Hazardous Materials: Request for Feedback on Tare Weight Marking Policy for Cylinders (2024)

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Pipeline and Hazardous Materials Safety Administration (PHMSA), Department of Transportation (DOT).

Notice; request for information.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) is publishing this notice to solicit information pertaining to the current tare weight, mass weight, and water capacity marking requirements for compressed gas cylinders.

Interested parties are invited to submit comments on or before September 4, 2024. Comments received after that date will be considered to the extent possible.

You may submit comments identified by the Docket Number PHMSA-2023-0130 by any of the following methods:

• Federal eRulemaking Portal: http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: 1-202-493-2251.
• Mail: Docket Management System; U.S. Department of Transportation, West Building, Ground Floor, Room W12-140, Routing Symbol M-30, 1200 New Jersey Avenue SE, Washington, DC 20590.
• Hand Delivery: Docket Management System; Room W12-140 on the ground floor of the West Building, 1200 New Jersey Avenue SE, Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except federal holidays.

Instructions: All submissions must include the agency name and Docket Number (PHMSA-2023-0130) for this notice. To avoid duplication, please use only one of these four methods. All comments received will be posted without change to the Federal Docket Management System (FDMS) and will include any personal information you provide.

Docket: For access to the dockets to read background documents or comments received, go to http://www.regulations.gov or the Department of Transportation's (DOT) Docket Operations Office (see ADDRESSES ).

Privacy Act: In accordance with 5 U.S.C. 553(c), DOT solicits comments from the public. DOT posts these comments, without edit, including any personal information the commenter provides, to http://www.regulations.gov, as described in the system of records notice (DOT/ALL-14 FDMS), which can be reviewed at http://www.dot.gov/​privacy.

Confidential Business Information (CBI): CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this notice contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this notice, it is important that you clearly designate the submitted comments as “CBI.” Please mark each page of your submission containing CBI as “PROPIN.” Submissions containing CBI should be sent to Steven Andrews, Standards and Rulemaking Division, 202-366-8553, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, 1200 New Jersey Avenue SE, Washington, DC 20590-0001. Any commentary PHMSA receives that is not specifically designated as CBI will be placed in the public docket for this notice.

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Noah Jacobson by email at noah.jacobson@dot.gov, or Steven Andrews by email at steven.andrews@dot.gov or by phone at 202-366-8553.

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I. Purpose

PHMSA is publishing this notice to solicit input pertaining to the current tare weight marking requirements in the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180)—specifically, § 178.35(f)(8)—regarding DOT specification 4B, 4BA, 4BW, and 4E cylinders used in liquefied compressed gas service to determine what, if any, effect they may have on the safe transportation of hazardous materials.

II. Background

On May 1, 2009, the Compressed Gas Association (CGA) petitioned (P-1540 ^[1] ) PHMSA to revise § 178.35(f) to require DOT 4B, 4BA, 4BW, and 4E cylinders be marked with the tare weight or mass weight, and water capacity. Tare weight is the weight of the fully assembled cylinder, including the valve(s) and other permanently affixed appurtenances; mass weight is the weight of the fully assembled cylinder, excluding valve(s) and removable protective cap(s) or cover(s); and water capacity is the total volume of water the cylinder is capable of holding. The purpose of marking these measurements on the cylinder is to ensure that cylinders filled by weight, a method primarily used for liquefied gases like propane, are filled with the correct amount of material. The HMR requires that, for liquefied gases, the content of the cylinder be checked after filling by an “accurate scale”—see § 173.304a(c)—to avoid overfilling cylinders, which can cause cylinder rupture.

