Notice2025-04605
Hazardous Materials: Request for Feedback on Determining the Effectiveness of Pressure Relief Devices (PRDs) on Composite Overwrapped Pressure Vessels (COPVs)
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Published
March 19, 2025
Issuing agencies
Transportation DepartmentPipeline and Hazardous Materials Safety Administration
Abstract
PHMSA is publishing this notice to solicit information to evaluate the test design for proposed bonfire tests on fully charged composite overwrapped pressure vessels (COPVs) with different pressure relief devices; seek input on how test results could inform design guidelines for COPVs; and solicit feedback on the impacts of possible updates for design guidelines.
Full Text
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<title>Federal Register, Volume 90 Issue 52 (Wednesday, March 19, 2025)</title>
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[Federal Register Volume 90, Number 52 (Wednesday, March 19, 2025)]
[Notices]
[Pages 12934-12936]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-04605]
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DEPARTMENT OF TRANSPORTATION
Pipeline and Hazardous Materials Safety Administration
[Docket No. PHMSA-2024-0180, (Notice No. 2024-15)]
Hazardous Materials: Request for Feedback on Determining the
Effectiveness of Pressure Relief Devices (PRDs) on Composite
Overwrapped Pressure Vessels (COPVs)
AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA),
Department of Transportation (DOT).
ACTION: Notice; request for information.
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SUMMARY: PHMSA is publishing this notice to solicit information to
evaluate the test design for proposed bonfire tests on fully charged
composite overwrapped pressure vessels (COPVs) with different pressure
relief devices; seek input on how test results could inform design
guidelines for COPVs; and solicit feedback on the impacts of possible
updates for design guidelines.
DATES: Interested parties are invited to submit comments on or before
June 17, 2025. Comments received after that date will be considered to
the extent possible.
ADDRESSES: You may submit comments identified by the Docket Number
PHMSA-2024-0180 by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
Follow the instructions for submitting comments.
<bullet> Fax: 1-202-493-2251.
<bullet> 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.
<bullet> 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-2024-0180] 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 <a href="http://www.regulations.gov">http://www.regulations.gov</a> or DOT's 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 <a href="http://www.regulations.gov">http://www.regulations.gov</a>, as described in the system of records notice (DOT/
ALL-14 FDMS), which can be reviewed at <a href="http://www.dot.gov/privacy">http://www.dot.gov/privacy</a>.
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
[[Page 12935]]
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 Andrew Leyder,
Pipeline and Hazardous Materials Safety Administration, U.S. Department
of Transportation, 1200 New Jersey Avenue SE, Washington, DC 20590-
0001. Any commentary that PHMSA receives that is not specifically
designated as CBI will be placed in the public docket for this notice.
FOR FURTHER INFORMATION CONTACT: Andrew Leyder, Office of Hazardous
Materials Safety, Research, Development & Technology, by phone at 202-
360-0664, by email at <a href="/cdn-cgi/l/email-protection#c3a2ada7b1a6b4edafa6baa7a6b183a7acb7eda4acb5"><span class="__cf_email__" data-cfemail="c0a1aea4b2a5b7eeaca5b9a4a5b280a4afb4eea7afb6">[email protected]</span></a>, or by mail at Pipeline and
Hazardous Materials Safety Administration, U.S. Department of
Transportation, 1200 New Jersey Avenue SE, Washington, DC 20590-0001.
SUPPLEMENTARY INFORMATION:
I. Purpose
PHMSA is publishing this notice to (1) solicit information to
evaluate the test design for proposed bonfire tests on fully charged
composite overwrapped pressure vessels (COPVs) with different Pressure
Relief Devices; (2) seek input on how test results could inform design
guidelines for COPVs; and (3) solicit feedback on the impacts of
possible updates for design guidelines.
II. Background
Pressure relief devices (PRDs) are standard equipment on all
compressed natural gas containers. The function of a PRD is to vent the
compressed gases in the case of a fire, preventing rupture and the
subsequent high-pressure gas release with a possible ignition and
explosion. If the gas is released at high-pressure in certain
environments, the result could be catastrophic. Therefore, PRD design
and manufacture must offer a degree of protection and reliability that
meets or exceeds that of the cylinder to provide the proper degree of
safety. Pressure vessels can be constructed using metal (e.g., steel or
aluminum) or composite material (i.e., cylinder/tube is wrapped with
continuous filaments held with metallic/polymer liners). Pressure
vessels used for transporting flammable gases are equipped with PRDs to
prevent explosions or ruptures during a fire. Per the Compressed Gas
Association (CGA) pamphlet S1.1, both metallic pressure vessels and
COPVs are typically equipped with CG-4 or CG-5 devices. These PRDs are
designed to activate under a combination of excess temperature and
pressure during a fire. The CG-4 device is more sensitive to
temperature as it uses a fusible metal plug that melts at a lower
temperature than those used in a CG-5 device.
Though there have been issues of premature activation, PRDs
historically have been used without major problems. Stainless steel
DOT-approved cylinders are proven to be fire-resistant for 20 minutes
without significant loss of yield strength. Due to heat conduction
through these steel cylinders, the PRDs may be activated before
cylinder rupture when exposed to excessive heat.
In contrast, COPVs are more heat-insulating; the internal pressure
of the cylinder typically will not reach PRD activating pressures
before the resin in the COPV shell begins to fail. Consequently, COPVs
will often rupture at lower internal pressures than their metallic
counterparts because of hull breakdown, and the CG-4 and CG-5 PRDs
never reach burst pressures.
