A new open industry standard for class approval based on a 3D model

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As the shipping and shipbuilding industry is making great strides in digitization, there are more opportunities for Classification to streamline and speed up its approval processes where the use of 3D models instead of drawings has become a reality.

To date, plan approvals for new construction projects have been based on conventional 2D drawings. However, since most designers use 3D modeling software, the next obvious step is to extract the information needed for design approvals directly from these models and perform the entire review process digitally instead of manually. The challenge is to standardize the format and process for submitting design data to the class for approval in order to overcome compatibility issues.

A joint research project develops a concept

In 2016, DNV launched a joint industrial project involving design offices, CAD software developers, the Norwegian Research Council (NFR) and other partners to develop a concept of using 3D models as documentation. design for verification.

The result is a model-based class approval and verification scheme for new construction projects, enabled by a cloud-hosted digital model sharing platform. Cloud-based collaboration benefits from the “one source of truth” principle, eliminating media disruption, duplicate data entry, data quality issues and unnecessary work.

“The main drivers of a model-based approval process and digital workflow between stakeholders during the design phase are reduced time to market, improved quality and traceability,” explains Ole Christian Astrup, Senior Senior Specialist at DNV Maritime who led the project. CAD models have been used in the engineering industry for some time to communicate designs to manufacturers, builders, maintenance companies, and regulators.

The key: the Open Class 3D Model Exchange (OCX) format

Developing an open standard interchange format to ensure interoperability between all different CAD software applications and allow the class to examine models generated by many different CAD tools was a key activity of the JIP. The result is the Open Class 3D Exchange or OCX standard.

To ensure neutrality and avoid the emergence of multiple incompatible exchange standards, an independent consortium was formed to industrialize, promote and maintain the OCX standard. A number of classification societies including DNV, Lloyd’s Register, Bureau Veritas, Korean Register, Türk Loydu, as well as major computer aided design (CAD) vendors have joined.

“For classification societies to succeed with 3D model-based approval and reap its benefits, it is essential that OCX become a recognized industry standard. If this is to happen, the maritime industry must cooperate and work together to implement and use the standard. Therefore, DNV took the initiative and established a joint OCX consortium with the participation of major classification societies and the maritime industry, ”said Geir Dugstad, Director of Ship Classification and Technical Director at DNV Maritime.

Successful pilot with DSME and NAPA

The new 3D approval platform and “design-centric workflow” were piloted by DNV, NAPA and Daewoo Shipbuilding & Marine Engineering (DSME) as part of a Joint Development Project (JDP) in three parts for a very large crude oil transporter (VLCC) designed by DSME. The OCX 3D model has completely eliminated manual 2D modeling tasks, providing a seamless exchange of the 3D model between the CAD system and the DNV Nauticus Hull calculation tool.

The JDP has successfully demonstrated that the VLCC model designed by DSME using NAPA Designer can be reused by Nauticus Hull, providing instant computational evaluation of any part of the 3D model. This also benefits the site, which will save time by avoiding the tedious creation of the calculation models necessary to optimize the weight of the steel.

DNV and NAPA are developing a new 3D OCX integration between NAPA Designer and Nauticus Hull, which allows the designer to verify their design directly in NAPA. “As a provider of tool software for the early stages of vessel design, NAPA sees great potential in the current and future development of OCX. Instead of having individual interfaces between different software packages, the OCX concept opens up new possibilities to use the best tools, which will drive the digital transformation of the shipbuilding and ship design industries from a classic design. based on drawings to transparent information exchange using a 3D model. NAPA offers full support for importing and exporting OCX data and looks forward to its expansion becoming the global standard, ”said Mikko Forss, EVP, Design Solutions.

The OCX file exchange standard allows for a smooth flow of communication between the job site or designer, classroom and owner.

In the future, the whole process could take place on the cloud-hosted exchange platform integrated with the DNV customer portal. The design office or the shipyard design department must first convert its CAD model to the OCX exchange format using a software interface, then upload it to the DNV portal where it is automatically verified. against DNV rules by the rule calculator. The output highlights design parameters that were not accepted as well as rules that were violated and is saved with the model. Designers can instantly access the annotated model and return it to their desk. “It’s still in the future,” says Astrup. “But it’s technically quite feasible and again the main enabler is the OCX interchange format.”

Browser-based visualization

When designers or construction sites replace 2D drawings with a 3D model as design documentation, stakeholders will need a new tool to view and inspect the 3D model. To this end, DNV has developed the CAD neutral “Sesam Insight” web browser for viewing 3D OCX models. For a complete visual check, process participants can use “Sesam Insight” to view, zoom, rotate and annotate the OCX model. Engineers can compare different design revisions in multiple iterations to verify the direct consequences of the changes and gradually optimize the model. “One of the main aspects of this approach is that no files need to be sent back and forth,” says Astrup. “You don’t have to sit together in front of a client’s CAD system; the platform allows both parties to maintain a constant dialogue about the 3D model.

Once the CAD design is updated based on DNV’s feedback, the final model is again converted to OCX format and officially submitted for approval.

Multiple advantages for new construction projects

“Using 3D models for approval offers multiple benefits to both the designer and the class society,” says Astrup. “First of all, it saves the designers the manual effort of creating computational models, normally a large part of the hull structure design process. It also allows the class to take a look at a design ahead of time to provide feedback before the actual approval process, providing an opportunity for very early feedback and optimization. Of course, a design needs to have some maturity before it can be verified, but this step-by-step approach gives the customer a basis for making decisions earlier in the process and dramatically speeds up iterations and optimizations.

Duke Lee, Technical Director of Basic Hull Design at DSME, comments, “We are developing a 3D model-based design procedure using NAPA Designer to improve our design capability as well as the competitiveness of the engineering. As our 3D model can be used for class rule checking and can be submitted to the class for approval using the 3D OCX format, 3D OCX can be very useful both for DSME and for the class.

The virtual twin was born first

“The customer supplied OCX 3D model can be used to streamline and automate approval services for disciplines other than hull, which can be a significant time saver. Using the 3D model to streamline the entire plan approval process is a natural next step. The shared 3D model – essentially the birth of the virtual twin before the birth of the “real twin,” the real ship, also opens up many downstream opportunities to manage the in-service fleet, continues Astrup. To be able to reap these benefits, he stresses, it is essential that the class and owner obtain the rights to use the model from the construction site or the designer as the holder of the intellectual property rights to the CAD design. “DNV can act as a mediator between the yard and the owner to help clarify the copyright issue,” he says.

Given the enormous benefits of the design verification and approval process and the commitment of several large class companies to its support, Astrup hopes that OCX will become the unified standard for the entire marine industry in the near future.
Source: Paving the way for class approval based on a 3D model – DNV

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