GB/T 4732.6-2024 Pressure vessels design by analysis - Part 6: Fabrication, inspection and testing and acceptance
1 Scope
This document specifies the requirements for the fabrication, inspection and testing, and acceptance of steel pressure vessels designed by analysis.
This document is applicable to the fabrication, inspection and testing, and acceptance of steel pressure vessels, and non-alloy, low-alloy or high-alloy steel substrate of clad plate pressure vessels with nickel and nickel alloys as cladding, lining or surfacing layers, lined pressure vessels, and pressure vessels with surfacing layer.
This document is applicable to single-layer welded (including tubular cylindrical shell) pressure vessels, forged-welded pressure vessels, shrink fit pressure vessels, multilayer-wrapped (including multi-layer cylindrical shell sections wrapped, and multi-layer integrally wrapped) pressure vessels, and flat steel ribbon wound pressure vessels.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 150.1 Pressure vessels - Part 1: General requirements
GB/T 150.2 Pressure vessels - Part 2: Materials
GB/T 150.3 Pressure vessels - Part 3: Design
GB/T150.4 Pressure vessels - Part 4: Fabrication, inspection and testing, and acceptance
GB/T 151 Heat exchangers
GB/T 196 General purpose metric screw threads - Basic dimensions
GB/T 197 General purpose metric screw threads - Tolerances
GB/T228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature
GB/T 228.2 Metallic materials - Tensile testing - Part 2: Method of test at elevated temperature
GB/T 229 Metallic materials - Charpy pendulum impact test method
GB/T 232 Metallic materials - Bend test
GB/T 1804 General tolerances - Tolerances for linear and angular dimensions without individual tolerance indications
GB/T 1954 Methods of measurement for ferrite content in austenitic Cr-Ni stainless steel weld metals
GB/T 2039 Metallic materials - Uniaxial creep testing method in tension
GB/T 3965 Determination of diffusible hydrogen in deposited metal
GB/T 4732.1 Pressure vessels design by analysis - Part 1: General requirements
GB/T 4732.2 Pressure vessels design by analysis - Part 2: Materials
GB/T 4732.3 Pressure vessels design by analysis - Part 3: Formulae method
GB/T 6396 Clad steel plates - Mechanical and technological test
GB/T 8923.1 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings
GB/T 12337 Steel spherical tanks
GB/T 16749 Bellows expansion joints for pressure vessel
GB/T 21433 Detecting susceptibility to intergranular corrosion in stainless steel pressure vessels
GB/T 25198 Heads for pressure vessels
GB/T 30583 Specification for post weld heat treatment of pressure equipment
GB/T 39255 Gases and gas mixtures for welding and cutting processes
HG/T 20592~20635 Steel pipe flanges, gaskets and bolting
JB/T 3223 Welding consumables quality management procedures
JB/T 4756 Nickel and nickel alloy pressure vessels
NB/T 10558 Coating and packing for pressure vessels transport
NB/T 11025 Reinforcing pad
NB/T 47002.1 Clad plate for pressure vessel - Part 1: Stainless steel-steel clad plate
NB/T 47002.2 Clad plate for pressure vessel - Part 2: Nickel-steel clad plate
NB/T 47013
(All parts) Nondestructive testing of pressure equipments
NB/T 47014 Welding procedure qualification for pressure equipments
NB/T 47015 Welding specification for pressure vessels
NB/T 47016 Mechanical property tests of product welded test coupons for pressure equipment
NB/T 47018
(All parts) Technical permission of welding materials for pressure equipment
NB/T 47020 Type and specification for pressure vessel flanges
NB/T 47021 A-type socket-weld flange
NB/T 47022 B-type socket-weld flange
NB/T 47023 Welding neck flange
NB/T 47024 Nonmetallic gaskets
NB/T 47025 Spiral wound gaskets
NB/T 47026 Double-jacketed gaskets
NB/T 47027 Stud blots & nuts for body flange
NB/T 47041 Vertical vessels supported by skirt
NB/T 47042 Horizontal vessels on saddle supports
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 150.1, GB/T 150.2, GB/T 150.3, GB/T 150.4, GB/T 4732.1 and GB/T 30583 and the following apply.
