Ultrasound Testing

Condition-monitoring technique · Updated 2026-07-15

Ultrasound testing detects the high-frequency sound that the ear cannot hear — emitted by early bearing faults, compressed-air and steam leaks, failing steam traps, valve leakage and electrical discharge. It often gives the earliest warning of all condition-monitoring techniques.

How it works

An ultrasonic detector picks up high-frequency sound and shifts it into the audible range, so a technician can hear faults that are otherwise silent. Because friction, turbulence and electrical discharge all emit ultrasound, the technique finds the very earliest stage of bearing wear, the hiss of a pressurised leak, and the flow through a passing valve or failed-open trap. It is fast, portable and needs no shutdown.

What the data shows

A rising ultrasonic level on a bearing is often the first sign of wear, before vibration; a continuous hiss locates a compressed-air or steam leak; flow noise through a closed valve reveals internal leakage; a failed-open steam trap shows continuous flow.

Ultrasound Testing in practice

Ultrasound Testing is versatile because it works across many asset types: bearings, steam traps, control valves and others. This breadth is both a strength and a consideration — a wide-ranging technique often requires less customization, but may not be as specialized as a dedicated point-solution. Most plants use Ultrasound Testing in combination with other techniques to build a complete condition-monitoring programme.

In practice: Ultrasound Testing excels at catching developing faults early, when they show as subtle changes in the monitored signal. The challenge is distinguishing a real fault signal from noise. Successful Ultrasound Testing programmes typically combine threshold alarms (alert if the signal exceeds a limit) with trending analysis (alert if the signal is rising fast, even if still below the limit). Both approaches matter for reliability.

Getting started: Implement Ultrasound Testing on your most critical assets first — those whose failure causes the longest downtime or highest cost. Start with one or two assets to learn the signals on your equipment and processes, then expand. Many plants find that Ultrasound Testing baseline data (what 'normal' looks like) takes 2–4 weeks to establish, after which the technique pays for itself through early fault detection.

Ultrasound Testing by equipment

Glossary: Ultrasound Testing →