Bunkering at Sea (Bunker Fuel supply to ships)

What is bunkering at sea

Taking fuel at high-seas is convenient and can save vessel owners thousands of dollars by avoiding costly port fees and lost travel time. The majority of the high-seas bunker tankers only carry MGO, although some of the high-seas tankers can also supply IFO-380cst and IFO-180cst. All of the fuel supplied by these tankers meet international bunker specifications and conform to Regulations.

Transporting cargo overseas is increasing in popularity. Because of this, ships are constantly getting bigger. This causes problems for the ports. Ports can only handle a certain amount of cargo at a time. Therefore bigger ships remain in ports for a longer time. This causes port congestion. The effect is even worse when vessels need to enter the port specifically for bunkering. With the current way of bunkering, vessels need to enter the port and berth. Due to this, other vessels have to wait for a berthing place to load and/or unload. A part of this congestion can be prevented if vessels can bunker at sea, instead of while at berth.

Bunkering usually takes place in a port. Fuel oil gets transported to the ports by tankers. It will be collected in a storage place in the ports. A small ship filled with the fuel or other supplies will go alongside the ship that needs to be bunkered. Port congestion can be caused by vessels bunkering. The desired situation is to create an innovative solution to resolve port congestion by bunkering at sea.

It is recommended to use a bunkering tower. The tower is already in use for transferring liquids between the shore and tankers, so the system already works. To operate the tower, a crew is required on the tower. When there are no vessels requiring bunkers, the crew can be taken off the bunkering tower.

Bunkering is supplying a ship with fuel, lubricating oil, or potable water, which usually happens in a port. It can also be done at sea, but this does not happen often.

The navy and a number of companies already bunker at sea, it saves a lot of time and money because vessels do not have to enter the port, and they do not have to pay the port fees. Bunkering in ports also causes port congestion, because other vessels have to wait for a berthing place when a vessel is bunkering.

Bunkering at sea can be complicated in bad weather conditions, so it usually happens in good weather conditions while the vessels are stopped. A system needs to be developed which makes it possible to bunker at sea under various circumstances.

Dynamic positioning system
This system, also known as DP, is widely used in all sorts of offshore operations. This system is capable to keep a vessel in the desired position. The desired position for a bunkering vessel at sea is a fixed distance from the receiving vessel. This system is using photography instead of Global Positioning system (GPS). And has an accuracy of 2 cm.

There are three different kinds of Dynamic Positioning systems.
DP1 makes sure the vessel stays in the desired position.
DP2 makes sure the vessel stays in the desired position, and allows for compensation when an error occurs, two independent systems.
DP3 makes sure the vessel stays in the desired position, and allows for compensation when an error occurs, two independent systems and a backup system.

For bunkering at sea at least a DP2 system is required, because it would be harmful to the environment if the hose disconnects and bunkering fluids leaked into the ocean.

Disconnect-able Turret
The turret mooring system consists of a turret assembly that is integrated into a vessel and permanently fixed to the seabed by means of a mooring system. The turret system contains a bearing system that allows the vessel to rotate around the fixed geostatic part of the turret, which is attached to the mooring system.
The turret mooring system can also be combined with a fluid transfer system that enables connection of (subsea) pipelines to the vessel like an F(P)SO. The fluid transfer system includes risers between the pipeline end manifold (PLEM) at the seabed and the geostatic part of the turret. In the turret a swivel provides the fluid transfer path between the geostatic part and the free weather vaning vessel that rotates around the turret.

The turret system is fully passive and does not require active vessel heading control or active rotation systems in the turret or swivels.
The turret system can be located externally or internally with respect to the vessel’s hull structure.

The turret system is a common system for Floating Production, Storage and Offloading vessels (FPSO). This system is used in case of an approaching hurricane or ice. It can quickly disconnect from the turret and leave the dangerous site. When using this system for bunkering, the vessels that require bunkers do not have to enter the port. The vessel can moor at this turret and load the required liquids.

Offshore bunkering tower
The idea of the tower mooring system consists of a tower structure that is permanently fixed to the seabed by means of piles or a gravity base. The tower contains a bearing system that allows a part of it to rotate around the fixed geostatic part. When moored to this rotating part of the tower with a mooring connection, the vessel is able to freely weathervane around the geostatic part of the tower.

Navigation and mooring
Vessels will approach the tower with its bow at slow speed, this gives the maximum control over the vessel and minimizes the need for tug assistance. The mooring tower will be designed to match all necessary requirements for all different kinds and sizes of vessels to moor. Various factors need to be kept in mind by the design of the tower, the tower mooring systems are typically designed for near shore applications with water depths of up to 50 metres. The mooring connections use the following systems: hawser and soft yoke.

