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INTERTANKO UK Corrosion 2002 – Cardiff, Wales October 24, 2002

INTERTANKO UK Corrosion 2002 – Cardiff, Wales October 24, 2002. CRUDE OIL CARGO TANK CORROSION. Purpose of this paper. Provide a brief background about: Tanker structures and the cargo tank environment Tanker corrosion INTERTANKO’s Corrosion conference 1998 - Update since 1998

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INTERTANKO UK Corrosion 2002 – Cardiff, Wales October 24, 2002

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  1. INTERTANKOUK Corrosion 2002 – Cardiff, Wales October 24, 2002 CRUDE OIL CARGO TANK CORROSION UK Corrosion 2002 Cardiff 22-24 October 2002

  2. Purpose of this paper Provide a brief background about: • Tanker structures and the cargo tank environment • Tanker corrosion • INTERTANKO’s Corrosion conference 1998 - Update since 1998 • Conclusions – way ahead – coating – access – class rule harmonization – UK Corrosion 2002 Cardiff 22-24 October 2002

  3. INTERTANKO INTERTANKO • The International Association of Independent Tanker Owners. • INTERTANKO membership represents about 2000 tankers. • Chemical, Product and Crude Oil tankers. • Offices in Oslo, London, Washington D.C and Singapore. • Regional Panels in Americas, the Far East and Greece. UK Corrosion 2002 Cardiff 22-24 October 2002

  4. INTERTANKO Examples of INTERTANKO activities: • Cooperates with other organisations like OCIMF – ICS – WWF – IACS and numerous others. • Active in IMO. • Providing factual information. • Commenting and working group participation. • Active with US Coast Guard. • Commenting on proposed rulemaking. UK Corrosion 2002 Cardiff 22-24 October 2002

  5. INTERTANKO • Keep members advised of political developments and proposed regulatory changes and other issues of general interest – like corrosion. • Tanker events – every 6th month • Membership criteria – quality • Visit Intertanko home page on: www.intertanko.com UK Corrosion 2002 Cardiff 22-24 October 2002

  6. Midship section Approximate Dimensions (in meter): Length over all: 332 Length B. P.: 320 Breadth moulded: 58 Depth moulded: 31 Design draft: 20.8 Scantling draft: 22.0 VLCC - Typical midship section UK Corrosion 2002 Cardiff 22-24 October 2002

  7. VLCC – Double hull • Double hull tanker in the building dock • Side ballast tank width abt. 2 – 4 meter. • Bottom ballast tank height abt. 2 - 3 meter. • Height of centre cargo tank abt. 29 meter • Length of centre cargo tank abt. 50 meter UK Corrosion 2002 Cardiff 22-24 October 2002

  8. THENAMARIS -Suez max tanker Notice the red coat on cargo tank inner bottom UK Corrosion 2002 Cardiff 22-24 October 2002

  9. Corrosion mechanisms at work UK Corrosion 2002 Cardiff 22-24 October 2002

  10. Volatile/stable crude oil UK Corrosion 2002 Cardiff 22-24 October 2002

  11. Day/Night UK Corrosion 2002 Cardiff 22-24 October 2002

  12. Pitting in the tank bottom plate(MIC) UK Corrosion 2002 Cardiff 22-24 October 2002

  13. Pitting as discovered on new double hull tankers (MIC) UK Corrosion 2002 Cardiff 22-24 October 2002

  14. ONE COAT ON TANK BOTTOM COATING APPLIED ON PITTING CORROSION IN PERFECT CONDITION 5 YEARS LATER NO FURTHER PROBLEM EXPECTED UK Corrosion 2002 Cardiff 22-24 October 2002

  15. RUST FLAKE FROM ABOVE – UNDER DECK CORROSION! RUST FLAKE COMMONLY FOUND ON CARGO TANK BOTTOM SOURCE; UNDER DECK CORROSION UK Corrosion 2002 Cardiff 22-24 October 2002

  16. Sulphur crystals FULLY FORMED SULPHUR CRYSTALS FOUND ON THE RUST FLAKES FROM THE UNDER DECK AREA OF THE CARGO TANKS UK Corrosion 2002 Cardiff 22-24 October 2002

