Stainless Steel Spiral Coil Tube — Waste Heat Boiler Section Retrofit Solution
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 452) manufactures high-performance stainless steel spiral coil tubes (Coil Tubes) engineered specifically for gasifier waste heat boiler (WHSB) sections in integrated coal gasification and combined cycle power generation systems. These coil tubes are the core heat transfer elements in the waste heat recovery system of pressurized and atmospheric gasifiers, where they absorb radiant and convective heat from high-temperature syngas (typically 1,200–1,500 °C) and transfer it to the working fluid (water/steam) flowing through the tube lumen.
The spiral coil tube design provides superior heat transfer efficiency compared to conventional straight tube bundles due to the continuous helical geometry, which induces secondary flow (Dean flow) inside the tube, significantly enhancing the convective heat transfer coefficient. This product line has been validated through extensive field studies on gasifier waste heat boiler section retrofits, demonstrating reliable long-term performance under severe thermal cycling and high-temperature oxidizing environments.
Material & Properties
The spiral coil tubes are fabricated from austenitic stainless steels and heat-resistant alloys selected to withstand the extreme thermal, chemical, and mechanical demands of gasifier waste heat boiler service.
- Common Grade — 310S (UNS S31008): The primary material for high-temperature radiant coil sections. Contains 24–26% Cr and 19–22% Ni, offering excellent oxidation resistance up to 1,150 °C in continuous service and superior resistance to sulfur and ash fouling commonly encountered in coal-derived syngas environments.
- Alternative Grade — 309S (UNS S30908): Used in intermediate temperature zones (up to 925 °C continuous). Provides good creep resistance and weldability with 310S components.
- Alternative Grade — 321H (UNS S32109): Stabilized with titanium, employed in lower-temperature convective coil sections where intergranular corrosion resistance is critical.
- Alternative Grade — Incoloy 800H (UNS N08810): Nickel-based alloy for ultra-high temperature and high-pressure applications requiring superior creep rupture strength.
Key Mechanical Properties (310S, Annealed Condition):
- Tensile Strength (Rm): ≥ 520 MPa
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A): ≥ 40%
- Modulus of Elasticity: ~200 GPa
- Thermal Expansion Coefficient (20–1000 °C): 18.5 × 10⁻⁶ /°C
- Thermal Conductivity (at 1000 °C): ~33 W/(m·K)
- Density: 7.92 g/cm³
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Tube Outer Diameter (OD) | Φ34, Φ38, Φ42, Φ51, Φ60, Φ76 (customizable) | mm |
| Tube Wall Thickness | 2.5 – 6.0 | mm |
| Helix Coil Diameter (Mean) | 1,000 – 3,500 | mm |
| Helix Pitch | 60 – 250 | mm |
| Coil Length (per section) | 15 – 60 | m |
| Number of Coil Layers | 1 – 4 (arranged in spiral or stacked pattern) | — |
| Maximum Service Temperature | 1,150 (310S) / 1,200 (Incoloy 800H) | °C |
| Design Pressure | 2.5 – 22.5 | MPa |
| Surface Finish | Mill finish or pickled & passivated (Ra ≤ 1.6 μm) | — |
| End Preparation | Plain, beveled (37°), or flanged (per ASME B16.5) | — |
| Welding Method | GMAW (GTAW for repair) with matching filler wire | — |
| Standards Compliance | ASTM A312, ASTM A213, ASME B36.19M, EN 10217-7 | — |
Manufacturing Process
The production of spiral coil tubes involves a precisely controlled multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and long-term service reliability.
- Raw Material Selection & Inspection: Stainless steel seamless tubes are procured from certified mills conforming to ASTM A312 Type 310S or equivalent. Each batch undergoes spectrographic analysis (OES), mechanical testing, and non-destructive examination (eddy current per ASTM A776).
- Cold Bending / Helical Forming: The straight tube is cold-formed into a helical spiral using a precision CNC-controlled coil winding machine. The bending process is carefully controlled to maintain the minimum bend radius (typically ≥ 3× OD) and avoid wall thinning exceeding 10%. The helix geometry (coil diameter, pitch, and number of turns) is programmed per engineering drawings specific to each gasifier design.
