Why does the plastic bucket of 25 liters in the north of Yingkou deform?

Why does the plastic bucket of 25 liters in the north of Yingkou deform?

Some people say that it is because of the good sealing. After refilling the plastic drum with liquid cargo, after screwing the lid tightly, because the airtightness is tight, the pressure inside the drum becomes smaller after the liquid is cooled, and the outside The pressure is large, which causes the pressure difference between the inside and outside of the barrel, causing the plastic barrel to deform. The more sealed the plastic bucket is, the more airtight it is, the easier it is to deform. In fact, this is a conceptual error. The plastic bucket obstruction inspection regulations clearly stipulate that the seal is airtight. If the liquid inside is a dangerous product, then the plastic drum required for the industrial dangerous goods must be able to withstand the pressure of 30Kpa / cm2, while the class 2 and 3 dangerous goods The plastic drums required to be contained must also be able to withstand a pressure of 20Kpa / cm2.

The machine used to manufacture 25-liter plastic drums has fewer control points for the wall thickness, resulting in unevenness of the barrel body, so it is also relatively loose when formulating the standards for plastic drums. The two-point wall thickness of the symmetrical two examples is allowed to be in the range of 2: 1 within. Such plastic barrels with uneven wall thickness will often pass the anatomy analysis. In actual use, the plastic barrel will be deformed because the thickness of the barrel wall varies greatly.