Clamp-On Narrow-Band Passive Ultrasonic Isolators for Enabling Non-Invasive Detection of Obstructions within Steel Pipeline

This work introduces a clamp-on narrow-band passive ultrasonic isolator that extends the gas density / pressure Pareto frontier for non-invasively polling the interior of gas-pressurized steel pipeline. The isolators enable an ultrasound-based approach for detecting obstructions within steel natural gas distribution pipeline with nominal operating pressures as low as 0 psig, which heretofore required either a radiographic or invasive approach. The ultrasonic isolators are machined using a copper alloy and potted in a grit-filled urethane compound. The isolators are complemented by in-house developed Lamb wave transducers and custom interface and signal processing circuitry and detection algorithms. The overall system is self-contained and highly portable for use in the field. Testing is performed in the lab using vented and methane-pressurized steel pipe, and in the field on live natural gas distribution pipeline.