ASTM E2982-21

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2982 − 21
Standard Guide for
Nondestructive Examination of Thin-Walled Metallic Liners
in Filament-Wound Pressure Vessels Used in Aerospace
Applications
This standard is issued under the fixed designation E2982; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope alloys, nickel-based alloys, and stainless steels. In the case of
COPVs, the composites through which the NDT interrogation
1.1 This guide discusses current and potential nondestruc-
shouldbemadeafteroverwrappinginclude,butarenotlimited
tive testing (NDT) procedures for finding indications of dis-
to, various polymer matrix resins (for example, epoxies,
continuities in thin-walled metallic liners in filament-wound
cyanate esters, polyurethanes, phenolic resins, polyimides
pressure vessels, also known as composite overwrapped pres-
(including bismaleimides), polyamides) with continuous fiber
sure vessels (COPVs). In general, these vessels have metallic
reinforcement (for example, carbon, aramid, glass, or poly-
liner thicknesses less than 2.3 mm (0.090 in.), and fiber
(phenylenebenzobisoxazole) (PBO)).
loadings in the composite overwrap greater than 60 percent by
weight. In COPVs, the composite overwrap thickness will be
1.6 ThisguidedescribestheapplicationofestablishedNDT
of the order of 2.0 mm (0.080 in.) for smaller vessels, and up
procedures; namely,Acoustic Emission (AE, Section 7), Eddy
to 20 mm (0.80 in.) for larger ones.
Current Testing (ET, Section 8), Laser Profilometry (LP,
Section 9), Leak Testing (LT, Section 10), Penetrant Testing
1.2 This guide focuses on COPVs with nonload sharing
(PT, Section 11), and Radiographic Testing (RT, Section 12).
metallic liners used at ambient temperature, which most
These procedures can be used by cognizant engineering
closely represents a Compressed GasAssociation (CGA) Type
organizations for detecting and evaluating flaws, defects, and
III metal-lined COPV. However, it also has relevance to (1)
accumulateddamageinmetallicPVs,thebaremetalliclinerof
monolithic metallic pressure vessels (PVs) (CGAType I), and
COPVsbeforeoverwrapping,andthemetalliclinerofnewand
(2) metal-lined hoop-wrapped COPVs (CGAType II).
in-service COPVs.
1.3 The vessels covered by this guide are used in aerospace
applications; therefore, examination requirements for disconti- 1.7 Allmethodsdiscussedinthisguide(AE,ET,LP,LT,PT,
nuities and inspection points will in general be different and and RT) are performed on the metallic liner of COPVs before
more stringent than for vessels used in non-aerospace applica- or after overwrapping and structural cure. The same methods
tions. may also be performed on metal PVs. For NDTprocedures for
detectingdiscontinuitiesinthecompositeoverwrapinfilament
1.4 This guide applies to (1) low pressure COPVs and PVs
wound pressure vessels; namely, AE, ET, Shearography Test-
used for storing aerospace media at maximum allowable
ing(ST),RT,UltrasonicTesting(UT)andVisualTesting(VT);
working pressures (MAWPs) up to 3.5 MPa (500 psia) and
3 consult Guide E2981.
volumes up to 2000 L (70 ft ), and (2) high pressure COPVs
used for storing compressed gases at MAWPs up to 70 MPa
1.8 Due to difficulties associated with inspecting thin-
(10 000 psia) and volumes down to 8 L (500 in. ). Internal
walled metallic COPV liners through composite overwraps,
vacuum storage or exposure is not considered appropriate for
andtheavailabilityoftheNDEmethodslistedin1.6toinspect
any vessel size.
COPV liners before overwrapping and metal PVs, ultrasonic
NOTE 1—Some vessels are evacuated during filling operations, requir-
testing (UT) is not addressed in this standard. UT may still be
ing the tank to withstand external (atmospheric) pressure.
performed as agreed upon between the supplier and customer.
1.5 The metallic liners under consideration include, but are
Ultrasonic requirements may utilize Practice E2375 as appli-
not limited to, ones made from aluminum alloys, titanium
cable based upon the specific liner application and metal
thickness. Alternate ultrasonic inspection methods such as
Lambwave,surfacewave,shearwave,reflectorplate,etc.may
This guide is under the jurisdiction ofASTM Committee E07 on Nondestruc-
tiveTesting and is the direct responsibility of Subcommittee E07.10 on Specialized
be established and documented per agreed upon contractual
NDT Methods.
requirements. The test requirements should be developed in
Current edition approved March 15, 2021. Published April 2021. Originally
ε1
conjunction with the specific criteria defined by engineering
approved in 2014. Last previous edition approved in 2014 as E2982–14 . DOI:
10.1520/E2982-21. analysis.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2982 − 21
1.9 In general, AE and PT are performed on the PV or the ization established in the Decision on Principles for the
baremetalliclinerofaCOPVbeforeoverwrapping(inthecase Development of International Standards, Guides and Recom-
of COPVs, AE is done before overwrapping to minimize mendations issued by the World Trade Organization Technical
interferencefromthecompositeoverwrap).ET,LT,andRTare Barriers to Trade (TBT) Committee.
performed on the PV, bare metallic liner of a COPV before
2. Referenced Documents
overwrapping, or on the as-manufactured COPV. LP is per-
2.1 ASTM Standards:
formed on the inner and outer surfaces of the PV, or on the
C274Terminology of Structural Sandwich Constructions
inner surface of the COPV liner both before and after over-
(Withdrawn 2016)
wrapping. Furthermore, AE and RT are well suited for evalu-
D1067Test Methods for Acidity or Alkalinity of Water
ating the weld integrity of welded PVs and COPV liners.
