When a large milling machine outdoes itself
Clients demand maximum milling performance in the rehabilitation of motorways, airports and other large traffic surfaces. For jobs like these, Wirtgen has developed the W 250 high-performance milling machine and XXL-size milling drum units with milling widths of up to 4.40 m. Bavarian contractor Kutter GmbH & Co. KG operates one of these extremely powerful machines, achieving top quality and maximum efficiency at the same time.
Milling under great deadline pressure has become normal, and speed of construction is an important factor of success for milling contractors. For precisely that reason, a Wirtgen cold milling machine type W 250 with 3.80 m wide, XXL-size milling drum unit has been part of the fleet operated by the milling experts from Kutter, who are based in the Southern German town of Memmingen, since the summer of 2011.
Milling instead of manoeuvring
“With the 3.80 m wide drum installed in the W 250, we significantly increase the machine’s milling performance as the drum is about 70% wider than that of the standard machine. As a result, turning and repositioning manoeuvres of the machine are also considerably reduced,” explains Roland Schmid, head of the milling division at Kutter. Bernd Holl, Product Manager Cold Milling at Wirtgen, adds: “The W 250 with 3.80 m wide milling drum efficiently translates the engine output of nearly 1,000 HP into milling power. In the United States, many of these XXL-size milling drum units have been in operation for quite a while. We are therefore all the more pleased that Kutter, our biggest customer in Germany, is now also using such a drum unit.”
Wirtgen offers the XXL-size milling drum units in several milling widths ranging from 2.50 m to 4.40 m. Kutter opted for the 3.80 m wide drum unit as “we can use it to mill off a typical German traffic lane in a single machine pass,” says Roland Schmid, adding that “the milling process is accelerated significantly when using the XXL-size machine. One reason is that there is less effort involved in coordinating operations as we need fewer machines. In addition, we save time due to the reduced number of reversing manoeuvres. This pays off in time-critical night operations or on airport sites where time is limited.”
Ideal for surface course rehabilitation and milling in layers
The giant drum units achieve optimal results when milling off layers at depths of up to 10 cm, which makes them ideal candidates for the rehabilitation of surface courses. Milling in layers is therefore the most economical method when removing asphalt pavements at full depth. In addition, it is a fast-paced process; after all, the flagship machine from Wirtgen features an engine output of 731 kW. “When removing the surface course, the machine produces an excellent milling pattern at a milling depth of 4 cm and advance speeds of around 20 m/min. With a 2.20 m wide drum unit, comparable results can only be achieved at milling speeds of well over 30 m/min but this would have an adverse effect on the quality of the milled surface,” says Product Manager Bernd Holl.
This is confirmed by Kutter’s experience: when removing the surface course of a country road in the Bavarian town of Hofstetten, an impressive advance speed of 18 m/min was measured over a distance of just under 3 km. The milling pattern and evenness produced were flawless despite the high advance speed, for the XXL-size milling machines achieve unrivalled levels of evenness due, in particular, to their tremendous milling width.
Easy handling, easy transport
Handling of the XXL-size cold milling machines is extremely straightforward. “Cameras give us an excellent view of the milling process,” says Klaus Strobl, milling machine operator in Kutter’s crew. And, as with all cold milling machines from Wirtgen, operation is exceptionally user-friendly. Finally, there is the question of how the wide machine gets to the milling site. Wirtgen offers an intelligent solution to facilitate transport: the WT 440 mounting carriage, which is used to transport the milling drum unit to the job site on a flatbed truck. When loaded with a 3.80 m wide milling drum unit, the carriage weighs around 20 tonnes, its width and height remaining below 3 m.
The machine minus drum unit has a transport weight of around 35 tonnes. For mounting, the self-propelled WT 440 is driven from the flatbed truck via remote control and is positioned underneath the machine. “Two of our staff need just under two hours to bolt the unit to the machine, connect it to the hydraulic system and install the power belt,” say the dispatchers at Kutter, relaying their experience. This solution provides them with a high level of flexibility in job site organization and machine scheduling.