Vetting schemes are increasingly focusing on the design’s fatigue standard and history of in-service cracking and repairs.

Cracks may result in oil leaking into the double hull and, in the worst case, in oil pollution with all the inconvenience and expense associated with this.

DNV knows the structural fatigue challenges facing oil tankers. Material technology and fatigue analysis have for many years been among our special fields of competence and experience..

The oil and shipping activities in harsh environments in the North Sea started more than 40 years ago, and has ever since put focus on structural fatigue challenges. About 80% of all shuttle tankers operating in the North Sea are classed by DNV.

DNV has improved the additional class notations relating to the fatigue evaluation of tankers to offer yards and owners what is needed for their specific trade, beyond the basic scope of class.

The PLUS notation is intended for vessels operating in harsh areas. It includes an extended scope of fatigue strength verification for hull structural details. The PLUS notation extends on the CSR notation with a minimum design fatigue life of 25 years of North Atlantic operation, where PLUS specifies an extended scope of details to be verified. A new calculation procedure that covers all critical details in the transverse web frames using detailed FE analyses has been developed.

A new class notation CSA-FLS has been introduced for direct calculation of the fatigue life according to first principles.