Study on the Service Life of Mechanical Seals for Pots

　　 1. Preface

　　Kettle-type machinery is a crucial piece of system equipment for industrial production. If leakage occurs during the production and application phase, it will adversely affect product quality and release hazardous gases that are toxic, explosive, and flammable, posing significant risks to both the ecological environment and the equipment system itself. Moreover, if the kettle-type machinery undergoes repeated maintenance, the materials inside must be transferred out and the tank subjected to necessary cleaning procedures. This not only leads to substantial waste but also reduces the efficiency of machinery utilization and lowers product yield. Furthermore, kettle-type machinery features a relatively complex sealing system, requiring high-level maintenance costs and inevitably prolonging production downtime. Therefore, it is essential to effectively extend the service life of mechanical seals and ensure they remain in good, stable working condition, thereby generating significant benefits and enhancing the overall level of practical production applications.

　　 2. Mechanical Seal Failure Issues in Kettles

　　During the mechanical operation phase of the reactor vessel, some processes require raising the temperature to a range between 160 and 180 degrees Celsius and maintaining a constant temperature for a certain period. Meanwhile, the pressure inside the reactor should be controlled within the range of 1 to 1.5 megapascals. Due to the frequent fluctuations in temperature, both the pressure inside the reactor and the pressure in the mechanical seal cavity will experience long-term variations. During the heating phase, as the reactor pressure gradually increases, gaseous substances may leak into the seal cavity. Conversely, when the temperature drops, the sealing fluid from the mechanical seal cavity may seep back into the reactor, causing the mechanical seal below it to fail more rapidly. During the operational phase, the seal cooling water must be turned off, which could lead to dry friction between the stationary and rotating rings during operation, significantly impacting the overall service life of the mechanical seal.

　　 3. Scientific Strategies for Extending the Service Life of Mechanical Seals Used in Reactor Vessels

　　3.1 Utilizing an auxiliary sealing system to extend service life.

　　To ensure that the vessel-mounted mechanical equipment always operates in a stable and reliable condition, an auxiliary sealing system can be employed to provide a smooth connection between the outlet pipe of the balance tank and the mechanical seal chamber. During operation, as the gas-phase pressure inside the vessel gradually increases, the gaseous medium will permeate into the mechanical seal chamber, causing the internal pressure to rise accordingly. The outlet of the seal chamber, the inlet of the balance tank, and the industrial air inlet should all be sealed using pre-fabricated needle valves. This ensures that the pressure differential between the vessel and the mechanical seal chamber remains stable at all times, effectively preventing continuous leakage of the gaseous medium from the vessel into the mechanical seal chamber, which could otherwise lead to adverse damage to the lower sealing surface and premature failure of the seal.

　　3.2 Effectively introduce balance tanks to optimize the application of mechanical seals for reactors.

　　During the operation phase of the reactor machinery, first open the valve at the mechanical seal water outlet, then open the valve at the mechanical seal water inlet. This will ensure thorough cleaning of the sealing cavity, effectively preventing abrasive wear caused by the formation of debris on the stationary and rotating rings. Once the water flowing out of the mechanical seal cavity gradually becomes clear, close the inlet valve and open the industrial air inlet valve. This will cause the liquid level in the balance tank to continue dropping. When the liquid level drop can be observed through the balance tank’s sight glass, close the mechanical seal water outlet valve. After the pressure gauge reading stabilizes, close the industrial air inlet valve. During the operation phase, keep the mechanical seal water inlet, outlet, and industrial air inlet valves closed; however, keep the other mechanical seal water inlet valve—connected to the mechanical seal—open. If a leak is detected in the balance tank, close the open mechanical seal water inlet valve to ensure the continued healthy operation of the reactor machinery.

　　3.3 Optimization of Mechanical Overall Sealing Maintenance and Inspection for Reactor Vessels

　　After the bearing mounted above the mechanical seal components for reactors has been in service for a certain period, its internal clearance will gradually increase. Consequently, the dimensions of the inner spacer sleeve should be reduced accordingly. During the maintenance and inspection phase, feeler gauges should be used to precisely measure the exact amount of misalignment. At the same time, the specific dimensions of the outer spacer sleeve should be customized, and the precise distance between the inner race of the bearing should be measured against established standards. Generally, measurements should be taken at three points spaced 120 degrees apart, and the average value calculated. Subsequently, the inner spacer sleeve should be machined to match these measured dimensions, thereby ensuring an appropriate preload. During the overhaul of the mechanical balancing sleeve for reactors, it is essential to ensure that the sleeve undergoes proper grinding treatment, with its surface roughness meeting the specified standards. This will optimize the sealing performance of both the balancing sleeve and the O-ring, effectively extending the service life of the balancing sleeve. The stationary ring of the mechanical seal assembly should have a close fit with its stationary ring seat, featuring a small clearance that allows the stationary ring to move and rotate freely and smoothly. Conversely, inadequate handling may cause the stationary ring to be subjected to spring forces, preventing it from evenly pressing the sealing O-ring over its entire circumference. Moreover, this could also result in the stationary ring and the rotating ring failing to maintain the proper perpendicularity relative to the main shaft axis. Under the influence of corrosive gases, the O-ring seal may easily develop small pits. Therefore, during the overhaul phase, such pits must be carefully addressed; a steel brush can be used for high-quality rust removal followed by thorough cleaning. Additionally, stainless steel welding rods can be employed to effectively build up the sealing groove, after which a lathe can be used to finish machining the groove, ensuring a tight seal between the stationary ring and its seat. After the mechanical seal assembly for reactors has been in service for a certain period, rust and scale buildup may occur internally. During disassembly, hammering can lead to improper deformation of the thrust ring, seat, and balancing sleeve. Thus, during the maintenance and repair phase, methods such as filing, deburring, and scraping can be utilized to ensure that the stationary ring and its seat can slide smoothly and freely within the balancing sleeve without causing any damage or impairment to the balancing sleeve itself, thereby meeting the required precision standards for fitting.

　　In short, optimizing mechanical seals for reactors is of paramount importance. Given the specific structural characteristics of reactor mechanical seals and the sealing failure issues that often arise, we must adopt scientifically sound and effective countermeasures—such as introducing auxiliary sealing systems, making rational use of balance tanks, and conducting thorough maintenance and inspection of the entire sealing system—if we are to enhance the operational efficiency of reactor machinery, extend the service life of their seals, and thereby generate significant benefits and achieve high-quality, healthy, and sustainable development.