Job Report Cold Milling

Top job in motorway rehabilitationWirtgen milling machines on the A99

Wirtgen cold milling:

Top job in motorway rehabilitationWirtgen high-performance milling machines on the A99

The “approach lane” towards the Austrian cities of Salzburg

and Innsbruck – the A99 motorway east of Munich – under-

went extensive rehabilitation over a length of 4.15 km just

in time for the European Football Championship 2008

hosted by Austria and Switzerland. First of all, an impres-

sive 70,000 m2 of asphalt pavement and hydraulically bound

base layer needed to be removed by milling – in just 4 days.

The most powerful cold milling machines available in the

market – the W 2200 and W 2100 high-performance

machines from Wirtgen – were called for to complete this

highly demanding job reliably and on time.

High-performance milling machines in non-stop operation

First of all, the 26 cm thick asphalt package (i.e. just under

18,000 m3 of asphalt material) needed to be removed over

the entire stretch of the motorway. In addition, the specifica-

tions called for the removal of around 13,500 m3 of hydrauli-

cally bound base layer. Around 30,000 m2 of the base layer

material needed to be removed at a depth of 15 to 20 cm,

while the remaining area was to be milled at a depth of

only 10 cm. Because of the consistently high prices of raw

materials and oil, both the granulated asphalt material and

the hydraulically bound base layer are valuable, recyclable

construction materials.

That was one of the reasons for milling and loading the vari-

ous asphalt layers of different quality, as well as the hydrauli-

cally bound base layer in separate operations. Maintaining

the exact milling depth and thus ensuring a clean separation

of the different construction materials was no problem at all

for the Wirtgen high-precision automatic levelling system.

Removal of the around 18,000 m3 of asphalt and 13,500 m3

of hydraulically bound base layer needed to be completed in

just under 100 hours. This led the contracting companies to

use Wirtgen W 2200 and W 2100 high-performance cold

milling machines for carrying out the job. 55 trucks were in

operation around the clock during the four days and nights

to ensure transport of the tremendous amounts of milled

material from site.

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Use high-performance milling machines economicallyHigh-performance milling machines are the

most economical machines when it comes to

milling large areas on motorways, airports or in-

dustrial estates, and where continuous and un-

hindered operation of the machines is ensured.

Especially in countries where wages and fuel

prices are high, using such high-performance

machines is the more economical solution for

construction volumes from as little as 1,500 m3

upwards when removing the pavement at full

depth, or from 40,000 m2 upwards when re-

moving the surface course. In such projects,

the use of smaller milling machines can in-

volve higher operating costs per m3 of asphalt.

Major reasons for the economic efficiency of

high-performance milling machines include:

Reduced labour cost

Like the smaller 2-m machine, a high-performance milling machine is operated by a crew of two.

As the job is completed in less time, labour costs per m3 of milled material are reduced.

Higher milling performance at reduced diesel consumptionPutting diesel consumption into relation with milling performance shows that the high-performance machines areeconomical in terms of fuel consumption. Analyses have shown that they consume less diesel per cubic metre ofmilled material than smaller cold milling machines.

Less costs for wear parts

High-performance milling machines need a significantly smaller number of point-attack cutting tools than medium-

class machines. This is due to higher advance speeds, which produce less abrasion at the point-attack tool per cubic

metre of milled material.

High engine power ensures high advance speeds at large milling widths, making the operation of the large machines, such as the W 2100 with 522 kW (710 PS) engine shown here, highly profitable.

High-performance milling machines from Wirtgen are particularly profitable incontinuous operation when supported by an efficient logistics system. 24-houroperation dispenses with “warm-up” times, which are always required at thebeginning of work until truck transport of the milled material is runningsmoothly. Instead, the milling operation goes on and on and on …

W 2200: The world’s most powerful cold milling machine

Using these machines enabled the project to be completed

not only within a very narrow time frame but with maximum

economic efficiency as well. Why? The high-performance

milling machines from the market leader impress with an

extremely favourable relation of costs to milling performance –

especially the W 2200, which is currently the most powerful

cold milling machine in the world. Good organization of

trucks provided, production rates of up to 200 m3 per hour

are the rule with this machine rather than the exception.

Under optimum conditions, the machine has even been able

to achieve milling outputs of more than 500 m3 per hour.

The powerful machine is a leader also in terms of environ-

mental friendliness. High-quality components and an intelli-

gent control system not only ensure high efficiency but also

Working non-stop for nearly 100 hours: Several Wirtgen W 2200 high-performance milling machines gave impressive proof of their reliabilityon the large construction site of Munich’s orbital motorway.

