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Natural gas, like oil, is produced from gas fields that are often far
from the consuming custormer. While pipelines, both on land and in the
sea, can deliver the gas in gaseous form, over relatively short distances,
another means to transport the gas in larger quantities over longer distances
is required. The most effective and practical way to transport gas between
continent is in liquid form by ships. Ships have been designed and built
to transport liquefied gases since the 1920s.
In general terms, a liquefied gas is the liquid form of a substance,
which at normal ambient temperature and atmospheric pressure would be
gaseous. Typical liquefied gases transported over sea are
| name |
atmospheric boiling point
BP (°C) |
liquid density at BP
(kg/m3) |
vapor pressure at 45°C
(Mpa absolute) |
ship type by IMO code |
| ammonia (anhydrous) |
-33,4 |
681 |
1.78 |
2G/2PG |
| butadiene |
-5 |
650 |
0.51 |
2G/2PG |
butane
n-
i- |
-0.5
-11.7 |
601
595 |
0.43
0.52 |
2G
2PG |
| chlorine |
-34.6 |
1557 |
0.126 |
1G |
| ethane |
-89 |
546.7 |
5.4 |
2G |
| ethylene |
-103.7 |
570 |
4.24@0ĄC |
2G |
| methane |
-161.5 |
425 |
4.21@-86ĄC |
2G |
| propane |
-42.1 |
583 |
1.57 |
2G/2PG |
| propylene |
-47 |
606 |
1.87 |
2G/2PG |
| vinyl chloride |
-13.7 |
965 |
0.68 |
2G/2PG |
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The gases are liquefied, by subjecting them to pressure and/or low temperature.
The carriage of liquefied gases in bulk began by transporting pressurized
butane and propane in the late 1920s, and subsequently refrigerated and
pressurized liquefied gas carriers were in service through the development
of refrigeration techniques and materials suitable for containment at
low temperature. By the mid- 1960s liquefied gas carriers with refrigerated
LPG at atmospheric pressure were in service, ethylene and LNG carriers
had also entered srvice. In the meantime ammonia had become a common cargo,
and chemical gases such as butadiene also became commercialy important.
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