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Summary
In order to remain competitive, the container terminal operator needs to continue improving its waterside productivity.
The quay crane, mainly responsible for this productivity, has technical specifications implying a productivity which is almost 4 times higher than is realized in practice. In order to reduce the gap between the technical and the actual productivity all delays causing this gap need to be analyzed.
For this analysis the operation time is subdivided into ‘inactive losses’ and ‘cycle time’. ‘Inactive losses’ are losses that occur when a quay crane is not actually operating while the crane is supposed to be operating. ‘Cycle time’ is the time when a crane is in operation.
‘Cycle time’ is subdivided into ‘inactive cycle intervals’ and ‘active cycle intervals’. ‘Inactive cycle intervals’ are delays caused by positioning the spreader, with or without container, at the start or end of every sub-cycle and by stacker handling. ‘Active cycle intervals’ is when the spreader, with or without container, is traveling from one point to another.
‘Active cycle intervals’ closely represent the technical productivity besides the ‘active losses’ caused by human imperfections, that of the crane operator.
The different losses are determined by data analysis. The method of data collection was either by retrieving registered data from a database, or by direct observation.
The different losses can be either stochastic or deterministic by nature determining the method of analysis.
After analysis, target values are stated, and when these target values are achieved the productivity will increase. The target values were determined by the median of the different stochastic delays. To achieve the target values extreme values of delays need to be diminished.
When all target values regarding ‘inactive losses’ are achieved a production increase from 22,5 to 23,81 moves per hour is realized.
When implementing ‘hot-seat-swaps’ for meal breaks and shift changes and achieving the target values on ‘inactive losses’ a production increase from 22,5 to 26,18 moves per hour is realized.
When achieving the target values on ‘inactive cycle intervals’ a production increase of 26,18 to 29,71 moves per hour is realized.
The deterministic technical productivity is calculated to be 85,6 moves per hour. After subtracting the actual ‘active losses’ and the actual ‘inactive cycle intervals’ this productivity reduces to 41,18 moves per hour. From the actual overall production 22,5 moves per hour and subtracting the ‘inactive losses’ the productivity becomes 30,48 moves per hour.
This indicates a gap of almost 11 moves/hour, mostly unregistered delays. The largest share of these unregistered delays is caused by waiting time for an AGV. Making this delay by far the most influencing factor of the quay crane production.
It is recommended to focus on AGV waiting times for further improvement of quay crane production. Also, hot-seat swaps for meal-breaks and shift changes will result in the largest increase of quay crane productivity.
