Mechanical seals, also known as face seals, consist of a pair of sealing faces that are perpendicular to the axis of rotation. These faces maintain close contact with each other and slide relative to one another under the influence of fluid pressure and external mechanical forces. This interaction is supported by auxiliary seals, which help ensure a tight seal and prevent fluid leakage. One common issue is periodic leakage, often caused by excessive axial movement of the pump rotor. If the clearance between the auxiliary seal and the shaft is too tight, the rotating ring may not move freely, leading to wear between the stationary and rotating rings without proper compensation. To address this, during assembly, the axial play of the shaft should be kept below 0.1 mm, and the interference fit between the auxiliary seal and the shaft should be moderate. This ensures that the rotating ring can move smoothly on the shaft while maintaining a good radial seal. Another cause of leakage is insufficient lubrication on the sealing surface, which can lead to dry friction or damage to the sealing faces. To prevent this, the oil level in the lubrication chamber must be higher than the dynamic and static ring sealing surfaces, ensuring adequate lubrication. Periodic vibration in the rotor can also cause leakage, often due to misalignment between the stator and end caps, imbalance in the impeller and main shaft, cavitation, or damaged bearings. Proper alignment and balancing of the components are essential to reduce such vibrations. Leakage can also occur under high-pressure conditions. If the spring force and total specific pressure are too high, excessive pressure in the sealed cavity—especially over 3 MPa—can prevent the formation of a liquid film, leading to severe wear and heat generation. To mitigate this, the spring compression must be carefully adjusted according to specifications. High-pressure seals should use materials like cemented carbide or ceramics, and cooling and lubrication measures should be enhanced. Vacuum conditions during pump start-up or shutdown can also cause dry friction if the inlet is blocked or if gas is present in the medium. In such cases, using double mechanical seals can improve lubrication and enhance sealing performance. Leakage can also result from the properties of the medium itself. Particles and impurities in the fluid can damage the sealing faces, while weak acids or bases in the medium can degrade the auxiliary seals. To address this, it's important to keep the lower cover and oil chamber clean, avoid using unclean lubricants, and ensure the oil level in the seal chamber is above the sealing surface. Selecting the appropriate mechanical seal structure based on the medium is also crucial—such as using fluororubber for corrosive media and tungsten carbide-to-tungsten carbide friction pairs in environments with solid particles. Other causes include improper design, selection, or installation of the mechanical seal. For example, incorrect spring compression (within -2 mm to +2 mm) is critical. Too much compression increases end-face pressure and frictional heat, potentially causing thermal deformation and accelerated wear. Insufficient compression, on the other hand, leads to poor sealing. Additionally, chamfering and polishing the sealing gland helps prevent damage to the seals during assembly. In summary, mechanical seals are precision components that require careful consideration of various factors, including pump requirements, operating conditions, and the nature of the medium. Proper selection, installation, and maintenance are essential to ensure long-term, reliable operation.

N300(Rongguang)

N300(Rongguang) Chevrolet wuling N300

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