Calculation of Erosional Velocity Due to Liquid Droplets with Application to Oil and Gas Industry Production

Abstract

Abstract The American Petroleum Institute Recommended Practice 14E (API RP 14E) describes a method for calculating an "erosional" velocity, a threshold velocity at which it is presumably safe to operate. The origin of this guideline appears to remain a mystery, but some authors and operators assume that the basis for API RP 14E is erosion due to liquid droplet impacts. However, there is no experimental evidence supporting this idea. In this work, a method has been developed to calculate erosion resulting from liquid impact for pipeline materials that are used in oil and gas industry applications. Material loss data has been collected for several oil field materials such as stainless and carbon steels, chromium alloys, inconel and duplex utilizing specimens that were mounted on a rotating flywheel and impacting liquid jets. The data and American Society for Testing and Materials (ASTM) G73 guideline are combined to develop a method for calculating erosion resulting from liquid droplets impacting the surface of the pipe materials under specific flow conditions. The results from this model have been compared to data provided in the literature for both liquid jets and droplets impacting specimens utilizing different materials, droplet sizes or jet diameters and velocities. Although the model was developed based on data at relatively low velocity conditions, the results agree well with data for a variety of flow speeds and conditions. Furthermore, the model for liquid impact erosion is used to predict threshold velocities for specific flow conditions for elbow geometry to avoid erosion-corrosion due to liquid impacts. Moreover, the results of this model are compared for several different flow conditions with API RP 14E. It is shown that the trend of the erosional velocity calculated by the API guideline does not correlate with the erosional velocity calculated by the present method that is based on the liquid droplet erosion model. The model presented in this work will be improved as more data and information becomes available. An example is provided in which Computational Fluid Dynamics simulations are being used for different droplet and impinging jet diameters to improve the performance of the model.