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Classification Alert: Mooring, Ship Design MBL and Direct Mooring Analysis (IACS Rec 10).

Class News 19/2021.

09 November 2021 

Applicability:  shipowners, technical managers, operators, designers and shipbuilders.

The International Association of Classification Societies (IACS) has revised Recommendation 10 on Chain Anchoring, Mooring and Towing Equipment. These revised recommendations in Rec 10 (Rev 4), September 2020 will apply to ships contracted for construction from 1 January 2022.

Accordingly, the following Lloyds’s Register (LR) Rule sets will be updated and come into effect on 1 January 2022: 

  • Rules and Regulations for the Classification of Ships.
  • Rules and Regulations for the Classification of Naval Ships.(Although not mandatory for naval vessels, these updates are included to promote safe mooring and towing operations).

Significant mooring changes

The updates in IACS Rec 10 (Rev 4) include significant changes to mooring recommendations as summarised below:

  • A design parameter ‘Ship design minimum breaking load’ – i.e. MBLSD – is being introduced for the selection of mooring lines, mooring fittings and their supporting structure. The same applies to towline and towing fittings.
  • The procedure to carry out  direct mooring analysis is now included in the appendix to Rec 10  i.e “Appendix A Direct mooring analyses”.

Impact on ship design

As an alternative to the conventional prescriptive mooring line recommendations, optimised mooring line recommendations can now be calculated through direct mooring analysis in accordance with the procedure given in Appendix A of IACS Recommendation 10 ‘Chain Anchoring, Mooring and Towing Equipment’. 

What to do now

​​​​Owners, technical managers, operators, designers and shipbuilders need to be aware that these updated recommendations are applicable to ships contracted for construction on or after 1 January 2022.

It is proposed that the Rule amendment notices for both LR Ship Rules and LR Naval Ship Rules will be issued in the month of November 2021 with effect from 1 January 2022. The amendment notices, when published, can be referred to for further details on the LR website:

The revised IACS Recommendation 10 and its technical background is publicly available for reference on the IACS website.

Further information

For further information, please get in touch with UKITSO-Ship Structures SST@lr.org

Click here to download a PDF copy of 19/2021 Class News.