Within the overall objective of re-purposing the NTS for hydrogen, there is current uncertainty as to the risk posed by degradation of polymeric (including elastomeric) materials when exposed to high-pressure hydrogen environments.
To investigate this risk, it is proposed to conduct a project to compile a full list of all polymeric materials on the NTS alongside the expected hydrogen operating conditions for these components. The functional and material property requirements of the polymers can then be determined. In parallel, a review of the susceptibility of such polymeric materials to hydrogen damage will be undertaken. This work will inform the definition of a test programme to validate the performance of the polymeric materials in a hydrogen transmission system, where appropriate.
Benefits
Gain increased knowledge of the impacts of hydrogen on NTS polymer materials and determine test programme to validate/approve polymeric materials.
Learnings
Outcomes
Work Package 1 – Determination of Materials in the NTS
A list of the current polymeric materials on the National Transmission System (NTS) was generated from the available data sources. It was found that there were approximated 23 different polymeric materials on the NTS with the most common material being nitrile followed by PTFE, synthetic rubber, nylon, neoprene and rubber.
Work Package 2 – Impact of hydrogen on polymeric NTS materials
During the literature survey on the impact of high-pressure hydrogen on polymeric materials it was identified that there is currently limited test data available at NTS specific pressures and temperatures across all the polymer grades identified in work package 1. Nevertheless, the limited data available suggested that there would be minimal expected impact of hydrogen over and above natural gas for the majority of the polymers assessed. One polymeric material, EPDM, might not be suitable in hydrogen-methane blends, but further work would be needed to verify this.
Work Package 3 – Establish expected service conditions
In the majority of cases, the expected service conditions of the polymers were found to be aligned to typical mainline pipe conditions. These would be typically a temperature range of -20 to +50 °C with gas pressures up to 94 bar. Some polymeric materials but also be subject to pressure cycling and or rapid depressurization (for example PIG trap closures).
Work Package 4 – Establish functional, material property and maintenance requirements
The following failure mechanisms were identified in relation to polymeric materials in high-pressure hydrogen: Rapid gas decompression (RGD); volume swell; chemical degradation; ageing; fatigue; compression set; abrasion/wear; and permeation. Of these, rapid gas decompression, volume swell, compression set and fatigue were identified as highest risk in terms of available data and expected performance in hydrogen.
Work Package 5 – Test and Validation Plan Proposal
Recommendations for validation and approval of polymeric materials were divided into new build applications and repurposing. For new build applications, a set of acceptance criteria for thermoplastics and elastomeric materials were defined and is expected that these would be requested as evidence of the hydrogen-readiness of the polymeric components used within assets such as valves, isolation joints, regulators etc. For the repurposing of existing assets for use in hydrogen it was recommended that asset-level testing (e.g leak tightness testing) be conducted to determine the functionality of the polymeric materials. If this asset-level testing did not meet the requirements, then further materials level testing could be carried out in the laboratory to determine whether and how the material was responsible for the asset-level failure. Such materials testing could be carried out alongside virgin (e.g. non-ex-service) materials to determine whether prior natural gas service contributes to polymeric material failure.
Work Package 6 – Standards & Reporting
Two technical reports were produced during the project; IMPACT OF HYDROGEN ON NTS POLYMER / ELASTOMER MATERIALS – Impact of Hydrogen on NTS Polymers (Report No.: 1699255 Rev. 3.0) covered WP1-3 and IMPACT OF HYDROGEN ON NTS POLYMER / ELASTOMER MATERIALS – WP 4 – Functional, Materials Properties & Maintenance WP5 – Test & Validation Proposal (Report No.: 1819089, Rev. 3.0) covered WP4-5.
The project value tracking is listed below:
· Maturity
o TRL 0-1. Desktop research to explore and define next steps.
· Innovation Opportunity
o >50% or multiple asset classes. Gas-facing polymers present in multiple asserts such as valves, actuators, regulators, pig traps, isolation joints and filters.
· Deployment Costs
o £0.00. No direct deployment costs as this is a research project. However, costs might need to be incurred to ensure hydrogen readiness of assets with respect polymeric/elastomeric component performance.
· Innovation Cost
o £ 61,866.67. Cost of innovation project (Phase 1).
· Financial Saving
o £ 0.00. No direct financial savings as this is a research project. However, confirmation of polymer/elastomer performance might enable life extension or avoidance of replacement of assets.
· Safety
o 0%. No direct safety improvement as this is a research project. However, confirmation of polymer/elastomer performance might inform decisions on asset condition monitoring in hydrogen.
· Environment
o 0.0 tonnes CO2e. No direct environmental benefits as this is a research project. However, confirmation of polymer/elastomer performance might enable life extension or avoidance of replacement of assets with associated avoidance of environmental harm.
· Compliance
o Ensures compliance. Work supports transition to hydrogen.
· Skills & Competencies
o Individuals. Work will augment knowledge of individuals involved in project.
· Future Proof
o Supports business strategy. Work could eventually inform hydrogen repurposing and future new build strategies (e.g. procurement requirements).
Lessons Learnt
The project structure enabled clear identification of the project requirements and the outputs of a database summarising the polymeric materials, their functional requirements and suitability for hydrogen service plus the test programme recommendations were as per plan. It is recommended that a similar approach is followed for other materials such as oils and greases.
Capture of data on assets within National Gas was found to be very difficult and there are some potentially significant gaps in the data which would need to be addressed in follow-on projects. For similar projects it would be recommended to allocate more resource to capturing the material data and comparing this to existing records such as asset lists to enable quantification of the data gaps.
