Improper Operation of Slurry Pumps: Common Issues and Preventive Measures

Improper Operation of Slurry Pumps: Common Issues and Preventive Measures

As a critical piece of equipment in mechanical engineering, slurry pumps are widely used in mining, power plants, dredging, metallurgy, chemical processing, building materials, and petroleum industries. By utilizing centrifugal force generated by the rotation of the pump impeller, slurry pumps increase the energy of solid-liquid mixtures, converting electrical energy into kinetic and potential energy of the medium. However, improper operation can lead to numerous problems that not only affect normal pump operation but also result in significant economic losses.

1. Reverse Motor Rotation
One of the most common issues is reverse motor rotation. Reverse rotation can cause the impeller to loosen or even break. When the motor rotates in reverse, the impeller experiences an opposite torque, loosening or fracturing its connection to the shaft. Once the impeller becomes loose, the pump fails to rotate properly; in severe cases, the impeller and liner can shatter, causing substantial damage. To prevent this, the pump installation and operation manual explicitly states that the motor direction must be checked before operation. Only after confirming correct rotation should the coupling pin be inserted, followed by manual barring to ensure smooth rotation, and then pump startup. Nevertheless, due to negligence or lack of experience, operators often skip this step, leading to frequent reverse rotation incidents.

2. Failure to Add or Improper Addition of Circulation Water
For water-cooled slurry pumps, the mechanical seal requires circulation water to be turned on before starting the pump. Circulation water provides cooling and lubrication, preventing overheating and damage to the mechanical seal. Without proper circulation water, the seal rapidly wears out due to lack of lubrication and cooling, potentially causing leakage. For pumps using gland packing, special attention is also required: water must be turned on before starting the pump, and the water pressure must be higher than the pressure inside the pump chamber. Otherwise, backflow may occur, leading to water ingress and affecting normal operation. In practice, many operators overlook the importance of adding water or do so incorrectly, resulting in mechanical seal damage and increased maintenance costs.

3. Incorrect Valve Opening/Closing Sequence During Startup and Shutdown
Improper sequencing of valve operations during pump startup and shutdown can cause a range of problems. The correct startup sequence is as follows:

• Check that inlet and outlet valves are closed.

• Open the clean water inlet valve.

• Open the normal-pressure cooling water valve (for auxiliary impeller seals or mechanical seals) or the shaft seal water valve (check water pressure).

• After the pump runs steadily, open the slurry pump inlet valve.

• Close the clean water inlet gate valve.

• Finally, open the outlet valve.

The shutdown sequence is the reverse:

• Open the inlet clean water valve and close the inlet pipeline valve (flush for 2–5 minutes).

• Close the outlet valve.

• Stop the pump, then close the shaft seal water or normal-pressure cooling water.

• Finally, close the inlet clean water valve.

Due to lack of familiarity with proper procedures or simple negligence, operators often ignore the correct valve sequence, leading to abnormal vibration, noise, or even damage during startup and shutdown.

4. Clogging
Slurry pumps handle mixtures containing solid particles and water. If oversized particles or long fibrous materials enter the pump pit, they can clog the pump casing or impeller, preventing normal operation. To avoid this, the suction piping must have no leaks, and the screen bars at the pump pit must meet the pump’s allowable particle size requirements. In practice, inadequate control over particle size or infrequent cleaning leads to frequent clogging, increasing maintenance difficulty and cost.

5. Other Common Failures

• Excessive Bearing Temperature – Usually caused by poor bearing lubrication or insufficient cooling water. High temperatures accelerate bearing wear and reduce operational stability and service life. Regular inspection of bearing lubrication and cooling water supply is essential.

• Mechanical Seal Leakage – May result from worn sealing faces, loose seal rings, or excessive seal medium pressure. Severe leakage not only affects pump operation but may also cause environmental contamination. Regular inspection and timely replacement of worn seal components are necessary to ensure reliability.

Preventive Measures
To address and prevent the above issues, the following measures are recommended:

• Operator Training – Strengthen training and education to improve technical skills and safety awareness. Operators must be thoroughly familiar with slurry pump working principles, operating procedures, and maintenance methods.

• Regular Maintenance – Perform routine cleaning, inspection, and repair of slurry pumps. Timely replace worn components and seals to ensure reliable operation.

• Monitoring and Management – Install sensors and monitoring equipment to track real-time operating status and parameters. Detect and address anomalies promptly to avoid accidents.

Improper operation of slurry pumps can lead to motor reverse rotation, clogging, excessive bearing temperature, mechanical seal leakage, and other problems. These issues compromise pump performance and service life, increase maintenance costs, and introduce safety risks. By enhancing operator training, performing regular maintenance, and strengthening operational monitoring, these risks can be effectively mitigated, ensuring that slurry pumps play a greater and more reliable role in industrial production.