Pipeline design codes and standards for use in UK CO2 Storage and Sequestration projects

Background

HSE's approach to dealing with carbon capture and storage (CCS) projects is currently being developed to ensure we are able to deal effectively with any new projects. As part of this process the need has been identified to co-ordinate work on understanding risks with CCS across HSE and other Government departments in key areas such as:

Determine whether certain physical states of CO2 (eg high pressure/supercritical) combined with quantity considerations should be classified as "dangerous fluids" for the purpose of the Pipelines Safety Regulations 1996 and/or "dangerous substances" for the purpose of COMAH 1999;
Propose any necessary legislative changes and gain policy support to take these forward;
Identify technical and other issues which need to be progressed;
Consider land use planning arrangements;
Identify research needs;
Inform and contribute to OGD work streams and the Seveso Community of Competent Authorities (CCA).

CO2 Pipelines

The incentives to reduce carbon emissions have led to a number of recent proposals for CO2 storage and sequestration schemes in the UK. Many of these schemes will involve the transportation of CO2 by pipeline, either through the construction of major new pipeline systems or by the modification of existing pipeline infrastructure. Current UK experience in CO2 pipelines is limited, and only some pipeline design codes appear to capture CO2 as a relevant fluid within their scope of application. This note seeks to highlight relevant pipeline design codes and standards suitable for use in the design of pipeline systems for the transportation of CO2 in the UK.

HSE Guidance on ALARP in Design and Good Practice

HSE attaches particular importance to reducing risks to people as a result of appropriate consideration of health & safety in design and the use of good practice. During the design stage, which covers concept selection through to detailed design specification, there is maximum potential for reducing risks by the application of the principles of inherently safer design. The use of good practice at the design stage is essential in demonstrating achievement of ALARP and in judging compliance HSE expects duty holders to apply relevant good practice as a minimum.

However, depending on the level of risk and complexity of the situation, it is possible that meeting good practice alone may not be sufficient to comply with the law. For example, in high hazard situations, where the circumstances are not fully within the scope of the good practice, then additional measures may be required to reduce risks ALARP. Furthermore, where the potential consequences are high, HSE will take a precautionary approach by giving more weight to the use of sound engineering and operational practice than to arguments about the probability of failure. Further guidance in these areas can be found on the HSE web site - the references are shown at the end of this document.

It should be noted that current pipeline codes did not anticipate the bulk transportation of CO2 in the quantities likely to be seen in CCS projects. Ongoing work suggests that the hazards involved with the bulk transport of CO2 are similar to the hazards transporting natural gas,

Current Guidance from the Pipelines Safety Regulations

Regulation 5 of the Pipelines Safety Regulations (PSR) 1996 requires that the design of a pipeline, or any modification to it, takes into account the operating regime of the pipeline, the conditions under which the fluid is to be conveyed as well as the environment to which the pipeline will be subjected. In particular relation to the reuse of existing pipelines, any change to the fluid conveyed will need a reassessment of the original pipeline design to ensure that the pipeline is capable of conveying the fluid safely.

European Standards implemented in the UK as British Normative Standards (BS EN series) and supported by published documents (such as the British Standards PD series) provide a sound basis for the design of pipelines. Other national or international codes (eg, a relevant standard or code of practice of a national standards body or equivalent body of any member state of the European Union) are likely to be acceptable provided the proposed standard, code of practice, technical specification or procedure provides equivalent levels of safety.

Relevant European Standards

PD 8010 Parts 1 and 2
BS EN 14161 – Petroleum and Natural Gas Industries, Pipeline Transportation Systems
Institute of Petroleum Pipeline Code IP6
DNV OS-F101 Submarine Pipeline Systems 2000

Discussion on Key Areas of Compliance

IP6, BS EN 14161, BS PD 8010 and DNV OS-F101 are all applicable to pipelines transporting CO2 with the latter three categorising it as a non flammable, non toxic fluid which is gaseous at ambient temperature and pressure. IP6 also treats it as a gas. None of these standards specifically address CO2 transported at a pressure above its critical point as a dense phase fluid. This omission is not an oversight by the standards organisations but simply a reflection of the fact that to date CO2 has not been transported in this phase and hence there has been no driver to address the issues associated with such an activity.

IP6 is still in existence but is not widely employed for new pipelines, although it contains useful guidance on operational issues. BS 8010 has been withdrawn and has been replaced by BS PD 8010 Parts 1 and 2. The European Standard BS EN 14161 - Petroleum and Natural Gas Industries, Pipeline Transportation Systems has also been introduced although the HSE recommends that any pipelines designed to BS EN 14161 should be supported by good industry practice as presented in BS PD 8010 Parts 1 and 2. DNV OS-F101 is specifically an offshore standard and its scope is limited to Submarine Pipeline Systems.

Issues in relation to US Pipeline Codes

Enhanced oil recovery using CO2 injection has been common practice for many years in the USA and hence there are numerous high pressure CO2 pipelines in operation. The US Federal Code of Regulations, Title 49, Volume 3, Part 195 - Transportation of Hazardous Liquids by Pipeline and the associated ASME standard B31.4 and B31.8 are the main codes which address the transportation of liquids and gases by pipeline respectively.

The US Code of Regulations only applies to pipelines transporting CO2 in the supercritical phase. The Code therefore may only be relevant to pipelines conveying supercritical CO2. There appear to be no US Regulations addressing the transport of CO2 in the gaseous or liquid phase. Furthermore the standard B31.8 specifically excludes pipelines carrying CO2 (in any phase), and whilst the standard B31.4 does not specifically exclude pipelines transporting CO2, it does not include CO2 within the list of fluids to which the code is intended to apply. It may therefore be concluded that there may be limited technical benefit in adopting the US Code or standards in either their entirety or in part.

References

Issue Date: 19th February 2008
Gas and Pipelines Unit