Duplex Stainless Steel Coil Tube for High-H₂S Sour Gas Gathering Pipelines
Product Overview
This high-performance stainless steel coil tube is purpose-engineered for the gathering, collection, and transportation of sour natural gas in aggressive petrochemical and acidic gas field environments. Designed specifically for installations where hydrogen sulfide (H₂S) partial pressures exceed 0.0003 MPa and chloride ion (Cl⁻) concentrations are elevated, this coil tube provides superior resistance to sulfide stress cracking (SSC), hydrogen-induced cracking (HIC), and chloride-induced pitting and crevice corrosion. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product delivers an exceptional balance of mechanical strength, corrosion resistance, and formability in a continuous coil configuration, minimizing field splicing and reducing installation costs for long-reach pipeline networks.
Material Grades & Properties
The coil tube is available in two primary material configurations to address the most demanding sour service environments:
- SAF 2205 Duplex Stainless Steel: A austenite-ferrite dual-phase alloy offering approximately 2.5× the yield strength of conventional 304/316 austenitic stainless steels, with a PREN (Pitting Resistance Equivalent Number) of 34–38, providing excellent resistance to chloride pitting and sulfide stress cracking.
- SAF 2507 Super Duplex Stainless Steel: A premium-grade alloy with a PREN of 38–42, engineered for extreme sour gas service with enhanced resistance to HIC, SOHIC (stress-oriented hydrogen-induced cracking), and high-temperature chloride corrosion.
- Inconel 625 Clad/Lined Configuration: A nickel-chromium-molybdenum alloy cladding or lining applied to a carbon or low-alloy steel substrate, providing near-absolute immunity to H₂S corrosion, HIC, and chloride attack while maintaining structural integrity and economic efficiency.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Material Grades | SAF 2205 / SAF 2507 Duplex SS; Inconel 625 Clad/Lined |
| Applicable Standard | ASTM A790 / ASTM A240 / ASTM B619 (Inconel 625) |
| Outer Diameter Range | Ø15 mm – Ø219 mm (configurable) |
| Wall Thickness Range | 1.5 mm – 12.0 mm |
| Coil Length | Up to 2000 m per coil (continuous) |
| H₂S Partial Pressure | > 0.0003 MPa (NACE MR0175/ISO 15156 Class 1–3) |
| Chloride Ion Tolerance | > 10,000 ppm (SAF 2507); > 50,000 ppm (Inconel 625) |
| Operating Temperature Range | -60°C to +350°C |
| Operating Pressure | Up to 16 MPa (design-dependent) |
| Surface Finish | Mill finish / 2B / BA / Custom (Ra ≤ 0.8 μm available) |
| Compliance | NACE MR0175/ISO 15156 Full Compliance (SSC, HIC, SOHIC, HTHA) |
| Hardness (HRC) | ≤ 22 HRC (per NACE MR0175 hardness requirement) |
Manufacturing Process
The coil tube is produced through a rigorous, multi-stage manufacturing process that ensures full NACE MR0175 compliance and consistent metallurgical quality:
- Hot Rolling & Annealing: High-purity duplex stainless steel or nickel-alloy ingots are hot-rolled into strip and annealed to achieve the target dual-phase microstructure (ferrite content 35–65% for SAF 2205/2507).
- Cold Reduction & Forming: Precision cold-rolled strip is formed into a seamless or welded coil tube via continuous forming, with strict dimensional control to ±0.1 mm tolerance.
- Heat Treatment & Stress Relief: Solution annealing at 1050–1100°C followed by controlled cooling to optimize phase balance and suppress sigma phase formation.
- Inconel 625 Cladding (if applicable):strong> Explode-bond cladding or explosion welding process to achieve metallurgical bonding between the Inconel 625 cladding layer and the substrate, with cladding thickness of 1.5–3.0 mm minimum.
- Non-Destructive Testing: 100% eddy current (EC) testing, ultrasonic testing (UT), and dye penetrant inspection (DPI) for weld seam integrity.
- NACE MR0175 Compliance Testing: Full suite of SSC (per ASTM G142), HIC/SOHIC (per ASTM G283), and HTHA (per ASTM G178) testing performed on every production lot.
- Final Dimensional & Chemical Verification: Spectrographic analysis (OES/LIBS), dimensional gauging, and hardness verification on each coil.
Applications
This coil tube is specifically designed for the following sour gas field applications within the petrochemical and upstream oil & gas sectors:
- High-H₂S Sour Gas Gathering Pipelines: Collection and transportation of raw sour natural gas from wellheads to processing facilities where H₂S partial pressures exceed 0.0003 MPa.
- Acid Gas Processing Plants: Internal piping, heat exchanger coils, and transfer lines within amine treating units (MEA, DEA, MDEA systems).
- Sour Water Injection Systems: Re-injection lines carrying chloride-laden produced water back into reservoir formations.
- Gas Sweetening & Desulfurization Units: Corrosion-resistant tubing for Claus process units and hydrotreating facilities.
- Subsea & Offshore Sour Gas Collection: Continuous coil deployment for subsea manifolds, umbilicals, and flowlines in offshore acidic gas fields.
- CO₂ Sequestration & Transportation: Long-reach pipelines for CO₂ transport with trace H₂S and chloride contamination.
Quality Certifications & Compliance
Every production lot of this coil tube undergoes comprehensive third-party verification and holds the following certifications and compliance credentials:
- NACE MR0175/ISO 15156: Full compliance with all four damage mechanisms — SSC, HIC, SOHIC, and HTHA — verified through ASTM G142, ASTM G283, and ASTM G178 testing.
- API 5CT / API 5L: Compliance with API standards for casing, tubing, and line pipe applications in sour environments.
- ASME Section VIII: Materials certified for pressure vessel and piping applications per ASME Boiler and Pressure Vessel Code.
- ISO 9001:2015: Quality management system certification for the manufacturing facility.
- ISO 14001:2015: Environmental management system certification.
- Third-Party Inspection (TPI): Available with SGS, Bureau Veritas, or DNV inspection and material test reports (MTRs) per EN 10204 Type 3.1.
- Mill Test Reports (MTRs): Comprehensive chemical composition, mechanical properties, hardness, phase balance, and NACE compliance data provided with every shipment.
Unique Selling Points
Engineered for the Harshest Sour Environments: Unlike standard austenitic stainless steel tubing, this duplex and Inconel 625 coil tube is specifically qualified for H₂S partial pressures above 0.0003 MPa with high chloride concentrations — the exact conditions that cause catastrophic failure in conventional 304/316L materials.
Full NACE MR0175 Compliance: Every lot is tested against all four NACE damage mechanisms, eliminating the risk of sulfide stress cracking, hydrogen-induced cracking, and stress-oriented hydrogen-induced cracking that plague unqualified materials in sour service.
Continuous Coil Configuration: Available in lengths up to 2,000 meters per coil, dramatically reducing the number of field welds and potential failure points in long-reach gathering pipelines.
Superior Strength-to-Weight Ratio: Duplex grades offer 2.5× the yield strength of 316L, enabling thinner wall designs that reduce material costs and installation weight while maintaining pressure integrity.