Upgrade from the assembly line - the ecological procedure

The railway line to Cuxhaven running to the north-west from Hamburg was renovated in stages. Improvement of the formation, cleaning the ballast bed, replacing rails and sleepers and thorough maintenance of the track were among the tasks carried out in several phases of construction in a three-week window.

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All this yellow on the railway line from Hamburg to Cuxhaven was a rare sight. In spring sections of the line near Stade were renovated. A full closure of the line could be avoided thanks to powerful, highly specialist but flexible track construction machines. The suburban railway traffic between Hamburg and Stade could continue running. And as a matter of course everything was finished on time, dual track operation could be restarted as scheduled once the work was completed.

Larger-scale railway construction work usually takes place during school or public holidays so that fewer commuters are affected. The time around Easter 2016 was one such peak construction period in the railway calendar. One of the work sites: track renewal with ballast bed cleaning near Horneburg and Dollern stations between Buxtehude and Stade. The northbound track was closed for this purpose. The complete work site logistics focused solely on this track, appropriate storage sites at the track were made available for the supply of the track materials - largely by railway - and the removal of spoil and old materials. So it was possible to keep the disruption to rail traffic and passengers to a minimum. 

Scenic route through green fields

The “Niederelbebahn” from the Hamburg area to Cuxhaven, which was 135 years old at the time the renovation work started, is the northern end of the line from Lehrte to Cuxhaven with line number 1720. Since 1st April 1881 the line has been running as a dual-track main line from Hamburg-Harburg in northwest direction via Buxtehude and Stade through the “old country” known for its apple orchards to Cuxhaven, directly at the estuary of the river Elbe.

Nowadays the non-commuting travellers are often tourists starting their journey from Cuxhaven when going to Helgoland, for instance.

Cuxhaven station is not accessed by Intercity rail services. Therefore, the hourly connections of the so-called “Metronom” regional express train RE 5 to Hamburg are well frequented. In the southern line section from Stade there is also the suburban railway service S 3, which runs at 20-minute intervals via Buxtehude, Harburg and the City of Hamburg to Pinneberg. During the construction work over several weeks the Metronom was not in operation, the suburban railway was bridging the gap between Buxtehude and Stade, at longer intervals of 40 to 60 minutes. Freight traffic was running as normal during the construction work. Cuxhaven is also a departure and destination point for automotive logistics. Closing the line completely would have been unimaginable. 

Lot 20 of the construction project, which was carried out around Easter 2016, concerned the line section north of Horneburg to Agathenburg station, about 7 kilometres away. The section of track towards Cuxhaven was to be renovated. The construction schedule comprised 27 working days and, after a gap of several weeks, another three nights for the final re-tamping of the renovated section of track. The contractor and coordinator for the multi-phase construction project was the Munich affiliate of the Austrian company Swietelsky Baugesellschaft mbH. Swietelsky has its own very extensive fleet of machinery and suitably trained specialist staff. The machinery is deployed throughout Europe. Some of the machines used here, such as the PM 1000 URM formation rehabilitation machine or the MFS material conveyor and hopper units, belong to the “Eurailpool” group that Swietelsky is a member of.

The three-week project directly at the transition from the coastal moorlands at higher altitudes to the damp marshland, in forest areas and in a slight dyke location between wide fields was carried out in several construction phases. After preparatory work the week before - always done during train intervals - the closed track was under possession for dismantling the railway control and signalling equipment and minor associated work.

The first machine to be used in three partial sections of track was the PM 1000 URM formation rehabilitation machine, an all-rounder that can be deployed for various tasks of track renewal. Its remit was to clean and replenish the ballast and to fit a new formation protective layer. It was only necessary to install geotextile fabric in short sections. Next step: transport units placing the new rails onto the sleeper ends. The RU 800 S ballast cleaning and track renewal machine replaced old material with new rails and sleepers. It also cleaned the ballast in those sections where a new formation protective layer was not required. The renewed track was then worked several times by an 09-4X Dynamic Tamping Express and an EM-SAT 120 Track Survey Car. At the same time the BDS 2000 Ballast Management System was used to optimise the ballast distribution. Before operations on the track could be recommenced the long rails needed to be welded and the control and safety equipment as well as the level crossings had to be re-established.

