The transportation department of the United States considers mechanical damage as one of the most frequent causes of pipeline incidents. Dent defects are highly varied in terms of depth, shape, and size even before considering interacting defects such as gouges or corrosion. Traditional mechanical damage repair methods can be limited in their applicability; For example, metal sleeves can have difficulty aligning with the pipeline surface. Even sectional replacements can create additional issues due to requiring pipeline shutdown or having to divert the flow through a bypass.
Composite repair systems provide an opportunity to address mechanical damage in a different way. Many composites are applied directly to the pipe before solidifying and therefore can encompass odd geometries that arise from mechanical damage. Additionally, the composite fabric can be oriented to address specific load expectations. However, there currently exists virtually no guidance in the common repair standards on how composite repairs can be used to effectively address dents and other mechanical damage. This is especially true considering that the largest threat from dents are due to how they affect pipeline fatigue life, not just short-term pressure burst restoration.
This article will address some of the significant testing programs that have been completed utilizing composite repair on mechanical damage and will analyze their performance in short-term burst pressure restoration as well as long-term cyclic fatigue capacity. A simplified design methodology will also be discussed as a bases for future composite repairs on dents.