Overview
EN ISO 18491:2026, Welding and allied processes - Measurement of arc energies (ISO 18491:2026), establishes standardized methods for measuring the parameters necessary to calculate arc energies during arc welding processes. Developed by CEN and ISO, this standard addresses consistency, reliability, and comparability in determining arc energy across both traditional and waveform-controlled welding systems. It defines terminology, outlines best practices for measurement, and supports compliance with related welding procedure qualification standards.
Arc energy - also known as welding “heat input” - is a critical parameter for assessing weld integrity, determining the properties of weld metal and heat-affected zones, and ensuring safety and performance in welded structures. By standardizing measurement techniques, EN ISO 18491 helps industry professionals avoid errors that can arise from inconsistent energy determination practices.
Key Topics
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Arc Energy Definition and Calculation
- Explains the concept of arc energy per unit length
- Provides methods for calculating arc energy using current, voltage, weld speed, or instantaneous power/energy values
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Measurement Methods
- Method A: Calculation using welding current, arc voltage, and welding speed (suitable for traditional welding)
- Method B: Based on total instantaneous energy and the length of the run
- Method C: Based on average instantaneous power and welding speed (recommended for waveform-controlled welding)
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Parameters to Measure
- Arc voltage: Measured as close to the arc as practical, to minimize errors due to voltage drop in cables
- Welding current: Requires correct clamp meter placement for accurate results
- Weld run length and welding speed: Must be measured precisely for consistency
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Waveform-Controlled Welding
- Special considerations for modern power sources with complex waveforms that affect measurements
- Guidance on suitable methods and measuring equipment for these systems
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Calibration and Validation
- Mandates regular calibration and validation of measuring devices, referencing ISO 17662
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Conversion Factors
- Provides information on converting between different energy units (J/mm, kJ/cm, etc.) for international usability
Applications
EN ISO 18491:2026 is essential for:
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Welding Procedure Qualification
- Ensures accurate measurement of arc energy as required by standards like ISO 15614 during procedure qualification
- Supports the calculation and documentation required for Welding Procedure Specification (WPS) and Welder Performance Qualifications (WPQR)
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Quality Control in Welding Production
- Enables weld inspectors and quality managers to verify that welding energies in production match those qualified in test pieces
- Reduces risk of safety or quality issues caused by measurement inconsistencies
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Equipment Selection and Maintenance
- Guides the selection of appropriate measurement devices and technologies for both conventional and advanced welding systems
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Training and Compliance
- Serves as a reference for training welding personnel on best practices for energy measurement
- Assists organizations in demonstrating compliance with international best practices and regulations
Related Standards
- ISO 4063 - Nomenclature of welding and allied processes
- ISO 17662 - Calibration, verification and validation of welding equipment
- ISO/TR 17671 - Welding of metallic materials
- ISO/TR 25901 (parts 1, 3, and 4) - Welding and allied processes vocabulary
- IEC 60974-14 - Arc welding equipment: Calibration and validation
Conclusion
EN ISO 18491:2026 is a key reference for professionals in welding engineering, quality management, and inspection who seek reliable, standardized methods of measuring arc energy. Accurate calculation and documentation of arc energies is fundamental for producing high-quality, safe, and regulation-compliant welded assemblies across manufacturing, construction, and maintenance industries.