Researchers develop an autonomous gas leak detection robot

Detection of gas leaks in industrial facilities can not only be dangerous and time-consuming, but it is also susceptible to human error and interpretation. RoboGasInspector was conceived in order to provide a safer, more efficient and more reliable detection solution.

As part of the German technology program AUTONOMIK, a consortium of nine companies and research institutes developed a prototype of an autonomous mobile robot for gas leak detection and localisation in large industrial facilities. The consortium came up with a system that is able to perform inspection tasks in industrial facilities without having to access hazardous areas directly - and without requiring any human presence. The robot can be used for routine inspections of facilities or for targeted inspections of specific system parts.

The development of innovative monitoring processes that make the most of state-of-the-art measuring and automation technology as well as robotics promises improvement in the reliability, efficiency and cost-effectiveness of inspections. At the same time, it relieves technical personnel of monotonous, time-consuming and labour-intensive tasks.

The RoboGasInspector consists of three modules: a chain-driven mobile platform, a navigation module and an inspection module.

RoboGasInspector was the result of a collaborative research project headed by Dr Andreas Kroll and Dr Ludger Schmidt at the Mechanical Engineering Department of the University of Kassel and subsidised with €2.4 million from the German Federal Ministry of Economics and Technology.

Exercising the utmost care wherever toxic or explosive gases are used is absolutely essential, which is why rigorous inspection specifications apply to the chemical industry, biogas facilities and gas suppliers. Usually, preventive inspection programs require personnel to perform time-consuming routine inspection procedures on a daily basis.

During these regular inspections, staff members check the system for proper functionality and therefore they usually rely on perceptions and experience without making use of measuring technology. However, there is always a risk of inadvertently overlooking possible sources of danger due to inattention. The development of innovative inspection technologies and focusing the flexibility and performance of human operators on managing the technological systems makes sense not only for economic reasons, but also with regard to relieving humans from repetitive routine tasks and improving inspection coverage.

For professors Kroll and Schmidt, a top requirement for the new system was that it should allow for automated, hazard-free inspection and monitoring and that it should be able to respond independently to problems. The RoboGasInspector was demonstrated for the first time in a hall at the University of Kassel and independently completed an inspection route, successfully overcoming obstacles and a ramp in the process.

At specified inspection sites it inspected various pipelines and found a methane leak. In the following months, this success was expanded to several square kilometres of large industrial facilities under laboratory conditions in which environmental factors such as wind and sun as well as confounding factors resulting from system operation were included.

The multisensor inspection module: The pan-tilt unit (1) is equipped with a thermal imaging camera (2), an active TDLAS measuring device (3), a laser rangefinder (4), a video camera (5) and the FLIR GF320 thermal imaging camera for gas visualisation (6).The computer and other electrical/electronic modules are housed in a switching cabinet (7).

The RoboGasInspector consists of three modules: a chain-driven mobile platform, a navigation module and an inspection module, which incorporates a FLIR optical gas imaging camera. The chain-driven platform is equipped with an electric drive and conventional batteries.

The navigation module consists of 2D laser scanners (front and back, particularly important for navigation inside buildings) as well as a GPS receiver for outdoor orientation. Continuous comparison of the area to be inspected with a digital map enables the RoboGasInspector to determine its position at any time; obstacles and blocked areas (such as explosive zones) can be noted on this map.

“Thanks to its 2D laser scanners, the RoboGasInspector also avoids unexpected objects such as parked cars, pallets, barrels and people,” explained Professor Kroll. “If the RoboGasInspector encounters obstacles, it moves around them or stops until the path is clear again.”

The inspection module combines various metrological instruments on a pan-tilt unit, including a remote methane leak detector (RMLD), which is based on an active tunable diode absorption spectroscopy (TDLAS) instrument. It works by means of an infrared laser: when the laser beam hits a surface, it is reflected and its residual intensity is measured. In addition, a FLIR GF320 thermal imaging camera is mounted on the inspection module to visualise the gases and to help to detect gas leaks from a safe distance.

The FLIR GF320 displays invisible gases at leak sites as dark plumes of smoke.

To ensure that the RoboGasInspector itself does not pose a risk, it is also equipped with a built-in gas sensor that shuts down the entire system from 10% of the lower explosion limit (LEL) onwards in order to prevent possible danger in a flammable atmosphere.

Processing of the measured data and pattern recognition are performed independently by the robot. The RoboGasInspector also carries out the inspection of the specified routes and performs measurements on its own. Despite this, it is continuously in contact with the control room and can be remotely controlled from there if necessary. A video camera is also incorporated in the pan-and-tilt measuring module for this purpose. However, in normal operating mode, the RoboGasInspector works independently and merely transmits all measured data to the control room via WLAN.

The system prototype has impressively demonstrated its use and capability in extensive series of tests. The drive unit, the navigation system and the complementary sensor systems performed well during the tests. However, before deployment in industrial settings, further development is required, and of course legal issues must be clarified prior to deployment in commercial settings