Seeing this huge metal tank in the picture, I believe many people know that this is an LNG, that is, a liquefied natural gas carrier. You may have seen a lot of pictures of the LNG ship , but a disintegrating LNG ship is still quite strange. It turns out that its internal structure is like this.
The LNG ship being dismantled is still quite rare
For the shipbuilding industry, there are three types of ships that are the most technically difficult and the most difficult to build. They are aircraft carrier , luxury cruise ship and LNG ship . The first two are easy to understand, because one of them concentrates the most advanced military technology, and the other concentrates the most luxurious decoration, so it is difficult. But what is so difficult about an LNG ship that transports liquefied natural gas?
What is the difficulty of LNG ship?
First of all, natural gas is a gas with light weight and large volume. If the gaseous natural gas is directly transported by ships, the cost will be unacceptably high. Therefore, the natural gas must be compressed 600 times and turned into a liquid for convenient transportation. There are two ways to turn natural gas into a liquid. One is to use 600 times the atmospheric pressure to depress it, which is too difficult; the second is relatively simple, which is to lower the temperature to -163°C.
LNG ship
So in a strict sense, an LNG ship is a floating refrigerated warehouse, but this floating refrigerated warehouse transports explosive and dangerous goods, and marine transportation usually takes dozens of days. , Even for a few months, if it leaks, the consequences will be disastrous. Therefore, it has high requirements on the materials used to construct the cold storage, such as low thermal conductivity, small expansion coefficient, high plasticity and high toughness.
not only that,Due to cost considerations, ship owners always hope that the heavier the cargo they load, the better, and the lighter the ship, the better. The easiest way to make the ship lighter is to make the steel plate thin. It is said that the thickness of the invar steel used for the cold storage of the LNG ship is only 0.7 mm, just like a piece of paper. Even if a drop of sweat drips on it, the steel plate will be rusted. However, such thin, high-toughness Invar steel plate is very difficult to process, and it was only a few years ago that my country broke through this technology.
Of course, you can also not liquefy natural gas, but compress it 100 times, which can also save transportation costs. This type of natural gas carrier is called CNG, which is a compressed natural gas ship. It can be transported at room temperature, does not require steps such as liquefaction and regasification, and does not require special berthing devices. It is simple to operate. However, due to the large volume of natural gas and the heavy weight of empty ships, the cost of returning without load is almost the same as that of full load. Long-distance transportation is not economical. Moreover, the cost of CNG is relatively high, with a single cost of US$200 million.
CNG ships are not seen much
And our common large tank type LNG carriers are actually just a classification of LNG, it is called MOSS spherical tank type LNG, and it is also parallel to it. There are membrane type LNG. In 2000, the spherical tank type accounted for about 50% of the global LNG ships in operation, and the membrane type accounted for 46%. However, as LNG ships are becoming larger and larger, only 32% of new LNG ships under construction in 2003 used spherical tank systems, while membrane types accounted for 62%.
Two types of LNG ships
The disadvantages of the spherical tank system are the low utilization rate of the cabin, the large size of the ship, and the high construction cost. For large-capacity tanks, all manufacturing and molds must be updated, resulting in cost It climbs further, but its advantages are long life, no sloshing problems, strong structure, can be used for emergency unloading, and it is not easy to damage the tank in the event of a collision. This is beyond everyone's expectation.
Generally speaking, there should be many accidents when transporting dangerous goods like natural gas.Be very careful. But in fact, there have been nearly 100,000 successful loadings in the industry, and there has been no leakage accident caused by damaged liquid cargo tanks. When an LNG ship collides with another LNG ship of the same size at a speed of 12 kilometers per hour, it can still guarantee that there will be no LNG leakage when it capsizes at 90 degrees. Such collisions are very rare, so The safety of LNG ships is still very high.
However, if a fully loaded LNG is ignited and exploded, its power is also very huge, which is said to be dozens of times the Hiroshima atomic bomb. Fortunately, no such disaster has occurred yet.
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