According to statistics, about 80% to 95% of the leakage of mechanical seals is caused by sealing faces and friction pairs. Flygt pump seals
has this problem. In addition to keeping the sealing surface parallel, it is mainly the material problem of the friction pairs. The design of most mechanical seals uses stiffer materials to make the revolving surface, so that it can rotate friction on the soft stationary surface. The rotating surface is now made of stainless steel or harder material, such as tungsten carbide or silicon carbide. Graphite or Teflon is used for stationary surfaces.
Material selection of mechanical seal friction pairs is a complex problem. In general, it should be selected according to the properties of the working medium, pressure, temperature and rotation speed, and the ability to withstand short time friction when the pair is started or the liquid film is destroyed. Taking into account the above factors, the material of the friction pair should have the following conditions:
(1). High mechanical strength, resistance to pressure and deformation;
(2). It has good dry abrasion resistance, high load resistance and good self lubrication.
(3). The matching material has good running in property without excessive wear and dual corrosion.
(4). Good wear resistance, long life;
(5). Good thermal conductivity and good heat dissipation;
(6). High temperature resistance;
(7). Good thermal cracking resistance;
(8). Strong corrosion resistance;
(9). The linear expansion coefficient is small, and it can resist heat distortion and dimensional stability.
(10). Good machinability and good molding performance.
(11). Good air tightness;
(12). The density is small.
But the environment is different and the selection of material is different. When we choose mechanical seal, we should take care of the consistency of material selection and take care of the difference of environmental corrosion; the temperature, concentration and pressure are different. The material is different from the material; the same medium temperature, concentration and pressure are different, the corrosion is different. Different, the selection is different.