Tower Crane Virtual Conference: Fibre Cranes26 March 2021
Philipp Weckerle, head of product management at Liebherr Tower Cranes delivered a presentation on the company’s Fibre Cranes.
He initially talked about the history of fibre rope, mentioning the Hemp ropes developed 100 years ago. “While they were severely limited in their lifting capacity, they had some big advantages in comparison to conventional steel ropes. For example in weight and handling, because of their great flexibility.”
Weckerle said Liebherr’s motivation was to develop a rope with the maximum advantages and benefits of both hemp and steel ropes as well as one with a significantly long service lifetime. The manufacturer cooperated with Teufelberger for the development of the rope.
“The outcome is our fibre rope concept. It is 80% lighter than steel rope, it is significantly more durable in use and it is more flexible due to the core structure.”
The inner core is made of high strength fibre, while the outer core layer acts as a visual indicator if the rope gets damaged in operation. The outer cover is made of fibres with different service lives; it has no load bearing function and serves to identify the discard maturity. “It also protects the load bearing core from environmental influences such as dirt or dust.”
Currently Liebherr offers the fibre rope in two different capacity versions, 10t and 12t, in the range of 200-400mt. In total four cranes with fibre rope are offered: the 240 EC-B 10 Fibre, 240 EC-B 12 Fibre, 278 EC-B 12 Fibre and the 370 EC B-12 Fibre.
There are significant increases in load capacity range between fibre rope cranes and corresponding cranes with conventional steel rope, from 250kg (13%) for the 240 EC-B 10 Fibre to 600kg (27%) for the 278 EC-B 12 Fibre.
Weckerle compared the 340 EC-B 12 steel rope crane and the 370 EC B-12 Fibre. “There is a weight reduction of 240kg on the hook block and 160kg on the rope. Dead load becomes payload. We generate in total 400kg more payload that means up to 20% more load capacity over the whole load moment range in this example.”
Another advantage cited by Weckerle is that the extended service lifetime. Liebherr says for the fibre rope is up to ten years compared to 2-3 years average lifetime of a conventional steel rope.
“It is also possible to repair a fibre rope under certain circumstances if it is damaged, with the conventional steel rope this is not possible. We have a very simple repair solution that allows to repair the fibre rope in the shortest time possible without cutting it.”
Since the beginning of 2020, Liebherr has been offering training courses for technicians on the Fibre rope repair. A usual question is how does the fibre rope reacts to collisions on the construction sites. “Of course we had some usual issues such as collision with the jib of another crane under load or contact with concrete edges also under load. Overall 11 rope damages have been reported to us over the past years due to the special fibre rope we have been able to repair two thirds of these directly on the jobsite.”
Liebherr simulated on a test bench some possible influences on the fibre rope during the development phase. One was contact with concrete edges, simulating light striking and heavy striking both under load. It found that with light striking even after 19,000 lifts the rope was still not ready to be discarded, for heavy stiking discard maturity was reached after 220 lifts.
Deliveries of the Fibre Cranes started on the January 1, 2020. Analysing the sales split between steel rope cranes and fibre cranes in 2020, Weckerle said: “About 50% of customers realised the great advantages and benefits of the fibre rope and decided to go with the Fibre Crane. A great result for our first year on the market. There is a bigger shift for Fibre Cranes as crane size increases. The largest Fibre Crane populations are in Europe, Australia and New Zealand.”