Step by step to an automated tamping process

Step by step to an automated tamping process

Plasser SmartTamping is a flexible automation solution consisting of three core components. These modules can be used either individually or fully integrated on machines, thus offering a high degree of scalability.

Automatically positioning and controlling the various work units ensures precise and efficient working, especially in demanding environments such as turnouts and crossings.

During penetration, the tamping unit is lowered to the required depth in a controlled manner.

The right squeezing force and squeezing time are of central importance during compaction. Plasser TampingControl automatically optimizes these values to ensure ideal compaction.

Simulation of the load distribution under a sleeper after squeezing times of 0.6 s, 1.2 s, and 2.5 s. Red areas indicate high loads. It is clearly recognizable that squeezing times that are too short result in poor force distribution and heavily loaded zones under the sleeper, which reduces the service life of the track position.

Increasing capacity utilization, shorter track possessions, and staff shortages require maintenance measures to be optimized. The automation of work processes is therefore becoming increasingly important. An essential basis for this is to divide complex processes into individual steps in order to identify key factors with an impact. This method has already proved itself in tamping.

Tamping is important for creating or restoring the target track position, which is crucial for ride comfort, cost-effectiveness, and safety. What phases does a tamping process entail and how can they be optimized?

The tamping process is divided into six steps (shown clockwise here). For a first-rate result, it is crucial to analyse and optimize each of these steps precisely.

Positioning

At the start of the tamping process, the tamping unit is positioned precisely over the sleepers, as deviations can lead to asymmetrical squeezing distances and possible damage to sleepers and tamping tines. Various systems available on the market facilitate this positioning by recognizing individual elements and obstacles in the track and calculating the optimum tamping position. One advanced approach is the AI-based Plasser TampingAssistant system, which not only takes care of positioning, but also recognizes obstacles and blocks individual tamping unit segments if necessary. At the same time, it controls the lifting and lining unit as well as the sleeper-end ballast consolidator, allowing even complex turnout areas to be treated fully automatically.

Lifting and lining

Track geometry defects are deviations from the target position of the track and can have recurring patterns with specific wavelengths. During lifting and lining, the track is brought into its target position before it is tamped. Modern tamping machines make it possible to proactively counteract future track geometry defects by detecting short-wave hollows and correcting them through targeted overlifting to create a reserve for the track geometry.

Penetration

After positioning the tamping units, the tamping process is initiated by lowering them to the required depth, usually 15 to 20 mm below the lower edge of the sleeper (Figure X). Modern tamping machines calculate an optimum trajectory in advance for precise, slightly time-delayed tamping, which reduces loading on the tamping units and ballast wear. In a joint project between ÖBB, SBB, Graz University of Technology, and Plasser & Theurer, the Plasser TampingControl – BallastMonitoring system was developed: it determines the ballast condition in real time during the penetration process. This data is used to automatically adjust the tamping parameters.

Squeezing

Squeezing is central to the tamping process: the ballast is moved and compacted under the sleeper by the vibrating tamping tines to fix the sleeper in the target position. Tamping quality is influenced by parameters such as vibration frequency, amplitude, squeezing time, squeezing force, and tamping depth. The process can be divided into two steps: filling (moving ballast under the sleeper) and compacting (ballast compaction to ensure a stable track position). If the cavity under the sleeper is not sufficiently filled and compacted after lifting, this leads to increased track settlement and reduced stability of the track position.

Filling

In the first phase of the squeezing process, the tamping tines push the ballast into the void under the sleeper. The squeezing speed is initially high as resistance is low. As soon as the void is filled, resistance increases and the squeezing speed automatically decreases. The working principle of non-synchronous constant pressure tamping ensures that the squeezing movement automatically adjusts to the respective conditions, thus ensuring careful ballast movement. As the filling process is difficult for the machine operator to monitor, infrastructure managers have developed guidelines for minimum squeezing times. However, they do not always guarantee optimum results. To solve this problem, Plasser & Theurer has developed the Plasser TampingControl – VoidDetection system, which monitors the squeezing movement and forces. If filling is insufficient, the operator is warned so that additional tamping can be carried out.

Compaction

After filling, the ballast is compacted due to the vibration superimposed on the movement of the ballast. An optimum squeezing force is crucial, as excessive forces can cause ballast breakage. The Plasser TampingControl – ForceAutomation system adjusts the squeezing force to the conditions to ensure effective compaction. Moving the ballast grains into a denser position is essential for the stability of the track position. The squeezing time is also crucial. Squeezing times that are too short lead to insufficient compaction and increase track settlement during operations. This inhibits force distribution under the sleepers and shortens the service life of the track position.

Lifting

After the squeezing movement, the tamping unit is lifted out of the ballast again, with the tamping tine arms opening and a vibratory movement being superimposed. This movement facilitates movement of the ballast grains in the area of the tamping tines’ reach, ensuring more homogeneous compaction in the sleeper crib as well as greater lateral track resistance.

By analysing the individual phases of the tamping process in detail, it was possible to achieve targeted optimization and automation. These steps contribute significantly to the efficiency and reliability of track maintenance and pave the way for a fully automated future.

Further information

Show all articles