Trains Plasser and Theurer

The Safe Tamping Process

Plasser & Theurer tamping technology – The standard for maintaining tracks and turnouts

The track network is a dynamic, constantly changing system shaped by diverse influences such as rail traffic, condition of the subsoil, changes in temperature or precipitation.  

Why does track need to be tamped?

Consisting of rails, ties and ballast, tracks form an elastic system. Traffic loads subject this system to enormous dynamic forces causing the entire track to deflect and return to its original position. In the long run, these high stresses lead to deviations from the ideal track position.  If the track quality falls below a certain level, the track must be maintained. To restore the ideal track position, a tamping machine is used to level, lift, line and tamp the track. This maintenance measure aims at ensuring safe operation and, thus, the customers' satisfaction. Delays in maintenance lead to speed restrictions hindering rail traffic.

Machine quality pays off

Maintaining tracks and turnouts requires exact planning as well as top quality and maximum performance of the machines used. The higher the level of quality and, particularly, sustainability of maintenance actions, the longer the intervals between maintenance operations. Our tamping technology ensures a durable consolidation of the tie bed. High-quality mechanical components combined with high-precision hydraulics ensure the consistent quality of the work performed. Brought to perfection in further development, this principle has proven its efficiency under varied ballast conditions and in different track structures. 

Cost-efficient machines for all fields of application

Choosing the ideal tamping machine depends on the technical and economic requirements in coordination with task-orientated equipment. Over the past 60 years, we have supplied more than 8,200 tamping machines to 109 countries all around the world. The following pages provide an overview on the varied work units, optional equipment as well as measuring and control technology. This diverse offer comprises the right machine for any requirement.
Tamping machine 1
Our tamping machines correct track faults (deviations in longitudinal level and alignment) and produce a durable track bed, thus ensuring a durable track geometry.

How do tamping machines work?

The right technology is crucial to achieving the best technical and commercial results. 

Our core technology - the tamping unit - is used in diverse designs and varying sizes on all of our tamping machines. To carry out high-quality maintenance efficiently and with maximum precision a range of further equipment is required. On all of our machines, only well-proven components are used. 

These include precise and reliable measuring systems with large sized measuring wheels or highly reliable and easily maintainable steel cables used as reference cords. Work is performed using a proportional parallel levelling system with one steel cord per rail and with a single-chord lining measuring system.  

The AGGS (Automated Geometry Guiding System) computer takes over full control of the machine during operation. It supplies exact data for the precise correction of faults in longitudinal level and alignment in both track and turnouts. 

The lifting and lining units used for the exact guidance of the track structure are generally integrated in separate frames. Lining rollers, roller lifting clamps or adjustable lifting hooks ensure the safe lifting and lining operation in tracks and turnouts. 

Connecting the work units, the main frames of the machines are sturdy constructions made of high-grade steel using modern welding processes. Axle and wheel material meets high standards. Suspensions with shock absorbers ensure a high degree of running stability.

Tamping technology in detail

During tamping, the ballast under the tie is consolidated to produce a stable track bed. This controlled consolidation ensures a durable track level.

For this purpose, Plasser & Theurer developed the non-synchronous uniform pressure tamping technique. Experts regard this mechanized technique as ground-breaking and unequalled in quality. Today, we are able to offer the right technology for all ballast conditions (hard, soft, encrusted, different ballast bed materials, etc.)

Non-synchronous uniform-pressure tamping

The tamping tools penetrate the ballast bed from above to compact the ballast underneath the tie with a squeezing movement.

Three parameters are decisive here: Firstly, all tamping tools work with the same pressure. Secondly, the tamping tools vibrate with the ideal frequency of exactly 35 Hz. Thirdly, the sturdy mechanical design enables a stable amplitude of .16 - .20 inches.

We have chosen this frequency range as it produces an upward force and leads to a lasting lift. At lower frequencies, the ballast is not consolidated sufficiently. Higher frequencies cause it to flow. In this case, it is difficult to bring the flowing ballast underneath the tie to create the required longitudinal level. This directional, linear vibration combined with the non-synchronous tamping tool movement produces a homogeneously compacted ballast bed.
Tamping unit lowered into working positionTamping unit during consolidation

Optimum work parameters ensure process reliability

In addition to pressure and frequency, various other parameters influence the tamping quality:

To re-arrange the granular structure (for consolidation) not only the right force, but also the right force impulse is required. If the duration of this impulse is too short, the consolidating effect will be lower despite the higher impact force. Both long years of experience and studies have shown that the optimum consolidation time ranges from at least 0.8 seconds to 1.2 seconds. Longer consolidation times achieve no decisive further improvement. Sustainable ballast consolidation, however, also requires a stable vibration amplitude of .16 - .20 inches.

The squeeze path depends on the ballast conditions (encrusted, well-packed) and the penetration position. Usually the squeeze path is around 5 inches.

The tamping depth is of crucial importance to achieve high-quality compaction of the ballast under the tie. If the depth is insufficient, the tamping tools strike the ties. If it is too large, the track bed is compacted unevenly and incompletely.

Lifting the track with the lifting units is a further important requirement to achieve a uniformly consolidated track bed as this creates the space under the ties required to re-arrange the ballast in order to form a new consolidation structure.

Quality of the tamping tools

The tamping tools transmit the consolidation energy. They are the link between the tamping unit and the ballast. To achieve optimum tamping results the tamping tools must be in perfect condition. Worn tamping tools must be replaced once the level of wear has reached a maximum of 20%.

High-quality tamping tools allow higher outputs and have to be replaced less often. In both cases, our original tamping tools have set the standard. Their design is crucial: produced as monobloc components forged in one piece and coated with a tungsten-carbide armour for all surfaces that come into contact with the ballast, the tamping tools have a high longevity. Their specially optimised shape makes them highly resistant to wear.

