Innovative Application of Ultrasonic Thickness Gauge with Low-frequency Probe in 100℃ PE Material

In the field of industrial testing, there has always been a technical bottleneck in the thickness measurement of high-temperature polyethylene (PE) materials. Traditional contact measurement methods are affected by material thermal expansion and surface deformation, while conventional ultrasonic testing faces problems such as changes in sound velocity and signal attenuation in high-temperature environments. This article combines practical cases to systematically explain the technological breakthrough of ultrasonic thickness gauge combined with dedicated low-frequency probe in 100 ℃ PE material testing, providing innovative solutions for non-destructive testing under special working conditions.

Technology Principle and Device Characteristic

The ultrasonic thickness gauge achieves thickness measurement by emitting pulse waves and receiving bottom echoes, with the core being the matching of probe frequency and material properties. For high temperature PE materials at 100 ℃, low-frequency probes below 2.5MHz are required, which have three major technical advantages:

1.Penetration enhancement: Low frequency ultrasound (0.5-2.25MHz) reduces attenuation coefficient by 30% -40% in high-temperature polymers, effectively penetrating 120mm thick PE sheets.

2.Thermal stability optimization: The specially designed probe chip uses high-temperature resistant piezoelectric ceramics, which can maintain sound velocity stability (error<0.1%) in an environment of 150 ℃.

3.Rough surface adaptation: The spherical contact surface design, combined with high-temperature coupling agent, can adapt to workpieces with surface roughness up to ± 2mm.

As it is shown in the picture,the color screen displays the A-scan waveform and the thickness values(in the range of 118-120mm), set the Gain to 50dB.

The Key Points of Detect Process

1.Preparation temperature compensation calibration: The instrument has a built-in temperature compensation curve, and the sound velocity decreases at 100 ℃ compared to room temperature. It needs to be corrected through software temperature compensation.

Apply coupling agent: Use high-temperature resistant coupling agent to better propagate ultrasonic waves into the tested PE material.
Probe selection: For the high attenuation of PE material, contact probes are preferred to enhance the penetration of ultrasonic waves

2. Detection and implementation of coupling monitoring: Determine the coupling status through changes in waveform amplitude on the display screen, with the green baseline representing ideal coupling
Multi point measurement: Conduct 9-point grid detection within a 300 × 300mm area, with standard deviation controlled within ± 1.2mm
Data recording: The device records thickness measurement data and supports real-time transmission to PLC or computer via WIFI/485/235, etc.

Technical Application Case

In the tank renovation project of a certain chemical enterprise, this technology was used to detect the PE lining during operation:
Operating conditions: Tank temperature of 105 ℃, lining thickness of 115mm, surface roughness Ra3.2.
Detection efficiency: Single point measurement time<3 seconds, complete detection of 10 ㎡ area takes 45 minutes.
Result verification: Compared with destructive sampling, the error rate is less than 2%, which meets the ASTM E797 standard.