Condition Assessment Scheme (CAS) in IMO GISIS

An Introduction and Practical Guide to Enhanced Surveys for Oil Tankers

Introduction: Why Ship Condition Assessment Matters for Tanker Safety

Oil tankers are among the most critical vessels in global shipping. They transport large quantities of crude oil and petroleum products across oceans, often close to coastlines and environmentally sensitive areas. When tanker accidents occur, the consequences can be severe—oil spills, environmental damage, economic loss, and long-term harm to coastal communities.

Experience has shown that the structural condition of aging oil tankers plays a major role in maritime accidents. Corrosion, fatigue cracking, poor maintenance, and inadequate inspections can significantly increase risk. For this reason, the international maritime community has placed special attention on older tankers, particularly those with single hull construction.

To strengthen oversight and ensure higher safety standards, the International Maritime Organization (IMO) introduced the Condition Assessment Scheme (CAS). To support transparency and international coordination, information related to CAS is made available through the “Condition Assessment Scheme” module of the Global Integrated Shipping Information System (GISIS).

This article provides a comprehensive introduction and practical guide to the CAS option in GISIS. It explains what CAS is, why it was introduced, how it works, what information is available in GISIS, and why this module is important for shipowners, flag States, port State control authorities, educators, and maritime professionals worldwide.

Understanding GISIS and Its Role in Tanker Safety Oversight

What Is the IMO Global Integrated Shipping Information System?

The Global Integrated Shipping Information System (GISIS) is an IMO-managed digital platform that collects and presents maritime information submitted by IMO Member States under international conventions and codes.

GISIS supports:

  • Transparency in maritime regulation

  • Consistent implementation of IMO instruments

  • Access to authoritative, State-submitted information

  • Oversight of safety, security, and environmental performance

The Condition Assessment Scheme (CAS) module is one of the most specialized safety-related components of GISIS, focusing specifically on structural integrity and condition of oil tankers.

What Is the Condition Assessment Scheme (CAS)?

Definition of CAS

The Condition Assessment Scheme (CAS) is an enhanced survey and assessment programme applied to certain oil tankers, particularly older vessels, to verify their structural condition beyond normal statutory surveys.

CAS requires:

  • More detailed inspections

  • Extensive thickness measurements

  • Independent verification

  • Thorough documentation of hull condition

Its purpose is to ensure that tankers operating at advanced ages continue to meet acceptable safety and environmental standards.

Why Was the Condition Assessment Scheme Introduced?

Lessons from Major Tanker Accidents

Several serious tanker accidents in past decades highlighted that:

  • Structural failure was a key contributing factor

  • Conventional surveys were sometimes insufficient

  • Aging tankers posed higher environmental risks

These events prompted the IMO to strengthen inspection regimes for older tankers.

Focus on Aging and Single-Hull Tankers

CAS was introduced primarily to address risks associated with:

  • Older oil tankers, especially beyond a certain age

  • Single-hull tankers, which offer less protection against oil spills

By applying enhanced scrutiny, CAS helps ensure that only tankers in acceptable structural condition continue to operate.

Legal Framework Behind the Condition Assessment Scheme

MARPOL Convention

The Condition Assessment Scheme is linked to the International Convention for the Prevention of Pollution from Ships (MARPOL), particularly provisions addressing oil pollution prevention.

CAS supports MARPOL objectives by:

  • Reducing the likelihood of oil spills

  • Strengthening tanker structural safety

  • Enhancing environmental protection

IMO Resolutions and Guidelines

CAS requirements are detailed in IMO resolutions and guidelines that specify:

  • Which ships are subject to CAS

  • How assessments must be conducted

  • What documentation is required

The GISIS CAS module reflects this regulatory framework.

Which Ships Are Subject to CAS?

Applicability Criteria

CAS generally applies to:

  • Oil tankers of a certain age, typically beyond 15 years

  • Tankers required to undergo enhanced surveys

  • Vessels operating under MARPOL provisions

The exact applicability depends on ship type, age, and regulatory context.

CAS and Double-Hull Transition

While the industry has largely transitioned to double-hull tankers, CAS remains relevant for:

  • Legacy vessels

  • Transitional compliance scenarios

  • Historical and regulatory oversight

What Does a CAS Survey Involve?

Enhanced Structural Inspection

A CAS survey goes beyond routine inspections and includes:

  • Close-up examination of hull structure

  • Detailed inspection of cargo tanks and ballast tanks

  • Verification of corrosion protection systems

Thickness Measurements

A major element of CAS is:

  • Extensive steel thickness measurements

  • Comparison with original scantlings

  • Assessment of corrosion margins

These measurements help determine whether structural strength remains adequate.

Independent Review and Documentation

CAS requires:

  • Independent evaluation of survey results

  • Comprehensive documentation

  • Clear reporting of structural condition

This ensures objectivity and transparency.

