Performance of a Guided Wave Pipe Monitoring System Over Extended Periods of Field Operation

The performance of a permanently installed guided wave pipe monitoring system over extended periods has been investigated. Other than at a clamped support, the signals obtained in the three installations reported here have been stable to better than 1% (–40 dB) over periods of 12–24 months, even in hostile oil and gas facility environments. The use of baseline subtraction means that the sensitivity to defects is substantially better than that obtained in one-off inspection; in the two site examples reported here, improvements of 7 and 12 dB relative to one-off interpretation of the A-scan signal were obtained, and changes can be flagged automatically. The improvement in sensitivity is even larger at features such as welds and bends, which give significant reflections even in the absence of damage. The permanently installed system combines long-range guided wave monitoring for localized corrosion patches with eight precise thickness measurements around the pipe circumference, making it possible to monitor the general wall loss rate, as well as detect any more severe, localized corrosion. Permanently installed guided wave monitoring systems are therefore found to be a commercially attractive tool for the assessment of current and future piping integrity.