Hamm has introduced the new HD+ 90i PH tandem roller with a hybrid powertrain.
Through the HD+ 90i PH, Hamm is combining a conventional internal combustion engine with a hydraulic accumulator: the diesel engine covers the base load while the hydraulic accumulator meets peak loads.
Hybrid solutions combine different technologies in a single system. For cars, a hybrid generally means an internal combustion engine and an electric motor.
For the Hamm roller, the manufacturer has combined an internal combustion engine with a hydraulic system for the tandem roller. The combination means Hamm is the first roller manufacturer to develop a series production-ready machine, the 9 tonne HD+ 90i PH.
Smaller engine, maximum performance
The concept is based on the realization that although maximum load is regularly required while compacting, it is always for a few seconds at a time. This typically occurs when starting up or activating the vibration or oscillation. All other compaction tasks call for significantly less power.
This is why Hamm 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 like a pumped storage powerstation: as soon as power demand falls below the maximum load of the combustion engine, a pump fills the hydraulic accumulator.
If a lot of power is called for, the hydraulic system functions as an auxiliary drive, and is able to supply a maximum short-term load of up to 20 kW. Following this, the cycle begins refilling the accumulator. The principle functions well as the maximum power is usually required for a matter of seconds. Afterwards there is sufficient time to replenish the accumulator.
As well, two other components of the HD+ 90i PH also help to ease the load on the diesel engine: an optimized electric fan drive and an efficient start-stop system. This means that for the HD+ 90i PH, a 55.4 kW engine provides enough power, instead of the 85 kW unit in the conventional version.
In 2017, the 9 tonne hybrid powertrain roller was put through its paces on numerous construction sites the length and breadth of Europe. Handling and maintenance are simplified for example, because the smaller engine does not require a SCR catalytic converter. In addition, the roller is quieter than its bigger-engined sibling. During testing, a German roadbuilding team reported no differences in compaction performance and quality compared to conventionally powered 9 tonne rollers. As well, the lower noise emission, thanks to the modified engine output, was praised by the roller’s first users.
Less fuel, same power
The hybrid roller was put to work with a Swedish construction company for several months in 2017, racking up more than 500 operating hours in the process. Analysis revealed two important findings: first, the roller delivered the same compaction performance as its sibling model without hybrid technology. At the same time, the Swedish company reported fuel savings of around 15 per cent.
Trials in France also yielded positive results. The French construction company Eiffage put the HD+ 90i PH to work for a number of weeks on differing sites in the south-west of France. The spectrum ranged from urban projects to the renovation of rural roads, and involved the compaction of differing asphalt types. Two experienced roller drivers put the new machine through its paces. They both agreed the reduced interior noise level made it a pleasant driving experience. Otherwise, they could not detect a difference from the 85 kW roller in respect of driving and compaction.
When it comes to performance, Eiffage was convinced by the hybrid concept, as all sites were monitored by a team from the company’s laboratory. The evaluations showed the degree of compaction on all projects was as good as the degree of compaction of the conventional HD+ 90i.
The number of standard variants of the HD+ 90i PH power hybrid roller offered by Hamm has now grown to six: with double vibration (VV), double vibration with split drum (VV-S), one oscillation and one vibrating drum (VO), one oscillation and one split vibrating drum (VO-S), as a combi roller (VT) and as a combi roller with split vibrating drum (VT-S).