In addition to the machines mentioned, trains consisting of MFS and transport wagons as well as smaller vehicles were used in this project. 

With existing lines it is important that the machinery is able to work past passenger stations and other narrow places on the track without stopping, if at all possible, and of course without affecting the work results. The PM 1000 URM and RU 800 S are able to work past narrow places such as bridges, walls and railings by adjusting the working width of excavating chains and plate compactors. Regardless of their design and height, platform edges are no obstacle for the RU 800 S which is specially equipped to deal with them. This was impressive to observe at the Dollern station platform, which also lies in a curve (height of 760 mm). All machines used were able to work through level crossings without stopping once the crossing plates and fastening components had been removed. They were refitted after the track work had been completed. Asphalt layers were replaced with new systems. 

To save on the use of new ballast, its transport and the associated considerable cost, the existing ballast was first cleaned and treated. The recyclable components were refitted while the spoil that was no longer usable was removed by the MFS units and deposited away from the track in Horneburg. The PM 1000 URM carried out the cleaning and recycling of the ballast as well as the installation of a formation protective layer. Depending on the quality of the existing track bed, the machine enables up to 100 percent of the track bed material to be reused and it can also respond to different load capacities of the subgrade. It was mostly not necessary to fit geotextile fabric because, after compaction, the 30 cm thick formation protective layer FPL already ensured the required load-bearing values despite the nearby marshland. It became obvious that 135 years ago people knew very well where to lay the track.

With three excavating chains the PM 1000 URM is as fast as it is thorough in excavating the existing material at any required width and depth. In the forward direction of working, the excavated material is transported to the ballast recycling, screening and washing wagon. The spoil for disposal is conveyed on belts to the construction train of MFS units coupled on to the front. The new material for the formation protective layer and to top up the ballast is simultaneously fed from the rear end of the 52-axle, ten-part PM 1000 consist of wagons. Here it is transport wagons with containers, not MFS units, that form a second construction train. Both construction trains - with spoil at the front and with the material for the FPL and new ballast at the rear - travel to the disposal and loading sites along the line, independently of the PM 1000 URM. To do this they are coupled with main-line diesel locomotives. To shorten the distances, the storage area for new material of the intermediate layer had been set up at a road leading to Dollern level crossing (which was under possession anyway) and protected with a mat. While lorries brought in more material a wheel loader loaded the containers, also known as buckets, in quick succession.

The containers were then transported using two gantry units running at the top of the transport wagons. The rear gantry unit continually brings along two containers whilst the gantry unit running closer to the machine tips one container load at a time into its bunker - either with the material for the FPL or the ballast bed, depending on the requirement. This relay system with container handover shortens the travelling distances of the two gantry units and thus accelerates the processes. The observer can see gantry units constantly moving containers to and fro at the top of the transport wagon throughout the whole working period. Their paths only cross at the respective handover point.

The plate compactors following straight after the intermediate layer installation can avoid any foundations, walls and railings next to the track in variable working width. Once the FPL and ballast have been reinstalled a tamping satellite with lifting and lining unit, which is integrated into the machine, concludes phase 1 of the permanent way reconditioning, with the old track still in place. Construction trains can travel on the track straight away at a remarkable speed of 70 km/h. Overall, the PM 1000 URM achieves a considerable output: At the nearly 5,000 metre long construction sections at Dollern, it was continuously in operation for around 50 hours day and night over the Easter weekend. 

In the next step, sleepers and rails had to be replaced. The bed had to be cleaned in further sections of the work site – here without renewing the FPL. The RU 800 S, another single, complex machine, dealt with this in one operation. After removal of the old sleepers it excavates the ballast, cleans it, temporarily stores the reusable parts and reinserts them on the track together with the new ballast. Next the new sleepers are laid and then the new rails are placed on the fastening points. Held by numerous rail guiding clamps, the old rails are simultaneously and continually exchanged for new ones by the RU 800 S. Owing to its construction with two independently controlled shoulder spaces the machine is also able to work along platform edges and excavate the ballast there.

