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Sealing is a measure taken to prevent fluids or solid particles from leaking between adjacent mating surfaces, as well as to stop external contaminants such as dust and moisture from entering the interior of machinery and equipment. The sealing elements in centrifugal pumps are designed to ensure that the interior of the pump and the surrounding internal and external spaces are separated in a leak-free or minimally leaky manner. Even if absolute sealing is not achieved (for example, under throttling conditions), the relevant components are still referred to as sealing components. The range of sealing degree goes from absolutely sealed sealing elements (with the sealing surfaces in close contact) to unsealed sealing elements (such as gaskets, sliding seals, O-rings), to throttling gap structures that allow leakage. Almost all types of seals can meet the sealing requirements in pipes and pumps. Sealing type: 1) Sealing surfaces that remain stationary (static seal); 2) Sealing surfaces that slide relative to each other (dynamic seal); 3) Sealing surfaces that can be adjusted relative to each other within a given range (adjustable seal); 4) Sealing surfaces that rotate around each other (rotary seal). Centrifugal pumps are primarily connected to pipes using seals with stationary sealing surfaces, although other sealing types are also used as well (where the surfaces of the sealing elements can be adjusted relative to each other within a given range, or where the sealing surfaces rotate around each other). Stationary sealing surface: The stationary sealing surface has functions such as \"sealing,\" \"centering,\" and \"alignment,\" and the type of seal can be selected based on these functions. “The “seal” function often applies a high sealing force to the sealing surface. Axial O-ring seals require a relatively low sealing compression force, axial gaskets need a higher sealing compression force, while metal ring contact seals require the highest sealing compression force. In contrast, radial O-rings require only a lower radial preload to achieve sealing. Since the sealing elements in locations such as the drain plug serve only a sealing function (without the need for alignment), their sealing design can be flexible. For the bearing cover of the bearing bracket, since its sealing elements are not exposed to significant pressure differences, it can be designed with a very simple structure accordingly. Rotary seals installed between stationary sealing surfaces (such as between a shaft sleeve and the shaft) are subjected to pressure differential forces in addition to centrifugal forces. These forces can be absorbed by adopting appropriate designs (such as restricted gaskets). Different types of static sealing surfaces: 1) Non-separable type (the flange and the sealing surface are in close contact); 2) Separable type (using gaskets or elastic materials); 3) Restrained type (such as O-rings); 4) Convex surface seal (metal gaskets); 5) Seal with isolation fluid (suitable for flammable, explosive, toxic, or harmful media, as well as in situations where there is a risk of air infiltration under vacuum conditions). Sealing surfaces that slide against each other are used to compensate for thermal expansion caused by temperature fluctuations during installation or operation; for example, two concentric tubes are sealed to each other using gland packing. For mechanical seals, O-rings or rubber bellows are used to ensure compensation for axial movement of the seal. Sealing surfaces that adjust to each other within a given range; these sealing surfaces are used for sealing through diaphragms, bellows, and expansion joints (in order to limit the forces acting on the pump outlet or to provide sound insulation between the pump housing and the pipes). This type of sealing element also includes connections and sealing via hoses. Rotating sealing surfaces: For rotating sealing surfaces, their function is to seal rotating and non-rotating mechanical components, in order to reduce leakage losses as well as the intrusion of external contaminants such as dust, sediment, and moisture to the desired level, while also minimizing potential wear of the sealing surfaces.