Effect of Impeller Inlet Edge Thinning on Efficiency of 6/4D-AH Slurry Pump: CFD Simulation and Field Validation

Subtitle: Thinning the inlet edge by 2-4mm during impeller repair can increase efficiency by 1.5%-3%, but excessive thinning (>6mm) induces cavitation – optimal thinning amount and measured data

Introduction

The 6/4D-AH is a classic AH series slurry pump (150mm discharge, 100mm inlet), widely used in mill discharge, cyclone feed, and tailings transport. After prolonged operation, the impeller inlet edge often becomes blunt or develops notches due to cavitation or wear. During field repair, maintenance personnel typically grind the inlet edge to restore a streamlined profile. This seemingly simple operation significantly affects pump performance: moderate thinning reduces inlet shock losses and improves efficiency; excessive thinning reduces inlet area, increases velocity, induces cavitation, reduces efficiency, and shortens life.

Hebei Xingou Machinery Equipment Co., Ltd. has quantified the effects of different thinning amounts on 6/4D-AH impeller efficiency, head, and NPSHr through CFD simulation and field testing. This article presents simulation data, the optimal thinning range (2-4mm), and repair guidelines.

1. Purpose and Risks of Inlet Edge Thinning

1.1 Why Thin the Inlet Edge?

1.2 Risks of Excessive Thinning

2. CFD Simulation Setup

2.1 Model and Conditions

2.2 Thinning Scenarios

Thinning was applied to the pressure side of the inlet edge. Five scenarios were compared:

3. Simulation Results

3.1 Efficiency Change

Conclusions:

• Moderate thinning (2-4 mm) improves efficiency by 0.8%-1.6%.

• Optimal thinning is 4 mm, giving the highest efficiency gain (+1.6%).

• Thinning beyond 6 mm reduces efficiency and significantly increases NPSHr (cavitation risk).

3.2 Flow Field Analysis

4. Field Validation Case

Background: A 6/4D-AH pump at an iron ore concentrator had an impeller with notches on the inlet edge due to cavitation. Hebei Xingou Machinery recommended thinning the inlet edge to 4mm during repair, and performance was tested before and after.

Field test data (same duty: flow 180 m³/h, speed 1450 rpm):

Conclusion: Thinning by 4mm improved efficiency by 2.3 percentage points, reduced current by 6.6%, and caused no cavitation. Results align with CFD trends.

5. Thinning Procedure

5.1 Tools

5.2 Steps

5.3 Precautions

6. Summary of Thinning Effects

Conclusion

Thinning the impeller inlet edge during repair of a 6/4D-AH slurry pump can improve efficiency. CFD simulation and field validation show that thinning by 2-4 mm increases efficiency by 0.8%-1.6%, with 4 mm being optimal. Thinning beyond 6 mm reduces efficiency and significantly increases cavitation risk. Repair should follow proper procedures, maintain symmetry, and include static balancing. Hebei Xingou Machinery Equipment Co., Ltd. offers impeller repair guidance and CFD support. Please contact us.