Research on structural optimization of shaft seals for filter press feed pumps in coal preparation plants

To address the issues of frequent failure, short service life, and poor sealing performance of shaft seal structures in filter press feed pumps of coal preparation plants, this study systematically analyzes the operating characteristics of feed pumps and the failure mechanisms of the combined structure of double-face mechanical seals and expeller dynamic seals. Based on an analysis of actual shaft seal leakage cases, a systemic optimization scheme is proposed: the compression springs are converted from a stationary type to a rotating type with additional fixing pins; the spatial structure of the rotating and stationary ring friction pairs is optimized; the number of compression springs is increased to 12; and based on the Finnie erosion model, the expeller diameter is appropriately reduced while an auxiliary flushing system is integrated. The results indicate that the sealing reliability and operational stability of the filter press feed pumps have been significantly enhanced. Post-optimization, the service life of key wear-prone components has increased to more than 2.5 times their original duration. Specifically, the service life of the mechanical seal has been extended from 90～180 days to over one year, and the lifespan of the expeller and seal box has increased from 60 days to over 150 days. This optimization scheme effectively solves the core problem of shaft seal failure under complex coal preparation conditions and provides a technical reference for the selection and improvement of shaft seals for filter press feed pumps.