdown in: • Heeling and Flume tanks, • Areas of high vibration, especially on twin screw ships, • Panting region, especially on higher speed ships with fine hull forms. Particular locations susceptible to severe corrosion, depending on ship type, are: • Hot/cold interfaces where accelerated corrosion takes place such as common boundaries between topside or hopper tanks and bunker tanks, double bottom ballast tanks adjacent to fuel tanks and ballast tanks adjacent to heated cargo tanks in chemical/products tankers. • Breakdown in way of manual welds, especially at unit erection joints. • Breakdown of coatings in way of sounding pipe striking plates. • Ballast trunks connecting topside and hopper tanks, especially in the forward holds where the shell plating is liable to panting and vertical grooving occurs. • Engine Room structure, especially frames adjacent to salt water ballast pumps, sea chests, bilge wells and areas of high humidity.



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Fig. B.1 DECK PLATING Plating at hatch side and hatch corner



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Fig. B.2 TOPSIDE TANK Transverse primary web plating



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Fig. B.3 TOPSIDE TANK Intermediate bracket supporting side frames and hatch side bracket



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Fig. B.4 DECK AND SIDE LONGITUDINALS Longitudinal web plating and connection to transverse



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Fig. B.5 SIDE FRAMES Side frame end bracket connection to hopper tank



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Fig. B.6 HOPPER TANK Transverse web, longitudinal connection and hopper knuckle



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Fig. B.7 DOUBLE BOTTOM Double bottom floor and longitudinal connection



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Fig. B.8 DOUBLE BOTTOM Longitudinal girder and double bottom longitudinal



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Fig. B.9 TRANSVERSE BULKHEAD Vertically corrugated bulkhead



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Fig. B.10 TRANSVERSE BULKHEAD Connection of vertically corrugated bulkhead to lower stool



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Fig. B.11 TRANSVERSE BULKHEAD Lower stool



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Fig. B.12 AFT BULKHEAD Intersection of topside tank sloping plating with engine room bulkhead



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Annex C Nomenclature The following pages contain sketches indicating common nomenclature and terminology applied to typical structure of major ship types. A full glossary of useful terms relating to ship’s structures, coatings, corrosion, defects, inspections and surveys can be found in the Hull Planned Maintenance Scheme Training Course Distance Learning Program CD ROM to which this guide is a supplement. See also IACS Recommendation 82 – Surveyor’s Glossary, Hull Terms & Hull Survey Terms.



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Fig. C.1 DOUBLE HULL OIL TANKERS: Typical midship section nomenclature.



1



2



13



14



12



15



3



16 4 11 17



10



5 8



7



6



9



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Fig. C.1 DOUBLE HULL OIL TANKERS: Typical midship section nomenclature. KEY: 1. Deck transverse in centre cargo tank 2. Deck transverse in wing cargo tank 3. Transverse web frame in side ballast tank 4. Horizontal stringers in side ballast tank 5. Transverse web frame in hopper tank 6. Double bottom outboard girder 7. Double bottom floor 8. Double bottom centreline girder 9. Keel plate 10. Transverse web frame end bracket toe 11. Transverse web frame end brackets in centre cargo tank 12. Cross ties 13. Transverse wed frame radius face plate 14. Deck transverse end brackets in wing cargo tank 15. Deck transverse end bracket toe 16. Longitudinal bulkhead transverse web frame in centre cargo tank 17. Longitudinal bulkhead transverse web frame end brackets in wing cargo tank



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Fig. C.2 DOUBLE HULL OIL TANKERS: Typical midship section nomenclature.



