Double Hull Oil Tankers: Guidelines for Surveys, Assessment and Repair of Hull Structures 2nd Edition 2020

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.

This manual has been developed using the best information currently available. It is intended only as guidance in support of the sound judgement of Surveyors, and is to be used at the Surveyors' discretion.

This book 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.

The International Association of Classification Societies (IACS) manuals provide guidelines to assist the Surveyors of IACS Member Societies, and other interested parties, involved in the survey, assessment and repair of hull structures for certain ship types.

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. It consists of double sides and double bottom spaces for the carriage of water ballast or void spaces.

These 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. It includes a review of survey preparation guidelines, which cover the safety aspects related to the performance of the survey, access facilities and the preparation necessary before the surveys can be carried out.

The survey guidelines encompass the different 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 that illustrates examples of structural deterioration and damages related to each structural area. It shows what to look for, possible causes 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. It is recognised that alternative and satisfactory methods are already applied by Surveyors. Should there be any doubt with regard to interpretation or validity in connection with particular applications, clarification should be obtained from the Classification Society concerned.

Surveyors dealing with single hull oil tankers should be encouraged to read the ‘Guidance Manual for Tanker Structures’, based on the practices of the Tanker Structure Co-operative Forum.

IACS Common Structural Rules for Tankers, implemented in April 2006 and updated in 2019, were developed in response to a consistent and persistent call from industry for an increased standard of structural safety. This was 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. The 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 (http://www.iacs.org.uk ).

1 Introduction

2 Classification Survey Requirements

2.1 General

2.2 Annual Surveys

2.3 Intermediate Surveys

2.4 Special Surveys

2.5 Drydocking (Bottom) Surveys

2.6 Damage and Repair Surveys

3 Technical Background for Surveys

3.1 General

3.2 Definitions

3.3 Structural Load Descriptions

3.4 Structural Defects, Damages and Deterioration

3.5 Structural Detail Failures and Repairs

4 Survey Planning, Preparation and Execution

4.1 General

4.2 Survey Programme

4.3 Survey Planning Meeting

4.4 Conditions for Survey

4.5 Access Arrangement and Safety

4.6 Use of Boats and Rafts

4.7 Personal Equipment

4.8 Thickness Measurement and Fracture Detection

4.9 Survey at Sea or at Anchorage

4.10 Documentation on Board

4.11 Reporting and Evaluation of Survey

5 Structural Detail Failures and Repairs

5.1 General

5.2 Actions to be Taken by the Classification Society when Fatigue Failures have been Identified

5.3 Catalogue of Structural Detail Failures and Repairs