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Identifying lack of fusion defects in high-density polyethylene piping welds

In this paper, microwave testing technique for identifying lack of fusion defects in thermal fusion weld of high-density polyethylene (HDPE) pipeline is proposed. HDPE piping thermal fusion welds with lack of fusion defects of different degrees were examined using a vector network analyzer and a self-designed microwave measuring system with a success. At a frequency that was most sensitive to the lack of fusion defects, the measured reflection coefficient S11 and voltage standing wave ratio (VSWR) had significantly different values between the good weld and those containing lack of fusion defects. The readily detectable differences in S11 and VSWR make identification of the lack of fusion defects possible. True density experiment and scan electron microscopy were conducted to confirm the reliability of the microwave testing methods. This work provides great insights into inspection of technical defects in HDPE piping welds.