3.1
maximum postweld heat treatment; Max. PWHT
specific heat treatment of a test piece (or specimen) to simulate the maximum thermal cycles possible during fabrication and use
Note 1: For test pieces (or specimens) of the same austenitized and tempered heat treatment conditions as the material upon delivery, all heat treatments above 490℃ during fabrication are accumulated for the simulated heat treatment, including intermediate stress relief, all postweld heat treatments, one postweld heat treatment after repair by the manufacturer, and at least one postweld heat treatment to be conducted by the user.
Note 2: For Cr-Mo and Cr-Mo-V steels, the equivalent holding time may be calculated using the Larson-Miller Parameter for heat treatment not higher than the final postweld heat treatment temperature, and the result shall be approved in writing by the design unit.
3.2
minimum postweld heat treatment; Min. PWHT
specific heat treatment of a test piece (or specimen) to simulate the minimum thermal cycles during fabrication
Note 1: For test pieces (or specimens) of the same austenitized and tempered heat treatment conditions as the material upon delivery, all heat treatments above 490℃ during fabrication are accumulated for the simulated heat treatment, including intermediate stress relief (when not combined with PWHT) and one postweld heat treatment.
Note 2: For Cr-Mo and Cr-Mo-V steels, the equivalent holding time may be calculated using the Larson-Miller Parameter for heat treatment not higher than the final postweld heat treatment temperature, and the result shall be approved in writing by the design unit.
3.3
intermediate stress relief; ISR
process where the weldment is evenly heated to a certain temperature, held for a certain time, and then evenly cooled before the final postweld heat treatment to eliminate welding residual stress
3.4
flat steel ribbon wound cylindrical shell
cylindrical shell consisting of an liner and a steel ribbon wound layer
4 General requirements
4.1 Fabrication, inspection and testing, and acceptance requirements for pressure vessels
4.1.1 Additional requirements shall be imposed on the fabrication, inspection and testing, and acceptance of pressure vessels in different structural forms apart from those for fabrication, inspection and testing, and acceptance of single-layer welded (including tubular cylindrical shell) pressure vessels:
a) See Annex A for additional requirements for the fabrication, inspection and testing, and acceptance of forged-welded pressure vessels;
b) See Annex B for additional requirements for the fabrication, inspection and testing, and acceptance of shrink fit pressure vessels;
c) See Annex C for additional requirements for the fabrication, inspection and testing, and acceptance of multilayer-wrapped pressure vessels;
d) See Annex D for additional requirements for the fabrication, inspection and testing, and acceptance of flat steel ribbon wound pressure vessels.
4.1.2 For low temperature pressure vessels made of chromium-nickel austenitic stainless steel (designed for temperatures below -196℃), additional requirements for their fabrication, inspection and testing, and acceptance shall be specified through consultation among the parties involved in the construction and shall be stipulated in the design documents by the design unit.
4.2 Basis for the fabrication, inspection and testing, and acceptance of pressure vessels
The fabrication, inspection and testing, and acceptance of pressure vessels shall comply with the following requirements in addition to those in this document and the design documents:
a) The fabrication, inspection and testing, and acceptance of heat exchangers, spherical tanks, vertical vessels supported by skirt, and horizontal vessels on saddle supports shall comply with GB/T 151, GB/T 12337, NB/T 47041, and NB/T 47042, respectively.
b) The fabrication, inspection and testing, and acceptance of the cladding, lining or surfacing layers of nickel and nickel alloy clad plates shall also comply with JB/T 4756.
