# Investigation of the Fluid Flow in a Large Ball Valve Designed for Natural Gas Pipelines
###### Abstract  
Natural gas pipeline networks used for long-distance transportation are expanding quickly, and the construction of special valves with large diameters has especially increased since 2022. The design and manufacturing of the flow control equipment is carried out on a case-by-case basis, in accordance with the parameters required by the beneficiary. In this paper, results obtained by fluid flow simulation with SolidWorks2023 software for a 500 mm diameter trunion ball valve lead to important information regarding how the fluid flow develops in the intermediary and fully closed positions. The large inner space of the ball allows the development of high-amplitude vortices; thus, the simulation demonstrates that the shut-on/off operation of large-diameter ball valves is mandatory to avoid fast destruction following partial opening. This paper also demonstrates why the metal-metal (MM) sealing with a double-piston effect (DPE) design for seats produces low leakage rates, including for the shut-off position; the pressure field reveals that few gas particles succeed in crossing the upstream sealing zone, and even fewer cross the downstream sealing zone. Additionally, the interpretation of the results explains and highlights the importance of using seats with a DPE design to achieve fire safety, which is required for natural gas pipeline applications. trunion ball valve; double-piston effect; valve seat; SolidWorks fluid flow simulation; natural gas pipelines; Repower EU Plan +
Footnote †: journal: Applied Sciences  
for the metal sealing components (i.e., the ball and the seats) of ball valves implemented in natural gas pipelines [5], but when the soil surrounding the underground pipeline contains salty hydrocarbons, the beneficiaries prefer stainless steel as the material. In the natural gas industry, a lot of categories of valves are used, including ball valves [6], check valves [7], plug valves [8], float valves [9], gate valves [10], and butterfly valves [11]. Safe operation is very important for natural gas transportation, and in this context, an appropriate design for the shut-off of large-diameter ball valves is crucial. The scientific literature proposes a wide range of methods to be used for research in thus domain. Computational fluid dynamics (CFD) can be used to obtain important information based on the analysis of the fluid flow in small or medium-sized ball valves by simulation. [PERSON], [PERSON] et al. investigated four different V-sector valve core opening shapes to be used in a DN65 ball valve. The best solution, designed to work with hot water in a secondary heating system, was identified by using ANSYS [12]. [PERSON], [PERSON] et al. proposed an innovative elastic valve seat for V-shaped ball valves, composed of a blade spring coil, a support back ring, and a sealing ring, adequate for powders or other media with granular matter. Mud with particulate matter was selected as the medium. The results of their study, based on fluid dynamics simulation with SolidWorks 2021 software and experiments on DN50, DN65, DN80, DN100, and DN125 ball valves, showed that the fatigue strength of the ball spool and the spring-loaded plate seat structure enabled the valve to comply with high safety standards. This highly efficient sealing is possible because it avoids the problem of sealing failure caused by granular media entering the spring cavity, or by the valve seat bonding on the valve body [13]. [PERSON], [PERSON] et al. used the finite element method to study the construction of a ball valve made of CF8M stainless steel. The purpose was to optimize the mass and the structural safety of the ball valve, with the target being an accurate flow coefficient. The analysis was carried out for seven opening positions of the ball: \(0^{\circ}\), \(15^{\circ}\), \(20^{\circ}\), \(30^{\circ}\), \(50^{\circ}\), \(70^{\circ}\), and \(90^{\circ}\).