NACE MR0175/ISO 15156 Compliant Stainless Steel Coil Tube — Anti-Sulfide Stress Cracking (SSC) Resistant Product
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 89) offers a premium-grade stainless steel coil tube engineered specifically for demanding oil and gas production environments where hydrogen sulfide (H2S) exposure is present. This product line is certified in accordance with NACE MR0175/ISO 15156 — the internationally recognized standard governing materials for use in oil and gas production facilities exposed to H2S. The coil tube form factor provides excellent formability and efficient downstream processing, making it ideal for heat exchangers, condensers, separators, and subsea production manifolds.
The primary engineering challenge in sour service is the prevention of Sulfide Stress Cracking (SSC) and Hydrogen-Induced Cracking (HIC), which can cause catastrophic, often brittle, failure of metallic components. This product addresses these degradation mechanisms through carefully controlled metallurgical composition, hardness management, and rigorous qualification testing.
Material & Properties
The stainless steel coil tube is manufactured from austenitic stainless steel grades (typically 304, 316, 316L, 321, or duplex 2205) that inherently resist SSC due to their face-centered cubic (FCC) or duplex crystal structures. Key material characteristics include:
- Crystal Structure: Austenitic (γ) or Duplex (α + γ) — both inherently resistant to hydrogen embrittlement compared to martensitic or heavily cold-worked ferritic structures.
- Maximum Hardness Limit: ≤ 22 HRC (Rockwell C) for austenitic grades in accordance with NACE MR0175/ISO 15156 Part 2; ≤ 300 HV for certain ferritic grades per Part 3. Hardness is strictly controlled to prevent SSC susceptibility.
- Chloride Content: Tightly controlled to minimize intergranular corrosion (IGC) risk; carbon equivalent ≤ 0.03% for low-carbon "L" grades.
- Equivalent Nickel Number (EN): ≥ 29 for austenitic stainless steels per NACE MR0175/ISO 15156-2, ensuring adequate austenite stability.
- Temperature Range: Qualified for service from cryogenic temperatures up to 120°C (248°F) under standard conditions; extended temperature limits apply for specific grades and test conditions.
- Partial Pressure of H2S: Suitable for environments with H2S partial pressures up to 100% (depending on grade and temperature), with reduced limits at elevated temperatures and in the presence of chlorides.
Specifications
| Parameter | Specification / Requirement | Test Standard |
|---|---|---|
| Compliance Standard | NACE MR0175/ISO 15156 Parts 1, 2, and 3 | — |
| SSC Test (Ferritic & Martensitic) | ASTM G15 (or ASTM G142) — Acid Solution Test | ASTM G15 / ASTM G142 |
| HIC Test | ASTM G283.3 (Hydrogen-Induced Cracking Test) | ASTM G283.3 |
| Maximum Hardness — Austenitic SS | ≤ 22 HRC | ASTM E18 |
| Maximum Hardness — Duplex SS | ≤ 32 HRC | ASTM E18 |
| Equivalent Nickel Number (EN) | ≥ 29 (Austenitic grades) | NACE MR0175/ISO 15156-2 |
| Heat Treatment Restriction | No hardening heat treatment permitted; solution annealing only | Manufacturer Procedure |
| Chemical Composition | Per ASTM A240 / EN 10088 / ASTM A270 | ASTM E4 / ASTM E1251 |
| Mechanical Properties | Tensile Strength, Yield Strength, Elongation per grade specification | ASTM E8 |
| Corrosion Testing | ASTM G48 (Pitting), ASTM G59 (Crevice), ASTM G150 (Intergranular) | Respective ASTM Standards |
| Product Form | Coil Tube (盘管 / Coiltube) — continuous coil configuration | — |
Manufacturing Process
The manufacturing of NACE MR0175/ISO 15156 compliant stainless steel coil tube follows a rigorously controlled sequence to ensure SSC/HIC resistance is maintained throughout production:
- Raw Material Selection: Only certified ingots or slabs with traceable chemical composition are used. The equivalent nickel number (EN) is verified at the melt level to ensure compliance with NACE MR0175/ISO 15156-2 requirements.
- Hot Rolling: Billets are reheated and hot-rolled into strip or tube blanks at controlled temperatures to achieve the desired austenitic microstructure with uniform grain size.
