What is a LNG Offloading System
Liquefield natural gas (LNG) is an odourless and flammable natural gas that is typically transported in the ships, primarily designed for this purpose. In order to transport the LNG safely through the water, the ships require to meet specific technical considerations, which would also include specific loading and offloading systems. The offloading LNG systems are considered as absolutely necessary components to support safe transportation of the gas from the ship to the system-base.
Depending on the brand and the construction choice, the hose can either be located above or below the water level. Aerial hoses can only offload LNG, while being connected to the ship and the tower-based or tandem-based offloading LNG systems above water. Diameter of such hoses can be or around 16” and its length can range up to 40 metres. Aerial hoses can include from 1 to 3 gas hoses as well as 1 vapour return hose. By its construction, the Aerial offloading hoses cannot be inserted into the water. Aerial offloading LNG hoses are considered to be a traditional way of offloading LNG. In general, around 5,000 m3 of the gas can be offloaded per hour.
In particular, the offoading system for LNG is an expedient technological construction, which enables the ship to release the LNG safely onto the system in order of transferring it to the shore. Typically, LNG offloading systems presents itself as a large metallic tower, which is situated in the sea or ocean and is protruding and rising high above the water level. However, LNG offloading systems can also be tandem-based and located on LNG terminal base. The tandem-based LNG systems, which are equipped with traditional aerial hoses tend to locate hose reels sufficiently high to support safe air-base LNG discharge. Such tandem-based systems tend to have hose reels located at the loading end of the base. Such tandem-based aerial-hosed LNG systems can support 80 metres distance between the carrying ship and the base and support the transportation of the gas during stormy weather conditions, reaching 4.5 metres of wave heights.
Alternatively, newer floating LNG hoses can be safely inserted into the water. The floating LNG hoses are considered to present a more advanced, safer and faster offloading system with lover pressure drop rates as well as promoting lower heat rate. Other improved features of the floating-hose system would include increased distance from 80 metres to 100 metres and more between LNG carrying vessel and LNG offloading system base. Improved safety of the transportation due to the increased adaptation to the various sea conditions, which support wave heights up to 4 m.
Regardless of the design and construction differences, LNG offloading systems discharge the gas through a flexible, durable and safe transfer hose technology. In general, appropriately fitted LNG hoses would require to undergo pressure tests, leak monitoring, fatique tests, be checked for possible damage, burst tests and other. To assure proper and ethical usage, aerial hoses as well as the floating hoses would need to undergo proper maintenance and tests on regular basis.