D3878Terminology for Composite Materials
1.10 Wherever possible, the NDT procedures described
D5687/D5687MGuide for Preparation of Flat Composite
should be sensitive enough to detect critical flaw sizes of the
Panels with Processing Guidelines for Specimen Prepara-
order of 1.3 mm (0.050 in.) length with a 2:1 aspect ratio.
tion
NOTE 2—Liners often fail due to improper welding resulting in
E165/E165MPractice for Liquid Penetrant Testing for Gen-
initiation and growth of multiple small discontinuities of the order of
0.050 mm (0.002 in.) length. These will form a macro-flaw of 1-mm eral Industry
(0.040-in.) length only at higher stress levels.
E215PracticeforStandardizingEquipmentandElectromag-
netic Examination of Seamless Aluminum-Alloy Tube
1.11 For NDT procedures that detect discontinuities in the
composite overwrap of filament-wound pressure vessels E426PracticeforElectromagnetic(EddyCurrent)Examina-
tion of Seamless and Welded Tubular Products, Titanium,
(namely, AE, ET, shearography, thermography, UT and visual
examination), consult Guide E2981. Austenitic Stainless Steel and Similar Alloys
E432Guide for Selection of a Leak Testing Method
1.12 In the case of COPVs which are impact damage
E493/E493MPractice for Leaks Using the Mass Spectrom-
sensitiveandrequireimplementationofadamagecontrolplan,
eter Leak Detector in the Inside-Out Testing Mode
emphasis is placed on NDT procedures that are sensitive to
E499/E499MPractice for Leaks Using the Mass Spectrom-
detecting damage in the metallic liner caused by impacts at
eter Leak Detector in the Detector Probe Mode
energy levels which may or may not leave any visible
E543Specification forAgencies Performing Nondestructive
indication on the COPV composite surface.
Testing
1.13 Thisguidedoesnotspecifyaccept/rejectcriteria(4.10)
E976GuideforDeterminingtheReproducibilityofAcoustic
used in procurement or used as a means for approving PVs or
Emission Sensor Response
COPVs for service. Any acceptance criteria provided herein
E1000Guide for Radioscopy
are given mainly for purposes of refinement and further
E1032PracticeforRadiographicExaminationofWeldments
elaborationoftheproceduresdescribedintheguide.Projector
Using Industrial X-Ray Film
original equipment manufacturer (OEM) specific accept/reject
E1066/E1066MPractice for Ammonia Colorimetric Leak
criteria should be used when available and take precedence
Testing
over any acceptance criteria contained in this document.
E1209Practice for Fluorescent Liquid Penetrant Testing
Using the Water-Washable Process
1.14 This guide references established ASTM test methods
thathaveafoundationofexperienceandthatyieldanumerical E1210Practice for Fluorescent Liquid Penetrant Testing
Using the Hydrophilic Post-Emulsification Process
result, and newer procedures that have yet to be validated
which are better categorized as qualitative guidelines and E1219Practice for Fluorescent Liquid Penetrant Testing
Using the Solvent-Removable Process
practices.The latter are included to promote research and later
elaboration in this guide as methods of the former type. E1255Practice for Radioscopy
E1309 Guide for Identification of Fiber-Reinforced
1.15 To ensure proper use of the referenced standard
Polymer-Matrix Composite Materials in Databases(With-
documents, there are recognized NDT specialists that are
drawn 2015)
certified according to industry and company NDT specifica-
E1316Terminology for Nondestructive Examinations
tions.ItisrecommendedthatanNDTspecialistbeapartofany
E1416Practice for Radioscopic Examination of Weldments
thin-walled metallic component design, quality assurance,
E1417Practice for Liquid Penetrant Testing
in-service maintenance, or damage examination.
E1419/E1419MPractice for Examination of Seamless, Gas-
1.16 Units—The values stated in metric units are to be
Filled, Pressure Vessels Using Acoustic Emission
regarded as the standard. The English units given in parenthe-
E1434Guide for Recording Mechanical Test Data of Fiber-
ses are provided for information only.
ReinforcedCompositeMaterialsinDatabases(Withdrawn
1.17 This standard does not purport to address all of the
2015)
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
priate safety, health, and environmental practices and deter-
Standards volume information, refer to the standard’s Document Summary page on
mine the applicability of regulatory limitations prior to use.
the ASTM website.
1.18 This international standard was developed in accor-
The last approved version of this historical standard is referenced on
dance with internationally recognized principles on standard- www.astm.org.