Purpose of the Condition Assessment Scheme Module in GISIS

Core Objectives

The CAS module in GISIS aims to:

  • Provide information related to CAS implementation

  • Support transparency in tanker safety oversight

  • Assist administrations and inspectors

  • Preserve institutional knowledge of enhanced survey outcomes

It serves as an information and governance tool, not a technical survey platform.

What Information Is Available in the GISIS CAS Module?

Types of Information Provided

Depending on what Member States submit, the module may include:

  • Information related to CAS applicability

  • References to CAS survey requirements

  • Data supporting oversight and monitoring

  • Links to regulatory frameworks

Detailed technical survey reports are not publicly disclosed, but the module supports administrative awareness.

Who Submits and Maintains CAS Information?

Role of Flag States

Flag States are responsible for:

  • Ensuring CAS surveys are conducted when required

  • Accepting survey results

  • Reporting relevant information to the IMO

Role of Recognized Organizations

Recognized Organizations (classification societies):

  • Conduct CAS surveys on behalf of flag States

  • Apply IMO and class rules

  • Provide technical expertise

However, final responsibility remains with the flag State.

How to Access the Condition Assessment Scheme Module in GISIS

Step 1: Access the GISIS Platform

Users access GISIS via the IMO website and enter the appropriate public area.

Step 2: Select “Condition Assessment Scheme”

From the GISIS module list, users select Condition Assessment Scheme (CAS).

Step 3: Review Available Information

Users can:

  • Understand CAS requirements

  • Use the information for compliance, education, or policy analysis

  • Support inspection and oversight activities

Importance of CAS for Maritime Safety and Environmental Protection

Reducing the Risk of Structural Failure

By identifying:

  • Excessive corrosion

  • Structural weaknesses

  • Maintenance deficiencies

CAS helps prevent catastrophic failures.

Protecting the Marine Environment

Oil spills from tanker structural failure can have long-lasting impacts. CAS supports:

  • Prevention rather than response

  • Stronger environmental safeguards

  • MARPOL objectives

Role of CAS in Port State Control

Supporting Inspection Decisions

Port State Control officers may consider CAS-related information when:

  • Inspecting older tankers

  • Assessing risk profiles

  • Evaluating compliance history

Enhancing Confidence in Certification

CAS provides assurance that:

  • Certificates reflect actual ship condition

  • Older tankers meet higher scrutiny standards

Practical Use Cases of the CAS Module

Flag State Administrations

Administrations use CAS information to:

  • Monitor aging tanker fleets

  • Make informed decisions on ship operation

  • Support policy development

Shipowners and Operators

Shipowners benefit from CAS by:

  • Identifying structural issues early

  • Planning maintenance and renewal

  • Demonstrating compliance and safety commitment

Maritime Educators and Researchers

CAS information supports:

  • Teaching on tanker safety

  • Analysis of aging ship risks

  • Understanding regulatory evolution

Relationship with Other GISIS Modules

The CAS module complements:

  • Recognized Organizations – survey delegation

  • Marine Casualties and Incidents – accident analysis

  • Port State Control – enforcement context

  • Pollution Prevention Equipment – environmental protection

Together, these modules provide a holistic view of tanker safety governance.

Common Misunderstandings About CAS

CAS Is Not a Routine Survey

CAS is additional and enhanced, not a replacement for normal surveys.

CAS Does Not Guarantee Unlimited Operation

A successful CAS does not mean a tanker can operate indefinitely. Age-related risks still apply.

Best Practices for Using the CAS Module in GISIS

  • Use it as an official reference source

  • Understand the link between CAS and MARPOL compliance

  • Combine information with class and flag guidance

  • Integrate CAS awareness into tanker training programs

Educational Value for Maritime Training and Academia

For maritime education, the CAS module provides:

  • Real-world insight into tanker safety regulation

  • Understanding of structural integrity assessment

  • Context for environmental risk management

It is especially valuable in courses on:

  • Tanker operations

  • Ship structural design

  • Maritime safety management

  • Marine environmental protection

CAS in the Context of Modern Shipping

Declining but Still Relevant

While many older tankers have been phased out, CAS remains important for:

  • Legacy vessels

  • Regulatory history

  • Understanding risk-based regulation

Lessons for Future Regulation

CAS demonstrates how:

  • Targeted regulation can address specific risks

  • Data and inspection depth improve safety outcomes

  • International cooperation enhances effectiveness

Conclusion: Strengthening Tanker Safety Through Enhanced Assessment

The Condition Assessment Scheme (CAS) option in the IMO Global Integrated Shipping Information System reflects the maritime community’s commitment to preventing tanker accidents before they happen.

By supporting enhanced structural assessment of aging oil tankers and providing transparency through GISIS, CAS has contributed significantly to:

  • Improved tanker safety

  • Reduced risk of oil pollution

  • Stronger confidence in maritime certification

For administrations, shipowners, inspectors, educators, researchers, and students, the GISIS CAS module offers a valuable window into one of the most important safety initiatives in modern tanker regulation.

In a sector where the consequences of failure are severe, CAS stands as a reminder that continuous vigilance, rigorous inspection, and informed governance are essential for safe and sustainable shipping.

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