Probe Selection for Ultrasonic Testing: Best Practices

Selecting the correct probe is the first step taken when starting an ultrasonic inspection. Probes generate and receive high-frequency sound waves that are then used to map the interior of objects. This allows nondestructive testing (NDT) technicians to gauge material thickness and identify flaws.

For most NDT applications, probe criteria have been established by relevant standards, regulations, or company policy. So, probe selection for ultrasonic testing comes down to consulting the right authority. For uncommon or novel applications, probe selection should be guided by a sound understanding of the inspection application challenges and requirements. Technicians should consider acquiring custom probes from an experienced NDT supplier. 

Consulting Relevant Standards for Ultrasonic Probe Selection 

Probes vary primarily by size, frequency, and other features. Many different configurations exist, and the wrong probe will not return the right results. Selecting the right probe should not be left to guesswork.

Most NDT applications are performed at the behest of the equipment or asset’s manufacturer. They, in turn, can make testing recommendations based on government regulations, company policy, or standards developed by international testing organizations. To find the right probe for an application, talking with a probe supplier or NDT equipment manufacturer is highly recommended.

The law is king, and meeting compliance regulations on probe selection are the highest authority. However, regulations for specific testing applications can vary from nation to nation, and possibly even within nations. In practice, the sheer number of potential applications and a variety of probes preclude detailed selection guidelines from being written into law in most cases. Rather, probe requirements are delegated to standards or recommendations usually developed by NDT experts. Still, it’s important to consult with industry experts to ensure that all relevant regulations are met.

The asset manufacturer is more likely to prescribe specific probe sizes and/or frequencies for each application, especially for common, well-studied uses. Company policy, which could include specifications, should be consulted as well. These internal standards are more likely to specifically address the application in question.

If neither regulations nor company policy dictates any specific probe requirements, then searching for standards created by international standards organizations—such as the International Organization for Standardization (ISO)—is another option. 

Organizations like ISO are typically nongovernmental agencies dedicated to researching and publishing working standards for companies and governments. While their standards are nonbinding, they are developed by experts and proven reliable across the world. Often, standards found in either company policy or regulation were developed by one of these organizations, though they may be subsequently modified.

Whether or not the above resources are able to provide guidance for probe selection, discussing application parameters with an NDT probe or equipment supplier is highly recommended.

Probe Customization for Specific Ultrasonic Testing Applications 

Selecting a probe for an inspection application should not be taken lightly, as the guidelines established during initial experiments will take on a life of their own in years to come. If the guidelines are even partially incorrect, they can lead to accidents in the field when flaws go undetected.

Probe selection for ultrasonic testing should be pursued according to relevant guidelines or under the supervision of a Level III NDT technician. The final consideration, when procuring probes, is to choose a reliable, trusted supplier that can meet very specific needs with standard or custom solutions. Probes that only nominally meet specifications can provide a false sense of confidence. Probe suppliers with long, proven track records should be preferred. 

Zetec has a long history as a leading provider of ultrasonic testing equipment and software. We have the experience and expertise to supply exactly the probes you’re looking for. To learn more, contact us today!