E2982 − 21
E1471Guide for Identification of Fibers, Fillers, and Core 2.5 ASME Document:
Materials in Computerized Material Property Databases ASME Boiler and Pressure Vessel Code, Section VNonde-
structive Examinations, Article 12, Rules for the Con-
(Withdrawn 2015)
struction & Continued Service of Transport Tanks
E1742/E1742MPractice for Radiographic Examination
2.6 ASNT Documents:
E1815Test Method for Classification of Film Systems for
ASNT CP-189Standard for Qualification and Certification
Industrial Radiography
of Nondestructive Testing Personnel
E2007Guide for Computed Radiography
SNT-TC-1ARecommended Practice for Personnel Qualifi-
E2104Practice for Radiographic Examination of Advanced
cation and Certification in Nondestructive Testing
Aero and Turbine Materials and Components
Leak Testing, Volume 1,Nondestructive Testing Handbook
E2033Practice for Radiographic Examination Using Com-
2.7 CEN Documents:
puted Radiography (Photostimulable Luminescence
EN 60825-1Safety of Laser Products—Part 1: Equipment
Method)
Classification, Requirements and User’s Guide
E2261/E2261MPractice for Examination of Welds Using
EN 16407-1Non-destructive testing—Radiographic inspec-
the Alternating Current Field Measurement Technique
tion of corrosion and deposits in pipes by X- and gamma
E2338Practice for Characterization of Coatings Using Con-
rays—Part 1: Tangential radiographic inspection
formable Eddy Current Sensors without Coating Refer-
2.8 Federal Standards:
ence Standards
21 CFR 1040.10Laser products
E2375Practice for Ultrasonic Testing of Wrought Products
21 CFR 1040.11Specific purpose laser products
E2445/E2445MPractice for Performance Evaluation and
2.9 ISO Document:
Long-Term Stability of Computed Radiography Systems
ISO 9712Non-destructive testing—Qualification and certi-
E2446Practice for Manufacturing Characterization of Com-
fication of NDT personnel
puted Radiography Systems
2.10 Compressed Gas Association Standard:
E2597/E2597MPracticeforManufacturingCharacterization
CGAPamphletC-6.4MethodsforVisualInspectionofAGA
of Digital Detector Arrays
NGV2 Containers
E2698Practice for Radiographic Examination Using Digital
2.11 LIA Document:
Detector Arrays
ANSI, Z136.1-2000Safe Use of Lasers
E2736Guide for Digital Detector Array Radiography
2.12 MIL Documents:
E2737Practice for Digital Detector Array Performance
MIL-HDBK-6870Inspection Program Requirements, Non-
Evaluation and Long-Term Stability
destructive for Aircraft and Missile Materials and Parts
E2884Guide for Eddy Current Testing of Electrically Con-
MIL-HDBK-340Test Requirements for Launch, Upper-
ducting Materials Using Conformable Sensor Arrays
Stage, and Space Vehicles, Vol. I: Baselines
E2981Guide for Nondestructive Examination of Composite
MIL-HDBK-1823Non-destructive Evaluation System Reli-
Overwraps in Filament Wound Pressure Vessels Used in
ability Assessment
Aerospace Applications
2.13 NASA Documents:
2.2 AIA Standard:
JSC 25863BFracture Control Plan for JSC Space-Flight
NAS 410NAS Certification & Qualification of Nondestruc-
Hardware
tive Test Personnel
NASA-STD-5003Fracture Control Requirements for Pay-
loads Using the Space Shuttle
2.3 ANSI/AIAA Standards:
NASA-STD-5009Nondestructive Evaluation Requirements
ANSI/AIAA S-080 Space Systems—Metallic Pressure
for Fracture Control Programs
Vessels,PressurizedStructures,andPressureComponents
ANSI/AIAA S-081 Space Systems—Composite Over-
wrapped Pressure Vessels (COPVs) 8
Available from ASME, Three Park Avenue, New York, NY 10016-5990,
800-843-2763 (U.S/Canada), email: CustomerCare@asme.org.
2.4 AMS Document:
AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Qualified Products List (Military) of Products Qualified
Available from British Standards Institution (BSI), 389 Chiswick High Rd.,
Under Detail Specification SAE-AMS 2644Inspection
London W4 4AL, U.K., http://www.bsigroup.com.
Material, Penetrant
Published by the Center for Devices and Radiological Health (CDRH) of the
Food and DrugAdministration (FDA) , available from Government Printing Office
Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE,
Washington, DC 20401.
4 12
Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000 Available from ISO copyright office, Case postale 56, CH-1211 Geneva 20,
WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org. Switzerland.
5 13
Available from American Institute of Aeronautics and Astronautics, 1801 Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th
Alexander Bell Drive, Suite 500, Reston, VA, 20191-4344. Floor, Chantilly, VA 20151-2923, http://www.cganet.com.
6 14
AvailablefromSAEInternational(SAE),400CommonwealthDr.,Warrendale, Available from the Laser Institute of America, 13501 Ingenuity Drive, Suite
PA 15096, http://www.sae.org. 128, Orlando, FL 32826.
7 15
TheactivityresponsibleforthisqualifiedproductslististheAirForceMateriel Available for Standardization Documents Order Desk, Bldg 4 Section D, 700
Command,ASC/ENOI, 2530 Loop Road West, Wright-PattersonAFB, OH 45433- Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
7101.ThequalifyingactivityresponsibleforqualificationapprovalisAFRL/RXSA, Available from the NASATechnical Standards System at the NASA website
2179 Twelfth St, Ste 1, Wright-Patterson AFB OH 45433-7809. www.standards.nasa.gov.
E2982 − 21
NASA-STD-5014Nondestructive Evaluation (NDE) Imple- 3.3.5 fracture control, n—the rigorous application of those
mentation Handbook for Fracture Control Programs branches of design engineering, quality assurance,
NASA-STD-(I)-5019Fracture Control Requirements for manufacturing, and operations dealing with the analysis and
Spaceflight Hardware preventionofcrackpropagationleadingtocatastrophicfailure.
