The R-ratio is considered a constant, equal to the area of the port (Ap) divided by the bellows effective area. When gas lift valves are tested for both opening and closing pressures, it is possible to calculate the R-ratio. The calculated R-ratio from test data is consistently larger than the manufacturers’ published R-ratios. This paper presents a discussion of the factors affecting the R-ratio and an explanation for the difference between published and tested R-ratios. The R-ratio is not a constant but varies with dome pressure, port-material strength, bellows size, and port size. A method is proposed to calculate or test the true R-ratio.
The use of the area of the port (Ap) in the R-ratio is not completely accurate. The area should be the seal area (As) defined by the outer-sealing diameter of the ball (Ds) on the port. It is possible to test valve behavior to determine the seal area, and it is recommended that the tests be conducted in order to use the correct R-ratio when designing gas lift wells. A method to apply the use of the measured R-ratio is also provided.