Thread Content
Regarding the installation requirements and technical improvements for FY-type submersible pumps: Source – China Chemical Machinery Network. The FY-type submersible corrosion-resistant centrifugal pump is suitable for transporting corrosive media, and therefore it is widely used in industries such as the chemical industry. In our use of this pump, we found that its graphite-polytetrafluoroethylene bearing shells wear out quite easily; sometimes even the pump shaft bends. As a remedy, we produced large quantities of replacement parts, but this approach not only led to significant waste of material but also caused considerable inconvenience to production due to the frequent replacements. To this end, our technical staff conducted thorough analysis and research, and found that the size of the pump shaft is sufficient to withstand the torque that needs to be transmitted. Since the pump is installed vertically and does not experience any bending moments, then how does the pump shaft bend? Based on the summary, we have reached the following conclusions: 1. The relationship between pump installation and its performance. Actual measurements show that for pumps whose shafts are bent, their verticality is poor during installation. If the upper end of the intermediate pump tilts, the graphite-polytetrafluoroethylene bearing shells will wear out first at the diagonal positions, causing the stainless steel sleeve and the graphite-polytetrafluoroethylene bearing shells to operate abnormally. As the wear of the bearing shells increases, the gap between the sleeve and the bearing shells also grows, causing deflection at the lower end of the \"cantilevered\" pump shaft. This occurs when the center of gravity of the impeller coincides with the rotational center of the pump shaft. No matter how well the static balance is adjusted in the original design, significant unbalanced inertial forces will still be generated. The rotational speed of FY-type submersible pumps is generally 2900 rmin, so the inertial force it can generate is indeed very large. When this unbalanced force exceeds the weight of the rotor, the moving parts of the bearings will suffer severe wear. As a result, wear of the bearings leads to the generation of unbalanced inertial forces, and the increase in these unbalanced inertial forces in turn exacerbates the wear of the bearing shells; this vicious cycle becomes increasingly severe. When the unbalanced force increases to a certain level, it will eventually cause the pump shaft on which the \"cantilever\" is mounted to bend. Therefore, poor verticality of the pump shaft during installation is the fundamental cause of its bending. In the original structure, the pump shaft is enclosed by branch pipes, making it difficult to measure its verticality. The solution is to keep the verticality at the support pipe within 0.1 mm, which indeed prevents the pump shaft from bending in practical use. By improving the installation accuracy, such failures have significantly decreased in different environments. 2. Graphite PTFE bearing shells: As mentioned above, if the pump shaft is slightly tilted during installation, the cylindrical bearing shells will wear out quickly. However, if the bearing shells are modified to have a spherical structure, then regardless of whether the pump shaft is tilted during installation, the concave spherical surface of the bearing shells and the convex spherical surface of the pump shaft sleeve will always be in uniform contact and experience even wear. This will **extend the service life of the polytetrafluoroethylene bearing shells, and it will also reduce the requirements for pump installation; even if the verticality tolerance of the support pipe is increased to 1 mm, the pump shaft will not bend. It should also be noted that, for ease of installation, a notch for the mounting sleeve should be made in the inner hole of the graphite-polytetrafluoroethylene bearing shell; its length should be slightly greater than the diameter of the sleeve’s ball, while its width should be slightly greater than the length of the sleeve, so that the convex sleeve can be smoothly inserted into the concave bearing shell. 3. Conclusion: After making the aforementioned improvements to the installation and use of FY-type submersible pumps, their operational efficiency was greatly enhanced, a significant amount of labor and resources were saved, and the normal progress of production was ensured; the results were very noticeable. The FY type submersible pump is a mature product with high demand. If the manufacturer pays sufficient attention to its installation, more satisfactory results can certainly be achieved. On the other hand, it is hoped that the relevant water pump manufacturers will make some beneficial attempts by using spherical graphite PTFE bearing shells in place of traditional cylindrical ones, thereby improving the performance of these pumps.