Safety Advisory Notice; Use of Non-Complying Portable Tanks for Transportation of Propane

AGENCY:

Research and Special Programs Administration (RSPA), DOT.

ACTION:

Safety advisory notice.

SUMMARY:

This safety advisory notice is to make persons aware of safety concerns related to the intermodal transportation of propane in portable tanks and of the proper packaging requirements for such transportation. RSPA has become aware of several instances where propane was improperly transported in portable tanks. This suggests that some persons who offer or transport propane in portable tanks may not be fully aware of the applicable requirements of the Hazardous Materials Regulations. This notice alerts offerors and transporters to potential safety problems and summarizes the proper packaging requirements for offering or accepting propane in portable tanks for transportation.

FOR FURTHER INFORMATION CONTACT:

Diane LaValle, Office of Hazardous Materials Standards, RSPA, Department of Transportation, 400 Seventh Street, SW., Washington, DC 20590-0001, Telephone (202) 366-8553.

SUPPLEMENTARY INFORMATION:

I. Background

The U.S. Coast Guard has identified problems with certain portable tanks used to transport propane in and between the states of Washington and Alaska. It appears that many of the portable tanks in this service may not conform to the requirements of the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180) and to requirements for approval and inspection of cargo containers (49 CFR parts 450-453). Some of the deficiencies identified may pose a significant safety threat.

On March 17, 2000, a SeaLand/CSX cargo vessel transporting over 6,000 gallons of propane in a portable tank encountered rough seas. The portable tank broke loose from its frame, damaging its external piping and releasing over 100 gallons of propane. Although the release of propane in this incident was relatively small, the potential for a catastrophic incident involving the bulk transportation of propane on board vessels should not be minimized. A significant release of propane, coupled with a fire or explosion, would place the crew and the vessel at serious risk.

Subsequent inquiries and investigations by RSPA's Offices of Hazardous Materials Enforcement and Hazardous Materials Technology, the Federal Motor Carrier Safety Administration, and the U.S. Coast Guard identified several potential problems with portable tanks used for the intermodal transportation of propane. These problems involve improper mounting of portable tanks to container frames, substandard welds where portable tanks are attached to container frames, overfilling, improperly modified cargo tanks, and invalid specification packaging markings. Preliminary indications are that such deficiencies may affect a significant number of portable tanks in intermodal propane service. An initial industry estimate is that perhaps 60 percent of 500 portable tanks involved in this transportation may not conform to HMR requirements. Because these tanks are used in intermodal service, the potential safety problems could affect highway and rail transportation, in addition to transportation by vessel.

II. Requirements for the Transportation of Propane in Portable Tanks

Section 173.315 of the HMR authorizes the transportation of propane in a number of bulk packagings, including DOT Specification 51 portable tanks. Specifications for the design and manufacture of DOT Specification 51 portable tanks are in Subpart H of Part 178 of the HMR.

Design and construction. Generally, DOT 51 portable tanks must be designed, constructed, certified, and stamped in accordance with the ASME Code in effect at the time the tank is constructed (see § 178.245-1). Welds used in tank construction, as well as welding procedures and weld performance tests, must conform to the ASME Code (see § 178.245-1(b)). The regulations also include specific requirements for tank openings and filling and discharge connections (see § 178.245-1(d)). Among other requirements, each filling and discharge connection below the normal liquid level of the tank must be equipped with an internal self-closing stop valve capable of closing within 30 seconds of actuation.

The regulations for DOT 51 portable tanks also include specific requirements applicable to materials of construction (§ 178.245-2), design pressure (§ 178.245-3), mountings (§ 178.245-4), and damage protection (§ 178.245-5).

A DOT 51 portable tank that meets the definition of a “container” in 49 CFR 450.3(a)(2) must also conform to the requirements of 49 CFR parts 450 through 453 for compliance with Annex II of the International Convention for Safe Containers, particularly with regard to attachment of the portable tank to its intermodal frame (see § 178.245-1(d)(4)(i) and 178.245-4(e)). Parts 450 through 453 establish requirements and procedures for safety approval and periodic examination of cargo containers. Portable tanks that meet the definition of “container” for purposes of Parts 450 through 453 must be inspected by an agency that has been approved by the US Coast Guard. As defined in 49 CFR 450.3(a)(2), a “container” is an article of transport equipment that: (1) Is suitable for repeated use; (2) is designed to facilitate the transport of goods by one or more modes of transport without intermediate reloading; (3) is designed to be secured and readily handled with corner fittings for these purposes; and (4) has an area enclosed by the bottom four corners that is at least 150 square feet or 75 square feet if it has top corner fittings.

Periodic inspections and tests. Portable tanks used for the transportation of hazardous materials must undergo periodic inspections and tests to assure the continued integrity of the tank and its appurtenances. The requirements for periodic inspection and testing of DOT 51 portable tanks are in § 173.32(e). Every five years, a DOT 51 portable tank must successfully pass a pressure test that conforms to the requirements in § 173.32(e)(2)(i) and a visual inspection that conforms to the requirements in § 173.32(e)(2)(ii). The date of the most recent periodic test and inspection must be marked on the tank on or near its certification plate. A portable tank for which the prescribed tests or inspections have become due may not be filled and offered for inspection until the test or inspection has been successfully completed.

Cargo tank conversions. It is possible, though difficult, to modify a cargo tank, such as by using the tank from an MC 330 cargo tank motor vehicle, to meet the DOT 51 portable tank specification. The modification must be performed by an ASME Code facility. The manufacturer performing the modification must assure that the modified tank conforms to all the requirements of the DOT 51 specification in § 178.245 of the HMR. Such a tank no longer meets the cargo tank specification; thus, the manufacturer must remove or cover the cargo tank specification plate on the modified tank and affix a new certification plate in accordance with § 178.245-6. Other than through recertification as a portable tank, there is no provision for use of the tank from a cargo tank motor vehicle as a portable tank.

Filling densities. The HMR prescribe maximum permitted filling densities for portable tanks in propane service in § 173.315(b). Generally, maximum permitted filling densities depend on the specific gravity of the material to be transported, measured at 60°F, and the size of the tank. Propane in a portable tank may not exceed 60 percent of the water-weight capacity of the tank.

III. Safety Implications

The purpose of this safety advisory notice is to alert persons who offer or transport propane that transporting propane in portable tanks that do not conform to the HMR could have serious safety implications for persons who handle or transport such tanks and for the general public. When liquid propane is released into the atmosphere, it quickly vaporizes into the gaseous form that is its normal state at atmospheric pressure. Vaporization occurs very rapidly and, in the process, the propane combines readily with air to form fuel-air mixtures that are ignitable over a range of 2.2 to 9.5 percent by volume. If an ignition source is present in the vicinity of the highly flammable mixture, the vapor cloud ignites and burns explosively.

No person may offer for transportation or transport hazardous materials except in conformance with the HMR. Persons offering or transporting propane in portable tanks that do not conform to the HMR requirements may be subject to civil or criminal penalties.