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Full-Scale Coating Abrasion Test to Supplement Laboratory Testing


 Laboratory coating qualifications often require determining the ability of the coating to resist abrasion and gouging. These tests help inform a pipeline operator on the coating’s ability in extreme conditions, often those that may be required during a horizontal directional drill (HDD) when specifying an abrasion resistant overcoat (ARO) would be considered. However, these laboratory bench-top tests subject the coating to subscale loading that typically is not of the magnitude that can be experienced during pipeline construction.
 An HDD is a trenchless pipeline installation method where a pipeline is pulled through a pilot hole and is likely to increase in popularly over the coming decades as current pipeline right of ways become more congested and urban sprawl increases. As HDDs increase, their construction will be pushed to the extreme: longer distances, larger/heavier pipe, and through more challenging formations. Drilling through more challenging formations, such as granite, will subject additional abrasion and gouging to the pipe coating. Therefore, there remains a need to supplement traditional laboratory bench-top testing with a full-scale alternative that more closely represents the abrasion and gouging risk experienced during an HDD.
 This paper provides an overview of common subscale abrasion testing as well as the newly developed, innovative full-scale test. This full-scale test was designed to subject a pipe sample and ARO coating to varying obstructions pneumatically engaged against the outside pipe/coating surface. Obstructions utilized during this test development included: (1) a granite block selected to represent a natural formation, (2) a round tip selected to represent wear, and (3) carbide-tipped machining inserts selected to simulate aggressive gouging. Applying larger loads pneumatically to each obstruction simulates higher loading during an HDD — either due to a longer pull, heavier pipe, or variations in drilling mud/ballast. Finally, this paper will review industry accepted HDD load calculations providing a selection chart to determine the thickness of an applied ARO sacrificial overwrap.