The U.S. Coast Guard (USCG) published the CG-ENG Policy Letter 04-12, “Alternative Pressure Relief Valve Settings on Vessels Carrying Liquefied Gases in Bulk in Independent Type B and Type C Tanks.”
This new policy allows type B or C gas carriers to operate within the US with the IMO Maximum Allowable pressure Relief Valve Setting (i.e. no more with the special lower USCG setting) provided their cargo tanks meet the following:
Existing USCG regulations regarding the allowable stress factors for the subject types of tanks have been in place since May 3, 1979. Coast Guard regulatory standards in this regard are stricter than International Maritime Organization (IMO) standards. The Coast Guard recognizes that there have been technological advances since 1979 with respect to the materials and manufacturing of such tanks. Based on these advances, the USCG determined that for certain type B and type C independent cargo tanks which are designed and manufactured using advanced techniques, the IMO standards for allowable stress factors are sufficient.
[mappress] LNG World News Staff, November 08, 2012; Image: USCG