f NTS Materials Testing to Enable Hydrogen Injection in High Pressure Pipelines, Technical Summary Report

National Gas is aiming to demonstrate the potential use of hydrogen in high pressure transmission pipelines and associated equipment through the FutureGrid NIC programme. This involves construction and operation of a realistic high pressure transmission system using decommissioned National Gas assets. The linepipe for the facility will be X-52 and X-65 grade steels. A key parameter for the facility is to operate at the current NTS pressure tier.
The most applicable pipeline design code is ASME B31.12, used in the USA and currently used by UK HSE for evaluating hydrogen pipeline designs. Hydrogen supplements to the IGEM/TD/1 and IGEM/TD/13 codes also refer to this standard. The code has prescriptive design methods for allowable pressures which would reduce the FutureGrid maximum allowable design pressure (MAOP) to below current NTS pressure. The code does, however, allow less prescriptive methods if the linepipe has been tested for fracture toughness and fatigue performance in hydrogen using a protocol as defined by ASME VIII Section 3 Article KD-10. This would potentially allow a higher MAOP for FutureGrid1.
A materials test programme has therefore been established to evaluate the fracture toughness and fatigue properties of the actual linepipe used for the FutureGrid facility. The X-52 and X-65 linepipe being used to construct the facility has been tested in hydrogen, including realistic seam welds and girth welds. This data has been used to confirm an appropriate maximum operating pressure for the FutureGrid test facility, by carrying out fracture mechanics analyses in accordance with the above standards.
The materials test programme also includes a task to generate similar fracture toughness and fatigue data for a wider range of materials within the NTS, as described in Table 1 below. This report provides test results for all of these materials, along with analysis and interpretation of the results. It therefore satisfies the reporting requirements associated with a number of milestones as follows:
• Task 7 “Update of Data Analysis/Design using additional X60 results”
• Task 19 “Completion of Task 3 Reporting”
• Task 20 “Completion of Task 4 & Associated Reporting”
At present, the report does not include details of tests carried out within Task 17 “Sub-critical crack growth testing” as some of those tests are still ongoing. The report will be updated to include these data when the tests are complete.
This report was submitted to HSE for their assessment of the safety evidence for 100% hydrogen heating, which can be found at Hydrogen heating: HSE assessment of the safety evidence - GOV.UK.
Queries should be directed to DESNZ: https://www.gov.uk/guidance/contact-desnz.