1、STP/PT-005DESIGN FACTORGUIDELINES FORHIGH PRESSURECOMPOSITEHYDROGEN TANKSSTP/PT-005 DESIGN FACTOR GUIDELINES FOR HIGH-PRESSURE COMPOSITE HYDROGEN TANKS Prepared by: Becht Engineering Co., Inc. 22 Church Street, P.O. Box 300 Liberty Corner, New Jersey 07938 Date of Issuance: August 1, 2006 This repor
2、t was prepared as an account of work sponsored by the National Renewable Energy Laboratory (NREL) and the ASME Standards Technology, LLC (ASME ST-LLC). Neither ASME, ASME ST-LLC, Becht Engineering Co., Inc., nor others involved in the preparation or review of this report, nor any of their respective
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9、tandards Technology, LLC Three Park Avenue, New York, NY 10016-5990 ISBN No. 0-7918-3038-1 Copyright 2006 by ASME Standards Technology, LLC All Rights Reserved Design Factor Guidelines for High-Pressure Composite H2Tanks STP/PT-005 TABLE OF CONTENTS FOREWORD. iv ABSTRACT vi 1 INTRODUCTION . 1 2 DEFI
10、NITIONS. 2 3 BASIC ASSUMPTIONS FOR THE RECOMMENDED DESIGN FACTORS. 3 3.1 Basic Tank Design. 3 3.1.1 Seam Welded Versus Seamless Tanks and Liners. 3 3.1.2 Liner Stress Limits . 3 3.1.3 Limited Life 3 3.1.4 Nozzles . 3 3.1.5 Effect of Hydrogen on Materials 4 3.1.6 Fatigue Calculations. 4 3.1.7 Environ
11、mental Effects 4 3.2 Prototype Tests and Design Verification. 4 3.2.1 Performance Testing. 4 3.2.2 Fatigue Testing. 4 3.2.3 Damage Resistance 4 3.2.4 Fire Resistance . 4 3.2.5 Short-term (Static) Versus Long-term 5 3.3 Manufacturing Controls and Tests 5 3.3.1 Examination . 5 3.3.2 Lot Testing . 5 3.
12、3.3 Pressure Testing . 5 3.4 In-Service Inspection. 5 4 STATIC DESIGN FACTORS IN RELATED CODES 7 5 LONG-TERM DESIGN FACTOR 10 6 RECOMMENDED DESIGN FACTORS FOR COMPOSITE TANKS . 12 7 RECOMMENDED SHORT-TERM (STATIC) DESIGN FACTOR FOR COMPOSITE TANKS 13 8 RECOMMENDATIONS FOR R it does not include vehic
13、le fuel tanks. The report provides recommended design factors relative to short-term burst pressure and interim margins for long-term stress rupture based on a fixed 15-year design life for fully wrapped and hoop wrapped composite tanks with metal liners. These recommended margins are based on the p
14、roven experience with existing standards for composite reinforced tanks. Recommendations for further research are also provided, in particular for development of rules that would provide design life dependent design factors relative to stress rupture that would provide a means to design for longer o
15、r shorter lives than 15 years, and to provide a method for the manufacturer to determine, by testing, the stress ratio for their fiber reinforcement system.vi Design Factor Guidelines for High-Pressure Composite H2Tanks STP/PT-005 1 INTRODUCTION This report provides recommendations to the ASME Hydro
16、gen Project Team for design factors for composite hydrogen tanks. The scope of this study included stationary (e.g., storage) and transport tanks; it does not include vehicle fuel tanks. The report provides recommended design factors relative to short-term burst pressure and interim margins for long
17、-term stress rupture based on a fixed 15-year design life for fully wrapped and hoop wrapped composite tanks with metal liners. These recommended margins are based on the proven experience with existing standards for composite reinforced tanks. Recommendations for further research are also provided,
18、 in particular for development of rules that would provide design life dependent design factors relative to stress rupture that would provide a means to design for longer or shorter lives than 15 years, and to provide a method for the manufacturer to determine, by testing, the stress ratio for their
19、 fiber reinforcement system. Because different terms are used in different standards for the same condition, this report starts by establishing a consistent set of definitions in section 2. Terms such as Working Pressure and Maximum Permissible Operating Pressure are adopted in this report, to be co
20、nsistent with a draft ISO standard, ISO/DIS 10286:2004, Gas Cylinders - Terminology. In making the recommendations for margins relative to short-term and long-term burst, a clear decision as to what is included in those margins, or what is not, is required. There may be an interrelationship between
21、the appropriate burst margin and other Code rules. Section 3 documents the assumptions made that led to the recommended margins. Sections 4 and 5 review design factors for short-term burst and long-term stress rupture in existing, related codes and standards. The evaluation of relevant existing code
