Ship to ship LNG transfer technology
The LNG market is continuing to expand at a rate of knots, with orders for new LNG ships to be built still providing a strong income, when the rest of the maritime industry is having a downturn in trade and orders for new builds. The LNG ships that are being ordered and built are getting bigger all the time. The largest LNG ship to date has a carrying capacity of 266,000 cubic metres of LNG gas, however the vessel herself has a summer draft of 12m. What does this mean? In a nutshell, it means that the trend of building vessels with a larger cargo capacity and larger drafts cannot get into the shallower ports that their smaller counterparts can. If a vessel can get into port, it maybe a case of waiting for the high tides and the times waiting to load and discharge cuts into the vessel’s profitability. This is where the trade off between the larger ships which can carry the maximum amount of cargoes and getting into the smaller ports comes into, the perfect balance of is the use of LNG ship to ship transfer.
So how are LNG ship to ship transfers conducted?
The current practice of LNG ship to ship transfer is conducted by both vessels being held in position against each other, whilst cargo is transferred via flexible hoses. There are many LNG ship to ship transfer operations taking place worldwide on a daily basis, with accidents and incidents being very low frequency. However, there is a risk due to various different factors, that there could be a cargo spill. There are numerous advances in technology that are taking into account the risks and managing these risks to make the LNG ship to ship transfer process safer.
What advances in LNG ship to ship transfer technology are there?
There are two main components of emergency release systems, which are a combination of different systems, to safeguard the ship and the environment, in the even of an emergency. A system which is fitted with emergency release system provides a managed close-down system, so should an emergency happen, the ship’s crew have full control of the situation and can isolate the cargo system and operations in the event of an emergency. All vessels are required to safeguard the environment as far as possible and to prevent cargo spills wherever possible and an emergency release system is one way of doing this as it protects the ship, cargo hoses and all associated cargo handling equipment.
Emergency Release Coupling (ERC)
The latest advance in technology for ship to ship transfer is providing a safe point, or weak link in the system, meaning that in the event of an emergency, the crew know exactly what the system will do and where it will part. This weak link of an LNG transfer system is designed to be the Emergency Release Coupling, which is part of the wider emergency release system, which is the safety point or weak link within the LNG transfer line. Should say the ships break away from each other unexpectedly, The Emergency Release Coupling is designed to close down the LNG system, separate the lines between the two ships and to ensure the LNG flow is safe should an emergency occur.
LNG Hydraulic Power Units
LNG HPUs are the cutting edge in technology and safety systems and for those using a full safety release system, for ship to ship transfer, then the HPU provides another fail safe option. The first point to note in a HPU system is that they often offer the designated crew a single point of control over the Emergency Release System, so should an emergency release coupling be activated for something other than hose line stress, the system can be reset by the operator, meaning cargo transfer can continue.
Another interesting advance in technology is the HPU can have different sets of variables, meaning the unit can release the couplings dependent on each individual scenario and the parameters that have been set. Advances in technology now mean that one HPU can actually control a full system of up to ten emergency release couplings, meaning the operator has less systems to check and can have one point of reference.
With advances in technology, this is the technology that is currently available on the market and being used with success by a number of vessels, however, there are likely to be further advances to the emergency release systems over coming years.
For further information on lng transfers read lng ship to ship transfer guidelines pdf