Stainless Steel Coil Tube (Coil Tube) — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance Stainless Steel Coil Tubes (also referred to as Coiltube or Coil Pipe) designed for demanding thermal, fluid transport, and heat exchange applications. These products are supplied in continuous coil form, offering significant advantages in installation efficiency, material utilization, and system integration compared to straight-length tubing. The coil configuration enables seamless integration into single-pipe series flow systems, fan coil unit assemblies, and radiator combinations used in modern hydronic heating and cooling infrastructure.
The Coiltube product line is engineered to meet international standards for dimensional accuracy, mechanical integrity, and corrosion resistance, making it suitable for both residential and commercial building services as well as industrial process applications.
2. Material Composition & Properties
The stainless steel coil tubes are fabricated primarily from austenitic stainless steel grades, selected for their superior corrosion resistance, formability, and thermal performance characteristics.
2.1 Common Grades Available
- 304 (AISI 304 / 1.4301) — General-purpose austenitic grade with excellent corrosion resistance and formability; suitable for most hydronic and food-grade applications.
- 316L (AISI 316L / 1.4404) — Enhanced molybdenum content provides superior resistance to pitting and crevice corrosion; ideal for marine and chemical environments.
- 321 (AISI 321 / 1.4541) — Titanium-stabilized grade offering improved resistance to intergranular corrosion at elevated temperatures.
2.2 Key Physical & Mechanical Properties (Grade 304 Reference)
- Density: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Yield Strength: ≥ 205 MPa (annealed condition)
- Tensile Strength: 515–720 MPa
- Elongation: ≥ 40%
- Maximum Service Temperature: 870°C (oxidizing atmosphere)
3. Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 38.1 mm (custom sizes available) | ASTM A269 / EN 10216-5 |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 / EN 10216-5 |
| Coil Length | 100 m – 500 m (standard); up to 1000 m on request | Manufacturer specification |
| Coil Inner Diameter | 150 mm – 500 mm | Manufacturer specification |
| Surface Finish | Mirror polish (Ra ≤ 0.2 μm), electropolished, or No.4 brushed | ASTM A270 / EN 10217 |
| Tolerance on OD | ±0.1 mm (precision) / ±0.3 mm (standard) | ASTM A269 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A269 |
| Heat Treatment Condition | Annealed (Solution Annealed) | ASTM A269 |
| Hydrostatic Test Pressure | ≥ 2.0 MPa (minimum 30 seconds hold) | EN 10216-5 |
| End Condition | Plain ends, beveled, or threaded (on request) | Manufacturer specification |
| Maximum Working Pressure (304, 12 mm OD × 1 mm WT) | ≈ 6.5 MPa at 20°C | Calculated per ASME B31.3 |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage process ensuring consistent quality and dimensional precision:
- Strip Selection & Inspection — Cold-rolled stainless steel strip is sourced from certified mills and subjected to incoming quality inspection including chemical composition verification (OES spectroscopy), surface condition assessment, and mechanical property testing.
- Coil Forming (ERW / Laser Welding) — The strip is precisely formed into a tube shape using either Electric Resistance Welding (ERW) or high-precision laser welding technology. Laser welding is preferred for thinner wall tubes (<1.0 mm) as it produces a narrow Heat-Affected Zone (HAZ) with minimal distortion.
- Pilot Welding & Weld Inspection — Each coil undergoes pilot welding and visual inspection of the weld seam. Non-Destructive Testing (NDT) methods including Eddy Current Testing (ECT) and Ultrasonic Testing (UT) are applied to verify weld integrity throughout the coil length.
- Solution Annealing — Tubes are annealed at 1050–1100°C in a protective atmosphere (hydrogen or vacuum) to relieve residual stresses, restore full austenitic structure, and enhance corrosion resistance. This step is critical for ensuring the material achieves its specified mechanical properties.
- Pickling & Passivation — Following annealing, tubes undergo chemical pickling to remove oxide scale, followed by passivation treatment to form a protective chromium oxide layer on the surface.
- Surface Finishing — Depending on the application, tubes receive mirror polishing, electropolishing, or brushing to achieve the specified surface roughness.
- Coiling & Packaging — The finished tube is coiled onto a steel spool, protected with anti-corrosion wrapping, and packed in export-grade wooden cases or cardboard reels.
5. Applications
Wenzhou Jixing's stainless steel coil tubes serve a diverse range of applications across multiple industries:
5.1 Building Services & HVAC Systems
- Single-Pipe Series Flow Heating Systems — As discussed in the technical literature on heat metering in single-pipe series flow systems, stainless steel coil tubes are integral components in fan coil unit and radiator combinations. The coil configuration allows efficient serpentine routing within compact fan coil housings, optimizing heat transfer surface area while minimizing installation space.
- Fan Coil Unit Heat Exchangers — Coil tubes serve as the primary heat transfer elements in fan coil units, where hot water or chilled water circulates through the coil to condition air streams.
- Radiator Integration — Coil tubes are used in combination with panel radiators and column radiators for combined heating and cooling systems.
- Underfloor Heating Loops — Continuous coil configuration eliminates the need for field welding, reducing leak points and improving system reliability.
5.2 Industrial Applications
- Chemical processing and pharmaceutical piping systems
- Food and beverage processing (sanitary grade 316L)
- Automotive fuel system tubing
- Aerospace hydraulic and pneumatic lines
- Solar thermal collector tubing
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance systems aligned with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System
- CE Marking — Compliance with European Directive requirements
- EN 10204 3.1 — Material test certificates provided with each shipment
- ASTM A269 / A270 — Compliance with American Society for Testing and Materials specifications for seamless and welded austenitic stainless steel tubing
- EN 10216-5 — European standard for welded stainless steel tubes for pressure purposes
- ASME B31.3 — Process piping design compliance
- NSF/ANSI 61 — Drinking water system component certification (for 316L grade)
7. Unique Selling Points
- Seamless Coil Configuration — Continuous tube length eliminates field splices and welds, significantly reducing the risk of system leaks and maintenance requirements.
- Optimized for Fan Coil & Radiator Systems — Coil tubes are specifically engineered for integration into single-pipe series flow heating systems, enabling precise heat metering and improved energy efficiency in combination with fan coil units and radiators.
- Superior Corrosion Resistance — Austenitic stainless steel construction provides exceptional longevity in aggressive hydronic environments, including systems with inhibitors, glycol solutions, and variable water qualities.
- High Thermal Efficiency — The coil geometry maximizes heat exchange surface area per unit volume, enhancing the coefficient of performance (COP) in heating and cooling applications.
- Customizable Specifications — Flexible manufacturing capability accommodates custom outer diameters, wall thicknesses, coil lengths, surface finishes, and end configurations to meet project-specific requirements.
- Full Traceability — Each coil is accompanied by a mill test certificate (MTC) with full chemical and mechanical analysis data, ensuring complete material traceability from raw stock to finished product.
8. Conclusion
Wenzhou Jixing Metal Materials' Stainless Steel Coil Tube product represents a state-of-the-art solution for thermal management systems requiring reliability, efficiency, and long service life. The integration of these coil tubes into single-pipe series flow systems with fan coil and radiator combinations has been demonstrated to improve heat metering accuracy and system energy performance, as supported by academic research in the field of building services engineering.