Gear pump mechanical seals appear more damage, the common forms of damage mainly corrosive damage, thermal damage and mechanical damage. Among them, the corrosion damage is more harmful. Due to the special structure of the mechanical seal and the different working environment and conditions, the corrosion damage is also varied. Mechanical seal corrosion: non-metallic ring corrosion First, graphite ring corrosion. Resin impregnated impermeable graphite ring, its corrosion for three reasons: First, when the end surface overheating, the temperature is greater than 180oC, the impregnated resin to break away from the graphite ring, the ring wear resistance decreased; Second impregnated resin if Improper choice, chemical changes occur in the medium, but also wear resistance decreased; third resin impregnation depth is not enough, when worn to impregnated layer, the wear resistance decreased. Therefore, the establishment of sealed cooling system, select the corrosion-resistant impregnated resin, impregnated with high pressure to increase the impregnation depth is very necessary. Second, the graphite ring oxidation. In the oxidizing medium, the end surface in the dry friction or cooling is poor, the temperature of 350 ~ 40o ℃ can make the graphite ring and oxygen react to produce CO, gas, the end face can be roughened, or even rupture. Non-metallic rings in the chemical medium and stress at the same time, it will rupture. Third, Teflon (F4) seal ring corrosion. F4 filled with such as glass fiber, graphite powder, metal powder to improve its temperature resistance, wear resistance. F4 ring filling corrosion mainly refers to the selective filling corrosion, dissolution or deterioration damage. For example, in hydrofluoric acid, glass fiber molecules are hot-corroded, so what should be filled should depend on the situation. Metal ring corrosion first, the surface of uniform corrosion. If the metal ring surface contact with corrosive media, and the metal itself is not corrosion-resistant, it will produce surface corrosion, the phenomenon is leakage, early wear and tear, damage, sound and so on. Uniform corrosion of metal surface with film and no film in two forms, no film metal corrosion is very dangerous, the corrosion process to a certain speed, which is mainly caused by the selection error. Film corrosion, the passivation film usually has the protective effect of the characteristics, but the material used in the metal seal ring, such as stainless steel, cobalt, chromium alloy surface passivation film damage in the end surface friction in the absence of oxygen under the new Film is difficult to generate, so galvanic corrosion worse. Second, stress corrosion cracking. Metal corrosion and tensile stress at the same time the role, the first cracks in the weak area, and then to the depth of development, resulting in rupture, known as stress corrosion cracking, the choice of surfacing cemented carbide and cast iron, tungsten carbide, titanium carbide seal ring, Prone to stress corrosion cracking. Seal ring cracks are generally radial divergent, can be one or more. These cracks communicate the entire seal face, accelerating the wear of the face and increasing the amount of leakage.