On February 11, 2018, a fire incident occurred involving a COPV
hydrogen tube trailer equipped with Type CG-5 PRDs. A subsequent
National Transportation Safety Board (NTSB) investigation (NTSB
incident report number NTSB/HZM-19/02 PB2019-101398) indicated that the
Type CG-5 PRDs installed on these COPVs had a lower setting than is
required under CGA PRD standard CGA S1.1. The lower set pressure of the
Type CG-5 PRDs resulted in premature activation of the devices and
caused a fire. The fire then spread to adjacent COPVs, which had CG-5
PRDs that did not function correctly, resulting in an explosion of
several additional COPVs. NTSB determined that while a correctly rated
CG-5 PRD may have reduced the risk of fire initiation, the CG-5 PRD
would not have prevented the COPVs from exploding due to exposure to
high heat temperatures.
The NTSB report for this incident is available online at 59258
(<a href="http://ntsb.gov">ntsb.gov</a>). NTSB directed PHMSA to work with CGA to develop design
guidelines for tube trailer pressure relief device vent systems in
Recommendation H-19-21. To address that recommendation, a systematic
evaluation of alternative PRDs in COPVs is necessary. There are
alternative PRDs (e.g., CG-9 and CG-10) that use thermal activation
rather than the pressure/temperature combination for activation. These
PRDs are commonly used on NGV-2 composite tubes, which have different
design specifications and operating conditions than COPVs regulated
under the Hazardous Materials Regulations (49 CFR parts 171 through
180). To evaluate whether thermally activated PRDs are effective
alternatives for COPVs, PHMSA is proposing a test design for various
PRDs subjected to bonfire tests on COPVs.
III. Request for Feedback
The objective of this project is to assess the effectiveness of
various PRDs when subjected to bonfire tests on fully charged COPVs.
The test results will determine the optimal number, type, and location
of PRDs to install in fully charged COPVs. The goal is to prevent
potential cylinder ruptures similar to the one described in the NTSB
investigation and recommendations reports. These test results can
inform future pressure vessel design guidelines.
The specified COPVs are:
a. Type 3 COPVs with 16'' outside diameter, 120'' length, and
5,400-psig test pressure.
b. Type 4 COPVs with 16'' outside diameter, 120'' length, and
5,400-psig test pressure.
PRDs to be tested are CG-4, CG-5, CG-9, and CG-10 PRDs that meet
the requirements set forth in pamphlet S1.1 of the CGA.
Bonfire testing will be completed under four different pressure
vessel configurations at three different locations for each PRD. Each
bonfire will be applied for a minimum of 30 minutes.
<bullet> One type 3 COPV with a CG-4 PRD at each end will be used,
with the center of the fire at three different locations (PRD exposed
to fire 6'' and 10'' away from the fire).
<bullet> One type 4 COPV with a CG-5 PRD at each end will be used,
with the center of the fire at three different locations (PRD exposed
to fire 6'' and 10'' away from the fire).
<bullet> A steel pipe with a CG-9 PRD will be used, with the center
of the fire at three different locations (PRD exposed to fire 6'' and
10'' away from the fire).
<bullet> A steel pipe with a CG-10 PRD will be used, with the
center of the fire at three different locations (PRD exposed to fire
6'' and 10'' away from the fire).
<bullet> One type 4 COPV with a CG-9 PRD at each end will be used,
with the center of the fire at three different locations (PRD exposed
to fire 6'' and 10'' away from the fire).
<bullet> One type 4 COPV with a CG-10 PRD at each end will be used,
with the center of the fire at three different locations (PRD exposed
to fire 6'' and 10'' away from the fire).
[[Page 12936]]
PHMSA requests comment on the following questions to assist in our
evaluation of the proposed research and development with a scope as
specified above.
1. Would the results from the proposed testing adequately inform
design specifications for vent systems?
2. Is the number of COPV tubes in the above test matrix adequate
for a representative test of the COPV, or should additional COPV tubes
be tested to ensure replicability?
3. Is a bonfire test of at least 30 minutes sufficient to test
activation of the PRDs? If not, what would be a sufficient minimum
duration to test PRD activation?
4. Should a minimum bonfire temperature be specified to test PRD
activation? If so, what should the minimum bonfire temperature be?
5. Is the number of bonfire tests (one for each configuration)
sufficient to test PRD effectiveness? If not, how many replicates of
the test should be conducted?
6. Would testing at 6'' and 10'' away from the center of the fire
be sufficient to capture differences in fire location from the PRDs? If
not, what fire distances/locations are recommended?
7. Should different operating pressures be tested? If so, what
other pressures should be tested?
8. Do the proposed COPV/PRD combinations provide an accurate
comparison of temperature/pressure-activated PRDs to temperature-
activated PRDs? If not, which COPV/PRD combinations should also be
considered in addition to the above testing matrix?
9. What other variables, if any, should be included in testing?
10. Are there other existing safety concerns about COPVs and PRDs
that PHMSA should be aware of?
11. What, if any, are the cost impacts of using CG-9 or CG-10 PRDs
on COPVs instead of CG-4 or CG-5?
12. How common is the current use of CG-9 or CG-10 PRDs for COPVs
used to transport flammable gases?
13. Should the allowable PRDs for COPVs used to transport flammable
gases be limited to CG-9 or CG-10?
Issued in Washington, DC, on March 14, 2025.
Yolanda Y. Braxton,
Director, Operations System Division, Office of Hazardous Materials
Safety, Pipeline and Hazardous Materials Safety Administration.
[FR Doc. 2025-04605 Filed 3-18-25; 8:45 am]
BILLING CODE 4910-60-P
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