In fractionation of atmospheric distillation resids, there has been a tendency to use water-circulating vacuum systems (WCVS) instead of the traditional steam-ejector vacuum systems (SEVS). The WCVS systems are more complex due to inclusion of a system for steam-and-gas stream transit from the circulation circuit of the working medium. However, the complication of the vacuum system and the related increase in capital expenditures are justified by the clear advantages of its operation.