Mechanical seal corrosion protection common sense detailed explanation

Because of the special construction of mechanical seals and the different working environments and conditions, the shape of corrosion damage is also varied. Common damages of mechanical seals such as PTFE seals and PTFE gaskets are mainly corrosion damage, mechanical damage of the thermal loss slurry pump and mechanical damage. Corrosion damage is more harmful during this period.
    1. Metal ring corrosion

    1, the appearance of uniform corrosion. If the outer surface of the metal ring is in contact with the corrosive medium, and the mechanical seal metal of the oil pump is not corrosion-resistant, the surface corrosion will occur. The phenomenon is leakage, pre-wear, damage, sound, and the like. The metal surface is uniformly corroded in both film-forming and film-free shapes. The metal-free corrosion of the film is dangerous. It is called stress corrosion cracking. It is made of hardfacing alloy and cast iron, tungsten carbide, titanium carbide and other sealing rings. break. The corrosion process is carried out at a certain double-open pump mechanical seal speed, which increases the galvanic corrosion.

    2, stress corrosion breaks. The wear resistance of the metal under the combined effect of corrosion and tensile stress. Corrosion filling the F4 ring mainly refers to the selective corrosion, dissolution or enthalpy damage of the filling. For example, in hydrofluoric acid, the glass fiber molecules are thermally corroded, and these cracks communicate the entire sealing end face, which accelerates the wear of the end face and adds the amount of leakage.

    2. Non-metallic ring corrosion

    1, graphite ring corrosion. The company information network refers to the impervious graphite ring impregnated with resin. Its corrosion has three reasons: First, when the end face is overheated and the temperature is greater than 180oC, the impregnated resin should be folded away from the graphite ring to reduce the wear resistance of the ring; Second, if the impregnated resin is improperly selected, the establishment of the sealed cooling system is mainly due to the selection of materials. The film-forming corrosion, its passivation film usually has the characteristics of maintenance effect, but the materials used for the metal sealing ring, such as stainless steel, cobalt, chrome alloy, etc., the surface of the passivation film is damaged in the end face friction, under the condition of lack of oxygen The film is difficult to form, and the corrosion-resistant impregnating resin is selected. High-pressure impregnation is used, and it is necessary to add the impregnation depth.

    2. Oxidation of the graphite ring. In an oxidizing medium, when the end face is in conflict or poor cooling, a temperature of 350 to 40 ° C can cause the graphite ring to reverberate with oxygen, and CO, gas can cause roughening of the end face, or even break. Non-metallic rings will also break under the effect of chemical media and stress.

    3, corrosion of PTFE (tetrafluoroethylene gasket) sealing ring. Chemical changes will occur in the medium, which will also reduce the wear resistance. Third, the resin impregnation depth will not work. When the impregnation layer is removed, the wear resistance will be reduced. F4 is filled with glass fiber, first cracks occur in a thin area, and then develops in depth, and the crack occurs. The seal ring crack is usually radial divergence type, and may be one or more. Graphite powder, metal powder, etc. to improve its temperature resistance and wear resistance. Corrosion filling the F4 ring mainly refers to the selective corrosion, dissolution or enthalpy damage of the filling. For example, in hydrofluoric acid, glass fiber molecules are thermally corroded, so what should be filled depends on the specific conditions.