Proper installation and removal of mechanical seals

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Installation and removal of mechanical seals Mechanical seals are one of the most effective methods for sealing rotating machinery. They require high precision in manufacturing, especially regarding the moving and stationary rings. If the installation and removal methods are 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: When removing a mechanical seal, it is strictly prohibited to use hammers or spades to avoid damaging the sealing elements. 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. For mechanical seals that have been in use, if the sealing surfaces shift 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 integrity of the contact surface. If the sealing element is stuck by dirt or deposits, these deposits must be removed before the mechanical seal can be disassembled. 2. Precautions during installation: 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. Check whether the chamfers on the shaft sleeve or gland are appropriate; if not, they must be trimmed. All components of the mechanical seal, as well as the relevant assembly contact surfaces, must be thoroughly cleaned with acetone or anhydrous alcohol before installation. Cleanliness should be maintained during installation, especially the moving and stationary rings as well as the auxiliary sealing elements must be free of impurities and dust. Coat the surfaces of the rotating and stationary rings with a layer of clean engine oil or turbine oil. 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 special tool should be used to check each point, with the error not exceeding 0.05 millimeters. 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. 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. After installation, the moving ring must be able to move freely; it should return automatically after being pressed against the spring. 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. During installation, it is absolutely not allowed to strike the sealing elements with tools directly; if striking is necessary, special tools must be used to do so in order to prevent damage to the sealing elements. All sealing rings should be coated with lubricants such as soapy water during assembly, this helps to avoid damaging the rubber rings during the process. Lubricant is applied between the sealing surfaces of the stationary and rotating rings to prevent wear of these surfaces before the water pump is started up. When assembling the floating ring, be careful not to knock over the floating ring spring, as this could affect the floating performance of the ring if the spring is displaced. After the floating ring is assembled, it can be gently pressed to determine whether it has good floating performance. When installing the seal, handle it gently to avoid damaging it; clean both the seal and the cavity thoroughly before installation. When tightening the mechanical seal gland, the bolts should be subjected to even force to prevent damage to the mechanical seal due to uneven loading. After the quick-install mechanical seal has been fully assembled, be sure not to forget to fix the positioning piece so that its radial movement path is kept away from the shaft. Since the media that mechanical seals are designed to seal vary, and the temperatures of cold water and hot water differ, as well as whether the sealing medium is corrosive and the pressure inside the chamber varies, the design of mechanical seals changes accordingly, and the maintenance procedures also differ. Some experiences have been gained through the maintenance of mechanical seals: it is necessary to assemble them properly, and cleaning and inspection must not be overlooked. First check the two rings, then the shaft; don’t miss any scratches or cracks. Finally, check the rubber ring and make sure to see the diameter of the air pores clearly. Various dimensions need to be measured, and the gap between the two rings must be adjusted properly. The tension must be checked; the small spring is key. The bolts should be subjected to even stress; handle them gently