Published on 01-Mar-2024

Ultrasonic Testing Procedure: Explained Step-By-Step

Ultrasonic Testing Procedure: Explained Step-By-Step

Table Of Contents

  • What is Ultrasonic Testing?
  • Why is a procedure required for UT?
  • How to make an Ultrasonic Testing Procedure?
  • Basic Requirements for Ultrasonic Testing
  • Important Terms in Ultrasonic Testing
  • Surface Preparation in Ultrasonic Testing NDT
  • Equipment for Ultrasonic Testing and Ultrasonic NDT
  • Ultrasonic Testing Procedure
  • Key Takeaways

What is Ultrasonic Testing?

Ultrasonic Testing is the process of detecting internal defects by the use of high-frequency sound waves that are non-audible to human ears.

The method can be used to detect flaws inside any solid material.

Ultrasonic testing (UT), a vital facet of non-destructive testing (NDT), is an advanced technique employed for the evaluation of materials and structures.

It plays a pivotal role in ensuring the integrity and quality of various components and is used across a diverse range of industries.

UT involves the transmission of high-frequency sound waves through a material, making it a key player in the field of ultrasonic NDT.

The history of Ultrasonic Testing can be traced back to the early 20th century when scientists and engineers began exploring the principles of sound wave propagation and its potential applications in materials testing, including ultrasonic inspection.

In its nascent stages, ultrasonic testing was developed primarily to inspect metals, especially in the context of metallurgy and the burgeoning aviation sector.

The pivotal point in the history of ultrasonic testing came during World War II when it emerged as an indispensable tool for assessing the structural integrity of aircraft components.

Its ability to detect hidden defects that could compromise safety made it a critical asset, leading to its widespread adoption and application.

Ultrasonic testing has evolved significantly over the years, with advancements in equipment, techniques, and software, reflecting the broader realm of ultrasonic NDT Testing.

In contemporary times, it is employed in a myriad of industries, spanning manufacturing, construction, and the oil and gas sector, to ensure the safety, quality, and reliability of crucial components and structures.

The procedure for Ultrasonic Testing entails the generation of high-frequency sound waves using a transducer, which is then directed into the material under examination.

As these sound waves propagate through the material, they encounter boundaries between different media or internal flaws, subsequently reflecting the transducer.

Expert technicians analyze the time it takes for the sound waves to return and their amplitude, allowing for precise determination of the size, location, and nature of any discontinuities within the material.

Ultrasonic testing, ultrasonic inspection, and ultrasonic NDT are versatile and indispensable tools in the field of NDT, enabling the detection of a broad spectrum of flaws, including cracks, voids, and inclusions, all while being non-invasive and highly accurate.

The historical development and continuous evolution of ultrasonic testing underscore its critical role in the quest for enhanced safety and reliability across a multitude of industries.

Why is a Procedure required for Ultrasonic Testing?

Any industrial operation requires a work instruction or working procedure.

When it comes to special techniques like Non-destructive testing (NDT), it is essential to have an approved procedure.

They have references from any of the international standards.

A few of the global inspection standards for Ultrasonic Testing are given below:

  • ASME Boiler & Pressure Vessel Code – Section V
  • BS EN ISO 17640 (British & ISO Standard)
  • SAE AMS 2630, SAE AMS 2632 – (Aero Space Standards)

The significance of a well-defined procedure in ultrasonic testing cannot be overstated:

  • Consistency:

Procedures ensure consistent testing, minimizing human error and reducing variability in results.

  • Safety:

Proper procedures incorporate safety guidelines to protect operators and equipment during ultrasonic examination.

  • Standardization:

Following established procedures helps maintain uniformity and compliance with industry standards and regulations.

  • Quality Assurance:

Procedures enable the accurate detection and documentation of flaws, ensuring the quality and reliability of materials and structures.

  • Training:

Procedures are valuable training tools for technicians, guiding them in understanding and implementing best practices in ultrasonic NDT Testingand ultrasonic examination.

How to make an Ultrasonic Testing Procedure

A Procedure should contain the below important contents.