- Stress Relief Annealing: After forming, the coil tubes are subjected to solution annealing at 1,050–1,100 °C followed by controlled cooling (air or furnace cool) to relieve residual bending stresses, restore full annealed microstructure, and ensure maximum corrosion resistance and ductility.
- Pickling & Passivation: The annealed coil tubes undergo acid pickling (nitric/hydrofluoric acid blend) to remove oxide scale, followed by passivation to establish a uniform chromium oxide passive film on the surface.
- Dimensional Verification: Post-manufacturing dimensional inspection includes helix diameter measurement (laser scanning or template method), pitch verification, straightness of coil axis, and wall thickness ultrasonic testing (UT) at critical locations.
- Non-Destructive Testing (NDT): 100% eddy current testing of the entire tube length, plus radiographic testing (RT) or ultrasonic testing of all weld joints. Penetrant testing (PT) is applied to surface-breaking defect detection.
- Hydrostatic Pressure Testing: Each coil tube assembly is pressure tested at 1.5× design pressure with distilled water to verify leak-tightness and structural integrity.
- Packaging & Shipping: Completed coil tubes are protected with moisture-absorbent desiccant, wrapped in VCI (Vapor Corrosion Inhibitor) film, and crated for shipment to the installation site.
Applications
The spiral coil tube products from Wenzhou Jixing Metal Materials Co., Ltd. are primarily deployed in the following industrial applications:
- Coal Gasification Waste Heat Boilers: Radiant and convective coil sections in Shell-type, Topsoe, and Texaco gasifiers operating at pressures of 2.5–8.0 MPa and gas temperatures exceeding 1,200 °C.
- Integrated Gasification Combined Cycle (IGCC) Power Plants: High-pressure steam generation through waste heat recovery from gasification off-gas.
- Methanol & Ammonia Synthesis Plants: Waste heat boilers in coal-to-chemical conversion processes.
- Biomass & Municipal Solid Waste (MSW) Gasification: Heat recovery systems in renewable energy gasification installations.
- Retrofit & Upgrading Projects: Replacement of legacy coil tube assemblies with improved 310S or Incoloy 800H designs to extend service life, improve thermal efficiency, and reduce unplanned outage frequency in existing gasifier installations.
- Hydrogen Production Facilities: Waste heat recovery in SMR (Steam Methane Reforming) and autothermal reforming (ATR) processes.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring traceability, conformance, and reliability across the entire product lifecycle.
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, testing, and delivery of stainless steel tube products.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ASME "S" Stamp / "U" Stamp — Authorized to manufacture pressure-bearing components per ASME Boiler and Pressure Vessel Code.
- EN 10204 3.1 Material Test Certificates — Provided with every shipment, including mill test reports, chemical analysis, mechanical test results, and NDT reports.
- CE Marking (PED 2014/68/EU) — Conformity with European Pressure Equipment Directive for Category II and III equipment.
- API 5L / API 5CT Compliance — Available upon request for oil and gas sector applications.
- Third-Party Inspection (TPI): Independent verification by SGS, Bureau Veritas, or DNV available for critical project deliveries.
Unique Selling Points
Field-Validated Retrofit Expertise: The spiral coil tube product line has been rigorously studied and optimized through actual gasifier waste heat boiler section retrofit projects. Real-world performance data confirms extended service life (3–5× improvement over legacy designs), reduced ash deposition rates, and enhanced thermal efficiency gains of 2–5% in waste heat recovery.
- Custom Helical Geometry Design: Parametric optimization of coil diameter, pitch, and layer configuration tailored to specific gasifier thermal profiles and available furnace space.
- Superior High-Temperature Oxidation Resistance: 310S and Incoloy 800H materials maintain structural integrity and minimum wall thickness loss (< 0.1 mm/year) under sustained 1,100 °C+ radiant heat exposure with sulfur-containing syngas.
- Enhanced Heat Transfer via Dean Vortex: The helical geometry generates secondary Dean flow inside the tube, increasing the convective heat transfer coefficient by 30–60% compared to straight tubes, reducing required tube surface area and system footprint.
- Full Traceability & Documentation: Every coil tube is traceable to its mill heat number, with complete NDT records, dimensional reports, and material certificates provided per EN 10204 3.1.
- Integrated Engineering Support: On-site installation guidance, thermal stress analysis, and post-commissioning performance monitoring support for critical gasifier projects.