The present invention concerns a system for storage and offloading of granular materials. The system comprises a tank (1) for storage of a granular material anda suction head (3) for offloading granular material from the tank (1). The suction head (3) comprises a lower end (3a), an outlet (3b) for removing granular material from the suction head (1), and sidewalls (3c), extending from the lower end (3a) to the outlet (3b). The suction head (3) further comprises at least one opening for the inflow of granular material into the suction head (3) and one or more nozzles configured to emit a pressurized fluid. The one or more nozzles comprise one or 0more inner nozzles (3a), configured to generate a helical flow within the suction head (3), and one or more outer nozzles (3b), configured to generate a helical flow around the suction head (3) in the same direction as the inner nozzles (3a).The present invention also concerns a method for storage and offloading of granular materials.