Robotic Non-Destructive Testing

Robotic non-destructive testing (NDT) is a method of inspection used to assess the structural integrity of petroleum, natural gas, and water installations. Crawler-based robotic tools are commonly used for in-line inspection (ILI) applications in pipelines that cannot be inspected using traditional intelligent pigging tools (or unpiggable pipelines).

Robotic NDT tools can also be used for mandatory inspections in inhospitable areas (e.g., tank interiors, subsea petroleum installations) to minimize danger to human inspectors, as these tools are operated remotely by a trained technician or NDT analyst. These systems transmit data and commands via either a wire (typically called an umbilical cable or tether) or wirelessly (in the case of battery-powered tetherless crawlers).

Robotic NDT tools help pipeline operators and utility companies complete required structural integrity data sets for maintenance purposes in the following applications:

Pipeline conditions that may prevent or hinder a flow-driven pig inspection include:

Robotic NDT tools also offer safety advantages in inhospitable areas:

Tethered robotic inspection tools have an umbilical cable attached to them, which provides power and control commands to the tool while relaying sensor data back to the technician. Tethered crawlers have the following advantages over untethered crawlers:

Tethered crawlers have the following disadvantages against untethered crawlers:

Untethered robotic ILI crawlers are powered by onboard batteries; these tools transmit sensor data wirelessly to the tool operator or store the data for downloading upon tool retrieval. Untethered crawlers have the following advantages over tethered crawlers:

Untethered crawlers have the following disadvantages against tethered crawlers:

Robotic NDT tools employ suites of inspection sensors. This section describes common sensor types; most tools combine several types of sensor depending on factors such as robot size, design, and application.

Main article – Electromagnetic acoustic transducers

Electromagnetic acoustic transducers (EMAT) induce ultrasonic waves into uniformly-milled metal inspection objects (e.g., pipe walls, tank floors). Technicians can assess metal condition and detect anomalies based on the reflections of these waves – when the transducer passes over an anomaly, a new reflection appears between the initial pulse and the normal reflection.

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