In industrial electric high-pressure centrifugal water pumps, the sealing structure plays a crucial role in preventing leakage when transporting liquids. These pumps are typically used under high-pressure conditions; if the seal fails, it will not only cause media leakage and energy waste, but may also lead to safety hazards or environmental pollution. Therefore, the design, selection, and maintenance of the sealing structure directly affect the reliability and service life of the pump.
The sealing structure of centrifugal water pumps is mainly divided into two categories: dynamic seals and static seals. Dynamic seals are used at the gaps between rotating and stationary parts, such as where the pump shaft passes through the pump casing; static seals are used at the connections of stationary parts, such as the connection between the pump body and end covers, flanges, etc. Under high-pressure conditions, the reliability of dynamic seals is particularly critical, as they must withstand the impact of high-pressure media and the rotational friction of the shaft. Even slight wear or installation deviations can lead to leakage. Common dynamic seal types include mechanical seals, packing seals, and floating ring seals. Among these, mechanical seals have become the mainstream choice for industrial electric high-pressure centrifugal water pumps due to their good sealing effect and long service life.
Mechanical seals achieve sealing through the contact between the end faces of the rotating and stationary rings, with the core principle being the balance of the liquid film between these end faces. Under high pressure, the medium pressure forces the rotating and stationary rings to adhere tightly, forming a very thin liquid film that prevents leakage and reduces end face wear. If the seal structure is poorly designed, such as with excessively high or low end face specific pressure, the liquid film will become unstable: excessive specific pressure will accelerate end face wear, while insufficient specific pressure will increase leakage. Furthermore, under high pressure, the medium temperature may rise. If the cooling system fails, the liquid film may vaporize, causing dry friction and further damaging the sealing end face. Therefore, mechanical seals require a flushing system to remove heat through circulating coolant and maintain a stable end face temperature.
While packing seals are simple in structure and low in cost, their application is limited under high pressure conditions. Their principle involves pressing flexible packing into the stuffing box using a gland, relying on the contact pressure between the packing and the shaft to prevent leakage. However, high-pressure media will exacerbate packing wear and extrusion, causing leakage to increase over time. To reduce leakage, frequent tightening of the gland is necessary, but this increases frictional power consumption and can even lead to shaft sleeve wear or packing burnout. Therefore, packing seals are mostly used in low-pressure, high-flow-rate applications or those requiring frequent flushing. Industrial electric high-pressure centrifugal water pumps typically only consider packing seals when the medium is highly corrosive and mechanical seals are unsuitable.
Floating ring seals achieve sealing through a combination of multiple floating rings and support rings. Each floating ring is supported by a spring and maintains a small gap with the shaft. When high-pressure media enters the gap between the floating ring and the shaft, a pressure drop is created, preventing further leakage. Its advantages are simple structure and reliable operation, but it has a relatively long axial length and requires the cavity to be kept full of liquid; otherwise, dry running may cause seal failure. Therefore, floating ring seals are more suitable for medium-to-high pressure, large-capacity water pumps, rather than high-pressure small water pumps.
The choice of materials for the sealing structure is equally important for leak prevention. Under high-pressure conditions, the sealing face must withstand high pressure, high temperature, and high-speed friction; therefore, the material must possess high hardness, wear resistance, and corrosion resistance. For example, the rotating ring is often made of hard alloy or ceramic materials, while the stationary ring uses self-lubricating materials such as graphite or silicon carbide to reduce end-face wear. In addition, auxiliary sealing elements such as O-rings and sealants must also be adapted to high-pressure environments to avoid leakage due to material aging or compression deformation.
Besides the sealing structure itself, installation and maintenance are also key factors affecting leakage prevention. When installing a mechanical seal, ensure the parallelism of the rotating and stationary ring end faces to avoid uneven wear; for packing seals, control the packing clamping force to prevent over-tightening or under-tightening. During operation, regularly check the sealing condition, such as monitoring leakage and temperature changes, and promptly identify and address any abnormalities. For example, if the leakage of a mechanical seal suddenly increases, it may be due to end-face wear or spring failure, requiring immediate shutdown and seal replacement; if the leakage of a packing seal increases, the gland can be tightened appropriately, but excessive tightening should be avoided to prevent damage to the shaft sleeve.
The sealing structure of an industrial electric high-pressure centrifugal water pump has a decisive influence on leakage prevention. By rationally selecting the sealing method, optimizing the structural design, using high-performance materials, and strictly controlling the quality of installation and maintenance, the reliability of the seal can be significantly improved, the risk of leakage can be reduced, and the water pump can be ensured to operate stably for a long time under high pressure conditions.