NASA-TM-2012-21737ElementsofNondestructiveExami-
3.3.6 operating pressure, n—see Practice D1067, Section 3,
nation for the Visual Inspection of Composite Structures
Terminology.
MSFC-RQMT-3479 Fracture Control Requirements for
3.4 Definitions of Terms Specific to This Standard:
Composite and Bonded Vehicle and Payload Structures
3.4.1 burst-before-leak (BBL), n—an insidious failure
SSP30558FractureControlRequirementsforSpaceStation
mechanism exhibited by composite materials usually associ-
SSP 52005Payload Flight Equipment Requirements and
ated with broken fibers caused by mechanical damage, or with
Guidelines for Safety-Critical Structures
stress rupture at an applied constant load (pressure), whereby
NSTS 1700.7BISS Addendum, Safety Policy and Require-
the minimum time during which the composite maintains
ments for Payloads Using the International Space Station,
structural integrity considering the combined effects of stress
Change No. 3, February 1, 2002
level(s), time at stress level(s), and associated environment is
2.14 Non-Governmental Documents:
exceeded, resulting in a sudden, catastrophic event.
NTIAC-DB-97-02Nondestructive Evaluation (NDE) Capa-
bilities Data Book
3.4.2 capability demonstration specimens, n—asetofspeci-
NTIAC-TA-00-01Probability of Detection (POD) for Non-
mens made from material similar to the material of the
destructive Evaluation (NDE)
hardware to be examined with known flaws used to estimate
thecapabilityofflawdetection,thatis,probabilityofdetection
2.15 Governmental Document:
(POD) or other methods of capability assessment, of an NDT
AFRL-ML-WP-TR-2001-4011 Probability of Detection
procedure.
(POD) Analysis for the Advanced Retirement for Cause
(RFC)/EngineStructuralIntegrityProgram(ENSIP)Non-
3.4.3 composite overwrapped pressure vessel (COPV),
destructive Evaluation (NDE) System Development Vol-
n—an inner shell overwrapped with multiple plies of polymer
ume 2—User’s Manual (DTIC Accession Number
matrix impregnated reinforcing fiber wound at different wrap
ADA393072)
angles that form a composite shell.
2.16 ECSS Document:
3.4.3.1 Discussion—The inner shell or liner may consist of
ECSS-E-30-01ASpace Engineering Fracture control
an impervious metallic or nonmetallic material. The vessel
may be cylindrical or spherical and be manufactured with a
3. Terminology
minimum of one interface port for pressure fitting or valve
3.1 Abbreviations—The following abbreviations are ad- attachment (synonymous with filament-wound pressure
opted in this guide: acoustic emission (AE), eddy current vessel), or both.
testing (ET), laser profilometry (LP), leak testing (LT), pen-
3.4.4 cracks or crack-like flaws, n—flaws (for example,
etrant testing (PT), and radiographic testing (RT).
planar discontinuities) that are assumed to behave like cracks
3.2 Applicable Document—Documents cited in the body of and may be initiated and grow during material production,
this guide that contain provisions or other pertinent require-
fabrication, and service life of the part.
ments directly related and necessary to the performance of the
3.4.5 critical-initial flaw size (CIFS), n—the largest crack
activities specified by this guide.
that can exist at the beginning of the service life of a structure
3.3 Definitions—Terminology in accordance with Termi-
that has an analytical life equal to the service life times the
nologies D3878, E1316, and C274 should be used where
service life factor.
applicable.DefinitionoftermsrelatedtoNDT,andcomposites
3.4.5.1 Discussion—For example, a factor of 4 is used by
appearing in Terminologies C274, E1316, and D3878,
NASA.
respectively, should apply to the terms used in this guide.
3.4.6 damage control plan (DCP), n—a control document
3.3.1 cognizant engineering organization, n—see Terminol-
that captures the credible damage threats to a COPV during
ogy E1316.
manufacturing, transportation and handling, and integration
3.3.2 defect, n—see Terminology E1316.
into a space system up to the time of launch/re-launch, reentry
3.3.3 discontinuity, n—see Terminology E1316.
and landing, as applicable, and the steps taken to mitigate the
possibility of damage due to these threats, as well as delinea-
3.3.4 flaw, n—see Terminology E1316.
tion of NDT performed (for example, visual examination)
throughout the life cycle of the COPV.
Available from Advanced Materials, Manufacturing, and Testing Information
3.4.6.1 Discussion—The DPC should be provided by the
Analysis Center, 201 Mill Street, Rome, NY 13440, Phone 315-339-7117, Fax
designagencyandmadeavailableforreviewbytheapplicable
315-339-7107.
18 safety/range organization per ANSI/AIAA S-081.
CopiesareavailablefromDefenseTechnicalInformationCenter(DTIC),8725
John J. Kingman Road, Fort Belvoir VA22060-6218 or online http://www.dtic.mil/
3.4.7 damage-tolerance life, n—the required period of time
dtic/.
or number of cycles that the metallic liner of a COPV,
Available from ESA Publications Division, ESTEC, P.O. Box 299, 2200 AG
Noordwijk,The Netherlands. containing the largest undetected crack shown by analysis or
E2982 − 21
testing, will survive without leaking or failing catastrophically 3.4.20 special NDT, n—nondestructive examinations of
in the expected service load and environment; also referred to fracture critical hardware that are capable of detecting cracks
as safe-life. or crack-like flaws smaller than those assumed detectable by
standard NDT or do not conform to the requirements for
3.4.8 defect criteria, n—a documented statement defining
standard NDT.
theengineeringcriteriaforrejectingaCOPVbaseduponNDT.
