Design and Construction of a High Pressure System for Evaluating Multiphase Twin-Screw Pumps

Twin-screw pumps are currently sold by manufacturers without adequate data predicting the pump behavior when pumping multiphase mixtures. In light of the fact that pump behavior is known to change significantly under these conditions, a new closed-loop test facility has been designed and constructed to allow for testing of twin-screw pumps at high gas volume fractions. With minimal modification, the test facility can accommodate high pressure flows and oil-based liquids for testing.

The closed-loop test facility supplies air and water to the inlet of an MR-200 twin-screw pump of which the performance characteristics are desired. The flow of air and water can be regulated to give the desired inlet pressure, outlet pressure, and gas volume fraction. The resulting mixture is driven to the test pump by its inlet suction. It then passes through the pump to a gravity separator, where it is separated into discrete liquid and gas phases. Inlet pressures up to seventy-five psig can be used, and with minimal modification, up to three-hundred psig. Total flow rates of up to six-hundred-fifty gallons per minute can be accommodated. A two-hundred horsepower electric motor provides the mechanical power for the pump.

The test facility includes instrumentation and data acquisition equipment to monitor the pressures and temperatures at various points in the flow loop, as well as the flow rate and motor voltage of the pump. The closed-loop facility is validated by comparing the volumetric efficiency, mechanical efficiency, and pump effectiveness results to a previous open-loop facility that was also used to test the same twin-screw pump. Suggestions are given to replace an air valve to allow for more precise control of the air supply and to add a pulsation dampener that will moderate pressure oscillations. High pressure piping and tubing must be added for testing at higher inlet pressures.