DNV GL Rules - January 2021 edition

The 2021 January edition of the DNV GL rules is now available.

The 2021 January edition of the DNV GL rules is now available on our Rules and Standards page.

1. General information

New and amended rules were formally approved on January 14th 2021 by Group CEO Remi Eriksen and are included in the January 2021 publication of the rules.  

The main changes to the rules cover:

  1. Rules for Ships:
    a) Revised class notation
    b) General updates and corrections
  2. Yachts - new class notations

The entry into force date for these rules is 1st of July 2021.   The rules may, however, be applied to projects contracted before this date upon agreement between parties.

For more information on the changes, please contact your local DNV GL office. 

Below is given a general overview of the main changes in the rules for classification of ships and the rules for classification of yachts.

2. Rules for Ships

Main class

Topic    Rule reference
Type of change

Materials and welding
Fabrication and testing

Pt.2 Ch.4 Sec.7Topic revison
NDT methods

Class notations

Class notationRule reference
Type of change


Pt.5 Ch.10 Sec.10Topic revision
Propeller loads
Tugs and escort vesselsPt.5 Ch.10 Sec.11Topic revision 
Towing winch emergency
release systems
Double acting vesselsPt.6 Ch.6 Sec.7Topic revision
Propeller loads

Updates commented

a) Materials and welding

  • IACS documents related to NDT have been updated, extended and put to a higher level. The new IACS requirements UR W33 and W34 complete a consistent overall picture of NDT requirements in the maritime industry.
  • Rules update in relation to IACS UR W33
    • added table for delay time requirements based on the strength levels of the materials
    • revised minimum parent material thickness requirement
    • aligned standards, abbreviations, quality levels and acceptance criteria.
  • Rules update in relation to IACS UR W34
    • Included definition of ANDT (advanced NDT) methods, standards, abbreviations, acceptance criteria
    • added qualification procedure for ANDT methods.

b) Icebreaker

  • The propeller loads for open propellers and ice pressure for structural loads have been reduced to meet actual operating conditions.

c) Tugs and escort vessels

  • Implemented IACS resolution UR M79 (rev1 Feb 2020) regarding towing winch emergency release systems.
  • Aligned with definitions for ‘black out condition’ and ‘safe location’.
  • New documentation requirement for test procedure for quay and sea trials for emergency release systems for all types of tugs.

d) Double acting vessels

  • Following changes to rules for Icebreakers, the backward blade force factor for DAV with icebreaker notation has been decreased from 1.2 to 1.1 accordingly.

3. Rules for Yachts

Class notation

Class notationRule reference
Type of change


Pt.6  Ch.2 Sec.1New notation
  • Offering a new class notation (MC) differentiating on the requirements for certification of  machinery systems and components based on yacht type/size.

4. Information on coming rule editions

DNV GL publishes main rule editions annually.  The next main rule edition will be published in July 2021.

Additional amendments may be carried out, and all amendments will be specifically marked in the rules table of contents found here.  

Oslo, Norway, 2021-01-21

Henning B. Karlsen

Service Responsible – Ship Class

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