What are the reasons for mechanical seal failure in chemical pumps?

　　Chemical pump mechanical seal failure reason analysis

　　First, the cause of corrosion

　　According to the type of corrosion, mechanical seal corrosion can be divided into metal ring corrosion, non-metallic ring corrosion, auxiliary seals and their contact parts of the corrosion of three categories.

　　1, metal ring corrosion

　　Metal ring is the core of the chemical pump seals, the component after corrosion will have a huge impact on the sealing effect of the chemical pump, so, explore the metal ring corrosion has significant practical significance.

　　Uniform corrosion of the surface of the metal ring, if corrosive substances contaminated near the seal will lead to damage to the seal, due to the poor corrosion resistance of the metal ring itself, contaminated with corrosive substances will accelerate the corrosion of the surface, under conventional conditions, the corrosion of the metal ring has the following serious consequences: one is the centrifugal pump leakage of the media; the second is the metal ring is abraded, affecting the sealing effect; the third is the metal ring was destroyed, the sealing function of the centrifugal pump basically lost; the third is the metal ring was damaged. Centrifugal pump sealing function is basically lost; the fourth is the metal ring will occur abnormal sound.

　　In chemical production, the surface of the metal ring is corroded, the corrosion state is divided into film corrosion and no film corrosion, film corrosion on behalf of the metal ring is corroded after the formation of a natural passivation film on the surface, will play a certain role in the protection of the metal components, but the metal ring material in the film, it will exacerbate the friction of its end face, thus shortening the service life, resulting in the passivation film to lose the protection of the function of the ring in the lack of oxygen, the new passivation film can not be generated. The new passivation film can not be generated. In this case, the corrosion is further aggravated. No film corrosion is caused by the selection of the wrong material, this kind of corrosion propulsion speed is faster, the metal ring is very unfavorable.

　　Secondly, stress corrosion damage, if the tensile stress and corrosion at the same time on the metal ring, its weak areas will crack, and then, the rupture position continues to increase, the gully is getting deeper and deeper. Rupture is triggered by stress and corrosion synchronization. According to preliminary statistics, the chance of rupture of metal rings made of titanium carbide, tungsten carbide, cast iron and cemented carbide is much higher than that of other materials. Conventional conditions, metal ring rupture cracks show scattered, cracks vary in number, cracking position can lead to end face wear continues to increase, thereby increasing the amount of leakage, affecting the chemical pump operation and chemical production.

　　2, non-metallic ring corrosion

　　Chemical pump mechanical seal non-metallic ring is one of the very key parts, and metal ring similar, non-metallic corrosion also affects the chemical pump mechanical seal function, graphite ring is an important part of the non-metallic ring, under normal conditions, graphite ring does not have permeability, at the same time, graphite ring need to be impregnated with resin before use, this is due to the resin impregnation can enhance the graphite ring wear resistance.

　　The reasons for graphite ring corrosion in chemical production can be summarized as follows:

　　First, if the temperature of the end face of the non-metallic ring itself rises suddenly and exceeds 180℃, the graphite ring will precipitate the impregnated resin, and its abrasion resistance decreases rapidly.

　　Secondly, there are many kinds of resin materials, if the resin material chosen by the installer cannot adapt to the production conditions, the impregnated resin will have chemical reaction with other materials during the production process, resulting in a decrease in the abrasion resistance of the graphite ring.

　　Third, the impregnation depth is not up to standard, when the surface layer of resin is worn out, the graphite ring wear resistance should be reduced.

　　Graphite ring is prone to oxidative corrosion phenomenon, if the medium itself has a strong oxidizing, once the sealing end face cooling degree is low or the end face suffered dry friction, the surface temperature will quickly rise to 350 ℃, in this temperature environment, the medium oxidation and graphite ring chemical reaction, carbon dioxide gas, the gas will lead to the sealing end face is gradually rough, resulting in the rupture of the end face, in addition, the stress and the chemical media In addition, stress and chemical media synchronization will lead to graphite ring rupture

　　3、Special corrosion

　　Auxiliary sealing ring and contact parts of the corrosion of chemical pump seals, auxiliary sealing ring with an important sealing element, if the sealing ring suffers corrosion, will affect the mechanical seal function of the chemical pump, sealing ring is mainly composed of rubber, and its material determines the sealing ring corrosion resistance, chemical production, rubber materials are diverse, any one material with a significant difference in the corrosion resistance of rubber materials, rubber materials performance will be With the passage of time and aging, the loss of corrosion resistance, when the rubber corrosion resistance failure, the seal surface will become rough, gradually lose elasticity, until the rubber is completely fractured, oil-resistant rubber on the sealing effect of the maintenance of the better, on the contrary, oil-resistant rubber will be poorer with the growth of time and expansion, the friction it suffers from should be raised, the rubber floatation weakened, the sealing effect and then reduced.

　　For auxiliary sealing ring contact parts of the corrosion, contact parts refers to the seal and specific parts (static ring seat, static ring, bushings, dynamic ring) of the contact, specific parts and the seal contact process did not occur during the movement of the obvious, due to the