Stainless Steel Coil Tube (Coil Tube) for High-Temperature Process Applications
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for demanding high-temperature, high-pressure process environments, particularly in the petrochemical, synthetic ammonia, and hydrogen production industries. This product category encompasses cold-drawn and hot-finished stainless steel tubes formed into continuous coil configurations, enabling efficient heat exchange performance in convective sections of process furnaces and reactors.
The product has been specifically validated for applications involving hydrogen retrofitting of synthetic ammonia plants, where convective section coil tubes face severe thermal stress, elevated operating temperatures, and aggressive chemical environments. Wenzhou Jixing Metal Materials Co., Ltd. supplies coil tubes that meet the stringent requirements of modern process engineering, ensuring long service life and operational safety under extreme conditions.
2. Material & Properties
2.1 Material Grades
- 304 / 304L (UNS S30400 / S30403) – Austenitic stainless steel with excellent general corrosion resistance and formability, suitable for moderate-temperature convective sections.
- 321 (UNS S32100) – Titanium-stabilized austenitic grade offering superior resistance to intergranular corrosion and thermal cycling, ideal for high-temperature coil tube service.
- 310S (UNS S31008) – High-chromium, high-nickel austenitic grade with exceptional oxidation resistance up to 1150°C, recommended for severe overheating zones in hydrogen production processes.
- 347H (UNS S34709) – Columbium-stabilized austenitic grade providing excellent high-temperature strength and resistance to sensitization in furnace convective sections.
- Custom Alloy Grades – Available upon request for specialized service conditions including superalloy compositions (e.g., Inconel 600, Incoloy 800) for extreme hydrogen environments.
2.2 Key Mechanical Properties (Typical)
- Tensile Strength: 515–830 MPa (depending on grade)
- Yield Strength: 205–415 MPa
- Elongation: 35–55% (minimum)
- Hardness: 150–210 HB (annealed condition)
- Thermal Stability: Maintains mechanical integrity up to 1100°C (310S grade)
- Creep Resistance: Optimized for sustained high-temperature service with minimal deformation
2.3 Chemical Composition Highlights
- Chromium (Cr): 18–32% depending on grade, providing passive film formation and oxidation resistance
- Nickel (Ni): 8–24%, ensuring austenitic microstructure stability
- Carbon (C): ≤ 0.08% (L-grades ≤ 0.03%), minimizing sensitization risk
- Titanium (Ti) / Columbium (Cb): Stabilizing elements in 321/347 grades to prevent chromium carbide precipitation
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code / No. | 1337 |
| Outer Diameter (OD) | 6.35 mm – 114.3 mm (¼" – 4½") |
| Wall Thickness | 0.5 mm – 8.0 mm |
| Coil Length | Customizable; typically 10 m – 200 m per coil |
| Coil Inner Diameter (ID) | 100 mm – 500 mm (adjustable per customer requirement) |
| End Configuration | Plain end, threaded, beveled, or custom per drawing |
| Surface Finish | Mill finish, polished (Ra ≤ 0.8 μm), or electropolished |
| Tolerance (OD) | ±0.05 mm to ±0.20 mm (per ASTM A213 / ASME standards) |
| Tolerance (Wall) | ±10% of nominal wall thickness |
| Operating Temperature Range | −196°C to +1150°C (grade-dependent) |
| Operating Pressure | Up to 150 bar (design-dependent) |
| Standards / Specifications | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771 |
| Delivery Condition | Annealed and Pickled (AP), Solution Annealed (SA), or Cold Worked (CW) |
| Coil Packaging | Wooden reel or steel drum with moisture-proof wrapping |
4. Manufacturing Process
4.1 Raw Material Selection
Wenzhou Jixing Metal Materials Co., Ltd. sources certified stainless steel strip and bar stock from reputable mills, ensuring full traceability through mill test certificates (MTC) conforming to EN 10204 Type 3.1. Incoming materials undergo rigorous chemical analysis (spectrometry) and mechanical testing prior to processing.
4.2 Production Workflow
- Material Preparation: Cold-rolled stainless steel strip is inspected, cleaned, and dimensionally verified. For larger diameters, seamless tube blanks are prepared from forged or extruded bar stock.
- Pipe Forming: Precision roll-forming or cold-drawing processes shape the strip or blank into seamless tubes with tight dimensional tolerances. Hot-forging and hot-drawing are employed for heavy-wall applications.
- Welding (if applicable):strong> For welded coil tubes, high-purity argon-shielded TIG (Tungsten Inert Gas) welding is used to ensure full-penetration welds with minimal oxidation. The weld seam undergoes 100% visual and dye-penetrant inspection.
- Coiling: Formed tubes are coiled onto precision-mandrel reels using computer-controlled winding equipment to ensure uniform curvature and prevent deformation or kinking.
- Heat Treatment: Solution annealing is performed at 1050–1150°C followed by controlled air or water quenching to restore full austenitic microstructure and eliminate residual stresses. Stabilization annealing at 870–900°C is applied for Ti/Cb-stabilized grades.
- Pickling & Passivation: Tubes are subjected to acid pickling (HNO₃/HF blend) to remove oxide scales, followed by passivation treatment to enhance the natural chromium oxide passive film.
