Specified for Hydrogen: Why Double Containment and H2-Ready PE 100-RC Belong in Every Serious Design

The UK's hydrogen buildout is accelerating. For specifying engineers, the pipe material decisions made at concept stage will define safety, regulatory compliance and whole-life cost for decades. Here is why AGRU Poly-Flo double containment and AGRULINE PE 100-RC are the technically rigorous choices.

The policy signal is unambiguous. The UK government has committed over £500 million to develop the country's first regional hydrogen transport and storage network (DESNZ, July 2025), and 27 electrolytic hydrogen projects representing approximately 765 MW of potential production capacity have been shortlisted under the second Hydrogen Allocation Round (DESNZ, April 2025). HAR3 and HAR4 are planned for 2026 and 2028 respectively. The pipeline of projects is real, it is funded, and it is moving from feasibility into detailed design. For consulting engineers, that means hydrogen piping specifications are being written right now.

The challenge is not enthusiasm: it is rigour. Hydrogen is the smallest molecule in common use. It permeates materials that would safely contain natural gas, it is invisible, odourless and highly flammable, and its behaviour under pressure and at the fitting joints in a distribution network demands a material selection approach that cannot be improvised from existing gas or chemical process precedent.

Material compatibility is the first question every hydrogen piping specification must answer. The good news for engineers specifying thermoplastic systems is clear. AGRU's AGRULINE PE 100-RC product range has been assessed by the DBI Gastechnologisches Institut and certified for hydrogen compatibility up to 100% hydrogen by volume. The range meets the relevant standards CEN EN 1555-1-3 and carries the H2Ready quality mark to DBI GTI 109.

From the pressure reduction station, hydrogen can be distributed either as a hydrogen-natural gas mixture or at 100% at pressures up to ten bar through the AGRULINE PE 100-RC system. That is a tested, certified, documented position: precisely the kind of evidence a specifying engineer needs before committing a material to a safety-critical specification.

PE 100-RC brings further advantages over standard PE 100 that matter specifically in hydrogen infrastructure. Its significantly enhanced resistance to slow crack growth improves safety and extends design service life. The material is rated for use down to -40°C, which is relevant to both outdoor installations and some hydrogen storage environments. It can be installed without a sand bed, reducing civil works cost and programme risk on a class of project where groundworks are rarely straightforward.

Containment: moving beyond single-wall thinking. For hydrogen production plant, electrolysis facilities, and any run of pipe traversing a groundwater protection area or a high-hazard process environment, single-wall pipe is not sufficient. The HSE is clear that secondary containment is used where a substance is particularly hazardous and alternative bunding is not available, and that monitoring of the annulus is used to detect initial failure. That principle maps directly onto the role of AGRU Poly-Flo.

Poly-Flo is AGRU's compact double containment piping system. The media pipe and the outer protective pipe are extruded simultaneously in a single production step, which means dimensional accuracy is controlled at manufacture rather than on site. The system is available in PE 100-RC and PPR materials in dimensions from OD 50/32 mm to 225/160 mm, with pressure ratings selectable between SDR 17/11 and SDR 33/17. The PE 100-RC variant's crack-resistant material allows installation without a sand bed. The outer and inner tubes are permanently joined with a single weld. There are no loose components to misalign, no field-fabricated annular supports to fail, and no dimensional mismatch between pipe and fittings because the complete system, pipes and fittings alike, comes from a single production facility.

For the specifying engineer, that matters in two ways. First, it simplifies the specification: one system, one manufacturer, one set of welding procedures. Second, it simplifies the quality audit trail. In a safety-critical hydrogen application, demonstrating that the containment system is dimensionally consistent and manufactured under a single quality regime is a significant risk reduction at design review and at HSE scrutiny.

The regulatory landscape is still developing, and that is an argument for over-engineering containment now. The Gas Safety Management Regulations 1996 require transporters of hydrogen to submit a safety case to the HSE identifying hazards and how they are controlled. The Pipeline Safety Regulations 1996 set out requirements for design, construction, installation, operation, maintenance and decommissioning. Double containment, with annulus monitoring, is the most direct and auditable way to demonstrate that a release from the primary pipe will be detected and contained before it reaches the environment or ignition sources.

Whole-life cost: the case that closes the specification. Thermoplastic systems do not corrode. AGRU references intact PE pipelines still in operation 50 years after installation. For a hydrogen network designed to operate into the second half of this century, that longevity is not a marketing claim: it is a whole-life cost argument. Maintenance inspection costs are lower. Replacement cycles are longer. The recyclability of thermoplastics supports the sustainability reporting obligations that are increasingly part of project governance, particularly in infrastructure funded through government business models.

