HAMM HD+ 90i PH tandem roller: Environmentally friendly hybrid technology as standard

Hybrid solutions combine different technologies in a single system – in the case of cars, at the present time this generally means an internal combustion engine and an electric motor. HAMM, the innovation pioneer, has instead combined an internal combustion engine with a hydraulic system for the tandem roller. This has enabled HAMM to become the first roller manufacturer to develop a machine ready for series production – the HD+ 90i PH, which weighs 9 tonnes.

Hybrid power train: Maximum performance despite a smaller engine

The underlying concept is based on the realisation that although the maximum load is called for regularly while compacting, it is always just for a few seconds at a time. This typically occurs when starting up or activating the vibration or oscillation for example. All other compaction tasks call for significantly less power. This is the reason why HAMM has equipped the power hybrid roller with a smaller diesel engine in combination with a hydraulic accumulator to satisfy the load peaks.

The hydraulic system works rather like a pumped storage power station: As soon as the power demand falls below the maximum load of the internal combustion engine, a pump fills the hydraulic accumulator. If a lot of power is called for, the hydraulic system functions as an auxiliary drive, able to supply a maximum short-term load of up to 20 kW. Following this the cycle begins afresh with the refilling of the accumulator. The principle functions splendidly because the maximum power is usually only called up for a matter of seconds. This leaves enough time to reload the accumulators. This technology allows the roller to deliver the same power while equipped with a smaller diesel engine. With the HD+ 90i PH, two further components also relieve the burden on the diesel engine: An efficiency-optimised electric fan drive and an efficient start-stop system. This means that a 55.4 kW engine output suffices for the HD+ 90i PH, instead of the 85 kW unit in the "conventional" version.

Significantly quieter and with lower maintenance overheads

During 2017, the 9 tonne roller with power hybrid train was put through its paces on numerous construction sites the length and breadth of Europe. It proved its worth in every respect. Handling and maintenance are simplified for example, because the smaller engine does not require an SCR catalytic converter and thus no AdBlue. In addition, the roller is markedly quieter than its bigger-engined sibling. This aspect was well-received everywhere – including when compacting the binder and surface courses on the A 93 motorway in Bavaria. A STRABAG team there reported no differences in compaction performance and quality compared to conventionally powered 9 tonne rollers – but everyone praised the lower noise emission thanks to the modified engine output.

The power hybrid roller was put to work with the Swedish construction company NCC over a number of months in 2017, racking up well over 500 operating hours in the process. Analyses revealed two important findings: Firstly, the PH roller invariably delivered the same compaction performance as its sibling model without hybrid technology. At the same time, NCC reported fuel savings of around 15%. This aspect was essential for the environmentally-conscious Swedes because the reduction in diesel consumption leads to markedly lower CO2 emissions.

Proven on city and country roads

Trials in France also yielded gratifyingly positive results: The French construction company Eiffage put the HD+ 90i PH to work for a number of weeks on widely differing sites in the south-west of France. The spectrum ranged from urban projects to the renovation of rural roads involving the compaction of widely differing asphalt types. Two experienced roller drivers put the new machine through its paces. They both agreed that the reduced interior noise level made it an extremely pleasant driving experience. Otherwise they could detect no difference to the 85 kW roller in respect of driving and compaction. And when it comes to performance, the people at Eiffage are convinced by the hybrid concept: All sites were monitored by a team from the laboratory. The evaluations showed that the degree of compaction on all projects was as good as the degree of compaction for the conventional HD+ 90i.

Available in many variants

HAMM now offers the HD+ 90i PH power hybrid roller as standard in six variants – with double vibration (VV), double vibration with split drum (VV-S), an oscillation drum and a vibration drum (VO), an oscillation drum and a split vibration drum (VO-S), as a combination roller (VT) and as a combination roller with split vibration drum (VT-S).