Tamping units for all fields of application

Tamping units are the core components of our machines. They determine not only the function of the machine but also its productivity and cost-efficiency. The well-proven dependability and operating reliability of our tamping units contributes significantly to ensuring cost-efficient track maintenance.

More than 200 variations of tamping units are manufactured exclusively in the main factory in Linz. There is hardly any customer requirement we cannot meet. This alone shows the technological progress that has been made since the first hydraulic tamping unit was built in in the early 1950s.

Today, we offer a complete range of tamping units for all fields of track and turnout maintenance, classified according to output and performance requirements.

Choosing the right tamping technology

Equipment and design of the machine depend on the requirement profile to be met.

The required tamping performance per time unit determines the size of the tamping unit. For this purpose, a high annual output may be just as crucial as short track possessions on high-capacity lines. Cyclic action or continuous action machines with 1-tie or multiple tie tamping provide an extensive offer to choose from.

The design of the units depends on the track conditions such as tie spacings, types of tie, power rails, etc.

The field of application is yet another selection criterion. Will the machine be used to tamp tracks, turnouts or - highly universally - both? When opting for a turnout tamping machine, the type of turnout is decisive: The offer ranges from machines and units for maintaining simple, small wooden-tie turnouts, to machines and units for long, heavy high-speed turnouts with concrete ties.

Our extensive range of equipment allows a selective and individual adaptation to all requirements. All tamping machines stand out due to the sturdy construction of the frame, the undercarriage and the use of hydraulic drives for the work units. Spacious drive and work cabins and ergonomically designed operator's desks with an excellent view onto the track and working area make the machine operators' work easier while increasing quality and speed.

The key to fault correction

Every tamping machine needs integrated measuring technology to enable the correction of level and line faults in tracks and turnouts. Therefore, the standard equipment for all of our tamping machines comprises measuring systems for correcting track geometry faults in longitudinal level, cross level and longitudinal alignment: the proportional parallel levelling system and the single-chord lining measuring system. 

The sturdy mechanical design, the large measuring wheels and the comfortable operating concept ensure highest precision. Vegetation or vibrations and dust caused during operation hardly affect the accuracy of the measurements. In addition, the systems are easy to inspect and to service. On all tamping machines, the AGGS (Automated Geometry Guiding System) computer performs the comprehensive guidance of the levelling and lining systems during work. 

Within the machines, steel chords are used as reference bases. Outside the machines, laser is used as measuring base.  

Proportional parallel levelling system

In conjunction with the lifting unit of the tamping machine, the system is used to measure and correct the longitudinal and cross levels of the track. Proportional to the lifting value, electronic signals are produced via transducers for automatic control of the track lifting hydraulics. 

Two methods of work are available: the compensation method and the precision method. An optical radio direction-finder or a laser direction-finding unit can be used for optimum correction of long wave faults in the longitudinal level.

Single-chord lining measuring system

This recognizes existing alignment faults in the track geometry and reduces or eliminates them using the tamping machine's hydraulic lining unit. Depending on the operating requirements, two methods of work can be selected: the 4-point method and the 3-point method. The latter is particularly suited for the precision method.
The sturdy mechanical design of the measuring technology ensures precision despite harsh conditions on track.

Integration of other stages of work

The three major elements of the MDZ mechanized maintenance train – tamping machine, ballast regulating machine, dynamic track stabilizer – can be excellently combined in different tamping machine designs. The selective combination of separate functions brings considerable savings.

Dynamic track stabilization is an additional function that is used on both track and turnout tamping machines. A controlled initial settlement raises the track's resistance to lateral displacement and increases the stability of the track geometry. Intervals between maintenance can be extended without risking the safety of the train services.

Integrated sweeper units pick up surplus ballast, store it in the hopper and place it in the track in metered quantities wherever required. Profiling units and ploughs distribute the ballast and place it in the tamping zones. To complete the track maintenance measure, simple sweeper units thoroughly sweep the track or the turnout.

All-in-one track maintenance machines combine all maintenance work

Turnout and track maintenance machines, such as the Unimat 09-475/4S N-Dynamic, combine the functions of three machines: ballasting, tamping, profiling, stabilizing and control measuring. This simplifies work site logistics significantly and results in a high savings potential.

In one single working pass, these machines perform the complete and technologically correct work sequence for the maintenance of turnouts and tracks. Despite the variety of functions, their operation is simple and clearly structured thanks to up-to-date control engineering with menu-assisted user guidance.
Tamp Link logo

Increase your work performance!

TAMPLINK® is Plasser American’s universal interface to connect different types of Plasser American machines/equipment with a tamping machine like a GRM3000T to increase work performance and provide more flexibility. The interface includes all necessary electrical/electronic, hydraulic, pneumatic and mechanical connections. Dependent on the actual work requirements, the customer can choose between a GRM2X Tamping Trailer, PST16SW Switch/Spot Tamper or a PTS90C Stabilizer to fulfil the ordered work performance without modifications to the machine/equipment and without additional operators.

The control system automatically detects what type of machine/equipment is connected and sets up the linked machines/equipment accordingly. This enables an economical use of the machine fleet. You gain the ability to purchase the basic machine/equipment today and expand the product and service portfolio by purchasing additional equipment later.
Tamping Game

Have you ever wanted to operate a tamping machine?

Tamping Game screen
Get to know the Plasser & Theurer machines with our Tamping Game app. In different scenarios, you will encounter a variety of obstacles. Improve your skills as you try to tamp each sleeper without any mistakes. As you improve, you will collect more points and increase your personal ranking. Check online to see your current position and to compare it to other players.