The CGA's petition requested that the markings be permitted to vary from the actual tare weight, mass weight, and water capacity of the cylinder to account for the accuracy of the stamped weight during manufacture. Specifically, the CGA's petition requested that for cylinders up to and including 25 pounds, the tare weight/mass weight marking be allowed a lower tolerance of three (3) percent and an upper tolerance of one (1) percent, while the tare weight/mass weight marking for cylinders larger than 25 pounds be allowed a lower tolerance of two (2) percent and an upper tolerance of one (1) percent. Similarly, the CGA's petition requested that water capacity tolerances for cylinders up to and including 25 pounds of −1 percent with no requirement for an upper tolerance, and for cylinders larger than 25 pounds of minus −0.5 percent with no requirement for an upper tolerance. In Start Printed Page 48483 practice, a three (3) percent tolerance in the lower bound equates to approximately 0.5 pound for typical consumer-sized propane cylinders with average stamped/stenciled tare weights between 16.6 pounds and 18 pounds ( i.e., a cylinder with a true tare weight of 17 pounds could be marked as low as 16.5 pounds).^[2]

The CGA's petition was accepted on July 23, 2009, and first addressed in the HM-234 Advanced Notice of Proposed Rulemaking (ANPRM) ^[3] titled “Hazardous Materials; Miscellaneous Amendments Pertaining to DOT Specification Cylinders (RRR).” In the ANPRM, PHMSA solicited data from the regulated community regarding the costs, benefits, and implications of the proposed cylinder markings on manufacturers, as detailed in the CGA's petition. PHMSA also sought data on alternative strategies to prevent overfilling accidents, as well as the safety advantages of the proposed markings. The goal of the ANPRM was to collect industry information to assess whether the proposed enhanced cylinder markings would offer safety benefits that justify the potential costs, particularly for small businesses.

In response to the ANPRM, commenters voiced concerns that mandating both tare weight and mass weight markings could lead to confusion among cylinder fillers due to potential discrepancies between the manufactured stamped weights. The commenters suggested that PHMSA refine the regulatory language to assign the marking of the tare weight specifically to the valve installer, given that some cylinders are not valved by the original manufacturer. The commenters also pointed out the limited space available for additional stamping on some cylinders that could affect the space for retest information. In summary, the commenters urged careful consideration of the language to prevent conflicting stamped weights, and to ensure the party best suited to mark the tare weight is clearly identified.

PHMSA then published the HM-234 NPRM ^[4] titled “Hazardous Materials; Miscellaneous Amendments Pertaining to DOT Specification Cylinders (RRR),” which proposed to revise § 178.35(f) to require marking the tare weight or mass weight, in addition to the water capacity, on DOT 4B, 4BA, 4BW, and 4E cylinders. The NPRM proposed to adopt the accuracy tolerances as presented in CGA's petition. PHMSA emphasized that while cylinder markings are crucial for safely filling liquefied compressed gas, they cannot replace comprehensive personnel training and procedures. These measures, along with ongoing requalification and maintenance of cylinders, are essential for preventing incidents. PHMSA subsequently expressed interest in receiving further comments on the possibility of extending this marking requirement to other DOT-specification cylinders, and was particularly interested in understanding the associated costs, benefits, and safety implications.

In response to the NPRM, PHMSA received comments opposing the proposed requirement to mark all DOT 4B, 4BA, 4BW, and 4E cylinders with tare weight or mass weight, and water capacity. These commenters cited concerns about the challenges and costs of implementing the proposal. In particular, commenters noted that while many DOT 4B, 4BA, 4BW, and 4E cylinders are used for liquefied gases, some are used in non-liquefied gas services, such as fire extinguishers, and these markings do not serve a useful purpose for a cylinder filled by pressure. Other commenters were generally supportive of the proposed revisions and reflected a range of perspectives on the costs, benefits, and potential unintended consequences of the proposed marking requirements. PHMSA received no comments related to existing tare-weight marking standards for consumer cylinders mandated by states.

PHMSA then published the HM-234 final rule ^[5] to revise certain requirements applicable to the manufacture, use, and requalification of DOT 4B, 4BA, 4BW, and 4E cylinders. Prior to this revision in the HM-234 final rule, the HMR did not contain any requirement for liquefied compressed gas cylinders that are filled by weight to be marked with a tare weight, mass weight, or water capacity. PHMSA determined that these cylinder measurements are critical for liquefied compressed gases, which are filled by weight, rather than by pressure. Improperly filled liquefied gas cylinders ( i.e., overfilled cylinders) have contributed to significant hazardous materials incidents, including the 2014 Philadelphia, Pennsylvania, food truck explosion.^[6] The HM-234 final rule revised the NPRM's proposal and imposed the tare weight or mass weight, and water capacity marking requirements to only apply to DOT 4B, 4BA, 4BW, and 4E cylinders used for liquefied compressed gases, an adjustment made in response to the comments in the NPRM. PHMSA received no comments regarding the accuracy tolerances proposed in the NPRM, and the final rule adopted them as proposed.

