Stainless Steel Coil Tube — Regenerative Heat Recovery & Solar Thermal Application Series (Wenzhou Jixing Metal Materials Co., Ltd)
Product Code: No. 876 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Category: Specialized Stainless Steel Coil Tube for Thermal Energy Systems
1. Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product designed specifically for high-efficiency thermal exchange applications. Unlike conventional straight or bent tubing, coil tubes are formed into continuous helical or spiral geometries that maximize surface-area-to-volume ratios, thereby enhancing heat transfer efficiency in demanding industrial and renewable energy environments.
This product line has been extensively studied and validated in the context of Solar Thermal Collection Systems (太阳能集热系统) and Regenerative Coil Tube Biogas Engineering (回热盘管沼气工程). These applications demand exceptional thermal conductivity, corrosion resistance under aggressive chemical environments, and long-term structural integrity under cyclic thermal loading. The coil tube series from Wenzhou Jixing Metal Materials represents a mature, field-proven solution for these critical infrastructure requirements.
2. Material & Properties
Coil tubes are typically fabricated from austenitic stainless steel grades selected for their superior combination of mechanical properties, corrosion resistance, and thermal performance. The following material specifications are representative of the product range:
- Primary Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS316L (UNS S31603), and SUS321 (UNS S32100) — selected based on the specific service environment.
- Chemical Composition (Typical for SUS316L):
- Carbon (C): ≤ 0.03%
- Chromium (Cr): 16.0 – 18.0%
- Nickel (Ni): 10.0 – 14.0%
- Molybdenum (Mo): 2.0 – 3.0%
- Manganese (Mn): ≤ 2.0%
- Iron (Fe): Balance
- Key Physical Properties:
- Thermal Conductivity: 14–16 W/(m·K) at 25°C
- Specific Heat Capacity: 0.50 kJ/(kg·K) at 25°C
- Density: 8.00 g/cm³
- Thermal Expansion Coefficient: 16–17 × 10⁻⁶ /°C (20–100°C)
- Maximum Service Temperature: 870°C (SUS304/316); 1150°C (SUS321)
- Mechanical Properties (Cold-Drawn Condition):
- Tensile Strength (Rm): ≥ 520 MPa (SUS304); ≥ 530 MPa (SUS316L)
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A): ≥ 35%
- Hardness (HV): 120–220
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, weak acids, alkaline solutions, and chloride-containing media. SUS316L grade provides enhanced pitting and crevice corrosion resistance suitable for biogas environments containing hydrogen sulfide (H₂S) and carbon dioxide (CO₂).
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 108.0 mm | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 6.0 mm | ASTM A213 / GB/T 12771 |
| Coil Diameter | 50 mm – 2000 mm (customizable) | Manufacturer specification |
| Coil Length (Uncoiled) | 5 m – 200 m (continuous) | Manufacturer specification |
| Helix Pitch | 10 mm – 150 mm | Custom per application |
| Number of Turns | 5 – 500+ (as required) | Custom per application |
| Surface Finish | Bright annealed, polished (Ra ≤ 0.8 μm), or passivated | ASTM A270 / GB/T 4237 |
| Tolerance on OD | ±0.1 mm (precision grade); ±0.3 mm (standard grade) | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| End Condition | Plain, beveled, or threaded | Per customer drawing |
| Operating Pressure | Up to 4.0 MPa (PN40) depending on dimensions | ASME B31.3 / GB/T 20801 |
| Temperature Range | −196°C to +870°C (SUS316L); up to +1150°C (SUS321) | Material grade dependent |
| Applicable Standards | ASTM A213, ASTM A269, ASME SA-213, GB/T 12771, GB/T 4237, EN 10216-5 | — |
4. Manufacturing Process
The production of high-quality stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous multi-stage process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Inspection: Certified stainless steel strips or seamless tubes are sourced from accredited mills. Incoming materials undergo spectroscopic analysis (OES) to verify chemical composition compliance with specified grades.
- Coil Forming (Bending & Coiling):
- For seamless tube: Continuous cold coiling using CNC-controlled hydraulic bending machines with precise die sets. The bending radius is carefully controlled to prevent wall thinning, ovality distortion, or strain hardening at the coil apex.
- For welded tube: Strip material is first formed into a helical shape, then longitudinally welded using TIG (Tungsten Inert Gas) or orbital welding to create a continuous coil tube with minimal weld distortion.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1050–1150°C followed by rapid water quenching to dissolve carbides, restore full austenitic microstructure, and eliminate residual stresses introduced during forming. This step is critical for ensuring corrosion resistance and ductility.
- Pickling & Passivation: Post-heat-treatment, tubes are immersed in nitric/hydrofluoric acid pickling solutions to remove oxide scales. Subsequently, a passivation treatment (typically 20–30% HNO₃) forms a stable chromium oxide passive film on the surface, enhancing corrosion resistance.