3.4.21 standard NDT, n—well established nondestructive
3.4.9 fracture critical flaw, n—a flaw that exhibits unstable
examination methods for which a statistically based flaw
growth at service conditions.
detection capability has been established for a specific appli-
3.4.10 hit, n—(in reference to POD, not AE) an existing
cation or groups of similar applications, for example, such as
discontinuity that is identified as a find during a POD demon-
the methods discussed in NASA-STD-5009.
stration examination.
3.5 Symbols:
3.4.11 leak-before-burst (LBB), n—a design approach in
3.5.1 a—the physical dimension of a discontinuity, flaw or
which, at and below MAWP, potentially pre-existing flaws in
target—can be its depth, surface length, or diameter of a
themetallicliner,shouldtheygrow,willgrowthroughtheliner
circulardiscontinuity,orradiusofsemi-circularorcornercrack
and result in more gradual pressure-relieving leakage rather
having the same cross-sectional area.
than a more abrupt Burst-Before-Leak (BBL) rupture.
3.5.2 a —the size of an initial, severe, worst case crack-like
3.4.12 marked service pressure, n—pressure for which a
discontinuity, also known as a rogue flaw.
vessel is rated; normally this value is stamped on the vessel.
3.5.3 a —the size of a severe crack-like discontinuity that
crit
3.4.13 maximum allowable working pressure (MAWP),
causes LBB or BBL failure often caused by a growing rogue
n—the maximum operating pressure, to which operational
flaw.
personnel may be exposed, for a pressure vessel; this pressure
is synonymous with Maximum Expected Operating Pressure
3.5.4 a —the discontinuity size that can be detected with
p
(MEOP), as used and defined in ANSI/AIAA S-080 or ANSI/ probability p.
AIAA S-081.
3.5.5 a —the discontinuity size that can be detected with
p/c
3.4.14 maximum design pressure (MDP), n—the highest probability p with a statistical confidence level of c.
pressure defined by maximum relief pressure, maximum regu-
3.5.6 â—(pronounceda-hat)measuredresponseoftheNDT
lator pressure, or maximum temperature.
system,toatargetofsize, a.Unitsdependontestingapparatus,
3.4.14.1 Discussion—Transient pressures should be consid-
and can be scale divisions, counts, number of contiguous
ered.WhendeterminingMDP,themaximumtemperaturetobe
illuminated pixels, millivolts, etc.
experienced during a launch abort to a site without cooling
facilitiesshouldalsobeconsidered.Indesigning,analyzing,or
4. Significance and Use
testingpressurizedhardware,loadsotherthanpressurethatare
4.1 The goal of the NDT is to detect defects that have been
present should be considered and added to the MDP loads as
implicated in the failure of the COPV metal liner, or have led
appropriate. MDP in this standard is to be interpreted as
to leakage, loss of contents, injury, death, or mission, or a
including the effects of these combined loads when the
combination thereof. Liner defects detected by NDT that
non-pressure loads are significant. Where pressure regulators,
require special attention by the cognizant engineering organi-
relief devices, or a thermal control system (for example,
zation include through cracks, part-through cracks, liner
heaters), or combinations thereof, are used to control pressure,
buckling,pitting,thinning,andcorrosionundertheinfluenceof
collectively they should be two-fault tolerant from causing the
cyclic loading, sustained loading, temperature cycling, me-
pressure to exceed the MDP of the system.
chanical impact and other intended or unintended service
3.4.15 minimum detectable crack size, n—the size of the
conditions.
smallestcrack-likediscontinuitythatcanbereadilydetectedby
NDTproceduresandwhichisassumedtoexistinapartforthe NOTE 3—Liners made from stainless steel and nickel-based alloys
exhibit a higher damage resistance to impact than those made from
purpose of performing a damage tolerance safe-life or POD
aluminum.
analysis of the part, component, or assembly.
NOTE 4—Safe life is the goal for any COPV so that a through crack in
3.4.16 miss, n—an existing discontinuity that is missed
the liner will not develop during the service life.
during a POD examination. NOTE 5—The use a material with good fatigue and slow crack growth
characteristics is important. For example, nickel-based alloys are better
3.4.17 NDT reliability, n—the reliability of an NDT proce-
than precipitation-hardened stainless steel. Aluminum also has good
dure is determined by: (1) the reproducibility—NDT system
ductility and crack resistance.
standardization; (2) the capability—POD; and (3) the
4.2 The COPVs covered in this guide consist of a metallic
repeatability—process control of the applied NDT procedure.
liner overwrapped with high-strength fibers embedded in
3.4.18 normal fill pressure, n—level to which a vessel is
polymeric matrix resin (typically a thermoset). Metallic liners
pressurized; this may be greater, or may be less, than marked
may be spun formed from a deep drawn/extruded monolithic
service pressure.
blank or may be fabricated by welding formed components.
