Ongoing initiative to get high energy capacity "green fuel" containers to market quickly and cost effectively. The United States has decided to invest in "green energy" technology, to become energy independent, and to "Innovate Our Way to a Clean Energy Future.

Beeson, Harold

Cone, Darren

Greene, Nathanael

McCloskey, David

NASA Technical Reports Server

Considerations for Using Composite Pressure 
Vessels (CPVs) in Fuel Storage for Automotive 
Applications
Nathanael Greene, NASA White Sands Test Facility
Darren Cone, NASA White Sands Test Facility
Harold Beeson, PhD., NASA White Sands Test Facility
David McCloskey, National Institute of Standards and Technology
https://ntrs.nasa.gov/search.jsp?R=20130011401 2019-08-31T00:37:08+00:00Z
History
 Ongoing initiative to get high energy capacity 
“green fuel” containers to market quickly and 
cost effectively
◦ The United States has decided to invest in “green 
energy” technology, to become energy 
independent, and to “Innovate Our Way to a Clean 
Energy Future” – (Blueprint for a Secure Energy 
Future, March 30, 2011, The White House)
 Commercializing NASA-developed high 
efficiency composite pressure vessel (CPV) fuel 
storage containers
◦ Developed in the 1970s for the Space Shuttle
 U.S. Department of Energy directing rapid 
commercialization of CPV fuel storage 
containers with programs like:
◦ The ARPA-E Move Program
◦ Vehicle Technologies Program
◦ Hydrogen and Fuel Cells Program
Composite Pressure Vessel “Green” 
Fuel Container Installation
Photo courtesy of NAFTC eNews
Photo courtesy of Pickens Plan
Standards and Regulations
 Initial 15-Year Service Life for Fuel 
Containers
◦ Consensus standard, “ANSI/AGA NGV2-1992, 
American National Standard for Basic 
Requirements for Compressed Natural Gas 
Vehicle (NGV) Fuel Containers.”
◦ Department of Transportation code 
“Compressed Natural Gas Fuel Containers in 
49CFR571.304 Standard No. 304; Compressed 
Natural Gas Fuel Container Integrity.”
 Growth in CPV fuel container use
◦ 9% of world vehicle population by 2020 
(65 million vehicles fueled with natural gas) 
CPV Type Definitions (TP-304 for FMVSS 304)  Type 2 container is a metallic liner over which an overwrap such as carbon fiber or 
fiberglass is applied in a hoop wrapped pattern over the liner's cylinder sidewall. Type 3 container is a metallic liner over which an overwrap 
such as carbon fiber or fiberglass is applied in a full wrapped pattern over the entire liner, including the domes. Type 4 container is non-
metallic liner over which an overwrap such as carbon fiber or fiberglass is applied in a full wrapped pattern over the entire liner, including the 
domes. 
Composite Pressure Vessel 
“Green” Fuel Passenger Bus
Photo courtesy of Show Times
Photo courtesy of CFS International
Issue
 Burst failures of CPV fuel containers during 
service life
◦ 3000-10,000 psi service pressure
 Kinetic energy pressure release (blast and 
fragmentation)
 Possible fire of gaseous contents
◦ Potential for injury and loss of life
 Focus: Type 4 CPV fuel container failures
◦ 1996 Metro Transit Authority Bus, California-
USA
◦ 1996 Industrial Accident, Canada
◦ 2008 Brisbane Bus, Brisbane-Australia
◦ 2009 Delivery Vehicle, California-USA
◦ 2012 Brisbane Bus, Brisbane-Australia
◦ “Four serious explosion accidents of Type 4 
tanks in China” – 12/10/2009 DOE CNG-H2 
Workshop
Delivery Vehicle, California 2009  (Type IV)
Passenger Bus, Australia 2009 (Type IV)
Solution
 NHTSA call to work with NASA and NIST to investigate 
failures (IAA DTNH22-10-X-00259)
◦ Minimize risk of failures in “green” fuel vehicle gas tanks
 Program Objectives
1. Perform unbiased investigations to determine root cause(s) of 
failures
 Review failures of CPV fuel containers in the U.S.
 Review failures in other countries that have implemented broad use of 
CNG vehicles and where cylinder type and root cause(s) are not 
explained or are unknown
2. Determine if current codes and standards ensure public safety 
for CPV fuel containers
3. Fill holes in codes and standards through conduct of 
development test and evaluation activities
Program Overview
 The initial focus is on testing and evaluation of Type 4 
cylinders that are:
◦ 1. Failed, 2. Unfailed and removed from service (Pasedna-CA case 
study), and 3. Certified new
 Program is a three-phased process - not fully funded
◦ Phase I - Establish internal and external condition of CPV fuel 
tanks after service, generic Type 4 fault tree analysis 
(FTA)/failure investigation (FI) methodology, and nondestructive 
testing per WSTF-TP-1178-001-11.
◦ Phase II - Vessel sectioning, destructive testing, fault tree 
validation, design of experiments, materials analysis, and 
mechanical properties per WSTF-TP-1178-002-12.
◦ Phase III - Burst testing, durability testing, analyzing results, and 
final reporting of data.
Program is reviewed by agency integration team 
(Includes NASA, DOT-NHTSA, DOT-PHMSA, DOE, 
FAA, and NIST) and is under an interagency technical 
core team
Missing Material
Damage 0°
90°
Liner deformation (bulge)
WSTF ID 11-45271 (Borescope)
Phase I Nondestructive Service Evaluation Results
 Liner (separation and indications)
 Mounting
◦ Unexpected mounting configurations
◦ Labels missing or obscured by mounts. Potential for cylinder misuse such as over pressurization or failure to 
remove upon expiration.