4.3 Raw materials and parts and components (including self-made, outsourced and purchased parts and components)
4.3.1 Raw materials
4.3.1.1 Plates, tubes, forgings, bars and clad plates shall be subject to the following requirements.
a) Plates, tubes, forgings, and bars shall comply with the relevant requirements of GB/T 4732.2 and JB/T 4756. Material suppliers shall provide the material manufacturer’s heat treatment process parameters for the materials as delivered.
b) Clad plates shall comply with NB/T 47002.1 and NB/T 47002.2, respectively. When heat exchange tubes are subject to axial compressive stress, if clad plates are used to manufacture tube sheets, requirements on bonding strength of the clad plates shall be specified and bonding strength tests shall be conducted in accordance with GB/T 6396.
c) For the pressure vessels within the scope of application of this document, if all pressure components are made of nickel and nickel alloy, the allowable stress shall be selected in accordance with the relevant provisions of JB/T 4756.
4.3.1.2 Welding materials shall comply with NB/T 47018 (all parts) as well as GB/T 4732.2.
4.3.2 Parts and components (including self-made, outsourced and purchased parts and components)
4.3.2.1 In addition to meeting the requirements of GB/T 25198, the heads shall also meet the following requirements.
a) Hard markings shall not be adopted for formed heads.
b) Cold-formed chromium-nickel austenitic stainless steel heads shall be tested for ferrite content using a ferrite tester along two mutually perpendicular bus bars, by referring to GB/T 1954. For ellipsoidal heads and dished heads, the test points shall include at least the apex, four points at the small-radius corner, and four points near the port on the straight edge. For conical heads, the test points shall include at least four points near the ports at the large and small ends, respectively, and four points in the middle. For hemispherical heads, the test points shall include at least the apex, four points near the port, and four points between the apex and the port. The measured ferrite content shall not be greater than 15%, and the pressure vessel manufacturer shall re-test each formed head one by one. For heads formed after plate splicing, the test parts shall include the weld seams.
c) When materials are supplied and used in the same heat treatment state, if the head forming changes the supply heat treatment state of the materials, the head manufacturer shall carry out the restorative heat treatment.
d) For heads assembled after being formed in flaps, if the assembly is not completed by the head manufacturer, the head manufacturer shall pre-assemble the heads. The inspection items and results of the pre-assembled heads shall comply with the relevant standards or technical documents for ordering.
e) For heads fabricated by means of processing with supplied materials, the performance of materials and the performance requirements for formed heads shall be agreed upon by the supplier and the purchaser, the performance of the supplied materials shall be guaranteed by the purchaser, and the performance of the formed head shall be guaranteed by the supplier.
4.3.2.2 The flanges of a pressure vessel and their components shall comply with NB/T 47020 to NB/T 47027 and the design documents.
4.3.2.3 The pipe flanges of a pressure vessel and their components shall comply with HG/T 20592 to HG/T 20635 and the design documents, and special grade fasteners shall be used.
4.3.2.4 The expansion joints for pressure vessel shall comply with GB/T 16749 and the design documents. Cold-formed chromium-nickel austenitic stainless steel expansion joints shall be tested for ferrite content using a ferrite tester along four bus bars spaced 90° apart by referring to GB/T 1954. The test points shall include at least the wave crest, wave trough, and the part between the crest and trough. The measured ferrite content shall not be greater than 15%, and the pressure vessel manufacturer shall re-test each formed expansion joint one by one. For expansion joints formed after plate splicing, the test parts shall include the weld seams.
4.3.2.5 The reinforcing pads shall comply with NB/T 11025 and the design documents.
4.3.2.6 Suppliers of purchased finished parts and components shall provide the pressure vessel manufacturer with complete and authentic product quality certificates. When requested by the pressure vessel manufacturer, the suppliers shall provide the thickness of the steel used in the finished parts and components.
Contents
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Material re-inspection, cutting and mark transplantation
6 Cold/thermal forming and assembly
7 Welding
8 Heat treatment
9 Test pieces and specimens
10 Non-destructive testing
11 Pressure test and leakage test
12 Hot gas cycle test
13 Pressure vessel factory requirements
Annex A (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of forged-welded pressure vessels
Annex B (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of shrink fit pressure vessels
Annex C (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of multilayer-wrapped pressure vessels
Annex D (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of flat steel ribbon wound pressure vessels
GB/T 4732.6-2024 Pressure vessels design by analysis - Part 6: Fabrication, inspection and testing and acceptance
1 Scope
This document specifies the requirements for the fabrication, inspection and testing, and acceptance of steel pressure vessels designed by analysis.