3.4.19 probability of detection (POD), n—themeanfraction Designers often seek to minimize the liner thickness in the
of flaws at a given size or other characteristic such as stress interest of weight reduction. COPVliner materials used can be
intensity factor expected to be detected. aluminumalloys,titaniumalloys,nickel-chromiumalloys,and
E2982 − 21
stainless steels, impermeable polymer liner such as high 4.6.2 Per the discretion of the cognizant engineering
density polyethylene, or integrated composite materials. Fiber organization, NDT for fracture control of COPVs should
materialscanbecarbon,aramid,glass,PBO,metals,orhybrids follow additional general and detailed guidance described in
(two or more types of fiber). Matrix resins include epoxies, MIL-HDBK-6870, NASA-STD-5019, MSFC-RQMT-3479, or
cyanate esters, polyurethanes, phenolic resins, polyimides ECSS-E-30-01A, or a combination thereof, not covered in this
(including bismaleimides), polyamides and other high perfor- guide.
mance polymers. Common bond line adhesives are generally
4.6.3 Hardware that is proof tested as part of its acceptance
epoxies (FM-73, West 105, and Epon 862) or urethanes with (that is, not screening for specific flaws) should receive
thicknesses ranging from 0.13 mm (0.005 in.) to 0.38 mm
post-proof NDT at critical welds and other critical locations.
(0.015 in.). Metal liner and composite overwrap materials
4.7 Discontinuity Types—Specific discontinuity types are
requirementsarefoundinANSI/AIAAS-080andANSI/AIAA
associated with the particular processing, fabrication and
S-081, respectively. Pictures of representative COPVs are
service history of the COPV. COPV composite overwraps can
shown in Guide E2981.
have a myriad of possible discontinuity types, with varying
4.3 The operative failure modes COPV metal liners and degrees of importance in terms of effect on performance (see
metal PVs, in approximate order of likelihood, are: (a) fatigue 4.7inGuideE2981).Asfordiscontinuitiesinthemetallicliner,
cracking, (b) buckling, (c) corrosion, (d) environmental the primary concern from an NDT perspective is to detect
cracking, and (e) overload. discontinuities that can develop cracks or reduce residual
NOTE 6—For launch vehicles and satellites, the strong drive to reduce strength of the liner below the levels required, within the
weight has pushed designers to adopt COPVs with thinner metal liners.
context of the life cycle. Therefore, discontinuities should be
Unfortunately, this configuration is more susceptible to liner buckling.
categorized as follows:
Therefore, as a precursor to liner fatigue, attention should be paid to liner
4.7.1 Inherent material discontinuities: inclusions, grain
buckling.
boundaries, etc., detected during (a) and (b) of 5.5.
4.4 Per MIL-HDBK-340, the primary intended function of
COPVs as discussed in this guide will be to store pressurized
NOTE 8—Inherent material discontinuities are generally much smaller
than the damage-tolerance limit size.Any design that does not satisfy this
gases and fluids where one or more of the following apply:
statement should be revised. Quality control procedures in place in the
4.4.1 Contains stored energy of 19 310 J (14 240 ft-lbf) or
manufacturing process should eliminate any source materials that do not
greater based on adiabatic expansion of a perfect gas.
satisfy specifications.
4.4.2 Contains a gas or liquid that would endanger person-
4.7.2 Manufacturing-induced discontinuities: caused by
nel or equipment or create a mishap (accident) if released.
welding, machining, heat treatment, etc., detected during (b)
4.4.3 Experiences a design limit pressure greater than 690
and (c) of 5.5.
kPa (100 psi).
NOTE 9—Manufacturing-induced discontinuities depend on the manu-
4.5 Per NASA-STD-(I)-5019, COPVs should comply with
facturing process, and can include machining marks, improper heat
the latest revision of ANSI/AIAA S-081. The following re-
treatment, and weld-related discontinuities such as lack of fusion,
quirements also apply when implementing S-081:
porosity, inclusions, zones of local material embrittlement, shrinkage, and
cracking.
4.5.1 Maximum Design Pressure (MDP) should be substi-
tuted for all references to Maximum Expected Operating
4.7.3 Service-induced discontinuities: fatigue, corrosion,
Pressure (MEOP) in S-081.
stress corrosion cracking, wear, accidental damage, etc. de-
4.5.2 COPVs shall have a minimum of 0.999 probability of
tected during (d) and (e) of 5.5 (after the COPV has been
no stress rupture failure of the composite shell during the
installed). In these cases, NDT should either be made on a
service life.
“remove and inspect” or “in-situ” basis depending on the
procedure and equipment used.
NOTE 7—For other aerospace applications, the cognizant engineering
organization should select the appropriate probability of survival, for
4.8 A conservative damage-tolerance life assessment is
example, 0.99, 0.999, 0.9999, etc., depending on the anticipated failure
madebyassumingtheexistenceofacrack-likediscontinuityor
mode, damage tolerance, safety factor, or consequence of failure, or a
system of discontinuities, and determining the maximum size
combinationthereof.Forexample,aprobabilityofsurvivalof0.99means
thatonaverage,1in100COPVswillfail.COPVsexhibitingcatastrophic or other characteristic of this discontinuity(s) that can exist at
failuremodes(BBLcompositeshellstressruptureversusLBBlinerleak),
the time the vessel is placed into service but not progress to
lower damage tolerance (cylindrical versus spherical vessels), lower
failureundertheexpectedserviceconditions.Thisthendefines
safety factor, and high consequence of failure will be subject to more
the dimensions or other characteristics of the crack or crack-
rigorous NDT.
like discontinuity or system of crack-like discontinuities that
4.6 Application of the NDT procedures discussed in this
should be detected by NDT.
standard is intended to reduce the likelihood of liner failure,
NOTE 10—Welding or machining may result in non-crack like flaws/
commonly denoted leak before burst (LBB), characterized by
imperfections/conditions that may be important, and NDT choices for
these flaws/imperfections/conditions may be different than for crack-like
leakageandlossofthepressurizedcommodity,thusmitigating
ones.
or eliminating the attendant risks associated with loss of the
pressurized commodity, and possibly mission.