The electrolysis process itself creates additional piping duties beyond hydrogen transport. In PEM electrolysis, ultrapure water at 60 to 80°C and 6 to 10 bar is required. In alkaline electrolysis, potassium hydroxide is transported from production to the electrolysis plant. These media require chemical-resistant systems: polypropylene and PVDF for aggressive process streams, and AGRU's PURAD high-purity range where ultrapure water quality must be maintained. The hydrogen value chain, from feedwater to gas distribution, is a thermoplastics application from end to end.

IPS Flow Systems supplies the full AGRU range into the UK and Ireland, including AGRULINE PE 100-RC pipe, fittings and electrofusion components, and Poly-Flo double containment systems. With more than 30 years in the industry, large UK stocks, next day delivery and direct access to technical support, IPS is positioned to support hydrogen projects from early specification through to construction delivery. Specifying engineers can access datasheets, welding procedure guidance and sector-specific technical support by contacting the IPS team directly.

References

1. Department for Energy Security and Net Zero (DESNZ), Hydrogen Update to the Market (2025): The UK government committed over £500 million for the development of the UK's first regional hydrogen transport and storage network. https://assets.publishing.service.gov.uk/media/6880b2139fab8e2e86160efe/hydrogen-update-to-the-market-2025.pdf
2. Department for Energy Security and Net Zero (DESNZ), HAR2 shortlist announcement (2025): 27 electrolytic hydrogen projects representing approximately 765 MW of production capacity were shortlisted under HAR2. https://www.energyvoice.com/renewables-energy-transition/hydrogen/uk-hydrogen/569076/uk-green-hydrogen-projects-secure-government-backing-allocation-round-har2-sarah-jones/
3. CMS Law, UK Hydrogen Sector Updates: Update to Market (2025): HAR3 and HAR4 are planned for 2026 and 2028 respectively. https://cms-lawnow.com/en/ealerts/2025/08/uk-hydrogen-sector-updates-update-to-market-and-blending-into-the-gb-gas-transmission-network
4. AGRU, AGRULINE product information and hydrogen page (2024): AGRU's AGRULINE PE 100-RC product range has been assessed by the DBI Gastechnologisches Institut and certified for hydrogen compatibility up to 100% hydrogen by volume, meeting CEN EN 1555-1-3 and carrying the H2Ready quality mark to DBI GTI 109. https://www.agru.at/en/markets/emerging-markets/hydrogen
5. AGRU Croatia, Hydrogen – AGRU (2024): Hydrogen can be distributed either as a hydrogen-natural gas mixture or at 100% at pressures up to ten bar through the AGRULINE PE 100-RC system. https://agru.hr/tvrtka/inovacije/hydrogen-agru/
6. AGRU, Poly-Flo double containment piping system product page (2024): AGRU Poly-Flo is available in PE 100-RC and PPR materials in dimensions from OD 50/32 mm to 225/160 mm, with pressure ratings between SDR 17/11 and SDR 33/17. https://www.agru.at/en/news/innovations/innovations-and-new-products/poly-flo-the-double-containment-piping-system
7. AGRU Australia, Poly-Flo: Ready-to-Use Double Containment Piping System (2025): The inner media pipe and outer containment pipe in Poly-Flo are extruded simultaneously in a single production step; the outer and inner tubes are permanently joined with a single weld. https://www.agru.com.au/poly-flo-the-ready-to-use-double-containment-piping-system/
8. HSE, Secondary Containment technical measures guidance (2024): The HSE states that secondary containment (outer shell or secondary pipe) is used where a substance is particularly hazardous and no alternative means such as bunding is available, and that monitoring of the annulus is used to detect the initial failure. https://www.hse.gov.uk/comah/sragtech/techmeascontain.htm
9. Pinsent Masons, UK hydrogen safety law: the developing framework (2025): The Gas Safety (Management) Regulations 1996 require any transporters of gas, including hydrogen, to submit a safety case to the HSE identifying hazards and risks and how they are controlled. https://www.pinsentmasons.com/out-law/guides/uk-hydrogen-safety-law
10. Pinsent Masons, UK hydrogen safety law: the developing framework (2025): The Pipeline Safety Regulations 1996 set out requirements for pipeline design, construction, installation, operation, maintenance and decommissioning. https://www.pinsentmasons.com/out-law/guides/uk-hydrogen-safety-law
11. AGRU, AGRULINE product brochure (2024): AGRU references intact PE pipelines still in operation 50 years after installation. https://www.agru.at/fileadmin/user_upload/produkte/agruline/downloads/Prospekte/EN/AGRU_AGRULINE_EN.pdf
12. AGRU, Overview of AGRU product innovations (2024): In PEM electrolysis, seawater is transported via AGRU XXL pipelines to desalination plants, treated with AGRUCHEM, and purified in PURAD piping systems before the purified water is converted into H2. https://www.agru.at/en/news/innovations/overview-of-agru-product-innovations