A system for grit blasting an annular junction portion of a pipeline extending along a longitudinal axis on board a laying vessel, comprises at least one carriage configured to advance along an annular path about the pipeline; at least one centrifugal turbine, which is configured to project grit towards the pipeline, rotates about a rotation axis lying on a plane orthogonal to the longitudinal axis and is supported by the carriage; at least one feed device configured to feed the grit to the centrifugal turbine and comprising a hopper which extends along a respective axis, defines a feed chamber and is coupled to the respective carriage and a guide device configured to act in conjunction with the hopper to feed the grit to the centrifugal turbine at all the operating positions of the carriage.