Crane Double Cycling in Container Ports

Crane Double Cycling in Container Ports is a method of improving the efficiency off the cranes that are used. Time is money, so professionals are always searching for ways to improve ship dwell time in ports around the world. With container vessels the problem is probably even more clear than with other types of vessels, as the crane returns empty every time it is sent back to the ship to pick up another container to be unloaded.

A possible solution to this problem could very well be what is called “Double Cycling”. The intention is that the crane will load a new one every time it has unloaded a container and as such reducing loading/unloading time of the ship. However, it is not easy to find a correct schedule to do this. Scheduling proves to be very difficult.

Use of algorithms

A solution to this problem was formulated by Anne V. Goodchild and Carlos F. Daganzo in their paper called “Crane Double Cycling in Container Ports: Affect on Ship Dwell Time” (April 1, 2005). They provide two solution algorithms and simple formulae to estimate reductions in the number of operations, and operating time. Small problems can be solved to optimality with a standard numerical solver, but problems of typical size are computationally burdensome and terminated after 10 hours with optimality gaps larger than 50%. A formula for an improved lower bound to the optimal solution is developed and shows the optimality gaps are actually below 2.5% in all cases. The paper presents a greedy algorithm that can obtain solutions in seconds. A formula for an upper bound to the greedy algorithm's performance can be used to accurately predict crane performance. The problem is extended to include an analysis of double-cycling when ships have deck hatches. Results are presented for many simulated vessels, and compared to empirical data from a real-world trial.

Conclusions

The paper demonstrates that analytical methods can be used in addition to numerical methods to provide greater insight. More importantly, the paper demonstrates that double-cycling can create significant efficiency gains.

External links

• Institute of Transportation Studies, University of California, Berkeley