DNV Rules for Ships - July 2022 edition

The 2022 July edition of the DNV rules is now available at www.dnv.com.

General information

New and updated rules were formally approved on June 17th 2022 by Group CEO Remi Eriksen and are included in the July 2022 edition.

The main changes to the rules cover:

1. New and revised class notations
2. Implementation of external requirements (IACS and IMO)
3. General updates and corrections

The general entry into force date for these rules is 1st of January 2023. The rules may, however, be applied to projects contracted before this date upon agreement between parties.

Also in this year’s publication, rules having retroactive entry into force have been included in Pt. 7 Ch. 2.

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

In addition to the changes in the rules for Ships, smaller changes have also been made to rules for:

• Yachts
• Naval vessels
• High speed and light crafts
• Inland navigation vessels
• Floating docks
• Underwater technology

Rules for Offshore Units will be presented separately.

Below is given a general overview of the main changes in the rules for Classification of Ships.

Rules for ships

Main class

Ship type notations

Additional class notations

Topic updates commented

Below a few comments to a selected part of the updates are offered.

• Rotating machinery – Driven units / Podded and geared thrusters (Ch. 5 Sec. 3)
  • Introduced requirements for main and auxiliary steering gear power units to restart automatically upon power being restored after power failure.
  • Removed steering gear requirement for redundancy on component level, accepting an overall system redundancy principle.

• Bulk carriers and dry cargo ships / Steel coil requirements (Ch. 1 Sec. 3)
  • Calculations for inner bottom section modulus to be based on stiffener bending span
• Liquefied gas tankers (Ch. 7)
  • Clarified that for type-B LNG fuel tanks, alternative means to meet the overall safety standard (ISO 10042 and 5817 quality level B) may be accepted.  
• Service vessels / Windfarm service (Ch. 9 Sec. 5)
  • New class notation Windfarm Service meeting market need in relation to e.g. floating wind park service and maintenance.

• Propulsion, power generation and auxiliary systems (Ch. 2)
  • Gas fuelled ship installations (Sec. 5)
    • Clarified the requirements in relation to maximum probable leakages in fuel systems as being an essential safety parameter for designs and operations.
  • Low flashpoint liquid fuelled engines (Sec. 6)
    • Introduced new class notation Gasoline INST covering gasoline fuel installations used for refuelling of crafts, typically stored on board passenger vessels.
  • Redundant and alternative propulsion (Sec. 7)
    • Introduced a class notation – AP - covering alternative propulsion installations. Intended for design solutions with reduced propulsion power, e.g. intended to bring vessel home after failures on the main propulsion line.  This notation is replacing previous notation RP(1) and being adapted to market requests.
    • Introduced new qualifier  - B – for the class notation redundant propulsion – RP. The qualifier sets up requirements more lenient than given by qualifier 2, but still meets the overall intention of a redundant propulsion and steering arrangement where all proulsors are designed for parallel operation.
  • Wind assisted propulsion systems – WAPS (Sec. 12)
    • Experience and market development shows larger systems being installed, thus specific stability requirements are introduced and consequently the class notation is also made mandatory for vessels with wind assisted propulsion systems installed.  
  • Gas fuelled ammonia (Sec. 14)
    • Introduced requirement for cofferdam and A60 insulation between fuel preparation room and machinery space category A, taking into account the possible toxic hazard should a fire propagate between spaces.
• Navigation, manoeuvring and position keeping (Ch. 3)
  • Based on market feedback, where more flexible solutions for low emission and energy efficient operations based on closed bus-tie systems are requested, the ship rules are aligned with the present offshore class rules for DP3 and also opens for closed bus-tie operations for DP2.  Three new qualifiers are offered, covering basic closed bus-tie operation - CB, built in simulation test capabilities – CBS  and live short circuit and earth fault testing - CBT.
• Cargo operations / Anti roll measures for container ships (Ch. 4 Sec. 16)
  • Market request for support to avoid loss of containers through an increased ability to minimize excessive roll moptions.
  • Offering a new class notation ARCS with possibility to include a predictive roll software application (PSA) and/or an anti roll device (ARD).
• Platform Supply (Ch. 5 Sec. 15)
  • For conversion of ships for compliance with the OSV code, discussions with NMA and MCA have resulted in alternative solutions in meeting the code for tank venting and gas detection arrangements.  This will give more flexibility for redesign of existing vessels and also free more deck area for dry cargo.
• Mooring (Ch. 5 Sec. 25)
  • Mooring requirements of SOLAS II-1/3-8 Mooring and towing have been amended, formally entering into force in 2024. The new class notation Mooring facilitates early compliance with SOLAS.
• Occasional carriage of dry bulk cargo (Ch. 5 Sec. 26)
  • Resolution MSC.277(85) provides safety requirements for ships engaged in occasional carriage of dry bulk cargo which are not considered bulk carriers.
  • The requirements are presently applied as mandatory for ship types General dry cargo ship and MPV (Pt. 5 Ch. 1). 
  • Moving the requirements of the resolution into a new class notation – SBC – being mandatory for vessels designed for occasional carriage of dry bulk cargo having length above 150m and five cargo holds or more only. 
  • Introduces more flexibility in market and less cost for smaller vessels. 
• Navigation systems data driven (Ch. 11 Sec. 4)
  • Offering a new class notation NAUTConnect.
  • Introducing data driven communication and verification of nautical systems, addressing onboard and onshore systems and infrastructure.  The notation supports automatic collection and analysis of key system parameters,

Information in relation to rules with retroactive entry into force

New retroactive rule changes are given in RU-Ship Pt.7 Ch.2.

The introduced retroactive requirements are valid for newbuilds and conversions with contract for construction on or after the entry into force date given in the rules.

Two-island container ships: The first rule change is related to calculation of the global bi-moment and leads to reduced and more realistic hull torsion deformation and subsequent warping stresses. This rule change is retroactively entering into force 1st January 2022.

Container ships with upper structure of thick plates: The second rule change corrects the application of non-destructive testing (NDT) for upper hull girder of container ships having a coaming built of “thick steel plates”. This correction is accompanied with clarifications, simplifying the application of requirements for brittle crack arrest (BCA) designs. This rule change is retroactively entering into force 1st January 2019.

Information on coming rule editions

DNV publishes main rule editions annually. The next main rule edition will be published in July 2023.

Additional amendments may be carried out, and all amendments will be specifically marked here:

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Oslo, Norway, 2022-06-28

Henning B. Karlsen
Service Responsible – Ship Class