What is Ultrasonic Testing (UT)? A Guide for NDT Firms

Ultrasonic testing (UT) is a non-destructive testing method that detects internal discontinuities in materials using high-frequency sound waves. It is widely used in aerospace, petrochemical, structural steel, and pipeline projects — and is the preferred method for both thickness measurement and flaw detection.

How does UT work?

In ultrasonic testing, a probe called a transducer is placed in contact with the surface of the material under test. The transducer sends high-frequency sound waves (typically 1–15 MHz) into the material. When the waves encounter internal surfaces, flaws, or material boundaries, they reflect back; these reflections are displayed on a screen as A-scan, B-scan, or C-scan images.

Key techniques include:

• Pulse-Echo: A single transducer both transmits and receives; the most common approach.
• Through-Transmission: Two separate transducers are placed opposite each other; sound transmission is measured.
• Phased Array UT (PAUT): A multi-element probe scans at multiple angles simultaneously; provides detailed imaging on complex geometries.

Which materials is UT used on?

UT is particularly suited to:

• Steel and metal alloys
• Welds (weld seam inspection)
• Pipe and tank wall thickness measurement
• Composite materials (with PAUT)

In coarse-grained or highly heterogeneous materials, sound scattering can limit UT results.

Standards used in UT inspection

Key standards referenced by NDT firms for UT in Turkey:

• ISO 17640 — Ultrasonic testing of welds
• ASTM E114 — Pulse-echo method
• ASME Section V — Pressure vessels and pipelines
• EN 583 — General UT technique series

Inspection bodies accredited under ISO/IEC 17020 are required to maintain valid technical procedures and quality documents for all UT activities.

UT personnel qualification

Personnel certification under schemes such as EN ISO 9712 or PCN is structured in three levels:

• Level 1: Calibration, scanning, and recording under supervision
• Level 2: Independent inspection, evaluation, and report writing
• Level 3: Procedure approval, technical management, methodology development

Tracking a UT technician's certificate validity is critical for both ISO 17020 compliance and TBDS requirements.

How NDT software simplifies UT work orders

UT inspections generate more data than most other methods: A-scan records, calibration documents, equipment serial numbers, environmental conditions. Collecting this data on paper is both error-prone and a risk in accreditation audits.

Good NDT management software provides:

• Automatic linking of method, standard, and procedure on the UT work order
• Certificate validity check when assigning a technician to a work order
• Equipment calibration status linked to the inspection date
• UT report generated from a standard template and automatically archived
• Filterable UT inspection record list for TÜRKAK audits

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