Storage and transportation of the bunkering fuel
The bunkering fuel will be transported from a terminal on shore. These terminals are filled with fuel by large crude tankers. The bunkering tower is connected with the terminal by a pipeline which lies on the seabed. The fuel will be transported through the pipeline. Because of the high viscosity of the fuel the (subsea) pipeline must be heated. This happens by blasting steam from shore with very high pressure through the pipe while the bunkering fuel is transported. To make this possible it is important to use a pipeline with a double hull.

Cleaning the pipeline
When the vessel is ready with bunkering the pipeline is full with a bunker product ( for example HFO), the next vessel willing to bunker might need MDO, to make this possible the pipeline has to be cleaned. To make sure that there is no more HFO left in the pipeline you can use a pig.
Pigs come in all sizes and shapes, it is important to use the correct pig on the correct diameter of the pipeline. When the vessel which is bunkering is for 80% filled with fuel, they inform the shore that they can stop pumping bunkering fuel. Now you’ll see that there is some HFO left in the pipeline. This is accomplished by inserting the pig in the pig launcher( or launching station). After this, the launching station will be closed and the pig will be pushed through the pipeline, under high pressure, all the way to the receiving station on the mooring tower taking all the rest HFO with it. Now the subsea pipeline is clean again and ready to receive its next bunkering fluid.

Sea going bunkering vessel
This seems to be the most realistic way to bunker at sea. Ship-to-ship bunkering while both vessels are stopped is an operation that does not allow for moderate or rough weather conditions, bus it is more practicable, less expensive and no specifically trained crew is required.
Current bunker barges need to be made stronger and equipped with a beam to make them suitable for use at sea.

Bunkering while sailing:
By doing field research at bunkering companies and Bluewater the conclusion can be made that the idea of using either the Ampelmann or dynamic positioning systems are of no real contribution. The shipping industry is a sector which always pays a lot of attention to prices and expenses and since these systems are not necessary, it is unlikely these systems would be applied at sea bunkering.
During a conversation with a bunkering company it turned out that only 5% of all ships in the port of Rotterdam specifically enter the port to bunker. That small amount does not really contribute to the total port congestion.
A vessel without these systems seems much more interesting. A river sailing bunker barge with a seaworthy hull and a large bunker beam might be enough to bunker other vessels at sea.

Offshore bunkering tower:
The bunkering tower seems a great way to bunker vessels, too. It might be most profitable to place these towers in an anchorage or a channel with a lot of ships passing through, because there will be a large number of customers in those locations.
It might be required to crew the bunkering tower. It might also be necessary to train crews that moor the vessel at these towers, or they can request a pilot for the operation.
The tower is expected to be operational in heavier weather conditions than a sea going bunker barge, so a larger part of the port congestion will be resolved in the relevant port.

After analysing two inventions it is found that, the bunkering tower seems the most successful one. It allows bunkering in heavier weather conditions, the structure of the tower allows the bunkering hose to be transferred to the receiving vessel more easily, and the tower can be built in anchorages or even near windmill parks. Also, with two vessels there will be two independently moving stations, with the tower only the requiring ship will move, so it is safer.
The bunkering tower does not at all replace the current method of bunkering. It can be built in ports where vessels come in specifically for bunkering. Those vessels will no longer require a berthing place and they no longer have to wait for the bunker barge to come.
The ideas unfortunately have not been tested in practice. Before the solutions can be carried out in practice, further research is recommended. When the solutions and recommendations are examined, the ideas can be implemented.

If there is the desire to bunker with a sea-going bunker barge, a Dynamic Positioning system and an Ampelmann system are not necessary for this purpose. A seaworthy hull and a larger bunker beam are required.
However, it is recommended to make use of the bunkering tower. These towers are stationary, adjust their rotation based on wind and current, and allow sea-bunkering in heavier weather than a bunker barge. It is also possible to take the crew off the tower when no vessels order bunkers. A bunker barge needs a constant running crew, also during its downtime, and that would be wasted expenses.
It would also be inefficient to only bunker in the port with a much more expensive bunker barge, which is likely to happen in times of rough weather, whereas the tower is still operational.
At this point is not possible to say whether the tower can be operated independently, so a crew to operate the tower is recommended at this point.
It is also recommended that if ship owners wish to make use of the tower, either a pilot comes aboard, or the crew has to be trained for these purposes.
Currently, a similar system is being used for transferring liquids between the shore and tankers, so that proves that the system works already.

Bunkering at sea is a revolutionary idea. High-sea bunkering does not yet happen. The most similar way, that does exist, is bunkering in front of a port, in a bay. Singapore anchorage is one of the locations where this is applied. However, this bay is enclosed by land at all sides, with only relatively small streams of water in between. This makes the water and weather to behave more calmly, making it easier for bunker barges to sail over these waters. The North Sea, for example, is a lot less calm, and often high waves and heavy winds occur. Besides that, the North Sea is a very dense and popular location for merchant vessels. Bunkering currently only happens with two vessels stationary, in port, or a bay similar to Singapore.

Check bunker prices for main ports.

Follow latest bunker price updates.