The International Association of Classification Societies (IACS) has released revised welding rules for marine and offshore structures, updating its Unified Requirements (UR) W11, W16, and W28. These revisions aim to harmonise high heat input welding requirements, improve the qualification of welding procedures, and ensure stronger alignment with internationally recognised standards such as ISO 15614-1 and AWS D1.1/D1.1M. The changes reflect extensive consultation with shipyards, steel manufacturers, and classification societies to better match real-world industry practices.
Harmonisation with International Standards and Stronger Welding Qualifications
A key focus of the revisions is the alignment of IACS welding requirements with global standards. The updated UR W28 now mirrors the structure and intent of ISO and AWS standards, improving consistency and global applicability. It also ensures coherence across other IACS Unified Requirements, including those governing hull structural steels, high-strength steels, welding consumables, and brittle crack arrest steels.
The revised rules introduce clearer definitions and qualification ranges for welding procedures, including a precise definition of high heat input welding expressed in kilojoules per centimetre (kJ/cm). Updated provisions also address base materials, welding consumables, welding positions, and post-weld heat treatment (PWHT), ensuring compatibility with newer steel grades and their mechanical properties.
Enhanced Controls for High Heat Input Welding and Inspection Requirements
The revisions introduce an optional approval scheme for high heat input welding procedures through a new Annex E in UR W28. This allows manufacturers to seek formal approval under a structured qualification framework, including welding tests on plates approved for high heat input grade notation. Importantly, existing qualification pathways remain valid even when steels are not specifically certified for high heat input, provided established UR W28 requirements are met.
Additionally, the updated rules clarify non-destructive testing (NDT) timing requirements based on steel yield strength. For steels with yield strength between 420 and 690 N/mm², NDT must be conducted at least 48 hours after welding, while higher-strength steels between 890 and 960 N/mm² require a minimum 72-hour waiting period unless PWHT is applied. UR W11 and UR W16 also introduce an optional manufacturing approval scheme for steels intended for high heat input welding, offering manufacturers a formal route to certify materials for demanding welding applications.
The revised IACS welding rules represent a significant step forward in improving safety, consistency, and global harmonisation in marine and offshore welding practices. By aligning with international standards, clarifying qualification and inspection requirements, and introducing optional approval schemes for high heat input welding, IACS has strengthened the framework governing critical structural work. As highlighted by IACS General Policy Group Chair Dr. Ajay Asok Kumar, these changes will support better-qualified welding procedures and more consistent application across the global maritime industry.
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Source: IACS
