A real-time and online corrosion monitoring system that provides reliable wall thickness data is presented. The system has monitored a weld for four years on a wet gas pipeline, and the operator has used this data as part of their risk-based integrity management strategy. The monitoring system is based on the well-established ultrasound pulse-echo technique. As the sensors are installed directly on the pipe outer wall, and measure wall thickness as a function of time, it provides high resolution data on material wall loss and corrosion rate. The system is modular in terms of number of sensors, and the ultrasound sensors can be installed in a ring on straight pipe, on top of the weld, or any matrix that the operator finds necessary to obtain sufficient information about the corrosion mechanisms.
We present field data and correlate with flow rates and flow temperature to demonstrate the strength of the systems performance.
Pipeline integrity management and practices have been systemized through standards(1), and one important aspect in integrity management is corrosion monitoring. Corrosion monitoring by using permanently installed equipment has increased in the past years(2). By using permanently installed ultrasound transducer (UT) sensors and automating signal processing and communication, a more cost-efficient corrosion management program can be obtained. Ultrasound techniques have been developed to complement traditional inspection with monitoring to improve cost efficiency of pipeline integrity management. Permanently installed ultrasound sensors can be retrofitted without interfering with production, which leads to a low threshold for using this type of equipment. It has low costs involved, and with an easy installation procedure the effort of installing this kind of equipment is low. In addition, retrofitted ultrasound sensors can be a substitute for corrosion monitoring by corrosion coupons and corrosion probes, as these intrusive techniques pose risk to HSE, increased work and planning. There are several publications discussing how corrosion monitoring should be performed in the most efficient way(3), (4).