Abstract: Method and apparatus for pneumatically transporting solid and abrasive particulate materials at high temperature, by means of a carrier gas through a plurality of co-axial straight pipes. The pipes are maintained under constant tension by applying a force across at least one expansion joint coupling said pipes in order to maintain said pipes straight against the forces acting on said pipes which tend to cause bending and deformation thereof, as for example: thermal elongation, the weight of the solids conveyed through said pipes, the friction forces between said pipes and its supporting frame, and the pressure of the carrier gas inside said pipes. The constant tensioning force may be applied for example, by means of hydraulic cylinders in combination with a telescopic water-cooled sleeve.