Shipping containers go through various stages in the shipping process, from being loaded at the origin and transported to the port to being unloaded at the destination and finally returned to the carrier’s depot.
All containers that arrive at the port of discharge (destination port) are unloaded from the vessel. This process is also called container discharge. Once containers are discharged from vessels, they are temporarily stored at a port yard, before they are delivered to the consignee.
In this article, we’ll explain how containers are discharged from vessels, along with the challenges associated with the process. We’ll also discuss why the discharge date is essential for shippers and consignees.
How Containers Are Discharged From Vessels
When a container arrives at the port of discharge, it is unloaded from the vessel using port cranes. This powerful piece of machinery can easily unload 25 to 30 shipping containers per hour.
Below is a step-by-step process of how port cranes unload shipping containers from ocean vessels:
- Positioning the Port Crane
Prot crane operators are first tasked with positioning the crane near the vessel. Most ports have rail systems that cranes use to align themselves with the ocean vessel. They are then aligned, ensuring a clear line of sight to unload the containers.
- Lowering of the Spreader Bar
The crane operator then lowers the spreader bar and aligns it with a laden container in the vessel. Each port crane is responsible for unloader several rows.
- Locking the Container
Once the spreader is lowered, the edges are carefully aligned with the container. A twist lock mechanism then secures each container’s corner castings, ensuring a secure connection.
- Lifting the Container from the Vessel
The crane operator then activates the hoist cables to lift the container off the vessel’s deck. The container is gradually lifted to a safe height, ensuring it clears the vessel and other obstacles.
- Moving the Container
Subsequently, the container is moved towards the dock and positioned onto a terminal tractor. Before it’s loaded, the container needs to be safely aligned.
- Lowering the Container onto a Terminal Tractor
The container is gradually lowered onto the terminal tractor and fastened using twist locks on each corner casting. The terminal tractor then shunts the container into a yard in the port, before it’s delivered to the consignee by a container truck.
Challenges When Discharging Containers
Laden containers can weigh above 50,000+ and therefore require special equipment, operators, and expertise to unload safely. Although port crane operators are well-trained to load and unload containers in various port conditions, several factors may pose a risk.
- Port Congestion – Port congestion occurs when there is an influx of vessels entering or leaving a port, leading to delays, inefficiencies, and disruptions in port operations. These congestions typically happen when the demand for port services exceeds its capacity and container vessels have to temporarily wait outside of the port until an available berth opens.
- Equipment Breakdown – While most cranes, forklifts, stackers, and other types of port equipment are reliable, they are still susceptible to breakdowns. Hence, they can be the cause of delays and slow discharge processes at a port, especially during peak hours or situations in which operators have no backup equipment.
- Weather Conditions – High winds, rain, ice, and other types of extreme weather can put the safety of crane operators and container handlers at risk. Hence, crane operators have to be extra vigilant when operating under harsh conditions.
- Labor Shortages – In specific scenarios, ports may have sufficient equipment to unload containers but insufficient operators and labor to manage the process. This typically happens during the holiday season or during periods of high demand.
The Importance of Container Discharge Date
The container discharge date is important for carriers, shippers, and consignees, as this date marks the start of container demurrage and port storage. Depending on the freight terms, either the consignee or the shipper is responsible to pay for demurrage and port storage, depending on the number of free days given by the carrier.
Most carriers use the container discharge date, the date that the container is unloaded from the vessel to calculate demurrage, which ends once the container leaves the port of discharge.
At the same time, the consignee (in this case often the receiver) uses the date to plan cargo pick-up and appoint a trucker to pick up the laden container from the port.
How the Container Discharge Date Is Captured
Port cranes start unloading shipping containers the moment the vessel berths at the port of discharge. However, depending on the vessel size, number of containers, and port conditions, the process can easily take up to three days or even longer.
Since carriers are responsible for paying berthing fees, it’s in their interest to accelerate the process and minimize the vessel turnaround time. Each unloaded container is then loaded onto terminal tractors.
The discharge date is registered and stored in the port’s system, which is often integrated with the system of carriers and shipping lines.
The port system and the carrier will therefore often reflect the same date and timestamp of the discharged container. This also means that multiple containers on the same vessel and even on the same bill of lading may have different discharge dates and times.
What Happens After Containers Are Discharged?
Once containers are discharged from the ocean vessel, they’re transported to a container yard within port premises by terminal tractors for temporary storage, to avoid congestion on the docks.
These containers are then stored until the consignee or shipper arranges for the pickup. The laden containers are then loaded onto semi trucks with container trailers, typically using gentry cranes or reach stackers.
Before the container gates out of the port and is delivered to the consignee, it is weighed by port officials to calculate the gross weight. After the container is delivered and the cargo is unloaded, the empty container is returned to the carrier’s container yard (CY).
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Co-Founder & Writer
About the Author
Gerrit is a certified international supply chain management professional with 16 years of industry experience, having worked for one of the largest global freight forwarders.
As the co-founder of freightcourse, he’s committed to his passion for serving as a source of education and information on various supply chain topics.