Pressure balancing proppant addition method and apparatus

Abstract

A method for controlling the flow of proppant into frac fluid during a frac. A first pressure source pressurizes fluid within a proppant addition unit. Process piping receives proppant through a proppant supply passage for supply to a frac pressure pump. A second pressure source pressurizes fluid within the process piping. A first sensor senses pressure on a first side of the proppant supply passage and outputs a first signal. A second sensor senses pressure on the process piping on a second side of the proppant supply passage and outputs a second signal. A processor receives the first signal and the second signal, and outputs a control signal to at least one of the first pressure source and the second pressure source in response to the first signal and the second signal to control proppant flow into the process piping.