In high-speed centrifugal impellers, the choice of sealing type directly affects media leakage control, equipment efficiency, and operational stability. Due to the combined effect of centrifugal force generated by the high-speed rotation of the impeller and the media pressure difference, the sealing structure must balance dynamic sealing performance and wear resistance, while adapting to complex operating conditions such as high temperature, high pressure, or corrosive media. Common sealing types include mechanical seals, labyrinth seals, floating ring seals, centrifugal seals, and combined seals. Each type achieves leakage prevention through different principles, and its applicability depends on the impeller speed, media characteristics, and equipment design requirements.
Mechanical seals are one of the most commonly used sealing types in high-speed centrifugal impellers. They achieve sealing through the end-face friction between a rotating ring and a stationary ring. The rotating ring rotates with the impeller shaft, while the stationary ring is fixed to the pump body. Lubricating fluid or sealing media is injected between the two rings to reduce wear. The advantages of mechanical seals are stable sealing performance and low leakage, making them particularly suitable for high-speed, high-temperature, and corrosive media environments. For example, in chemical process pumps, mechanical seals can effectively prevent the leakage of toxic or flammable media, ensuring production safety. The design of labyrinth seals requires consideration of material pairing, spring pressure, and cooling systems to ensure long-term reliability.
Labyrinth seals utilize energy dissipation in a tortuous channel to achieve sealing. They employ a series of radial or axial grooves in the impeller cover or pump body, causing the leaking medium to experience multiple throttling and diffusion processes, reducing its pressure and ultimately trapping it within the sealing cavity. Labyrinth seals eliminate the need for contact friction, resulting in low wear, long service life, and the ability to withstand high temperatures and pressures. In high-speed centrifugal compressors, labyrinth seals are commonly used for interstage sealing and impeller cover sealing to prevent backflow or interstage leakage. Their design requires optimization of tooth profile, clearance, and channel length to balance sealing effectiveness and pressure drop.
Floating ring seals are a type of dynamic oil film seal suitable for high-speed, high-pressure conditions. They consist of a floating ring mounted on the shaft, forming a thin oil film between the ring and the shaft, providing both lubrication and sealing. As the floating ring rotates with the shaft, the hydrodynamic effect of the oil film causes it to automatically align, forming a stable sealing surface. Floating ring seals offer advantages such as excellent sealing performance, adaptability to minor shaft vibrations or thermal expansion, and minimal maintenance. In high-pressure centrifugal pumps used in the petrochemical industry, floating ring seals are commonly used for shaft end sealing to prevent flammable gas leakage. Their design requires strict control of oil film thickness and temperature to avoid dry friction or oil film rupture.
Centrifugal seals, on the other hand, utilize the centrifugal force generated by impeller rotation to directly block leakage. This is achieved by installing an oil slinger or back vanes on the shaft, causing leaking liquid to be thrown against the sealing cavity wall under centrifugal force and returned to the pump through a return hole. Centrifugal seals have a simple structure, no contact wear, and can seal media containing solid impurities, making them suitable for high-speed hydraulic machinery such as slurry pumps. However, they are only suitable for low-pressure or near-zero pressure differential applications and require supplementary shutdown seals to prevent leakage during shutdown. In high-speed centrifugal pumps, centrifugal seals are often used as an auxiliary sealing method in combination with other sealing types.
Combined seals combine two or more sealing types to leverage their respective advantages and improve overall sealing performance. For example, a combination of mechanical seals and labyrinth seals can simultaneously achieve low leakage and high wear resistance; a combination of floating ring seals and centrifugal seals can handle both high-pressure sealing and solid-containing media. The design of combined seals needs to be customized according to specific operating conditions. For instance, in high-speed centrifugal pumps, a structure with a mechanical seal as the main seal and a labyrinth seal as the auxiliary seal can be used to cope with the challenges of high temperature, high pressure, and corrosive media.
The selection of the sealing type for high-speed centrifugal impellers requires comprehensive consideration of speed, media characteristics, pressure rating, and operating environment. Mechanical seals are suitable for most high-speed, high-temperature, and corrosive operating conditions; labyrinth seals and floating ring seals are more suitable for high-pressure or low-maintenance scenarios; centrifugal seals and combined seals provide flexible solutions for specific needs. By optimizing the seal design, the operating efficiency and reliability of high-speed centrifugal impellers can be significantly improved, extending equipment life.
