Hydraulic components in Liebherr LTM mobile cranes
Cologne Cathedral is a constant and challenging construction site: The approximately 157-meter-high church spires, for example, can only be restored with the help of huge suspended scaffolds that have to be assembled in the middle of the city center. Such major projects at tremendous heights and with enormous loads would be inconceivable without the world’s largest LTM mobile cranes from Liebherr. The construction equipment manufacturer’s cranes with up to 9 axis are used internationally on major constructions ranging from power plants, wind turbines, stadiums and halls to bridges. To ensure that the machines can safely and reliably move and lift loads to their destination, hydraulic components have to work excellently: from the support cylinder to the ballasting cylinder to the axle blocking valve, which the specialist WEBER-HYDRAULIK from Güglingen develops and manufactures.
Liebherr all-terrain cranes (LTM) with up to 9 axis are among the largest mobile cranes in the world. They lift loads of up to 1,200 tons and reach lifting heights of up to 188 meters. By comparison, “normal or smaller” mobile cranes with 2 to 5 axis achieve lifting capacities of between 35 and 250 tons and a maximum lifting height of 111 meters. In general, both large and small models operate with the same standard hydraulic cylinders in the crane undercarriage and superstructure: outrigger, extension, suspension, steering cylinders and axle locking valve, or ballasting and pin pulling cylinders. For use in large LTM mobile cranes, however, they must be adapted in terms of design and manufacture. They have to be able to withstand the enormous load caused by high lateral forces and axle loads and release the corresponding forces.
On the one hand, it is essential to select high-quality materials that also ensure maximum safety in lightweight construction – with wall thicknesses that are as thin as possible – and which can be produced cost-effectively. On the other hand, very precise calculations and designs are carried out in close cooperation with Liebherr when designing components. The support cylinder, for example, needs a particularly large piston diameter to be able to generate the corresponding forces. For the longer extension cylinder, the greater risk of the piston rod buckling must be calculated. Steering and suspension cylinders must be designed in accordance with the high axle loads and the large continuous and peak loads. This also applies to the axle locking system, which must be able to withstand high pressures and flow rates.
Support cylinders from WEBER-HYDRAULIK with their special design and material selection as well as their specific seals ensure that the Liebherr LTM 1400-7.1 has a safe and firm footing even at its maximum lifting height of 130 meters. (Image: Liebherr)
In-house research and test station drive developments
Seals such as the piston seal of the outrigger and ballasting cylinders play a special role in giant mobile cranes, as the cylinders are among the safety-relevant components. A leakage here could have serious consequences, up to and including the tipping over of the mobile crane. “The requirements are moving more and more in the direction of extreme environmental conditions – in general and even more so for the very large machines,” says Michael Ungar, Head of the Cranes segment at WEBER-HYDRAULIK. “Today, we can cover a temperature range of at least -40°C to +80°C with special sealing technologies.” For piston rod coating, which ensures the appropriate corrosion resistance of components in extreme environments, the hydraulics specialist has developed a coating process (WNC) and conducts its own research in its electroplating. Tests and inspections are also carried out at the company, which significantly improves coordination with the customer and development times.
WEBER-HYDRAULIK develops special valves and cylinders that withstand the enormous loads in the world’s biggest mobile cranes. (Image: WEBER-HYDRAULIK)
Permanent optimization and further development of the components
WEBER-HYDRAULIK has been developing and manufacturing hydraulic products and systems for the crane industry for over 40 years. “We learn with every new project and can incorporate our many years of experience. Here, we see ourselves not only as a supplier of individual products, but also as a consultant for our customers,” says Michael Ungar. The demand to optimize components is always in the spotlight. An example of this is the reduction of power and performance requirements by minimizing the friction of guides and seals in order to reduce fuel consumption. Or further development of the cylinders with regard to additional functions: For example, the suspension cylinders of LTM mobile cranes are equipped with a double proximity switch so that the necessary end positions and the direction of movement can be detected. The axle blocking valve is equipped with sensors that provide information on its position – locked or open. To detect the positions of the cylinder, the extension cylinders today have length measuring systems on the crane side. “WEBER-HYDRAULIK is constantly working on new solutions and new measuring systems to achieve more and more flexibility and increasingly better utilization of the working area,” says Michael Ungar.