Stainless Steel Coil Tube — High-Pressure Steam Superheater Grade
Product Overview
The Stainless Steel Coil Tube (Product No. 1477) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed for demanding high-temperature and high-pressure thermal applications, particularly in high-pressure steam superheater systems within power generation, petrochemical processing, and industrial heat exchange facilities. The coil tube is formed into a continuous helical or serpentine configuration to maximize heat transfer surface area within a compact footprint, enabling efficient thermal energy absorption and fluid conveyance under extreme operating conditions.
This product line is specifically developed with lessons learned from high-pressure steam superheater coil tube burnout analysis, incorporating metallurgical enhancements, optimized wall thickness profiles, and advanced manufacturing tolerances to mitigate common failure modes such as oxidative scaling, thermal fatigue cracking, intergranular corrosion, and creep rupture observed in conventional coil tube designs operating above 600°C.
Material & Properties
The coil tube is fabricated from high-performance austenitic and super-austenitic stainless steel grades engineered for superior resistance to high-temperature oxidation, carburization, and thermal cycling fatigue. Primary material specifications include:
- Grade 304 / 304L (UNS S30400 / S30403): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Suitable for superheater coil applications up to approximately 870°C in non-oxidizing atmospheres.
- Grade 316 / 316L (UNS S31600 / S31603): Molybdenum-enhanced austenitic stainless steel providing superior resistance to pitting and crevice corrosion in chloride-containing environments. Recommended for superheater coil tube sections exposed to flue gas with trace halogen compounds.
- Grade 310 / 310S (UNS S31000 / S31008): High-chromium, high-nickel austenitic stainless steel designed for sustained service temperatures up to 1150°C. Specifically selected for primary superheater coil tube runs subject to peak radiant heat flux.
- Grade 347H (UNS S34700): Stabilized austenitic stainless steel with niobium (Nb) addition to prevent intergranular sensitization during high-temperature service and welding operations. Preferred for critical superheater coil sections experiencing thermal cycling.
- Grade TP347H / TP347HN: ASTM-standardized variants with controlled carbon content and nitrogen addition for enhanced creep strength at elevated temperatures.
Mechanical Properties (Typical at Room Temperature):
- Tensile Strength (UTS): ≥ 515 MPa (Grade 304); ≥ 550 MPa (Grade 310S)
- Yield Strength (0.2% offset): ≥ 205 MPa (Grade 304); ≥ 205 MPa (Grade 310S)
- Elongation: ≥ 40% (Grade 304); ≥ 35% (Grade 310S)
- Density: 8.00 g/cm³ (Grade 304); 8.03 g/cm³ (Grade 310S)
- Thermal Conductivity at 100°C: 16.3 W/(m·K) (Grade 304); 21.5 W/(m·K) (Grade 310S)
- Linear Thermal Expansion (20–100°C): 17.3 × 10⁻⁶ /K (Grade 304); 18.0 × 10⁻⁶ /K (Grade 310S)
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / Coil Tube) |
| Product Number | 1477 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Outer Diameter (OD) | 14 mm – 114.3 mm (½" – 4½" nominal) |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm (customizable per application requirements) |
| Coil Diameter (CD) | 150 mm – 2000 mm (standard); custom diameters available |
| Coil Length per Spool | Up to 150 m per continuous coil (dependent on OD and WT) |
| Material Grades | 304, 304L, 316, 316L, 310, 310S, 347H, TP347H, TP347HN |
| Surface Finish | Mill finish (2B), pickled and passivated, or polished (Ra ≤ 0.4 μm) |
| Applicable Standards | ASTM A213/A213M, ASTM A269/A269M, ASME SA-213, ASME SA-269, GB/T 12770, GB/T 13296, EN 10216-5 |
| Maximum Operating Temperature | Up to 1150°C (Grade 310S); Up to 870°C (Grade 304/316) |
| Maximum Operating Pressure | Up to 25 MPa (250 bar), subject to wall thickness and temperature rating |
| Tolerance — OD | ±0.05 mm (precision grade); ±0.10 mm (standard grade) |
| Tolerance — Wall Thickness | ±10% (standard); ±5% (precision grade) |
| Coil Tolerance | ±2 mm (diameter); ±1° (winding angle deviation) |
| Delivery Form | Continuous coil (helical), serpentine coil, or U-bend coil assemblies |
| Packaging | Wooden crate with moisture-absorbent desiccant; custom packaging available |
Manufacturing Process
The production of the stainless steel coil tube adheres to a rigorously controlled multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and resistance to high-temperature service failure modes identified through superheater coil tube burnout analysis:
- Raw Material Procurement and Verification: Hot-rolled stainless steel strip or seamless tube blank material is sourced from certified mills with full mill test certificates (MTC) conforming to ASTM, EN, or GB standards. Incoming material undergoes 100% chemical composition verification via Optical Emission Spectroscopy (OES) and mechanical property confirmation through tensile testing.
- Heat Treatment — Solution Annealing: The base material is subjected to solution annealing at 1050°C – 1150°C (Grade 304/316) or 1050°C – 1100°C (Grade 310S), followed by rapid water quenching to dissolve carbides into the solid solution, ensuring maximum corrosion resistance and eliminating sensitization risks at grain boundaries.