This document is applicable to the fabrication, inspection and testing, and acceptance of steel pressure vessels, and non-alloy, low-alloy or high-alloy steel substrate of clad plate pressure vessels with nickel and nickel alloys as cladding, lining or surfacing layers, lined pressure vessels, and pressure vessels with surfacing layer.
This document is applicable to single-layer welded (including tubular cylindrical shell) pressure vessels, forged-welded pressure vessels, shrink fit pressure vessels, multilayer-wrapped (including multi-layer cylindrical shell sections wrapped, and multi-layer integrally wrapped) pressure vessels, and flat steel ribbon wound pressure vessels.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 150.1 Pressure vessels - Part 1: General requirements
GB/T 150.2 Pressure vessels - Part 2: Materials
GB/T 150.3 Pressure vessels - Part 3: Design
GB/T150.4 Pressure vessels - Part 4: Fabrication, inspection and testing, and acceptance
GB/T 151 Heat exchangers
GB/T 196 General purpose metric screw threads - Basic dimensions
GB/T 197 General purpose metric screw threads - Tolerances
GB/T228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature
GB/T 228.2 Metallic materials - Tensile testing - Part 2: Method of test at elevated temperature
GB/T 229 Metallic materials - Charpy pendulum impact test method
GB/T 232 Metallic materials - Bend test
GB/T 1804 General tolerances - Tolerances for linear and angular dimensions without individual tolerance indications
GB/T 1954 Methods of measurement for ferrite content in austenitic Cr-Ni stainless steel weld metals
GB/T 2039 Metallic materials - Uniaxial creep testing method in tension
GB/T 3965 Determination of diffusible hydrogen in deposited metal
GB/T 4732.1 Pressure vessels design by analysis - Part 1: General requirements
GB/T 4732.2 Pressure vessels design by analysis - Part 2: Materials
GB/T 4732.3 Pressure vessels design by analysis - Part 3: Formulae method
GB/T 6396 Clad steel plates - Mechanical and technological test
GB/T 8923.1 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings
GB/T 12337 Steel spherical tanks
GB/T 16749 Bellows expansion joints for pressure vessel
GB/T 21433 Detecting susceptibility to intergranular corrosion in stainless steel pressure vessels
GB/T 25198 Heads for pressure vessels
GB/T 30583 Specification for post weld heat treatment of pressure equipment
GB/T 39255 Gases and gas mixtures for welding and cutting processes
HG/T 20592~20635 Steel pipe flanges, gaskets and bolting
JB/T 3223 Welding consumables quality management procedures
JB/T 4756 Nickel and nickel alloy pressure vessels
NB/T 10558 Coating and packing for pressure vessels transport
NB/T 11025 Reinforcing pad
NB/T 47002.1 Clad plate for pressure vessel - Part 1: Stainless steel-steel clad plate
NB/T 47002.2 Clad plate for pressure vessel - Part 2: Nickel-steel clad plate
NB/T 47013
(All parts) Nondestructive testing of pressure equipments
NB/T 47014 Welding procedure qualification for pressure equipments
NB/T 47015 Welding specification for pressure vessels
NB/T 47016 Mechanical property tests of product welded test coupons for pressure equipment
NB/T 47018
(All parts) Technical permission of welding materials for pressure equipment
NB/T 47020 Type and specification for pressure vessel flanges
NB/T 47021 A-type socket-weld flange
NB/T 47022 B-type socket-weld flange
NB/T 47023 Welding neck flange
NB/T 47024 Nonmetallic gaskets
NB/T 47025 Spiral wound gaskets
NB/T 47026 Double-jacketed gaskets
NB/T 47027 Stud blots & nuts for body flange
NB/T 47041 Vertical vessels supported by skirt
NB/T 47042 Horizontal vessels on saddle supports
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 150.1, GB/T 150.2, GB/T 150.3, GB/T 150.4, GB/T 4732.1 and GB/T 30583 and the following apply.
