[Federal Register: September 24, 1999 (Volume 64, Number 185)]
[Notices]               
[Page 51824-51825]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24se99-134]                         

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DEPARTMENT OF TRANSPORTATION

Research and Special Programs Administration
[Docket No. RSPA-99-5143; Notice No. 99-6]

 
Safety Advisory: Use of Aluminum Pressure Relief Valves on 
Portable Tanks and Cargo Tanks in Anhydrous Ammonia Service

AGENCY: Research and Special Programs Administration (RSPA), DOT.

ACTION: Safety advisory notice.

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SUMMARY: RSPA was recently advised of the use of aluminum pressure 
relief valves on portable tanks and cargo tanks that are used for the 
transportation of anhydrous ammonia which is not authorized by the 
Hazardous Materials Regulations (HMR; 49 CFR parts 171-180). The intent 
of this notice is to ensure safety and facilitate compliance with the 
HMR by clarifying applicable regulatory requirements pertaining to 
aluminum pressure relief valves.

FOR FURTHER INFORMATION CONTACT: Ms. Jennifer Karim, Office of 
Hazardous Materials Standards, telephone (202) 366-8553, Research and 
Special Programs Administration, Mr. Ronald Kirkpatrick, Office of 
Hazardous Materials Technology, telephone (202) 366-4545, Research and 
Special Programs Administration, or Mr. Danny Shelton, Office of Safety 
and Technology, telephone (202) 366-6121, Federal Highway 
Administration (FHWA).

SUPPLEMENTARY INFORMATION: The Research and Special Programs 
Administration (RSPA; ``we'') has been advised of the use of aluminum 
pressure relief valves on specification DOT 51 portable tanks, MC 330 
and MC 331 cargo tanks, and certain non-specification cargo tanks used 
in anhydrous ammonia service. The purpose of this advisory guidance is 
to remind persons who offer for transportation or transport anhydrous 
ammonia of their responsibility for meeting the applicable 
specification requirements of part 178, and the provisions for the use 
of portable tanks in Sec. 173.32(m), cargo tanks in Sec. 173.33(b), and 
general requirements for packaging and packages contained in 
Sec. 173.24(e)(1) and (2). The use of aluminum valves in anhydrous 
ammonia service may present a potential safety hazard due to the severe 
chemical attack/corrosion that may occur as a result of contact with 
anhydrous ammonia. The purpose of a pressure relief device is to 
discharge pressure to protect a tank from being over-pressurized. A 
corroded pressure relief device is not likely to perform its required 
function and may fail with a resulting release of anhydrous ammonia.
    The general compatibility requirement in Sec. 173.24(e) states that 
``packaging materials and contents must be such that there will be no 
significant chemical or galvanic reaction between the materials and 
contents of the package.'' We believe significant corrosion of aluminum 
pressure relief devices is a result of a chemical reaction with the 
anhydrous ammonia. This is particularly true when water has been added 
to anhydrous ammonia for carriage in quenched and tempered (``QT'') 
steel tanks as specified in Sec. 173.315(l).
    The use of aluminum valves on MC 330, MC 331 cargo tanks, and DOT 
51 portable tanks is specifically prohibited by Note 12 of the 
Sec. 173.315 Table. This is true also of non-specification tanks 
authorized by Note 17 of the Sec. 173.315 Table. For nurse tanks, 
Sec. 173.315 (m) provides an exception, but that

[[Page 51825]]

exception applies to part 178 provisions in regard to specification 
cargo tanks. It does not waive the requirements of Sec. 173.24(e) that 
are stated above.
    Persons who offer for transportation and transport anhydrous 
ammonia in cargo tanks and portable tanks should take immediate steps 
to ascertain if their safety relief devices comply with the HMR.

    Issued in Washington, D.C. on September 21, 1999, under 
authority delegated in 49 CFR part 106.
Alan I. Roberts,
Associate Administrator for Hazardous Materials Safety.
[FR Doc. 99-24899 Filed 9-23-99; 8:45 am]
BILLING CODE 4910-60-P