For smelting of high-quality metal for the applications in transport vehicles, it is necessary to limit the content of harmful impurities in it, including dissolved gases. For example, hydrogen content in the finished product should not exceed more than 2 ppm. In order to obtain low residual hydrogen content in steel in the converter shop of JSC EVRAZ NTMK, the transport metal is processed at circulating vacuuming plants. Circulating vacuum degasser is the last stage of steel processing before casting on continuous casting machine, so it is important to study and improve the technological processes in it. To investigate the physico-chemical processes occurring in this metallurgical unit, a hydrodynamic model was created for the system that includes the circulating vacuum degasser and the steel ladle. Based on theoretical calculations using physical model and experiments conducted, the main dependencies between the structural and technological parameters of the metallurgical unit were determined. The resulting equation makes it possible to determine the rate of metal circulation in vacuum chamber depending on the gas flow rate supplied to inlet snorkel and its inner diameter at circulating vacuuming plants designed for metal processing in steel ladles with a capacity of 140–180 tons. Theoretical calculations were confirmed by practical smelting in a steelmaking unit. It is shown that in order to obtain stable residual hydrogen content during the wear of lining of the inlet snorkel vacuum chamber, it is necessary to make changes in the technological process of vacuuming. Additionally, rational technological parameters of steel processing at the circulating vacuuming plant were determined on the basis of theoretical calculations.