NDT Ultrasonics Thickness Test

1. What Is Ultrasonic Thickness Testing?

Ultrasonic Thickness Testing (UTT) is a non-destructive testing (NDT) method used to measure the thickness of materials, such as metals, plastic, and composites, by using high-frequency sound waves.

It is widely used to assess corrosion, erosion, or wear in pressure vessels, pipelines, storage tanks, structural steel, and more — without cutting or damaging the component.

2. How Does It Work? (Basic Principle)

• A transducer (probe) sends ultrasonic sound waves into the material.

• The sound travels through the material until it reaches the back wall (opposite surface).

• The echo (reflected wave) returns to the transducer.

• The time it takes for the echo to return is used to calculate the material's thickness, using the formula:

Thickness = (Velocity × Time) / 2

The velocity is the speed of sound in the specific material (e.g., steel, aluminum).

3. Why Perform Ultrasonic Thickness Testing?

       Common Purposes:

• Detect material loss due to corrosion or erosion

• Evaluate structural integrity of pressure vessels and tanks

• Ensure compliance with safety standards (e.g., DOSH / JKKP in Malaysia)

• Determine if a component is safe for continued operation

• Provide input for repair or replacement planning

4. Testing Procedure (Simplified)

• Surface Preparation

            – Remove rust, paint, or debris from the test spot.

• Apply Couplant

• Measurement

  – Place probe on surface, take multiple readings, typically in a grid pattern.

• Recording Results

  – Log the thickness values, identify any readings below minimum allowable thickness.

• Interpretation & Reporting

  – Compare with design specifications, standards, or previous results.

5. Benefits of UTT

•  Non-destructive (no need to cut or drill)

•  Highly accurate

•  Quick and portable

•  Works on only one-side access

•  Suitable for in-service equipment

6. Regulatory and Compliance Notes (Malaysia)

In Malaysia, ultrasonic thickness testing is often required by law for:

• Pressure vessels (under the Factories and Machinery Act 1967)

• Boilers and air receiver tanks (DOSH / JKKP certified inspections)

• Occupational safety audits

 UTT must be performed by qualified NDT technicians, often certified under PCN, ASNT, or ISO 9712.

Ultrasonic Thickness Testing is an essential tool for monitoring material integrity and preventing unexpected failures. It ensures regulatory compliance, improves operational safety, and supports predictive maintenance.

Regular UTT checks can help detect hidden problems before they become critical, saving costs and lives.