STS Operations: Ship-to-Ship Transfer vs. Traditional Port Unloading in Indonesian Waters

Choosing a flexible sts operation over standard berth discharges allows vessel operators to bypass port congestion and significantly reduce turnaround times. While traditional port unloading requires waiting for available berth slots and shore infrastructure, offshore transshipment enables direct cargo transfers between vessels. Executing these transfers safely across indonesian water keeps chartering schedules intact while optimizing overall voyage economics.

What Is Ship-to-Ship Transfer?

Ship-to-ship (STS) transfer is the movement of cargo directly from one vessel to another while both are at anchor or underway in an approved area. It is most often associated with liquid cargo such as petroleum products, chemicals, and gases, although some dry bulk cargoes are also transferred between vessels using floating cranes or barges.

Indonesia is an archipelago with long coastlines, many anchorages, and ports that differ widely in depth and capacity. STS transfer can therefore be a practical option where shore infrastructure is limited or where a vessel is too large for the port it needs to serve.

What Is Traditional Port Unloading?

Traditional port unloading takes place when a vessel berths at a jetty or terminal and discharges cargo to shore. Cargo goes to terminal storage, trucks, rail, pipelines, or barges, using the port’s cranes, pumps, and handling equipment. This remains the standard method for most cargo in Indonesia. It relies on port infrastructure, berth availability, and the terminal’s own procedures.

STS vs. Traditional Port Unloading: Quick Comparison

The table below summarizes the main differences between the two methods.

Aspect	Ship-to-ship transfer	Traditional port unloading
Location	Designated anchorage or approved transfer area	Berth at a port terminal
Infrastructure	Support vessels, fenders, hoses, or floating cranes	Berth, jetty, shore cranes, pumps, and storage
Vessel size	Can serve vessels that are too large for a port’s draft or berth	Limited by channel depth, berth length, and terminal capacity
Scheduling depends on	Weather, sea state, and availability of the second vessel	Berth availability and terminal queue
Cargo destination	Second vessel, which carries it onward	Shore storage or inland transport
Main cost drivers	STS service provider, mooring master, equipment, support vessels	Port dues, terminal charges, pilotage, towage, stevedoring
Regulatory focus	Approved transfer area, STS plan, local authority coordination	Standard port clearance and terminal procedures

Operational Comparison

The two methods differ most in where the work happens and what it depends on.

Port infrastructure

Traditional port unloading depends on a suitable berth, enough water depth, and working shore equipment. Where these are limited, vessels may wait for a berth or discharge only part of their cargo. STS transfer reduces reliance on the berth. It does, however, require suitable sea conditions, a safe transfer area, and the right equipment for the cargo.

Vessel size and draft

Larger vessels can be restricted by channel and berth depth. STS transfer allows cargo to be moved to a smaller vessel that can enter the port, or between two vessels that are both offshore.

Weather and scheduling

A sheltered berth is generally less exposed to sea conditions. STS operations depend more on wind, swell, and visibility, so schedules need to allow for weather delays.

Coordination

STS involves more parties working at the same time: two vessels, a mooring master or STS superintendent, support craft, service providers, and local authorities. Traditional port unloading involves the terminal, port services, and the vessel, which many operators handle routinely.

Financial Comparison and Cost-Benefit Analysis

Neither method is always cheaper. The result depends on cargo type, volume, vessel size, location, and how long each option takes. The table below shows where each method may offer a cost advantage.

Cost factor	Where STS can help	Where traditional port unloading can help
Waiting time	May reduce time spent waiting for a congested berth	Berth scheduling can be predictable at well-run terminals
Draft limits	May avoid partial discharge or additional lightering	Suitable where the port can handle the vessel fully loaded
Port charges	May reduce some berth-related charges	Charges follow established terminal and port tariffs
Specialist services	Adds cost for STS provider, mooring master, and equipment	Fewer third-party providers are normally needed
Weather exposure	Weather delays can extend time and increase costs	Sheltered berths are less exposed
Shore handling	Depends on the receiving vessel or onward arrangements	Terminal storage and handling may be available directly

A practical way to compare the options is to look at the total cost and time of the whole cargo movement, not only the transfer itself. Consider waiting time, port charges, service fees, equipment hire, insurance, and the cost of delay. For large cargo volumes or restricted ports, STS may offset its extra services. For smaller volumes or well-served ports, traditional port unloading is often the simpler option.

