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May 23, 2005
Natural gas
The western world's need for power and the fuel to generate it is creating the need for ever more ingenious ways to get the fuel from the source - in this case the Persian Gulf - to the end user. The ship in the picture below is one such solution. She carries up to 135,000 cubic metres of liquified natural gas in her specially designed and insulated tanks. In order to keep the gas liquid you have to do one of two things to it - place it under enormous pressure - or refrigerate it. There is only one more problem - how to get it down to -146 degrees Celsius!
A large LNG carrier loading liquified natural gas at a facility in the Gulf.
The gas can be contained in the ship's tanks only as long as it remians refrigerated, the tanks will vent off the gas if the pressure rises due to a change in state or temperature, and LNG is quite volatile. Unlike Liquified Petroleum Gas (LPG), which is relatively easy to store under pressure, the nature of LNG makes it necessary to hold it under much higher pressures - or chill it to its liquifaction point, which just happens to be around MINUS 140 degrees Celsius. At this sort of temperature most metals start to get very brittle - in fact, at these temperatures you and I would freeze solid in seconds!
The ships are constructed to take account of this, and the tanks are heavily insulated and multi-skinned as well. To ensure that the refrigeration system doesn't fail they are fitted with two, one taking over if the other fails. As you would expect there are also a full range of fire defence systems fitted to the ship, and many of these can be remotely operated if necessary. The ship's structure is also heavily protected to ensure that the crew can evacuate safely before anything penetrates to the crew spaces, and there are multiple alarm systems fitted to warn of gas leaks and failures of the structure.
A new generation of these ships is being built as I write, and we will soon, in Europe, be hosting these as they increasingly carry our fuel to terminals along our coasts. This new generation carry over 150,000 cubic metres of LNG, each, and will become increasingly common sights in our harbours as our own North Sea gas supplies dwindle.
Perhaps the sight of them in some ports will occassion a rethink on the nuclear power debate!
Posted by The Gray Monk at May 23, 2005 08:03 AM