Mechanical seal selection guide

Mechanical seal selection guide Each type of mechanical seal can only function effectively when it is used within the specified range. Improper selection of mechanical seal will result in a significant reduction in sealing performance, shortened life, or even failure. The following is the selection guide for mechanical seals: Steps/Methods The medium pressure of the seal chamber P 　　P≤0.8MPa, select the unbalanced type, P≥0.5MPa, select the balanced type of mechanical seal. Mechanical seal selection guide Linear velocity V 　　 The linear velocity should be combined with pressure, temperature, medium characteristics, etc. to determine the spring form. The PcV value relates to the stability (vaporization) of the fluid film between the sealing surfaces and the wear resistance of the friction pair. In the absence of external cooling, the maximum operating temperature of the mechanical seal generally depends on the safe operating temperature of the auxiliary sealing material. The particularity of the medium 　　Some mediums will have special requirements for auxiliary sealing. For example, solvents and other mediums cannot use fluorine rubber, and mineral oil cannot use EPDM rubber. Users should pay special attention to it.　　1) Balanced type should be selected for low-viscosity media that is prone to dry friction; for high-viscosity media, forced transmission structure should be used.　　2) For strong corrosion, external PTFE bellows should be used for sealing. Note 1. The radial runout of the main shaft where the seal is installed should be less than or equal to 0.04mm (0.06mm), and the axial movement should be less than or equal to 0.3mm, and the corresponding parts of the shaft and static ring seat should be machined according to the requirements of the figure.　2. The parts of the sealed cavity, shaft, and mechanical seal should be cleaned, and there should be no pollution, bumps, scratches, and especially to prevent impurities, dust, and particles from being brought into the sealed cavity.　3. It is strictly forbidden to collide and savagely during installation, and the surface of the friction pair should be absolutely clean.　4. The static ring gland must have sufficient strength. Tighten the screws evenly during installation to ensure that its end face is perpendicular to the axis.　5. After installation, press the moving ring lightly by hand, it should be free to expand and contract and have a certain degree of flexibility; manual cranking should run freely.　6. Carry out a static pressure test to observe if there is any leakage.　7. Start trial operation, pay attention to whether there is abnormal sound.　 8. When the operating temperature exceeds 80°C, a forced circulation method should be used to cool the seal.　9. The sealed pipeline must be kept unblocked; dry friction is strictly prohibited. Keywords: mechanical seals, mechanical seals