HAMM 322 – the climbing specialist

Water for Yinchuan

In Yinchuan, the capital of Ningxia province in the north of China, a huge water reservoir, the Xixia reservoir, was built in 2019. It is located in the first flood discharge area of Huangyangtan Farm, Ningxia and is a part of the water supply system of the Yinchuan metropolitan area. The reservoir is surrounded by three dikes, has a maximum capacity of 18.2 million cubic meters and a water area of approx. 2 square kilometers. The water in the reservoir will supply the newly built southern Yinchuan Waterworks and the Helanshan Waterworks. Once completed, it will be used for desilting the sediments and regulating water storage for residents in three districts and two counties of Yinchuan City. After the completion of the whole project in 2020, more than 2.6 million urban and rural people will benefit from it.

Slope, safety and time were major challenges

On a dam project, thorough compaction of the mineral aggregates is a prerequisite for withstanding the pressure of the water behind it. Any problem with the quality of the dam body may cause a leak, threatening the lives and property of the surrounding residents. In the Yinchuan project, it was quite a task to compact the dam, which consists of a mix of clay, rock and sand from local sources: it is 18 m high, with an incline of at least 35%, so the resulting inside surface of the dam is 54 m long. Given the 5.6 km circumference of the reservoir, a total area of some 302,400 square metres required compaction.

Besides compaction quality, the other factor with an impact on occupational safety is the incline of at least 35%. Using construction machinery to work on a slope like this inevitably entails potential safety risks such as rollover or slipping which may harm machine operators and other job site staff. After investigating the performance of different types of soil compactors, the project manager selected Ningxia Zhongyuantong Construction Machinery Rental Co., Ltd., a rental and construction company which has several HAMM 322 high-performance compactors in its machine fleet. In addition to performance, the HAMM 322 also provides a high level of safety because it is a fully hydraulically-driven compactor: it can completely self-lock by braking, eliminating the phenomenon of slipping on the slope and thus avoiding potential safety hazards.

Powerful drive system

On this project, semi-hydraulic compactors were not considered a qualifying machine option, as their climbing capacity is limited to a 30% incline – and that‘s before compaction has even been mentioned. The HAMM 322, meanwhile is fully hydraulically driven and its powerful drive system features an original Rexroth hydraulics system with hydraulic flow divider – a special feature for the Chinese market. Self-locking differential guarantees excellent climbing ability, allowing HAMM compactors to impress with their gradeability of up to 50% on soft soil. In fact, the high performance of the HAMM 322 compactor working on the slope totally convinced both the contractors and the project managers.

Scaling incline and compacting effortlessly

The contractor was highly satisfied with the compaction efficiency of the HAMM 322, as well as with its climbing ability. One reason for its efficiency is its engine, with a rated output of 164 kW which delivers plenty of power to ensure a sustainable and stable amplitude output when compacting along such steep slopes. Its static linear load of 62.4 kg/cm is every bit as impressive as its centrifugal force of 331 kN. This power feature leads to a high compaction performance. While compacting the final layer on the slope, for example, the HAMM 322 worked 6 hours a day at a compaction speed of 3 km/h. Compacting the dam with two passes in low amplitude mode, it completed 9,000 m² per day. The contractor used two HAMM 322 units for this project and this compaction performance made it possible to complete final compaction in the short time frame available at the end of the project without compromising on quality.

Highly cost efficient

If we take a closer look at operating costs, the contractor is also satisfied with the HAMM 322 in this regard. Ma Zhongyong, General Manager of Ningxia Zhongyuantong Construction Machinery Rental Co.,Ltd., mentioned on the job site that: “In terms of operational efficiency, one HAMM 322 can completely replace two semi-hydraulic single-drum rollers. This reduces labour costs (operator wages), fuel consumption and machine depreciation to 50%, as only half the number of machines is needed. The total cost saving is obvious and improves our return. What is more, WIRTGEN CHINA and its local dealer provide reliable customer support which gives us the confidence to handle the project.”