SD means ‘Safely Driven’, referring to the controlled clip guidance from the parked to the in-service position. In addition to its ability of pre-assembly in the concrete sleeper, SD systems have also been designed in order to offer high rates of installation by mechanical methods.
The screws are tightened to refusal which generate the clamping force and longitudinal restraint.
SD fasteners have been developed for a wide combination of support types and construction methodologies eg. new concrete sleepers, retrofitting existing concrete sleepers (including SKL), installation on plastic baseplates, dual gauge applications and plastic baseplates for slab tracks.