Technical Diagnosis and Solutions for Abnormal Speed ​​Fluctuations in Mining Multistage Pumps

As a core component of mine drainage and conveying systems, the speed stability of multistage pumps directly affects the pump set's operating efficiency and the continuity of mine production. Based on years of experience in mining pump R&D, HNYB PUMPS analyzes the causes of speed instability and proposes technical solutions from four dimensions: electrical, mechanical, fluid control, and system management.

• Common Fault Causes and Technical Analysis

1. Power Supply System Fluctuations: Underground power supply networks in mines are prone to voltage drops or harmonic interference due to sudden load changes and cable aging. Actual measurements show that a voltage deviation of ±5% can cause motor speed fluctuations exceeding 3%, and long-term fluctuations accelerate motor insulation aging.
2. Transmission System Defects: In belt drives, differences in V-belt pulley diameters and uneven belt tension can cause periodic speed jumps; misalignment of the coupling (radial deviation > 0.1 mm/m) will generate additional torque, leading to unstable pump shaft speed.
3. Fluid Dynamics Interference: Sudden changes in valve opening, pipeline cavitation, or excessive solids content in the medium (>8%) can cause pump impeller imbalance. Actual measurements show that a 15% flow rate fluctuation can cause speed deviations of ±20 rpm.
4. Control system failure: PLC program logic errors and improper inverter parameter settings (such as PID adjustment coefficient Kp/Ki/Kd mismatch) can cause speed closed-loop control failure, which is particularly prominent in constant pressure water supply systems.

• Technical Solutions

1. Electrical System Optimization Intelligent Voltage Stabilizer: Utilizing a customized isolation transformer and active filter combination from Changsha Zhonglian Pump Industry, it can filter out 50Hz/60Hz grid harmonics, keeping voltage fluctuations within ±1%. Practical testing shows it is suitable for underground 660V/1140V power supply systems. Redundant Power Supply Design: Key pump units are equipped with dual-circuit power supply switching devices, with a switching time <50ms, ensuring uninterrupted speed switching during dual power supply transitions in the mine.
2. Mechanical Transmission Upgrade Synchronous Belt Drive System: Adopting imported polyurethane synchronous belts (elongation <0.5%), combined with precise pulley tooth machining (tooth error <0.02mm), achieving speed fluctuations <±1rpm. High-Precision Couplings: Laser alignment calibration is completed before shipment (accuracy up to 0.01mm/m), and an ISO10820 standard certification report is provided.
3. Fluid Control Optimization: Dynamic Flow Balancing Valve: A V-cone flow meter and intelligent valve assembly independently developed by Changsha Zhonglian Pump Industry are installed at the pump inlet. The valve opening is adjusted in real time by PLC to achieve flow fluctuation < ±3%. Gas-Liquid Separation Device: For high-gas-content mines, a cyclone gas-liquid separator is adopted with a separation efficiency > 95%, avoiding sudden speed drops caused by cavitation.
4. Intelligent Monitoring System: Multi-parameter Sensors: Integrated vibration (range 0-100mm/s), temperature (-20℃~150℃), and speed (0-3000rpm) monitoring modules are used. The data sampling frequency is 1kHz, and the data is connected to the mine's SCADA system via a 4-20mA signal. Remote Diagnostic Platform: The Changsha Zhonglian Pump Industry cloud diagnostic system is deployed, supporting AI algorithm predictive maintenance and providing early warning of abnormal speed trends up to 72 hours in advance.
5. Standardized operation and maintenance Three-level maintenance system: daily inspection, weekly inspection (bearing clearance <0.2mm), monthly inspection (impeller dynamic balance test), and key components are provided with a 12-month warranty commitment.

• Preventive measures: Avoid unstable speed problems at the source

1. Strengthen Power Supply System Management

Use dedicated power lines to avoid sharing lines with high-power equipment and reduce voltage fluctuation interference.

Regularly test power grid quality, conducting voltage, frequency, and harmonic tests quarterly, and promptly address any potential issues.

2. Standardize Fluid and Pipeline Management

Optimize fluid pretreatment processes, reducing solids content through filtration and sedimentation to ensure viscosity, temperature, and other parameters meet pump design requirements.

Regularly clean pipelines, check valves and check valves to prevent blockages or leaks that could cause sudden load changes.

3. Implement Regular Maintenance

Establish maintenance cycles according to the pump's instruction manual: check bearing lubrication monthly, perform impeller cleaning and dynamic balancing every six months, and conduct a comprehensive disassembly and overhaul annually.

Establish an inventory of vulnerable parts (such as bearings, seals, and impellers), replacing aging components promptly to avoid operating with defects.

4. Scientific Selection and Installation

Select a suitable self-balancing multistage centrifugal pump based on actual operating conditions (flow rate, head, fluid characteristics) to avoid over-engineering or operation beyond the design range; during installation, strictly control the alignment accuracy of the coupling and the flatness of the foundation to ensure stress-free pipeline connections and reduce operational imbalances caused by installation errors.

Unstable speed of multistage centrifugal pumps in mining is not uncontrollable. The key lies in accurately identifying the cause, promptly investigating and addressing it, and mitigating risks at the source through scientific preventative measures. By standardizing power supply management, optimizing operating conditions, strengthening mechanical maintenance, and implementing precise control systems, we can ensure stable pump operation, maximize its energy-saving advantages, and reduce production and maintenance costs.