Site manager Ralf Böhm (left) from Stratebau GmbH made sure thatthe high-performance milling machines from Wirtgen worked underoptimum boundary conditions: “Good communication is neededbetween the many companies involved and the many differentproject sections. That’s just as important for the project’s successas machine technology.”

result in an excellent energy balance. The Wirtgen formula

reads: maximum milling power at minimum diesel consump-

tion. This was demonstrated impressively yet again on the

Bavarian motorway: On average, the cold milling machines

consumed just 0.9 litres of diesel per cubic metre of milled

material, making the high performers leaders in terms of

economy.

Economical operation by optimizing the milling depth

On the A99, site manager Ralf Böhm from Stratebau GmbH

and his milling crews demonstrated how to use the Wirtgen

flagships in the best possible and therefore most profitable

way. To complete milling of the huge area in record time, the

26 cm thick asphalt package was removed in two separate

passes. Even though this approach involved reversing of the

machines, which was very time-consuming, the overall vol-

4 // 5

Logistics – a key efficiency driverEven the most powerful cold milling machines cannot work economically when logistics are lacking. With insufficient truck

capacity, the proportion of unproductive waiting times increases, and profitability decreases accordingly. The four large

milling machines on the A99 kept as many as 55 trucks busy for 4 days and 4 nights. The tremendous performance

capacity of these powerful machines needs to be considered as early as the planning stage. They load a 4-axle truck

in significantly less than 3 minutes. In addition, they have a very high percentage of uptime – even water can be refilled

during the milling operation.

The hydraulically bound

base layer removed on

Munich’s large construction

site was used again right

away: Most of the material

was used to produce the

subgrade level for a mobile

concrete mixing plant, and

the remainder was stock-

piled and introduced into the

bottom-layer concrete later.

Filling up with water during milling helped the millingcrew on the A99 to avoid waitingtimes and ensured tremendous

production rates.

Shift change at 8 pm. Briefing takes place while the W 2100 iswaiting for a truck.

ume performance achieved per working hour was significantly

higher because the asphalt was removed at a milling speed

of 10 m/min. After that, the large machines tackled the hy-

draulically bound base layer at a working width of 2.20 m.

It was removed at a milling depth of 20 cm and an impres-

sive advance speed of 15 m/min, equalling a theoretical

volume performance of around 400 m3 per hour. The ma-

chine’s large milling speed is also the key to profitability.

Nightshift included

The narrow time frame required the cold milling machines

to work around the clock. No problem at all for the crews

of two, as bright spotlights on the Wirtgen cold milling

machines permit full visibility of the machines’ surroundings

and critical areas even at night. Backlit control panels and

Level Pro displays ensure ease of operation at the same

time.

Top service technicians on site fast

Reliable machines are of tremendous importance. In case of

an emergency, however, reliable service is no less important.

The pros from Wirtgen Augsburg took care of the construction

site on the A99 motorway. With its extensive network of

service technicians in Bavaria and Baden-Wurttemberg, the

Wirtgen Group’s subsidiary in southern Germany guarantees

that service personnel, armed with tools and spare parts,

can be on site within the shortest possible time – regardless

of the time of day or night.

“The machines on the A99 motorway were attended to by

our service technician based in Rott am Inn, not even 40 km

away from the construction site. Close proximity helps us to

ensure short response times, for we know that our cus-

tomers are working under tremendous pressure of time,”

says Ulrich Städele, service manager at Wirtgen Augsburg.

Bright spotlights at the upper end of the discharge conveyor ensure optimum illumination of the flow of milled material and of the truck’s loading edge.

6 // 7

Met the budget, adhered to deadline

And sure enough – after four days and four nights, the as-

phalt and hydraulically bound base layer had been milled off

entirely, enabling the milling crews to lash down the high-

performance milling machines on their low-loaders accord-

ing to schedule. “We have demonstrated on this project that

a professional crew, superior machine technology, good

planning and efficient site logistics enable large construction

projects to be executed with maximum efficiency,” says site

manager Böhm satisfied, summarizing the operation while

Wirtgen soil stabilizers are driven onto the construction site:

They are getting ready for recycling the hydraulically bound

base layer …

A clear operating concept enables machine operators to remain focused on their work even over 12-hour shifts during the evening or night hours.

Most powerful cold milling machine in the world: The Wirtgen W 2200 high-performance milling machine is best-in-class, offering a maximum milling performance of over 500 m3/h.

