ALERT Assessment of Life-Cycle Effects of Repairs on Tankers 1
ALERT Project Overview Coordinated Action funded by European Commission A two year project Started 1st. November 2006 This is an interim report on progress to date Programme evolved from the recommendations in the report on the loss of the Prestige It will examine the cumulative effect of repairing a tanker throughout its life, looking for present best industry practice and ways in which that practice can be improved IMO, Copenhagen, 8th October 2007 2
ALERT Partners IMO Secretariat - observer Funding provided by the European Commission 6 th Framework Programme IMO, Copenhagen, 8th October 2007 3
ALERT Project Overview What is the effect of joining new steel to old Overview steel? WP1 What additional stresses are put into a ship’s WP2 structure during a repair? WP3 How is fatigue in a structure affected when WP4 part of the structure is replaced? WP5 How do the effects of repairs change during a Conclusions ship’s life? Could detection of defects be improved? How can any possible adverse effects of repairs be detected and minimised? How effective are current best practices? IMO, Copenhagen, 8th October 2007 4
ALERT Project Overview This Project is a preliminary exercise, it will Overview not be doing fundamental research. WP1 The intention is to identify: WP2 • Current best practice and WP3 WP4 • Areas in which in-depth work is required. WP5 Conclusions IMO, Copenhagen, 8th October 2007 5
ALERT Project Overview 5 Work Packages: Overview WP1 Ship repair practices 1. WP2 Condition monitoring of ships WP3 2. WP4 Structural assessment methods 3. WP5 Through life management 4. Conclusions Integration, dissemination and 5. exploitation IMO, Copenhagen, 8th October 2007 6
WP1: Ship Repair Practices 7
Work package 1 overview Objective of this work package is to critically Overview review the current knowledge and understanding, WP1 and identify future research and development needs in the following areas: WP2 WP3 Standard practices and class society requirements for the repair of ships WP4 Alternative repair practices WP5 Conclusions Consequences on structural reliability of new to old steel replacement, and Development and implications of common repair, inspection and maintenance procedures, requirements and acceptance by the classification societies. IMO, Copenhagen, 8th October 2007 8
WP1 Task overview Overview WP1 Task 1-1 Standard practices, Class WP2 Society requirements for the repair of WP3 ships and alternative repair practices WP4 Task 1-2 Consequences on structural WP5 reliability of new to old steel Conclusions replacement Task 1-3 Development of common repair, inspection and maintenance IMO, Copenhagen, 8th October 2007 9
Relationships in ship repair Flag States Ship owners Overview and operators WP1 WP2 WP3 WP4 Ship repairers WP5 Ship Repair Conclusions Consultant Services and NDT Contractors International, national and industry standards IMO, Copenhagen, 8th October 2007 10
Recent developments IACS progress Overview Recommendation 96 (April 2007) WP1 Experience feedback WP2 With modern computing it is possible to collect WP3 more and more data. WP4 Databases have been developed in classification but will take some years to mature WP5 Condition assessment and monitoring Conclusions development Class societies are working to develop better and faster ways to quickly analyse a ships condition so it will be possible to make a more informed decision on the appropriateness of a repair. IMO, Copenhagen, 8th October 2007 11
Analysing the reliability of repairs Correlation between survey and Overview WP1 incident data could be improved WP2 Anecdotal evidence confirms that WP3 repairs do fail – but it is not known at WP4 what frequency WP5 Conclusions IMO, Copenhagen, 8th October 2007 12
Conclusions There are developments in ship repair Overview knowledge and guidelines, for example WP1 IACS recommendation 96, new data WP2 collection programs WP3 It is important to establish reliable data WP4 collection systems WP5 The ship repair industry is a multi- Conclusions stakeholder affair It is important that we continue to develop best practice guidelines and regulations through cooperation IMO, Copenhagen, 8th October 2007 13
