Metric Ton Toy
The LR 11000 is the third-largest crawler crane offered by manufacturer Liebherr and is deployed whenever exceptionally heavy loads of up to 1,000 metric tons need to be lifted up to dizzy heights. On behalf of crane specialist Wiesbauer, Head of the Crane Department TIMO STARK carried out a routine inspection on one of these colossal steel structures at a wind farm by the A81 expressway.
The roughly ten-centimeter-thick sheet steel links of the crawler chassis can be heard clunking and clanking as the transmission, supported by 680 hp, hauls the roughly 600 metric ton unladen weight of the Liebherr LR 11000. This gargantuan crane slowly maneuvers back and forth on a wooden ramp until it is in the correct position to pick up a further 400 metric tons of rear suspended ballast, in addition to the 70 metric tons already loaded. This ballast is needed as a counterweight to the 168-meter-long boom (with bob) that is being set down for disassembly.
Balancing Masterclass
The maneuver takes roughly an hour, as crane driver Sylvio Hieronymus carefully lowers the steel boom, which sags at least three feet on its own weight. An on-board computer program helps him achieve the precise equilibrium between suspended ballast and boom
Finally, the yellow steel-frame structure, weighing some 215 metric tons, is resting on supports in a cornfield near Tauberbischofsheim. There is a good reason why this mammoth Liebherr crane has such huge dimensions: it was used in the assembly of the rotor blades of a roughly 160-meter-tall wind turbine at the Lauda-Heckfeld II wind farm, which is located next to the A81 expressway by Tauberbischofsheim. There are only a handful of cranes in the world that are large and powerful enough to handle this kind of job.
The Utmost Precision
The work of crane expert Timo Stark, who is based at the Stuttgart branch, began even before the disassembly of the boom: a routine inspection pursuant to Sect. 26 of DGUV Regulation 52 (BGV D6) and the German Occupational Safety Directive (BetrSichV) is mandated every four years to ensure the safety of such heavy-duty lifting equipment. The inspection usually lasts two days and starts with a complete examination of the bolts holding the individual crane components in place. These must all be present and securely fastened. Timo Stark starts from the two crawler chassis and works upward to the rotating platform. The driver’s cabin is also at this height of about five meters.
While the wind is biting on this cold March day, crane driver Sylvio’s workplace is warm and cozy. He can track the crane’s activities on three computer screens and move it into the various positions. Four foot pedals enable him to operate the two crawler chassis, the thrust of the eight-cylinder engine, and the rotating platform with rope winches.
A Marvel Weighing Tonnes
The 32-millimeter-thick steel hoisting ropes are the key components of this Liebherr crawler crane, as they carry the entire load via winches and pulleys. With this in mind, DEKRA inspector Timo Stark subjects them to an extremely close inspection, caliper in hand. “Does the crane have the right ropes of the right kind? What condition are they in? Is the specified thickness correct? These are the points I have to check,” he explains.
The next step is to inspect the load torque limit, which means that the crane has to lift a test weight of eleven metric tons with the boom attached, and carry this weight 52 meters forward. It is worth pointing out that the crane’s hook alone (known as the “hook block”) has an unladen weight of twelve metric tons. The rope itself also weighs seven metric tons. Once the maximum load threshold is reached, it is imperative that the crane’s safety mechanism kicks in and stops the crane. This is indicated acoustically via a horn signal in and on the outside of the cabin, and visually by means of a flashing light.
Basically, it’s a combination of simple physics and technical mechanics. But it’s the dimensions that often take your breath away.
Timo Stark DEKRA crane expert
Crane Passed the Test
Timo Stark, who is now also in the cabin, notes that this safety mechanism has passed the test. He is highly committed to his work: “Basically, it’s a combination of simple physics and technical mechanics. But it’s the dimensions that often take your breath away. My friends are jealous of the fact that I get to inspect such mammoth toys for grown-ups. They say I should pay for the privilege!”
Labor of Love
The 49-year-old’s passion for his field is very much apparent as he moves nimbly across the crane boom in his specially made “DEKRA crane expert” jacket, communicates with the crane driver via walkie-talkie, and writes his inspection report in his self-assembled office in the trunk of his Ford Tourneo Custom. He always displays 100 percent focus.
A clear understanding of roles
Although Stark usually adopts the friendly demeanor found on construction sites, he sometimes also has to speak plainly in his role as a DEKRA expert: “There are times when I identify defects, which I then have to raise. While I do not have legal powers to shut down a crane completely, I can, of course, refuse to grant approval if, for example, the safety mechanism doesn’t work, attachment bolts are missing, support parts are corroded, or welded eams are porous. There have even been situations where a customer has been so frustrated that they have ordered me to leave the site,” recalls the 49-year-old. He does add that such instances are rare.
The Green Light
His final act of the day is to inspect the boom, which is resting on wooden beams. Attached to a steel harness in accordance with regulations, Timo Stark proceeds meter for meter, looking for signs of corrosion, inspecting welded seams, and checking screw connections. Ultimately, the DEKRA expert is able to give his seal of approval; the LR 11000 is in excellent condition. There is nothing standing in the way of its next assignment at the wind farm.