Thread Content
This post was last edited by Desert Fish on 2021-12-25 at 21:24. In a container filled with liquefied gas, under normal conditions the substance should be mostly in liquid state due to pressure; in reality, however, it exists in a saturated state where both gas and liquid coexist. But if the container is overfilled or exposed to heat unexpectedly, its interior may become entirely filled with the liquid phase. As the temperature continues to rise, the expansion of the liquid combined with its low compressibility often leads to a sharp increase in pressure inside the container. For example, in an over-pressurized steel cylinder containing liquid chlorine, for every 1°C increase in temperature when the cylinder is full, the pressure inside increases by 1–2 MPa; further rises in temperature can lead to an explosion. Overfilling with liquefied gases is extremely dangerous, as these substances, which are mostly in liquid state due to the high pressure inside the container, will immediately boil and evaporate once the container ruptures, causing a sudden drop in pressure; this leads to a rapid expansion in volume, resulting in what is known as a \"vapor explosion\" or \"boiling explosion.\" The energy released at this time is much greater than when the cylinder is filled with saturated steam or ordinary gases; the crack expands rapidly, and in some cases it almost flattens out the cylinder into a sheet. Overfilling of liquefied gases is one of the causes of explosions in such pressure vessels. After filling with liquefied petroleum gas, raising the temperature by another 2°C causes the pressure increase inside the container to exceed the design pressure of the mixed liquefied petroleum gas storage tank (1.77 MPa) ； Raising the temperature by another 4°C could cause the storage tank to rupture (510–640 MPa for Q345R). In recent years, explosions of civilian liquefied gas storage tanks have occurred frequently in winter, due to the tanks being overfilled outdoors before being moved into warm indoor areas. When designing chemical pressure vessels, for storage containers used to hold liquefied gases, the \"filling coefficient\" must be indicated on the general layout diagram, or the specific amount of gas that can be stored, calculated based on this filling coefficient, should be specified on the same diagram.