High H₂S Gathering & Transmission Pipeline Coiltube
Product Code: JX-CT-122 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd
1. Product Overview
This coil tube (coiltube) product is purpose-engineered for the gathering and transmission of high hydrogen sulfide (H₂S) bearing natural gas and oil streams in acidic gas field environments. Designed for the petroleum and petrochemical sector, this product addresses the most corrosive and operationally demanding scenarios encountered in upstream hydrocarbon production, where H₂S partial pressures exceed 0.0003 MPa (NACE MR0175 threshold for sour service) and chloride ion (Cl⁻) concentrations are significantly elevated.
Unlike conventional seamless or welded pipe, coil tube is supplied in continuous coil form, enabling high-efficiency downstream processing—including cold drawing, rolling, and cutting—into a wide range of final dimensions. This makes it an economically superior starting material for fabricating small-to-medium diameter tubing, heat exchanger tubes, and specialty components used in sour gas processing facilities, acid gas injection systems, and produced water handling infrastructure.
2. Material & Properties
Given the aggressive dual-threat environment of H₂S-induced sulfide stress cracking (SSC) and chloride pitting/crevice corrosion (CSC), the following material grades are specified:
2.1 Primary Material Options
- Duplex Stainless Steel 2205 (UNS S31803 / S32205): A 22% Cr, 5% Ni, 3% Mo, 1.5% N alloy offering approximately 2× the yield strength of austenitic 304/316, with excellent resistance to both SSC and Cl⁻-induced pitting. PREN (Pitting Resistance Equivalent Number) ≥ 34.
- Super Duplex Stainless Steel 2507 (UNS S32750 / S32760): A 25% Cr, 7% Ni, 3% Mo, 0.7% N alloy with PREN ≥ 38, providing superior resistance in environments with Cl⁻ concentrations exceeding 50,000 ppm and elevated temperatures.
- Inconel 625 Clad (UNS N06625 cladding over carbon/low-alloy steel base): A nickel-chromium-molybdenum alloy (59% Ni, 21% Cr, 9% Mo) providing exceptional resistance to SCC, pitting, and general corrosion in the most severe sour service environments. Clad thickness typically ≥ 1.5 mm.
2.2 Key Mechanical & Corrosion Properties
| Property | 2205 Duplex | 2507 Super Duplex | Inconel 625 (Clad) |
|---|---|---|---|
| Yield Strength (Min.) | 450 MPa | 550 MPa | 275 MPa (clad layer) |
| Tensile Strength (Min.) | 550 MPa | 620 MPa | 450 MPa (clad layer) |
| PREN (Pitting Resistance Equivalent Number) | ≥ 34 | ≥ 38 | — (Ni-based; inherently resistant) |
| H₂S Service Limit (Partial Pressure) | > 0.0003 MPa | > 0.0003 MPa | Unlimited (NACE compliant) |
| Maximum Service Temperature | 250 °C | 300 °C | 593 °C |
| Cl⁻ Tolerance (at 25 °C) | Up to 50,000 ppm | Up to 100,000 ppm | Unlimited |
| SSC Resistance (NACE MR0175) | Full compliance | Full compliance | Full compliance |
| Equivalent Weight (kg/m³) | 7,800 | 7,800 | 8,440 (clad layer) |
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Form | Coil tube (cold-rolled coil for tube drawing) | — |
| Outer Diameter (OD) | 6.35 mm – 114.3 mm (1/4" – 4-1/2") | ASTM A778 / ASTM A312 |
| Wall Thickness | 0.5 mm – 6.35 mm (0.020" – 1/4") | ASTM A778 |
| Coil Inner Diameter (ID) | 300 mm – 600 mm (12" – 24") | Manufacturer standard |
| Coil Weight | Up to 5,000 kg per coil | — |
| Surface Finish | 2B (cold-rolled and annealed) or BA (Bright Annealed) | ASTM A480 |
| Tolerance (OD) | ± 0.10 mm or ± 0.05 mm (on request) | ASTM A778 |
| Tolerance (Thickness) | ± 0.025 mm | ASTM A778 |
| Delivery Condition | Annealed (soft) or cold-worked (hardened) | — |
| End Condition | Slit ends or beveled ends | — |
| Coating (Optional) | None (bare metal); passivated per ASTM A967 | ASTM A967 |
| Maximum H₂S Partial Pressure | > 0.0003 MPa (sour service) | NACE MR0175 / ISO 15156 |
| Cl⁻ Environment | High chloride (≥ 50,000 ppm) | — |
| Weldability | Full weldability (GTAW, GMAW, ERW) | ASTM A778 |
| Heat Treatment | Solution annealed at 1020–1120 °C (duplex); 1150–1250 °C (Inconel 625) | ASME SA-790 / ASTM B625 |
4. Manufacturing Process
4.1 Duplex Stainless Steel Coil (2205 / 2507)
- Slab Casting: Continuous casting of ultra-low carbon (C ≤ 0.030%) duplex stainless steel slabs with precise control of nitrogen content (0.14–0.25% for 2205; 0.24–0.32% for 2507).
- Hot Rolling: Multi-stand hot rolling mill reducing slab to semi-finished strip (1.2–2.5 mm thickness).
