High level of automation and high pre-tensioning forces
Thanks to the low number of moulds required, the DSR process offers utmost flexibility. Moreover, the high level of automation in a DSR plant reduces personnel requirements to a minimum. Conversion for different sleeper types or rail fastening systems is carried out in the shortest time. In the DSR process, wires are pre-tensioned in a frame. Hereby, tensile forces up to 500 kN per sleeper are possible. The innovative approach of crossing four of the eight tendon wires per sleeper ensures an optimum force distribution in the prestressed concrete structure, as required for rail tracks. Consequently, sleepers produced with the DSR process are also suitable for high-speed railways with speeds exceeding 300 km/h, and for wheelset loads above 25 kN per axle.

The manufacturing procedure
Each tensioning frame contains 6 moulds. When the concrete has been poured, the moulds and the frame are covered with a steel pallet. The resulting sandwich, consisting of palette, tensioning frame, and moulds with freshly-cast sleepers, is turned upside down, enabling the moulds to be removed upwards, which leaves the tensioning frame and the sleepers on the palette. In the curing magazine, the palettes and tensioning frames are stacked to form climatic chambers. A specially insulated cover closes the top of each stack. After curing (about 16 hours with good concrete quality), the tensioning frames are cut away, which transfers the tensile force of the wires to the sleeper.

Manufacturing options using the DSR process:
Standard rail sleepers
Sleepers for craneways