What about flange gaskets?

The rubber pads between bearings used in industry for shock absorption and abrasion prevention are called flanges. Industrial flange gaskets are a key part of stopping leaks. Commonly used are polytetrafluoroethylene gaskets, metal gaskets, inner and outer ring metal gaskets, graphene gaskets, rubber sealing gaskets, etc.

Type of flange gasket

1) Polytetrafluoroethylene gaskets are also called tetrafluoroethylene gaskets

Made of polytetrafluon material, polytetrafluon gasket is mainly used for FF full plane and RF protruder steel flange connection.

2) Metal wound gasket

It is a semi-metallic flat gasket made of metal outer ring and graphene. The characteristics of metal winding gasket are good compression and resilience, with multi-channel sealing and a certain self-tightening function, can maintain its excellent sealing performance under various harsh conditions such as high temperature, low pressure, high vacuum, shock vibration and other cyclic changes. There are four types of metal winding gaskets: basic type, with inner ring type, with positioning ring type, with inner ring type and positioning ring type.

3) Metal covered shoe gasket

It is a composite gasket with non-metallic material as the core material, cut into the required shape and coated with metal sheet with a thickness of 0.25 ~ 0.5mm. According to the bag shoe state, generally divided into flat type and corrugated type two. According to the structure, it is divided into two types: plane type (F type) and corrugated type (C type). The structure type of metal covered shoe gasket for flange of pressure vessel is plane type.

4) graphite composite gasket

Also known as flexible graphite composite gasket, usually made of graphite composite reinforced plate. Graphite composite gasket characteristics are mainly characterized by good high temperature resistance, low temperature resistance, corrosion resistance, radiation resistance and other properties, high strength, can be used in high pressure conditions. Flexible graphite composite gaskets are divided into RF type, MFM type and TG type, which are suitable for protrudate surface, concave and convex surface and tenon surface flange respectively.

5) metal wave tooth composite gasket

The gasket has both the strength of metal and the characteristics of corrugated elasticity, with a maximum temperature of 650℃ and a maximum pressure of 26MPa. Flexible graphite metal wave tooth composite gaskets can be divided into three types according to their different structures: basic type, with positioning change type, with strip type.

6) Metal ring sealing gasket

It is a solid metal gasket with octagonal or oval section processed by stainless steel or alloy material, which has radial self-sealing effect. Metal ring sealing gasket and flange groove match, good sealing, but the processing accuracy is high, so the manufacturing is higher.

7) Octagon and oval pads

Octagonal pads and elliptical pads for trapezoidal groove flange (commonly known as "earth ring" in the oil refining industry) have good sealing performance. On the cone of the groove, the octagonal pad is the surface contact and the elliptical pad is the line contact. Therefore, the elliptic pad has good adhesion under low fastening force, but it needs to be tightened twice. And octagonal pad generally a fastening, not easy to leak.

Advantages of flange gaskets

1. Wide range of temperature

2. Good drug resistance and softness

3. Low temperature resistance, good heat resistance, good electrical insulation performance

4. No pollution medium, high sealing reliability

5. Compressibility, good recovery, good sealing, surface without finishing

6. Simple use, cheap price, wide range of pressure

Factors affecting the tightness of flanges

1) Gasket performance

Gasket is used for sealing the gaps between the flange sealing surface, prevent fluid leak sealing is an important part of, containing non-metallic gaskets and metal gasket gasket type in order to expand the gasket surface and the distance between the flange sealing surface, in order to make the gasket surface and flange surface between elastic, needs under the appropriate reaction to produce the necessary elastic deformation. When choosing gasket material, it is also necessary to consider the working medium and working temperature. The width of gasket is also one of the important factors affecting sealing, and the width of gasket is also one of the important factors of sealing performance.

2) Sealing surface type

And give play to the role of sealing between the flange gasket interface called flange sealing surface or on the surface, sealing surface type and shell, the result of the leak and the choice of gasket performance, shape and surface properties of the flange sealing surface plays an important role in sealing flange sealing surface of straightness and sealing surface and flange the verticality of middle line, The stress uniformity of gasket and the roughness of flange sealing surface with good contact between gasket and flange should be directly affected to meet the requirements of gasket. There should be no wound or surface crack on the surface.

3) Flange rigidity

Flange, excessive warping deformation due to insufficient rigidity, mostly poor bolt fastening sealing flange in the process of production, one of the main reasons for high rigidity of flange deformation is small, the force of bolts evenly to the gasket, flange flange rigidity is related to various factors, among them, increasing the thickness of the flange ring, flange ring increase with the decrease of the diameter of the bolt circle among, outer diameter, In addition, increasing the size of the cone neck can increase the bending resistance of the flange, but in principle, if the rigidity of the flange is not increased, it will increase the rigidity of the flange.

4) Control conditions

The physical and chemical properties of pressure, temperature and medium have a complex effect on the sealing performance. Simple pressure and medium have little effect on the sealing performance, but under the joint action of temperature, especially under the fluctuating high temperature, the sealing performance is seriously affected and the failure is caused by fatigue. At high temperature, the medium has low viscosity, high permeability and easy to leak. The corrosion effect of the medium on the gasket and flange is intensified, and the possibility of leakage is increased. Therefore, the flange, bolt and gasket will produce high temperature creep and stress relaxation, and the seal will be damaged.