  • Scope (What is the range, material, type of material or weld joint the procedure covers, and technique)
  • References (the International or local Standards that the procedure refers to)
  • General Requirements

        1. personal qualification,

        2. requirement equipment capacity,

        3. Search unit size and frequency (Probe)

        4. Couplant

        5. Calibration standards /reference standards

  • Inspection Procedure
  • Evaluation of Indications
  • Acceptance Criteria
  • Documentation & Report format 

In general, a procedure should state all the essential variables given in the standards. Given here the essential variable requirement as per ASME section V Article 4

Ultrasonic Testing procedure

The developed procedure will be more informative if it has a scanning sketch attached to it. Here is an example of a scanning sketch:

Basic Requirements for Ultrasonic Testing

  • Ultrasonic Testing Equipment:

Essential equipment includes an ultrasonic flaw detector, transducers (or probes), and a couplant.

The flaw detector generates and receives ultrasonic waves, while transducers emit and receive the waves, and the couplant facilitates sound wave transmission.

  • Calibration Standards:

Calibration standards are crucial to ensure the accuracy of ultrasonic equipment.

These standards typically consist of known defects with precisely measured dimensions, serving as reference points for equipment performance evaluation in Ultrasonic Testing NDT.

  • Surface Preparation

Thorough surface preparation is vital to ensure accurate results.

The material's surface should be clean and free from contaminants that could hinder sound wave transmission.

  • Training and Certification:

Properly qualified personnel are essential for conducting ultrasonic testing.

Technicians must undergo training and certification to understand the principles, techniques, and best practices of UT examination and ultrasonic NDT testing.

Important Terms in Ultrasonic Testing

  • Transducer:

The transducer emits ultrasonic waves and receives echoes. It is a pivotal component of ultrasonic testing equipment.

  • Couplant:

A coupling medium, typically a gel or liquid, applied to the transducer to facilitate effective sound wave transmission between the transducer and the material under inspection in the ultrasonic examination.

  • Echo:

When an ultrasonic wave encounters a boundary or flaw within the material, it reflects back to the transducer, creating an echo.

The time and amplitude of these echoes are used to assess the material's condition.

  • Wavelength:

The distance between two successive points in a sound wave.

Wavelength is inversely proportional to frequency, meaning that higher-frequency waves have shorter wavelengths.

  • Frequency:

Ultrasonic waves are generated at specific frequencies.

The choice of frequency depends on the material's thickness and the nature of the flaw being inspected in ultrasonic testing work.

  • Velocity:

Velocity refers to the speed at which ultrasonic waves travel through a material.

Velocity is a critical parameter in calculating the material's thickness.

Ultrasonic Testing is a crucial NDT method for inspecting materials and structures.

Proper equipment, adherence to standardized procedures, and comprehension of key terminology are essential for achieving accurate and reliable results in UT.

A well-defined procedure is a cornerstone, ensuring consistency, safety, standardization, and quality assurance in ultrasonic testing work, ultrasonic examination, and ultrasonic NDT testing.

Surface Preparation in Ultrasonic Testing NDT

Effective surface preparation is a fundamental aspect of ultrasonic testing NDT, ensuring that reliable results are obtained during the ultrasonic examination process.

It plays a pivotal role in maintaining the integrity of non-destructive testing (NDT) and the overall quality of ultrasonic testing work.

Key factors include:

  • Clean Surface for NDT:

A clean surface is essential for accurate ultrasonic testing NDT.

The material being tested should be free from contaminants such as dirt, oil, rust, and paint.

These foreign substances can interfere with the transmission and reception of ultrasonic waves, affecting the reliability of the non-destructive testing procedure.

  • Surface Smoothness in Ultrasonic Examination:

The surface should ideally be smooth and devoid of rough or irregular areas that might scatter or attenuate sound waves.

This consideration becomes particularly critical when inspecting materials with complex geometries, underlining its significance in ultrasonic examination work.

  • Optimal Couplant Application:

Couplant, a specialized gel or liquid, is employed to enhance the transmission of ultrasonic waves between the transducer and the material.

Proper coupling application is a fundamental practice that ensures efficient contact and sound wave transmission in NDT ultrasonic testing and ultrasonic examination.

  • Addressing Surface Irregularities:

Surface irregularities, such as pitting or corrosion, should be assessed individually, as they can influence the interpretation of ultrasonic results.

The use of calibration standards with known defects can facilitate the evaluation of these irregularities, which is particularly important when working with various materials and flaw sizes in NDT testing.

