Foreword

In modern industry, the safe operation of piping systems is of paramount importance. As a weak link in the structure, internal defects in pipeline welds (e.g., cracks, pores, unfused, etc.) may lead to serious accidents such as leaks and explosions. Traditional visual inspection or radio-graphic testing (RT) can no longer meet the demand for high efficiency and high precision. Based on this, ultrasonic inspection technology has become the core means of pipeline weld quality control by virtue of its advantages of non-destructive, high efficiency and low cost. In this paper, the synergistic application of ultrasonic pulse generator, oscilloscope and probe in pipeline weld inspection will be introduced in detail.

Technique Principle

The core principle of ultrasonic inspection utilizes the propagation properties of ultrasonic pulses through the material. When the ultrasonic pulse passes through the probe into the weld under test, if it encounters a defect (e.g., a porosity or crack), part of the sound wave will be reflected, forming an echo signal. By analyzing the time difference, amplitude and phase of the echo, the location, size and nature of the defect can be determined.

Ultrasonic pulse generator: Generates high-frequency electrical pulses (usually 1-20 MHz) to drive the probe to generate ultrasonic waves.

Oscilloscope: Real-time display of the echo signal waveform for the inspector to analyze.

Probe: Converts electrical signals into ultrasonic waves and transmits them, and receives the reflected echoes at the same time.

Device Composition and Function

Ultrasonic Pulse Generator

Outputs adjustable high-frequency electrical pulses with controlled emission energy and frequency.

Supports multi-channel inspection and is suitable for complex weld structures.

Oscilloscope

Displays the time-amplitude curve of the echo signal (A-scan mode).

Equipped with signal amplification, filtering, storage and other functions, convenient for subsequent analysis.

Probe Type Selection

Straight beam probe: Vertical incidence, suitable for detecting flat defects inside the weld (e.g. delamination).

Angle beam probe: Incidence at a certain angle, suitable for detecting defects on the bevel and near surface of the weld (e.g. unfused).

Focused probe: improves defect localization accuracy, suitable for thin-walled pipes.

Auxiliary Equipment

Coupling agent: Reduce the air gap between the probe and the workpiece surface to ensure the effective transmission of sound waves.

Sweeping device: To realize the uniform movement of the probe and avoid human error in operation.

Measurement and Operation Points

Preparation before testing

Clean the weld surface of oil, rust and corrosion to ensure the coupling effect.

Select the appropriate probe frequency according to the pipe material and thickness (e.g. 2.5-5 MHz for steel pipes).

Calibration and Parameter Setting

Calibrate the equipment with a standard test block (e.g. CSK-IB test block) to determine the sensitivity and scanning speed.

Setting oscilloscope parameters: time base range (matching with pipe thickness), gain compensation (noise suppression).

Sweep and signal analysis

Bottom echo: If there is no bottom echo or the echo is weakened, there may be volumetric defects.

Defect echo: Calculate the equivalent size of the defect according to the height and position of the echo.

Sawtooth sweep along the vertical direction of the weld to ensure that the entire weld area is covered.