Optimization of shaft-seal water system of cutter suction dredger based on high-efficiency centrifugal separation technology

Abstract The shaft-seal water system (SSWS), as one of the critical systems for slurry pump protection, is widely used to provide shaft-seal water in cutter suction dredger. In general, the shaft-seal water obtained from gravity clarifier always accompanies with numerous sand with large size (>10 μm), resulting in the inevitable intense wear of components in the slurry pump, especially, the shaft sleeve and L-shaped rubber ring in back shaft seal. Even worse, the high temperature caused by unstable shaft rotation in the present of sand will aggravate the degree of this wear. To address the above thorny problems, in this study, water-sealed hydrocyclone (WSH) was unprecedentedly applied to optimize SSWS for high-efficiency sand centrifugal separation. The dimension and structure of WSH were designed and optimized before final industrial application. High-efficiency separation zone (the separation efficiency >90%) with Re ranged of 1.88 × 104–2.23 × 104 was also confirmed by introducing the optimal structure of the WSH (5° of cone angle and 10 mm of bottom apex diameter). For the improved SSWS in the actual application, the Dv(50) of the shaft-seal water decreased from 38.0 μm to 9.1 μm, and the corresponding solid concentration declined from 0.51 g/L to 0.051 g/L. Furthermore, it was verified that the optimized SSWS could significantly reduce the wear of the shaft sleeve and L-shaped rubber ring, and extend the service life of L-shaped rubber ring, up to 4 months. This finding provided a new insight for the optimization of the SSWS for slurry pump, which could improve the operational stability and reliability of cutter suction dredger in the construction of marine infrastructure.