22、s is the basis for the recommended margins for the initial draft of the codes for hydrogen storage and transport tanks. Section 6 compares transport tanks with stationary tanks. The recommended margins, both for the initial draft of the standards, and a recommended approach for the future, are outli
23、ned in section 7. Research and development is required to establish the technology necessary to implement the recommended approach for the future. Recommendations for this research are provided in section 8. 1 STP/PT-005 Design Factor Guidelines for High-Pressure Composite H2Tanks 2 DEFINITIONS Auto
24、frettage: For metallic vessels, autofrettage is a process for producing a system of favorable residual stresses in a thick-walled pressure vessel by pressurizing it to produce plastic deformation in part or all of the wall thickness. For composite tanks, autofrettage is a process in which the tank i
25、s pressurized sufficiently to yield the metallic liner, such that the liner will be in compression due to the elastic response of the fiber reinforcement when the tank is not pressurized. The process is intended to improve the fatigue resistance of the liner but is not expected to affect the short-t
26、erm burst pressure. Burst Pressure: The minimum pressure at which the tank will fail due to excessive pressure. This is verified by prototype design qualification testing of the tanks. Burst Ratio: The ratio of the minimum burst pressure to a specific lower pressure. For stationary tanks, this repor
27、t recommends that the lower pressure be the MAWP; for transport tanks, this report recommends that the lower pressure be the Working Pressure. Fully Wrapped: A composite tank with fibers wrapped to provide both hoop reinforcement and longitudinal reinforcement. Hoop Wrapped: A composite tank with ci
28、rcumferentially oriented fibers wrapped to reinforce the liner cylinder. The longitudinal strength of the tank is entirely from the liner. Maximum Allowable Working Pressure (MAWP): This is used for stationary tanks. The maximum pressure the tank will be subjected to (except for accumulation during
29、a pressure relieving event) at any time in service. This is limited by the pressure setting of the pressure relief device (rupture disk or relief valve). Maximum Permissible Operating Pressure (MPOP): This is used for transport tanks, and is also termed “Developed Pressure.” Typically, this must not
30、 exceed 125% of the Working Pressure. This is the pressure developed during filling of the tank and while the tank is at the maximum ambient temperature while in service. Normal Operating Pressure: The pressure at which a tank is expected to operate for most of its life. It does not include short-te
31、rm variations in pressure. Short-term (Static) Burst Pressure: The pressure at which the tank will fail due to excessive pressure at the time of manufacture. Stress Ratio: The ratio of the stress in the reinforcing fibers at Working Pressure to the initial ultimate (tensile) strength of the fibers,
32、as demonstrated by short-term burst tests. Test Pressure: The required pressure that each tank must be tested to at the time of manufacture. Working Pressure: For transport tanks, this is the maximum settled pressure at 21.1oC (70oF) to which the tank may be filled. For stationary tanks, this is the
33、 expected normal operating pressure for the tank. 2 Design Factor Guidelines for High-Pressure Composite H2Tanks STP/PT-005 3 BASIC ASSUMPTIONS FOR THE RECOMMENDED DESIGN FACTORS In making the recommendations for margins relative to short-term and long-term burst, a clear decision as to what is incl
34、uded in those margins, or what is not, is required. There may be an interrelationship between the appropriate burst margin and other Code rules. As such, this section documents the assumptions made that led to the recommended margins. 3.1 Basic Tank Design 3.1.1 Seam Welded Versus Seamless Tanks and
35、 Liners While DOT has traditionally required seamless tanks for high-pressure transport tanks, seam welded liners, such as permitted in Code Case 2390, will be required for larger-diameter tanks. The recommendations on margins presume that seam welded liners will be permitted. While it is logical to
