DNV GL Rules for classification: Ships - January 2017

The 2017 January edition of DNV GL rules for classification: Ships is now available at www.DNVGL.com

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1. General information

New and amended rules were formally approved on November 28th 2016 and are included in the January 2017 edition of the rules. Entry into force date is generally July 1st 2017, however please note the immediate entry into force for hull related parts of the rules (to be found in Pt.3 and Pt.5); entry into force date being January 1st 2017.

The changes to the rules may be categorized into three:

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

Additional to the updates to the DNV GL rules for classification: Ships, there have also been updates to the DNV GL rules for classification: High speed and light crafts (HSLC) and the DNV GL rules for classification: Yachts. For accurate and detailed information on all rule sets, please visit www.DNVGL.com/rules-standards and/or contact your local DNV GL office.

2. DNV GL rules for classification: Ships

Below is given an overview of the main changes.

• New class notations

  Additional class notations:

  • Walk2Work (Pt.6 Ch.5 Sec.16)

• Revised class notations

  Ship type notations:

  • Passenger ships (Pt.5 Ch.4)
  • Fishing vessels (Pt.5 Ch.12 Sec.2)

  Additional class notations:

  • Dynamic Positioning (Pt.6 Ch.3 Sec.1 and 2)
  • Nautical Safety notations (Pt.6 Ch.3 Sec.3 and 5)
  • Transportation of Containers (Pt.6 Ch.5 Sec.1)
  • Helicopter deck installations (Pt.6 Ch.5 Sec.16)
  • Ballast Water Management (Pt.6 Ch.7 Sec.1)

• Changes to material related topics (Pt.2)

Rule reference	Description
Pt.2 Ch.1
	Alignment with IACS UR W16 High strength steels for welded structures (i.e. extra high strength steels in DNV GL rules) Established test requirements for t>100mm for normal and high strength grades.
Pt.2 Ch.2
	Alignment with IACS UR W16 High strength steels for welded structures Plate thickness up to max. 250 mm accepted by the rules. Introduction of 2 new strength grades VL 890 and VL 960.
Pt.2 Ch.4
	Alignment with IACS UR W11 Normal and higher strength hull structural steels. IACS UR W28 Welding procedure qualification tests of steels for hull construction and marine structures. IACS Rec.No.47 Shipbuilding and Repair Quality Standard.

Note: Changes to Pt.2 Ch.4 come into force with immediate effect; i.e. from January 1st 2017.

• Changes to hull related topics (Pt.3 and Pt.5)

Following the new technical platform for hull structures introduced with the DNV GL rules in October 2015, further updates have been carried out to streamline the application and refine scantling impact.

Please note that these changes come into force with immediate effect; i.e. from January 1st 2017.

• Reduced minimum thickness requirements with 0.5 mm for side and bottom plating.
  • Aligned with well proven and existing designs.

Rule reference	Description
Pt.3 Ch.3 Sec.3
	Net scantling approach for beam analysis: Removed the need for subtracting 0.5 tc from scantlings applied in beam analysis models. More convenient application and aligned with the procedure for FEM. Slightly reduced scantling requirements.
Pt.3 Ch.3 Sec.6
	Simplified requirement to tripping bracket arm length based on customer feedback. More convenient application and aligned the requirements with industry practise. Added requirement to fitting of brackets to prevent local bending of plate in tank boundaries. Normally no consequence as this is in line with present design practise. The added requirement provides a rule reference to require brackets fitted where needed.
Pt.3 Ch.4 Sec.2
	Increased horizontal bending moment in line with torsional moment. No consequence on scantlings observed. The adjustment is introduced to improve technical consistency.
Pt.3 Ch.4 Sec.3
	Reduction of accelerations for smaller vessels based on approval findings and investigation of design waves applied. To avoid unnecessary strengthening due to unrealistic/unphysical accelerations.
Pt.3 Ch.4 Sec.5
	Sea pressure in oblique sea at waterline tuned. The existing formulation led to an increased pressure inside in a limited area aft, resulting in a complicated design and approval process. More convenient application of the rules and avoid performing a separate scantling check within a limited area of the vessel.
Pt.3 Ch.6 Sec.3
	Reduced minimum thickness requirements for upper part of superstructure side - typically on passenger and ro-ro ships by ~1mm based on customer feedback. Gives reduced scantlings in upper part of superstructure not exposed to sea pressures. This reduction has a positive effect on stability and associated requirements for these vessels.
Pt.3 Ch.6 Sec.5
	Increased permissible stress for flooding (accidental) loads. Scantling requirements aligned with previously approved designs Gives reduced scantling requirements for container vessels. Overall safety is maintained since the modified acceptance criteria implies a sufficient reserve capacity to prevent an ultimate collapse in an accidental case.
Pt.3 Ch.8 Sec.1
	Revised buckling requirement for Permanent Means of Access (PMA) stringers. Current prescriptive formulation (taken from CSR) have been modified to require a general buckling check as for other structural members. Gives reduced required scantlings of PMA stringers, but still in line with proven and previously approved yard standards.
Pt.3 Ch.8 Sec.2
	Requirement to maximum distance between tripping brackets has been refined, targeting to reduce number of required tripping brackets for decks where stiffener spacing is very small (typically car decks). Gives a reduction in the required number of brackets. Aligned with present and proven industry practise.
Pt.5 Ch.12 Sec.2 Fishing vessels
	Reduced minimum thickness requirements with 0.5 mm for side and bottom plating. Aligned with well proven and existing designs.

