Corrosion Analysis of the mechanical seal

mechanical security seals, also known as face seal (Mechanical End Face Seal), is a dynamic seal rotating shafts. Mechanical seals, reliable performance, small amount of leakage, long life, low power consumption, do not need frequent maintenance, and can adapt to the production process automation and high temperature, low temperature, high pressure, vacuum, high speed and a variety of strong corrosive medium, containing solid particles media and other harsh mining sealing requirements.
A mechanical seal - metallic ring corrosion
First, uniform surface corrosion. If the metal ring surface contact with corrosive media, and the metal itself impatience corrosion, it will produce surface corrosion, the phenomenon is leaking, early wear and tear, damage, sound and so on. Uniform corrosion of metal surfaces and non-film forming two forms, free film very dangerous metal corrosion, the corrosion process in a certain speed, which is mainly caused by the errors selection. The corrosion film, the passivation film characteristics generally has a protective effect, but the metal material used for the sealing ring, such as stainless steel, cobalt-chromium alloy such as a passivation film on the surface friction of the end face destruction, under hypoxic conditions New film is difficult to produce, so that galvanic corrosion intensified.
Second, stress corrosion cracking. Metal in corrosion and tensile stress while under the effect of the first cracks in the weak areas, and then to develop in depth, resulting in rupture, known as stress corrosion cracking, the choice of surfacing and cast iron carbide, tungsten carbide, titanium carbide seal ring, prone to stress corrosion cracking. The radial sealing ring generally divergent crack, and can be one or more. These cracks communicate the bolt seals faces, accelerated wear of the end face, an increase of leakage.
Second, the mechanical seal - metallic ring corrosion
First, the graphite ring corrosion. Impregnated with a resin impermeable graphite ring, its corrosion for three reasons: First, when the face overheating when the temperature is higher than 180oC, to break away from the resin impregnated graphite ring, the ring wear down; Second, if the resin impregnated Choose properly, it will undergo chemical changes in the medium, but also to wear down; Third, resin impregnated deep enough, when rubbed impregnated layers, wear down. Establishing the sealing of the cooling system, the corrosion of the impregnating resin selection, use of high pressure impregnation, impregnation depth increase is necessary.
Second, oxidation of the graphite ring. In an oxidizing medium, the end face or poor cooling in the dry friction generated when a temperature of 350 ~ 40o ℃ graphite ring can react with oxygen to produce CO, gas, can face becomes rough, or even rupture. Metallic ring, while chemical medium and under stress, will rupture.
Third, polytetrafluoroethylene (F4) corrosion of the sealing ring. F4 filler such as glass fiber, graphite, metal powder to improve its heat resistance, wear resistance. Corrosion fill F4 ring filled mainly refers selective etching, stripping damage or deterioration. For example, in hydrofluoric acid, hot corrosion of glass fiber molecules, so what things should be filled, as the case may be.