# Investigation of the Fluid Flow in a Large Ball Valve Designed for Natural Gas Pipelines
###### Abstract
By optimization using an orthogonal array, the response surface method and trade-off method demonstrated that the weight could be reduced by up to 16.67% (from 2.34 to 1.95 kg) for the studied balls, which had radii of 37/35/33 mm. The results highlight that when using ASTM A296 CF8M as the construction material, the ball valve was more resistant to corrosion and provided higher strength at different temperatures, compared to balls made from CF8 [14]. The particle tracking flow visualization (PTFV) method can also be used to determine flow characteristics and flow patterns. [PERSON] et al. performed an experimental study on a DN50 ball valve to observe the flow patterns for different opening angles and cavity phenomena [15]. The study concluded that such a method represents an effective way to determine the performance coefficients of a valve and to understand how and when cavitation can occur. [PERSON], [PERSON] et al. studied the evolution of flow characteristics for different openings using FLUENT. They observed how a DN50 ball valve opening or closing within different time intervals developed different fluid flow patterns. If the opening/closing period is long, the flow rate, the inlet and outlet pressure, the pressure drop, and the flow resistance are similar to the steady condition. These results can offer support for increasing the dynamic performance during the opening and closing process [16]. [PERSON], [PERSON] et al. conducted a comparative analysis on two types of metallic seats for ball valves: one with the multi-asperity model and one with the magnification-based model. The scope was to study leakage simulation for a ball valve, using water as the working fluid. Simulations performed by ANSYS and experiments on a ball with a radius of 20 mm were performed. The best simulation results were obtained for the magnification model, which was the one that provided the best match to the experimental results [17]. The works [12; 13; 14; 15; 16; 17] focus on new valves. Some researchers were more interested in the phenomena that occur in the components of old pipelines. For instance, [PERSON], [PERSON] et al. studied the failure pressure in aged pipelines using the finite element method, considering the changes in mechanical characteristics following a long working period. Their results demonstrated that corrosion defects and aging have an impact on the failure pressure [18]. In contrast to previously presented works that focused on ball valves of up to 125 mm in diameter, the present study focuses on CFD simulation of the fluid flow in a large ball valve. A trunnon ball valve with a diameter of 500 mm, with metal-metal (MM) sealing and double-piston effect (DPE) seats, is the type of valve analyzed in the present work. This paper aims to contribute to the research field by studying the behavior during the closing process of a sealing technology recommended for ball valves with components, materials, and technologies selected to answer to the challenges of natural gas transportation within the large-diameter domain. The investigated valve was designed according to the standard API 6D [19] and the corresponding European standard SR EN ISO 14313 [20], which are the standards that specify requirements and provides recommendations for the design, manufacturing, testing, and documentation of ball, check, gate, and plug valves for application in pipeline systems meeting the requirements for the petroleum and natural gas industries. The simulation was performed using SolidWorks Fluid Flow 2023 software. The main originality of this paper consists in the simulation of a large-diameter ball valve working at a high class of pressure (Class 400), as well as providing explanations about why MM sealing with a DPE design for seats is appropriate to obtain high valve safety by limiting leakages. To the best of our knowledge, this topic has not been the focus of other works. Ball valves are shut-off valves, designed to work at 0\({}^{\circ}\) and 90\({}^{\circ}\) opening positions.