Flange type of sealing surface

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What is gasket  ?

The contact surface where the gasket is inserted between the flanges and pressed to achieve the sealing effect is called the flange sealing surface or pressing surface.The choice of sealing face type depends on operating conditions, the consequences of leakage, and the nature of the gasket.The common types of structures are as follows.

EN 1092-1 Q235 FF plate flanges

EN 1092-1 Q235 FF plate flanges

1   Flat sealing surface  : the sealing surface is not a smooth plane.There are usually 2 to 4 concentric triangular cross-section grooves (i.e. flanged waterline) in the plane.Plane sealing surface structure is simple, easy to manufacture, easy to corrosion-resistant lining.Secondly, the width of the sealing surface of this structure is large, so non-metal or metal soft gaskets are often used in use.But when the bolts are tightened, the gasket material can easily stretch to both sides.Applicable to the pressure requirement is not high, non-toxic medium occasions.

2   Concave-convex sealing surface  : It is equivalent to a pair of flat sealing face flanges, one of which is made into a pressing surface with a raised platform, called a flange, and the other is correspondingly made into a concave flange, called a concave flange.The same size gasket as the concave type is embedded, and the gasket is easily centered.The height of the convex surface is slightly greater than the depth of the concave surface, and the bolt is pressed tightly to play a sealing role.This structure can limit the radial deformation of the gasket, prevent the gasket from being squeezed, and improve the sealing performance to a certain extent.Suitable for high pressure occasions.

Raised Face Flange

Raised Face Flange

3    Tongue and groove sealing surface  :  in the middle of a pair of flat sealing surfaces in the width direction, one is made into a cross-section like a tenon, and the other cross-section is like a groove. The pressing surface is paired the former is called a tenon surface flange, the latter is called groove flange. The groove-shaped pressing surface can limit the radial deformation of the embedded gasket, with good sealing performance, and the gasket can be less eroded and corroded by the medium. But the tenon part is easy to damage. It is often used in flammable, explosive, toxic media and higher pressure occasions.

In addition, there are trapezoidal groove sealing surfaces and tapered sealing surfaces. The former uses an elliptical cross-section annular metal gasket, and the latter uses a lens-type annular metal gasket. The above two structures are forced sealing, which are commonly used on high-pressure pipelines.The form and surface properties of the flange sealing surface play a vital role in the influence of the sealing effect. The flatness of the flange sealing surface and the perpendicularity between the sealing surface and the flange centerline directly affect the uniformity of the gasket force and the good contact between the gasket and the flange.

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