An Experimental Study on the Effect of Oil Viscosity and Wear-Ring Clearance on the Performance of an Industrial Centrifugal Pump

The clearance of wear-rings in the impeller of centrifugal pumps has an important influence on the pump’s performance. Unfortunately, this effect has not been quite well documented, especially for the centrifugal pumps handling viscous oils. An industrial centrifugal pump with low specific speed was employed as a model to investigate the effect of the clearance on the performance of the pump. In this experimental study, the clearances of the wear-rings on the impeller shroud and hub were enlarged; the performances of the pump were measured when it pumped water and the viscous oils. The performance curves, the hydraulic parameters, and their relative variation ratios at best efficiency points were examined carefully for different clearances at various viscosities. The results showed that the flow rate is varied relatively in a range of −6% − +5%, the head −10% − +6%, the shaft-power + 2% −+8% and the efficiency −19% − +2%, respectively, when the clearance was enlarged from 0.25 mm to 0.85 mm at best efficiency points. The clearance of wear-rings on shroud has a more significant influence on the performance than on the hub. However, such an effect is weakened with increasing viscosity.