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 not appropriate or if the seals are used incorrectly, 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 spades to avoid damaging the sealing elements. 2) If mechanical seals are present at both ends of the pump, care must be taken during disassembly to avoid neglecting one aspect while focusing on another. 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 retightened and used again. Because after loosening, the original operating path of the friction pair changes, which easily compromises the sealing performance of the contact surface. 4) If the sealing element is stuck by dirt or deposits, these deposits must be removed before disassembling the mechanical seal. 2. Precautions during installation: 1) Before installation, carefully check whether there are sufficient numbers of sealing parts, and whether all components are intact; in particular, inspect 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 related assembly contact surfaces must be thoroughly cleaned with acetone or anhydrous alcohol before installation. Keep the area clean during installation; in particular, the moving and stationary rings as well as the auxiliary sealing elements must be free from any impurities or dust. Coat the surfaces of the moving and stationary rings with a layer of clean engine oil or turbine oil. 4) Tightening the gland should be carried out after the coupling has been aligned. The bolts should be tightened evenly to prevent skewing of the gland cross-section; a feeler gauge or specialized tool should be used to check each point, with the error not exceeding 0.05 millimeters. 5) Check the fit clearance (and concentricity) between the gland and the outer diameter of the shaft or sleeve; it must be even around the perimeter, and a feeler gauge should be used to ensure that the tolerance at each point is no more than 0.10 millimeters. 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 pressure will be insufficient to provide a sealing effect; once the spring is installed, it must be able to move freely within the spring seat. When using a single spring, pay attention to its winding 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 end face of the stationary ring, ensure that it is perpendicular 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, but avoid any contact between them. 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.