Slurry leakage from seals is relatively common during sand mill operation. It is often not caused solely by the quality of the seal itself, but by the combined effects of temperature, pressure, medium, and structure. When temperature control is lost, heat in the grinding chamber increases, slurry viscosity changes, the force on the seal faces becomes unbalanced, and thermal expansion of the seals changes the fit clearances. When cooling is insufficient, it is difficult to form a stable fluid film on the seal faces, leading to dry running, wear, and leakage. Therefore, dealing with slurry leakage should start from both temperature control and seal structure.
The causes can be divided into several categories. In terms of temperature and cooling, high cooling water temperature, insufficient flow, jacket scaling, and blocked internal rotor channels can all raise the temperature in the seal area. In terms of pressure and flow, feed pressure fluctuations, outlet blockage, and unstable pumping can cause pressure changes at the seal faces. In terms of medium and materials, high-solid, high-viscosity, and particle-containing slurries accelerate seal face wear; solvent-based systems may cause seals to swell. In terms of installation and wear, improper spring pressure, poor face parallelism, worn shaft sleeves, and aged O-rings can also cause leakage. In terms of operation and maintenance, frequent start-stop cycles, dry running, incomplete cleaning, and delayed replenishment of the barrier medium can also shorten seal life.
During maintenance, first shut down and release pressure, stop the feed, drain the slurry, and clean with a suitable cleaning fluid. Disassemble the seal chamber and inspect the seal faces, shaft sleeve, springs, O-rings, and cooling channels. If the faces are worn, scratched, or thermally deformed, they need to be replaced or lapped. Check whether the cooling water circuit is unobstructed and remove scale. Check whether the shaft is bent and whether the bearing clearance is excessive. When replacing seals, select them according to material compatibility. During installation, keep the faces clean, apply a suitable lubricant, tighten to the specified torque, and adjust the spring pressure. After assembly, first supply cooling water and run a no-load trial to observe temperature rise, vibration, and leakage. Then gradually introduce feed and check pressure and flow. If leakage persists, check shaft sleeve runout, seal chamber coaxiality, and pipeline pressure.
In terms of prevention, RUCCA adopts an internal and external dual cooling system to control temperature at the source and reduce a major cause of seal failure. The seal faces use wear-resistant, corrosion-resistant, and high-temperature-resistant cemented carbide combinations, combined with proper spring pressure and fluid film design, so that stable sealing can be maintained under frequent start-stop and variable operating conditions. The modular design enables faster replacement and reduces downtime losses. Daily monitoring should include cooling water temperature, flow, grinding chamber outlet temperature, and seal area temperature. Keep the feed stable and avoid dry grinding and idle running. Regularly inspect seals and the medium, and replace wear parts according to the cycle. For high-solid and particle-containing materials, an inline dispersion system can be used for pre-dispersion to reduce scouring of the seal faces by large particles.
If slurry leakage occurs repeatedly, record the operating parameters and combine them with disassembly results to determine whether the problem is caused by temperature, installation, or medium selection. It is recommended to send material samples for testing, and RUCCA engineers will recommend seal materials and cooling solutions based on the material characteristics. By observing temperature rise, leakage, and wear through laboratory or pilot tests before determining the production configuration, maintenance time after commissioning can be reduced.
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