36、 presume that such welds will be subjected to sufficient volumetric and other examination to effectively give them a weld efficiency of 100%, no presumption on this was made. If welds of lower quality are permitted by the rules, knockdown factors that result in heavier wall construction will be requ
37、ired. It was presumed that the prototype tanks for burst and fatigue testing would have welds, if any, of the same type and using the same procedures as the production tanks. 3.1.2 Liner Stress Limits Some codes have specific stress limits for the liner, together with requirements relative to the bu
38、rst pressure for the completed tank. The recommendations in this report for margins relative to burst pressure do not require stress limits in the liner. The performance testing of the tanks with respect to short-term burst and fatigue testing adequately test the liner. While limitations on liner st
39、ress are required to successfully pass such prototype testing, the prototype testing is judged to adequately prove the design, and limitations on liner stress are necessary to pass the prototype testing. It is not necessary to provide an additional code requirement. 3.1.3 Limited Life The fibers are
40、 subject to stress rupture and as such may have a limited life. Accordingly, the tanks must be assigned a limited life. At present, there are no Nondestructive Evaluation (NDE) methods that have been proven to be reliable for determining the degree of damage, or portion of life consumed in the mater
41、ial, after a period of operation 2. Until such time as examination or other techniques are available to confirm fitness for continued service after the design life has been reached, it is assumed that a design life will be assigned to each tank, and that the tank will be retired after it reaches its
42、 design life. The design factors relative to long-term burst failure presume that the tank will be retired once it reaches its design life. Note that specific research activities are recommended to develop a method to determine a design life dependent design factor for fiber stress. It is possible t
43、hat the development of such rules, together with time dependent testing of specific fiber materials, will permit extension of the lives of tanks. This would occur in cases where the margin used for original design is later found to be suitable for a longer design life than provided in the original c
44、onstruction code. 3.1.4 Nozzles The tanks envisioned for these rules are of simple construction. It was assumed that there would be no side nozzles; that all nozzles would be at the ends, and would generally be polar. 3 STP/PT-005 Design Factor Guidelines for High-Pressure Composite H2Tanks 3.1.5 Ef
45、fect of Hydrogen on Materials The effect of hydrogen will depend upon the material selected. The effect of hydrogen should be addressed elsewhere in the rules, such as in material selection, fatigue, and toughness requirements. 3.1.6 Fatigue Calculations The recommendations in this report do not pre
46、sume that fatigue calculations will be performed. The fatigue demonstration testing of prototype tanks is considered to be sufficient. 3.1.7 Environmental Effects While environmental effects such as exposure of the fibers to moisture and ultraviolet (UV) exposure can be a significant consideration i
47、n design, these are not a consideration in establishing the margin relative to burst. Protection may be provided by coatings or other measures. 3.2 Prototype Tests and Design Verification 3.2.1 Performance Testing The recommended margin presumes that burst testing of prototype tanks will be required
48、 by the rules. This provides important assurance of proper design, in particular for fiber reinforced composite tanks. The design factors that are recommended are consistent with proven experience for tanks constructed to codes for composite tanks that require prototype burst testing. 3.2.2 Fatigue
49、Testing Fatigue performance and margin against burst are considered herein to be two separate, although related, issues. Measures such as autofrettage can be taken to improve fatigue performance, but autofrettage has no effect on burst pressure. The recommendations made herein assume that detailed fatigue qualification rules will be provided, including fatigue performance testing of prototype tanks. The design factors that are recommended are consistent with proven experience for composite tanks constructed to codes that require prototype fatigue testing. It is assumed that fatigue testing
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