Detailed explanation of common sense of mechanical seal corrosion protection

Detailed explanation of common sense of mechanical seal corrosion protection Due to the special planning methods and working environment and conditions of mechanical seals, the shapes of mechanical seals damaged by corrosion are also varied. The common damage methods of mechanical seals such as PTFE seals and PTFE gaskets are mainly corrosion damage, thermal damage and mechanical damage. Corrosion damage during this period is more harmful. 1. Corrosion of metal ring 1. Uniform corrosion on the surface. If the outer surface of the metal ring touches the mechanical seal and touches the corrosive medium, and the metal itself is not resistant to corrosion, the appearance of corrosion will occur. The phenomenon is leakage, early wear, damage, and noise. Uniform corrosion of metal surface has two shapes: film-forming and non-filming. Metal corrosion without film is very dangerous, called stress corrosion cracking. Selecting surfacing hard alloy and sealing rings such as cast iron, tungsten carbide, titanium carbide, etc., will briefly appear stress corrosion Split. The corrosion process proceeds at a certain speed, which aggravates the galvanic corrosion. 2. Stress corrosion cracking. Under the combined effect of corrosion and tensile stress, the metal is a mechanical seal, which is wear-resistant. The corrosion of the filled F4 ring mainly refers to the selective corrosion, dissolution or disintegration damage of the filling. For example, in hydrofluoric acid, the glass fiber molecules are thermally corroded, and these cracks communicate all the sealed end faces, and immediately abrasion of the end faces increases the leakage. 2. Non-metallic ring corrosion 1. Graphite ring corrosion. The impermeable graphite ring impregnated with resin has three reasons for its corrosion: one is that when the end surface is overheated and the temperature is greater than 180oC, the impregnated resin will fold away from the graphite ring, which will reduce the wear resistance of the ring; second, if the impregnated resin The selection was incorrect, so the establishment of a seal factory for the sealed cooling system was mainly caused by the faulty selection of materials. Corrosion of the film, the passivation film usually has the characteristics of protective effect, but the materials used in the metal seal ring, such as stainless steel, cobalt, chromium alloy, etc. The passivation film on the outer surface is damaged by end surface friction, and it is new under the condition of lack of oxygen. It is very difficult to form a film. It is very necessary to choose a corrosion-resistant impregnating resin, select high-pressure impregnation, and add impregnation depth. 2. Corrosion of PTFE (tetrafluoroethylene gasket) sealing ring. Chemical changes will occur in the medium, and the wear resistance will also be reduced; third, the depth of resin impregnation is not possible. When the impregnated layer is worn away, the wear resistance will decrease. F4 filled with glass fiber, first cracks in the thin area, and then develops in the depth, cracks occur. The seal ring cracks are usually radially divergent, but there can be one or more. Graphite powder, metal powder, etc. to improve its temperature resistance and wear resistance. The corrosion of the filled F4 ring mainly refers to the selective corrosion, dissolution or disintegration damage of the filling. For example, in hydrofluoric acid, the glass fiber molecules are thermally corroded, so what to fill depends on the specific situation. 3. Oxidation of graphite ring. In an oxidizing medium, when the end face is dry or poorly cooled, a temperature of 350-40o ℃ can cause the graphite ring to react with oxygen, generate CO and gas, and make the end face rough or even split. The non-metallic ring will also split under the combined effect of chemical media and stress. Keywords: mechanical seals, mechanical seals