Precautions for disassembling and assembling mechanical seals

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Mechanical seals are one of the most effective methods for sealing rotating machinery. They require a high level of precision in their manufacturing, especially with regard to the moving and stationary rings. If the installation method is inappropriate or if the seals are not used correctly, the resulting mechanical seal will not only fail to provide proper sealing but may also damage the sealing components. 1. Precautions during disassembly: 1) When removing the mechanical seal, it is strictly prohibited to use hammers or flat shovels to avoid damaging the sealing elements. 2) When there are mechanical seals at both ends of the pump, care must be taken during disassembly to avoid neglecting one while attending to the other. 3) For mechanical seals that have been in use, if the sealing surface moves when the gland becomes loose, the stationary and rotating ring components should be replaced; they should not be tightened again and used continuedly. After loosening, the original operating trajectory of the friction pair changes, making it easy for the sealability of the contact surface to be compromised. 4) If the sealing elements are adhered by dirt or condensate, the condensate must be removed before disassembling the mechanical seal. 2. Precautions during installation
1) Before installation, carefully check whether the number of sealing components is sufficient, and whether any components are damaged. In particular, check the moving and stationary rings for any defects such as scratches, cracks, or deformation. If there is a problem, it needs to be repaired or replaced with new spare parts. 2) Check whether the chamfer on the shaft sleeve or gland is appropriate; if not, it must be trimmed. 3) All components of the mechanical seal and their relevant assembly contact surfaces must be thoroughly cleaned with acetone or anhydrous alcohol prior to installation. The installation process should be kept clean; in particular, the moving and stationary rings as well as the auxiliary sealing elements must be free of impurities and dust. Apply a layer of clean machine oil or turbine oil to the surfaces of the moving and stationary rings. 4) The upper gland should be tightened after the coupling has been aligned. The bolts should be tightened evenly to prevent any skewing of the gland cross-section. Use a feeler gauge or special tools to check each point; the tolerance should not exceed 0.05 mm. 5) Check the clearance (and concentricity) between the gland and the outer diameter of the shaft or bushing; it must be uniform all around. Use a feeler gauge to verify that the tolerance at each point does not exceed 0.10 mm. 6) The compression amount of the spring must be in accordance with the specified values; it is not allowed to be too large or too small. The allowable error is ±2.00 millimeters, as a larger compression amount will increase the stress on the cross-section and accelerate its wear. If it is too small, the specific pressure will be insufficient to ensure a proper seal; after installation, the spring must move freely within the spring seat. When using a single spring, pay attention to its rotation direction; it should be opposite to the rotation direction of the shaft. 7) After installation, the moving ring must be able to move freely; it should return automatically after being pressed against the spring. 8) First, fit the static ring seal ring around the back of the static ring, and then insert it into the sealing end cover. Be careful to protect the cross-section of the stationary ring, ensure its perpendicularity to the centerline of the end cover, and align the anti-rotation groove on the back of the stationary ring with the anti-rotation pin, ensuring that they do not come into contact with each other. 9) It is strictly prohibited to strike the sealing element directly with tools during installation; if striking is necessary, special tools must be used to avoid damaging the sealing element.