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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #17-0035

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name:

Individual Name: Mr. Jared Sherman

Location State: FL Country: US

View the Interpretation Document

Response text:

November 16, 2017
Jared Sherman
4940 E Sabal Palm Boulevard # 401 Tamarac, FL  33319
Reference No. 17-0035
Dear Mr. Sherman:
This letter is in response to your April 6, 2017, e-mail requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the requalification of cylinders.  Specifically, you ask about filling a Department of Transportation (DOT) cylinder in excess of 10 percent in accordance with § 173.302a(b).  You provide an example of a DOT 3AA cylinder that was marked with a service pressure of 3,000 psi and a plus (+) at the time of manufacturing.
We have paraphrased and answered your questions as follows:
Q1.      You ask for confirmation of your understanding that a cylinder with a service pressure of 3,000 psi is allowed to use a service pressure of 3,300 psi, provided the cylinder passes hydrostatic inspection at the 3,300-psi rating.
A1.      Your understanding is incorrect.  A DOT 3AA cylinder may be filled with a Division 2.2 non-flammable, non-liquefied gas to 10 percent in excess of its marked service pressure if all requirements contained in § 173.302a(b)(1) through (5) are met.  The plus sign (+) is marked on a cylinder to indicate compliance with the testing and evaluation requirements in § 173.302a(b)(2) through (4).
For requalification of a cylinder previously marked with a plus sign, the hydrostatic retest must be performed using the water jacket method to determine the cylinder’s elastic expansion (see § 173.302a(b)(2)).  The cylinder requalifier must know the elastic expansion rejection (REE) value to ensure the cylinder's average wall stress or the maximum wall stress does not exceed the wall stress limitation specified in § 173.302a(b)(3).
Q2.      You ask whether any hydrostatic test shop can apply the plus (+) rating, or if the rating must be applied by the manufacturer.
A2.      The initial plus sign marking is typically applied by the manufacturer.  A cylinder requalifier may apply subsequent plus sign (+) markings.  Both the manufacturer and requalifier must ensure the conditions of § 173.302a(b)(2) through (4) are met in order to mark the plus sign.  Only a plus sign (+) marked after the last (most recent) test or retest date applies to determine whether the cylinder can continue to be filled to 10 percent in excess of its marked service pressure.  The HMR contain no limitations on the number of times a cylinder that meets the requirements in § 173.302a(b) may be marked with a plus sign. 
Q3.      You ask whether DOT keeps REE information on file for DOT 3AA cylinders.
A3.      DOT neither collects nor maintains REE values or other information from the manufacturer's design for DOT specification cylinders.  Manufacturers of DOT cylinders comply with the recordkeeping requirements specified in § 178.35.  Requalifiers of DOT cylinders comply with the recordkeeping requirements specified in § 180.215.
Q4.      You ask whether the test facility or owner may stamp the REE value on a cylinder using the test log data obtained by following the Compressed Gas Association (CGA) Pamphlet C-5 to determine allowance to fill a cylinder to 10 percent in excess of its marked service pressure.
A4.      Only the manufacturer is authorized to apply the REE marking on a cylinder.  If the manufacturer did not mark the REE number, then the requalifier must either use the tabulated data or compute the limit using CGA Pamphlet C-5.  See the final rule titled, "Hazardous Materials: Requirements for Maintenance, Requalification, Repair and Use of DOT Specification Cylinders (HM-220D)," published August 8, 2002 for additional information [67 FR 51633].
Q5.      You ask if—in the event one or more cylinders are tested and a REE number(s) is recorded in the test shop(s) logs—the DOT will accept a record of three such tests as being substantially correct for that specific cylinder model, and allow that number to be used for any other cylinder from the same production group.  You specify by asking, "If my cylinder is tested and a REE number is found, can that be recorded or registered with the DOT or other organization, for future use by owners of other 'same' cylinders?"
A5.      It is the opinion of this Office that a REE value determined at the time of manufacture for a DOT 3AA cylinder would only be valid for other DOT 3AA cylinders of the same cylinder model that were also manufactured from the same "lot."
DOT permits computing the REE value in accordance with CGA Pamphlet C-5.  Under CGA Pamphlet C-5 section 3.3.1, the "k factor" may be determined through procedures followed for "three (3) cylinders typical of the design."  This "k factor" can be used in calculations related to the REE value.  CGA Pamphlet C-5 also provides procedures for other calculations that require information from the manufacturer to determine the "k factor" or REE value.  DOT also permits reference to data tabulated in CGA Pamphlet C-5, which was determined by CGA through an analysis of manufacturer data.  Neither the computations or data tabulations in CGA Pamphlet C-5 include a registry for cylinder requalifiers. 
Q6.      You ask whether any provision allows the REE number that has been determined for a cylinder to be recorded for future use of that cylinder, if it has not been stamped on the cylinder itself.  You specify by asking, "Can the hydrostatic shop that obtained the number document it in their test log, and then supply a copy of the log page?"
A6.      In accordance with § 180.215(b)(2), "for each cylinder marked pursuant to § 173.302a(b)(5) of this subchapter, the test sheet must indicate the method by which any average or maximum wall stress was computed."  Test records are not prohibited from including additional information.  Additional information about the source of the REE value may be helpful to a requalifier determining compliance with § 173.302a(b)(2) through (4).
I hope this information is helpful.  Please contact us if we can be of further assistance.
T. Glenn Foster
Chief, Regulatory Review and Reinvention
Standards and Rulemaking Division
173.302a(b)(1) through (5), 173.302a(b)(2) through (4), 173.302a(b)(3), 178.35, 180.215, 180.215(b)(2),

Regulation Sections

Section Subject
173.302a Additional requirements for shipment of nonliquefied (permanent) compressed gases in specification cylinders
173.302b Additional requirements for shipment of non-liquefied (permanent) compressed gases in UN pressure receptacles
178.35 General requirements for specification cylinders
180.215 Reporting and record retention requirements