- Final Inspection: Each coil undergoes dimensional verification, visual inspection, and non-destructive testing (NDT) including eddy current testing, ultrasonic testing (UT), and hydrostatic pressure testing.
4.3 Quality Control Measures
- 100% hydrostatic pressure testing per ASTM A213 requirements
- Eddy current inspection of weld seams (if applicable) to detect subsurface defects
- Hardness testing (Rockwell/Brinell) on every production lot
- Intergranular corrosion testing (ASTM A262 Practice E) for sensitization verification
- Full chemical composition analysis via optical emission spectrometry (OES)
5. Applications
5.1 Primary Application: Synthetic Ammonia Plant Hydrogen Retrofit
The stainless steel coil tubes are critically deployed in the convective sections of process furnaces within synthetic ammonia production facilities undergoing hydrogen retrofit upgrades. In such configurations, coil tubes serve as heat exchangers that recover waste heat from flue gases to preheat process streams (feed gas, synthesis gas, or reformate).
Following hydrogen retrofitting, convective section coil tubes frequently experience overheating conditions due to altered heat load distributions, increased gas velocities, and elevated wall temperatures exceeding original design parameters. The coil tubes supplied by Wenzhou Jixing Metal Materials Co., Ltd. are engineered to address these challenges through:
- Enhanced thermal stability – Grades such as 310S and 347H maintain structural integrity at temperatures exceeding 900°C, preventing creep deformation and tube rupture.
- Superior oxidation resistance – High chromium content (≥25% for 310S) forms a stable, adherent Cr₂O₃ scale that protects the base metal from accelerated oxidation at elevated temperatures.
- Hydrogen resistance – Austenitic microstructure provides resistance to hydrogen embrittlement and hydrogen attack, critical in hydrogen-rich process environments.
- Thermal cycling durability – Stabilized grades resist intergranular cracking during repeated start-up/shutdown thermal cycles.
5.2 Additional Applications
- Petrochemical industry: Crude oil distillation, steam cracking furnaces, and hydrotreating units
- Power generation: Boiler economizers, superheaters, and waste heat recovery systems
- Pharmaceutical & food processing: Sanitary heat exchangers requiring high-purity fluid handling
- Oil & gas: Subsea manifolds, chemical injection lines, and offshore heat exchangers
- Environmental engineering: Flue gas desulfurization (FGD) systems and emissions control equipment
- Specialty chemicals: Chlor-alkali plants, sulfuric acid production, and fluorine chemical processing
6. Unique Selling Points
Proven Performance in Overheating Scenarios: Wenzhou Jixing Metal Materials' coil tubes have been successfully deployed to resolve overheating issues in synthetic ammonia plant convective sections after hydrogen retrofit, demonstrating superior thermal management capabilities validated through real-world industrial operation.
- Grade Expertise: Deep technical knowledge of high-temperature stainless steel grades (310S, 347H, custom alloys) specifically selected for hydrogen-rich, high-temperature environments
- Custom Engineering: Tailored coil configurations, dimensions, and material selections to match specific furnace heat load profiles and process conditions
- Full Traceability: Complete documentation chain from raw material mill certificates to final product inspection reports
- Extended Service Life: Optimized material selection and manufacturing processes deliver 2–3× the service life compared to standard-grade coil tubes in severe thermal environments
- Comprehensive Testing: Multi-stage quality assurance including intergranular corrosion testing, elevated-temperature tensile testing, and long-term creep assessment
- Technical Support: Application engineering support for installation, commissioning, and operational monitoring of coil tube systems
7. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering all manufacturing and quality assurance processes |
| ISO 14001:2015 | Environmental Management System ensuring sustainable manufacturing practices |
| ASTM A213 | Standard specification for seamless and welded austenitic stainless steel tubes for high-temperature service |
| ASTM A269 | Standard specification for seamless and welded austenitic stainless steel tubes for chemical and similar severe service |
| ASME SA-213 | American Society of Mechanical Engineers specification for boiler, heat exchanger, and superheater tubes |
| EN 10216-5 | European standard for seamless and welded stainless steel tubes for pressure purposes – austenitic tubes |
| GB/T 12771 | Chinese national standard for seamless stainless steel tubes for fluid transport |
| NACE MR0175 / ISO 15156 | Material requirements for equipment in H₂S-containing environments in oil and gas production |
| Mill Test Certificate (MTC) | EN 10204 Type 3.1 certificates provided for every production lot |
| Third-Party Inspection | Available upon request (e.g., SGS, Bureau Veritas, TÜV) |
8. Conclusion
The Stainless Steel Coil Tube (Coiltube) product line from Wenzhou Jixing Metal Materials Co., Ltd. represents a highly specialized solution for the most demanding thermal and chemical process environments. With proven track record in resolving convective section overheating challenges in synthetic ammonia plants post-hydrogen retrofit, this product delivers exceptional reliability, extended service life, and compliance with the most stringent international standards. The combination of advanced material science, precision manufacturing, and comprehensive quality assurance makes these coil tubes the preferred choice for critical industrial heat exchange applications worldwide.