DNV DNV CLASSIFICATION NOTES 31.12 [ Obsolete ]

Introduction

Classification Notes shall be considered in connection with DNV Rules for Classification of Ships, Pt.3 Ch.1, Hull Structural Design, Ships with Length 100 metres and above, /1/, and Pt.5 Ch.5, Liquefied Gas Carriers, /2/. The aim of this Classification Note is to describe the scope and applicable procedures for strength analysis of the hull in the cargo area, the cargo tanks and the supporting hull structures of LNG carriers with IMO Type B cargo tanks constructed mainly of plane surfaces. Structural analysis carried out in accordance with the procedures outlined in this Classification Note will normally be basis for plan approval.

In general, LNG carriers should satisfy the strength criteria to main class 1A1 as given in the Rules Pt.3 Ch.1. The criteria for classification notation Tanker for Liquefied Gas as given in the Rules Pt.5 Ch.5 should be complied with for tank structures, tank supports*), and the hull structures supporting the cargo tank. The requirements of DNV Rules Pt.5 Ch.5 are considered to meet the requirements of the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, IGC Code.

*) See Pt.5 Ch.5 A1100: Prismatic B-tank design have normally supports blocks distributed on the inner bottom and the whole double bottom, depending on the load case considered, shall then be regarded as supporting structure.

Class notation NAUTICUS(Newbuilding) is normally mandatory for LNG carriers with independent tanks of type B. Additional class notations PLUS and CSA as defined in DNV rules Pt.3 Ch.1, may impose additional requirements for the hull structure.

Attention should be given to the additional requirements by flag or port authorities. Please note that USCG may have additional requirements for vessels trading to US ports.