Flying high: hydraulic drives for the Zoomlion QAY 2000
The world’s largest all-terrain crane uses components from Linde Hydraulics.
1200 tonnes: Until recently, this was the highest nominal load bearing capacity with which the versatile all-terrain mobile cranes had operated, both on and off the road. The eight or nine-axle machines made in Europe are predominantly used for assembling large plant systems, e.g. in the chemical industry and power plant engineering as well as for erecting wind turbines.
At bauma China 2012, this record was beaten – and quite significantly at that. Chinese construction machine and crane manufacturer Zoomlion, which is China’s second-largest manufacturer of construction machines, unveiled QAY 2000 (Image 1), its new flagship model in the all-terrain crane category. As the description states, this off-road crane weighs 96 tonnes and can bear heavy loads of up to 2000 tonnes.
The development was brought about as a result of the desire to erect larger wind turbines with an output of 3 MW or more using the more flexible AT cranes instead of the crawler cranes previously used. Since the AT cranes reach the operating site by their own means, they are more mobile. This also makes equipment assembly and dismantling times significantly shorter. Fewer accompanying vehicles are required, the amount of effort required for logistics is therefore much less and the expensive hoists are utilised in the most effective way possible.
The QAY 2000 operates on 12 axles and is driven by a 480 kW engine. In the upper carriage there is a 190 kW diesel engine that provides torque exclusively for the hydraulic drive systems. This includes the extension system for the eight-part telescopic jib, the mighty rocker cylinders and the rocker point, which is also hydraulically adjustable, as well as the cables that ultimately lift the load. In the undercarriage, the swivel mechanism and the enormous supports are moved hydraulically.
During development of the high-pressure hydraulic drive systems and selection of the central components, the Zoomlion engineers received support from Beijing Hylet Co. Ltd. – the Chinese sales and distribution partner of the Linde/Eaton alliance.
The Zoomlion QAY 2000 has a total of twelve swash plate axial piston pumps from the tried and tested 02 series. Seven variable displacement pumps from the HPV-02 series work in a closed circuit and are electrohydraulically controlled. The five other units are HPR 02-type regulating pumps that work in an open circuit in load sensing systems.
The twelve pumps supply the generated pressure to nine high pressure axial piston motors that are also from the Linde Hydraulics 02 series. In addition to the fixed displacement motors from the HMF series, electrohydraulic infinitely adjustable variable motors from the HMV series are used and incorporated into the electro-hydraulic control cycle via a speed sensor. For two of the nine hydraulic drive systems, Zoomlion uses an HMA motor. This has the special design of an “adjustable high-pressure fixed displacement motor”. It has a constant displacement that the user can change with infinite variability via a screw as required.
With the high-pressure pumps and motors from the Linde Hydraulics range, which achieve a maximum displacement of 28 to 210 cc/rev, Zoomlion has opted for tried and tested premium drive solutions that also operate extremely reliably in pure construction site settings and facilitate not only sensitive control but also particularly high performance levels. Both of these properties are indispensable for the working hydraulic systems in a high-performance crane of this kind. For Linde Hydraulics, the QAY 2000 is an excellent reference: For now, the 2000-tonne work machine is likely to remain the world’s largest and most powerful all-terrain crane for the time-being.
The QAY 2000, which was unveiled in China, is a pilot model. The company is yet to divulge when series production of Zoomlion will begin and where the cranes will be deployed. There is definitely demand for this machine: In China, the capacity for wind energy is currently being significantly expanded. Wind turbine systems with a capacity of around 75,600 megawatts were in place by the end of 2012. In 2015, the capacity should rise to 100,000 MW.