Wirtgen Resurface Frankfurt/Main Airport

02 February, 2017

First published in the January 2017 issue of Quarry Management as Rapid Runway Reinstatement

Wirtgen Group technologies deliver successful runway rehabilitation project at Frankfurt/Main Airport

Fraport AG, the operators of Frankfurt Airport, renew the surface course on the runways every seven years or so. The various milling and paving tasks involved would normally be considered standard activities, were it not for the extreme time pressure and high quality requirements that arise when resurfacing the central runway at Europe’s third-largest airport. To ensure air traffic is disrupted as little as possible, work has to proceed extremely rapidly and very reliably. The general contractor on the latest resurfacing project at the airport, Heitkamp Erd- und Straßenbau GmbH, had a timeframe of only 60h to complete the paving, during which a total of 20,000 tonnes of material would need to be processed.

Wirtgen milling machines

To complete the milling work as quickly as possible, specialist planing contractors GMS Fahrbahnsanierungen GmbH put four Wirtgen large milling machines to work on the runway. With milling widths of 2.0m and 2.2m, and a total output of 3,452hp (2,600kW), these high-performance machines milled 80,000m2 of asphalt on the 2.6km long x 31m wide strip to a depth of 5cm. The milling job, including surface cleaning, was completed in 19h.

The W210i, W250i and W2200 large milling machines used on the project are specially designed for continuous high-performance output. ‘The most critical points on major projects of this kind are usually the removal of the milled material and the water supply,’ explained Klaus Kormann, site manager for GMS.

An intermediate storage facility for the milled material was set up within the airport to minimize turnaround times, whilst with regard to water support, the advantages of the Widrive machine-management system from Wirtgen were readily apparent. This system monitors and controls not only the speed of the milling drum and conveyor as a function of feed rate and milling depth, but also the water system. For example, Widrive automatically shuts off the water when the milling drum is lowered into working position or when milling stops. In addition, the water pump pressure is automatically increased or decreased depending on engine load and milling speed. According to Wirtgen, these functions significantly reduce water consumption, making the milling process much more efficient.

The W210i and W250i machines, in particular, are capable of achieving unusually high milling performance levels thanks to their two separate diesel engines. The engines are mounted in what are known as ‘silent blocks’ that isolate them from vibration and dampen noise, providing a more comfortable environment for the machine operator. At the same time, these large milling machines are also said to be very energy efficient thanks to the Widrive system.

Once the milling machines had completed their work, the surface was cleaned and an adhesive layer was applied as a base for the new asphalt layer. The asphalt paving was carried out in two night shifts between 5pm and 7am. During this period, the 35 trucks in operation on the scheme could deliver the asphalt without being held up in the usual congestion that occurs around Frankfurt Airport.

Each night, the Heitkamp crew paved 40,000m2 of runway using an aggregate-rich AC 11 D S asphalt. Axel Konrad, project manager for Fraport AG, explained why: ‘Material with a high aggregate content offers high resistance to grain break-out, which is critical for aircraft because dislodged stone particles could damage their engines. Another reason is that abraded rubber from aircraft wheels can easily be removed from this material.’

Vögele feeders and pavers

Operating under extreme time pressure, four paving trains consisting of four Vögele pavers and four feeders were used to pave the surface, together achieving rates of around 500 tonnes/h. Airport operators Fraport had stipulated the use of feeders in its invitation for bids, because the surface accuracy of the centre runway is of critical importance. ‘Feeders are ideal here because they prevent jolts and joints in the surface,’ explained Mr Konrad.

As a result, Jörg Pigorsch, Heitkamp’s senior site manager, deployed four Vögele MT3000-2i high-performance feeders at the site. These can take on an entire 25-tonne asphalt mix payload from a truck in just 60 seconds. During transfer to the paving process, transverse conical augers within the material hoppers of the Vögele PowerFeeders homogenize the mix. Colder areas along the edges are mixed with the warmer mass, while segregated edge areas as a result of truck unloading are mechanically homogenized. Infrared heating keeps the conveyor at the right temperature to prevent mix from sticking.

Following behind the feeders, the four Vögele pavers – two Super 1800-3i machines, one Super 1900-3i and one Super 2100-2i – paved the surface course ‘hot to hot’ at a width of 31m. The Super 1900-3i took on the role of lead paver. During the night shifts, in particular, the advantages of this machine’s new and intuitive ErgoPlus 3 operating concept were evident. The operator’s console has an extra-large colour display with high-resolution images that are visible even in poor lighting conditions.

Another advantage of the Super 1900-3i and Super 1800-3i machines is their material-handling capability. With these pavers, the proportional control of the conveyor and augers with continuous monitoring of the mix level ensures an optimum head of mix in front of the screed. Moreover, the auger height can be hydraulically adjusted by up to 15cm across its entire working width, including the bearing boxes and limiting plates. As a result, an optimum spread of mix is achieved, even when paving thin overlay or varying thicknesses within a single section. With their very large blades (400mm diameter), the augers ensure optimum spreading of the mix without segregation, even across large paving widths. This was a relevant factor at Frankfurt Airport, where paving widths of 7.5m and 8.0m were required.

Hamm rollers

Four Hamm DV85 rollers provided final compaction of the asphalt. According to the manufacturer, these pivot-steered machines with an operating weight of more than
9 tonnes offer very good visibility, allowing the driver to work safely and confidently at all times. From the fully glazed panoramic cabin and through the large windows in the floor, machine operator can see the entire work area and the drums. From the edge of the cabin, they also have an unobstructed view of the drum edges.

On night duty at Frankfurt Airport, the importance of good lighting was obvious. Heitkamp had equipped their Hamm machines with very bright LED working lights as well as additional lights for the drums and drum edges, to enhance safety and quality.

Another key factor in the quality of the end result is the machines’ smooth reverse function. Hamm rollers help the operator because the DV85 brakes and accelerates the drum automatically. With optimized ramps, the rollers effectively prevent lateral displacements in the asphalt and produce an exceptionally smooth surface. The high-precision pivot steering supports this process. The steering resistance changes as a function of speed to avoid jerky steering movements. Moreover, the rollers have a very large and variable track offset which, together with 1.68m wide drums, supports a maximum working width of 2.99m.

During the compaction operations, the Hamm rollers proved efficient and productive, thanks in part to the Hammtronic electronic machine-management system for monitoring engine and travel functions. It automatically adapts the drive, vibration, oscillation and engine speed to match the current operating conditions. This perfectly tuned machine control helps ensure optimum compaction quality while also reducing fuel consumption and both exhaust and noise emissions.

All-round reliability

After two days and three nights, senior site manager Jörg Pigorsch was able to report the punctual completion of the asphalt paving work to his client. ‘We again saw proof of just how reliable machines from the Wirtgen Group are,’ he said. ‘I always use machines from Wirtgen, Vögele and Hamm when time is a critical factor on a job. What’s more, their service is excellent. If a component should fail, the Wirtgen Group subsidiaries immediately provide replacement machines, spare parts or competent service technicians.’