Location

Snowmass Village, CO

Start Date

1-1-1995 12:00 AM

Description

Ultrasonic inspection is a standard method to assess the integrity of large-diameter oil pipelines. However, similar methods applied to natural-gas pipelines present a considerably greater challenge; gas is a poor coupling agent for the probing ultrasonic signals between the transducer and the pipe wall. Natural gas exhibits a very low specific acoustic impedance (300 Rayls for methane at atmospheric pressure) compared to oil (1.5 MRayls and higher). Consequently, large ultrasonic-signal transmission losses occur at the transducer/gas and pipe-wall/gas interfaces. To circumvent this obstacle, past exploratory developments included the use of a liquid-filled wheel [1], electromagnetic-acoustic-transducer (EMAT) [2], and liquid-slug technologies [3]. While prototypes of high-speed, in-line inspection systems employing such principles do exist, all exhibit serious operational shortcomings that prevent widespread commercial exploitation.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

14A

Chapter

Chapter 4: Transducers, Sensors, and Process Control

Section

Ultrasonic Transducers

Pages

951-958

DOI

10.1007/978-1-4615-1987-4_120

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Gas-Coupled, Pulse-Echo Ultrasonic Crack Detection and Thickness Gaging

Snowmass Village, CO

Ultrasonic inspection is a standard method to assess the integrity of large-diameter oil pipelines. However, similar methods applied to natural-gas pipelines present a considerably greater challenge; gas is a poor coupling agent for the probing ultrasonic signals between the transducer and the pipe wall. Natural gas exhibits a very low specific acoustic impedance (300 Rayls for methane at atmospheric pressure) compared to oil (1.5 MRayls and higher). Consequently, large ultrasonic-signal transmission losses occur at the transducer/gas and pipe-wall/gas interfaces. To circumvent this obstacle, past exploratory developments included the use of a liquid-filled wheel [1], electromagnetic-acoustic-transducer (EMAT) [2], and liquid-slug technologies [3]. While prototypes of high-speed, in-line inspection systems employing such principles do exist, all exhibit serious operational shortcomings that prevent widespread commercial exploitation.