The Infrabolt system was developed to be used on existing turnouts to replace timber sleepers with Concrete Universal sleepers.
The significance of the Universal Concrete Sleeper in conjunction with the Infrabolt system is that it uses standard sleepers, which can be mass-produced and used in exactly the same way as timber sleepers. They are inserted under the track and only then are the bolt holes drilled.
During the development of the system the following had to be considered:
- The baseplates on the existing turnout had to be re-used and therefore the Universal Sleeper had to be drilled to accommodate the dimensions of the holes in these baseplates
- The System had to be fully insulated
- No protruding bolts or studs could be used that would hamper the removal of sleepers
- No chemical epoxies or grouts could be used
- The sleeper had to be re-usable in terms of replacement of new steel hardware
- The fastening system had to allow undrilled Universal Concrete Sleepers to be stored for new installations or emergency work.
The availability of a coring drill that could drill a sleeper in less than 1 minute ensured that Infrabolt met the above criteria. The system was thus approved by Transnet.
The System consists of the following:
- M18 x 195 Hexagon flange bolt grade 8.8
- M18 x 2.5 x 80 Hexagon tube nut
- 2 Flat round washers
- High viscosity nylon insulating sleeve