Leakage problems of mechanical seals and maintenance countermeasures

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Mechanical seal technology relies on a pair or several pairs of end faces that slide relative to each other perpendicular to the shaft; these end faces remain in contact even under the pressure of the fluid and other forces exerted by the compensation mechanism, and auxiliary sealing devices are used to prevent leakage. Mechanical seals ensure that the contact surface of the stationary ring and the rotating ring remain in constant contact even during movement. Sealing is achieved by creating an appropriate specific pressure between the stationary and rotating rings, as well as by maintaining a layer of liquid film between them. The main components of a mechanical seal include face seal components such as the stationary ring and the rotating ring ； Auxiliary roles are also played by various types of sealing rings such as O-type, U-type, and X-type ； Compensation components include springs, push rings, etc ； The transmission components include transmission screws and transmission pins, etc ； Fastening components are numerous, including push rings, spring seats, gland plates, and set screws, among others. So, in what types of equipment are mechanical seals mostly used? Generally, mechanical seals are used in equipment such as centrifugal pumps, centrifuges, compressors, and reaction vessels. It has good sealing performance, low leakage, a long service life, low energy consumption, and requires little maintenance. Mechanical seals also exhibit excellent adaptability; they are generally capable of functioning in automated production environments as well as in harsh conditions such as high temperatures and pressures, along with other demanding requirements regarding sealing performance. Sealing leakage issues: The common types of leakage in mechanical seals include the following: 1. Leakage caused by damage to the flatness of the sealing surfaces. Damage to these surfaces usually results in uneven scratches and breaks on their surface. The cause may be deformation or damage to the pump’s seal box and the stirrer’s head, or uneven bolt tightening, which leads to deformation of the sealing surface of the static ring and ultimately results in leakage. It is also possible that changes in temperature during the hot fitting of the sliding components, along with differences in thermal expansion, cause changes in the shape of the sealing surface. The sealing performance will also be damaged as a result, leading to leakage problems. 2. Leaks caused by damage to the lubricity of the sealing surface. The lubricity of the end-face seal is also very important; in addition to relying on the liquid film at the end face for sealing, lubrication is necessary as well to ensure proper operation. Once the liquid film on the end face is broken, it will cause immediate wear and increased roughness of the friction sealing surface; in some cases, even hard materials can develop cracks and other serious defects. When the temperature of the sliding friction surface rises suddenly, if the heat accumulation cannot be removed immediately, it will lead to the evaporation of the sealing fluid and the disappearance of the lubrication film, thereby causing dry friction. Thousand-friction can easily damage the sealing surfaces and create many potential sources of leakage. 3. Leakage caused by operational damage: The rotating ring and the stationary ring of a mechanical seal device rotate together with the shaft; they perform the same movements repeatedly and frequently. Such repetitive motion not only alters the sealing surfaces but also increases the axial movement of the device, gradually reducing the precision of the mechanical seal. Over time, the various components of the device will suffer damage or even deformation, thereby losing their ability to move in response to changes, which leads to seal leakage. What factors can affect the performance of mechanical seals? Firstly, the accumulation of slurry can hinder the action of the springs, cause the sliding components to lose control of their movement, and lead to wear on the surface of the sealing surfaces, all of which severely impact the performance of mechanical seals ； When the sliding seal surface suffers from wear, hardening, and aging, the shaft and sleeve can be damaged as a result, and the spring seat can also become worn or even bent. 4. Leakage caused by the combination of multiple factors. Sometimes, leakage occurs as a result of the combined effect of various factors, such as high friction, poor sliding, deformation of the sliding rings, and variations in flatness; these factors together can easily lead to leakage. Many of these reasons are caused by excessive fatigue, uneven stress, and damage to the liquid film. Therefore, proper installation and maintaining the cleanliness of the mechanical seal are extremely important; coupled with effective cooling, this helps to better eliminate potential problems. Training in the design of fine chemical plants, the layout planning of multi-functional workshops, and the design of process systems and utility systems; countermeasures for leaks and repairs. 1. Countermeasures for poor performance: First, use O-rings with good wear resistance and high rubber elasticity, as such rings can maintain their original shape and size even when slightly damaged, thus continuing to provide a seal. O-rings used for sealing are generally made of rubber or polytetrafluoroethylene. Polytetrafluoroethylene primarily has corrosion-resistant properties; it can be used as corrugated gaskets or in V-shaped tubes, among other applications. In high-temperature or low-temperature conditions, bellows made of materials such as stainless steel are generally chosen as sealing rings. If a rotary mechanical seal is required, O-rings are used as sealing rings for sliding sealing. We can consider using long-life stationary mechanical seals, where the stationary ring is mounted on the shaft side and the rotating ring is mounted on the casing side. This way, there will be no adverse effects on the device due to mechanical deformation; moreover, it also helps maintain good flatness of the structure. At the same time, with this installation method, the spring does not come into contact with the sealing fluid, which greatly improves its operational performance; it also provides significant convenience in tasks such as removing slurry and maintaining the flatness of the seal as well as the precision of the machine. Mechanical seals are also greatly affected by heat; heat can cause the materials to degrade and the components to deform, which in turn alters their load-bearing capacity. This significantly reduces the performance of the seal and increases the risk of it being damaged or burned out. The treatment method depends on the amount of heat involved; options include natural cooling, internal circulation cooling, external flushing cooling, and other such methods. Additionally, the temperature of the seal needs to be controlled in order to achieve the best sealing effect. 2. Countermeasures for the sliding surface: During equipment maintenance and inspection, carefully check for wear and scoring on the equipment to ensure the precision of the static ring surface. At the same time, the use of a stationary mechanical seal can effectively solve the problem of wear. Another method to address the thermal deformation of seals due to changes in stress in the materials of sliding components is to change the way in which the O-rings or graphite rings of the seal are held, from a sliding arrangement to an inserted one. 3. Measures to prevent dry sliding: If dry sliding occurs as a result of damage to the sliding surface due to insufficient cooling when heat is generated from sliding, we can opt for more advanced sealing fluids, cooling water, and temperature control units. Additionally, it is necessary to regularly inspect the supply pipelines to prevent blockages. When selecting a mechanical seal, it is advisable to use a stationary mechanical seal with good resistance to slurry, as this helps to prevent dry friction more effectively. In addition, it is very important to strengthen the operational management of rotating machinery by regularly checking various parameters and conditions such as the pressure of mechanical seals, and addressing any related issues promptly, in order to maintain the integrity of the machinery and its proper operation.