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Container Shipping & Trade

Container Shipping & Trade

Containerships: leading the way for LNG box ships

Mon 18 Feb 2019 by Rebecca Moore

Containerships: leading the way for LNG box ships
Shell is supply the LNG for Containerships’ LNG vessels via ship-to-ship bunkering at the Port of Rotterdam (credit: Containerships)

CMA CGM-owned Containerships has received 1,400-TEU Containerships Nord – the first container ship newbuild in Europe to run on dual-fuel LNG.

Built by Wenchong Shipyard in China, the 1,400-TEU feeder vessel will be followed by three more gas-fuelled ships, scheduled for delivery during H1 2019. There are also options for two more vessels.

“By taking this decision, we accepted the challenge of building with a new technology. It has been a rewarding project full of learning opportunities”, said Containerships’ chief executive Kari-Pekka Laaksonen.

Containerships’ LNG-concept involves more than just the vessel-side of the supply chain – it spreads out from sea to land, and the target is to create a complete, LNG-based door-to-door supply chain in Europe. In addition to LNG-powered vessels, the company is investing in LNG-fuelled trucks.

The vessel was classed by ABS. Summing up the main challenges and considerations of deploying LNG on this box ship, ABS regional business development manager Daniele Bottino told CST “Using LNG as fuel on non-gas carriers creates numerous challenges and for this series of container ships, the main ones included the location and arrangement of the LNG fuel tanks and the fuel gas supply system. Space on a small container ship is at a premium so locating the fuel tanks and fuel gas supply systems to minimise the impact on the vessel’s cargo capacity and operations is important.”

In this case, the vessel is designed to transport containers holding numerous types of cargo and the fleet will operate in the Baltic Sea, where Finnish and Swedish ice navigation guidelines are applicable.

Another challenge was that building a ship with LNG as fuel was a new endeavour for the chosen shipyard. Mr Bottino commented “With interest in LNG as fuel growing, many yards have entered this sector with limited expertise in working with complex gas and cryogenic systems. For ABS, this required a more proactive approach than the typical supervisory role of class, helping the yard to understand the key design and construction challenges.”

He said the vessel was designed with a fuel gas handling room rather than the conventional tank connection space, with fabrication and welding completed on board during construction by the yard under the supervision of the vendor’s service engineer.

Engines a ‘perfect match’

Containerships’ vessel deploys WinGD’s 7RT-FLEX-50DF engines, with an MCR of 10,080 kW x 124 r/m. WinGD also provided the gas valve unit and other hardware associated with the engines.

WinGD general manager warranty and projects operation Erkki Rahja explained that the project was first discussed about five years ago. “Containerships wanted to reduce emissions in the entire logistics chain,” he said. WinGD’s engines were seen as a “perfect match” for the project.

“When we first discussed this in 2014, the two-stroke dual-fuel engine was a new concept and idea and the engine only existed in the test bed at that time. Therefore, the challenge was to get the engine performance optimised, that was critical to make a success of this project.”

In 2016, WinGD’s first dual-fuel engine entered commercial operation. “This proved that the concept was going to work very well for Containerships, too,” said Mr Rahja. Containerships Nord is the first instance where WinGD’s LNG dual-fuel two-stroke engine is installed. It is also going to install the ‘big brother’ X92DF-engine of 50DF on CMA CGM’s gas-fuelled ultra large container ships.

Control of the gas feeding engine is through a remote-control system. “This was not in our scope but when doing this project there were a lot of discussions with stakeholders including the remote-control system maker (Nabtesco) and TGE Marine from a technical and safety concept point of view as the system must be very safely designed and operated.”

Highlighting the major challenge of the technical construction of the ship, Mr Rahja said “The big issue is always where to install the gas tanks and system – the engine itself is not a big difference from a conventional diesel engine.”

Gas fuel supply considerations

A 3D view of TGE Marine’s vertically tanks – the tanks were placed vertically to gve the highest volume efficiency

TGE Marine scooped the contract to provide the gas tanks and gas fuel supply solution.

TGE Marine sales engineer and LNG technology specialist Max Liese explained that three Type C tanks were placed vertically, with the gas plant placed on top of these.

Mr Liese explained “This is the arrangement that gives the highest volume efficiency. With Type C tanks the issue is that volume efficiency is not always perfect due to their roundish shape – the tanks have to be integrated into the hull and the space around tanks can be more or less lost. This was the most suitable concept to minimise the space lost.”

He explained that other tank concepts, including prismatic shaped ones have better volume efficiency as they can mould to fit the shape of the hull.

The benefit of using type C tanks is their pressure is above atmospheric, as opposed to prismatic tanks. Mr Liese explained “That means that if gas pressure increases you can wait and give time for the ball of gas to evolve, there is no need to carry out any actions to release the ball of gas.”

