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ISO 27955:2025 — CO2 Pipeline Transportation Systems: Design, Operation and Maintenance
Standardized Requirements for CO2 Pipeline Infrastructure
1. Scope of ISO 27955:2025
ISO 27955:2025 establishes comprehensive requirements for the design, construction, operation, and maintenance of pipeline transportation systems for CO2 streams from capture facilities to storage or utilization sites. As carbon capture and storage (CCS) deployment accelerates globally, standardized pipeline transportation infrastructure becomes essential for connecting emission sources with storage reservoirs. This standard addresses material selection, corrosion management, hydrate prevention, fracture propagation control, and leak detection specifically for dense-phase and supercritical CO2 pipeline service.
The standard covers pipeline systems operating at pressures typically between 8 and 20 MPa, maintaining CO2 in a dense-phase or supercritical state to ensure single-phase flow and prevent two-phase flow instabilities. Unlike natural gas pipelines, CO2 pipelines present unique challenges including high compressibility near the critical point, Joule-Thomson cooling during depressurization, and high susceptibility to ductile fracture propagation over long distances.
CO2 pipeline design differs fundamentally from natural gas pipeline design. The high compressibility of CO2 near its critical point (31 C, 7.38 MPa) creates unique flow dynamics that require specialized simulation tools and operating procedures.
2. Material Selection and Corrosion Control
Material selection is critical for CO2 pipeline integrity. The standard provides a detailed material selection matrix based on CO2 stream composition, operating pressure, temperature, and water content. Carbon steel grades (API 5L X52 to X70) are typically suitable for dehydrated CO2 service with less than 50 ppmv water. For wet CO2 service or streams containing high concentrations of impurities (SOx, NOx, O2), corrosion-resistant alloys or internal coatings may be required.
| Water Content (ppmv) | Material Recommendation | Corrosion Allowance (mm) | Additional Requirements |
|---|---|---|---|
| Less than 30 | Carbon steel (X52-X70) | 1.5 | Standard dehydration |
| 30-200 | Carbon steel + inhibitor | 3.0 | Chemical injection system |
| 200-500 | 316L SS or clad pipe | 0 | Internal coating recommended |
| Greater than 500 | Duplex SS or lined pipe | 0 | Specialized corrosion assessment required |
Water content is the single most important quality parameter for CO2 pipeline transport. Free water phases enable carbonic acid formation, leading to corrosion rates exceeding 5 mm/year in carbon steel pipelines. Continuous online moisture monitoring at pipeline inlet is essential.
3. Fracture Propagation Control
CO2 pipelines have a well-documented tendency for long-running ductile fractures due to the high compressibility and rapid decompression behavior of dense-phase CO2. ISO 27955 specifies requirements for fracture arrest design using the two-curve method or Battelle-type analysis. The standard requires that the pipeline material’s Charpy impact energy exceed the minimum required fracture arrest toughness calculated for the specific CO2 composition, operating conditions, and pipe geometry.
For pipelines transporting CO2 with impurities (hydrogen, nitrogen, oxygen, argon), the decompression wave speed is significantly affected. Even small amounts of hydrogen (above 2 mol%) can reduce the decompression wave speed, increasing fracture propagation risk. The standard provides correction factors for impurity effects on decompression behavior based on computational fluid dynamics simulations validated against full-scale burst test data.
Do not use natural gas pipeline fracture models for CO2 pipelines. The decompression characteristics of dense-phase CO2 are fundamentally different from natural gas. Using inappropriate models can lead to fracture arrest failure and catastrophic pipeline rupture over distances exceeding 1 kilometer.
4. Operational Safety and Leak Detection
The standard specifies operational safety requirements including pressure control, overpressure protection, emergency shutdown systems, and leak detection methodologies. For CO2 pipelines, leak detection must consider the unique behavior of CO2 releases: dense-phase CO2 exiting a pipeline forms a complex multiphase jet with solid CO2 particles, creating different detection challenges compared to natural gas leaks. Recommended technologies include real-time mass balance, acoustic detection, distributed temperature sensing, and soil gas monitoring.
Modern CO2 pipelines achieve leak detection sensitivity of 1-2% of flow rate using combined mass balance and acoustic monitoring systems. This is critical for early detection and minimizing environmental releases.
5. Frequently Asked Questions
Q: What is the typical operating pressure range for CO2 pipelines?
Dense-phase CO2 pipelines typically operate at 8-20 MPa depending on source pressure, pipeline length, and terrain. Supercritical operation requires maintaining temperature above 31 C.
Dense-phase CO2 pipelines typically operate at 8-20 MPa depending on source pressure, pipeline length, and terrain. Supercritical operation requires maintaining temperature above 31 C.
Q: Can existing natural gas pipelines be converted to CO2 service?
Yes, but conversion requires detailed assessment of fracture toughness, valve compatibility, and leak detection systems. Only about 30-40% of existing pipeline inventory is suitable for conversion without major upgrades.
Yes, but conversion requires detailed assessment of fracture toughness, valve compatibility, and leak detection systems. Only about 30-40% of existing pipeline inventory is suitable for conversion without major upgrades.
Q: What impurities in the CO2 stream cause the most concern?
Water (causing carbonic acid corrosion), hydrogen (affecting decompression behavior), and oxygen (increasing corrosion potential). The standard defines maximum impurity limits for pipeline transport.
Water (causing carbonic acid corrosion), hydrogen (affecting decompression behavior), and oxygen (increasing corrosion potential). The standard defines maximum impurity limits for pipeline transport.
Q: How are CO2 pipeline leaks detected?
Through a combination of mass balance methods (1-2% detection threshold), acoustic monitoring, distributed temperature sensing along the pipeline, and regular aerial or drone-based infrared surveys.
Through a combination of mass balance methods (1-2% detection threshold), acoustic monitoring, distributed temperature sensing along the pipeline, and regular aerial or drone-based infrared surveys.
