Stainless Steel Coil Tube for Waste Heat Boiler Applications
Product Overview
The Stainless Steel Coil Tube (Product No. 1580) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered helical tube product specifically designed for integration into waste heat recovery boilers and high-temperature heat exchange systems. This coil tube adopts a continuous helical geometry that maximizes surface area-to-volume ratio, thereby enhancing thermal transfer efficiency while minimizing pressure drop across the heat exchanger. The product represents a state-of-the-art solution in spiral coil tube structural design and manufacturing, combining advanced metallurgical properties with rigorous fabrication standards to deliver reliable performance under demanding industrial conditions.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior resistance to oxidation, corrosion, and thermal cycling degradation. The following material characteristics are typical:
- Base Alloy: Grade 304 (UNS S30400), Grade 316L (UNS S31603), or Grade 321 (UNS S32100), selected according to application-specific environmental conditions.
- Chromium Content: 18–21%, providing a robust passive oxide layer for corrosion resistance.
- Nickel Content: 8–12%, ensuring stable austenitic microstructure and ductility at elevated temperatures.
- Maximum Service Temperature: Up to 870°C (continuous), with intermittent peaks tolerable to 1100°C for 304-grade variants.
- Tensile Strength (Annealed): ≥ 515 MPa (Grade 304); ≥ 485 MPa (Grade 316L).
- Yield Strength (0.2% offset): ≥ 205 MPa (annealed condition).
- Thermal Conductivity: 16.3 W/(m·K) at 100°C (Grade 304), decreasing with temperature.
- Coefficient of Thermal Expansion: 17.3 × 10⁻⁶ /K (20–100°C range).
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and mild acidic environments; Grade 316L offers enhanced pitting and crevice corrosion resistance due to molybdenum addition (2–3% Mo).
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Helical Coil Tube (WJX-CT-1580) |
| Outer Diameter (OD) | 19 mm – 76 mm (customizable) |
| Wall Thickness | 1.0 mm – 4.0 mm |
| Helix Pitch | 100 mm – 400 mm (adjustable per thermal design) |
| Helix Diameter | 300 mm – 2000 mm |
| Tube Length (Developed) | Up to 500 m continuous helix |
| End Form | Plain, beveled, or threaded (per client specification) |
| Surface Finish | Pickled and passivated (Ra ≤ 0.8 μm) |
| Manufacturing Standard | ASTM A213, GB/T 14976, EN 10216-5 |
| Applicable Medium | Flue gas, steam, hot water, superheated air, non-corrosive process fluids |
| Operating Pressure | Up to 1.6 MPa (design-dependent) |
| Operating Temperature Range | -40°C to 870°C |
| Welding Method | TIG (GTAW) seamless weld, 100% radiographic inspection |
Manufacturing Process
The production of the WJX-CT-1580 coil tube follows a multi-stage manufacturing workflow designed to ensure geometric accuracy, metallurgical integrity, and dimensional consistency:
- Raw Material Selection: Certified cold-rolled stainless steel coil is procured from qualified mills, with each lot accompanied by a mill test certificate (MTC) verifying chemical composition and mechanical properties.
- Coil Straightening and Sizing: The flat coil is fed through precision roller straighteners to achieve uniform cross-sectional geometry and eliminate residual stress from the cold-rolling process.
- Helical Forming: Using CNC-controlled helical bending machinery, the tube is wound into the specified spiral geometry with precise control over pitch, helix diameter, and tube cross-sectional deformation. The forming process is optimized to minimize ovality (≤ 2% of OD) and maintain wall thickness uniformity.
- Welding (if segmented): For multi-section coil assemblies, butt welds are performed using Tungsten Inert Gas (TIG/GTAW) welding with filler wire matching the base alloy. Weld parameters are qualified per ASME Section IX.
- Stress Relief Annealing: Post-forming annealing is conducted at 1050°C ± 25°C followed by controlled cooling to eliminate residual stresses introduced during cold forming, restoring full ductility and mechanical properties.
- Pickling and Passivation: The formed coil tube undergoes acid pickling to remove surface scale and oxide, followed by passivation treatment to establish a stable chromium oxide protective layer.
- Quality Inspection: Final inspection includes dimensional verification (helix pitch, diameter, tube OD/WT), visual examination, dye penetrant testing (PT) or radiographic testing (RT) of welds, and hydrostatic pressure testing at 1.5× design pressure.
Applications
The WJX-CT-1580 Stainless Steel Coil Tube is engineered for demanding thermal applications including but not limited to:
- Waste Heat Recovery Boilers (WHRB): Primary application — capturing high-temperature flue gas energy to generate steam or hot water, commonly used in power generation, cement, and petrochemical industries.
- Solar Thermal Collectors: Concentrated solar power (CSP) systems where helical tubes serve as absorber elements under intense radiant heat flux.
- Industrial Furnace Heat Exchangers: Regenerative and recuperative heat exchangers in metallurgical and glass manufacturing processes.
- Chemical Process Heaters: Process fluid preheating and superheating in continuous chemical manufacturing operations.
- Marine and Offshore Waste Heat Systems: Exhaust gas boilers and economizers on marine vessels and offshore platforms, leveraging the corrosion resistance of stainless steel in humid, chloride-rich environments.
- Power Plant Auxiliary Systems: Flue gas desulfurization (FGD) upstream heat recovery and stack gas cooling applications.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring product conformity to international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ASME "S" Stamp — Authorization for pressure vessel and piping fabrication (where applicable)
- ASTM A213 — Seamless austenitic stainless steel tubes for high-temperature service
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- EN 10216-5 — European standard for welded stainless steel tubes
- NACE MR0175 / ISO 15156 — Compliance for sour service applications (Grade 316L variant)
- Third-Party Inspection (TPI): Available upon request — SGS, Bureau Veritas, or TÜV Rheinland inspection and certification services
Unique Selling Points
The WJX-CT-1580 coil tube distinguishes itself through several competitive advantages:
- Optimized Helical Geometry: CNC-precision forming ensures consistent pitch and minimal cross-sectional distortion, maximizing heat transfer coefficient while maintaining structural integrity under thermal cycling.
- Seamless Integration Capability: The continuous helical design eliminates internal welds, reducing potential failure points and enabling uniform fluid flow distribution throughout the coil.
- Extended Service Life: High-grade austenitic stainless steel with full stress-relief annealing provides resistance to thermal fatigue, creep, and oxidative scaling at elevated operating temperatures.
- Customizable Configuration: Flexible manufacturing capability accommodates project-specific requirements for helix diameter, pitch, tube dimensions, and end connections, enabling seamless integration into diverse boiler designs.
- Comprehensive Traceability: Each production batch is accompanied by full material traceability documentation, including mill certificates, heat numbers, welding procedure specifications (WPS), and inspection records.
- Proven Waste Heat Boiler Expertise: Drawing upon extensive experience in spiral coil tube structural design and manufacturing for waste heat recovery systems, the product delivers validated thermal performance and mechanical reliability.