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Japanese precision

Track possessions on Japanese high-speed lines are short. Tracks are not closed for maintenance works. Rails and sleepers must be exchanged in the shortest possible time. This is why staff, machines, and design engineers must meet particularly high requirements.

Speed and perfection according to schedule

Japan is a prime example for speed and precision in rail traffic. There is no place else in the world where trains run at such high speeds and where they are on time with such a high level of consistency. On average, 270,000 persons are transported on the Tōhoku Shinkansen every day between 6 a.m. and midnight. Maintenance work on the infrastructure are expected to be performed with the same level of punctuality. A time window from midnight to 5 a.m. is scheduled for track maintenance. Due to the maintenance vehicles’ long travelling times to the track sections that have to be maintained, the time window effectively available for maintenance works is 150 minutes. 

Before the track is reopened for the first high-speed train, the entire line is scanned by inspection vehicles, which search for tools or other objects that were left in the track but do not belong there. On the Shinkansen, temporary or long-time speed restrictions are not an option, perfection according to schedule is – also when maintaining the track or exchanging rails or sleepers.

REX-S Rail Exchange System

Optimal planning and excellent technological support are in demand. Together with the partner companies Nippon Plasser and ROBEL Bahnbaumaschinen GmbH (Germany), Plasser & Theurer supplied the REX-S 1200 rail exchange system in late 2016, after two years of development and manufacture. It uniquely combines transporting, depositing and welding rails. Due to the short time windows, a complete exchange of the rails is not possible. Therefore, 150 m long rail sections are pre-deposited and the APT 1500 RA mobile flash-butt welding machine welds them to section of up to 1200 m. In addition, the rails are ground and fixed. During a second night-time track possession, the old material is exchanged with new material within 30 minutes using two REX-S special vehicles, and the rail ends are joined with pre-tension – also using the APT 1500 RA welding robot. For the first time since the Tōhoku Shinkansen of East Japan Railway Corporation (JR East) was put into operation in June 1982, the rails are being exchanged. The works started in February 2017. They are scheduled to be completed by 2026. Using the REX-S, the length of the rails to be installed was increased fourfold. At the same time, the welding time per joint was reduced from 40 to about 6 minutes.

The specially designed REX-S machine consist for 1,435 mm standard gauge is composed of a tractive unit – a modified SILAD loading train and unloading train for twenty up to 150 m long rail sections by ROBEL – two rail unloading and positioning wagons and an APT 1500 RA welding machine in lightweight design. All machines reach the work site at the same time. The machines’ dimensions were set to constructional limits: To ensure that the consist can be parked in Japanese depots, the REX-S must not exceed a total length of 230 m. The distance between the bogie pivots of the individual vehicles must not exceed 14.4 m. Their maximum axle loads are limited to 15 t.

Welding on narrow-gauge tracks

In 2015, Plasser & Theurer supplied an APT 1500 RA for the operation on 1,067 mm narrow gauge tracks to JR Kyushu. The maintenance windows are not as short as on JR East’s Shinkansen, the technological requirements, however, are similar. Before we were able to introduce the innovative electric flash-butt welding process onto the market, a new type of method for Japan, we had to provide extensive quality certificates. The traditional Japanese welding method is similar to the flash-butt welding process, but uses a gas burner. This is why the heat-affected zone in the rails is far greater. To prove the consistently high welding quality during flash-butt welding, the welding machine was tested using rails, which were delivered to Austria particularly for testing. The Japanese Railway Technical Research Institute (RTRI) checked the results. To test closure welding, which is an integral part of the exchange of rails, a separate test rig was set up in our factory.

Exchange of sleepers without exchange of rails

JR East had to exchange rails, JR West had to exchange sleepers. For these works, Plasser & Theurer supplied a special unit to Japan in 2015: the SES 170 continuous action sleeper exchange system. It exchanges old sleepers with new sleepers within intervals of 20 seconds, without spreading or cutting the rails. Following preparatory work such as loosening rail fastenings, and the removal of the ballast stones by vacuum, the old sleepers are turned underneath the rails and removed. Prior to the installation of the new sleepers, the ballast formation is regulated. Problem: The new sleepers are significantly larger and heavier than standard European sleepers and they are placed at less distance. Moreover, there are two types of sleepers – with and without cable bushing. A gantry unit on the SES 107 brings new material and removes old sleepers. Close to the place of installation, three sleeper tables are mounted on the machine. The SES places the ballast removed by the vacuum excavator in the track wherever required. Following behind, a tamping machine and a ballast profiling machine finish the track.