Forschungsbericht G 202006 01/2023 -pdf-file-

DVGW Project SyWeSt H2: Investigation of Steel Materials for Gas Pipelines and Plants for Assesment of their Suitability with Hyrogen

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  • 1st edition 2023
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For hydrogen transmission within the German gas grid, it is imperative to obtain a clearly defined assessment of steel components for hydrogen suitability and relevant implementation in the DVGW Codes of Practice. Within this context, DVGW Code of Practice G 409 (for the conversion of pipelines to hydrogen transmission) and DVGW Code of Practice G 463  (for the construction of new pipelines), for example, have been specifically aligned to hydrogen as a transmission medium. Both these codes of practice may require a fracture-mechanical assessment of pipelines and pipeline components, with fracture-mechanical parameters beingrequired as input variables.

So far, it was only in ASME B 31.12 [3] that these parameters were specified in an international code of practice. They specifically involve minimum fracture toughness (KIc) and the description of crack toughness (da/dN) with hydrogen as a medium. However, the parameters specified in ASME B 31.12 were based on investigations on US materials which are verysimilar, but not identical, to the materials used in Germany and elsewhere in Europe. Furthermore, the conversion of existing older natural gas pipelines (comprising older materials) is of very considerable interest particularly for the scope of application of the DVGW Code of Practice, although a direct transferability of the US investigations was considered to be problematic.

Hence, within the context of the DVGW’s extensive SyWeSt H2 research project, fracturemechanical investigations were performed specifically for the pipeline steel grades used in Germany (and, in some cases, elsewhere in Europe) with hydrogen as a medium. The objective of this project was to compare the established fracture-mechanical parameters with the results on which ASME B 31.12 is based for the purpose of validating their application to steel grades used in Germany and, where applicable, drawing up a modified correlation for crack growth.

1 Terms of Reference

2 Basic Procedure for Performance of Fracture-Mechanical Tests

2.1 Test Set-up for Performance of Fracture-Mechanical Tests in Hydrogen Atmosphere

2.2 Cyclical Tests: Testing and Evaluation as per ASME E647 [5]

2.3 Static Fracture-Mechanical Testing: Testing and Evaluation as per ASTM E1820

3 Investigated Materials

3.1 L290 NE

3.2 5L Grade A

3.3 St35

3.4 15k (St35)

3.5 X42

3.6 RR St43.7

3.7 P355 NH/NL2

3.8 L360NE

3.9 L360NB (Batch 2)

3.10 X46 / StE320.7

3.11 StE360.7

3.12 StE480.7 TM

3.13 L360 NB

3.14 14HGS

3.15 WSTE 420

3.16 St53.7

3.17 X56.7

3.18 St60.7

3.19 P460 NH

3.20 X70

3.21 L485

3.22 L485 ME

3.23 L485 (Batch 2)

3.24 GRS550/X80

3.25 L415

3.26 P355 NL1

3.27 GJS400

3.28 P460 QL1

3.29 C22.3

3.30 GS C25 N

3.31 TStE 355N

4 Results of Crack Growth Measurements

4.1 Crack Growth at pH2 = 100 bar and R=0.5

4.2 Crack Growth Law Depending on Hydrogen Pressure pH2

4.3 Additional Consideration of Mean Stress (R Value)

5 Selected Results for Fracture Toughness

5.1 Results for pH2 = 100 bar

5.2 Results for pH2 < 100 bar

6 Conclusions and Outlook

7 Literature

8 List of Abbreviations

9 List of Symbols

10 List of Figures

11 List of Tables