ISO 20601:2018

Overview

ISO 20601:2018 - "Non-destructive testing of welds - Ultrasonic testing - Use of automated phased array technology for thin-walled steel components" defines how to apply phased array ultrasonic testing (PAUT) to fusion-welded, full-penetration joints in thin-walled steel parts. The standard targets components with wall thicknesses between 3.2 mm and 8.0 mm (typical boiler tubes), and covers both semi‑automated and fully automated phased array inspections for plates, tubes, pipes and vessels made from low-alloy or fine‑grained steels.

Key technical topics and requirements

• Testing scope and limitations: Applies to simple geometry, full-penetration welds in low-alloy/fine‑grained steel. Specifies that different material sound velocities must be considered; default values used in the standard are longitudinal 5920 ± 50 m/s and transverse 3255 ± 30 m/s.
• Testing levels: Defines two levels - level “C” (standard situations) and level “D” (special/different situations) with guidance on when to apply each.
• Assessment methods: Provides procedures for discontinuity evaluation based on height & length, amplitude (equivalent reflector size) & length, and go/no‑go decisions. The standard does not prescribe acceptance criteria.
• Equipment, probes and verification: Includes requirements for PAUT instruments, probe characterization, scan mechanics, reference blocks and calibration, and verification of test setup and sensitivity.
• Procedure development and checks: Addresses pre-test information, written test procedures, range/sensitivity settings, pulse‑echo time windows, scan increments, environmental considerations (temperature, couplant), and equipment checks.
• Personnel and data: Refers to personnel qualifications and competence, data storage, phased array image interpretation and analysis, and reporting requirements.

Practical applications and users

ISO 20601:2018 is practical for:

• NDT engineers and technicians performing automated phased array inspections
• Welding inspectors and quality assurance teams in boiler, pressure vessel, pipe and tube fabrication
• Power generation, petrochemical, and industrial maintenance organizations conducting pre‑service weld testing and repair verification
• NDT equipment manufacturers and system integrators developing PAUT solutions for thin‑walled steel components

PAUT under ISO 20601 is used as a stand‑alone or complementary NDT method to detect, locate, size and characterize weld discontinuities during manufacturing, installation and pre‑service inspection.

Related standards (useful references)

• ISO 17640 - Ultrasonic testing of welds: techniques and assessment
• ISO 18563 (Parts 1–3) - Characterization and verification of phased array equipment
• ISO 9712 - Qualification and certification of NDT personnel
• ISO 5577 and EN 16018 - Ultrasonic testing terminology

Keywords: ISO 20601:2018, phased array ultrasonic testing, PAUT, thin-walled steel, weld inspection, NDT, boiler tubes, automated ultrasonic testing.