New Standards and Services for Design of Offshore Structures
Authors: Ørbeck-Nilssen Knut , Haug Tom 
Published: October 2008

The new offshore Standards include a general Design Standard for offshore structures as well as specific Standards for offshore Ships, Semisubmersibles, Jackups, TLP's and Deep Draught Floaters (Spars). The Standards replace the present DNV Rules for Classification of such objects. The Standards are divided into three levels which enables separation of DNV specific Class requirements, Technical Standard and Recommended Practice.

The new offshore Standards will provide a new basis for the design of offshore structures for engineering companies. Oil companies/operators and ship owners will have extended possibility to describe the content of the Classification Service and the Standards will provide a better basis for cost estimates.

The Standards are based on the Load Resistance Design format (LRFD format). The format improve the consistency and uniformity of the safety level compared to existing offshore rules based on the working stress format. Selection of material is harmonised for the different types of structures. Requirements are given to methodology, degree of documentation, fabrication and inspection which may enable equivalent codes to be used.

The Technical Standards are supplemented by detailed technical design procedures in the Recommended Practice which clarify the use of the Standards. The technical requirements reflects the latest knowledge in the different areas like environmental loads, fatigue, sloshing loads due to green seas and capacity of structural members.

Introduction - Use of classification in the offshore industry

Classification Societies establishes Rules and Guidelines for design and fabrication of ships, offshore structures and floating marine structures in general. Issuing a Classification Certificate is a confirmation that the object has been built in compliance with the Classification Rule requirements.

The Rules have been formed and influenced by the role of the Class and the shipping market being served. The role of the Class is primarily to set an acceptable safety level and to ensure that the product is built and maintained according to this Standard. The approval from a recognised Classification Society has been a condition for insurance and a requirement from national bodies.

International maritime organisations have contributed to a unified world wide acceptable safety level. Through IACS members are committed to agreed minimum safety level which are reflected in the Rules from the Classification Society.

Some Flag States statutory rules and regulations are incorporated in the Classification Society Rules. Some Flag States accept partly or completely the Classification Society Rules. The Classification Society may also have been delegated work by the National Statutory body to act on their behalf.

The offshore industry has quite different tradition and contractual constellations than the shipping industry. In simplified terms this industry is divided into two main categories:Mobile units for explorationFixed installations for exploitation of oil and gas

The first category is similar to the shipping industry with respect business constellations, and operation and the services offered by the Classification Societies are well adjusted to their needs. DNV and other Classification Societies have in many years served this marked and gained valuable experience.