At the time of writing this article and to the best of our knowledge, no commercially available drone is intrinsically safe to a level where it can safely fly in an environment where explosive gases or dust is likely to occur in normal operational conditions. The "Are drones intrinsically safe?" question is definitely the first one that comes to the mind of professionals concerned with performing visual inspections and maintenance in environments that are subject to hazardous materials. As the manufacturer of , we had to answer this question countless times, and we thought that this topic deserves its own article. However, even if an intrinsically safe drone does not exist, it does not prevent drones from being applied for visual inspection in the Oil & Gas and Chemical industries. To properly cover the topic of the intrinsically safe drone, let's start by looking at what it takes to build a real intrinsically safe drone. Then we will look at solutions to mitigate risks and use drones where we would naturally not use them. Finally, we will look at the benefits of using drones despite risk mitigation procedures.
What does it take to build an intrinsically safe drone?
First of all, it is important to define the level of intrinsic safety that must be accomplished. Different standards are used around the world to regulate the use of electronic equipment in an explosive atmosphere. Standards differ in nomenclature and specificities, but all agree that passed a certain concentration of hazardous material and a certain probability of being in the presence of hazardous materials, electronic equipment must present certain characteristics to mitigate the risk of an explosion. This is the level of intrinsic safety we are talking about.
An intrinsically safe machine must not generate a spark nor a static charge. To achieve that, different technics are used: oil immersion, powder filling, encapsulation, or purge and pressurization. In the worst case, if an explosion happens within the intrinsically safe machine, its structure must be able to contain the blast and guarantee that no hot gas, hot parts, flame or spark is released to the explosive environment. As a consequence, a serious intrinsically safe machine is usually heavier than its non-intrinsically safe counterpart. This ratio is usually in the range of 10x. And if that wasn't enough, the surface of such a machine must not reach more than 25°C (77°F).
Drones have every characteristic of a very dangerous equipment to fly in an explosive environment. It carries batteries, motors, and potentially LEDs that reach a high temperature when in function. It has high-speed rotating propellers which can generate a lot of sparks and static electricity. These propellers are mounted on brushless motors exposed to the environment for cooling purpose. produce light which is a source of heat higher than the 25°C ceiling. And finally, drones must be light enough to be able to fly a reasonable amount of time.
Considering all these constraints, until we discover how to compensate for gravity in a more efficient way than what is available today, a serious intrinsically safe drone won't be envisioned.
Why is intrinsic safety the wrong answer to a correct question?
Fortunately, humans are resourceful and the abovementioned limitations have long been overcome using different risk mitigation technics. If human presence is required, intensive cleaning and degassing - until no more trace of explosive is present - is the defacto approach. This risk mitigation technic can be applied as well to deploy drones.
It is also very common to use Nitrogen to purge or inert an enclosed space and avoid explosions. The downside of this technic is that humans can no longer breathe in a Nitrogen purged or inerted atmosphere. However, drones can fly, and with no risk of explosion whatsoever. This safe and simple, yet elegant solution has successfully been tested to allow drone flights in enclosed spaces subject to hazardous material. It is used by some of the largest chemical companies in the world at the forefront of innovation.
Technically speaking and for those who really like to play with fire, a third solution exists. It is scientifically proven that above its Upper Explosive Limit a mixture of air and fuel is too "rich" and will not burn, thus removing the risk of an explosion. However, we do not encourage anyone to try it on and prove scientific theories by walking the talk.
Are the benefits of drones preserved despite mitigation measures?
In most of the cases, the answer is yes. It will essentially be a question of how much more benefits do you'll get by deploying drones instead of humans and this will depend on the inspection you perform or your specific use case.
If we look at the safety impact, simply because you do not have to send humans in a confined space or a hazardous area to visually inspect an asset, the effort of deploying drone technology at your worksite is worth the investment.
From a pure cost point of view, if the results of your inspection were to indicate the need for human intervention to perform a repair, just by having the data intelligence of a remote visual inspection prior to any human entry will be of a tremendous help. You will be able to tell scaffolders where to build scaffolding. "Rather than scaffolding in the entire structure, you may only have to scaffold a single wall or a single location," , Chief Pilot at Viper Drone. This can generate huge downtime and, ultimately, cost savings.
When properly trained, an inspector using remotely operated technology will be much more efficient and faster than if he was to perform the same inspection by entering the asset. The ratio can span from a fourth of the time to a twelve of the time according to Schutte's experience. Depending on the asset, there are even chances that you don't have to stop the entire asset like you would do for a human entry. This can sometimes make a big difference in downtime.