Overwrap Damage and Liner Failure in Composite Overwrapped Pressure Vessels Measured Using Electromagnetic Inductive Coupling Analysis

In recent years, the lightweight nature of composite overwrapped pressure vessels (COPVs) has been adopted in multiple industries and Type II (hoop overwrapped, metallic lined) or Type III (fully overwrapped, metallic lined) vessels are becoming increasingly commercially available. These tanks are subject to various environmental stresses with corrosion of the metal (often aluminum) liner being a major cause of removal from service. Visual inspections are typically performed annually to ensure safe operation of these vessels by identifying various degrees of damage but are influenced by human error and subjective data interpretation, while also being a source of liability for inspection companies. An improved method for COPV damage investigation and periodic inspection is described here using the recently developed Electromagnetic Inductive Coupling Analysis (EMICA) technique to spatially characterize the presence of 6061 aluminum liner failure caused by corrosion damage, as well as repeated cyclic loading wear from lifetime pressure cycling in an otherwise “healthy” vessel. EMICA is a non-destructive evaluation (NDE) imaging technique that can provide information from both the aluminum liner and the outer CF overwrap of COPVs, while being measured from the outer surface. A discussion is provided for future steps to implement EMICA as an augment to visual inspection in order to lower COPV inspection liability by providing quantitative damage dimensions and pass/fail criteria.