- Precision Cold Forming / Seamless Tube Fabrication: Seamless tubes are produced via the Pilger rolling or plug piercing method to achieve precise OD and wall thickness tolerances. Alternatively, welded coil tubes are fabricated using Automatic Argon Arc Welding (A-TIG) or High-Frequency Induction Welding (HFW) processes, followed by post-weld heat treatment (PWHT) to homogenize the weld microstructure.
- Coil Forming: The formed tube is wound into the specified coil geometry using a CNC-controlled coil former. The winding process is optimized to minimize residual stresses and avoid work-hardening that could compromise high-temperature creep strength. A minimum bend radius of 3×OD is maintained to prevent wall thinning or ovality.
- Pickling and Passivation: The coil tube undergoes pickling in a nitric-hydrofluoric acid (HNO₃/HF) bath or citric acid solution to remove oxide scale, followed by passivation to form a protective chromium oxide layer (Cr₂O₃) on the surface. This step is critical for ensuring long-term corrosion resistance in high-temperature oxidizing environments.
- Non-Destructive Testing (NDT): All coil tubes undergo 100% Eddy Current Testing (ECT) for subsurface defect detection, Helium Leak Testing for weld integrity verification (welded variants), and Visual Inspection in accordance with ASME SA-213 and ASTM A213 requirements.
- Dimensional Verification: Final products are inspected for OD, wall thickness, coil diameter, and length using calibrated measuring instruments with documented traceability to national standards.
Applications
The stainless steel coil tube is engineered for the most demanding thermal processing environments, including but not limited to:
- High-Pressure Steam Superheaters: Primary application in utility power plants (subcritical, supercritical, and ultra-supercritical boilers) where coil tubes operate in radiant and convection superheater sections, absorbing peak heat flux from flue gas at temperatures ranging from 400°C to 1050°C.
- Reheat Steam Systems: Steam reheat coil assemblies in fossil-fuel and nuclear power stations requiring reliable thermal performance under cyclic pressure and temperature loading.
- Petrochemical Process Heaters: Fired process heaters and heat exchangers in refining and chemical processing facilities handling aggressive hydrocarbon streams and high-temperature catalysts.
- Industrial Waste Heat Recovery: Coil tube heat recovery units capturing thermal energy from industrial furnace exhaust and process off-gas streams.
- Chemical Processing Reactors: Jacketed reactor coil systems requiring corrosion-resistant heat transfer in aggressive chemical environments (acids, alkalis, halides).
- Pharmaceutical and Food Processing: Sanitary-grade coil heat exchangers for CIP (Clean-In-Place) compatible thermal processing of pharmaceutical intermediates and food-grade fluids.
- Marine and Offshore Applications: Steam superheater coil assemblies in marine power systems and offshore platform process units requiring resistance to chloride-induced corrosion.
Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that every stainless steel coil tube meets international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing, inspection, and delivery processes.
- ISO 14001:2015 — Environmental Management System certification ensuring environmentally responsible manufacturing practices.
- ASME "S" Stamp — Authorization for the manufacture of components conforming to ASME Boiler and Pressure Vessel Code requirements.
- TÜV / SGS / DNV — Third-party inspection and certification available upon customer request for critical applications.
- Mill Test Certificates (MTC) — Full traceability documentation conforming to EN 10204 Type 3.1 or Type 3.2 for each production batch, including chemical composition, mechanical test results, heat treatment records, and NDT reports.
- NACE MR0175 / ISO 15156 — Compliance available for coil tubes intended for use in sour service environments containing hydrogen sulfide (H₂S).
- Material Traceability: Each coil tube is marked with heat number, grade designation, standard reference, and manufacturing date code for full lifecycle traceability.
Unique Selling Points
- Burnout-Informed Design: The product specifications are directly informed by forensic analysis of high-pressure steam superheater coil tube burnout failures, incorporating enhanced wall thickness margins, optimized material selection, and improved heat treatment protocols to prevent premature failure.
- Custom Coil Geometry: Full capability for custom coil diameter, pitch, and configuration to match specific superheater or heat exchanger design requirements, enabling optimized heat transfer performance.
- Wide Material Range: Availability of multiple stainless steel grades — from standard 304/316 to high-temperature 310S and stabilized 347H — allows precise material matching to specific service temperature, pressure, and corrosion environments.
- Precision Manufacturing: CNC-controlled coil forming with tight dimensional tolerances (±0.05 mm OD, ±5% WT precision grade) ensures seamless integration into pre-engineered superheater assemblies.
- Full Traceability and Third-Party Inspection: Comprehensive MTC documentation and availability of independent third-party inspection provide assurance for critical infrastructure and power generation applications.
- Cost-Effective Continuous Length: Coil delivery format minimizes waste and reduces field fabrication labor compared to straight tube segments, offering significant cost advantages for large-scale superheater installations.
Disclaimer: The specifications described above represent typical values for the product line. Actual material properties, dimensional tolerances, and performance characteristics may vary depending on the specific grade, heat treatment condition, and application requirements. Customers are advised to consult with Wenzhou Jixing Metal Materials Co., Ltd. engineering team for application-specific material selection and specification confirmation prior to procurement.