In-line inspection (ILI) of pipelines used to transport anhydrous ammonia is challenging since several components that make up a typical inspection tool are not compatible with anhydrous ammonia. MFL and Deformation tools were developed in the past to assess anhydrous ammonia pipelines for corrosion and deformation anomalies. However, assessing for crack type anomalies has never been possible as no ammonia compatible ultrasonic ILI tool was developed. Operators of these pipelines have conducted ultrasonic  inspections using water to navigate the tool through the line during hydrotesting. This process is expensive and it causes months of interruptions in flow due to repairs and other factors related to the procedure. The opportunity to conduct ultrasonic (crack) inspections during normal operation of the pipeline system results in significant savings. 

A main threat in the development process was the design of robust ultrasonic probes. The aggressive nature of ammonia, especially to plastic materials, and the two-phase states of ammonia (fluid and gaseous), meant that conventional probes to inspect pipelines proved unsuited. Therefore, the goals of the development were to find ammonia resistant materials, design a fully enclosed, gas tight housing, and build UT probes ensuring optimized acoustic characteristics to deliver high resolution UT data during an ILI run. After various iterations a final probe specification was released and verified in laboratory and on-site testing in a launcher and in a section of ammonia pipeline. Development of UT probes was carried out in cooperation with Sonotec.

The paper will report on the ILI inspection carried out on a section identified by the pipeline operator. The paper will present results from the qualification program and a more detailed set of results will be presented during the conference.