  17. ERIKA - December 1999 • MAIN INGREDIENTS – OLD TANKER – CORROSION –BAD WEATHER – DISTRESS -SINKING – POLLUTION – ALL HANDS SAVED • SIGNIFICANT CONSEQUENCES OF ONE TANKER ACCIDENT ACROSS THE INDUSTRY; • TWO TRENCHES OF MARITIME LEGISLATION KNOWN AS ; • ERIKA I AND ERIKA II UK Corrosion 2002 Cardiff 22-24 October 2002

  18. Castor – main deck crack • December 2000;Part of crack • Mediterranean – bad weather • Fully loaded tanker – Castor developed a 22 meter long crack in the main deck • Coastal states refuse port of refuge • Castor survives – no cargo spilled – minor regulatory effect • Main ingredients – corrosion – bad weather – inadequate surveys and maintenance UK Corrosion 2002 Cardiff 22-24 October 2002

  19. More inspections and more surveys….!? The answer is a clear NO! There is more than adequate survey regulations in force. If the present survey regimes are followed, that is! So, what can be done? CARRY OUT SURVEYS AND REPAIRS AS INTENDED! NOTHING MORE – NOTHING LESS! UK Corrosion 2002 Cardiff 22-24 October 2002

  20. What else can be done? • Identify risk areas at the design stage • Arrange access at newbuilding stage • Apply suitable coating to areas of concern like all cargo tank tops and inner bottoms • Produce inspection manual • THESE COUNTERMEASURES MUST BE COMPULSORY MEASURES – EXEMPT FROM COMMERCIAL PRESSURE! UK Corrosion 2002 Cardiff 22-24 October 2002

  21. Stress analysis UK Corrosion 2002 Cardiff 22-24 October 2002

  22. AREAS VULNERABLE TO CORROSION These are the areas in a tanker that are likely to suffer corrosion during its service life. Well known! But no permanent access. UK Corrosion 2002 Cardiff 22-24 October 2002

  23. No access • Arrows indicate where access is necessary for meaningful close up inspection. • Notice no access arrangement • Tank inner bottom not coated UK Corrosion 2002 Cardiff 22-24 October 2002

  24. Practical logistical problems! 100% survey of a VLCC would require: Height to climb 11 km Area to survey 300 000 m2 Length of weld 1 200 km Length longitudinals 58 km Bottom area 10 700 m2 1,0 % pitting 85 000 pits UK Corrosion 2002 Cardiff 22-24 October 2002

  25. Wing cargo tank on a small single hull VLCC (Source DNV) • Note the surveyor in the tank bottom • Volume of tank abt. 25.000 cubic meter • Notice no access – no railings on stringers UK Corrosion 2002 Cardiff 22-24 October 2002

  26. Probability of crack detection (source: DNV) UK Corrosion 2002 Cardiff 22-24 October 2002

  27. Cargo tank top/bottom coating UK Corrosion 2002 Cardiff 22-24 October 2002

  28. MEASURING METHOD Hull plate thickness can be measured with the ship afloat. A vehicle with special instrumentation will crawl along the bottom UK Corrosion 2002 Cardiff 22-24 October 2002

  29. THICKNESS MEASUREMENT SHIPS BOTTOM PLATING THE COLOR DIAGRAM SHOWS THE IN-WATER BOTTOM PLATING THICKNESS MEASUREMENT RESULT. THE RED AREA NEEDS ATTENTION. THE YELLOW NEEDS WATCHING. UK Corrosion 2002 Cardiff 22-24 October 2002

  30. Building blocksBLOCK SIZE IS IMPORTANT TO REDUCE THE AMOUNT OF PAINT REPAIRS – WHEN THE BALLAST CARGO TANKS ARE COATED AT THE BLOCK STAGE. BLOCK WELDS - EXTERNAL UK Corrosion 2002 Cardiff 22-24 October 2002

  31. THENAMARIS - New Suez max tanker during construction 2000 LAST SECTION OF MAINDECK WILL CLOSE THE DECK NOTICE THE BULKHEAD PLATFORM UK Corrosion 2002 Cardiff 22-24 October 2002

  32. THENAMARIS – ATHENSMEANS OF ACCESS WALKWAY FOR INSPECTION IN BALLAST TANK UK Corrosion 2002 Cardiff 22-24 October 2002

