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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 #17-0120

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: Mihama Corporation

Location State: NY Country: US

View the Interpretation Document

Response text:

September 07, 2018

Andrea Kornbluth
Mihama Corporation
200 Pinehurst Avenue
New York, NY  10033

Reference No. 17-0120

Dear Ms. Kornbluth:

This letter is in response to your October 31, 2017, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to pressure relief device (PRD) requirements for U.S. Department of Transportation (DOT) 39 specification cylinders. Specifically, you indicate that you fill these cylinders with "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1."

In accordance with § 173.301(f)(4), a PRD is required on a DOT 39 specification cylinder regardless of the cylinder size or the filled pressure. When used for a liquefied Division 2.1 material, a DOT 39 specification cylinder must be equipped with a metal PRD; fusible PRDs for liquefied gases are not authorized. Furthermore, § 173.301(f)(1) specifies that the PRD must be selected in accordance with CGA S 1.1 and CGA Pamphlet S 7, as incorporated by reference in § 171.7.

We have paraphrased and answered your questions as follows:

Q1. You ask if a DOT 39 specification cylinder can be filled with more than 75 in3 of "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1."

A1. The answer is yes.  Generally, R 32 refrigerant gases are classified as liquefied Division 2.1 flammable gases. Sections 173.304 and 173.304a provide the filling requirements for liquefied compressed gases and additional requirement for shipments of liquefied compressed gases in specification cylinders and do not specify that a DOT 39 specification cylinder cannot be filled with more than 75 in3 of "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1."

As mentioned in your request, PHMSA published a revised safety advisory notice on April 24, 2017, titled "Hazardous Materials: Use of DOT Specification 39 Cylinders for Liquefied Flammable Compressed Gas" [82 FR 18967; Notice No. 2016-14], which clarified that DOT 39 specification cylinders exceeding 75 in3 should not contain liquefied compressed cyclopropane, ethane, or ethylene, or liquefied petroleum gases. Your understanding is correct that this safety advisory did not apply to "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1."

Please note that on July 26, 2016, PHMSA published a notice of proposed rulemaking (NPRM) titled, "Hazardous Materials: Miscellaneous Amendments Pertaining to DOT Specification Cylinders (RRR)" [81 FR 48977; HM-234], which proposed to revise the requirements for § 173.304a and restrict the internal volume of a DOT 39 cylinder to 1.23 liters (nominal 75 in3) for a liquefied flammable gas. This proposed amendment was based on a petition for rulemaking (P-1622; PHMSA 2013 0201).

Q2. You ask if a DOT 39 specification cylinder filled with "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1" can be fitted with a CG-1 PRD.

A2. The answer is yes. As outlined in Table 3 of CGA S 1.1, Methylene Fluoride (R 32) is authorized to have a CG-1 PRD.

Q3. You ask if a DOT 39 specification cylinder filled with "UN3252, Difluoremethane or Refrigerant gas R 32, 2.1" can be fitted with a CG-7 PRD.

A3. The answer is yes. As outlined in Table 3 of CGA S 1.1, Methylene Fluoride (R 32) is authorized to have a CG-7 PRD.

Q4. You ask if a previous letter of interpretation on this topic (Reference No. 11-0117) applies to the scenario in your request.

A4. The answer is no. Reference No. 11-0117, issued by this Office on June 13, 2011, addresses PRD selection for a DOT 39 specification cylinder filled with HFO-1234yf shipped as "UN3161, Liquefied gas, flammable, n.o.s. (2,3,3,3 Tetrafluroprop-1-ene), 2.1." Reference No. 11-0117 does not reflect your scenario because you have a different commodity. Further, as opposed to Methylene Fluoride (R 32), which is listed in Table 3 of the CGA S 1.1, HFO-1234yf or 2,3,3,3 Tetrafluroprop-1-ene is not listed in Table 3, meaning that further analysis must be conducted to select the appropriate PRD for the cylinder. Please note that HM-234 proposed to require the use of a CGA CG 7 PRD for liquefied flammable gases in DOT 39 specification cylinders when the gas is not listed in CGA S 1.1.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

 

Dirk Der Kinderen
Chief, Standards Development
Standards and Rulemaking Division

173.301(f)(4), 173.301(f)(1), 171.7, 173.304, 173.304a

Regulation Sections

Section Subject
171.7 Reference material
173.301 General requirements for shipment of compressed gases and other hazardous materials in cylinders, UN pressure receptacles and spherical pressure vessels
173.304a Additional requirements for shipment of liquefied compressed gases in specification cylinders