Details of replacement of mechanical seals for various pumps and methods for replacement of mechanical seals
In order to ensure the normal operation of the pump, the mechanical seal is generally replaced once every three months. This paper describes in detail how to replace the mechanical seal and the steps of replacing the mechanical seal for your reference.
Tools and materials
Adjustable wrench, socket wrench, slotted screw driver, slotted screwdriver, sandpaper, clean cotton cloth, grease
Maintenance table, a new set of mechanical seal.
The method of changing the mechanical seal of water pump: 1. Install the left part first; install it on the sealing plate; 2. Then install the moving ring on the right side, and the sealing surface of the moving ring and the static ring should be clean; 3. Install the flat key and impeller, and install the gasket and nut. Before installation, it is necessary to carefully check whether the number of assembly sealing parts is enough, whether the components are damaged, especially whether the dynamic and static rings are damaged, cracked and deformed. If there is any problem, repair or replace with new spare parts.
Check whether the chamfering of shaft sleeve or gland is proper, if not, it must be trimmed.
All components of mechanical seal and its related assembly contact surface must be cleaned with acetone or anhydrous alcohol before installation. During installation, it should be kept clean, especially the dynamic and static rings and auxiliary sealing elements should be free of impurities and dust. Apply a layer of clean engine oil or turbine oil on the surfaces of moving and stationary rings.
Tighten the gland after the coupling alignment. The bolts should be tightened evenly to prevent the gland section from skewing. Check each point with a feeler gauge or special tool, and the error is not more than 0.05mm.
Check the fit clearance (and concentricity) between the gland and the shaft or shaft sleeve outer diameter, and ensure that it is even all around. Use a feeler gauge to check that the tolerance of each point is not greater than 0.10 mm.
The amount of spring compression should be carried out according to the regulations. It is not allowed to have too large or too small phenomenon. The error is required to be ± 2.00 mm. If it is too large, the specific pressure of the section will be increased and the wear of the section will be accelerated. If it is too small, the specific pressure will not be enough to play a sealing role. After the spring is installed, it should move flexibly in the spring seat. When using a single spring, pay attention to the rotation direction of the spring. The rotation direction of the spring should be opposite to the rotation direction of the shaft.
After installation, the moving ring must be able to move flexibly, and it can automatically spring back after pressing the moving ring to the spring.
First, the static ring seal ring is set on the back of the stationary ring, and then installed into the seal end cover. Pay attention to protect the section of the static ring, ensure the perpendicularity of the section and the center line of the end cover, and align the anti rotation groove on the back of the static ring with the anti rotation pin, but do not make them contact each other.
During the installation process, it is not allowed to directly knock the sealing elements with tools. When it is necessary to knock, special tools must be used to knock to prevent damage to the sealing elements
During assembly, all sealing rings should be coated with soap water and other lubricants to avoid damage to rubber rings during assembly. The sealing surfaces of the dynamic and static rings are coated with grease to prevent wear of the sealing surfaces of the dynamic and static rings before the pump is started.
When assembling the floating ring, be careful not to knock down the floating ring spring, so as not to affect the floating performance of the floating ring after the spring is knocked down. After the floating ring is assembled, you can press the floating ring gently to determine whether it has good floating performance.
When installing the seal, it should be handled with care to prevent damage to the seal. The seal and cavity should be cleaned during installation.
When fastening the mechanical seal gland, the fastening bolt should be evenly stressed to prevent the mechanical seal from being damaged by uneven force. For the quick installation mechanical seal, do not forget to fix the position far away from the shaft of the radial moving path of the locating piece after the whole assembly.
Because the sealing medium of mechanical seal is different, the temperature of cold water and hot water is different, whether the sealing medium is corrosive, and the pressure in the chamber is different, the design of mechanical seal will be different, and the maintenance process will also be different,
Mechanical seal maintenance process summed up some experience: mechanical seal assembly, cleaning and inspection do not forget. First look at the two rings and then look at the shaft. Do not leak the scar and crack. Finally, when looking at the apron, the pore diameter should be clear. Various dimensions need to be measured and the clearance between the two rings should be adjusted. The tightening force must be checked, and the small spring is the key. The stress of bolt should be uniform, and it should be handled with care.
The mechanical seal of water pump is one of the most effective ways to seal the body of rotating machinery. Its machining accuracy is relatively high, especially for the dynamic and static rings. If the disassembly method is not suitable or used improperly, the assembled mechanical seal will not only fail to achieve the purpose of sealing, but also damage the assembled sealing elements.
Precautions for mechanical seal disassembly
When disassembling the mechanical seal, do not use the hand hammer and flat shovel to avoid damaging the sealing elements.
If there are mechanical seals at both ends of the pump, care must be taken in the disassembly process to prevent one from losing the other.
For the mechanical seal that has been working, if the sealing surface moves when the gland is loose, the dynamic and static ring parts should be replaced instead of being tightened again. Because after loosening, the original running track of friction pair will change, and the sealing of contact surface is easy to be damaged.
If the sealing element is bonded by dirt or agglomerate, the mechanical seal shall be disassembled after removing the condensate.
Mechanical seal pumps are: chemical pumps, centrifugal pumps, multi-stage pumps, self-priming pumps and a variety of sewage pump products