Rules of DNV GL Group AS
Germanischer Lloyd, now part of DNV, is one of the world's leading classification societies. Its "Rules for Classification" establish strict and systematic technical requirements for marine construction materials, particularly hull structural steel plates.
Germanischer Lloyd (GL), now part of DNV GL Group AS (DNV), is one of the world's leading classification societies. Its "Rules for Classification" establish strict and systematic technical requirements for marine construction materials, particularly hull structural steel plates, ensuring the structural integrity and safety of ships under various operating conditions.
Regarding steel plate specifications, GL classifies hull steel into ordinary strength grades (A, B, D, E) and higher strength grades (such as AH32, AH36, AH40, DH32, DH36, DH40, EH32, EH36, EH40), based on the structural location, stress levels, and environmental conditions. Each grade has defined requirements for chemical composition, mechanical properties, and toughness. To ensure weldability and crack resistance, the rules strictly control carbon equivalent (Ceq) and limit harmful elements like sulfur and phosphorus, especially for high-strength and low-temperature service steels.
Mechanical properties are central to GL’s plate requirements. The rules specify yield strength, tensile strength, elongation, and Charpy V-notch impact energy (KV2) at ambient and low temperatures (e.g., 0°C, -20°C, -40°C). For vessels operating in polar or cold regions, critical structural plates must pass impact tests at -40°C or lower to prevent brittle fracture.
Additionally, GL sets detailed requirements for manufacturing processes, surface quality, dimensional tolerances, and non-destructive testing (e.g., ultrasonic testing). Steel production must be witnessed by GL surveyors (WITNESS), and full material certification is required. All plates used in primary load-bearing structures must be fully traceable, with complete quality records from steelmaking to final product.
In summary, Germanischer Lloyd ensures the long-term safety and reliability of marine steel plates in demanding maritime environments through scientific material grading, rigorous performance criteria, and comprehensive quality control.
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