3.1
maximum postweld heat treatment; Max. PWHT
specific heat treatment of a test piece (or specimen) to simulate the maximum thermal cycles possible during fabrication and use
Note 1: For test pieces (or specimens) of the same austenitized and tempered heat treatment conditions as the material upon delivery, all heat treatments above 490℃ during fabrication are accumulated for the simulated heat treatment, including intermediate stress relief, all postweld heat treatments, one postweld heat treatment after repair by the manufacturer, and at least one postweld heat treatment to be conducted by the user.
Note 2: For Cr-Mo and Cr-Mo-V steels, the equivalent holding time may be calculated using the Larson-Miller Parameter for heat treatment not higher than the final postweld heat treatment temperature, and the result shall be approved in writing by the design unit.
3.2
minimum postweld heat treatment; Min. PWHT
specific heat treatment of a test piece (or specimen) to simulate the minimum thermal cycles during fabrication
Note 1: For test pieces (or specimens) of the same austenitized and tempered heat treatment conditions as the material upon delivery, all heat treatments above 490℃ during fabrication are accumulated for the simulated heat treatment, including intermediate stress relief (when not combined with PWHT) and one postweld heat treatment.
Note 2: For Cr-Mo and Cr-Mo-V steels, the equivalent holding time may be calculated using the Larson-Miller Parameter for heat treatment not higher than the final postweld heat treatment temperature, and the result shall be approved in writing by the design unit.
3.3
intermediate stress relief; ISR
process where the weldment is evenly heated to a certain temperature, held for a certain time, and then evenly cooled before the final postweld heat treatment to eliminate welding residual stress
3.4
flat steel ribbon wound cylindrical shell
cylindrical shell consisting of an liner and a steel ribbon wound layer
4 General requirements
4.1 Fabrication, inspection and testing, and acceptance requirements for pressure vessels
4.1.1 Additional requirements shall be imposed on the fabrication, inspection and testing, and acceptance of pressure vessels in different structural forms apart from those for fabrication, inspection and testing, and acceptance of single-layer welded (including tubular cylindrical shell) pressure vessels:
a) See Annex A for additional requirements for the fabrication, inspection and testing, and acceptance of forged-welded pressure vessels;
b) See Annex B for additional requirements for the fabrication, inspection and testing, and acceptance of shrink fit pressure vessels;
c) See Annex C for additional requirements for the fabrication, inspection and testing, and acceptance of multilayer-wrapped pressure vessels;
d) See Annex D for additional requirements for the fabrication, inspection and testing, and acceptance of flat steel ribbon wound pressure vessels.
4.1.2 For low temperature pressure vessels made of chromium-nickel austenitic stainless steel (designed for temperatures below -196℃), additional requirements for their fabrication, inspection and testing, and acceptance shall be specified through consultation among the parties involved in the construction and shall be stipulated in the design documents by the design unit.
4.2 Basis for the fabrication, inspection and testing, and acceptance of pressure vessels
The fabrication, inspection and testing, and acceptance of pressure vessels shall comply with the following requirements in addition to those in this document and the design documents:
a) The fabrication, inspection and testing, and acceptance of heat exchangers, spherical tanks, vertical vessels supported by skirt, and horizontal vessels on saddle supports shall comply with GB/T 151, GB/T 12337, NB/T 47041, and NB/T 47042, respectively.
b) The fabrication, inspection and testing, and acceptance of the cladding, lining or surfacing layers of nickel and nickel alloy clad plates shall also comply with JB/T 4756.
