In-Line Inspection Techniques for “Non-Piggable” Liquid Pipelines

While in-line inspection tools have been around for many years, the primary focus for this technology has always been on long sections of mainline pipe. The recent increased attention on facility integrity, as well as US Department of Transportation (DOT) baseline assessment requirements, have made it necessary to develop inspection tools and techniques for pipelines that have previously been considered non-piggable. Within industry, the term non-piggable has been used to describe pipelines that cannot be inspected with traditional free swimming mainline inspection tools using standard launch and receive traps. Typical reasons for classifying a pipeline as non-piggable include: • No launch or receive facilities; • Mechanical design (number/type of bends, diameter changes, offtakes etc.); • Operating conditions (zero/low/high pressure, zero/low/high flow, type of product, pipeline cleanliness etc.). Within the Enbridge system, a lack of launch and receive facilities has been the main obstacle on laterals and delivery/receipt pipelines. However, mechanical design and operating conditions have been factors on certain pipelines. The preferred method to inspect these pipelines, whenever possible, is to use in-line inspection tools, as opposed to other options such as External Corrosion Direct Assessment (ECDA) or hydrostatic test. While inspecting these short sections of pipe has proven challenging, various in-line inspection tools and techniques have been developed to meet this requirement. This paper will discuss some of the challenges faced and different solutions that have been developed to successfully inspect these types of pipelines.