New paradigm on double cycling



Jang-Ho (Remy) Song, Operation and Planning Team Manager, Pusan Newport Co., Ltd. (DP World), Pusan, South Korea


Double cycling by multi-quay cranes in container terminals


Under the rapidly changing maritime environments, worldwide container terminals are concentrating on improving productivity to reinforce market share and obtain competitiveness. Modern container terminals are quickly developing their equipment and facilities, and their productivity is increasing. This is largely due to a great deal of investment in equipment and infrastructure.

Double cycling can improve productivity without the need for extra investment on current equipment and infrastructure. It merely needs manpower, training and research into operational methods. If research on double cycling is revisited, the crane productivity will be vastly improved upon, because double cycling can maximize equipment efficiency.

Until now double cycling has generally meant the stevedore work conducted by a single quay crane, and in practice each crane achieves only around 10 percent of total exchanges. In other words, although in theory double cycling is great, it fails to live up to expectations due to low frequencies. Now we need to approach double cycling with a new paradigm to maximize the frequency of the practice.


We do not have to define double cycling based on quay cranes any more, since the biggest factor that has impact on the quay crane productivity is the yard tractor. There are three factors that have impact on quay cranes: the productivity of the quay crane, RMGC productivity and yard tractor productivity.

How many yard tractors have to be allocated to one quay crane to guarantee target crane productivity? It varies depending on the environment of the terminal, which is a problem in terms of cost effectiveness, though from the yard tractor perspective, the issue can be solved easily with double cycling. Moreover, the target quay crane productivity can then be achieved through less yard tractors.

It is time that the double cycle is conducted on individual yard tractors using multi-quay cranes to enhance the frequency of the double cycles. Due to the complications of terminal operations caused by the introduction of automated cranes and pooling systems of yard tractors, TOS should back-up the yard tractor double cycling with multi-quay cranes. This will require the enhancement of TOS and the development of work procedures for users.

The first stage; pinning station for double cycling by multi-quay cranes

Current pinning stations are not right for double cycling multiquay cranes (like Figure 4 above), in terms of achieving both productivity and safety. As yard tractors must move sideways then along, this increases the risks of incidents and it takes unnecessary additional time for yard tractors to drive into the designated lane. Therefore, a new type of pinning station should be developed to conduct multi-quay cranes double cycling. In Figure 5 above, where the back quay crane is loading and the front one is discharging, the pinning station for the discharging quay crane should move to make a straight line with the pinning station for the loading quay crane. This way, both the safety and productivity can be achieved.


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