Understanding Annex M of CSA W59 and Its Connection to IACS Classification Society Rules

Introduction

Annex M of CSA W47, is one of the informative annexes included to help engineers, welding engineers, inspectors, and fabricators understand the application of structural welding requirements to steels that originate outside the traditional Canadian structural steel specifications. In particular, Annex M is closely associated with the recognition of materials used in the marine, offshore, and shipbuilding industries, many of which are governed by rules developed through the International Association of Classification Societies (IACS).

For inspectors and welding engineers, Annex M is important because it bridges the gap between Canadian structural welding standards and the global steel grades commonly used in offshore structures, marine terminals, shipbuilding, and other heavy industrial applications.

What Is IACS?

The International Association of Classification Societies (IACS) is an organization that harmonizes technical requirements used by the world's major marine classification societies. Its members include:

Lloyd's Register (LR) American Bureau of Shipping (ABS) DNV Bureau Veritas (BV) ClassNK RINA China Classification Society (CCS) Korean Register (KR)

These organizations establish requirements for:

Ship structures Offshore platforms Floating production facilities Marine equipment Structural steels used in marine environments

Classification societies developed many of the steel grades used today in offshore and shipbuilding applications long before they became common in other industries.

Why Was Annex M Added?

Historically, CSA W59/W47.1 primarily recognized structural steels from:

CSA ASTM ASTM/AASHTO Other conventional structural specifications

However, Canadian fabricators increasingly encountered projects involving:

Offshore structures Port facilities Marine equipment Ship repairs Heavy industrial modules fabricated for international clients

As a result, CSA expanded recognition of additional material standards, including steels governed by ABS, Lloyd's Register, and IACS-recognized specifications. The 2018 edition specifically noted the addition of several material specifications from ABS, API, ASTM, CSA, IACS and Lloyd's.

Annex M was developed to provide guidance regarding these materials and their use within the framework of CSA W59.

Relationship Between Annex M and Classification Society Steels

Many structural steels used in marine construction have familiar designations such as:

Normal Strength Grades Grade A Grade B Grade D Grade E Higher Strength Grades AH36 DH36 EH36 FH36 Higher Yield Variants AH40 DH40 EH40 FH40

These steels are commonly approved under classification society requirements and are recognized by multiple organizations through harmonized IACS requirements.

Although these grades may carry different certification stamps depending on whether they are supplied under ABS, DNV, LR, BV, or another society, their chemistry and mechanical property requirements are often governed by the same IACS Unified Requirements.

The IACS Concept of Harmonization

One of the most misunderstood aspects of marine steels is that many classification societies are not creating completely different steel grades.

For example:

Classification Society Common GradeABS AH36 DNV AH36 Lloyd's Register AH36 Bureau Veritas AH36 ClassNK AH36

While individual certification and approval processes differ, the underlying steel requirements are largely harmonized through IACS.

This means that:

Yield strength requirements are similar. Tensile strength requirements are similar. Charpy impact requirements are similar. Material testing requirements are similar.

The result is a high degree of international equivalency.

Connection to Offshore Structures

Many offshore structures are fabricated using steels such as:

EH36 FH36 EH40 FH40

These materials offer:

High strength Excellent notch toughness Improved low-temperature performance Proven fatigue performance

Because offshore structures experience:

Wave loading Wind loading Cyclic loading Fatigue-sensitive service

weld quality requirements become significantly more stringent than those typically applied to statically loaded structures.

This aligns well with the fatigue philosophy found in CSA W59 and CSA S16 for cyclically loaded structures.

Why Annex M Matters to Welding Engineers

For a CWB Retained Welding Engineer, Annex M is valuable because it assists in determining:

Material Grouping

How IACS steels fit within CSA W59 material groups.

Procedure Qualification

Whether an existing WPS or WPDS can be applied to:

AH36 DH36 EH36 FH36

or whether additional qualification is required.

Preheat Requirements

The carbon equivalent and mechanical properties of offshore steels may influence:

Preheat Interpass temperature Heat input limits Filler Metal Selection

Typical consumables include:

E4918 / E7018 E5518 FCAW E71T-1C/M Higher strength consumables where matching strength is required

Selection depends on:

Base metal strength Service temperature Design requirements Classification society requirements Annex M and Global Fabrication

Annex M demonstrates an important fact:

Structural steel fabrication is increasingly global.

A fabrication shop in Ontario may receive material certified to:

ABS DNV Lloyd's BV ClassNK

even though the fabrication is taking place under CSA W59 and CSA W47.1 certification requirements.

Annex M helps ensure these internationally recognized materials can be properly evaluated and welded within the Canadian regulatory framework.

Conclusion

Annex M of CSA W59 represents the Canadian welding industry's recognition of internationally accepted marine and offshore structural steels. Its roots can be traced to requirements developed by IACS and adopted by major classification societies such as ABS, DNV, Lloyd's Register, Bureau Veritas, and ClassNK. These organizations largely use harmonized material requirements, meaning many of their steel grades are effectively equivalent despite carrying different society certifications.

For welding engineers, inspectors, and fabricators, Annex M provides a practical bridge between Canadian welding standards and globally recognized marine and offshore materials, ensuring that steels such as AH36, DH36, EH36, and FH36 can be used with confidence while maintaining compliance with CSA W59 requirements and sound welding engineering practices