In self-priming spiral water pumps, the effectiveness of the sealing design directly affects their stable operation and leakage prevention during the self-priming process. These pumps typically employ a combination of spiral seals and mechanical seals, using a multi-stage sealing structure to create layers of protection, ensuring consistent sealing performance even in complex conditions involving gas-liquid mixing during the self-priming phase. The spiral seal, as a non-contact dynamic seal, works by utilizing the pumping effect of the spiral grooves to generate reverse pressure, counteracting the leakage tendency of the sealed medium (such as water or a gas-liquid mixture). When the pump starts, the impeller rotates at high speed, creating negative pressure. Gas and liquid mix in the suction line and enter the pump chamber. At this time, the spiral grooves of the spiral seal push the potentially leaking medium back through rotation, achieving dynamic equilibrium. This design is particularly suitable for the gas-liquid mixing state during self-priming, effectively reducing the risk of leakage.
The mechanical seal, as a supplement to the contact seal, achieves zero leakage through the tight fit between the dynamic and stationary rings. In self-priming spiral water pumps, the mechanical seal is usually installed at the rear end of the spiral seal, providing double protection. Its working principle relies on the preload of elastic elements (such as springs) to maintain contact between the rotating and stationary ring end faces, achieving lubrication and sealing through a liquid film between the end faces. During self-priming, if the spiral seal's sealing capacity decreases due to fluctuations in operating conditions (such as an excessively high gas ratio), the mechanical seal immediately assumes the primary sealing task to prevent media leakage. Furthermore, the material selection for the mechanical seal must be compatible with the transported medium; for example, wear-resistant materials such as silicon carbide or ceramics should be used to withstand wear from impurities that may occur during self-priming.
Another key aspect of the seal design is the precision of the fit between the rotating and stationary components. The clearance between the rotor and stator of the spiral seal must be strictly controlled. An excessively large clearance will reduce the sealing effect, while an excessively small clearance may lead to frictional wear due to thermal expansion or eccentricity. In practical designs, this is often achieved by elastically mounting the rotor or using a floating seal structure, allowing the rotor to automatically align during operation and reducing the impact of eccentricity. Simultaneously, the flatness of the rotating and stationary ring end faces of the mechanical seal must reach the micron level to ensure the formation of a stable liquid film even under high-speed rotation, avoiding leakage caused by dry friction.
The gas-liquid separation efficiency during self-priming directly affects sealing performance. If the gas-liquid mixture is not fully separated, gas may enter the sealing area, disrupting liquid film stability and leading to leakage. Therefore, self-priming spiral water pumps are typically equipped with an independent gas-liquid separation chamber. By increasing the volume and reducing the flow velocity, the gas and liquid naturally separate due to their density difference. The separated liquid flows back to the impeller inlet to re-enter the circulation, while the gas is discharged from the pump through the exhaust pipe. This design not only improves self-priming efficiency but also reduces gas interference in the sealing area, indirectly enhancing sealing reliability.
The corrosion resistance and temperature resistance of the sealing material are equally important. During self-priming, the medium may generate localized high temperatures due to high-speed shearing or friction, accelerating the aging of the sealing material. Therefore, the spiral groove surface of the spiral seal is often hardened (e.g., chrome plating or ceramic coating), and the auxiliary sealing ring of the mechanical seal uses high-temperature and corrosion-resistant materials such as fluororubber or polytetrafluoroethylene to adapt to the transportation requirements of different media.
Maintenance and monitoring are crucial for ensuring the long-term effectiveness of the seal. Regularly inspecting sealing gaps, replacing worn parts, and cleaning deposits in the gas-liquid separation chamber can significantly extend seal life. Furthermore, some high-end models are equipped with leak monitoring sensors that provide real-time feedback on the sealing status, facilitating timely maintenance and preventing equipment failure due to escalating leaks.
The self-priming spiral water pump utilizes a multi-layered, highly reliable sealing system through the synergistic effect of spiral and mechanical seals, high-precision dynamic and static fit, efficient gas-liquid separation design, and the application of corrosion-resistant materials. This design not only meets the sealing requirements of complex operating conditions during self-priming but also reduces maintenance difficulty through a modular structure, providing a solid guarantee for the stable operation of the pump.
