The aim of the work is to develop mechanical equipment for resource-saving technology of applying liquid slag to refractory lining of 250-ton converters in order to form a protective layer of slag garnish on its working surface. On the basis of the conducted set of industrial experiments the hypothesis of significant increase of BOF lining durability with organization of liquid slag blow with its primary run-out on the most worn trunnion zones was confirmed for the first time. In order to check this hypothesis, the new design of skull lance (patent protected) with grouped lance nozzles of different cross-section at the face of lance tip was developed, produced and tested. This allowed to form the protective slag layer at the working surface of liner both at the bottom part (walls) of converter and at the mouth of the unit. In the course of the converter's campaigns, this ensured that the more worn areas of the converter's lining would be repaired by forming a thicker slag layer on them, thus obtaining a total lining thickness (masonry + slag layer) on these areas that is almost the same as on the other (less worn) working surfaces of the lining with reduced slag carry-over from the converter and reduced refractory consumption.