Double Cycling - Reduce ship turnaround time by 10%

Optimising several tasks in as few movements as possible separates high-performing ports from their competition. Double-cycling or dual-cycling of quay and yard cranes is an optimisation technique used within container ports. It is often a key consideration in discussions between the container terminal and shipping company port captains, port superintendents and vessel operations managers.

We’ll look at defining double-cycling, the rationale behind its use within container ports and how double-cycling can improve or affect vessel turnaround time.

For clarity, we’ll discuss double-cycling in quayside gantry operations, but these processes and techniques also apply to container yard operations.

Double cycling in the Port of Valencia
(Image credit: Intelligent Cargo Systems)

What is Double Cycling?

Double-cycling is a process where the container terminal discharges and loads with a single gantry in one move (and vice-versa).

For example:

1. A chassis brings a container for load to the gantry.

2. The gantry picks up the load container, and the chassis waits under the gantry

3. The gantry loads the container on the seaside hatch cover

4. The gantry picks up a discharge container on the landside hatch cover

5. The gantry discharges the container to the chassis

6. The chassis takes the discharged container to the yard stack

This process repeats until the double-cycling operation is complete. 

What are the requirements for Double Cycling?

It’s advantageous, though not mandatory, for the discharge and load operation to be on the same bay. This minimises the gantry from undertaking longitudinal quayside movements between the discharge and loading operation.

Double cycling operations are straightforward in cargo holds, especially in adjoining rows. When double cycling happens on deck, it works best when the operations are on adjoining hatch covers, as this will minimise travel and hoist time from the loading hatch cover to the discharge hatch cover.

The most useful aspect of dual cycling is the flexibility in operations on the bay. For example, if there are tasks to load in the cargo hold beneath empty centre cargo hatch covers and discharge the outboard hatch covers on deck, this operation can be done in either a single cycle (discharging deck then loading underdeck) or as a double cycle (loading underdeck and discharging on deck). The key parameter here would be the height of the discharge containers on the deck, causing unnecessary hoisting, but the flexibility of double cycling means consecutive tasks can be completed in a single move.

Advantages of Double Cycling

By effectively carrying out two moves in a single gantry move, double-cycling is an attractive option for container terminals to improve efficiency.

Gantry utilisation is high with less idle time expected. As the chassis is involved with two containers per move rather than one, the gantry does not need to wait for a chassis to arrive to supply or transfer the container to and from the stacks.

1. Increased Efficiency: Double cycling can significantly cut down berthing time. This efficiency is a game-changer in port operations, contributing to quicker turnaround times.

2. Optimized Crane Utilization: Double cycling maximises gantry usage by engaging cranes in a continuous load/unload cycle. This is particularly crucial during peak periods when crane availability can bottleneck operations.

3. Cost Savings: Reduced port stay times directly translate to lower port charges and operational costs for shipping lines, while opening up berth capacity for container terminals. The faster turnaround times mean ships can maintain their sailing schedules, reducing the need for costly speed-ups in transit.

Disadvantages of Double Cycling

1. Operational Complexity: Double cycling requires precise coordination and planning. The complexity of simultaneously handling different container moves can strain terminal management and operational frameworks. Most ports engaging in double cycling will have a TOS capable of planning these moves without comprising the overall cargo operations plan.

2. Infrastructure Demands: Not all ports have the infrastructure, technological capability or landside space to support double cycling effectively. This limits its application to more advanced and equipped ports.

3. Risk of Delays: Any misstep in the intricate dance of double cycling can lead to operational delays. This could offset the time savings if not managed meticulously.

4. Training and Skill Requirements: Efficient double cycling demands highly skilled crane operators and ground staff, necessitating ongoing training and upskilling.

Double-cycling on an aft bay in Port of Valencia
(Image credit: Intelligent Cargo Systems)

Why propose double cycling?

In a 2007 paper from Goodchild and Daganzo, double cycling can reduce operations time by 10% and landside vehicle use reduction by one driver and chassis per gantry.

These are significant costs that would otherwise have been passed on to the shipping company. But, this also means that the shipping company should plan stowage with double cycling terminals to make such processes feasible.

Are there cargo software systems to know when double cycling occurs at a port call?

Depending on your relationship with the container terminal, they may inform you when double cycling is planned for your vessel’s port call or is occurring. Still, they are unlikely to let you know the effectiveness or productivity gains/losses caused by the operation. The outcome may only be shared once operations are complete and the terminal departure report has been shared with the shipping company. At this point, the potential for any remedial action has been lost.

Proactively monitoring and collaborating with the container terminal as they work your vessels can be the difference between on-time or costly, delayed departures.

Utilising a cargo operations software system such as CargoMate can provide a real-time view of the operations without needing the terminal to provide regular updates.

There are three details CargoMate measures which can indicate when double cycling is in use:

1. Gantry performance for a single gantry is notably higher than the other gantries operating on the vessel

2. The crew and/or senior officers onboard have observed and noted double cycling is occurring

3. CargoMate shows the gantry operations per bay, so you can see when loading and discharging are happening at the same time

4. A terminal performance report on completion from CargoMate shows comparable gantry moves to the terminal’s departure report.

Using these four features, CargoMate ensures that vessel operations managers can monitor cargo operations with the right information at their fingertips.