• Changes for system related topics

Rule reference	Description
Pt.4 Ch.5
	Removed separate certification requirements to ancillaries integrated as part of larger units. Modified rules for crash stop for vessels with thrusters or pods to be in compliance with industry standard and maritime practice. The aim is to perform effective stopping without harming vessel or equipment. Removed requirement of 2 [rpm] turning speed for steering gear. Procedures with combination of steering & propulsion are accepted for means going astern, as an alternative to change of rotation direction for propeller.
Pt.4 Ch.6 Sec.8
	All remaining redundancy requirements for EGC systems removed as systems are not considered an important function in the class systematics. Specific section for urea based systems incorporating relevant requirements from fuel oil system rules (IACS UR M77.). Specific section for NaOH based systems incorporating relevant requirements from fuel oil system requirements, with same logic as for urea systems. New requirements for in-line exhaust gas cleaning systems, taking into account the increased risk of backflow and consequences of structural failures in the scrubber unit.
Pt.4 Ch.8
	Updated in accordance with IACS UR E24 Harmonic Distortion for Ship Electrical Distribution System including Harmonic Filters Added req. to documentation, on-board testing, and req. to protection and monitoring. Implemented acceptance criteria for new technology in marine use: Cables with aluminium conductors Permanent magnet electrical machines Clarified requirements for certification of slip ring units, added reference to IEC 60092-501. Removed acceptance of one dedicated standby generator.

• New class notations
  • Walk2Work (offshore gangway installations) (Pt.6 Ch.5 Sec.16)
    1. Operators in both oilfield and offshore wind turbine operation are increasingly focusing on alternative means of personnel transfer to installations.
    2. The new rules include requirements for:
       1. Certification of the gangway in accordance with DNVGL-ST-0358 Certification of offshore gangways for personnel transfer.
       2. Vessel station keeping ability. If handled by a DP system, class notation for DP is made mandatory.
       3. Stability and hull supporting structure.

• Other significant changes
  • Passenger Ships (Pt.5 Ch.4)
    1. Updated rules with test requirement for glass side walls consisting of more than one element or not supported on all four sides.
    2. Provided acceptance of glass side walls not supported on all four sides, in line with cruise design trend and present practice.
  • Dynamic positioning Systems (Pt.6 Ch.3 Sec.1 and 2)
    1. Modernized the rules for DP station keeping assessment by replacing “environmental regularity numbers”; ern* calculations with “Station keeping capability calculations” according to new DNVGL-ST-0111 Assessment of station keeping capability of dynamic positioning vessels published in July 2016.
    2. Station keeping assessment for ship-shaped mono-hulls can be performed by DNV GL and customers in the new free DNV GL web application.
  • Nautical safety notations (Pt.6 Ch.3 Sec.3 and 5)
    1. Aligned NAUT rules with the IMO performance standards for bridge alert management (BAM).
    2. Enhance the safety of operation through the BAM protocol and give a smooth implementation process for yards.
  • Transportation of containers (Pt.6 Ch.5 Sec.1)
    1. Specific requirements for container stowage on general cargo ships provided.
    2. Removed requirement for approved lashing computer for the vessels with limited container intake; limited to vessels with more than 2 tiers on deck and/or 3 in hold.
  • Helicopter deck installations (Pt.6 Ch.5 Sec.16)
    1. Clarified that aluminium-steel transition joints (bi-metallic connections) are not to be used for helideck structure in tensile exposed areas; being in line with current practice.
    2. Removed requirement for deck cambering. Replaced with general requirement for the deck to be constructed so that fluids will not accumulate on the deck.
  • Ballast water management (BWM) (Pt.6 Ch.7 Sec.1)
    1. Removed requirement for detailed calculations in the BWM plan for sequential exchange of ballast water when an approved loading computer is on board.