Gas leaks pose a severe health hazard to people, have a negative impact on the environment and can also be extremely costly if not detected quickly. It’s no surprise then to see an upswing in drones, or unmanned aerial systems (UAS), being used to detect and give real-time evaluation of leaks at a safe distance before sending in a team on the ground, minimising risk and maximising efficiency.
Using a drone not only removes humans from potentially dangerous situations, but they can move quickly and unimpeded across large areas and can carry sensors that are so sensitive that they can detect multiple gases in tiny concentrations while flying at a distance.
Many gases are lighter than air, meaning that indoors they can rise and concentrate near the ceiling. Therefore, detection carried out by people on the ground may not achieve the most accurate results. Drones can reach these heights to measure accurately. Below are profiles of some of the systems on the market.
Craig O’Neill, director of business development at Teledyne FLIR, says: “For optical gas imaging (OGI), we use specialised infrared detectors that are filtered for specific chemical compounds of interest. In the case of oil and gas applications, our partner – Workswell – has created the GIS-320, an OGI payload for UAS, unmanned ground vehicles, and mobile platforms.”
The GIS-320 features a Teledyne FLIR cooled thermal imaging detector designed to detect hydrocarbon gases, methane and volatile organic compounds. When mounted on a suitable UAS, it provides a way to visually detect hydrocarbon emissions in the same way as do handheld OGI cameras.
O’Neill adds: “FLIR is the only OGI camera manufacturer that offers certification training and online fundamental training for OGI through the Infrared Training Center. The technology is easy to use, but training is recommended to fully understand OGI and to more accurately diagnose leaks and/or to identify false positives.”
Based in Croatia, AIR-RMLD provides a gas leak detection by drone service. Its solution is a 560g payload, which includes an RGB camera, GPS and tunnel diode laser technology, mounted on a DJI Matrice 210 UAV.
CEO of AIR-RMLD, Milan Domazet, says: “We fly the drone 20-30 metres above pipelines. The laser can detect methane gas from 50m with around 99% accuracy. The sending beam at 580nm reflects back into the collector lenses and the change in the valent linearly approximates to the ppm (parts-per-million).
“This is not new technology, but it’s not used often because it’s not cheap, especially in handheld applications. But when you put it on a drone it’s OK because you can cover more ground faster.”
The company’s proprietary software uses GPS to mark the position of leaks and allows operators to filter out any readings below or above a certain ppm. The drones usually fly between 20-25 minutes. The software can stitch together the videos and data captured by multiple flights to get a complete overview of the area being surveyed.
“Our record is around 55km in a day, but around 40km per day is normal,” Domazet adds. AIR-RMLD’s services can currently only be provided within 1,000km of its headquarters in Zagreb, but he has had several enquiries from the Middle East and South America, so a training plan is being put in place for customers who are further afield.
Next for the company is rust detection and inspection on oil pipelines. Domazet says that in around 30% of oil leak cases methane leakage also occurs. With a combination of laser technology, multi-spectral, thermal and RGB cameras which use AI and machine learning, the company can detect rust on the pipelines easily and with high accuracy. It is testing the technology in one ongoing project.
ABB has recently launched HoverGuard, which it calls the world’s fastest, most sensitive drone-based gas leak detection and greenhouse gas measuring system.
HoverGuard detects, quantifies, and maps leaks up to 100m away from possible natural gas sources, including distribution and transmission pipelines, gathering lines, and storage facilities. It automatically generates comprehensive digital reports that summarise results and can be shared in minutes after a survey (pictured). HoverGuard can be fitted to drones that can carry a payload of 3kg.
In addition to methane, it can also quantify carbon dioxide and water vapour continuously while flying. Patented cavity enhanced laser absorption spectroscopy detects methane with a sensitivity more than 1,000 times higher and over 10 times faster than conventional leak detection tools. it says. This sensitivity and speed allows HoverGuard to detect, locate, and quantify the size of leaks while flying at altitudes of 40m and at speeds greater than 88kmph.
HoverGuard works by continuously sampling local air through an onboard analyser based on ABB’s cavity enhanced laser absorption spectroscopy technology. ABB’s FastScanner software incorporates these measurements of gas concentrations with local wind velocity into detailed fluid dynamics models to estimate the origins and sizes of leak emissions sources.
“The accuracy and the precision of the measurements is related to the product of the optical path length times the concentration,” Baer explains: “In traditional closed-path methods, you’re limited by a small path length, and thus suffer from low sensitivity. In conventional open-path methods, only path averaged measurements of column density can be reported. In contrast, our technology provides extremely long and well-characterised optical path lengths which enables us to report accurate measurements of gas concentrations with extraordinary precision.”
HoverGuard displays results on geospatial maps (Google or Microsoft Azure) and colour-codes them depending on the size and localisation of the leak source. The system is said to be able to detect a 0.5 litre per minute leak rate, roughly the amount produced to keep a pilot light lit, from a source 40m away.
ABB sells HoverGuard as well as offers it as a service in the US. Baer says a modest amount of training is suggested, but not required; the instruments are designed to operate and begin making measurements by the push of a button. But a registered pilot is required by the US FAA to fly the drone within line of sight.
Mark Fishburn, global key account manager at Teledyne FLIR, says: “Flight safety is paramount. Before each flight, a briefing makes the pilot and team aware of utility lines, roads that can or cannot be flown over, distances that need to be kept around assets, and air traffic radio is monitored for incoming private aircraft. The UAS pilot also needs to be well versed in OGI to be able to identify leaks versus steam or other anomalies.”
Domazet adds that one of the most important things potential customers must have in place for a good, fast and accurate inspection is “good GIS [geographic information system] data. If we have to record it, it extends the time taken by three times.”
Baer says that using drones to inspect plant and pipelines is simply quicker and cost-effective. But “a-number-one is safety; you want to find a leak fast, or inspect on a regular basis, to ensure there’s never a large leak because, sometimes, you can’t smell a leak until it’s too late.”