CNG (Compressed Natural Gas) carrier
New concept of fully-pressurized gas carrier fitted with steel pipes used as pressure vessels. Different from the LNG tanker that maintains LNG in liquefied form at -163°C at near atmospheric pressure, the CNG carrier will transport the cargo in a gaseous state at temperature down to -29°C, and at pressure from 130 bar to 250 bar, depending on the precise design.
Further reading: ABS Guide for “Vessels Intended to Carry Compressed Natural Gas in Bulk” (2005), can be downloaded from www.eagle.org
DNV developed throughout 2002 rules for CGN carriers that were issued in January 2003 and came into force July 1rst 2003. The DNV CNG rules set strict requirements for the protection of the cargo tanks from damages due to collision and/or grounding. Without compromising on safety, the use of DNV submarine pipeline standard reduces the steel weight of the cylinders to 50% of what should have been necessary with the requirements of the International Gas Code. It has been shown that the probability of burst is less than 10-6 per year and the probability of fatigue failure is less than 10-5 per year for a typical CNG carrier with up to 3900 pipes of total length of 150km.