1



2 3



17



4 18



16



5 6 19



15



7



20



14 8 9 12 13



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Fig. C.2 DOUBLE HULL OIL TANKERS: Typical midship section nomenclature. KEY: 1. Strength deck plating 2. Strength deck longitudinals 3. Deck stringer plate 4. Sheer strake 5. Side shell plating 6. Side shell longitudinals 7. Wing ballast tank 8. Bilge plating 9. Bilge keel 10. Double bottom outboard girder 11. Double bottom tank 12. Bottom shell longitudinals 13. Bottom shell plating 14. Inner bottom plating (tank top) 15. Inner bottom longitudinals 16. Longitudinal bulkhead longitudinals 17. Longitudinal bulkhead plating 18. Inner hull longitudinal bulkhead plating 19. Inner hull longitudinal bulkhead longitudinals 20. Hopper tank sloping plating



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Fig. C.3 DOUBLE HULL OIL TANKERS: Typical transverse bulkhead nomenclature.



1



2



3



4



5 6 7 8



10



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Fig. C.3 DOUBLE HULL OIL TANKERS: Typical transverse bulkhead nomenclature. KEY: 1. Strength deck plating 2. Transverse bulkhead plating in centre cargo tank 3. Transverse bulkhead plating in wing cargo tank 4. Transverse bulkhead horizontal stringers 5. Watertight transverse bulkhead plating in wing ballast tank 6. Side shell plating 7. Inner hull longitudinal bulkhead plating 8. Longitudinal bulkhead plating 9. Watertight double bottom floor in way of transverse bulkhead 10. Bottom shell plating



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Fig. C.4 DOUBLE HULL OIL TANKERS: Typical transverse bulkhead nomenclature.



1



12



11



2 3



4



10 5 9



6 7 8



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Fig. C.4 DOUBLE HULL OIL TANKERS: Typical transverse bulkhead nomenclature. KEY: 1. Strength deck plating 2. Strength deck longitudinals 3. Transverse bulkhead plating 4. Transverse bulkhead vertical stiffeners 5. Inner bottom plating (tank top) 6. Inner bottom longitudinals 7. Inner bottom longitudinal end brackets 8. Bottom shell longitudinals 9. Transverse bulkhead vertical stiffener end brackets 10. Transverse bulkhead horizontal stringers 11. Transverse bulkhead horizontal stringer tripping brackets 12. Transverse bulkhead vertical stiffener end brackets



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Fig. C.5 SINGLE SKIN BULK CARRIERS: Typical cargo hold structural configuration



2 1



9 8 7



6



3 5 4



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Fig. C.5 SINGLE SKIN BULK CARRIERS: Typical cargo hold structural configuration KEY: 1. Topside tank 2. Transverse bulkhead upper stool 3. Transverse bulkhead lower stool 4. Longitudinal/flat bar end connection 5. Double bottom tank 6. Hopper tank 7. Side shell frames 8. Side shell frame end brackets 9. Corrugated transverse bulkhead



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Fig. C.6 BULK CARRIERS: Nomenclature for typical transverse section in way of cargo hold.



22



1



2



3



21



20



4



19 18



5



17 4 14



16



13



12



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15



9



8



7



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Fig. C.6 BULK CARRIERS: Nomenclature for typical transverse section in way of cargo hold. KEY: 1. Strength deck plating 2. Strength deck longitudinals 3. Transverse web frame in topside tank 4. Side shell longitudinals 5. Side shell plating 6. Transverse web frame in hopper tank 7. Bilge plating 8. Bottom shell longitudinals 9. Bottom shell plating 10. Double bottom floor 11. Keel plate 12. Duct keel 13. Double bottom girders 14. Inner bottom plating (tank top) 15. Inner bottom longitudinals 16. Hopper tank sloping plating longitudinal 17. Hopper tank sloping plating 18. Side shell frames 19. Topside tank sloping plating longitudinal 20. Topside tank sloping plating 21. Topside tank longitudinal plating (hatch side girder) 22. Hatch side coaming



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Fig. C.7 BULK CARRIERS: Nomenclature for typical transverse bulkhead