4.3 Raw materials and parts and components (including self-made, outsourced and purchased parts and components)
4.3.1 Raw materials
4.3.1.1 Plates, tubes, forgings, bars and clad plates shall be subject to the following requirements.
a) Plates, tubes, forgings, and bars shall comply with the relevant requirements of GB/T 4732.2 and JB/T 4756. Material suppliers shall provide the material manufacturer’s heat treatment process parameters for the materials as delivered.
b) Clad plates shall comply with NB/T 47002.1 and NB/T 47002.2, respectively. When heat exchange tubes are subject to axial compressive stress, if clad plates are used to manufacture tube sheets, requirements on bonding strength of the clad plates shall be specified and bonding strength tests shall be conducted in accordance with GB/T 6396.
c) For the pressure vessels within the scope of application of this document, if all pressure components are made of nickel and nickel alloy, the allowable stress shall be selected in accordance with the relevant provisions of JB/T 4756.
4.3.1.2 Welding materials shall comply with NB/T 47018 (all parts) as well as GB/T 4732.2.
4.3.2 Parts and components (including self-made, outsourced and purchased parts and components)
4.3.2.1 In addition to meeting the requirements of GB/T 25198, the heads shall also meet the following requirements.
a) Hard markings shall not be adopted for formed heads.
b) Cold-formed chromium-nickel austenitic stainless steel heads shall be tested for ferrite content using a ferrite tester along two mutually perpendicular bus bars, by referring to GB/T 1954. For ellipsoidal heads and dished heads, the test points shall include at least the apex, four points at the small-radius corner, and four points near the port on the straight edge. For conical heads, the test points shall include at least four points near the ports at the large and small ends, respectively, and four points in the middle. For hemispherical heads, the test points shall include at least the apex, four points near the port, and four points between the apex and the port. The measured ferrite content shall not be greater than 15%, and the pressure vessel manufacturer shall re-test each formed head one by one. For heads formed after plate splicing, the test parts shall include the weld seams.
c) When materials are supplied and used in the same heat treatment state, if the head forming changes the supply heat treatment state of the materials, the head manufacturer shall carry out the restorative heat treatment.
d) For heads assembled after being formed in flaps, if the assembly is not completed by the head manufacturer, the head manufacturer shall pre-assemble the heads. The inspection items and results of the pre-assembled heads shall comply with the relevant standards or technical documents for ordering.
e) For heads fabricated by means of processing with supplied materials, the performance of materials and the performance requirements for formed heads shall be agreed upon by the supplier and the purchaser, the performance of the supplied materials shall be guaranteed by the purchaser, and the performance of the formed head shall be guaranteed by the supplier.
4.3.2.2 The flanges of a pressure vessel and their components shall comply with NB/T 47020 to NB/T 47027 and the design documents.
4.3.2.3 The pipe flanges of a pressure vessel and their components shall comply with HG/T 20592 to HG/T 20635 and the design documents, and special grade fasteners shall be used.
4.3.2.4 The expansion joints for pressure vessel shall comply with GB/T 16749 and the design documents. Cold-formed chromium-nickel austenitic stainless steel expansion joints shall be tested for ferrite content using a ferrite tester along four bus bars spaced 90° apart by referring to GB/T 1954. The test points shall include at least the wave crest, wave trough, and the part between the crest and trough. The measured ferrite content shall not be greater than 15%, and the pressure vessel manufacturer shall re-test each formed expansion joint one by one. For expansion joints formed after plate splicing, the test parts shall include the weld seams.
4.3.2.5 The reinforcing pads shall comply with NB/T 11025 and the design documents.
4.3.2.6 Suppliers of purchased finished parts and components shall provide the pressure vessel manufacturer with complete and authentic product quality certificates. When requested by the pressure vessel manufacturer, the suppliers shall provide the thickness of the steel used in the finished parts and components.
Contents of GB/T 4732.6-2024
Contents
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Material re-inspection, cutting and mark transplantation
6 Cold/thermal forming and assembly
7 Welding
8 Heat treatment
9 Test pieces and specimens
10 Non-destructive testing
11 Pressure test and leakage test
12 Hot gas cycle test
13 Pressure vessel factory requirements
Annex A (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of forged-welded pressure vessels
Annex B (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of shrink fit pressure vessels
Annex C (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of multilayer-wrapped pressure vessels
Annex D (Normative) Additional requirements for the fabrication, inspection and testing, and acceptance of flat steel ribbon wound pressure vessels
