The lashing of containers onboard a ship is a hard and sometimes dangerous operation. The working conditions may vary dramatically depending on the types of container vessels in use and the weather. There are great safety problems during loading and discharge of containers especially when a neighbour bay is open. The stevedores who carry out this work sometimes have to work on container stacks which are several meters high above the ship’s deck, under the suspended load, and in cages operated by quay cranes. Safety arrangements in some ports are poor and the work frequently has to be performed in the dark, under windy, rainy, and icy conditions. The problems are to a large extent due to the lashing equipment. Container ports often use sub-contractors for performing the lashing and unlashing activities. In most cases the focus is put on decreasing the vessel port stay time without taking into account proper planning and safety restrictions. arl-shipping.com has taken upon itself the development of an algorithm and software application which could help container terminal operators to reach two goals simultaneously: ensure that lashing and unlashing operations are being done in a safe manner at all times, and all operations are optimised in terms of man power and time. There is another sort of natural outcome there – financial benefits. If there are less lashing gangs servicing a vessel then terminal operators can save on lashing and unlashing expenses.
LASHING SPECIFICS
There are three types of stevedoring operations and three roles performing these operations are taken into account in the lashing/unlashing model used by arl-shipping.com:
– lashers mount and dismount lashing rods and chains onboard a vessel;
– conemen remove twist locks from the unloaded containers and insert twist locks into the being loaded ones;
– dowelmen remove locks on dowels from the onboard container stack.
The responsibilities and exact role naming and distinctions vary from terminal to terminal. Here is the example list of dowelmen responsibilities as defined by DP World in vacancy VAC2253:
– to open or remove locks on dowels from the onboard container stack in accordance to the instructions of the vessel supervisor;
– to ensure the proper placing of container on deck in vessel operations, as well as twist locks placing in a safe and efficient manner;
– to indicate the right signal to crane operator during discharging and loading containers;
– to remove and secure twist locks/cones/bridge fitting on the container for safely handling of containers;
– assist the duties of lasher on board thereby adding support to the container terminal operations.
If the container stack is too high then dowelmen perform the operations from the cage suspended from a quay crane. The terms used for stevedoring roles may vary from port to port but we will continue to use lasher, conemen, and dowelmen terms in this paper.
METHOD OF OPTIMAL PLANNING
How does the new approach help container terminals and what it the background it is built upon? In order to make a good plan one should know quite a lot about actual performance figures of lashing operations such as typical productivities of single, double, and chain lashing, average moving time between vessels. The same should be known for the operations performed by dowelmen: productivity for manual and semi-automatic twist locks, bridge fittings, etc. Vessel parameters are also important: what lashing gear is in use, number of tiers to lash, availability of cell guides, type of twist locks, etc. Taking into account ETA and ETD of calling vessels, QC work sequence, all available lashing gangs, their typical performances and vessel specs one can use a standard mathematical algorithm and distribute available gangs between vessels in time so the total servicing time would be minimal. The required computational power is not that big and modern computers can perform such a distribution within one second. The algorithm can make sure that there are no activities involving humans happening next to the open bay.
It makes sense to plan separately per lashing role and produce plans in various formats. Below one can see the simulated global view of lashing plan for the whole terminal:
The lashing plan for a specific vessel:
The plan for conemens:
The plan for dowelmens also includes indications of when a cage is required:
The same reports in tabular format can be generated and given out to all assigned gangs. The plan indicates the place of work (vessel and bay), type of work, how many containers to be processed and target time frames for the work. Modern container terminals can also require lashing gangs to report back when a piece of work is done, like for instance when lashing of the bay is finished.
Where should we get the source data to make a reliable plan? The input data required for the algorithm are normally managed by terminal operating system (TOS). All vessels’ ETA and ETD, quay crane work sequences are normally managed by the correspondent TOS modules. If the same data can be exported in the tabular format for instance then external application like lashing planner can manage the rest of specific input parameters like lashing gang performance. Knowing that re-doing of lashing plan takes only a second we can constantly update it and produce the best assignment plan by the time when we need to issue it. The tool additionally follows the execution of quay crane operations and safeguards that lashing assignments are adjusted according to real-life operations, and eventually substantiate the achieved savings.
CONCLUSIONS
The lashing planner application has been tested in a major Middle Eastern terminal who validated that the lashing planner application successfully resolves planning challenges with terminal planners, responsible for stevedore planning including assigning lashers, dowelmen, and conemen. According to the preliminary estimations done on the historical data from the pilot terminal the project team has concluded that the same amount of work could have been done with half the number of gangs used, (so reducing the cost by half), and in a safe manner. The result points at a big potential to improve the inefficient lashing resource usage which is probably the case for the majority of modern container terminals.