1.1 This Practice discusses nondestructive testing (NDT) methods for detecting defects and flaws in thin-walled metallic pressure vessels (PVs) and composite overwrapped pressure vessels (COPVs) used in aerospace applications. In general, these COPVs have metal liner thicknesses less than 2.3 mm (0.090 in.) and a filament wound composite overwrap. 1.2 Although this Practice focuses on PVs and COPVs used at ambient temperature, it also has relevance to a) composite pressure vessels (CPVs), and b) COPVs and CPVs used at cryogenic temperatures. NDT of the composite overwrap of COPVs is beyond the scope of the Practice, however, a general overview of applicable NDT methods is provided in Guide E2533. 1.3 This Practice applies primarily to high pressure COPVs used for storing compressed gases at MAWPs up to 400 bar (6,000 psia) and volumes down to 8000 cm3 (500 in.3), but also has applicability to low pressure metallic PVs used for storing liquid propellants at maximum allowable working pressures (MAWPs) up to 35 bar (500 psia) and volumes up to 2 m3 (70 ft3) . 1.4 This Practice describes the application of established NDT methods; namely, acoustic emission (AE), eddy current (EC), magnetic particle (MP), penetrant testing (PT), radiography (RT), ultrasound (UT), and visual inspection (VI) methods (including borescopy and laser profilometry). 1.5 Wherever possible, the NDT methods described shall be sensitive enough to detect critical flaw sizes of the order of 1.3 mm (0.050-in.) length and greater with a 2/1 aspect ratio. 1.6 Although visual NDT methods are discussed, emphasis is placed on NDT methods that are sensitive to detecting damage caused by impacts at energy levels which leave no visible indication on the COPV surface. 1.7 This Practice does not specify accept-reject criteria and is not intended to be used as a means for approving filament-wound pressure vessels for service. 1.8 This Practice references established ASTM Test Methods that have a foundation of experience and that yield a numerical result, and new procedures that have yet to be validated which are better categorized as qualitative guidelines and practices. The latter are included to promote research and later elaboration in this Standard as methods of the former type. 1.9 To insure proper use of the referenced standard documents, there are recognized NDT specialists that are certified according to industry and company NDT specifications. It is recommended that a NDT specialist be a part of any composite component design, quality assurance, in service maintenance or damage examination. 1.10 The values stated in metric units are to be regarded as the standard. The English units given in parentheses are provided for information only.
The need for this standard was identified during the Denver 2008 Workshop on NDT of COPVs, and during follow-on E07.10 TG on NDE of Aerospace Composites meetings held in 2009 and 2010. Such a standard would also augment NASAs usage of COPVs in mission critical applications on the ISS and future programs. Currently there are no standards which specify accept-reject criteria determined using NDE to ascertain the health of high pressure COPVs during service. Consensus standards are not available for NDE of metallic liners during the COPV manufacturing phase, especially after autofrettage. This standard is intended to fill in these gaps, and will specify NDE procedural detail relevant to 90/95 POD requirements whenever possible, either as accept-reject criteria for COPV designs, or NDE measurements that constitute grounds for caution, removal from service, and further NDE. The planned standard would be used by both COPV manufacturers, and end users like NASA and the DOD, but would would be be of peripheral interest to the CPV and automotive COPV industries (potential DOT application). The Standard will be drafted initially as a Practice, but may later evolve into a Test Method.
Keywordsacoustic emission; composite overwrapped pressure vessel; composite pressure vessel; eddy current; filament wound pressure vessel; metal liner; magnetic particle; dye penetrant testing; radiography; ultrasound; visual inspection
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
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