Soviet motor tug Sakov active on the line Vienna-Ismail-Vienna according to a CIA report dated 21 May 1952

An item reported that Hungarian petroleum first was shipped to the cracking plant at Vienna, Austria and from there was the gasoline shipped towards Ismail, Ukraine usually with Soviet DDSG ships and rarely with Hungarian vessels. Oil tankers of the Hungarian Meszhart were usually unloaded in the Hungarian Danube harbours and did not go the Soviet Union. On their return voyage were barges towed loaded with crude oil or iron ore. The barges loaded with gasoline were in the harbour of Braila exchanged for barges loaded with crude oil coming from the Romanian minefields destined for the cracking plant at Vienna while the iron ore was shipped to Bratislava, Czechoslovakia. At Ismail were 28 gasoline storage tanks available. A voyage Vienna-Ismail-Vienna needed usually 35-40 days making it possible for a tug to make 8-8 voyages in a year. The Soviet DDSG owned motor tug Sakov with a towing capacity of 500 tons  and a horsepower of 700hp was used on this route.

Source
The report was published on www.archive.org, document number CIA-RDP82-00457R011900230009-0