1 2 9 3 8



4



5 6 7



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Fig. C.7 BULK CARRIERS: Nomenclature for typical transverse bulkhead KEY: 1. Hatch end coaming 2. Hatch end beam 3. Transverse bulkhead upper shelf plate 4. Corrugated transverse bulkhead plating 5. Shedder plate 6. Transverse bulkhead lower shelf plate 7. Inner bottom plating (tank top) 8. Cross-deck cantilever support bracket 9. Cross-deck beam



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Fig. C.8 CONTAINER SHIPS: Nomenclature for typical transverse section in way of cargo hold



3 1



2



4 5 6 7 8



26 9 10 11 12 13 25



24 23



14



22



17 21



19



18



15 16



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Fig. C.8 CONTAINER SHIPS: Nomenclature for typical transverse section in way of cargo hold KEY: 1. Inboard continuous hatch side coaming and girder (if fitted) 2. Continuous hatch side coaming 3. Hatch coaming transverse brackets (stay brackets) 4. Strength deck plating 5. Strength deck longitudinals 6. Sheer strake 7. Side shell plating 8. Transverse web frame in side ballast tank 9. Side shell longitudinals 10. Horizontal stringers in side ballast tank 11. Inner hull longitudinal bulkhead plating 12. Transverse web frame horizontal stiffener in side ballast tank 13. Transverse web frame horizontal stiffener end brackets 14. Bilge longitudinals 15. Bilge keel 16. Bilge plating 17. Double bottom floor 18. Double bottom floor vertical stiffeners 19. Bottom shell plating 20. Bottom shell longitudinals 21. Inner bottom longitudinals 22. Double bottom girders 23. Keel plate 24. Double bottom centreline girder 25. Inner bottom plating (tank top) 26. Transverse bulkhead vertical webs © Lloyd’s Register, 2004



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Fig. C.9 CONTAINER SHIPS: Nomenclature for typical sections through forward cargo regions.



1 2



4



3 3 3



5



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Fig. C.9 CONTAINER SHIPS: Nomenclature for typical sections through forward cargo regions. KEY: 1. Cross-deck strip 2. Passageway 3. Transverse bulkhead horizontal stringers 4. Transverse bulkhead vertical webs 5. Transverse bulkhead plating



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Fig. C.10 CONTAINER SHIPS: Nomenclature for typical structural members in cargo region



2



3



4



5



1 10



14 11 12



13 6 7 9



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Fig. C.10 CONTAINER SHIPS: Nomenclature for typical structural members in cargo region KEY: 1. Hatch corner deck insert plate 2. Hatch coaming transverse brackets (stay brackets) 3. Hatch end coaming 4. Continuous hatch side coaming 5. Cross-deck strip 6. Transverse bulkhead vertical stiffeners 7. Double bottom girders 8. Bottom shell longitudinals 9. Inner bottom longitudinals 10. Inboard continuous hatch side coaming and girder (if fitted) 11. Hatch end beam 12. Transverse bulkhead horizontal stringers 13. Inner bottom plating (tank top) 14. 40 foot containers (FEU)



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Fig. C.11 CONTAINER SHIPS: Nomenclature for typical watertight and non-watertight transverse bulkheads.



7



6 1 5



2



3 4



A B



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Fig. C.11 CONTAINER SHIPS: Nomenclature for typical watertight and non-watertight transverse bulkheads. KEY: A 1. 2.



Non-watertight transverse bulkhead (mid-hold support) Transverse bulkhead vertical webs Transverse bulkhead horizontal stringers



B 3. 4. 5. 6. 7.



Watertight transverse bulkhead Transverse bulkhead vertical stiffeners Double bottom floor Transverse web frame in side ballast tank Transverse bulkhead vertical webs Hatch coaming transverse brackets (stay brackets)



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Annex D Coating Condition Assessment Report The following pages contain copies of a Coating Condition Assessment Report based on the proposed IACS assessment methodology. Complete these report forms using a soft pencil or water based ink pen. This guide is printed on waterproof plasticized paper and therefore your entries can be easily removed using an eraser or damp cloth without damaging the paper.



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NOTES:



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NOTES:



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