DNV GL Rules for Ships - July 2019 edition
The 2019 July edition of DNV GL rules for Ships is now available.
1. General information
New and amended rules were formally approved on June 21st 2019 by the Group CEO Remi Eriksen, and are included in the July 2019 edition of the rules.
The changes to the rules may be categorized as:
- New and revised class notations
- Implementation of external requirements (IACS unified requirements and relevant IMO codes)
- General updates and corrections
The entry into force date for these rules is 1st of January 2020. The rules may, however, be applied to projects contracted before this date upon agreement between parties.
To find out more on the changes, please contact your local DNV GL office. You can also find more details under “Changes - current” in the individual documents - compilations of the changes for all rule documents can be found below.
Additional to the updates to the rules for classification of Ships, there have also been smaller updates to rules for classification of High speed and light crafts (RU-HSLC), Naval vessels (RU-NAVAL) and Yachts (RU-YACHTS).
2. Main changes
Below is given a general overview of main changes in the rules for classification of ships.
2.1 New class notations
Ship type notations
| Class notation | Rule reference
|
| Pt.5 Ch.7 Sec.25 |
Additional class notations
| Class notation | Rule reference
DNVGL-RU-SHIP |
| Pt.6 Ch.1 Sec.13 |
| Pt.6 Ch.2 Sec.11 |
| Pt.6 Ch.2 Sec.12 |
| Pt.6 Ch.2 Sec.13 |
| Pt.6 Ch.4 Sec.13 |
| Pt.6 Ch.4 Sec.14 |
| Pt.6 Ch.5 Sec.15 |
| Pt.6 Ch.5 Sec.16 |
| Pt.6 Ch.6 Sec.4 |
| Pt.6 Ch.6 Sec.7 |
| Pt.6 Ch.7 Sec.8 |
| Pt.6 Ch.9 Sec.9 |
2.2 Revised class notations
Ship type notations
| Class notation | Rule reference
|
| Pt.5 Ch.2 |
| Pt.5 Ch.4 |
| Pt.5 Ch.5 |
| Pt.5 Ch.6 |
| Pt.5 Ch.10 Sec.10 |
| Pt.5 Ch.9 Sec.3 |
| Pt.5 Ch.10 Sec.2 |
| Pt.5 Ch.10 Sec.11 |
Additional class notations
| Class notation | Rule reference
DNVGL-RU-SHIP |
| Pt.6 Ch.1 Sec.6/7 |
| Pt.6 Ch.1 Sec.8 |
| Pt.6 Ch.2 Sec.1 |
| Pt.6 Ch.2 Sec.5 |
| Pt.6 Ch.2 Sec-6 |
| Pt.6 Ch.3 Sec.3 |
| Pt.6 Ch.4 Sec.2 |
| Pt.6 Ch.4 Sec.11 |
| Pt.6 Ch.6 Sec.3 |
| Pt.6 Ch.7 Sec.5 |
| Pt.6 Ch.7 Sec.7 |
2.3 Changes to material related topics (DNVGL-RU-SHIP Pt.2)
a. Metallic materials (Pt.2 Ch.2)
i. Added new grades of steel forgings for low temperature application.
ii. Reduced the required extent of:
– mechanical testing for pipe fittings
– required testing for pressed parts
– impact testing for grades VL D47 and VL E47
iii. Reduced specified minimum limit of aluminum in steel grade VL 9Ni.
iv. Aligned ship and offshore rules.
b. Fabrication and testing (Pt.2 Ch.4)
i. Added requirements for very high strength steels VL 890 and VL 960:
– specified limitations to cold forming
– specified requirements for welding consumables.
ii. Waived extended NDT for isolated volumetric indications.
iii. Specified requirements for temporary corrosion/oxidation preventive coatings.
iv. Revised welding procedure specification (WPS) requirements to a number of processes and applications.
2.4 Changes to hull related topics (Rules Part 3)
The following is an excerpt of the changes made to Part 3:
a. Bracketed end connections of non-continuous stiffeners (Pt.3 Ch.3)
i. An investigation by non-linear FEA has been carried out to investigate the capacity of bracketed connections compared with continuous stiffeners, concluding that:
– for stiffeners with the web welded, the requirement to steel grade for the bracket is removed
– for stiffeners with the web not welded, the requirement to steel grade for the bracket is maintained and the minimum size requirement has been increased by 10%.
b. Web frames with low web angle (Pt.3 Ch.3)
i. Requirements to the connection of stiffeners to primary support members (PMS) has been corrected and made dependent on the angle between the PSM web and the plating in line with the principles for section modulus and shear area for PSM.
ii. The connection area requirement for impact loads (bow impact/bottom slamming/stern slamming) has been changed from a special one in Ch.10 to the general requirement in Ch.6 .
