Modeling Production of Longline Yarding Operations in Coastal British Columbia

Abstract Two Madil 046 skyline yarders, rigged as slackline systems and equipped with Ballenger motorized carriages, were studied by field crews from the University of British Columbia - Forest Operations Group for approximately six months at sites on the west coast of Vancouver Island in British Columbia. A continuous turn element time study, using handheld data recorders was employed to collect data throughout the study. Mean cycle times for the two operations ranged from 11.5 to 13.5 minutes per cycle. Delays contributed at least 20 percent of the cycle time for both operations and were primarily caused by carriage related problems. Average piece size differed by more than 56 percent and created significant differences in overall system productivity. While average cycle time for the two systems differed by at least two minutes, the system with the longer cycle time had higher mean production due to the larger volume per piece and per cycle. The study results strongly suggest that maximizing volume per cycle is critical to maintaining productivity and minimizing costs, even though cycle time may be increased. In this case, one system was able to capitalize on larger average piece size to significantly improve hourly production, even though cycle times for this yarder were higher. More effort is needed during operations to monitor volume (or weight) per cycle and consistently maintain the maximum volume per cycle for existing conditions.