Mechanical seal corrosion protection general knowledge detailed

 Because the mechanical seal special construction method and working environment and conditions are not the same, the shape of corrosion damage is also varied. PTFE seals, PTFE gaskets and other mechanical seals are commonly damaged mainly by corrosion damage, heat damage slurry pump mechanical seal damage and mechanical damage. Among them, corrosion damage is more harmful.

A. Metal ring corrosion

 1, the appearance of uniform corrosion. If the metal ring surface contact with corrosive media, and the oil pump mechanical seal metal itself is not resistant to corrosion, it will occur on the surface corrosion, the phenomenon is leakage, pre-wear, damage, sound, etc.. Uniform corrosion of the metal surface has a film and no film two shapes, no film of metal corrosion is very dangerous, known as stress corrosion cracking, the choice of overlay cemented carbide and cast iron, tungsten carbide, titanium carbide and other sealing rings, simple stress corrosion cracking. Corrosion process to a certain double-open pump mechanical seal speed, so that the electric couple corrosion aggravated.

2, stress corrosion cracking. Metal in the corrosion and tensile stress together under the effect of wear resistance. Filled F4 ring corrosion mainly refers to the filling of the selective corrosion, dissolution or metamorphosis damage. Such as in hydrofluoric acid, glass fiber molecular thermal corrosion, these cracks communicate the entire seal end face, accelerating the wear of the end face, so that the amount of leakage increased.

II. Non-metallic ring corrosion

 1, graphite ring corrosion. Company information network mentioned in the impermeable graphite ring impregnated with resin, its corrosion has three causes: First, when the end face is overheated, the temperature is greater than 180oC, the impregnated resin to fold away from the graphite ring, so that the ring wear resistance is reduced; Second, the impregnated resin if improperly selected, so the establishment of the seal cooling system, which is mainly the formation of the wrong material selection. The corrosion of the film, its passivation film usually has the characteristics of the maintenance effect, but the metal sealing ring used in the material, such as stainless steel, cobalt, chromium alloy, etc. Its appearance of the passivation film in the end friction damage, it is difficult to generate a new film in the absence of oxygen conditions, select the corrosion-resistant impregnating resin, the choice of high-pressure impregnation, add the depth of impregnation is very necessary.

2, the oxidation of graphite ring. In the oxidizing medium, the end face in dry conflict or poor cooling, the onset of 350 ~ 40o ℃ temperature can make the graphite ring and oxygen reactions, the onset of CO, gas, can make the end face rough, and even cracking. Non-metallic ring in the chemical medium and the effect of stress together, will also be cracked.

 3, PTFE (teflon gasket) sealing ring corrosion. F4 filling such as glass fiber, first in the single thin area onset of cracks, and then to the longitudinal development, the onset of fracture, sealing ring cracks are usually radial dispersion type, can be one or more. Graphite powder, metal powder, etc. to improve its temperature resistance, wear resistance. Filled F4 ring corrosion mainly refers to the filling of the selective corrosion, dissolution or metamorphosis damage. Such as in hydrofluoric acid, glass fiber molecular thermal corrosion, so the filling of what should depend on the specific situation.