Berlin-Tegel: Some 50 years ago, the “raisin bombers” landed here to bring in supplies to the occupied city of Berlin. Today, Tegel is the busiest of the three Berlin airports, handling as many as 11.5 million passengers in 2005. Airplanes usually take off and land at time intervals of between 2 and 3 minutes. As this busy traffic schedule leaves its marks on the runways, these are inspected at regular intervals. Following the 2005/2006 winter season, they have now been restored to top shape – using, amongst other things, a Wirtgen cold milling machine W 2000 that was equipped with “FCS light” and a special micro fine milling drum.
On the 3,023 m long and 60 m wide runway North, the airport operator’s staff in charge of rehabilitation and maintenance had identified 109 sections of between 2.5 m² and 295 m² in size where cracking and blistering had occurred. Such damages are usually eliminated at short notice to prevent them from propagating on the surface or in deeper layers of the runway pavement. It was, however, not possible to mill off the damaged areas at full depth in just one pass. The reason: The entire surface of the runway is coated with an anti-skid layer. This coating contains a special binder based on reactive resin and must therefore be disposed of separately as hazardous waste after milling. To avoid the disposal of large quantities of construction material as hazardous waste – and the related high costs –, the anti-skid layer of the damaged sections was removed by the Wirtgen milling machine prior to milling off the underlying “normal” asphalt at a depth of 5 cm.
A cold milling machine of the 2-m class was used to carry out this “filigree” task. Did milling contractor E. Feind from the town of Lübben use a sledgehammer to kill flies? Not at all, since this large milling machine was equipped with a special drum: a micro fine milling drum that is among the “finest” stuff currently available in the market. It is a milling drum with a tool spacing of 4 mm, and a second line of tools is additionally welded on the drum at the same tool spacing but offset by 180 degrees. A total number of 1,008 cutting tools are mounted on this piece of equipment that is impressive from both an engineering and an aesthetic point of view. The narrow tool arrangement causes the texture depth to be little more than 1 mm. As a result, a milling depth of 4 mm sufficed to safely and completely mill off the 2 to 3 mm thick anti-skid layer, removing as little of the normal asphalt as possible at the same time.
Milling contractor E. Feind fitted standard Wirtgen cutting tools type W 6 to the milling drum to carry out this work. Like all other cutting tools from Wirtgen, they are characterized by an extremely small tolerance of the tool head, thus ensuring a particularly uniform milling depth.
The micro fine milling drum is a Wirtgen product designed and manufactured for particular applications. Wirtgen develops, engineers and manufactures custom-made milling drums for special applications on a regular basis. The milling drum equipped with 1,008 cutting tools was also manufactured as part of a customer project. Milling contractor Feind normally uses the micro fine milling drum for levelling uneven pavements to improve skid resistance, or for fine milling pavements that are to be trafficked immediately after milling – in other words, wherever it is not – or not yet – intended to apply an overlay on top of the milled surface. Of prime importance for the riding quality of the fine milled surface is the shallow texture depth, which is mainly achieved by the narrow tool spacing of only 4 mm. Custom-made products like these enable milling machine users to establish themselves as service providers for selected special applications, thus achieving improved utilization of their cold milling machines at the same time.
To milling contractors like Enrico Feind, who works with a number of different series and special milling drums from the Wirtgen range, it is particularly important to be able to exchange milling drums quickly. The FCS from Wirtgen allows him to do precisely that. The system is available in several versions. The W 2000 owned by contractor Feind, for instance, is equipped with the so-called “FCS light”. With this system, workshop technicians need barely 2 hours to complete the exchange of a milling drum. This practical advantage was also brought to bear in connection with the fine milling project at Tegel Aiport, since on the day after its operation in Berlin, the same W 2000 – now equipped with a standard milling drum – milled off a damaged road pavement to the full depth of 30 cm.
While the W 2000 began its work on the new job site, another Wirtgen machine of the Feind fleet, a W 1200 F with a milling width of 1.20 m, milled off the exposed surface course at a depth of 5 cm. The milled material was loaded on trucks for subsequent recycling. Following that, the new asphalt course was paved, and the rehabilitated surface was coated with a new anti-skid layer.
In order to mill off the damaged sections, which exceeded 100 in number on the 3 km long runway, both Wirtgen milling machines had to do a lot of manoeuvring and had to be repositioned several times. Another important point was for the W 2000 with the micro fine milling drum to precisely hit the predetermined setting-in point and, in the second operating step, for the W 1200 F to precisely set in at the milling edge previously produced by the W 2000. The highly sensitive all-track steering of both machines was a valuable asset for this type of work. Features like steering the W 2000 by joystick, driving in crab mode, the simple handling of the machine during manoeuvring, and the continuously adjustable advance speed enabled the machines to be repositioned quickly and ensured precise execution of the work.
Fine milling of the total surface of almost 5,000 square metres was completed in just one working day so that milling contractor Enrico Feind complied with the tight schedule stipulated by the client. The shallow milling depth of the W 2000 micro fine milling drum further ensured that the costs of disposing of the anti-skid layer were minimized.
Michaela Adams, Mario Linnemann
Press and Public Relations
Phone: +49 2645 / 131-0
Fax: +49 2645 / 131-499
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High area performance despite 109 repositioning manoeuvres: The milling gang of contractor Feind completed an area of almost 5,000 square metres in just one day with the productive W 2000.
The thin stream of milled material from the discharge conveyor indicates a shallow milling depth. In this case, the shallow milling depth was worth hard cash, as it enabled the contractor to remove the complete anti-skid layer while keeping the volume of hazardous waste as low as possible.
The micro fine milling drum with a working width of 2 m is fitted with 1,008 cutting tools. The milling drum has a tool spacing of merely 4 mm, enabling it to produce surfaces at an extremely shallow texture depth and with a fine surface texture.
On the smaller ones among the more than 100 partial sections, the contaminated milled material was not loaded on trucks but was left on the ground to be swept up manually by a sweeper and then deposited in containers.
The surface milled with the micro fine milling drum (right) has a very shallow texture depth and an extremely fine surface texture. These are ideal properties if the volume of material to be removed is to be kept low. They are also ideal if the milled surface is to be trafficked again immediately after milling.