◦ A variation in geometry, that could lead to potential strength and/or mounting variability.
 Interfacing connections
◦ Unexpected variation in fitting break-away torque from below 5 ft-lb to 170 ft-lb. No provision for proper  
fitting torque application (leakage at the fitting) could result in flammability and hypoxia hazard inside and 
outside of vehicles. Over torque could result in damage to the CPV fuel container.
 Durability issues
◦ Labels did not “remain in place and be legible for the manufacturer's recommended service life” per the 
FMVSS 304 section S7.4 requirement
◦ Limited shipping protection (exposure to chemical and mechanical damage)
 Media compatibility/chemical damage
◦ Interior liquid pooling
 Mechanical damage
◦ No enforcement of 3-year/36,000 mile inspection for damage
 Design specification and construction difference
180°
90°
Liner 
Indications
WSTF ID 11-45272
Pooled Oil
8Create FTA of 
Undesired 
Outcome
Create 
Timeline
Identify the 
Undesired 
Outcome
Create 
ETA
Generate 
Recommendations
Typical NASA Root Cause Analysis (RCA) Method
Event Tree Analysis  (ETA) 
assesses the consequences of 
given initiating events 
(formal inductive technique)
Fault Tree Analysis (FTA) is a 
formal approach for 
resolving the basic causes of 
a given undesired event 
(formal deductive technique)
Components
“the Fiber & Matrix Fracture”
FM-001
The Component(s)
“the Lamina(s) Fracture”
LAM-001 The individual layers consist of 
high-modulus, high-strength 
carbon & glass fibers in a 
polymeric, matrix material. 
The Subsystem
“the Laminate Fracture”
LAE-001
Deflagration Crack Leaks
Fracture Crack Fracture
Rupture 
and/or 
Explosion
Rupture 
and/or 
Explosion
Deflagration
Rupture 
and/or 
Explosion
When! What?
Fault Tree Analysis (FTA) 
Top Event
“The SYSTEM Failure 
Mode”
gate identifier
AND gate
1st Decision
An “AND gate” to
identify the conditions
and events that need
to occur
Pressure > 0
A-1
NASA WSTF Generic
Fault Tree Analysis
EXAMPLE STEP #1
NOTE
These are the 
System and Subsystem Engineer Failures 
but they are the Component Engineer’s
Failure Effects
Explosion = rapid release of high pressure gas into the environment
Deflagration = flame spread rate less than the speed of sound
Detonation = flame spread rate above the speed of sound
For the FTA, 
“System Failure” 
is the composite
Potential 
Failure Modes
For a Top Event
Consider the Cylinder 
to be “the system”
in the FTA
Unplanned 
Event
Fluid = CNG
Automotive 
Industry
Phase II Destructive Evaluation Results
NASA White Sands Test Facility 
Personnel  Cross-sectioning
a CPV Fuel Container
 Validated sectioning on new 
pathfinder vessel
 Cross-sectioning CPV fuel 
containers removed from 
service (in process)
 Physical and chemical 
properties on new CPV fuel 
containers and CPV fuel 
containers removed from 
service (in process)
 Validate generic fault tree 
analysis (FTA)/FI methodology 
against Type 4 case studies
Phase II Validation of Generic FTA/FI Methodology Results
 Inputs to fault tree analysis/generic FI methodology 
from review of all Type 4 failures
◦ Known failures are during the 15-year service life
◦ Burst failure mode observed (the technical community expects 
leakage)
◦ Head-to-dome transition failure observed (the technical 
community expects predictable side wall leakage)
 Inputs from documented case study
◦ Two vessels burst
◦ Vertical vessel support ring damage
◦ Fracture pattern in the fiber and liner
 FTA indicates failure initiated in CPV tank head-to-dome 
transition
Phase III Burst and Durability Testing
 Residual life determination
◦ Cycling Testing
 DOE provided new CPV fuel containers and 15,000 cycle testing 
that complimentary meets some of NHTSA’s test matrix
◦ Pneumatic Burst Testing
 Failure mode testing on at least one CPV fuel container 
removed from service
 Closure of fault trees for case study failures
◦ Narrow the CPV fuel container FTA from generic to specific using 
the Pasadena California case study
 Determination of probable failure mechanism(s)
 Data for updating codes and standards
 Report
Summary
 Type 4 cylinder service evaluation is complete
 Cross-sectioning completed on a new Type 4 CPV fuel 
container
 Cross-sectioning of vessels removed from service in process
 Validation of the generic Type 4 FTA/FI methodology in 
process
 Developing the Phase III Burst and Durability Test Plan
 Initiate burst and durability testing in FY13
 Update codes and standards with new knowledge
 Generic FTA/FI investigation validation for Type 2 and Type 3 
cylinders not currently funded
 Repeating for Type 2 and Type 3 cylinders not funded
Thank you
NASA White Sands Test Facility
12600 NASA Road
Mailstop RF
575.524.5723
http://www.nasa.gov/centers/wstf/laboratories/composite/index.html
References
 http://www.showtimesdaily.com/news-articles/cng-and-
beyond-in-los-angeles
 http://www.cfsinternational.com.au/ngv_technical.php
 http://naftcenews.wvu.edu/naftc_enews/2010/12/18/-let-s-
clear-the-air-
 http://push.pickensplan.com/photo/photo/show?id=218703
4%3APhoto%3A225586&context=album&albumId=2187034
%3AAlbum%3A447634
 The International Association of Natural Gas Vehicles 
(IANGV, Auckland, New Zealand) 


Considerations for Using Composite Pressure Vessels (CPVs) in Fuel Storage for Automotive Applications

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