View
223
Download
1
Category
Tags:
Preview:
Citation preview
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
1
INTERTANKO
UK Corrosion 2002 – Cardiff, Wales October 24, 2002
CRUDE OIL CARGO TANK CORROSION
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
2
Purpose of this paperProvide 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 –
INTERTANKO 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.
INTERTANKO 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.
INTERTANKO 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
6
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
INTERTANKO 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
8
THENAMARIS -Suez max tanker
Notice the red coat on cargo tank inner bottom
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
13
Pitting as discovered on new double hull tankers (MIC)
INTERTANKO 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
INTERTANKO 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
INTERTANKO 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
INTERTANKO 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
18
Castor – main deck crackDecember 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
19
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!
CARRY OUT SURVEYS AND REPAIRS AS INTENDED!
NOTHING MORE – NOTHING LESS!
INTERTANKO 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!
INTERTANKO 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.
INTERTANKO 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
INTERTANKO 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
INTERTANKO 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
26
Probability of crack detection (source: DNV)
Probability of detection of cracks in ship hulls (Visual inspection)
0,01
0,1
1
10
100
0,1 1 10 100
Crack Size [cm]
Pro
bab
ilit
y o
f D
etec
tio
n,
%PROBABILITY OF DETECTION OF CRACKS
INTERTANKO 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
INTERTANKO 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.
INTERTANKO 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
INTERTANKO 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
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
32
THENAMARIS – ATHENSMEANS OF ACCESS
WALKWAY FOR INSPECTION IN BALLAST TANK
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
33
THENAMARIS – ATHENS
Walkway in ballast tank using oversized longitudinal fitted with railing
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
34
THENAMARIS – ATHENS
Coated cargo tank inner bottom to prevent MIC corrosion
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
35
THENAMARIS/ ATHENS
Coating of tank head – ullage space
Note access platform with railing for inspection
coated
Dark area – coated to prevent ullage space corrosion
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
36
THENAMARIS - ATHENS
CARGO TANK HEAD INSPECTION ACCESS PLATFORM
COATEDCARGO TANK TOP (DARK AREA)
INTERTANKO UK Corrosion 2002 Cardiff 22-24 October 2002
37
VLCC cargo tank walkway
Notice oversized longitudinals as access walkway for inspection and the walk way platforms around the web frames
Oversized longitudinals
Walk way
INTERTANKO 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.
INTERTANKO 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.
INTERTANKO 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.
INTERTANKO 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.
INTERTANKO 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
Recommended