[Federal Register Volume 77, Number 188 (Thursday, September 27, 2012)]
[Pages 59408-59409]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-23772]



Coast Guard

[Docket No. USCG-2012-0804]

Finding of Equivalence; Alternate Pressure Relief Valve Settings 
on Certain Vessels Carrying Liquefied Gases in Bulk

AGENCY: Coast Guard, DHS.

ACTION: Notice of availability.


SUMMARY: The Coast Guard announces the availability of 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.'' Existing Coast Guard regulations regarding the allowable 
stress factors for type B and type C independent cargo tanks are more 
stringent than the International Maritime Organization (IMO) standards 
for such cargo tanks. Materials, manufacturing, and inspections have 
advanced since the Coast Guard first promulgated regulations on 
allowable stress factors on May 3, 1979. CG-ENG Policy Letter 04-12 
establishes that for certain type B and type C independent cargo tanks 
that are designed and manufactured using advanced techniques, the IMO 
standards for allowable stress factors provide a level of safety 
protection equivalent to the standards in 46 CFR 154.447 and 46 CFR 

DATES: CG-ENG Policy Letter 04-12 is effective as of September 27, 

ADDRESSES: This notice and the documents referenced within are 
available in the docket and can be viewed by going to 
www.regulations.gov, and using ``USCG-2012-0804'' as your search term. 
CG-ENG Policy Letter 04-12 is also available at www.uscg.mil and can be 
viewed by clicking the link to the Office of Design and Engineering 
Standards (CG-ENG) under the ``Units,'' ``USCG Headquarters 
Organization,'' and ``CG-5P'' tabs, and scrolling down to ``Policy 

FOR FURTHER INFORMATION CONTACT: If you have questions on this notice, 
call or email Cynthia A. Znati, CG-ENG-5, U.S. Coast Guard; telephone 
(202) 372-1412, email Cynthia.A.Znati@uscg.mil.

[[Page 59409]]

If you have questions on viewing material in the docket, call Renee V. 
Wright, Program Manager, Docket Operations, telephone (202) 366-9826.


Background and Purpose

    The IMO first adopted the International Code for the Construction 
and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) on 
November 12, 1975. The current version of the IGC Code is the 1993 
Edition, as amended through December 5, 1996. On May 3, 1979, the Coast 
Guard promulgated regulations based largely on the IGC Code, but 
adopted the stricter standards of the American Society of Mechanical 
Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Section VIII 
with respect to allowable stress factors. Coast Guard regulations in 46 
CFR 154.447 and 154.450 regarding allowable stress factors for type B 
and type C independent cargo tanks have remained unchanged since May 3, 
    Coast Guard regulations in 46 CFR 154.447 and 154.450 require that 
self-propelled ships carrying liquefied bulk gases in type B and type C 
tanks use stress factors that are higher than those in the IGC Code. 
The higher stress factors lead to lower maximum allowable relief valve 
settings (MARVS) than are allowed by the IGC code. Accordingly, ships 
with type B or type C tanks that travel from international waters to 
U.S. territorial waters must have two pressure relief valve (PRV) 
settings per tank, and they must switch PRV settings upon entering U.S. 
territorial waters. We believe that in many cases, switching between 
these two PRV settings is not necessary for safety purposes.

Finding of Equivalence

    According to 46 CFR 154.32, vessels may meet an alternate standard 
if the Commandant determines that the alternate standard provides an 
equivalent or greater level of protection for the purpose of safety. We 
recognize that advances have been made with respect to materials, 
manufacturing, and inspection since we first promulgated 46 CFR 154.447 
and 154.450. Therefore, as specified in CG-ENG Policy Letter 04-12 and 
below, we have determined that for tanks designed and manufactured with 
advanced techniques, the stress factors in the IGC Code provide a level 
of safety equivalent to current Coast Guard regulations.
    Tanks manufactured consistent with certain conditions are 
considered to meet the level of safety required in 46 CFR 154.447 and 
154.450. Tanks that meet the following two requirements may use the 
MARVS as determined by the IGC Code:
    (1) The tank must be designed and built according to the IGC code, 
1993 Edition, including all amendments through December 5, 1996; and
    (2) The classification society that certified the tank must be 
authorized to issue an International Certificate of Fitness for the 
Carriage of Liquefied Gases in Bulk (Certificate of Fitness) and must 
be authorized to participate in the Coast Guard's Alternate Compliance 
Program. See http://www.uscg.mil/hq/cg5/acp/ for further information.

Tanks that do not meet both of these requirements must comply with 
current Coast Guard regulations in 46 CFR 154.447 or 154.450. 
Alternatively, persons may request approval from the Commandant (CG-
ENG-5, formerly CG-522) to use an alternate pressure relief valve 
setting for such tanks. Equivalency requests must include the 
information required in 46 CFR 154.32(b) and should also include a copy 
of the Certificate of Fitness.
    The guidance in this notice and CG-ENG Policy Letter 04-12 is not a 
substitute for applicable legal requirements, nor is in itself a 
regulation. It is not intended to nor does it impose legally-binding 
requirements on any party. It represents the Coast Guard's current 
thinking on this topic and may assist industry, mariners, the general 
public, and the Coast Guard, as well as other federal and state 
regulators, in applying U.S. statutory and regulatory requirements.
    This notice is issued under authority of 46 U.S.C. 3703, 46 U.S.C. 
9101, 5 U.S.C. 552(a), 46 CFR 154.32, and 33 CFR 1.05-1.

    Dated: September 13, 2012.
J.G. Lantz,
Director of Commercial Regulations and Standards, U.S. Coast Guard.
[FR Doc. 2012-23772 Filed 9-26-12; 8:45 am]