The MD type wear-resistant multistage centrifugal pump for coal mines is independently developed by Changsha Zoomlian Pump Industry. It possesses MA (Coal Mine Safety) and KA (Mine Safety) certifications and is generally equipped with explosion-proof motors.
Changsha Zoomlian Pump Industry has 30 years of experience in the continuous innovation and upgrading of MD type wear-resistant multistage centrifugal pumps for coal mines. Its customer applications cover numerous steel plants, mine drainage, wastewater transportation, and other scenarios.
Adopting a high-efficiency and energy-saving hydraulic model, the MD type pump is designed to transport neutral mine water and similar wastewater media with solid particle content ≤15%, particle size ≤0.5 mm, and temperature ≤80 °C.
The pump components feature a high-quality balance disc-ring system to balance axial forces. This system offers excellent wear resistance, requiring no replacement under normal operation for 5,000 hours. The service life of the pump body is ≥10 years, and the normal service life of rotor components such as the impeller is ≥5,000 hours.
Working Principle of the Return Pipe (Balance Pipe) of the MD Type Wear-Resistant Multistage Centrifugal Pump for Coal Mines
The medium liquid discharged from the last-stage impeller of the MD pump carries a certain pressure. It flows into the balance disc cavity through the radial clearance between the balance ring and the balance disc, putting the cavity under high pressure.
The balance disc is connected to the pump inlet via the balance pipe, where the pressure approximates the pump inlet pressure. This pressure difference across the balance disc generates a backward axial thrust — the balancing force of the pump. Acting opposite to the pump’s axial force, it automatically balances the axial thrust of the impeller.
When the axial thrust of the impeller exceeds the balancing force of the balance disc, the pump rotor moves toward the pump inlet. Due to inertia, this movement does not stop immediately at the equilibrium position but exceeds the limit, rapidly and excessively reducing the axial clearance of the balance disc. As a result, pump leakage decreases, the pressure in the front cavity of the balance disc rises, and the balancing force increases beyond the impeller’s axial thrust, pulling the rotor back toward the outlet side.
This inertial process enlarges the axial clearance again, causing the balancing force to drop below the axial thrust and the rotor to shift toward the inlet side. The cycle repeats continuously.
The above process is fully mechanical and automatic. During normal operation, the pump rotor repeatedly moves axially within a tiny equilibrium position. The axial movement is so slight that it is barely visible from the exterior of the pump.
Main Functions of the Return Pipe (Balance Pipe) of the MD Type Wear-Resistant Multistage Centrifugal Pump for Coal Mines