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News From Around The World: Italy

Economic maintenance of tracks and turnouts in high-speed traffic

The Unimat Combi 08-275 is fitted with Plasser & Theurer’s non-contacting GPS based inertial track geometry system – this is how we extend the field of application of our universal tamping machines.

In 2010, the first Unimat Combi 08-275 was supplied to Rete Ferroviaria Italiana (RFI) in Bologna. Now, RFI has five Unimat Combi 08-275. The machines are operated by the permanent way districts of Naples, Florence, Reggio di Calabria and Palermo. Until the end of 2017, Plasser & Theurer will supply further new machines. All of them will be fitted with the automatic train control system mandatory in Italy.

The machines are used for spot fault elimination on both high-speed and conventional lines. Three times a week, about 1,000 m of track and one or two turnouts are tamped, profiled and swept during night-time operation of four to five hours.

Special requirements for track geometry on high-capacity lines. In Italy, high-speed lines are checked for long-wave track geometry faults with wavelengths of up to 200 m. At present, surveying is mandatory only on high-speed lines. The EM-SAT or manually operated measuring devices are used to record the required absolute data. To ensure optimum results, the Unimat Combi is fitted with our inertial track geometry measuring system. The DRP used for the control measurement only detects short-wave track faults. Due to the lowered measuring axles, the maximum speed is 5 km/h. The inertial track geometry measuring system, however, measures both short-wave and long-wave track faults (D2 and D3) at speeds of up to 100 km/h. The measured data can be imported into the ALC automatic guiding computer.

Inertial track geometry measuring system for recording track parameters. The non-contacting, GPS based inertial track geometry system consists of the IMU inertial measuring unit, GPS antenna, rate gyro and the optical gauge measuring system. The inertial measuring unit and the four gauge measuring units are installed on one measuring frame mounted on the axle bearings of the bogie. It is guided parallel to the rails, measuring its motion paths using the rate gyro. Based on the measured data, the track parameters are extrapolated. Today, this track geometry measuring system is in use on more than 60 track recording cars and machines all over the world and meets every requirement stipulated in the European standard EN13848-2 “Track geometry quality – Part 2: Measuring systems – track recording vehicles”.

Control measuring using the inertial track geometry measuring system. Measuring frame and sensor technology are mounted on the rear bogie of the UNIMAT COMBI 08-275. The GPS assisted inertial track geometry measuring system detects track faults quickly and precisely. Following tamping, ploughing and sweeping, control measurements are carried out. This is why a separate measuring car is no longer needed. In most cases, RFI carries out a measurement also prior to tamping for before/after comparisons. Measuring axles and the SmartALC guide the machine during work.

The inertial track geometry measuring system records the track geometry with regard to long-wave faults (D2 and D3) and short-wave faults (D1) according to the RFI guideline on track maintenance. Track geometry faults are documented in the measuring graph and the fault report. On secondary lines, RFI uses the tamping machine also as track recording car. The recorded data is analysed and a control measurement is carried out after tamping. 

The measuring system reduces the time required for the working operations, thus making a further important contribution to the economic maintenance of railway lines using our machines. 

Plasser & Theurer track geometry measuring system

The high-precision track geometry measuring system of Plasser & Theurer records the following parameters:

  • track gauge (dual measurement)
  • longitudinal level (display of space curves and chords)
  • superelevation
  • twist (difference between two superelevation measurements)
  • alignment (display of space curves and chords)
  • track gradient
  • curvature and radius

By comparing the measured data with the target values, faults in the track geometry are detected. They are displayed on the measuring graph and summarised in tabular form on the exception report.

A GPS location is assigned to each measuring point, regardless of the quality of GPS reception (e.g. in tunnels). This enables track faults to be detected easily and quickly.

For different line categories (line speeds), faults in different wavelength ranges are important:

D1 = 3 < λ ≤ 25 m

D2 = 25 < λ ≤ 70 m

D3 = 70 < λ ≤ 150 bzw. 200 m (depending on the parameters)

λ stands for wavelength

The Plasser & Theurer track geometry measuring system produces precise measuring data for all wavelength ranges, regardless of the measuring speed (0 to 300 km/h).

The repeatability and reproducibility of the measured parameters is equal to or better than the values required by the European standard EN 13848-2. The resolution for all measurements is 0.04 mm.