Low pressure in centrifugal pumps is a common issue that can reduce efficiency, decrease flow, and even damage equipment. Understanding the root causes is essential for maintenance and system optimization. The reasons can generally be classified into pump-related, system-related, and operational/medium-related factors.

1. Pump-Related Causes

1. Impeller Wear or Damage

   • Worn or damaged impellers reduce the pump head, resulting in low pressure.

   • Solution: Inspect the impeller regularly and replace it if necessary.

2. Blocked Suction or Impeller

   • Debris or sediment in the pump can reduce suction flow and lower pressure.

   • Solution: Clean the pump and pipeline to ensure smooth fluid flow.

3. Bearing or Mechanical Seal Failure

   • Increased friction or leakage from seals consumes energy and decreases output pressure.

   • Solution: Check bearings and mechanical seals, and repair or replace as needed.

4. Incorrect Pump Selection

   • Using a pump with a designed head lower than the system requirement leads to insufficient pressure.

   • Solution: Recalculate system resistance and select a suitable pump.

2. System-Related Causes

1. Excessive Pipeline Resistance

   • Small pipe diameters, long pipelines, or excessive elbows increase resistance and reduce pump pressure.

   • Solution: Optimize pipeline design, increase diameter, or reduce elbows.

2. Partially Closed Valves

   • Partially closed valves restrict fluid flow, causing pressure drops.

   • Solution: Check valve positions and adjust according to design specifications.

3. Insufficient NPSH (Net Positive Suction Head)

   • Low liquid level, long suction pipes, or air leaks can cause cavitation and low pressure.

   • Solution: Raise the liquid level, shorten the suction line, and eliminate air leaks.

3. Operational and Medium-Related Causes

1. High Fluid Viscosity

   • High-viscosity fluids increase pump load, leading to lower pressure.

   • Solution: Use pumps designed for high-viscosity fluids or reduce fluid viscosity.

2. Low Pump Speed

   • Insufficient motor power or incorrect variable frequency settings reduce pump output.

   • Solution: Check the motor and drive system, ensuring the pump runs at the designed speed.

3. Cavitation or Dry Running

   • Insufficient suction liquid or high gas content causes cavitation or dry running, reducing pressure.

   • Solution: Maintain adequate suction fluid and remove gas from the system.

💡 Summary

The most common causes of low pressure in centrifugal pumps include impeller wear, excessive pipeline resistance, poor suction conditions, and incorrect pump selection.

Recommended Troubleshooting Order:

1. Inspect the pump itself (impeller, seal, bearings).

2. Check the system pipeline and valves.

3. Examine operational conditions and fluid characteristics.