As a critical connection component in piping systems, the sealing surface type of an overflow short pipe flange is a core indicator for evaluating its sealing performance, as it significantly impacts leakage rate. Different sealing surface structures directly affect the probability and extent of leakage by altering the gasket's stress distribution, the media flow path, and the contact area.
The flat sealing surface is the most basic sealing type in overflow short pipe flanges. Its surface is smooth and without protrusions, resulting in a simple structure but limited sealing performance. This type of sealing surface relies on the gasket's own elasticity to fill minor irregularities on the flange surface. If the gasket preload is insufficient or the surface roughness is high, the risk of interface leakage increases significantly. Especially under high pressure or corrosive media conditions, flat sealing surfaces are prone to increased leakage rates due to gasket extrusion or aging, making them more suitable for low-pressure, non-toxic media applications.
The raised face sealing surface increases the contact area between the gasket and the flange by incorporating raised rings along the flange edge. This structure allows the gasket to undergo greater plastic deformation under preload, effectively filling minor gaps in the sealing surface. Simultaneously, the raised rings restrict lateral gasket movement, reducing gasket displacement caused by media pressure fluctuations. Compared to flat types, raised-face sealing surfaces have a lower leakage rate under the same operating conditions. However, attention must be paid to the matching of the raised height with the gasket thickness; improper design may lead to localized stress concentration.
Concave-convex sealing surfaces employ a paired design, achieving sealing through the mechanical interlocking of the concave and convex surfaces. This structure confines the gasket within the groove, preventing the medium from directly scouring the gasket edges and significantly reducing the risk of interface leakage. Simultaneously, the centered installation characteristics of the convex-convex surfaces reduce misalignment problems caused by installation errors, further improving sealing reliability. Under high-pressure or flammable/explosive media conditions, convex-convex sealing surfaces exhibit better leakage control than the previous two types due to the gasket's resistance to extrusion and the uniform distribution of friction between the sealing surfaces.
Tongue-and-groove sealing surfaces create a more complex media flow path through the tight fit of the tenon and groove. The gasket is completely encased within the groove, completely isolated from the medium, effectively preventing seepage and leakage. Furthermore, the geometric constraints of the tongue-and-groove structure cause uniform compression deformation of the gasket under preload, resulting in a more rational distribution of contact pressure between the sealing surfaces. This design excels under ultra-high pressure or highly toxic media conditions, but it requires extremely high machining precision. Deviations in groove dimensions or surface scratches can lead to a sharp increase in leakage rate.
The ring-connection type sealing surface is specifically designed for metal ring gaskets, achieving a seal through line contact between the trapezoidal groove and the metal ring gasket. Under preload, the metal ring gasket undergoes plastic deformation, filling the tiny gaps within the groove to form a high-strength metal seal. This structure has a high tolerance for installation errors, and the high-temperature and corrosion-resistant properties of the metal ring gasket make it suitable for extreme conditions. However, the leakage rate of the ring-connection type sealing surface is significantly affected by groove depth, groove width, and surface finish. Any deviation in geometric parameters can disrupt the sealing line contact, leading to leakage.
The matching between the gasket and the sealing surface is a key factor in quantifying the leakage rate. Different sealing surface types require gaskets made of specific materials. For example, flat types are suitable for non-metallic flat gaskets, while ring-connection types must use metal ring gaskets. The gasket's compression rebound characteristics, creep relaxation behavior, and thickness tolerance all interact with the sealing surface structure, affecting the actual leakage rate. If the hardness of the gasket does not match the roughness of the sealing surface, it may lead to localized stress concentration or damage to the sealing surface, resulting in leakage.
In practical applications, leakage rate control of overflow short pipe flanges requires comprehensive consideration of the sealing surface type, gasket type, media characteristics, and operating conditions. Optimizing the geometric parameters of the sealing surface, improving machining accuracy, and selecting suitable gasket materials can significantly reduce the risk of leakage. For example, using a ring-type sealing surface with a metal ring gasket under high-temperature conditions, or using a tongue-and-groove type sealing surface with a corrosion-resistant gasket in corrosive media environments, can effectively control the leakage rate and ensure safe system operation.
