Guidance Manual for Tanker Structures - Consolidated Edition 2027

This consolidated edition has been updated to reflect the completed transition to double hull oil tankers, with guidance aligned to 'IACS Unified Requirements (UR) Survey and Certification: Z10.4 Hull Surveys of Double Hull Oil Tankers (Rev.18 Feb 2023)' and Chapter 15 of the 'Code of Safe Working Practices for Merchant Seafarers (COSWP) - 2026 Edition' on safe enclosed space entry, which is now included in the manual.

The guidance manual supplies comprehensive information on IACS survey requirements for Special, Annual and Intermediate Surveys, survey preparation and reporting, thickness measurements, structural defects, corrosion, maintenance and repairs and required survey documentation. Practical guidance from the Tanker Structure Co-operative Forum to support the assessment and monitoring of in-service tanker structures is also provided.

An ideal resource for those who require all of the necessary information to assess and monitor the condition of in-service ballast tanks, cargo tanks and other tanker structures.

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 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.

Introduction to the 2026-27 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
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
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
Appendices
Appendix I Background to Forum Activities
Appendix II IACS Unified Requirements UR Z10.4
Appendix III COSWP Entering Enclosed Spaces
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
Appendix VIII IACS Rec No. 47: Shipbuilding and Repair Quality Standard

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