Equipment for Ultrasonic Testing and Ultrasonic NDT

  • Search Units in Ultrasonic Testing Inspection:

Search units, commonly referred to as transducers or probes, serve as the heart of ultrasonic testing equipment in ultrasonic testing inspection.

They emit ultrasonic waves into the material and receive echoes in return.

These essential components come in various types, differing in frequency, size, and shape to cater to specific non-destructive testing applications, including ultrasonic testing NDT and ultrasonic examination.

  • Screen Height Linearity in NDT Ultrasonic Testing:

Screen height linearity is a critical parameter in the ultrasonic flaw detector.

It ensures that the instrument accurately displays the depth of flaws, a foundational element in ultrasonic NDT.

A reliable flaw detector with excellent screen height linearity provides precise depth measurements, an essential aspect of NDT ultrasonic testing.

  • Amplitude Control in NDT Testing:

Linguistics of amplitude control refers to the precise adjustment of ultrasonic signal strength and echoes during NDT testing.

This control is a vital consideration, as it allows for the detection of subtle indications by amplifying or reducing signal amplitudes.

It is especially pertinent when working with a variety of materials and flaw sizes in NDT ultrasonic testing techniques.

  • Couplant Use in Ultrasonic NDT Testing:

Couplant is an indispensable element of Ultrasonic Testing work, ensuring proper contact between the transducer and the material.

The selection of a couplant depends on the specific application and the material under inspection in NDT ultrasonic testing and ultrasonic examination.

Typical choices include gels, oils, and water-based solutions.

Ultrasonic Testing Procedure

  • Equipment Setup:

Assemble and calibrate the ultrasonic testing equipment, including the flaw detector and appropriate transducer (probe).

  • Surface Preparation:

Clean the material's surface, ensuring it is smooth and free from contaminants that could interfere with sound wave transmission.

  • Couplant Application:

Apply a suitable couplant to the transducer for efficient sound wave transmission.

  • Probe Placement:

Position the transducer on the material's surface, ensuring good contact for sound wave transmission.

  • Sound Wave Emission:

Emit ultrasonic waves into the material through the transducer, which propagates and encounters boundaries or internal flaws.

  • Echo Reception:

The transducer receives echoes generated when ultrasonic waves encounter boundaries or flaws within the material.

  • Data Analysis:

Analyze time-of-flight and amplitude of echoes to determine the size, location, and nature of defects.

  • Calibration and Reference Standards:

Use calibration standards for equipment verification and reference standards for surface irregularity assessment.

  • Adjusting Parameters:

Optimize equipment settings, including amplitude control, based on material thickness and defect type.

  • Recording and Documentation:

Record inspection results and relevant data for documentation.

  • Interpretation and Evaluation:

Interpret data to assess the material or structure's condition based on established criteria and standards.

  • Reporting:

Generate a detailed report summarizing inspection findings, including defect location, size, and depth.

  • Follow-up Actions:

Based on inspection results, take appropriate follow-up actions, such as repairs, further testing, or monitoring.

Adhering to a standardized procedure is essential to ensure the accuracy and reliability of the inspection process.


The procedure for performing Ultrasonic Testing is a meticulously orchestrated process that relies on advanced technology, precise techniques, and the expertise of trained professionals.

This non-destructive testing method, encompassing ultrasonic inspection and ultrasonic NDT, serves as a vital guardian of structural integrity and material quality.

From equipment setup to the interpretation of results, each step plays a pivotal role in unveiling the hidden secrets of materials and structures. 

Ultrasonic testing, a cornerstone of quality assurance and safety across various industries, underscores the importance of adherence to established procedures to ensure accuracy, reliability, and peace of mind in the ever-evolving world of NDT.

As a critical component of the broader field of non-destructive testing (NDT), ultrasonic testing inspection exemplifies the precision and rigor found in NDT techniques, ultimately contributing to the integrity and longevity of structures and materials in a myriad of industries.

Key Takeaways

  • Ultrasonic Testing is a non-destructive testing method that uses high-frequency sound waves to inspect materials for hidden flaws without causing damage.
  • The process involves transmitting ultrasonic waves into the material, receiving echoes or reflections, and analyzing the data to detect and characterize defects such as cracks, voids, and thickness variations.

Tree PNG back


Tree PNG back




Tree PNG back


Application Notes


onestop ndt application

NDT Trends #83 is out!!
Grab your FREE copy now.