An inducer for a casing of a gas turbine system is disclosed. The inducer includes a plurality of orifices defined in the casing, the plurality of orifices disposed in an annular array about the casing, and a plurality of cartridges, each of the plurality of cartridges configured to mate with one of the plurality of orifices. Each of the plurality of cartridges includes an inlet and an outlet for flowing a cooling medium therethrough. The inducer further includes at least one flow modifier disposed in each of the plurality of cartridges for modifying the flow of the cooling medium through each of the plurality of cartridges. Each of the plurality of cartridges is independently removable from each of the plurality of orifices.