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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

INTERTANKOUK Corrosion 2002 – Cardiff, Wales October 24, 2002

CRUDE OIL CARGO TANK CORROSION

UK Corrosion 2002 Cardiff 22-24 October 2002

purpose of this paper
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

intertanko
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

intertanko1
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

intertanko2
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

vlcc typical midship section
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

vlcc double hull
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

thenamaris suez max tanker
THENAMARIS -Suez max tanker

Notice the red coat on cargo tank inner bottom

UK Corrosion 2002 Cardiff 22-24 October 2002

corrosion mechanisms at work
Corrosion mechanisms at work

UK Corrosion 2002 Cardiff 22-24 October 2002

volatile stable crude oil
Volatile/stable crude oil

UK Corrosion 2002 Cardiff 22-24 October 2002

day night
Day/Night

UK Corrosion 2002 Cardiff 22-24 October 2002

pitting in the tank bottom plate mic
Pitting in the tank bottom plate(MIC)

UK Corrosion 2002 Cardiff 22-24 October 2002

pitting as discovered on new double hull tankers mic
Pitting as discovered on new double hull tankers (MIC)

UK Corrosion 2002 Cardiff 22-24 October 2002

one coat on tank bottom
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

rust flake from above under deck corrosion
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

sulphur crystals
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

erika december 1999
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

castor main deck crack
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

so what can be done
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

what else can be done
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

stress analysis
Stress analysis

UK Corrosion 2002 Cardiff 22-24 October 2002

areas vulnerable to corrosion
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

no access
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

practical logistical problems
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

wing cargo tank on a small single hull vlcc source dnv
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

probability of crack detection source dnv
Probability of crack detection (source: DNV)

UK Corrosion 2002 Cardiff 22-24 October 2002

cargo tank top bottom coating
Cargo tank top/bottom coating

UK Corrosion 2002 Cardiff 22-24 October 2002

measuring method
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

thickness measurement ships bottom plating
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

slide30

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

thenamaris new suez max tanker during construction 2000
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

thenamaris athens means of access
THENAMARIS – ATHENSMEANS OF ACCESS

WALKWAY FOR INSPECTION IN BALLAST TANK

UK Corrosion 2002 Cardiff 22-24 October 2002

thenamaris athens walkway in ballast tank using oversized longitudinal fitted with railing
THENAMARIS – ATHENSWalkway in ballast tank using oversized longitudinal fitted with railing

UK Corrosion 2002 Cardiff 22-24 October 2002

thenamaris athens coated cargo tank inner bottom to prevent mic corrosion
THENAMARIS – ATHENSCoated cargo tank inner bottom to prevent MIC corrosion

UK Corrosion 2002 Cardiff 22-24 October 2002

thenamaris athens coating of tank head ullage space
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

thenamaris athens cargo tank head inspection access platform
THENAMARIS - ATHENSCARGO TANK HEAD INSPECTION ACCESS PLATFORM

COATED

CARGO TANK TOP (DARK AREA)

UK Corrosion 2002 Cardiff 22-24 October 2002

vlcc cargo tank walkway
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

conclusions 1 5
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

conclusion 2 5
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

conclusion 3 5
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

conclusions 4 5
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

conclusions 5 5
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