Pipeline inspection: following hundreds of kilometres from the air, every day

Pipeline failures fall into a few families: third-party damage (excavation and heavy equipment striking the pipe), corrosion (external, from coating damage and failing cathodic protection; internal, from water, hydrogen sulphide and the like), ground movement (landslides, subsidence, frost heave or thawing permafrost, river scour exposing the pipe), and material or weld defects such as stress corrosion cracking. The difficulty is that any of them can occur anywhere along hundreds of kilometres.

Pipeline inspection works on two fronts: from inside the pipe and from above it. Inside, in-line inspection (ILI) tools — “smart pigs” — travel with the flow and measure wall loss and dents magnetically or ultrasonically. Above, ground and aerial patrols look for changes on the right-of-way, cathodic protection surveys check that the anti-corrosion current is flowing properly, and leak surveys search for escaping gas.

The pain is frequency versus distance. Activity on the right-of-way can start and finish within a day, but the longer the line, the wider the gaps between patrols. In North America manned aerial patrols are common, yet flying low for hours is itself dangerous work for pilots.

Pipeline drones split into long-range aircraft and spot-check aircraft. Long-range aircraft follow the line beyond visual line of sight looking for change. Spot-check aircraft fly to river crossings, valve stations or reported anomalies and look closely.

Line monitoring should not rely on drones alone. Satellites see broad and shallow (subsidence, large changes), drones narrow and deep (identifying equipment, methane concentration), and people do the final confirmation. Layering their strengths is the most realistic design today.

For pipelines the obstacles are not tight spaces or darkness but distance and weather. Long flights over open ground and ridges take the full force of the wind; Arctic sections bring icing and weak batteries; deserts bring heat and sand. In Japan many pipelines run under roads, so flights pass over people and traffic.

• Wind & turbulence: headwinds change fixed-wing range dramatically. Budget battery margin for both legs. Wind & turbulence
• Cold & icing: battery capacity drops and ice builds on props and wings. Use cold-rated aircraft and decide go/no-go from icing forecasts. Cold & icing
• Heat: in deserts batteries and motors run hot. Choose the time of day and protect against sand. Heat
• Urban areas & people below: inspecting gas mains under roads means flying over people and vehicles; plan permissions and safety measures accordingly. Urban areas & people below

Imaging hundreds of kilometres every day produces more pictures than anyone can review, so change detection is AI’s main job on pipelines: equipment has appeared near the pipe, soil has been disturbed, methane has risen. Only those reportable changes go to people. Deciding whether to stop the work, dig to verify or reduce pressure remains the operator’s responsibility.

Japan has relatively few long-distance pipelines. City gas mains fall under the Gas Business Act and oil pipelines under the Petroleum Pipeline Business Act (the jet fuel line to Narita Airport is a well-known example), each setting a safety framework within which operators carry out patrols and inspection. Because most Japanese lines run under roads and through towns, coordinating with excavation works matters more than aerial patrol.

Flights that follow a line are almost always beyond visual line of sight (BVLOS). Japan introduced a framework for BVLOS over populated areas (Level 4) in December 2022, and in December 2023 a simplified “Level 3.5” process for BVLOS over unpopulated areas. These are the foundation for long-line patrols.

Abroad, the US Pipeline and Hazardous Materials Safety Administration (PHMSA) requires right-of-way patrols under federal regulations, while aviation rules to normalise BVLOS are being developed. Canada relies on the Canada Energy Regulator (CER) and the CSA Z662 standard; in Europe, flights are risk-assessed under EASA’s specific category. Compare countries in world regulations.

• Corrosion on buried pipe: wall loss underground is invisible from the air. It needs ILI, cathodic protection surveys or excavation.
• Reliably finding small leaks: gas dispersed by wind, or liquid hidden by snow or soil, can escape airborne detection.
• Stopping the excavator: a drone can spot it, but people must go and stop it. Without a reporting and dispatch process, detection is meaningless.
• Patrols in bad weather: strong wind, icing and poor visibility ground the aircraft. Decide in advance how those days are covered.
• Long-range patrol without BVLOS approval: without the regulatory process and an operating organisation in place, long lines cannot be flown.
• Decisions and accountability: integrity assessment, pressure reduction or shut-in, and regulatory reporting stay with people.

Drone ports stand every few dozen kilometres along the line. At dawn an aircraft lifts off, follows the pipe to the next port and lands. When an excavator appears a few metres from the pipe, the image reaches both the operator and the contractor within minutes, and the phone rings before the bucket hits the ground.

Methane levels become a daily map, overlaid on in-line inspection results on the same screen, and the data says where to dig. That is our editorial view — and we expect measuring buried pipe walls will still fall to pigs and human hands even then.