Safe and comfortable train travel is only possible on a track with the correct geometry. The first machines which could quickly and reliably create this track condition were manufactured by Plasser & Theurer. Plasser & Theurer developed the world’s most widely used, hydraulic non-synchronous constant pressure tamping principle for fixing tracks in the correct position.
In the meantime, thousands of levelling, lifting, lining, and tamping machines from Linz are operating around the world. In line with operating companies’ individual requirements, this machine portfolio provides a unique selection nowadays. For tamping machines, we mostly differentiate between machines in standard railway vehicle design for plain-line tracks or turnouts, equipped with 1-,2-,3-, or 4-sleeper tamping units; self-loading or road-rail tamping machines; and lightweight tamping machines. Machines built in special designs are also included in these categories, for example, ones that are fully soundproofed or for special tasks such as tamping Y-sleepers or remedying isolated defects. Other examples include small track radii, tight structure gauges, power rails, or various track gauges and structure gauges.
Why is tamping useful?
When a train travels over a track, enormous forces act on it. These forces cause the entire system consisting of rails, sleepers, and ballast to deflect. Its elasticity allows it to return to its original position.
Over time, this high amount of loading causes the track geometry to deteriorate. This may result in defects, i.e. the track is no longer in the ideal position and speed restrictions may be required on certain sections of the line.
To prevent this from happening in the first place, tracks must be maintained at regular intervals, i.e. levelled, lifted, lined, and tamped. Doing so restores the ideal track geometry.
How is tamping performed?
During tamping, ballast is filled and compacted under the sleeper to produce a stable sleeper bed.
Plasser & Theurer developed a mechanized technique for this purpose: non-synchronous constant pressure tamping. Regarded as ground-breaking by experts, this technique produces results of unparalleled quality. The tamping tines penetrate the ballast bed from above, filling and compacting the ballast below the sleeper with a squeezing movement. Two parameters are decisive here: the tamping tines are working at the same pressure and are vibrating at the ideal frequency of exactly 35 Hz. This directional, linear vibration combined with the non-synchronous movement of the tamping tines creates a compact, stable sleeper bed.
