CO₂SafeArrest (‘Improving safety and efficiency of CO₂ pipelines by developing and validating predictive models for CO₂ pipeline design’)

Background and project purpose
Safe and efficient transport of carbon dioxide (CO₂) from where it is captured to a storage site is an important stage in the CCS process and CO₂ transport by pipelines is a commonly used method. The costs of pipelines in CCS projects are significant, where material costs are a major part. Ensuring safe arrest of running ductile fracture is essential in any pipeline but current assessment models give highly uncertain results for CO₂. Non-optimal and inefficient pipeline design may be the results. In the absence of accurate fracture models, CO₂ pipelines must be either designed and constructed excessively conservative or subjected to full-scale propagating tests.

In order to address this challenge DNV and Energy Pipelines CRC (EPCRC) have established a joint industry project (JIP) funded by the Norwegian CLIMIT and the Commonwealth Government of Australia. The project is seeking to advance optimal pipeline design through updated simulation models and full-scale fracture tests and validating predictive models for CO₂ pipeline design in order to reduce the future cost of CO₂ pipelines while ensuring the required safety level and quality.

Objective
• Validate fracture arrest models and design requirements
o Reduce the need for project specific full-scale fracture arrest tests.
O Remove excessive conservatism (sufficient wall thickness and material properties identified).
O Reduce costs for new CO₂ pipeline projects.

• Validate dispersion models
o Give valuable input to definition of safety class and selection of pipeline safety factors.
O Improve overall safety level for surrounding communities.

What has the project done in terms of activities?
The project has undertaken two full scale fracture arrest tests for validation of the numerical models at the Spadeadam full scale test site during 2017/2018 followed by in-house material testing, analysis and assessments.
Provided input to guidelines for high pressure CO₂ pipeline design that can be fed into national and international standards such as DNV-GL-ST-F101, DNVGL-RP-F104, AS2885, relevant ISO standards.

What has the project achieved? Did the project achieve its objective?
The project has made the results available through conferences, seminars, workshops with relevant industry players as well as updating DNVGL-RP-F104 ‘Design and Operation of Carbon Dioxide pipelines’. New revision of DNVGL-RP-F104 was published on 20.02.2021.

Future plans?
The project has shown that there are still uncertainties associated with the model for running ductile fractures for pipelines with low fracture toughness that are characteristic of pipes of older data, i.e. for existing pipelines as per today transports natural gas but which is considered re-qualified to be able to transport CO₂ in the future. There is a desire to have further collaboration with the industry to take a closer look at this type of pipe. Furthermore, the update of DNVGL-RP-F104 has also led to other issues related to the current edition that are relevant for CO₂-carrying pipes, and which were not a topic for the CO₂SafeArrest project. This applies to i.e. CO₂ specifications and various impurity elements effect on mechanical properties, corrosion etc. Plans will be made for what is to be covered by this in the next update of DNVGL-RP-F104.