A flow control system for filling a bag with a granular product, comprising [a] an acceleration conduit with: [i] a metering side, there being provided adjacent to said metering side a metering device comprising a metered amount holder movable between a) a holding position for holding a metered product amount, and b) a discharging position for discharging said metered product amount, and [ii] a filling side comprising receiving means for receiving a bag to be filled, [b] a first granular product passage sensor, provided at an intermediate point located between said metering and filling sides (4, 10), upstream of said at least one control blade and functionally associated with said control device, and [c] a second granular product passage sensor, provided on said filling side, the system further comprising [d] a flow control device, said control device being provided between said metering side and said filling side, [e] said metering device, said control device, and said first and second sensors (S1, S2) being functionally associated with one another such that said metered amount holder of said metering device moves between said holding and discharging positions, characterized in that [f] said flow control device comprises at least one control blade, said at least one control blade being movable between a plurality of control positions located between [i] a maximum opening position of said conduit in which a maximum flow of said granular product can pass through said control device, and [ii] a closed position of said conduit in which the flow of said granular product through said control device is interrupted, and in that [g] said at least one blade of said control device moves among one position of said plurality of positions depending on if said first and second sensors (S1, S2) detect an accumulation of granular product on said filling side which may delay the filling of said bag. [a] an acceleration conduit with: [i] a metering side, there being provided adjacent to said metering side a metering device comprising a metered amount holder movable between a) a holding position for holding a metered product amount, and b) a discharging position for discharging said metered product amount, and [ii] a filling side comprising receiving means for receiving a bag to be filled, [i] a metering side, there being provided adjacent to said metering side a metering device comprising a metered amount holder movable between a) a holding position for holding a metered product amount, and b) a discharging position for discharging said metered product amount, and a) a holding position for holding a metered product amount, and b) a discharging position for discharging said metered product amount, and [ii] a filling side comprising receiving means for receiving a bag to be filled, [b] a first granular product passage sensor, provided at an intermediate point located between said metering and filling sides (4, 10), upstream of said at least one control blade and functionally associated with said control device, and [c] a second granular product passage sensor, provided on said filling side, the system further comprising [d] a flow control device, said control device being provided between said metering side and said filling side, [e] said metering device, said control device, and said first and second sensors (S1, S2) being functionally associated with one another such that said metered amount holder of said metering device moves between said holding and discharging positions, characterized in that [f] said flow control device comprises at least one control blade, said at least one control blade being movable between a plurality of control positions located between [i] a maximum opening position of said conduit in which a maximum flow of said granular product can pass through said control device, and [ii] a closed position of said conduit in which the flow of said granular product through said control device is interrupted, and in that [i] a maximum opening position of said conduit in which a maximum flow of said granular product can pass through said control device, and [ii] a closed position of said conduit in which the flow of said granular product through said control device is interrupted, and in that [g] said at least one blade of said control device moves among one position of said plurality of positions depending on if said first and second sensors (S1, S2) detect an accumulation of granular product on said filling side which may delay the filling of said bag.