A track renewal train has a series of machinery units that are combined into one train. As the track renewal train moves forward, the track renewal process will be done stage by stage to the completion of track renewal as it leaves the area.
Old sleeper removal The first stage of track renewal is the removal of old sleepers. The releasing rail fastening system from the sleepers may be part of this process. Some machines integrate the semi-automatic clip-releasing devices by hoisting such devices as part of the track renewal train to allow operators to manually position the device to each clip and trigger it to automatically release the clip. Some units have a machine to automatically remove spikes in the older type of wooden sleepers. Some machines have an automatic track copying by recording the
track geometry of the old rails prior to the removal, then the machine will calculate the exact amount to clear the ballast bed to prepare for laying new sleepers and rails to match to the original geometry of the old ones in term of cant, leveling and positioning.
New sleeper laying There are
gantry cranes attached to the top of the track renewal train. These cranes run along the special side rails of the train. These special rails also connect between cars allowing operators to travel along the entire length of the train. The cranes are used to transport old sleepers into the storage area and bring the new sleepers into the working area. The new sleepers are delivered by the cranes to feed into the machine. The machine puts sleepers onto the ballast bed and spaces them to the exact position required by specification.
New rail insertion After the new sleepers are laid, the new rails will be pushed from the side of the train into position on the sleepers. To prevent
rail stressing due to temperature fluctuations during normal operation, the rail will need to be laid at a precise temperature, based on anticipated operating temperatures. This is done by heater units of the track renewal train that warm the rails to the specification before laying on the sleepers. Another unit has an automated process to clip the rails onto the sleepers. Depending on the models of the track renewal train, the old rail will be laid either inside at the center of track or outside the new track at the shoulder waiting to be picked up by another work train. At the end, a large crane or conveyor belt with a magnet will be used to take all loose parts that have been left on the tracks to storage for reuse or recycling. The new track will be inspected prior to the ballast handling
Ballast handling After the track renewal train completes the tasks, the ballast will be put back on the track. For track renewal trains that do not have ballast excavating machines included, workers will use a shoulder ballast cutter machine that takes excess ballast that has been pushed out during the track renewal process, into a screening and cleaning machine. The reusable ballast will be put back to the new track together with the new ballast materials. For track renewal trains that do not include track copying or leveling, a
ballast tamper will be used to make final adjustments to the track to the correct specification. A
ballast regulator will then be used to make the final shape of the ballast. Some track renewal train units have the ballast handling included such that the entire process of shoulder cutting, cleaning and placing of ballast is fully integrated. ==Examples==