A new visbreaking unit with output of 1.5 million tons a year in vacuum resid was started up at Salavatnefteorgsintez Co. A separate reaction chamber (soaker) is provided in the unit for increasing the degree of feedstock conversion and reducing coking of furnace coil tubes. To increase takeoff of gasoil cuts, the unit is equipped with a vacuum block. Heavy and light vacuum gasoils are used for preparation of type M-100 atmospheric resid.