- Solution Annealing: The hot-rolled product undergoes solution annealing at temperatures typically between 1010°C and 1150°C, followed by rapid water quenching. This step dissolves carbide precipitates and restores full austenite, ensuring low hardness and high corrosion resistance. No hardening heat treatments (e.g., precipitation hardening, martensitic quenching) are permitted under any circumstances.
- Forming / Coil Tube Fabrication: The annealed strip is precision-formed into coil tube geometry. Cold working during forming is limited to ensure the final hardness does not exceed the NACE MR0175/ISO 15156 maximum hardness limits. Interpass annealing may be performed if cumulative cold work exceeds allowable strain.
- Final Annealing (if required): If cold forming introduces hardness above the specified limit, a final stress-relief or solution anneal is performed to bring hardness back within specification.
- Surface Treatment: Pickling and passivation are applied to remove mill scale and restore the passive chromium oxide film, ensuring optimal corrosion resistance.
- Quality Inspection & Testing: Each production lot undergoes comprehensive testing including chemical analysis, mechanical testing, hardness measurement, SSC testing (ASTM G15), and HIC testing (ASTM G283.3) as applicable.
Applications
NACE MR0175/ISO 15156 compliant stainless steel coil tubes are deployed in critical sour service applications across the upstream oil and gas industry:
- Upstream Production: Gas-liquid separators, pressure vessels, and production manifolds in sour gas fields containing H2S at partial pressures up to 100%.
- Heat Exchangers & Condensers: Coil tubes used in air coolers, condensers, and reboilers where H2S-laden hydrocarbons are processed.
- Subsea Systems: Subsea production manifolds, umbilicals, and flow lines where SSC resistance is critical under high pressure and corrosive environments.
- Refining & Petrochemical: Hydrodesulfurization (HDS) units, amine treating systems, and flare headers in refineries processing sour crude.
- Injection & Wellhead Equipment: Gas injection lines, wellhead assemblies, and Christmas tree components in sour well environments.
- Offshore Platforms: Platform topsides piping, heat exchanger bundles, and process equipment on offshore drilling and production platforms.
Quality Certifications
Every coil tube product from Wenzhou Jixing Metal Materials Co., Ltd. is backed by a comprehensive quality assurance framework:
- NACE MR0175/ISO 15156 Certification: Full compliance with Parts 1 (general requirements), Part 2 (austenitic stainless steels), and Part 3 (ferritic stainless steels) as applicable. Certification is maintained through ongoing audit and testing programs.
- API Q1 / ISO 9001 Quality Management: The manufacturing facility operates under a certified quality management system ensuring traceability, process control, and continuous improvement.
- Third-Party Inspection (TPI): Optional independent inspection by recognized bodies (e.g., BV, DNV, Lloyd's Register, SGS) for verification of compliance with NACE MR0175/ISO 15156 requirements.
- Mill Test Reports (MTR): Each shipment is accompanied by detailed mill test reports documenting chemical composition, mechanical properties, hardness values, and SSC/HIC test results.
- Material Traceability: Full heat-to-heat traceability from raw material mill certificates through final product dispatch, ensuring complete accountability across the supply chain.
Unique Selling Points
- Proven Sour Service Reliability: Engineered to prevent the two most destructive failure modes in H2S environments — Sulfide Stress Cracking (SSC) and Hydrogen-Induced Cracking (HIC) — through strict hardness control, verified metallurgical composition, and rigorous qualification testing.
- Coil Form Efficiency: The coil tube configuration enables high-speed, low-waste downstream fabrication, reducing manufacturing costs and lead times for end users compared to straight-length tube.
- Full Standard Compliance: Not merely "suitable" but fully certified to NACE MR0175/ISO 15156 — the global benchmark for sour service materials — providing assurance to project engineers, procurement authorities, and regulatory bodies.
- Elimination of Hardening Heat Treatments: The manufacturing process explicitly prohibits any heat treatment that could increase hardness beyond NACE limits, ensuring long-term SSC resistance is not compromised by post-production processing.
- Comprehensive Testing Protocol: Every production lot is subjected to ASTM G15 SSC testing and ASTM G283.3 HIC testing, providing empirical proof of resistance to hydrogen-induced degradation mechanisms.
Note: NACE MR0175/ISO 15156 is periodically revised. Users are advised to confirm compliance with the current edition (e.g., NACE MR0175/ISO 15156:2020 or latest) at the time of procurement. Wenzhou Jixing Metal Materials Co., Ltd. maintains ongoing compliance with the most current revision of the standard.