Investigating effects of ball size on the performance of gas lift valve for both modified and optimized seats

Abstract

The seat and the ball are the only two components of a Gas Lift Valve (GLV) that can be switched out to meet changing gas throughput requirements. For this reason, individual pairings of balls and seats must be designed to meet the particular requirements of specific situations. While conventional GLV seats have sharp edges, a modified seat design with partially beveled edges has been shown to improve gas throughput. This design was then tested using benchmark valve and was optimized by beveling the entire port of the seat. These experiments were conducted using a ball diameter that was 0.0016 m larger than the diameter of the port top, although the effects of even larger ball sizes have also been studied using benchmark valves with conventional seats. Researchers have yet to explore the effects of ball diameters smaller than the Port Top Diameter (PTD) and larger than the Port Bottom Diameter (PBD) for modified and optimized seat designs. In this paper, the effects of smaller ball size on the GLV gas throughput have been analyzed using both modified and optimized seat designs and actual GLV. The ball was 0.0016 m smaller than the PTD of the seats. Geometric models have been deduced to calculate the generated upstream area (frustum area) open to flow. This frustum area is a function of stem travel, and the dimensions of the seat and ball. Theoretical calculations have been compared with results obtained through robust experimental methods. The entire experimental program was divided into four individual experiments. The static testing was used to fix the dome pressure and the opening pressure. The hysteresis effect associated with the bellows assembly was minimized using the aging procedure. Probe tester was used to measure the stem travel. Finally, the gas throughput of the GLV was measured using dynamic testing. The smaller ball sizes were found to significantly improve the gas throughput of actual GLV. This improvement was as high as 179% for large PBD seats. However, the frustum area practically decreased for these cases. This result suggests that the flow coefficient has more effect on GLV gas throughput compared to frustum area.