The potentials between static sources in various representations in SU(3) are calculated on the basis of the fat-centre-vortices model of Faber, Greensite and Olejník. At intermediate distances, potentials are in qualitative agreement with "Casimir scaling," which says that the string tension is proportional to the quadratic operator of the representation. At large distances, screening occurs for zero-triality representations for the representations with non-zero triality the string tension equals that of the fundamental representation.