On January 23, 2023, PHMSA received a petition for rulemaking (P-1772) ^[7] from the National Council on Weights and Measurements (NCWM) requesting that PHMSA reconsider the allowable differences on stamped tare weight verses actual tare weight for liquefied petroleum gas (LPG) cylinders. In their petition, NCWM recommends a ±0.5 percent tolerance between actual and marked TW/MW for cylinders weighing 25 pounds or less, with an additional requirement that “good quality control practices” be followed. This tolerance is significantly tighter than the accuracy tolerances adopted in the HM-234 final rule ( i.e., 6x less variance is permitted in the tare weight/mass weight marking for a cylinder weighing less than 25 pounds).

The NCWM also suggested that the stamped tare weight on “used” cylinders be verified periodically to ensure accuracy. Additionally, the NCWM recommends that the allowable difference between the stamped tare weight verses the actual tare weight for cylinders more than 25 pounds be reviewed and be based on data. Finally, the NCWM suggests that the current edition of the National Institute of Standards and Technology (NIST) Handbook 44 ^[8] be incorporated by reference for the marking and weighing of cylinders to be filled with liquefied petroleum gas. NCWM also requests that PHMSA add an “Average Requirement” to the tare weight regulations to improve measurement accuracy and production controls, and to ensure a business is not using the allowable differences to gain a competitive advantage. The NCWM proposes the “average requirement” to mean “when used to determine the net contents of cylinders, the stamped or stenciled tare weights of cylinders at a single place of business found to be in error predominantly in a direction favorable to the seller and near the allowable difference limit shall be considered to be “not in conformance with these requirements.”

PHMSA requests feedback from the public on the current regulation as Start Printed Page 48484 adopted in the HM-234 final rule, and on the proposed provisions in the NCWM petition.

III. PHMSA's Current Tare Weight Marking Requirement for Cylinders

The HMR mandates in § 178.35(f) that DOT 4B, 4BA, 4BW, and 4E cylinders—used for liquefied compressed gases—be marked with either tare weight or mass weight, in addition to the water capacity. For cylinders weighing 25 pounds or less at the time of manufacture, a variance is permitted with a lower tolerance of three (3) percent and an upper tolerance of one (1) percent. For cylinders weighing more than 25 pounds at the time of manufacture, a variance is allowed with a lower tolerance of two (2) percent and an upper tolerance of one (1) percent. If mass weight marking is chosen over tare weight marking, the same variance tolerances apply based on whether the manufacturing mass exceeds or is at or under 25 pounds.

IV. Request for Feedback

PHMSA requests comment on the following questions to better inform potential regulatory revisions. For all questions, please explain your answers and provide any economic, technical, or other information available to you as justification for your response:

1. Do you believe the current language for the marking of DOT cylinders in § 178.35(f)(8) leads to confusion between marked tare weight at the time of manufacture and the stamped tare weight for the filling of cylinders?

2. How should PHMSA revise the requirements in § 178.35(f)(8) for marking of tare weights on DOT 4B, 4BA, 4BW, and 4E cylinders used in liquefied compressed gas service?

3. What impact would PHMSA incorporating the current edition of NIST Handbook 44 for scales used to weigh cylinders containing liquefied compressed gases have on ensuring accurate scales in both direct sale applications and for prepackaging liquefied compressed gas cylinders in advance of sale?

4. What would be the impacts of PHMSA adding an “average requirement” to the tare weight regulations in § 178.35(f)(8) to improve measurement accuracy and production controls, and to ensure a business is not using the allowable differences to disadvantage consumers while at the same time maintaining safety compliance?

5. What would be the impacts of PHMSA reconsidering the allowable differences on stamped tare weight as opposed to actual tare weight and applying a ±0.5 percent tolerance for cylinders 25 pounds or less? How would PHMSA define a requirement to follow “good quality control practices” as suggested in the NCWM petition?

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