Performance of Multiphase Twin-Screw Pump During the Period of Wet-Gas Compression

Summary Sealflush recirculation in twin-screw pumps is an important function because it serves the purpose of not only cooling the seal faces but also sealing the gas leakage from one cavity to another during the period of wet gas compression, which directly affects the pump performance. This study focuses on evaluating the effect of heat generation during the period of wet gas compression on the pump performance and potential mitigation measures to consequential issues for fixed flow rate of sealflush-fluid recirculation. A new design of twin-screw pump skid with an inbuilt closed-loop sealflush-circulation loop was tested for 150-, 200-, and 250-psi pressure differentials at 10-psi suction pressure. A sealflush flow of approximately 6% was maintained at an operating speed of 3,600 rev/min with 100% gas at the pump inlet. Pump performance was observed as the temperature rose from approximately 95°F to 180°F. Heat generation caused by gas compression significantly reduced the pump volumetric efficiency. Pump performance was characterized as a function of exhaust temperature for given pressure differentials. Effect of sealflush-fluid viscosity was investigated. Volumetric efficiency was found to decrease slightly with an increase in sealflush-fluid viscosity. Sealflush fluid was quenched to evaluate the effect of cooling. Cooling the sealflush fluid significantly affected the pump performance, reinstating the efficiency to near its optimal value.