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More efficient compaction with hybrid

Hybrid drive systems make construction machinery more economical, quieter, and more environmentally friendly. In addition, a hydraulic hybrid offers highly dynamically retrievable power reserves. Bomag is presenting the new BW 174 AP tandem roller with hydraulic hybrid drive for the first time at Bauma 2019. The diesel engine, hydraulic accumulator and compaction system unite to form a highly efficient system solution. Bomag customers can then combine the technologies that best suit their desired application and performance class even more flexibly from a wide variety of available drive concepts.


Bomag is advancing alternative drive technology in construction machinery with an innovative hydraulic hybrid drive system for its new tandem roller: The company presents the BW 174 AP Hybrid for the first time at Bauma 2019 (booth: FS 1009); the machine will be available from April 2019. The highly efficient drive unit consists of a modern diesel engine, a hydraulic accumulator and the Asphalt Manager. The hydraulic accumulator covers short-term peak loads, which occur e.g. when vibration is activated. This makes it possible to use a more compact motor and operate it at its best efficiency. In this way, the hybrid solution protects the environment and saves costs: fuel consumption and CO2 emissions are reduced by up to 20 percent. The BW 174 AP hybrid drives and compacts just as powerfully as operators are used to from the tried and tested sister tandem rollers with a conventional drive.

The motors of conventional rollers are usually designed to handle peak loads. However, this high power is only required for a short time, for example when switching on vibration or for acceleration. The flip side of the coin is: for the rest of the time, the motor runs at partial-load operation, which is less energy-efficient.

Hybrid: Lower fuel consumption with the same performance

With Bomag's innovative hybrid solution, everything is different: the engine only covers the base load. It consumes much less fuel in this load range. The optimised engine size means less heat loss, which increases efficiency. The modern Kubota engine with common rail injection further increases efficiency.

The new hydraulic hybrid accumulator covers peak loads. It balances up to 100 Nm and 20 kW power directly onto the crankshaft. With 75 kW, the total output corresponds to the sister machine with conventional drive system.

The storage unit is charged in overrun mode, i.e. it recovers energy instead of consuming fuel. As this only takes a few seconds, the hybrid power is immediately available again at the next vibration start. In practice, the driver doesn't register this cycle at all.

Precise control makes hybrid solution possible

The Asphalt Manager compaction system plays a pivotal role in the performance of the hybrid solution, as such systems require extremely precise control. Bomag's Asphalt Manager is the only system on the market with infinitely variable compaction force control.

The vibration can be accelerated from standstill with little energy requirement, and the desired frequency is achieved faster than with conventional vibration or oscillation systems. With the steplessly adjustable exciter, the Asphalt Manager ensures that the force required for compaction is permanently and automatically controlled. The close interlinking of the hybrid and compaction system ensures the required vibration frequency is always maintained even under the highest loads - precision that quickly pays off in high surface quality and compaction performance.

Significantly fewer passes

The exceptional compaction performance of the Asphalt Manager also contributes to environmental protection: the maximum compaction force exceeds that of conventional vibratory systems by 20 percent. In practice, this means significantly fewer passes until the required density is reached. The fact that every saved pass translates 1:1 into less fuel consumption, CO2, and noise, and wear, further underlines the efficacy of the system. In short: Bomag's new tandem roller with hybrid and intelligent compaction system sets new standards in terms of energy consumption and operating costs per ton of compacted asphalt.

Bomag's hybrid system is currently the only one to combine no fewer than three components: engine, hydraulics and Asphalt Manager. During development, the engineers benefited from their many years of experience with Ecomode - the roller's electronic brain. The Ecomode control unit processes data from various sensors and networks individual components. In addition to the engine and hydraulics, Ecomode now also steers the hybrid system. The

operation of every component with the correct setting at all times is one of the key factors to the efficiency of Bomag rollers.

International field test confirms 20 percent savings

In an extensive international field test, the alternative hybrid drive solution successfully proved more than just its readiness for practical application and reliability. Thanks to Bomag Telematic, the company's digital fleet management system, the test operations were even able to track the actual fuel savings in real time. Savings of 20 percent were confirmed in practice.

Ecological in design and functions

As you would expect, the BW 174 AP Hybrid also features the proven Ecostop idle speed cut-off, which ensures lower fuel consumption, less wear and tear, and longer value retention.

The diesel engine already meets the Tier V emissions standard. And here, too, Bomag shows that economy and ecology are by no means contradictory: with the combination of particulate filter, oxi-cat and cooled exhaust gas recirculation, the BW 174 AP Hybrid requires no additional operating fluids. Refuelling AdBlue is no longer necessary.

On request, the machine can be supplied with biodegradable, sustainably produced bio-hydraulic oil. Thanks to its well-thought-out eco-design, the BW 174 AP Hybrid is 98 percent recyclable when it finally reaches the end of its product life after many operating hours.

Source: BOMAG GmbH