The Right Concept
The
When tamping a sleeper the tamping tines penetrate the ballast and perform a closing movement, called squeezing. A vibration in the form of a sinusoidal oscillation is superimposed on this squeeze movement. The coordinated interaction of vibration frequency, amplitude, squeezing speed and closing force of the tamping tines determines the stabilising quality (consolidation) of the track ballast.
This principle has proven to be thoroughly reliable in countless operations all over the world. High capacity lines throughout the world are maintained using
Scientific studies and comparisons between various tamping techniques have documented impressively the high quality of the
Vibration frequency 35 Hz
Bild vergrößernStability of the longitudinal level of the track in relation to the vibration frequency
Source: Diss. TU-Graz Fischer Johann: Einfluss von Frequenz und Amplitude auf die Stabilisierung von Oberbauschotter, 1983.
Bild vergrößernDeformation of the ballast structure under dynamic load
Source: Diss. TU-Graz Fischer Johann: Einfluss von Frequenz und Amplitude auf die Stabilisierung von Oberbauschotter, 1983.
An important factor when selecting the vibration frequency can be seen in diagram 1: at frequencies up to 35 Hz and with an amplitude of 3-5 mm there is an upward force and a lasting lift, whereas it can happen with greater frequencies that the sleeper sinks down because the elasto-fluid properties of the ballast increase.
A further factor can be seen from the investigation into the durability of the tamping in relation to the dynamic load. Although frequencies below 35 Hz enable a lasting lift, diagram 2 shows that only in the range of 35 Hz is there a minimum of deformation of the ballast. Therefore, the greatest stability of the longitudinal level achieved by tamping is found here. Furthermore, low vibration frequencies make it unnecessarily hard for the tamping tines to penetrate the ballast.
Non-synchronous constant pressure tamping principle
The squeeze pressure of all tamping units is equally large, independent of the path covered by the tines. Thus producing non-synchronous movements of the tines. This guarantees a homogeneously compacted ballast bed even under difficult tamping conditions.
Directional, linear vibration
The ideal range for the vibration amplitude lies between 3 and 5 mm. Larger amplitudes would raise the stress on the ballast, smaller amplitudes reduce the consolidating effect.
The values chosen specifically by
The Plasser & Theurer Tamping Units - Proven and Reliable
Tamping units are those components of a levelling, lining and tamping machine subjected to the highest stress. The operating reliability of the tamping units is therefore a major factor for cost-efficient maintenance of the track. The well-known and repeatedly proven reliability of the
Single-sleeper tamping unit
Bild vergrößernSingle-sleeper tamping unit
This "classic" tamping unit is equipped with eight tamping tines arranged in pairs which produce a new sleeper bearing surface at each rail-sleeper intersection.
Duomatic (two-sleeper) tamping unit
Bild vergrößernDuomatic tamping unit
The Duomatic tamping unit is equipped with a total of 16 tamping tines arranged in pairs. These go into action at each penetration to tamp two sleepers simultaneously.
Three-sleeper tamping unit
Bild vergrößernThree-sleeper tamping unit
This tamping unit is able to tamp three sleepers per tamping cycle. The tamping unit is divided into sections so that it is possible to switch over to single sleeper tamping at any time.
Switch tamping unit
Bild vergrößernSwitch tamping unit
This unit has four side tilting tamping tines. By additional lateral displacement of the tamping units in the machine frame, it is possible to tamp the entire switch, including the frog area. Connecting track or station tracks can also be tamped.
Universal tamping unit
Bild vergrößernUniversal tamping unit
The universal tamping unit has a total of eight tamping tines, arranged in pairs and individually tiltable. This unit is excellently suited for tamping work on plain line track as well as for the complete treatment of switches and crossings.
Split-head technology
Bild vergrößernSplit head tamping unit
Split head tamping units for work on switches, crossings and plain track are in principle tamping units divided in longitudinal direction of the machine. Each of the two halves of the unit can be lowered and put into action separately from the other. Additionally, both halves of the unit, depending on the design, can be laterally displaced together or individually. For operation on sections of plain track the two halves are locked together to form a plain line tamping unit.
Almost all types of
Tamping units for special applications
The proven
Individual positioning of the tamping units enables tracks with special sleeper designs, such as Y-type sleepers, to be tamped.