- Precision Sizing & Straightening (if applicable): For applications requiring specific dimensional tolerances, tubes pass through cold sizing passes to achieve final OD and wall thickness within specified tolerances.
- Quality Control & Testing:
- Dimensional inspection (OD, wall thickness, coil diameter, pitch) using laser measurement systems
- Hydrostatic pressure testing per ASTM A213 requirements
- Visual inspection for surface defects, weld integrity, and passivation quality
- Corrosion testing (ASTM A967 passivation verification, ferric sulfate test)
- Optional: hardness testing, tensile testing, and intergranular corrosion testing (ASTM A240)
- Packaging & Marking: Tubes are coiled on protective packaging, wrapped with moisture-barrier materials, and clearly marked with grade, dimensions, heat number, and traceability information.
5. Applications
The coil tube product line from Wenzhou Jixing Metal Materials is designed for a diverse range of demanding thermal and chemical processing applications:
5.1 Solar Thermal Collection Systems (太阳能集热系统)
- EPC (Evacuated Tube Collector) Heat Exchangers: Coil tubes serve as the primary heat transfer element within evacuated glass tubes, absorbing solar radiation and transferring thermal energy to the working fluid (water or heat transfer oil). The helical geometry maximizes absorptive surface area while minimizing thermal stratification losses.
- Parabolic Trough Concentrated Solar Power (CSP): High-temperature coil tubes (SUS321 grade) used as receiver tubes in concentrated solar thermal plants, operating at temperatures up to 400°C with synthetic heat transfer fluids.
- Domestic Hot Water Systems: Immersion coil heat exchangers for solar water heating systems, providing efficient heat transfer between the solar loop and the storage tank water.
5.2 Regenerative Coil Tube Biogas Engineering (回热盘管沼气工程)
- Biogas Upgrading & Purification: Coil tubes used in regenerative heat exchangers for biogas purification processes, where heat recovery from compressed biogas streams preheats incoming raw biogas, improving overall system energy efficiency by 20–35%.
- Anaerobic Digestion Systems: Immersion heating coils for maintaining optimal fermentation temperatures (35–55°C) in anaerobic digesters processing agricultural waste, food waste, or sewage sludge.
- Biogas Engine Preheating: Coil heat exchangers for preheating biogas before engine injection, ensuring consistent combustion performance and reduced emissions.
- Corrosion-Resistant Heat Transfer: The biogas environment contains H₂S (0.5–5.0%), CO₂ (35–55%), and moisture, creating highly corrosive conditions. SUS316L coil tubes provide the necessary corrosion resistance for long-term service life exceeding 15 years.
5.3 Additional Industrial Applications
- Industrial waste heat recovery systems
- Chemical processing heat exchangers (pharmaceutical, food & beverage)
- Refrigeration and HVAC condenser/evaporator coils
- Nuclear power plant secondary loop heat transfer
- Aerospace fuel and hydraulic system tubing
- Medical equipment (MRI cooling circuits, sterilization systems)
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and holds the following certifications and compliance standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European health, safety, and environmental protection standards (EU Pressure Equipment Directive 2014/68/EU)
- ASME Stamp — American Society of Mechanical Engineers certification for pressure-containing equipment
- EN 10204 3.1 — Material Inspection Certificates (Mill Test Reports) provided with every shipment
- GB/T 19001-2016 — Chinese National Standard for Quality Management Systems
- Third-Party Inspection: Available upon request — SGS, BV (Bureau Veritas), or TÜV Rheinland
7. Unique Selling Points
Maximized Thermal Efficiency: The helical coil geometry provides up to 3× greater heat transfer surface area per unit volume compared to straight tubes, resulting in compact, high-performance heat exchangers ideal for space-constrained installations.
Proven Performance in Aggressive Environments: Field-validated in biogas engineering applications with H₂S and CO₂ exposure, demonstrating service life exceeding 15 years without significant corrosion degradation — a testament to the material selection and manufacturing precision.
Renewable Energy Integration: Specifically engineered for solar thermal systems, the coil tube design minimizes thermal losses and maximizes solar energy capture efficiency, contributing to energy self-sufficiency in off-grid and remote installations.
Custom Engineering Capability: Full customization of coil diameter, pitch, tube dimensions, grade selection, and end configurations to match specific system designs and installation constraints — supported by experienced engineering teams.
Full Traceability & Quality Assurance: Every production batch is accompanied by complete mill test reports, chemical analysis certificates, and mechanical property documentation, ensuring full supply chain traceability from raw material to finished product.
8. Technical Consultation & Ordering
For detailed engineering specifications, custom coil tube designs, or project-specific material recommendations, Wenzhou Jixing Metal Materials Co., Ltd provides comprehensive technical support. Engineering drawings, CAD models, and sample testing are available upon request. Minimum order quantities and lead times are negotiable based on project scale and specification complexity.
Document Reference: Product Catalog No. 876 | Classification: Technical Literature & Application Study | Last Revised: 2024