AB 600-2 Extending Screed with New TP2 Plus Compacting System
Leading Screed Technology: Made by VÖGELE
Paving asphalt layers with high precompaction values is crucial for long lasting traffic surfaces resistant to deformation. VÖGELE have been foremost in this field for decades now, thanks to their expertise in High Compaction Technology based on pulsed-flow hydraulics.
However, there’s a great deal more to leading screed technology than this alone. If high-quality results are to be achieved, it is also important that the hydraulic extension of the screed is absolutely smooth and jerk-free when paving across varying widths. And in this respect, the VÖGELE Extending Screeds equipped with high-quality telescoping systems are unparalleled.
The new
AB 600-2 Extending Screed in TP2 Plus version represents the ultimate in VÖGELE Screed Technology. Originally developed for the VÖGELE “hot on hot”
InLine Pave® process, this heavy-duty High Compaction Screed brings its strengths to bear in many other applications, too, where high precompaction is to be achieved by the paver.
RoadNews 19 presents the design-related principles of VÖGELE High Compaction Technology and the telescoping system incorporated in the new high-tech product, and highlights the many advantages of the new
AB 600-2 Extending Screed in TP2 Plus version.
The Highlights of VÖGELE High Compaction Technology
VÖGELE have always set the standards when it comes to compaction: cutting-edge technology combined with the most advanced materials guarantee the outstanding performance and reliability of VÖGELE high compaction products. This technology is based on the development of pressure bars operated by pulsed-flow hydraulics, an innovation that still remains unique to this day.
In combination with other compaction systems, i.e. tamper and vibrators, the VÖGELE technology yields the highest compaction values ever. This article explains the functionality of the individual systems and the various options for set-up.
Tamper
The tamper packs the mix under the screed, ensuring controlled material feed in all paving situations. The optimal tamper setting is critical in ensuring that sufficient mix is always available under the screed as required for the specified layer thickness and pave speed. This is why, in VÖGELE screeds, the tamper speed can be adjusted. In High Compaction Screeds, the length of the tamper stroke can be varied as well.
Vibrators
The eccentric vibrators, causing the screed plate to vibrate, provide for optimum grain size distribution and produce a uniform and close-textured surface structure. Just as the tamper, the vibrating intensity, too, is infinitely variable through the speed of the vibrators’ eccentric shaft - from the operator's consoles.
Pressure Bars
The pressure bars located in the rear area of the screed are crucial for high-compaction paving with VÖGELE screeds. With the screed versions TP1 (tamper and 1 pressure bar), TP2 (tamper and 2 pressure bars) and TP2 Plus, VÖGELE products lead the world in terms of compaction values.
In contrast to the beating tamper bar, the pressure bars are in permanent contact with the pavement. While paving, the pressure bars force the mix down until it cannot be compressed any further. An equilibrium of forces is thus reached between the pressure bars on the one hand and the compacted mix on the other.
To achieve the high degree of final density, the pressure bars’ action is based on pulsed-flow hydraulics. The pressure can be adjusted separately for each pressure bar between 40 and 120 bar by flow-rate controller.
To put it more simply: the thicker the layer and the more difficult the mix is to compress, the higher the pressure that needs to be selected for the pressure bars. Even thick layers can be placed in one pass, achieving a high degree of precompaction. Thanks to infinitely variable pressure control, surface course can also be compacted without shattering the grains.
Switching off the pressure bars at the push of a button
High Compaction Screeds can also be used for paving surface course. Whenever use of the tamper alone is advisable, the pressure bars can be simply deactivated at the push of a button on the ErgoPlus® paver operator’s console (push F6 button to access the menu for pressure bars, then F4 for “Off”). In this way, the same screed can be used both for placing base and binder courses and for paving surface course.
Precision and Quality: The Unique Telescoping System of VÖGELE Extending Screeds
Of course, compaction is not the only important criterion a modern screed has to fulfil. There is one task screeds always have to cope with in the most diverse paving situations and using a wide variety of mixes: precise paving, regardless of pave width or layer thickness. This is why precision and quality are key concerns of VÖGELE in both development and production of their products. The results are Extending Screeds featuring high variability in paving and superb stability across all pave widths.
For screed width control, two hydraulic rams are provided, operated very precisely from the ErgoPlus® consoles.
The large telescoping tubes keep the hydraulically extending units securely in place. Even with the screed set to its maximum width, the three individual tubes of the telescoping system are extended by no more than half their lengths. Supporting each tube over this large span effectively counteracts the vertical forces exerted on the screed by the mix.
