For this specialist, it is necessary to consider the safety of hydrogen vehicles
Who better to talk about safety in hydrogen vehicles than an explosive character who is an authority in the field? In this case, Mark Mouthon is the right person. After becoming a master installer of LPG systems from the mid-1980s, he devoted himself to training. Assisting staff primarily responsible for maintaining handling equipment. Then, from 1993, temporarily and liberally, it was quickly integrated into the GNFA (National Group for Automotive Education), which was born 2 years later.
An expert volunteer firefighter and recipient of the gold medal for internal security, he has trained SDIS (Departmental Fire and Rescue Services) personnel from most departments in France on alternative energy interventions. He took a very concrete and active part in the development of LPG and CNG mobility, burning more than 1000 vehicles for safety and training experiments. We invite you to discover all this in a special interview recently published on the Gaz Mobilité website.
Copy texts to hydrogen
Since the 1964 decree, gas-powered vehicles have come a long way in terms of safety: “The text provided for a rapid valve for the NGV to be activated in the event of a fire. Later, it was necessary to lie down under the burning car and open this valve to release the gas.”.
Especially thanks to Marc Mouthon, the tanks of LPG cars got a valve that releases the product in case of excessive pressure, and now in France there is a surplus of safety devices in the steel models designed for CNG.
“With a few tweaks, we copied and pasted the R67 European regulation for LPG to get R110 dedicated to CNG. For hydrogen, R134 is perfect. There are many things to improve. Now we will have to transfer the lessons learned during the tests with CNG to hydrogen mobility.he explains.
Diffusion and rolling
“It is important to think carefully about safety systems that release gases in the event of a fire. I have an example of a CNG bin with a side outlet. The height of the flame reached 10 meters. Although the gas release was short-lived, it was enough to destroy the artist’s gallery at the bottom of the neighboring building.he describes.
“You can use chamomile for better diffusion, which reduces the effect of the flame. With hydrogen tanks designed for 350 bar, the radius is only 2 meters. Depending on the orientation, the car reduces rejections »compares “The hood also makes a difference because it affects the direction and power of the jets. It is a bare tank that is subject to approval today. It should be a complete system, including the hood.”he assures.
Tiger and elephant
“CNG and hydrogen tank explosions are very different. For training, I compared models with CNG at 200 bar, hydrogen at 350 and 700 bar. With natural gas, the heating chamber panics and the tank completely dislodges after a little over 4 minutes without a flame or with a ball of flame. There’s nothing left”Marc Mouthon exposes.
“The heat released by hydrogen is very low. After detonation, the tank is moved, but not destroyed. You can see that it is pierced with hydrogen at only one end at 350 bar. At 700 bar it comes out more damaged, but still there. At this pressure, it takes a little longer to detonate, about 5 and a half minutes.”opposes.
How can it be explained? “It’s about the size of the molecule. To make this clear, during my training I mark a tiger for hydrogen and an elephant for CNG. If they have to leave the store urgently, the elephant will break the entire window while the tiger can get through the door with less damage., he answers. Does this mean that a hydrogen tank explosion would be less destructive to the vehicle and less dangerous to the emergency services in the event of a fire compared to CNG? “Kind of, yeah”admits.
Hydrogen tank explosion
The case of the Toyota Mirai
Marc Mouthon has taken up the pilgrim’s rod to warn against the safety flaws already discovered in hydrogen vehicles, particularly the Toyota Mirai. “Current regulations minimize risks and safety needs. It was written as a compromise to please the entire ecosystem. R134 allows approval of components that should not »he says.
“Toyota Mirai’s 3 tanks, for example, each have only one TPRD, which acts as a protector. In the larger one, located longitudinally and in the center of the car, the valve and its TPRD are at the rear. “If a fire starts in front of the car and stays there, the tank is likely to explode because of the direction of the wind like Mistral.”warns.
Is it the same in Hyundai Nexo? “I don’t know yet. At least one safety device is required at each end of the tank. And even in the middle, if needed, as in CNG buses. On paper, the additional costs would not be significant, but many containers were not designed for this.”he answers. “We don’t burn cars in the suburbs of Beijing, Tokyo or Seoul. But in France, yes. Therefore, the safety aspect cannot be neglected »– insists our interlocutor.
Arrangement of components to be respected
“There are also serious errors in the design of the components. So with high pressure valves. These mistakes were made by startups and then repeated by current developers.”This was reported by Marc Mouthon.
“If we put in a manual valve, it’s isolating the circuit. However, there are devices where the solenoid valve is located between the tank and the manual valve. Therefore, there is always a component under pressure – the HP solenoid valve – when the isolation valve is closed to lock the circuit “he explains.
“There are also systems where the regulator is placed between the mechanical valve and the solenoid valve. This is not good either. Because if the regulator fails, its pressure relief valve can empty the tank.”he adds. “These 2 bad mounts are found on certified systems. They are dangerous, but they follow the rules. There is no common sense of design here.”Highlights a coach who introduced hydrogen to his sessions 10 years ago.
What forms of hydrogen are there for mobility?
“I am very skeptical about hydrogen used in heat engines. Primarily because there will be the formation of nitrogen oxides, which requires the use of a product such as Adblue. NGV/bioNGV is more suitable for this because it contains 3 times more energy per volume. On the other hand, syngas is the main vector for the development of green hydrogen.”Marc Mouthon rates.
“If we get liquid hydrogen out of rockets, it can’t be used in trucks. Manufacturers are working on this topic, especially since they receive subsidies for this. For 2020, I had planned a demonstration of leakage with liquid hydrogen ignition at the technical days organized by SDIS 86. But Covid-19 did not allow us to do that.”he continues.
“I have new requests for H2 training, circuit and component interventions, especially when degraded due to accident or end-of-life. I have already had the pleasure of leading internships for Volvo Trucks, Hype taxi, Eneria, Energy Explorer, Mercedes. Soon for the city of Paris, Iveco and Axa. But it is in collaboration with Energy Formation that I will lead my future training courses on hydrogen.”he concludes.
H2-Mobile and I would like to thank Marc Mouthon very much for his sensitivity and time.