New research shows impressive productivity figures using new grapple yarding systems
Harvesting on steep slopes, especially when coupled with sensitive soils, has always been expensive. The small piece volume of pulpwood and the low payloads of conventional cable yarders has made this even more expensive. A company in Sarawak, Malaysia, recently introduced grapple yarding systems into their operations in an attempt to improve productivity (and cost) and reduce the environmental impact caused by the traditional bulldozer skidder ground-based systems. The systems introduced consisted of an excavator-base un-guyed yarder equipped with new radio-controlled grapple carriages, fed by another excavator stationed on the cut-over.
The primary benefit of this system is that cycle times are very quick. The feeding of grapple infield lasts a few seconds and dropping of the load on the landing is even quicker. The line speeds of the Alpine Yarder winches are also impressive. An additional benefit is that the system avoids the need for ground-based machines to travel on the highly erodible steep slopes, where many metres of rain falls each year. The yarder and tail hold is mobile which makes rack changes quick and reduces congestion which could stop the machine from working (e.g. if the landing is full of trees). The need for chokermen and other people on the ground is also eliminated, which makes the operation much safer.
The researchers have presented the results of a long-term study conducted on 12 different teams equipped with the new technology, operating in Acacia mangium plantations. Data were collected continuously for almost 8 months and represented 555 shifts, or over 55,000 cycles—each recorded individually. Production of 63 m3 per productive machine hour was achieved, with good teams achieving even more. Machine availability was 93% per shift and machine utilisation was 63% per shift. Because of the long-term nature of the research and the multiple teams, the results are particularly robust. The next step is to carry out mechanical felling with tethered machines to remove the high-risk chainsaw felling activity.
The research was titled “A Robust Productivity Model for Grapple Yarding in Fast-Growing Tree Plantations” and was published in Forests 2017, 8(10). The authors were R Engelbrecht, A McEwan and R Spinelli. Source