By contrast, in a prismatic tank, the gas pressure will reach a certain threshold and then action needs to be taken.

Mr Liese said of a type C tank: “From an operational point of view it is very smooth – the big advantage comes when bunkering. When bunkering a type C tank, the pump pushes LNG into the tank and if that is done fast the pressure increase is quite fast due to heat ingress coming from the hoses. But the pressure increase is really relaxed as Type C allows you to increase the pressure in the tank. If you have a prismatic tank with a maximum design pressure of 700 millibars, which is slightly above atmospheric pressure, you have to take care of the bunker process, this reduces bunkering speed and increases time spent bunkering as crew have to reduce bunker velocity and ensure that the pressure does not increase too much.”

The dual-fuel gas engines were provided by WinGD. Mr Liese said the interface between the engines and gas supply system was not fixed at the beginning, so a “lot of work was invested with WinGD to optimise that interface”, which worked well in operations.

The vessel will operate on LNG but the dual-fuel concept will provide safe return to port and some redundancies in the system. However, Mr Liese pointed out that the gas supply system also has redundancies including boil off gas compressors, while each tank has a pump, so if one pump fails the other can be used to push LNG from one tank to another.  

Mr Liese said “There are possibilities to run the LNG system even if there are failures in it. But if the entire fuel gas system fails you always have back up to use oil instead of LNG for propulsion.”

The safety measures in the gas engineroom include gas detectors that can close tanks and sections of the gas supply to try and detect and repair the leakage, and which can lead to emergency shutdown if needed, as well as fire detectors. These were provided by TGE. Drip trays are placed under certain connection points designed to catch LNG if there is leakage, for example at the position of a flange.

Mr Liese added “The trays are equipped with temperature sensors and so once a temperature drops below a certain level you know there is a leakage and you can release emergency shutdown.”

LNG cannot touch normal steel so the trays are constructed from stainless steel that can endure the low temperatures of LNG.

TGE supervised the tank and gas supply system installation at Wenchong shipyard, observed the pre-commissioning and was present at the sea trials.

Mr Liese said “We spent a lot of time during pre-commissioning testing all parts of fuel gas system, explaining our system and doing onboard training for crew.”

LNG safety focus

Mr Bottino opened up on the safety considerations: The IMO’s Code for Gas Fuelled Ships (The IGF Code) requires risk assessments to be performed and typically a hazard identification (HAZID) supported by gas dispersion analysis and fire risk assessment.

These vessels are designed and are being constructed in accordance with IMO resolution MSC.285(86) 'Interim Guidelines on Safety for Natural Gas Fuelled engine Installations in Ships', which requires a risk assessment for each specific project. “The interim guidelines require a more thorough risk assessment for the whole design than the IGF Code, since the IGF Code limits the risk assessment requirement to items that are not specifically described within its requirements,” said Mr Bottino.   

The scope of the HAZID included the design and operations of the vessel, and bunkering operations.

He said “These studies cover the risk of gas and cryogenic releases in the engineroom as well as in the cargo area of the vessel. For container ships, one of the key challenges is congestion of the cargo area, which is stacked with containers. Special consideration must be given to locating and routing the fuel gas supply systems and bunkering areas as well as the location of any tank vents and safety vents.”

Energy efficiency elsewhere

Wärtsilä provided one auxiliary engine genset (six-cylinder in-line Wärtsila 20DF dual fuel), one CPP controllable pitch propeller, type Wärtsilä E1415and one PTO Wärtsilä shaft generator.

Indeed, it is not just using LNG that makes the vessel extremely energy efficient. The hullform was optimised through CFD calculations, with tank tests carried out by SVA Potsdam in Germany. Energy saving measures include a Becker full spade twisted rudder with rudder bulb.

The Containerships vessel also features a shaft generator with a controllable pitch propeller to supply the ship’s power while the main engine is running.

Mr Bottino said “The shaft generator is fitted at the output side of the main engine so that whenever the main engine is running to drive the propulsion shafting, the shaft generator can produce supplementary electrical power for use on board. As a result, the use of auxiliary engines can be minimised, reducing overall fuel consumption and operating costs.”

The ice-class 1A ship has high cargo carrying flexibility, mixing the loading of 20 ft, 40 ft and 45 ft containers.

As part of the agreement signed by Containerships and Shell, Shell will supply the LNG for Containerships’ LNG vessels via ship-to-ship bunkering at the Port of Rotterdam. All the newbuilds will be bunkered by Shell bunker vessels, including Cardissa.

The bunkering will be carried out at a normal operational berth simultaneously with loading and discharging operations. This means no disadvantages in operative efficiency will occur compared to traditional oil burning vessels.

Containerships is the first container shipping line in Europe to perform ship-to-ship bunkering with LNG.

 

 

 

 

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