Even the process of replacing rails is not impeded by platform structures. By guiding them skilfully beside and above one another, i.e. by lifting and moving them out, the rails swap their places on the rail fastenings and sleeper ends. They are subjected to only minimal bending stresses as the free work space is 45 metres long. This is only possible because the machine lifts at the centre and therefore lifts the centre bogie while at the same time the two 4-axle end bogies are manoeuvred outwards. Once the new track is in place an 8-spindle wrench is used to tighten the rail fastenings.

The RU 800 S, too, makes use of gantry units that continuously convey new and old material in a relay system. In this instance, however, these are two identical units each of which moves 30 sleepers. The new sleepers are fed in from the front in working direction and laid down. Then, the same gantry unit picks up and transports the old sleepers dispensed and collected by the track renewal machine one level lower down. These old sleepers are laid down on the space that has become available on the wagon consist coupled at the front. As there are no longer sidings on the Buxtehude to Stade line the transport wagons had to be swapped in Hamburg for others carrying new sleepers. This was done overnight.

New ballast is supplied continuously from the rear end of the machine. For this purpose, MFS units are coupled and will occasionally travel to the loading station where the ballast store is replenished. The RU 800 S was in operation at this work site for three ten-hour shifts. It was not working in the evenings and during the night. On the third day this job was completed as planned. Punctuality is routine: Dates had been scheduled long before for work sites in Luxembourg, Austria and Scandinavia to follow immediately afterwards. 

Like the PM 1000 URM, the RU 800 S, too, leaves behind a track that construction trains can travel on. As a result, it is not necessary to perform an additional stage of work between the work sequences. Of course, the track will still need to be prepared for the railway service and its precise nominal geometry established. First, more ballast was distributed, followed by the deployment of the 09-4X Dynamic Tamping Express with 4-sleeper tamping and Dynamic Track Stabiliser. With its continuous method of working and the manoeuvrable tamping satellite it is possible to work at considerable speed - any watching pedestrians had to hurry. The high working speed of the final tamping work is another decisive factor for the short overall construction period. Several tamping cycles were out one after another. Since a further supply of ballast was required, subsequently another construction train loaded with ballast, followed at some distance. MFS units were not required here as the ballast was supplied directly onto the track. 

Ballast is a valuable resource. To prevent ballast being left lying unnecessarily, e.g. on the shoulders of the ballast bed, the BDS 2000 ballast management system was used on this work site. Its shoulder ploughs and the centre plough plus the sweeper unit in the rear machine section remove excess ballast after the tamping operation and re-distribute it or temporarily store it in the bunker. An MFS wagon was running between the two machine parts of the BDS 2000 in order to increase capacity. 

To record the track geometry, an EM-SAT 120 Track Survey Car was in operation at this work site between the tamping express and BDS. This unit for electronic recording of the lateral, longitudinal and vertical geometry of the track helps achieve the perfect end condition. The small, independently travelling satellite car first followed the tamping express and then stopped at one position. Then the main machine was approaching. Using a laser long chord between the two vehicles as well as the data recording in the survey car the actual geometry was determined for each section, i.e. the level and alignment of the track in combination with fixed points (for instance, overhead line masts). This is recorded by 8-channel recorders, and all measured values are stored digitally.

Numerous MFS units were used for the material logistics. When supplying material and removing spoil they are able to fully exploit their advantages such as through-conveyance of the load from the end of the train to the front. Moreover, it was possible to use the conveyors to deposit the spoil directly at a disposal site next to the track for later removal, an invaluable advantage for keeping distances and times short. If an MFS train was withdrawn from the construction machine for emptying or loading, some MFS wagons remained there, in order to prevent any potential stoppages due to supply or disposal constraints. After only 27 intensive working days for man and machine the track upgrade of the line to Cuxhaven was completed. Safe railway operations on both tracks could recommence as planned. 

The work site in figures

The machinery used at this work site - some of which was unique - moved 10,000 t of new ballast. 3,500 t of material was used for the formation protective layer. A far greater amount of ballast was cleaned and reused. The quantity of spoil to be removed amounted to around 11,800 t. Furthermore, 10,800 new concrete sleepers and 13,120 m of S 54 rail profile were transported and installed.