Night shifts on the skyway
HD O120V enables quick rehabilitation
One of these elevated roads, the 48 km long Inner Ring Road, was opened for traffic in 1994. Now, after 14 years in operation, some sections needed maintenance. The Shanghai Chengji Municipal Company was awarded for this contract. As this is a highly frequented road, the work mainly had to be carried out during night time. Each night a section of approx. 1.200 sqm was to be repaired. Therefore, the road was closed from midnight until 5 a.m. As a frist step, the old wearing course was milled out by a Wirtgen W 1900 large milling machine.
For the compaction of the new wearing course paved immediately after milling, Shanghai Chengji Municipal Company decided to use a HAMM HD O120V tandem roller because this machine fulfils all requirements including the economical and environmental friendly tasks. Moreover, with an operating weight of 12.250 kg and the HAMM oscillation technology it was the perfect machine for the compaction of the new SMA 13 wearing course on the elevated road.
Oscillation allows dynamic compaction even on bridges
HAMM oscillation is the only technology that can compact dynamically even on bridges or elevated roads. In Shanghai, after only three passes the tandem roller had compacted the SMA 13 to 99.16 %. This demonstrated impressively that oscillation rollers can achieve outstanding compaction results with only a few passes. This advantageous technology is offered uniquely by HAMM. Other than vibratory rollers, HAMM oscillation rollers introduce tangential forces in the material to be compacted. During this process the horizontally moving drum rests in constant contact to the asphalt resp. soil layer. The dynamic oscillating movement in combination with the permanent static load of the drum guarantee a fast increase of compaction paired with very homogeneous compaction and good surface roughness. Thereby the substructures are hardly affected. This is why dynamic oscillation can be applied even on bridges or other structures sensitive to vibration. On the Shanghai skyway, a normal vibration roller would have had to work in static mode, without vibration. This would have needed more passes and thus more time without reaching the level of compaction achieved by the HD O120V. The saving of time and the outstanding compaction performance are two decisive application advantages offered by HAMM oscillation rollers.
HD O120V – two systems in one machine
Basically the machine is a „two in one”-roller as the front drum is equipped with vibration and the rear drum comes with HAMM oscillation. The roller is driven by a 4 cylinder Deutz diesel engine type TCD 2012 LO4 2V with a power rate of 100 kW at 2.300 rpm. A 185 l fuel tank ensures that the machine can operate at least one shift without refilling. The same fact counts for the 900 l water tank of the sprinkler system. The standard sprinkler system is pressurized and works with two pumps. An emergency system ensures sufficient water supply in any situation.The front vibration drum can reach a centrifugal force of 186 kN, the rear oscillation drum can even reach up to 279 kN. In crab steering mode, the roller with a drum width of 1.980 mm can extend its working width up to 2.090 mm. Besides the technical features also the operator is in focus of the HAMM design team. A swivelling and turning operator’s seat with two multifunction levers on the left and right hand side allows the operator a clear view on the edge of the drum.
All these features are important for a successful operation and of course for an excellent result. Furthermore, the fact that HAMM combined two dynamic systems in one roller pays off financially. Using the oscillation system, the roller components are exposed to considerably less stress and thus achieve an extended service life.
24 h service and support
However, the machine itself is not the only key to success. Mr. Hu Liping, Section Chief of Equipment Department at Shanghai Chengji Municipal Company, explains why: „It is not only the machine but also the outstanding after sales service, repair, training and application support offered by WIRTGEN CHINA that eases the operation. With the assembling, repair and service centre in Langfang (Hebei) and additional service centres in Shanghai, Guangzhou and Xi`an, support is always close to us. So WIRTGEN CHINA supports jobs like this in Shanghai with a 24 h service on site, for example. Even if usually the services of the HAMM engineers remain unused, their presence gives us the safety we need on night jobs like this where there is a strict deadline to finish work at 5 a.m. every morning. Nobody would like to imagine what happened if the Inner Ring Road could not be opened in the morning. Everyone who has been in Shanghai, knows what it means ...”