- Pickle & Passivate: Acid pickling (HNO₃ + HF blend) to remove scale, followed by passivation to establish protective chromium oxide film.
- Cold Rolling: Multi-pass cold rolling to achieve final coil thickness with tight dimensional tolerances (± 0.025 mm).
- Intermediate Annealing: Solution annealing at 1050–1100 °C in controlled atmosphere (dew point ≤ -50 °C) to restore ductility and maintain austenite-ferrite balance (40–60% ferrite by volume).
- Final Cold Rolling & Annealing: Final gauge reduction followed by controlled cooling (≤ 10 °C/min through 870–480 °C range) to prevent σ-phase precipitation.
- Coil Winding: Automated coil winding with edge protection and moisture barrier packaging.
4.2 Inconel 625 Clad Coil
- Base Steel Preparation: Low-carbon or low-alloy steel coil (e.g., ASTM A516 Gr.70) hot-rolled to specified gauge.
- Inconel 625 Cladding Strip: Cold-rolled Inconel 625 (UNS N06625) strip produced to specified thickness (≥ 1.5 mm).
- Diffusion Bonding / Explosion Welding: Metallurgical bonding of Inconel 625 cladding to steel base via controlled thermal diffusion bonding at 1100–1200 °C, or explosive cladding for high-integrity interfaces.
- Thermal Treatment: Solution heat treatment at 1150 °C with water quench to dissolve carbides and ensure uniform microstructure.
- Quality Verification: Interface bond strength testing per ASTM A403, hardness mapping, and metallographic inspection.
- Cold Rolling (if required): Final cold rolling to achieve target dimensions while maintaining cladding integrity.
5. Applications
This coiltube product is specifically designed for the following applications in acidic gas field environments:
- Sour Gas Gathering Lines: Collection and transmission of H₂S-bearing natural gas from wellheads to processing facilities, where H₂S partial pressures routinely exceed 0.0003 MPa.
- Acid Gas Injection (AGI) Systems: High-pressure tubing for injecting H₂S-rich acid gas back into depleted reservoirs for storage and pressure maintenance.
- Produced Water Handling: Corrosion-resistant tubing for handling produced water with elevated Cl⁻ concentrations (20,000–80,000 ppm) and dissolved H₂S.
- Gas-Liquid Separators & Heat Exchangers: Fabrication of tube bundles and internals for separators, condensate drums, and heat exchangers operating in sour service.
- Well Completion Tubing: Drawn and cut from coil into small-diameter tubing for downhole completion strings in sour wells.
- Refinery Acid Gas Handling: Piping and components for amine treating units, flare headers, and sulfur recovery facilities.
- Offshore Sour Gas Platforms: Structural tubing and heat exchanger components for offshore platforms processing sour hydrocarbon streams in marine environments.
6. Quality Certifications & Compliance
6.1 NACE MR0175 / ISO 15156 — Full Compliance
All material supplied complies fully with NACE International MR0175/ISO 15156 (Petroleum and Natural Gas Industries — Materials for use in H₂S-containing environments in oil and gas production), covering all relevant clauses:
- Clause 2 (Carbon and Low Alloy Steels): Hardness ≤ 22 HRC for base steel layers in clad configurations.
- Clause 3 (Stainless Steels): Full compliance for duplex stainless steel grades including hardness limits, weld overlay requirements, and post-weld heat treatment protocols.
- Clause 5 (Nickel and Nickel Alloys): Compliance for Inconel 625 cladding, including solution heat treatment verification and hardness limits (≤ 350 HV for Inconel 625).
- Clause 6 (Welding Consumables): All welding consumables and filler metals specified per NACE MR0175 requirements for each material grade.
- Clause 7 (Fabrication): Post-fabrication hardness verification, visual inspection, and non-destructive testing (NDT) per NACE requirements.
6.2 Additional Certifications & Standards
| Standard / Certification | Scope of Compliance |
|---|---|
| ASTM A778 | Standard Specification for Stainless Steel and Alloy Steel Strip and Sheet for Cold-Formed Tubes |
| ASTM A312 / A213 | Standard Specification for Seamless and Welded Austenitic Cr-Ni Stainless Steel Tubing (reference) |
| ASTM A928 | Standard Specification for Duplex (Austenitic-Ferritic) Stainless Steel Plate and Sheet for Pressure Vessels |
| ASME SA-790 / SA-789 | Standard for Nickel-Chromium-Iron-Molybdenum Alloy (Inconel 625) |
| ASTM A403 | Standard Specification for Clad Steel Plates for Pressure Vessels |
| ASTM A967 | Standard Practice for Chemical Passivation of Stainless Steel Parts |
| EN 10204 3.1 | Material Test Certificate (MTC) — Third-party inspection and testing |
| ISO 9001:2015 | Quality Management System Certification (Manufacturer) |
| API 5CT / API 5L | Applicable for tubing and pipe specifications in oil and gas service |
| CRN (Canadian Registration Number) | Available for pressure vessel applications (upon request) |
| PED 2014/68/EU | Pressure Equipment Directive compliance (upon request) |
6.3 Testing & Inspection Regime
- Chemical Analysis: Full spectrographic analysis (OES) of every heat, with supplementary carbon and nitrogen determination per ASTM E1019.