Differences in technology qualification for mooring ropes with Anti Snap-Back features
Many types of certificates are associated with mooring ropes, and it can be difficult to understand the differences between a statement of qualified technology and other certificates.
We provide a brief description of the main types of certificates and explain why not all of them guarantee the performance and reliability of an anti-snap back feature.
Statement of qualified technology
In November 2022, DNV awarded Wilhelmsen Ships Service with a statement of qualified technology for the Timm’s Snap Back Arrestor (SBA™). We are the first and only manufacturer to receive such a qualification from DNV for an anti-snap back rope.
The statement of qualified technology is issued following an extensive qualification process, performed in accordance with DNV’s recommended practice A203. The process provides a systematic approach to identify and verify all possible threats and failure modes of the technology being qualified.
For the Timm Snap Back Arrestor, it shows that the performance of the SBA has been verified in the most severe scenarios and in operational conditions onboard vessels, thus demonstrating the robustness and reliability of the technology. The qualification of the SBA took over 4 years of planning, testing and analysis. It did not focus on performance alone but also looked at the reliability of the technology in real-life use as a system with other elements of the mooring arrangement.
This process also includes verification of ropes returned from service and feedback from cases of ropes snapping. Further feedback from field experience will be used to prove the maturity of the technology.
Type approval certificate
Type approval is a procedure for the approval of the product in compliance with relevant industry standards. The design of the product is assessed once, and the approval is then valid for all products of the same design, within a defined range.
Type approval certificates for ropes cover the performance and the manufacturing of the rope itself but it does not verify the performance of any anti snap back element.
Certificate of conformity/Mill test certificate
The manufacturer typically issues a certificate of conformity (CoC) or mill to confirm that the product meets the performance requirements stated in the product specification. It can also refer to specific international standards.
These certificates sometimes also include results of internal testing, demonstrating the product’s performance, but these tests are typically not verified by a 3rd party.
The conformity of the product is declared by the manufacturer, usually with reference to requirements defined by the manufacturer, but this does not guarantee that the technology was qualified through a rigorous process.
Verification statement (Third party witnessing certificate)
These documents confirm that a surveyor from a class society has witnessed the product test in line with specific standards that are listed in the statement. This verification also typically includes the review and approval of the relevant test reports.
When it comes to anti-snap back ropes, the performance of the anti-snap back can be verified by a third party and documented in a verification statement. However, this will only cover the performance of a unique rope or batch of ropes within the limitations of a test facility.
Mooring line certificate (MEG4 certificate)
OCIMF introduced the mooring line certificate in the fourth edition of its Mooring Equipment Guidelines.
The manufacturer completes the mooring line certificate for each mooring line or tail supplied. In addition, the certificate summarizes the performance and design of the actual mooring line or tail provided, the performance indicators, and other supporting documentation and information for the design range.
The performance indicators refer to the results of the specific tests defined in OCIMF MEG4. However, no test in MEG4 currently relates to the performance of any anti snap back element; hence the indicators only refer to the rope itself.
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