ABSTRACT

Wire rope used in cable logging, where a series of cables facilitate the extraction of timber on steep terrain, experiences high tensions that must be managed to ensure safety. Innovations change practices over time and double-hitch carriages, which allow trees to be extracted horizontally, are a recent example. This makes it feasible to harvest across terrain with limited deflection, increases the recovery of biomass, and potentially reduces high-dynamic load events associated with ground contact. In this study, a standard single-hitch carriage was compared against a new double-hitch carriage under controlled conditions. Tension was measured continuously and specific elements, such as tension when the carriage was at midspan, maximum tension at breakout and inhaul, and magnitude of cyclic tension during inhaul were identified, measured and compared against payload. While payload was similar in the treatments, the additional weight of the double-hitch carriage resulted in higher skyline tensions. In both treatments, payload and skyline tension when the carriage was at midspan were strongly correlated. Cyclic tension was reduced by the double-hitch carriage system. While a number of unique high-dynamic loads were identified that were not part of the normal extraction, they represented only 6% of the cycles and the maximum tension was similar to that experienced during break-out and inhaul. This study increased the understanding of skyline tension during logging operations and the effect of carriage type. It showed that, though tension often exceeds the safe working load of the cable, it does not exceed the endurance limit for a well-designed and operated system.

摘要

用于电缆测井的钢丝绳，其中一系列电缆有助于在陡峭地形上提取木材，经历必须管理以确保安全的高张力。随着时间的推移，创新会改变做法，最近的一个例子是允许水平提取树木的双挂车。这使得在有限偏转的地形上收获成为可能，增加了生物量的回收，并有可能减少与地面接触相关的高动态载荷事件。在这项研究中，在受控条件下将标准单挂车与新型双挂车进行了比较。连续测量张力，并确定特定元素，例如车厢在跨中时的张力、拉出和回拉时的最大张力以及回拉期间循环张力的大小，测量并与有效载荷进行比较。虽然处理中的有效载荷相似，但双挂钩支架的额外重量导致了更高的天际线张力。在这两种处理中，当车厢处于中跨时，有效载荷和天际线张力具有很强的相关性。双挂钩运输系统降低了循环张力。虽然确定了许多独特的高动态载荷，它们不属于正常提取的一部分，但它们仅占循环的 6%，并且最大张力类似于在拆卸和进料期间所经历的张力。这项研究增加了对测井作业期间天际线张力和车厢类型影响的理解。它表明，尽管张力经常超过电缆的安全工作负载，但它不会超过设计和运行良好的系统的耐久极限。