4.9 Acceptance Criteria—Determination about whether a
4.6.1 NDTis done on fracture-critical parts such as COPVs COPV meets acceptance criteria and is suitable for aerospace
to establish that a low probability of preexisting flaws is service should be made by the cognizant engineering organi-
present in the hardware. zation. When examinations are performed in accordance with
E2982 − 21
this guide, the engineering drawing, specification, purchase safely exist. This establishes the defect criteria: all disconti-
order, or contract should indicate the acceptance criteria. nuities equal to or larger than the minimum size or have
4.9.1 Accept/reject criteria should consist of a listing of the J-integral or other applicable fracture mechanics-based criteria
expected kinds of imperfections and the rejection level for that will result in failure of the vessel within the expected
each.
servicelifeareclassifiedasdefectsandshouldbeaddressedby
4.9.2 The classification of the articles under test into zones the cognizant engineering organization.
for various accept/reject criteria should be determined from
4.11.1 Design Requirements—COPV design requirements
contractual documents.
related to the metallic liner are given in ANSI/AIAA S-080.
4.9.3 Rejection of COPVs—Ifthetype,size,orquantitiesof
The key requirement is the stipulation that the PV or COPV
defectsarefoundtobeoutsidetheallowablelimitsspecifiedby
thin-walled metal liner should exhibit an LBB failure mode or
the drawing, purchase order, or contract, the composite article
should possess adequate damage tolerance life (safe-life), or
should be separated from acceptable articles, appropriately
both. The overwrap design should be such that, if the liner
identified as discrepant, and submitted for material review by
develops a leak, the composite will allow the leaking fluid
the cognizant engineering organization, and given one of the
(liquidorgas)topassthroughitsothattherewillbenoriskof
following dispositions; (1) acceptable as is, (2) subject to
composite rupture.
further rework or repair to make the materials or component
4.12 Probability of Detection (POD)—Detailed instruction
acceptable,or (3)scrapped(madepermanentlyunusable)when
for assessing the reliability of NDT data using POD of a
required by contractual documents.
complex structure such as a COPV is beyond the scope of this
4.9.4 Acceptance criteria and interpretation of result should
guide. Therefore, only general guidance is provided. More
be defined in requirements documents prior to performing the
detailed instruction for assessing the capability of an NDT
examination. Advance agreement should be reached between
procedureintermsofthePODasafunctionofflawsize, a,can
the purchaser and supplier regarding the interpretation of the
be found in MIL-HDBK-1823. The statistical precision of the
results of the examinations. All discontinuities having signals
estimated POD(a) function (Fig. 1) depends on the number of
that exceed the rejection level as defined by the process
examination sites with targets, the size of the targets at the
requirements documents should be rejected unless it is deter-
examination sites, and the basic nature of the examination
mined from the part drawing that the rejectable discontinuities
result (hit/miss or magnitude of signal response).
will not remain in the finished part.
4.12.1 Given that a has become a de facto design
90/95
4.10 Certification of PVs—ANSI/AIAA S-080 defines the
th
criterion, it is important to estimate the 90 percentile of the
approachfordesign,analysis,andcertificationofmetallicPVs.
POD(a) function more precisely than lower parts of the curve.
4.11 Certification of COPVs—ANSI/AIAA S-081 defines
Thiscanbeaccomplishedbyplacingmoretargetsintheregion
the approach for design, analysis, and certification of COPVs,
ofthe a valuebutwitharangeofsizessotheentirecurvecan
while ANSI/AIAA S-080 defines the approach for design,
still be estimated.
analysis, and certification of PVs. More specifically, the PV or
COPV thin-walled metal liner should exhibit a leak before NOTE 11—a for a metallic liner and generation of a POD(a)
90/95
function is predicated on the assumption that critical initial flaw size
burst (LBB) failure mode or shall possess adequate damage
(CIFS)foralinerofagiventhicknesscanbedetectedwithacapabilityof
tolerance life (safe-life), or both, depending on criticality and
90/95 (90 percent probability of detection at a 95 percent confidence
whether the application is for a hazardous or nonhazardous
level).ThisisproblematicforCOPVswithverythinmetalliclinerswhere
fluid. Consequently, the NDT procedure should detect any
the CIFS will be smaller than the minimum detectable flaw sizes given in
Table 1 in NASA-STD-5009. At this limit of detection (CIFS < a ),
discontinuity that can cause burst at expected operating con-
90/95
a will have no validity for a thin-walled COPV.
