【Equipment Reliability Improvement】Replaced the packing seal with a ceramic seal to address seal leakage in the acrylic acid stock pump

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Anqing Petrochemical’s Acrylic Fiber Department Solves the Problem of Seal Leakage in Pump Motors Through Minor Modifications 2016-12-15 Source: Petrochemical News “Since the mechanical seals were replaced with these new ceramic composite seals, none of the 8 pumps used for pressurizing the raw material have experienced seal leakage after nearly 3 months of operation.” ”“I never expected that such a minor modification could yield such noticeable results.” On December 13, in the original liquid supply area for spinning at the acrylic fiber department of Anqing Petrochemical, workers were excitedly discussing a technical improvement measure that had been implemented recently. In the raw material section of the polymerization unit in the acrylic fiber department, glue leakage has always been a major problem for equipment managers. It not only leads to material loss and increased consumption but also causes environmental pollution. The root cause of glue leakage is mostly due to seal failure in the pumps; therefore, addressing the seal leaks in these pumps has become a top priority in preventing glue leakage. Since the original liquid is a viscous gel-like fluid, its viscosity increases as the temperature drops; it also has the tendency to solidify and form clumps when exposed to water. The chemicals contained in it can erode and wear away seals, leading to corrosion of the sealing elements, a decline in their functionality, and ultimately leakage. The glue leakage problems with the original liquid booster pump, the second-stage filter transfer pump, and the spinning return slurry pump in this department have persisted. Under stable production conditions, the leakage is not noticeable. During unstable production, especially when the spinning speed fluctuates, pressure variations in the production system can easily lead to seal leakage. Not only that, but when a pump fails and it is necessary to switch to a backup pump, the liquid medium remaining in the backup pump itself and the pipelines experiences a change in viscosity, resulting in operating resistance that is much greater than the pump’s normal operating capacity; this leads to wear of the pump shaft and leakage of fluid. The original seals for pumps such as the stock solution booster pump are packing seals. Leakage can be controlled by tightening the packing, but in many cases this tightening increases the operating resistance of the pump, causes the packing to overheat and burn out, resulting in greater leakage. Sometimes, the increased resistance of the pump also leads to the motor tripping, forcing the spinning process to stop. Over the years, the equipment managers in the acrylic fiber department have been exploring, starting with the materials of sealing elements, which sealing material is most suitable for addressing the problem of seal leakage. They attempted to use mechanical seals on multiple occasions. During the experiments, due to the limitations of the properties of the original liquid, it was not possible to cool the mechanical seals using water or air supply, as is done with conventional mechanical seals. This led to a short service life for these seals, high maintenance costs, and other related problems. During that time, they tried sealing elements made of other materials on several occasions, but none were able to effectively resolve the sealing leakage issue. This year, after consulting with various experts and obtaining relevant certifications, they decided to try using new ceramic composite seals. Taking advantage of the downtime for major repairs, they conducted tests on 8 primary liquid booster pumps, replacing the mechanical seals on these pumps with ceramic composite seals. After nearly 3 months of trial operation, the modification was successful – none of the pumps experienced seal leakage, which proved that the hardness, compressive strength, and chemical stability of ceramic composite seals meet the requirements for sealing primary liquid pumps. They plan to gradually replace the sealing elements of pumps such as the secondary filter transfer pump and the slurry return pump, in order to completely resolve the problem of glue leakage. (Zhang Lingling, Zhang Hongqiu, He Wensheng)