The DNV 2.7-1 and DNV 2.7-3 standards are both critical certifications for offshore containers, each serving distinct purposes and adhering to different design philosophies. Understanding the main differences between these two standards is essential for ensuring the safe and efficient use of offshore containers in various applications.
The DNV 2.7-1 standard, also known as DNVGL-ST-E271, is based on the European standard EN 12079 and is globally accepted for the offshore lifting of containers at sea. This standard follows a “design by code” philosophy, which means that if the offshore container falls within specified categories, the designated design criteria are applied. The DNV 2.7-1 certification ensures the safety of the crews working with the containers, the environment, and the vessels and installations to which the containers are transported. The standard covers various aspects, including design, manufacture, testing, certification, marking, and periodic inspection of offshore containers. It is crucial for containers intended for repeated use in transporting goods or equipment in offshore environments.
One of the key features of DNV 2.7-1 is its focus on the safe lifting and handling of containers between floating vessels and between vessels and offshore installations. The standard specifies requirements for the structural integrity and stability of the containers, ensuring they can withstand the harsh conditions of offshore operations. The maximum gross weight for DNV 2.7-1 certified containers is typically less than 25,000 kg, making it suitable for a wide range of applications where lighter containers are required.
In contrast, the DNV 2.7-3 standard, or DNVGL-ST-E273, adheres to a “design by analysis” approach. This philosophy places more responsibility on the design engineer to provide the design basis and conduct detailed analyses to ensure the container meets the required safety and performance criteria. The DNV 2.7-3 certification is intended for portable offshore units (POUs) that may be designed for single or repeated offshore transport and installation, including subsea lifting. These units can have a maximum gross weight exceeding 25,000 kg, making them suitable for heavier and more specialized applications.
The DNV 2.7-3 standard covers a broader range of offshore units, including those intended for special service tasks such as laboratories, workshops, stores, power plants, and control stations. These units are often designed for temporary installations and may include features not typically found in standard offshore containers. The standard emphasizes the need for detailed analysis and testing to ensure the units can safely perform their intended functions in offshore environments.
Another significant difference between the two standards lies in their applicability to specific types of offshore units. DNV 2.7-1 is primarily focused on offshore containers used for the transportation of goods and equipment, while DNV 2.7-3 encompasses a wider variety of portable offshore units, including those designed for special service tasks. This distinction is important for designers and engineers who must select the appropriate standard based on the intended use and design requirements of the offshore unit.
Both DNV 2.7-1 and DNV 2.7-3 standards aim to ensure the safety and reliability of offshore containers and units, but they do so through different design approaches and criteria. The choice between the two standards depends on the specific requirements of the offshore operation, the weight and size of the container or unit, and the intended application. Understanding these differences is crucial for selecting the appropriate certification and ensuring compliance with the relevant safety and performance standards in offshore environments.