c. Tank testing loads (Pt.3 Ch.6)
i.Design loads for the outer shell below ballast water line need to consider possible tank testing at the low draft or in dry dock.
ii. The design testing pressure of tanks with a boundary to sea is increased by reducing the static counter pressure from outside.
d. Finite element acceptance criteria (Pt.3 Ch.7 / Ch.8)
i. For the acceptance criterion for static hull girder loads for harbor/special operations, both the permissible utilization factor for FE yield (both coarse mesh and fine mesh) and the permissible utilization factor for FE buckling, have been increased by 6.5% .
e. Foundation and supporting structure (Pt.3 Ch.11)
i. Class involvement in small, non-essential foundations and supporting structures is relaxed.
f. Welding (Pt.3 Ch.13)
i. A procedure for the direct stress analysis of welds has been added. Such stress analysis may be applicable in fillet weld joints with high tensile stress in the abutting plate .
ii. The necessary extent of increased fillet weld in way of hatch coamings has been further investigated and rules have been updated accordingly.
g. Rudder (Pt.3 Ch.14)
i. Rules are updated and aligned with IACS UR S10 Rev.5. The more important change is the requirement to protrusions for solid parts in heavy forged or cast steel.
ii. For areas with high in-plane stresses, the material factor, k, has been set to 1.0 (no benefit for high tensile (HT) steel) in way of one side welded butt joints where the weld root is not accessible after welding. This rules change goes beyond UR S10 Rev.5.
iii. Changes have been done in close contact with rudder designers.
2.5 Changes to system related topics (Rules Part 4)
There is a limited number of changes for the systems part of the rules this year. Below we have listed two of the more important:
a. Shaft alignment – viscosity factor for EAL (Pt.4 Ch.2 Sec.4)
i. There has been an increased number of stern tube bearing damages since 2014, whereas one possible contributing factor to the damages are the introduction of environmentally acceptable lubricants (EAL).
ii. Rules now establish relations between viscosity and temperature/pressure and also introduce a viscosity factor for oil film criteria calculation.
b. Electrical installations (Pt.4 Ch.8)
i. The technology on energy sources and storage systems and also on DC distribution systems is further developing.
– New requirements for alternative sources of energy and energy storage systems introduced
– Rules for DC distribution systems are updated to cater for the latest development.
3. Class notations commented
Below is a summary of all new class notations and excerpt of changes to some of the revised notations.
3.1 New class notations (Rules Part 5 and 6)
Ship type notations
a) FSU for liquefied gas (Pt.5 Ch.7 Sec.25)- A new ship type notation for floating storage units (FSU) that may be used for storage vessels intended to operate in permanently moored locations.
Additional class notations
NAABSA (not always afloat but safe aground - Pt.6 Ch.1 Sec.13)
- The additional class notation includes an increased level of safety, related to the strengthening of the double bottom hull structure for vessels touching the ground during loading and unloading in dedicated NAABSA ports. It is assumed that the vessel will be grounded on a plane and homogeneous sea bed with no hard points.
- The overall intention of the safe return to port is to increase the safety level of passenger ships through more redundant system arrangements, providing increased robustness and fault tolerance. The regulations are given as a goal-based standard in SOLAS and apply to passenger ships above a certain size. The SRtP scheme has a substantial impact on the vessel design and system arrangements and is closely linked to the operation of the vessel. The purpose of the additional class notation is to frame the relevant goal-based regulations of SOLAS in a systematic and structured class-context by addressing the various implications of the regulations, describing the key activities, work process and responsibilities and providing requirements and acceptance criteria for system design to support the functional requirements of the goal-based standard.
WAPS (wind assisted propulsion systems – Pt.6 Ch.2 Sec.12)
- Wind assisted propulsion systems like rotor sails and wing rigs are gaining market interest as a mean to save fuel and to support the reduction of shipping related emissions. Formal rules and standards for this are however missing in the market interface. The objective of the class notation is to provide a set of requirements covering both operational and technical safety aspects related to the installation of WAPS onboard ships.
- The class notation provides criteria for the safe and environmentally friendly arrangement and installation of machinery for propulsion and auxiliary purposes, using LPG as fuel. The requirements cover the ship's gas fuel system, from the ship's gas fuel bunkering connection up to and including the gas consumers. Further, the requirements cover arrangement and location of gas fuel tanks and all spaces with fuel gas piping and installations, including requirements for the entrances to such spaces. Hazardous areas and spaces, due to the fuel gas installations, are defined. Requirements for control, monitoring and safety systems for the fuel gas installations are included.
