How often should the vacuum be drawn for an LNG truck?
2 Answers
There is no specific time limit for how often the vacuum should be drawn for an LNG truck; it depends on the usage of the gas cylinder. When the vehicle leaves the factory, the vacuum level in the interlayer of the LNG heavy truck's gas cylinder is around 3*10-3Pa, providing excellent insulation. However, as the usage time increases, the vacuum level in the interlayer will decrease, causing the pressure inside the LNG cylinder liner to rise and leading to frequent venting through the safety valve. Drawing a vacuum for the LNG truck's gas cylinder is done to stabilize the pressure inside the liner and maintain the low-temperature working state of the cylinder. Advantages of LNG trucks: 1. Safety and reliability: LNG has a higher ignition point compared to gasoline and diesel, and its explosion limit is nearly four times higher than that of gasoline. Even in the event of a leak, spontaneous combustion or explosion is unlikely, ensuring high safety. 2. Clean and environmentally friendly: The comprehensive exhaust emissions of LNG are nearly 85% lower than those of gasoline and diesel, with almost no sulfur compounds, making it super environmentally friendly and easier to upgrade to the National VI emission standard. 3. Long driving range: Compared to CNG vehicles, a 335L steel cylinder of LNG can provide a driving range of over 500 kilometers.
I've been driving LNG trucks for five or six years, and the vacuum layer isn't regularly evacuated. When the truck is new, the vacuum level is set just right and can last seven or eight years. We usually just watch the pressure gauge—if the pressure suddenly spikes, or if the gas in the tank drops noticeably even without much driving, then it's time to check the vacuum. My truck hasn't had its vacuum evacuated in over four years, but my neighbor Lao Zhang's truck had to get it done after a rear-end collision shook the tank. The key is to monitor the actual condition—testing the vacuum level during regular maintenance is the real deal. If you wait until something goes wrong to fix it, it's already too late.
