Subsea Gate Valve – PDC Material and Sand Slurry Test

Produced well flow is controlled through the valves placed in the Christmas tree. Often being a gate-type valve, they are responsible for isolating the well from the surface on purpose with a surface command and automatically in an emergency. The reliability of the valves is particularly essential for subsea wells, as maintenance and replacement involve significant cost, time, and HSE risks to the project. Their designs are intended to withstand harsh conditions for long periods, including high temperatures, pressure, flowing solid particles, and corrosive environments. However, it is not rare to experience failing subsea valves due to leakage, cold welding, erosion of sealing elements, and other mechanical problems. These issues were the primary driver of the initial stage of the research where it was experimentally concluded that replacing the current tungsten carbide (WC)-based coating with polycrystalline diamond compact (PDC) material results in friction and wear reduction as expected theoretically due to its low friction, high hardness and high thermal stability properties. Following the promising results, developing a prototype is the next phase, which needs to pass the required tests by American Petroleum Institute (API) standards, the slurry test being the most challenging. Therefore, in this research, a 3D model is created and simulated with relevant conditions (sand slurry) to investigate the erosion and wear rate on the sealing element and internal walls of a subsea gate valve. Ansys Fluent is used along with the Oka erosion model and a Discrete Phase Model (DPM) to simulate the interaction of sand particles with valve surfaces under realistic flow conditions. The findings contribute to the decision-making period by providing the expected flow characteristics and erosion-prone areas, and quantitative erosion estimates before manufacturing the prototype. To quantify the optimization due to the change of internal coating material, a comparative analysis is used on the case study that includes a 5-inch subsea gate valve exposing to upstream flow with 2% sand slurry (250-400 μm particle size). A finite element method is used to solve the simulation for WC and PDC materials separately. The results show that in the same conditions, having PDC material as a contact layer leads to a 77.6% reduction in erosion depth and, thereby, 4.5 times the extended lifetime of the subsea valve. This study is among the first to simulate erosion behavior of PDC-coated subsea valves under API slurry test conditions, contributing to both technology readiness advancement and literature on erosion-resistant valve coatings.