Why can't the LNG pressurization valve increase pressure?
3 Answers
When the vehicle is loaded and the cylinder pressure is below 0.8 MPa, insufficient power may occur. You can open the pressurization valve and then the return valve to activate the cylinder pressurizer. Wait until the pressure increases to the range of 0.8~1.2 MPa before closing both valves. Below are relevant details: Precautions: If the cylinder pressure is too low, gas supply will be insufficient; if it is too high, it may trigger the safety valve to release gas, causing losses. The cylinder pressure should not exceed 1.7 MPa. LNG vehicle cylinders are designed with two-stage safety valves to account for pressure increases due to rising temperatures. When the internal pressure exceeds 1.2 times the normal working pressure, the primary safety valve activates to release gas, thereby reducing the pressure until it falls below 1.2 times the working pressure. If the pressure does not return to normal after the primary safety valve releases gas, the secondary safety valve will activate (at 1.8 times the working pressure). Maintenance: Do not place the cylinder in environments above 60°C for extended periods. Owners who install cylinders on the vehicle body with metal protective boxes should especially avoid exposing the vehicle to direct sunlight in summer. Avoid using the cylinder in high-static environments, prevent impacts, and keep it away from chemicals. Vehicle cylinders should be maintained at the contracted modification facility and inspected regularly to ensure the safety of users and others.
I've dealt with numerous pressurization valve issues in LNG systems, where the most common problem is internal valve sticking or blockage by impurities. Back when I worked at the auto plant, an LNG truck kept failing to build up pressure. Upon disassembly, we found moisture in the pipeline had frozen, blocking the valve core passage. After cleaning and adding antifreeze, the issue was resolved. Another possibility is seal ring aging leading to leaks—whether air or LNG escaping, the pressure naturally drops. The control system could also malfunction, such as sensors misreading data, causing the electronic module to fail to actuate. I recommend starting with manual operation tests. If the valve can be manually opened and closed, the issue likely lies in the control end. If not, inspect the filters and connecting pipelines. Regular cleaning and dustproof protection are crucial, especially in humid environments, as this can reduce faults by half.
As a seasoned LNG bus driver, I once encountered a situation during a long-distance trip where the pressure of the pressure valve suddenly failed to rise, nearly causing a delay. Later, it was found that the issue was due to a loose air pipe joint causing a leak, possibly caused by the bumpy road. Tightening it myself solved the problem. However, I've also seen cases where the valve got stuck due to rust, requiring disassembly for cleaning and lubrication. It's important to always pay attention to the operating sounds; if you hear abnormal friction noises or unstable air pressure, be alert. These valves are easily affected by oil stains or impurities, such as when unclean LNG medium is added, causing blockages inside. I recommend developing a habit of performing a quick check before driving, such as feeling the pipelines by hand for any leaks. Safety should always come first.
