Basic principles of sealing

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The primary cause of leakage is the pressure difference or concentration difference on either side of the sealing area, which drives fluid flow, as well as gaps on the sealing surface that allow fluid to leak out. For different types of seals, the working principles vary. A static seal relies on the gap between the sealed surfaces to achieve sealing ； Dynamic sealing cannot rely solely on the gap between the sealed surfaces to achieve sealing; indeed, the tighter the gap, the greater the frictional resistance generated during the relative movement of the surfaces, which leads to heating of those surfaces and rapid failure of the seal. Therefore, the key to the principle of dynamic sealing is to maintain sealing while avoiding excessive frictional resistance, which involves reducing the pressure difference across the sealed surfaces and maintaining a fluid lubrication film between them. Figure 1 Classification of sealing devices (components)