Caterpillar Performance Handbook, January 2017, SEBD0351-47

Cycle Times

Hydraulic Mining Shovels

CYCLE TIMES The cycle time of a hydraulic mining shovel is an important productivity factor, and a key driver for high or low performance. There are two main areas that influence cycle times. One factor is the pure technical capability of the hydraulic mining shovel. The engine output and associated hydraulic power defines the maxi- mum available oil flow, which consequently determines the speed of the hydraulic cylinders and swing drives, and ultimately the achievable working speed of the machine. The other factor is site specific parameters, such as operator skill, bench height (in particular for hydraulic front shovels), and swing angle, will impact cycle times considerably. Material fragmentation and penetration resistance make a big difference, as well. Large hydraulic mining shovels are used as the prime mover in most applications. Therefore, the set-up of the loading area is pre-considered to be favorable for pro- ductive loading conditions when defining cycle times. Those are for example: For backhoe machines For face shovel machines Truck position lower level same level Average swing angle 60°–90° 90° Bench height similar to stick length 75% of max. reach height A complete working cycle of a hydraulic mining shovel can be separated into four segments: ● Bucket fill ● Swing loaded ● Dump ● Swing empty

However, the bucket fill process constitutes the main fraction of the loading cycle, with a portion between 40% and 50% of the total time. This is heavily influenced by the material parameters, therefore, the different cycle times, shown for each model in the attached diagram, only consider the increasing effort to fill the bucket: ● Ideal loading conditions —Loose material, such as dry sand, soil and gravel, or re-handled or tipped material with no effort to achieve a good fill. Bucket can pene- trate anywhere in the face or pile without resistance. ● Average loading conditions — Soft overburden with low grade of compaction, and well-shot material with good and consistent fragmentation. Operator doesn’t have to concentrate on loosening or finding the right spot for penetration. ● Fair digging conditions — Shot rock with partially interlocked sections, or compacted overburden, requir- ing some effort to loosen the material. ● Difficult digging conditions — Inhomogeneous shot rock with some oversized boulders and interlocking, or unblasted material. Also free digging applications in sediment type of rock with fractures and layers which allow to penetrate the material. Considerable effort required to break out material. ● Severe digging conditions — Poorly shot rock with a large amount of oversized boulders and/or heavily interlocked material in the majority of the face. Also free digging operations with high digging resistance. In those conditions neither cycle times nor bucket fills are predictable.

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