WP2: Condition Monitoring of Ships Task 2.1 Non-Destructive testing of welds Task 2.2 Detection and recording of fatigue cracks Task 2.3 Corrosion detection and protection 14
Non – Destructive Testing of welds Detectability of welding defects depends on: Overview WP1 -Methods applied WP2 -Capability of the NDT-operator WP3 -Extent of examination. WP4 Requirement for non destructive testing of WP5 Repairs are determined on a case by case basis. Conclusions Not all specified techniques have adequate POD (Probability of Detection) characteristics IMO, Copenhagen, 8th October 2007 15
Non-Destructive Testing of welds The capability of the NDT-operator could Overview be improved by adding specific knowledge WP1 WP2 of ships structures. WP3 The extent of examination and selection of WP4 area’s is verified by the Class surveyor on WP5 the basis of the NDT program submitted by Conclusions the ship repairs yard The intensity of testing and locations tested influences the number of defect detected. IMO, Copenhagen, 8th October 2007 16
Detection and recording of fatigue cracks Visual inspections is the most Overview WP1 economical method for the inspection WP2 of large tanker structures. WP3 More advanced testing methods have WP4 better POD characteristics. WP5 Conclusions The development of better POD curves requires more extensive test data than is available at present. IMO, Copenhagen, 8th October 2007 17
Detection and recording of fatigue cracks The detection of cracks by visual Overview means will be improved by: WP1 WP2 - Prior knowledge of area’s with stress WP3 concentrations WP4 -Historical information of fracture WP5 damages in similar structures. Conclusions - Adequate lighting conditions with clean and safe access IMO, Copenhagen, 8th October 2007 18
Corrosion detection, protection... Tanker corrosion is not new Overview WP1 Tested & tried coating systems are WP2 available WP3 Industry guidelines are available WP4 Sufficient in-service inspection WP5 requirements inplace Conclusions Steel replacement quality standard – not compulsory Market forces – OCIMF members IMO, Copenhagen, 8th October 2007 19
Corrosion detection, protection... Steel replacement guidelines, coating of Overview replaced steel & repair guarantee WP1 WP2 CTF – tank coating maintenance file & WP3 access platforms - CSR WP4 How to reduce need for steel replacement: WP5 Specification & coating newbuild stage Conclusions Supervision during construction Shipbuilder’s guarantee for structure and coating – one (1) year IMO, Copenhagen, 8th October 2007 20
Corrosion detection, protection... How to reduce.......... (cont.): Overview WP1 Shipbuilder’s guarantee for structure and WP2 coating – one (1) year WP3 Feedback to shipbuilder – one (1) year WP4 Extend ship builders hull structure and WP5 coating guarantee to first renewal survey Conclusions – 5th year anniversary Information / experience sharing Environmental impact of steel replacement IMO, Copenhagen, 8th October 2007 21
Corrosion detection, protection... Quality seesaw – ”it is the economy Overview WP1 stupid!” (Bill Clinton) WP2 Regulation Experience Hull structure WP3 Specification Performane Tank coating WP4 Knowledge Quality systems Workmanship WP5 Research LIFE CYCLE (1) One year guarantee COST + .....? Conclusions € - £ - ¥ - $ Five(5) year builders guarantee Market, OCIMF – SIRE etc IMO, Copenhagen, 8th October 2007 22
WP3: Structural Assessment Methods 23
Global Strength Assessment Methods Methods used for assessment of new- Overview WP1 build ships include: WP2 Empirical and Analytical Methods WP3 Section Modulus based approaches WP4 2-D Progressive Collapse methods WP5 Numerical Analysis methods Conclusions Finite Element Analysis Idealised Structural Unit Method (ISUM) Can these methods consider effects of repair? IMO, Copenhagen, 8th October 2007 24
Global Strength Assessment Methods Repairs can be considered by: Overview WP1 Increase in Section Modulus WP2 Modification to: WP3 Material thicknesses WP4 Deformations – both weld induced and WP5 misalignments Conclusions Residual Stresses Some methods for assessing Global Strength are able to consider more effects than others IMO, Copenhagen, 8th October 2007 25
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