Design Considerations And Application Guidelines For Pumping Liquids With Entrained Gas Using Open Impeller Centrifugal Pumps

Abstract

The proper selection of a centrifugal pump for liquid and gas (two phase) mixtures, is highly dependent on the amount of gas and the characteristics of the mixture. The presence of entrained gases will reduce the output of centrifugal pumps and can potentially cause loss of prime. Conventional pump designs can be used for low percentages by volume (up to four percent), while special impeller modifications are used effectively to handle five percent to 10 perfect gas by volume, although performance corrections are required for proper pump selection. Pump performance test data is presented for low to medium specific speed pumps (900 to 3000 U.S. units), pumping water with up to 10 percent entrained air. The results are shown for conventional pumps and those modified for air handling. Also discussed are the effects of suction pressure and impeller vane number. The effectiveness of inducers, vortex pumps, and special pump designs for gas extraction for up to 40 percent gas by volume are discussed. Application guidelines are presented for the proper selection of centrifugal pumps, which consider the percentage of gas volume, the pump size, system operation, impeller trim, and suction head.