- LR2 tankers are fully coated and many are designed as standard crude tankers with plane bulkheads (internal structures) and pump room type cargo system. This implies that they need to carry intermediate cargo on three consecutive voyages when changing from dirty cargo to clean petroleum product (CPP). The notation sets requirements for arrangements and systems for improved tank cleaning when changing from dirty to clean oil cargoes.
- More LNG carriers are considering converted to floating storage and regasification units (FSRU). Preparing a vessel for a future conversion, will give improved flexibility and support an efficient and cost-effective conversion process. The class notation supports preparedness for converting a vessel from an LNG carrier to an FSRU by addressing and setting requirements to relevant systems and equipment.
- Following the IMO Res. A.1122(30) which covers requirements for OSVs carrying chemicals, a class notation covering carriage of all chemicals listed in IBC code and MEPC.2 Circ. together with dry bulk, liquefied nitrogen/carbon dioxide, and oil cargoes are offered.
- The notation may be implemented on all vessels engaged in transport of cargoes to offshore installations.
- A new class notation indicating that the vessel is prepared for the installation of an offshore gangway (often temporary) with regards to e.g.:
- designated area
- supporting structures
- power
- dynamic positioning
- sea-fastening.
- Class notation for compliance with the IMO polar code which entered into force 1st of January 2017.
- The notation also provides the DNV GL interpretation of the code.
- Class notation offering support for the design of vessels intended to proceed in ice by stern first without losing the capability to run efficiently in open waters.
- External noise emission to residential areas close to ports have got increased attention the last years, where many ports are struggling with complaints with respect to noise from ships.
- External noise is typically one of the top 5 most important environmental parameters defined by ports.
- The new class notationdefines a standard measurement procedure for airborne emitted noise from ships.
- An increased number of floating storage and regasification units (FSRU) and floating storage units (FSU) is in operation and need a flexible survey program which suits their operation profile and intended service.
- If units are located in favorable locations, like in sheltered locations or by a jetty, only reduced loads act on the unit and hence an alternative survey programme with extended interval between survey of the internal cargo tank(s) can be suitable compared to the units trading as LNGCs worldwide.
3.2 Revised class notations
Ship type notations
Container ship (DNVGL-RU-SHIP Pt.5 Ch.2 Sec.4)- Aligned yield strength assessment according with IACS UR S11A.
- This may give scantling and steel weight reduction on the outer parts of the hull, without influencing on safety
- Rules for glass balustrades implemented.
- A reduction factor for pillar loads for multiple deck supporting pillar lines introduced as an option for more realistic buckling approach.
- The minimum glass thickness for balcony doors is adjusted in order to be aligned with the minimum external pressure on the superstructure side and deckhouse side, PA-min.
Additional class notations
PLUS / CSA (Pt.6 Ch.1 Sec.6/7)
- The notation now offers a “simplified method” without FE modeling as an alternative to direct FE analysis. Details are also described in DNVGL-CG-0152 Plus-extended fatigue analysis of ship details.
- The method gives significantly less design time and documentation requirements.
RSD (Pt.6 Ch.1 Sec.8)
- The notation is revised to also cover small/medium sized container vessels offering a simplified method where the cost for calculations may be reduced to 1/3 compared to the full scope for large container vessels.
- For container vessels, the notation is also introducing an optional design verification for extended North Atlantic operations.
- The notation is also opened for vessels with class notation Multi-purpose dry cargo ship and General dry cargo ship.
NAUT (Pt.6 Ch.3 Sec.3)
- A new INS+ qualifier in line with prevailing technology and development of regulatory codes is replacing the current ICS qualifier for integrated navigation systems..
CCO (Pt.6 Ch.4 Sec.2)
- The rules have been aligned with external requirements such as OCIMF pump room safety guideline and OCIMF SIRE requirements for cargo instrumentation and remote control.
- They are also adapted to cover shuttle tanker specialties.
VCS (Pt.6 Ch.4 Sec.11)
- The notation now offers a new qualifier for laden voyages.
Winterized (Pt.6 Ch.6 Sec.3)
- Meeting market feedback to offer a notation for ships intended to operate in the northern Baltic Sea during winter, or in areas with similar conditions.
- The notation presents simpler and prescriptive requirements adapted to the relevant operational area and gives owners good basis for further upgrade to meet operations within polar waters.
ER (emission reduction – Pt 6 Ch.7 Sec.7)
- The notation offers two new voluntary qualifiers:
- Enhanced: Emission reduction function is defined as essential for operations and requirements for availability are given.
- Zero discharge: Covers the ability to operate with no discharge to sea.
- Additionally, new requirements for exhaust gas recirculation (according to MEPC. 307(73)) and new types of exhaust arrangements (blocking systems) are introduced.