A North American operator required an inspection of a liquid propane line critical to the company’s business. Liquid propane is an extremely difficult environment for conventional ultrasonic inline inspection (ILI) methods. The medium’s volatility can cause variations in sound velocity from 1,520 mph (680 m/s) to as high as 2,235 mph (1000 m/s), depending on pipeline pressure and temperature. This large swing degrades the accuracy of ordinary tools and can render them ineffective. The pipeline’s nominal 6" ID and thin walls were further constraints.