90/95
ditions during the life of the COPV. The Damage-Tolerance
Liferequiresthatanydiscontinuitypresentinthelinerwillnot 4.12.2 NASA-STD-5009 defines typical limits of NDT
grow to failure during the expected life of the COPV. Fracture capability for a wide range of NDT procedures and applica-
mechanics assessment of crack growth is the typical approach tions. Given the defect criteria established by the Damage-
used for setting limits on the sizes of discontinuities that can ToleranceLiferequirementsandthepotentialdiscontinuitiesto
FIG. 1 Probability of Detection as a Function of Flaw Size, POD(a), Showing the Location of the Smallest Detectable Flaw and a (Left);
POD(a) With Confidence Bounds Added and Showing the Location of a (Right)
90/95
E2982 − 21
be detected, NASA-STD-5009 can be used to select NDT 4.12.6.2 For detailed test program guidance; specimen
procedures that are likely to achieve the required examination design, fabrication, documentation, and maintenance; statisti-
capability. cal analysis of NDT data; model-assisted determination of
POD; special topics; and related documents, consult MIL-
NOTE 12—NDT of fracture critical hardware should detect the initial
HDBK-1823, Appendices E through J, respectively.
crack sizes used in the damage tolerance fracture analyses with a
capability of 90/95. The minimum detectable crack sizes for the standard
4.13 NDT Data Reliability—MIL-HDBK-1823 provides
NDT procedures shown in Table 1 of NASA-STD-5009 meet the 90/95
nonbinding guidance for estimating the detection capability of
capability requirement. The crack size data in Table 1 of NASA-STD-
NDT procedures for examining either new or in-service hard-
5009arebasedprincipallyonanNDTcapabilitystudythatwasconducted
ware for which a measure of NDT reliability is needed.
on flat, fatigue-cracked 2219-T87 aluminum panels early in the Space
Shuttle program.Although many other similar capability studies and tests
SpecificguidanceisgiveninMIL-HDBK-1823forET,PT,and
have been conducted since, none have universal application, neither
UT.MIL-HDBK-1823maybeusedforotherNDTprocedures,
individually or in combination. Conducting an ideal NDT capability
such as RT or Profilometry, provided they provide either a
demonstration where all of the variables are tested is obviously unman-
quantitative signal, â, or a binary response, hit/miss. Because
ageable and impractical.
the purpose is to relate POD with target size (or any other
4.12.3 Aspect Ratio and Equivalent Area Considerations—
meaningful feature like chemical composition), “size” (or
Current standards governing aerospace metallic pressure ves-
feature characteristic) should be explicitly defined and be
sels (ANSI/AIAA S-080) and COPV liners (ANSI/AIAA
unambiguouslymeasurable,thatis,othertargetshavingsimilar
S-081)requirethatfractureanalysisbeperformedtodetermine
sizes will produce similar output from the NDT equipment.
the CIFS for cracks having an aspect ratio ranging from 0.1 to
This is especially important for amorphous targets like corro-
0.5. However, there is insufficient data to support the approach
sion damage or buried inclusions with a significant chemical
of testing at only one aspect ratio and then using an equivalent
reaction zone. Other literature on NDTdata reliability is given
area approach to extend the results to the required range of
elsewhere (2-7).
aspect ratios (1-9). Accordingly, POD testing on metallic
NOTE14—AEasgenerallypracticeddoesnotyieldthesizeofaflawin
COPVlinersshouldbeperformedattheboundsoftherequired
a metallic liner of a COPV; however, can be used for accept-reject of
range of crack aspect ratios.
COPVs (see Section 7 in both this guide and Guide E2981).
4.14 Further Guidance—Additional guidance for fracture
NOTE13—Caution:Tominimizemass,designersofaerospacesystems
are reducing the wall thickness for metallic pressure vessels and COPV
control is provided in other governmental documents (NASA-
liners. This reduction in wall thickness produces higher net section
STD-5003, SSP 30558, SSP 52005, NSTS 1700.7B), and
stresses, for a given internal pressure, resulting in smaller CIFS. These
non-government documents (NTIAC-DB-97-02, NTIAC-TA-
smaller crack sizes approach the limitations of current NDT. Failure to
00-01).
adequately demonstrate the capabilities of a given NDT procedure over
the required range of crack aspect ratios may lead to the failure to detect
5. Basis of Application
a critical flaw resulting in a catastrophic tank failure.
5.1 Personnel Certification—NDT personnel should be cer-
4.12.4 To provide reasonable precision in the estimates of
tified in accordance with a nationally or internationally recog-
the POD(a) function, experience suggests that the specimen
nized practice or standard such asANSI/ASNT-CP-189, SNT-
test set contain at least 60 targeted sites if the system provides
TC-1A, NAS 410, ISO 9712 or a similar document. The
only a binary, hit/miss response and at least 40 targeted sites if
practiceorstandardusedanditsapplicablerevisionsshouldbe
the system provides a quantitative target response, â. These
specified in any contractual agreement between the using
numbers are minimums.
parties.
4.12.5 For purposes of POD studies, the NDT procedure
should be classified into one of three categories: 5.2 Personnel Qualification—NDT personnel should be
4.12.5.1 Those which produce only qualitative information qualified by accepted training programs, applicable on-the-job
as to the presence or absence of a flaw, that is, hit/miss data, trainingunderacompetentmentororcomponentmanufacturer.
4.12.5.2 Those which also provide some quantitative mea- Cognizant engineering organization and manufacturer qualifi-
sure of the size of
...