Guidance Manual for Tanker Structures - Consolidated Edition 2025-26

While the original manual primarily addressed the conventional single hull tanker, this revised edition includes 'IACS Unified Requirements (UR) Survey and Certification: Z10.4 Hull Surveys of Double Hull Oil Tankers' (Rev.18 Feb 2023), where changes introduced in Rev.18 are to be uniformly applied by IACS Societies for surveys commenced on or after 1 July 2024. The guidance also includes updated information on safety and access during surveys, including the updated 'IACS Recommendation No. 72: Confined Space Safe Practice Rev.4' (Jan 2025).

The guidance manual provides comprehensive guidance and information on IACS and owner's surveys, as well as on technical maintenance and repair. It includes guidance on structural defects, corrosion in tank spaces, fatigue and other survey procedures such as thickness measurement, which is important in monitoring.

This consolidated edition combines in one guidance manual the various sources of information necessary for assessing the condition of the ballast tanks, cargo tanks and structure of tankers in service. While the original manual mainly addressed the conventional single hull tanker, this revision includes IACS Recommendation No. 72: Confined Space Safe Practice - Rev.4 2025 and IACS Unified Requirements (UR) Survey and Certification: Z10.4 Hull Surveys of Double Hull Oil Tankers (Rev.18 Feb 2023), where changes introduced in Rev.18 are to be uniformly applied by IACS Societies for surveys commenced on or after 1 July 2024.

This Guidance Manual has been updated to provide a comprehensive overview of:

? IACS requirements for Special, Annual and Intermediate Surveys

? survey preparation, including a review of requirements, safety aspects, equipment and details of carrying out and reporting different types of surveys

? thickness measurements

? technical background and awareness of structural defects in terms of the effects on local strength or overall structural integrity

? basic maintenance and repair guidelines are provided along with sketches of experienced structural failures and proposed repairs

? documentation required for survey, including supporting documents

? the guidance of the Tanker Structure Co-operative Forum (see Appendix I for further details of the Forum) in areas of corrosion, defects and repairs, ultrasonic gauging and the strength of corroded structural items, as well as corrosion and maintenance evaluation of tanker structures.

Phase-Out of Single Hull Tankers and Implementation of UR Z10.4

Since 2016, single hull tankers (SHTs) have been phased out of international trading. Since 1993, double hull structures are the mandatory standard for tanker design, as detailed in the 1996 requirements of MARPOL Annex I, Regulation 19.

With the international phase-out of SHT effectively completed, this 2024 edition of the Guidance Manual has been comprehensively updated to contain the guidance relating to double hull oil tankers. References are made throughout to the information in IACS UR Z10.4.

However, for those wishing to consult the applicable parts of the Z10.1 Unified Requirements for Hull Surveys of Oil Tankers, reference can still be made to the current IACS version at: https://iacs.org.uk/resolutions/unified-requirements/ur-z/ur-z10-1-rev24-cln

Introduction to the 2024 Consolidated Edition
Chapter One ? Survey Preparation Guidelines
1.1 Survey Requirements
1.1.1 Class and Statutory Requirements
1.1.2 Owner?s Requirements
1.2 Safety and Access
1.2.1 Safety During Surveys
1.2.2 Access to the Structure
1.3 Ultrasonic Thickness Determination
1.3.1 Survey Team Qualifications
1.3.2 Basic Equipment Types
1.3.3 Thickness Measurement Accuracy
1.3.4 Measurement Procedures
1.4 Technical Background for Surveys
1.4.1 Nomenclature
1.4.2 Structural Load Descriptions
1.4.3 Structural Defects
1.4.4 Fatigue
1.4.5 Typical Corrosion Patterns
1.4.6 Factors Influencing Corrosion
1.4.7 Corrosion Trends in Tank Spaces
1.4.8 In-Service Corrosion Rates
1.4.9 Corrosion Control Systems
Chapter Two ? Survey Execution Guidelines
2.1 Introduction
2.2 General Planning Requirements
2.2.1 General
2.2.2 Data Collection and Reporting ? Databases
2.3 Structural Aspects
2.3.1 Tank Bottom Structures
2.3.2 Side Shell, Longitudinal and Transverse Bulkheads
2.3.3 Deckhead Structures
2.4 Risk Categories
2.4.1 Corrosion
2.4.2 Structural Elements
2.5 Classification Society Surveys/IACS Unified Requirements for Hull Surveys of Double Hull Oil Tankers
2.5.1 General
2.5.2 Special Survey
2.5.3 Annual Survey
2.5.4 Intermediate Survey
2.5.5 Preparation for Survey
2.6 Owner?s Surveys 44
2.6.1 General
2.6.2 General Condition Survey
2.6.3 Detailed Condition Survey
2.6.4 Corrosion Rate Survey
2.6.5 Repair Specification Survey
Chapter Three - Survey Data Analysis Guidelines
3.1 Method of Assessment 51
3.1.1 Steel Condition
3.1.2 Coating Condition Assessment
3.1.3 Cathodic Protection System Assessment
3.2 Structural Integrity
3.3 Acceptance Criteria
Chapter Four - Maintenance and Repair Guidelines
4.1 General
4.2 Type of Repair
4.3 Maintenance and Repair Methods
4.3.1 Repairs of Existing Coated Areas in Segregated Ballast Tanks
4.3.2 Repairs of Uncoated Areas in Cargo Tanks
4.3.3 Pitting and Grooving Repair
4.3.4 Steel Renewal
4.3.5 Steel Reinforcement
4.3.6 Steel Design Modification
4.3.7 Repairs of Structural Defects
4.4 Optimum Maintenance and Repair Strategy
4.4.1 General
4.4.2 Short-Term Maintenance and Repair Programme
4.4.3 Long-Term Maintenance and Repair Programme
Bibliography
Appendix I Background to Forum Activities
Appendix II IACS Unified Requirements UR Z10.4
Appendix III IACS Rec No. 72: Confined Space Safe Practice
Appendix IV Catalogue of Structural Detail Failures
Appendix V In-Service Corrosion Rate Studies
Appendix VI Structural Inspection Guidelines
Appendix VII Assessment of Existing Surface Coating Systems

TSCF

The Tanker Structure Co-operative Forum (TSCF) is an informal technical body whose membership is voluntary and comprised of Oil Companies, Independent Owners/Operators and Classification Societies who will actively contribute to the TSCF'S Mission.

The mission of the TSCF is to advance maritime safety through improvements in the design and maintenance of tanker structures. This is achieved by sharing technical knowledge and experience in order to gain a better understanding of the safety performance of tanker structures in service. Specific topic areas of interest include corrosion, structural defects, inspection procedures, and criteria for determining renewal of damaged or corroded structure.

The TSCF is committed to sharing accumulated experience on tanker structures with the marine industry. This is achieved through prompt public release of technical manuals and information papers, and proceedings of TSCF Shipbuilder's Meetings.

http://www.tscforum.org/AboutTSCF/interim.aspx