  33. THENAMARIS – ATHENSWalkway in ballast tank using oversized longitudinal fitted with railing UK Corrosion 2002 Cardiff 22-24 October 2002

  34. THENAMARIS – ATHENSCoated cargo tank inner bottom to prevent MIC corrosion UK Corrosion 2002 Cardiff 22-24 October 2002

  35. THENAMARIS/ ATHENSCoating of tank head – ullage space Dark area – coated to prevent ullage space corrosion Note access platform with railing for inspection coated UK Corrosion 2002 Cardiff 22-24 October 2002

  36. THENAMARIS - ATHENSCARGO TANK HEAD INSPECTION ACCESS PLATFORM COATED CARGO TANK TOP (DARK AREA) UK Corrosion 2002 Cardiff 22-24 October 2002

  37. VLCC cargo tank walkway Walk way Oversized longitudinals Notice oversized longitudinals as access walkway for inspection and the walk way platforms around the web frames UK Corrosion 2002 Cardiff 22-24 October 2002

  38. CONCLUSIONS (1/5) • CORROSION CAN BE DUBBED MANY NAMES – BUT NAME CHANGE IS NO SUBSTITUTE FOR INSPECTION, DISCOVERY AND REPAIRS. • CORROSION RISK CAN BE PREDICTED, LOCATION IDENTIFIED AT DESIGN STAGE, PERMANENT ACCESS ARRANGED FOR MONITORING IN SERVICE. • CORROSION, CRACKS AND BUCKLING CAN BE DISCOVERED – ACCESS FOR CLOSE-UP INSPECTION IS NEEDED. UK Corrosion 2002 Cardiff 22-24 October 2002

  39. CONCLUSION (2/5) • MODIFY LONGITUDINALS ON NEW SHIPS TO BE USED AS ACCESS PLATFORMS. • OWNERS MUST DEMAND THAT – CLASS MAKE PERMANENT ACCESS REQUIREMENT COMPULSORY AND HARMONIZED FOR ALL CLASS SOCIETIES. • COATING MUST BE APPLIED TO CARGO TANK TOP & INNER BOTTOM AS COMPULSORY IACS COUNTERMEASURE AGAINST CORROSION. UK Corrosion 2002 Cardiff 22-24 October 2002

  40. CONCLUSION (3/5) • NEGATIVE TOLERANCE ON STEEL PLATE THICKNESS MUST STOP – POSITIVE TOLERANCE ONLY ACCEPTABLE. • SHIPBUILDERS MUST EXTEND HULL STRUCTURE AND COATING GUARANTEE FROM ONE TO FIVE CALENDAR YEARS TO MATCH THE FIRST SPECIAL SURVEY. • GUARANTEE LENGTH IS A SAFETY MATTER – NOT A COMMERCIAL ISSUE. UK Corrosion 2002 Cardiff 22-24 October 2002

  41. CONCLUSIONS (4/5) • SHIP REPAIRERS MUST REPAIR SHIPS IN A RESPONSIBLE AND PROFESSIONAL MANNER – SHIP REPAIRERS SHOULD BE HELD LIABLE FOR INADEQUATE REPAIRS. • OWNERS, CLASS AND THE INDUSTRY HAVE COMMON INTEREST IN NEVER AGAIN SEEING A TANKER OR ANY SHIP GOING DOWN AND SPILL HER CARGO BECAUSE OF CORROSION AND LESS THAN SATISFACTORY REPAIRS. UK Corrosion 2002 Cardiff 22-24 October 2002

  42. CONCLUSIONS (5/5) • ALL CLASS SOCIETIES’ GOVERNING BODIES HAVE SIGNIFICANT NUMBERS OF SENIOR EXECUTIVES FROM SHIP OWNING, SHIP OPERATING INTERESTS. • THESE SENIOR EXECUTIVES HAVE A PARTICULAR DUTY TO TAKE THE LEAD, BE PROACTIVE AND ENSURE CLASS/IACS SPEED UP THE PROCESS OF; • UNIFORM SCANTLING REQUIREMENTS • UNIFORM FATIGUE CALCULATIONS • GENERAL HARMONISATION OF CLASS RULES • INSPECTION ACCESS AND COATING FOR CARGO TANKS UK Corrosion 2002 Cardiff 22-24 October 2002

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