Double Hull Oil Tankers Guidelines for Surveys, Assessment and Repair of Hull Structures IACS
: Witherby Seamanship International Ltd
This manual gives guidelines for a double hull oil tanker which is constructed primarily for the carriage of oil in bulk and which has the cargo tanks protected by a double hull that extends for the entire length of the cargo area, consisting of double sides and double bottom spaces for the carriage of water ballast or void spaces. The guidelines focus on the IACS Member Societies' survey procedures but may also be useful in connection with survey/examination schemes of other regulatory bodies, owners and operators. The manual includes a review of survey preparation guidelines, which cover the safety aspects related to the performance of the survey, the necessary access facilities, and the preparation necessary before the surveys can be carried out.
The survey guidelines encompass the different main structural areas of the hull where damages have been recorded, focusing on the main features of the structural items of each area..
An important feature of the manual is the inclusion of the section, which illustrates examples of structural deterioration and damages related to each structural area and gives what to look for, possible cause, and recommended repair methods, when considered appropriate..
This manual has been developed using the best information currently available. It is intended only as guidance in support of the sound judgment of Surveyors, and is to be used at the Surveyors' discretion..
Surveyors dealing with single hull oil tankers should be encouraged to read the 'Guidance Manual for Oil Tankers' by Tanker Structure Cooperative Forum.
IACS Common Structural Rules for Tankers implemented from April 2006 have been developed in response to a consistent and persistent call from industry for an increased standard of structural safety. This has been achieved through enhancing the design basis and applying engineering first principles. The development of the CSR for Tankers included review of existing Rules, new development using a first principle approach, application of the net thickness philosophy, an enhanced design environment and a longer life ie 25 years North Atlantic. These Rules are applicable to double hull oil tankers exceeding a length of 150 metres.
Note: Throughout this document reference is made to various IACS Unified Requirements (UR), Procedural Requirements (PR) and Recommendations. All URs and PRs and key recommendations are available from the IACS website