Mechanical seal manufacturer Tell you the corrosion type and protection method of mechanical seal

Protection method Mechanical seal is often damaged, and the common damage forms mainly include corrosion damage, thermal damage and mechanical damage. The corrosion damage of mechanical seal knowledge is more harmful. Due to the special structure of mechanical seal and different working environment and conditions, the forms of corrosion damage are also diverse.  

L Corrosion of mechanical seal

1.1 Corrosion of metal ring

First, the surface is evenly corroded. If the surface of the metal ring contacts the corrosive medium, but the metal itself is not corrosion resistant, surface corrosion will occur, and the phenomenon is leakage, early wear, damage, noise, etc. Metal surface Cartridge mechanical seal There are two forms of uniform corrosion: film forming and no film. Metal corrosion without film is very dangerous. The corrosion process is carried out at a certain speed, which is mainly caused by wrong material selection. Film forming corrosion. The passivation film is usually protective, but the passivation film on the surface of the materials used for metal sealing rings, such as stainless steel, cobalt, chromium alloy, etc Grundfos The mechanical seal of the water pump is damaged in the scratch, and it is difficult to form a new film under the anoxic condition, which aggravates the galvanic corrosion.  

Second, stress corrosion cracking. Under the simultaneous action of corrosion and tensile stress, the metal first produces cracks in the weak area, and then develops in depth to produce cracks, which is called stress corrosion cracking. The choice of hardfacing carbide and cast iron, tungsten carbide, titanium carbide and other sealing rings is prone to stress corrosion cracking. The seal ring cracks are generally radial divergent, which can be one or more. These cracks communicate with the whole sealing end face, accelerate the wear of the end face, and increase the leakage.  

1.2 Corrosion of non-metallic rings

First, graphite ring corrosion. There are three reasons for the corrosion of impermeable graphite ring impregnated with resin: first, when the end face is overheated and the temperature is greater than 180oC, the impregnated resin will break away from the graphite ring, which will reduce the wear resistance of the ring; Second, if the impregnated resin is not properly selected, chemical changes will occur in the medium, which will also reduce the wear resistance; Third, the impregnation depth of the resin is not enough. When the impregnation layer is removed, the wear resistance decreases. Therefore, it is necessary to select corrosion resistant impregnating resin, use high-pressure impregnation and increase the impregnation depth for the establishment of sealed cooling system.  

Second, the oxidation of graphite ring. In oxidizing media, when the end face is dry rubbed or poorly cooled, the temperature of 350~40o ℃ can make the graphite ring react with oxygen to produce CO and gas, which can make the end face rough or even broken. The non-metallic ring will also break under the simultaneous action of chemical medium and stress.  

Third, the corrosion of polytetrafluoroethylene (F4) sealing ring. F4 is filled with glass fiber, graphite powder, metal powder, etc. to improve its temperature resistance and wear resistance. The corrosion of the filled F4 ring mainly refers to the selective corrosion, dissolution or deterioration of the filling. For example, in hydrofluoric acid, glass fiber molecules are thermally corroded, so what to fill depends on the specific situation.