Increasing productivity by optimizing the milling operation26 cm of asphalt needed to be milled off on

the A99. The W 2200 and W 2100 machines

completed the job in two passes of 12 cm

and 14 cm each, even though the Wirtgen

high-performance machines can easily mill up

to 32 cm and 35 cm deep respectively.

Site manager Ralf Böhm explains the decision:

“The layer thickness of the asphalt package as

such is not a challenge at all for the powerful

machines. But large milling depths result in

considerably reduced advance speeds, in-

creased friction at the cutting tools, and thus

fairly high wear and tear. Working in two passes

and milling off the surface course and binder

course first offers the advantage that the pave-

ment comes off much more easily at the seam

between the binder and base course layers,

thus offering much less resistance to the cutting

tools. In addition to that, the mixing plants

prefer to receive granulated asphalt separated

according to quality.

Optimizing the milling depth results in reduced cutting tool wear and tear, which also means less time needed for tool replacement and more uptime for the milling operation.

Profitable high-performance milling machines: The W 2200 is repositioned extremely quickly despite its impressive size and operatingweight. The secret is in the machine’s precise all-wheel steering, clear-cut operator’s platform and user-friendly operating concept.

8 // 9

And what’s equally important: The large

milling machines from Wirtgen achieve

their maximum milling power at milling

depths of between 8 and 15 cm. Due to

their powerful engines, this course of

action enables us to make headway

really fast. All things considered, we will

have completed the job more quickly

and will save diesel and cutting tools

despite the need for repositioning more

often and a higher total mileage.”

The milling profiles of the cutting tools and therefore the chipsizes of the milled material vary significantly at different millingdepths. When the specified milling depth exceeds 200 mm, it canindeed be worthwhile to mill in several machine passes.

The milling depth selected has an immediate effect on the milling performance and on the wear of tools and toolholders. At a milling depth of 100 to 150 mm, Wirtgen large millingmachines achieve the highest volume output of milled material at the lowest costs of wear and tear.

Milling depth 50 mm

Milling depth 150 mm

Milling depth 300 mm

Tool

pat

h in

mm

per

cut

Theo

retic

al m

illin

g vo

lum

e in

m3 /

h

Milling depth in mm

Path of the tool in mm per cut

Theoretical milling volume(bulk material) in m3/h

Reaching the goal in three steps: The surface of the hydraulically bound base layer can be seen in the foreground,while half of the asphalt pavement has been milled off in the central carriagewaysection, and in the background, the asphalt package is as yet untouched.

Carriageway closure and tight schedule minimize traffic disruptionsUsed by around 110,000 vehicles

per day, the A99 motorway

leading from Munich towards

Salzburg is one of the most

heavily trafficked roads in all of

Germany. Between the junction

at Hohenbrunn and the München-

Süd intersection, the 3-lane and

4-lane asphalt carriageway was

“finished”, as a representative

of the Hohenbrunn motorway

maintenance depot put it.

To keep the duration of traffic dis-

ruptions caused by the rehabilita-

tion of the 4.15 km long section

as short as possible, the motor-

way authority for southern

Bavaria decided to close the

entire carriageway to traffic.

The time schedule was corre-

spondingly ambitious: The upper

pavement layers were removed,

the frost blanket was recycled,

and an asphalt base layer and

concrete surface course were

placed in just two months. A

huge program with tight dead-

lines that posed a challenge to all

of the various project sections.

Incidentally, powerful machines

from the Wirtgen Group were part

of the team also in the remaining

project phases: In addition to the

milling machines, soil stabilizers

from Wirtgen, asphalt pavers

from Vögele and rollers from

Hamm were in operation on the

project as well. Full closure of the carriageway gave cold milling machines and trucks the room they neededfor milling and manoeuvring and for unimpeded transport of the milled material from site.

10 // 11

Coming out for the final round: After three days of non-stop operation, the large milling machines begin removing the hydraulicallybound base layer at a depth of 20 cm. 671 kW (913 PS) enable the W 2200 to complete the job quickly at 15 metres per minute or 200 m3 of milled material per hour.

Illustrations are non-binding and may include customized fittings. Subject to technical changes. Performance data depend on operational conditions. No. 06-42 EN-08/08 © by Wirtgen GmbH 2008. Printed in Germany

Wirtgen GmbHReinhard-Wirtgen-Strasse 2 · 53578 Windhagen · GermanyPhone: +49 (0) 26 45 / 131-0 · Fax: +49 (0) 26 45 / 131-242

Internet: www.wirtgen.com · E-Mail: info@wirtgen.com