Regulatory Requirements in Indonesia

Regulatory requirements are one of the biggest differences between the two methods. Traditional port unloading follows the normal port clearance and terminal procedures. STS operations in Indonesia involve additional requirements, and these can vary by location, cargo, and vessel type.
Points that operators commonly need to confirm include:

• whether the transfer will take place in an area approved for STS activity;
• permits or standards that apply to the STS activity and the parties performing it;
• coordination with the harbormaster and relevant port authorities;
• vessel clearance and approvals, including approvals for foreign vessels where applicable;
• customs, immigration, quarantine, and other clearances that apply to the cargo and vessels; and
• environmental and reporting obligations.

For oil tankers, international rules under MARPOL Annex I also require a plan covering how the STS operation will be conducted. Industry guidance such as the Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases is widely used to prepare these plans. Requirements can change, and different locations may have their own local guidelines. Confirm the current requirements with the relevant authorities before the operation is planned.

Safety Protocols for STS Operations

STS transfer has risks that are different from berth-based discharge. Two vessels are close together at sea, so safety planning has to begin well before the vessels meet. Common safety measures include:

• a vessel-specific STS transfer plan and risk assessment;
• agreement on cargo type, transfer rate, and transfer procedure;
• an experienced mooring master or STS superintendent;
• checks of fenders, mooring equipment, and hoses before use;
• weather and sea-state limits for approach, mooring, transfer, and departure;
• clear communication between both vessels and the shore;
• emergency shutdown and stop-work procedures; and
• pollution response arrangements and equipment.

Safety decisions remain with the Masters, the vessels’ management, and qualified STS personnel. The operation should stop whenever conditions or equipment no longer meet the agreed limits. Safety is also important in traditional port unloading, but it relies more on terminal procedures, shore equipment, and the berth environment.

When Does Each Method Make Sense?

The right choice depends on the circumstances of the cargo operation. STS may be worth considering when:

• the vessel is too large or deep for the available berth;
• the berth is congested or shore facilities are limited;
• cargo needs to move to a smaller vessel for onward delivery; or
• the cargo volume justifies the additional equipment and services.

Traditional port unloading may be the better choice when:

• suitable berth and shore facilities are available;
• the cargo needs direct shore storage or inland transport;
• the cargo volume is small; or
• weather exposure at the anchorage creates too much schedule risk.

The Ship Agent’s Role in STS Operations

STS operations involve many parties, so coordination matters as much as the transfer itself. A ship agent can help connect the vessels, the STS service provider, support craft, and local authorities, and can coordinate arrangements for permits, notifications, and vessel access. The agent does not perform the transfer or decide on safety. Those responsibilities stay with the vessels’ Masters, management, and the qualified STS provider.

When the vessel owner or operator is based outside Indonesia, local coordination helps ensure that requirements are understood early. Treating the permits, services, schedule, and communication as one operation also reduces the chance that a missing arrangement delays the transfer.

STS Operations With Balancia

Balancia Ship Agency coordinates support for vessels calling ports and anchorages across Indonesia. Depending on the requirement, we can assist with local coordination for STS operations, including communication with authorities, service providers, support vessels, and other parties involved. We can also support traditional port calls and cargo operations, so owners and operators can compare both options with local input before deciding.

People Also Ask

References

• Maritime Trainer. (2026, August 4). Retrieved from Beyond Proximity: The True Complexities of Bulk Carrier STS Operations: https://maritimetrainer.com/blog/beyond-proximity-the-true-complexities-of-bulk-carrier-sts-operations
• Naval Orientation. (2026, August 11). Retrieved from Ship-to-Ship Transfer Operations: Planning, Compatibility and Compliance: https://navalorientation.com/ship-to-ship-transfer-planning-compatibility-compliance/
• PGN LNG. (2024, August 29). Retrieved from Ship-to-Ship Transfer: Jenis Operasi dan Cara Aman Melakukan STS LNG Transfer: https://pgnlng.co.id/berita/wawasan/ship-to-ship-transfer/