In June 2003, the IACS council responded to initiatives by the IMO and industry and decided to develop a set of common Rules for both oil tankers and bulk carriers. The first draft was issued in July 2004 and, after receiving a large volume of industry comments, a second draft was issued in April 2005. The second draft was open for comments until end of September; a large number of comments have been submitted. The main contributors seem to be DNV and the Greek Union of Shipping.
The Joint Bulker Project (JBP) Rules are applicable to single and double side skin bulk carriers as defined in IACS URS 11.2 of 90m in length and above. All the relevant requirements influencing the structural design, including SOLAS, Load Line and IACS, have been incorporated and the project is claimed by the JBP team to be based on the following objectives:
To eliminate competition between class societies on scantlings
To embrace the intentions of the anticipated IMO requirements for goal-based standards for newbuildings
To ensure that a ship complying with these new Rules will be recognised by the industry as being at least as safe, robust and fit for purpose as would have been required by any of the existing rules
To employ the combined experience of all class societies to develop an agreed set of Rules
A net scantling principle.
One of the main changes from current classification rules is the design life of 25 years in a North Atlantic environment. Today’s practice is 20 years’ trading in a world wide environment. The new harsh environment standard and long design life is expected to enhance safety and thus increase the scantlings of bulk carriers. Ramifications studies performed by both DNV internally and the JBP officially confirm this. A steel weight increase of 2–9% has been experienced.
Monitoring the discussion in the industry, one of the main issues of concern is the corrosion allowance included in the JBP Rules. The new corrosion allowance is now a fixed figure regardless of the original plate thickness, an approach totally different from the previous one, where a certain percentage of the plate thickness was stated. According to the JBP, the new corrosion additions correspond to 95% of the measured corrosion wastages after 25 years in service.
It should be noted that the corrosion additions were revised in the second draft of the JBP Rules. Generally, an addition of 0.5mm was introduced to all structural elements.
An example of the corrosion allowance before and after the introduction of the JBP Rules can be seen in the figure. The corrosion additions are based on the second draft of the Rules. It should be noted that the DNV corrosion additions are based on 20 years of service; the JBP uses 25 years of service.
Preparations for the introduction of JBP Rules by DNV
As mentioned above, DNV has played an active role in the period during which comments were invited and has submitted several comments. Several ramification studies have been undertaken and this work will continue until all uncertainties with respect to the understanding and interpretation of these Rules are in place.
People and tools up to speed on software development
Nauticus Hull is DNV’s comprehensive solution for the 3D modelling, design and analysis of ship structures. The software provides tools for simplified rule checks and scantling calculations and advanced tools for extended calculation procedures, including wave load and FE structural analysis.
During the past two years, Nauticus Hull has undergone a major upgrade to support the new JTP (Joint Tanker Project) Rules for double hull oil tankers, and DNV Software is well under way with the implementation of the new Rules for bulk carriers on the same platform.
DNV has made a strategic decision that software is to be an important factor in how we differentiate ourselves from the other class societies. Therefore, in addition to supporting the new Rules, Nauticus Hull will also undergo a broader and more general update based on user-feedback received over the past three years. Together, this constitutes an exciting challenge – to develop and deliver radically improved high-quality software within a very tight schedule.
New bulk rule check modules are necessary to deal efficiently with the far-reaching changes in the Rules. Some of the new Rule requirements introduce a radical shift towards more computerisation of the structural assessment.
Finite element analysis is mandatory for structural assessments of the hull structure within the cargo region. The Nauticus ship modelling and FEA software will be upgraded to meet the new requirements. A fully automatic buckling check based on the JBP buckling rules of the FE model will also be introduced to make the post-processing work more efficient.
DNV is committed to being the premier provider of software to support the new bulk rules, ensuring that our customers, and DNV, still have the most efficient tools for ship structural design.
Roald Vårheim, Head of Section
for Bulk Carriers and Container Ships,
DNV Maritime
Date: 08 February 2008