What Causes High Pressure in LNG Cylinders?
4 Answers
LNG cylinder pressure is high because the pressurization valve remains in the open state. Introduction: Liquefied Natural Gas, abbreviated as "LNG," is natural gas in its liquid state. It is produced through a series of cryogenic condensation processes that cool natural gas to ultra-low temperatures (-162°C) under normal pressure, converting it into liquefied natural gas. Working Principle of LNG Cylinders: When the pressurization valve is opened, the liquid at the bottom of the cylinder undergoes heat exchange with the inner wall of the shell via the pressurization coil, transforming into saturated vapor. This vapor then returns to the gas space of the cylinder through the combined pressure-regulating valve, increasing the internal pressure. During operation, the pressurization valve can remain open continuously, with the flow through its pipeline controlled by the combined pressure-regulating valve. Once the internal pressure reaches the level set by the combined pressure-regulating valve, the pressurization system automatically shuts off. After use, the pressurization valve should be manually closed.
As a frequent driver of LNG vehicles, I've encountered several instances of excessive gas cylinder pressure, usually due to an accumulation of evaporated gas. For example, during summer when the vehicle is exposed to intense sunlight, or when the insulation layer is damaged allowing heat to enter, the liquid evaporates more quickly. Another common issue is overfilling during refueling; when the liquid expands due to heat and has nowhere to go, the pressure naturally spikes. Valve problems are also quite common—if the safety valve gets stuck or fails, gas can't escape, causing the pressure to gradually rise. I've found that checking the insulation performance before each trip is crucial. If the pressure gauge shows an abnormality, it's important to stop the vehicle immediately for ventilation and avoid forcing it to run, as leaks could potentially lead to serious issues. Regularly visiting a service center to test the valves and regulators can prevent such incidents, ensuring safe and worry-free driving.
When I was driving an LNG truck before, the gas cylinder pressure was too high and almost caused an accident. Luckily, I discovered it in time. The reason is often overfilling, where the liquid fills the cylinder leaving no space for expansion. Once the temperature rises, the pressure builds up. Improper handling of evaporated gas is also a major factor. If the exhaust valve is faulty or the regulating device is damaged, gas accumulates and the pressure increases. External factors like hot weather or parking near a heat source can exacerbate the situation. I recommend checking the pressure gauge readings daily. If the pressure remains consistently high, don’t ignore it—release the excess gas promptly or have a professional inspect the valves. Safety first; never let a small issue lead to an accident.
The rise in LNG cylinder pressure may stem from several key points. Excessive evaporation of natural gas, such as poor insulation or excessive heat load, can cause rapid vaporization and accumulation of the liquid. Overfilling is a common issue, leaving insufficient space for liquid expansion. Malfunctioning valves or safety devices that fail to release pressure in time can also lead to abnormal increases. During inspection, start with the external environment by removing heat sources, then test valve functionality, and repair or replace them if necessary. Address any issues as early as possible to avoid hazards.