In the horizontal direction, too, the hydraulically extending units of the screed are subjected to enormous pressure exerted by the mix. This would usually cause the extending unit to rotate on the telescoping tube. VÖGELE utilize a sliding restraint system to counteract the forces exerted by the mix, holding the screed securely in place.
Smooth extension and retraction of the telescopic tubes, without jamming or jerking, is essential to impeccable paving quality, especially when frequent changes in screed width are required. This is why the telescoping tubes in VÖGELE Extending Screeds are protected against dirt and damage, feature a very smooth surface and are provided with non-wearing teflon tapes inside the tubes for jerk-free screed width control.
AB 500-2 and AB 600-2, the two large VÖGELE Extending Screeds, can double their basic widths by hydraulic extension. VÖGELE achieve this high variability, while still retaining maximum stability, by means of an additional guide tube joined to the extending unit with a linear sliding bearing.
Thanks to sufficient overlapping at the critical transition point between the basic screed and the hydraulically extending unit, no mix is left uncompacted behind the screed. This produces an excellent paving result across the entire pave width.
AB 600-2 TP2 Plus Extending Screed: Redefining High Compaction Technology
For the market launch of the InLine Pave® technique, VÖGELE High Compaction Technology has been developed further. This was because the “hot on hot” paving process requires the paver to compact the binder course to such a high degree that compaction values in excess of 98% are achieved without the use of rollers.
Handles also conventional paving jobs
The heart of the "hot on hot" paving process is the
AB 600-2 TP2 Plus Extending Screed. This High Compaction Screed can also be used for non-IP applications when highest compacting effort is required, e.g. for placing bituminous or non-bituminous base course mixes or paving binder course.
VÖGELE High Compaction Technology in top form
The guarantee for this well-proven and extremely high compaction performance is the unique VÖGELE High Compaction Technology (see RoadNews 15, special edition on InLine Pave®). The
AB 600-2 TP2 Plus has been developed to the point of perfection thanks to the wealth of expert knowledge acquired by VÖGELE engineers in the course of many years. These are some of the innovations that have been incorporated in the current technological concept: options for the tamper stroke have been modified compared to other TP2 screeds. For the screed in TP2 Plus version, the length of the tamper stroke can be set to 4, 7 and 9mm. Adjusting the tamper stroke is easy and can be managed quickly. The tamper geometry has been changed as well, so that the mix is packed under the screed in an optimal way and outstanding precompaction is achieved by the tamper. Two pressure bars located in the rear area of the new VÖGELE Extending Screed provide plenty of power. The pressure for the pressure bars is infinitely variable within the range of 40 and 120 bar. This is a pressure specifically tailored to the requirements of both the material and the job site.
High precompaction for maximum evenness
As to paving, the VÖGELE high compaction system offers a host of advantages. Achieving a high degree of precompaction of the binder course by the paver is an important basis for the evenness of roads. Especially when paving thick layers, high precompaction prevents material accumulating in front of the roller drums during subsequent compaction by rolling, with a very positive effect upon a pavement’s evenness.
Base course placed in a single pass
VÖGELE High Compaction Technology also offers new perspectives when paving thick layers. With the
AB 600-2 in TP2 version, it is possible to place base course in a single pass. The advantage is clear: placing just one layer instead of two saves both time and money. A precondition, however, is good job site logistics, for as a function of layer thickness and pave width and depending on the length of the job site, large quantities of mix are required.
AB 600-2 TP2 Plus handles maximum pave width of 8.5m
The
AB 600-2 Extending Screed in TP2 Plus version is ideal for placing binder course, asphalt base course and others, such as crushed-stone base or anti-freeze layer – with a high degree of precompaction. The screed combines with the VÖGELE
SUPER 1900-2 and
SUPER 2100-2 pavers, as well as
SUPER 3000-2, the newcomer. Equipped with 2 x 1.25m bolt-on extensions, the screed handles a maximum pave width of 8.5m.
“We examined the paving results of VÖGELE High Compaction Technology by the example of “hot on hot” projects handled with the InLine Pave® train. The material tests showed that compaction values of 98% and more were achieved, without rolling. This figure verifies that the binder course features superb stability and a high resistance to deformation."
Prof Kurt Schellenberg,
Managing Director of the Institut für Materialprüfung
Dr Schellenberg Rottweil GmbH, Germany.
AB 600-2 Extending Screed in TP2 Plus version, representing the ultimate in VÖGELE High Compaction Technology. The modified tamper geometry and the long tamper stroke of 9mm make it possible to place base course in a single pass.
