How Internal Clearance Expansion Affects Backflow in Screw Pumps | Shanghai Cheng Pump Valve

 How Internal Clearance Expansion Affects Backflow in Screw Pumps | Shanghai Cheng Pump Valve

In industrial conveying systems, screw pumps are widely used for transporting high-viscosity media, sludge, oils, chemical liquids, and other complex fluids. Their stable flow and smooth operation make them common equipment in many factories. However, after long-term operation, some users notice that although the motor still runs normally, the pump flow rate and pressure gradually decrease. In many cases, the real reason is not motor failure, but the expansion of internal clearances inside the screw pump.

As the rotor and stator continue operating under friction, wear gradually increases the internal gap between components. Once the clearance becomes larger than the designed tolerance, part of the conveyed medium begins flowing backward inside the pump chamber. This phenomenon is known as internal backflow.

The increase of internal backflow directly reduces the actual output flow of the screw pump. Even if the pump speed remains unchanged, part of the liquid circulates internally instead of being discharged efficiently. At the same time, discharge pressure becomes unstable, energy consumption rises, and overall conveying efficiency decreases.

This issue is especially obvious when transporting abrasive or particle-containing media. Fine particles accelerate wear on the rotor and stator surfaces, causing clearance expansion to happen much faster. In some industrial applications, improper dry running or insufficient lubrication can also speed up internal wear.

Signs of excessive internal clearance usually appear before serious failure occurs:

• Reduced outlet pressure

• Flow instability

• Increased vibration or noise

• Higher motor load

• Reduced volumetric efficiency

To maintain stable performance, regular inspection of rotor and stator wear conditions is very important. Replacing worn components in time can effectively reduce internal backflow and extend pump service life.

As a manufacturer focusing on industrial fluid conveying equipment, Shanghai Cheng Pump Valve provides various screw pump solutions for chemical, environmental protection, food processing, wastewater treatment, and industrial conveying systems. More technical information about screw pump operation and maintenance can be found here:

https://www.scpv.cn/news/874.html

Choosing the correct operating conditions and performing routine maintenance are key factors in maintaining long-term stable screw pump performance.