Chemical pump mechanical seal device essentials and leakage analysis

Reasons for leakage of chemical pump mechanical seals The proportion of leakage of mechanical seals accounts for more than 50% of all chemical pump repairs. The work of mechanical seals directly affects the normal operation of centrifugal pumps. Leakage of mechanical seals can be roughly classified into the following: Leakage due to pressure: (1) Leakage of mechanical seals consisting of high pressure and pressure waves. As the ratio of the tension spring to the pressure and the total specific pressure is too large and the pressure in the seal chamber exceeds 3 MPa, the pressure at the seal face is too large. The liquid film is difficult to construct, and the sealing end surface is worn out with severe heat generation, which constitutes a thermal deformation of the sealing surface. Countermeasures: When the device is mechanically sealed, the compression of the spring must be carried out according to the rules. It is not allowed to have excessive or too small phenomenon. The mechanical seal under high pressure conditions should adopt the measures. In order to make the force on the end face reasonable and minimize deformation, it is possible to use materials with high compressive strength such as cemented carbide and ceramics, and to strengthen the cooling lubrication method. (2) The mechanical seal leaking pump working in the vacuum condition constitutes a negative pressure in the sealing chamber during the starting and stopping process due to the pump inlet blockage and the pumping medium containing gas. Caused by the dry end of the dry face conflict, built-in mechanical seal will leak (water) phenomenon, the difference between the vacuum seal and the positive pressure seal is the difference in the direction of the sealing target, and the mechanical seal also has its adaptability in a certain direction. Countermeasures: Use double-faced mechanical seals, which will help improve the lubrication conditions and improve the sealing function. 2. Periodic leakage: (1) Large axial motion of the pump rotor, large amounts of interference between the seal and the shaft, and dynamic rings cannot Sensitive movement on the shaft. After the pump turns over and the static and dynamic rings are worn, no compensation displacement can be obtained. Countermeasures: When the device is mechanically sealed, the axial axial movement of the shaft should be less than 0.1mm, and the amount of interference between the auxiliary seal and the shaft should be moderate. While ensuring the radial seal, the ring device can be moved sensitively on the shaft after ensuring the radial seal ( Pressing the ring against the spring will bounce back freely.) (2) The lack of lubricating oil on the sealing surface causes dry crushing or roughing of the sealing face. Countermeasures: The height of the oil in the oil chamber cavity should be added to the sealing surface of the moving and static rings. (3) Rotor periodic vibration. The reason is that the stator is not aligned with the upper and lower end caps or the impeller and the main shaft are not balanced, cavitation or bearing damage (wear), this will shorten the seal life and leakage. Countermeasures: The above problems can be corrected based on the repair specifications. Third, due to media-induced leakage: (1) After most of the submersible pump mechanical seal dismantling, static ring and dynamic ring assisted seals are inelastic, and some are now decayed, constitute a lot of leakage of the machine seal even There is a phenomenon of grinding axis. Due to the corrosive effect of high temperature and weak acid and weak alkali in the sewage on the rubber seals assisted by the static ring and the moving ring, the mechanical leakage is too large. The data on the dynamic and static ring rubber seals is nitrile-40, which is not high temperature resistant. Not acid and alkali, when the sewage is acidic alkaline corrosion. Countermeasures: For corrosive media, rubber parts should use high temperature, weak acid, weak base fluororubber. (2) Leakage of mechanical seal caused by solid particles Impurities If the solid particles enter the sealing face, it will scratch or accelerate the wear of the sealing face. The accumulation rate of scale and oil on the shaft (set) external surface exceeds the wear speed of the collision pair, resulting in The moving ring cannot compensate for the wear displacement. The working life of the hard-to-hard pair of collisions is longer than that of the hard pair of graphite collisions, since the solid particles will be embedded in the sealing surface of the graphite sealing ring. Countermeasures: In the direction of the simple entry of solid particles, a tungsten carbide-to-tungsten carbide mechanical seal should be used. Chemical pump mechanical sealing device essentials Chemical centrifugal pump needs to select different mechanical seals according to the different working conditions. The requirements of different mechanical seals are different. Let's abstractly introduce the points of the mechanical seal device: IH horizontal stainless steel chemical Pump 1), the radial runout of the equipment shaft should be ≤ 0.04 mm, the amount of axial turbulence does not allow greater than 0.1 mm; 2), the sealing part of the equipment should be kept clean in the device, the sealing parts should be cleaned, the sealing end surface is intact, To prevent impurities and dust from being carried into the sealing area; 3) To prevent collisions or blows in the process of the installation so as to avoid damage caused by mechanical seal damage and seal failure; 4) The exterior of the device that touches the seal should be coated with a layer Clean mechanical oil, so that the device can be smooth; 5) When the device is installed with a static ring, it is necessary to tighten the screw and force it to be even to ensure the straightness of the end surface of the static ring and the axis of the shaft; 6) After the device, push the ring by hand , Can make the moving ring sensitive movement on the shaft, and there must be flexibility; FB, AFB corrosion-resistant centrifugal pump 7), the device after the hand rotation axis, the shaft should be no light and heavy feeling; 8), equipment in It is necessary to fill the medium before work to avoid dry collision and seal failure;

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