Stainless Steel Coil Tube for Floating Coil & U-Tube Heat Exchangers
Product Overview
The Stainless Steel Coil Tube (Model Reference: JX-985) is a precision-engineered continuous coil-form tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coil tube is specifically designed for integration into Floating Coil Heat Exchangers (FCHX) and U-Tube Heat Exchangers (UTHE), serving as the primary heat transfer element in building hot water systems, district heating networks, and industrial process heating applications.
Unlike conventional straight pipe configurations, the coil tube geometry provides an exceptionally high surface-area-to-volume ratio, enabling superior thermal efficiency within compact installation envelopes. The continuous coiled form factor eliminates the need for external bending operations at the installation site, reducing labor costs and minimizing potential leak points at joints or welds.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, ensuring long-term resistance to corrosion, scaling, and thermal fatigue under continuous hot water service conditions.
- Primary Material Grades: SUS304 (ASTM A270 TP304), SUS316L (ASTM A270 TP316L), and SUS321 (ASTM A270 TP321)
- Corrosion Resistance: Exceptional resistance to chloride-induced pitting (316L grade), intergranular corrosion (321 grade), and general atmospheric corrosion (304 grade)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer performance
- Operating Temperature Range: -196°C to +870°C (depending on grade selection)
- Maximum Operating Pressure: Up to 1.6 MPa (standard), configurable up to 4.0 MPa for high-pressure applications
- Hygienic Surface Finish: Available in Ra ≤ 0.4 μm electropolished finish for sanitary applications
- Mechanical Properties (SUS304): Tensile Strength ≥ 520 MPa; Yield Strength ≥ 205 MPa; Elongation ≥ 40%
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 19 mm (custom sizes available) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Pitch (Helix Diameter) | 100 mm – 500 mm (configurable per application) |
| Coil Length per Spool | 10 m – 100 m (continuous coil) |
| Material Grade | SUS304 / SUS316L / SUS321 |
| Surface Finish | Mirror Polish (Ra ≤ 0.25 μm) / Electropolished (Ra ≤ 0.4 μm) / Industrial Passivated |
| End Connection Type | Flanged / Threaded / Socket Weld / Clamp Connection |
| Standard Compliance | ASTM A270 / EN 10217-7 / GB/T 12771 |
| Heat Exchanger Configuration | Floating Coil (immersed) / U-Tube Bundle |
| Applicable Fluids | Domestic Hot Water (DHW), District Heating Water, Steam, Glycol Solutions |
| Design Life | ≥ 25 years under normal operating conditions |
Manufacturing Process
The production of the JX-985 Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection & Inspection: Certified stainless steel strip or seamless tubing stock is procured and subjected to spectroscopic analysis (PMI) to verify chemical composition compliance with the specified grade.
- Coil Forming (Cold Bending): Precision CNC-controlled coil forming machines bend the straight tubing into the required helical geometry at controlled strain rates to prevent work hardening, cracking, or ovality distortion.
- Heat Treatment & Stress Relief: Post-forming annealing at 1050°C–1150°C (solution treatment) restores the austenitic microstructure, eliminates residual stresses, and ensures uniform mechanical properties throughout the coil.
- Pickling & Passivation: The formed coil is treated with nitric/hydrofluoric acid pickling solution followed by passivation to remove oxide scale and establish a protective chromium oxide layer.
- Surface Finishing: Electropolishing or mechanical polishing is applied to achieve the specified surface roughness (Ra) for optimal hydraulic performance and hygiene compliance.
- Dimensional Inspection & Testing: Each coil is verified for OD tolerance (±0.05 mm), wall thickness uniformity, coil pitch consistency, and overall length. Hydrostatic pressure testing is conducted at 1.5× the maximum operating pressure.
- Packaging & Dispatch: Coils are wrapped in protective film, secured on wooden reels or pallets, and labeled with full traceability documentation including heat numbers and test certificates.
Applications
The JX-985 Coil Tube finds extensive application across multiple sectors where efficient, compact, and reliable hot water generation is critical:
- Building Hot Water Supply Systems: Floating coil heat exchangers immersed in thermal storage tanks for domestic hot water (DHW) preparation in residential complexes, hotels, hospitals, and commercial buildings.
- District Heating Networks: U-tube heat exchanger bundles for substation heat recovery from district heating primary loops to secondary building loops.
- Industrial Process Heating: Coil-type heat exchangers for process water preheating, glycol loop heating, and thermal oil systems in food processing, pharmaceutical manufacturing, and chemical industries.
- Renewable Energy Integration: Immersed coil heat exchangers for solar thermal water heating systems, ground-source heat pump integration, and biomass boiler heat recovery.
- Marine & Offshore Applications: U-tube heat exchangers for shipboard hot water generation utilizing seawater as a heat source or sink.
Quality Certifications & Standards Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- CE Marking — Conformity with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU)
- ASTM A270 / A269 — Standard Specification for Stainless Steel Seamless and Welded Tubing
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubing
- EN 10217-7 — European Standard for Heat Exchanger Tubes
- NSF/ANSI 61 — Drinking Water System Components (available upon request)
- Full Traceability: Each coil is accompanied by a Mill Test Certificate (MTC), Hydrostatic Test Report, and Dimensional Inspection Record
Unique Selling Points
- Superior Thermal Performance: The helical coil geometry enhances turbulent flow within the tube, achieving up to 30% higher heat transfer coefficients compared to straight-tube equivalents of the same volume.
- Compact Footprint: Floating coil configurations allow high-capacity heat exchange within existing tank volumes, eliminating the need for external heat exchanger units and associated pipework.
- Maintenance-Free Operation: The floating design allows thermal expansion of the coil without imposing mechanical stress on tank walls or connection points, resulting in a maintenance-free operational lifespan exceeding 25 years.
- Custom Engineering: Wenzhou Jixing Metal Materials Co., Ltd offers fully customizable coil geometry, material grade selection, and end-connection configurations to match specific project requirements.
- Hygienic Construction: Available with electropolished interior surfaces (Ra ≤ 0.4 μm) compliant with FDA and 3-A sanitary standards for food and pharmaceutical applications.
- Energy Efficiency: The high surface-area-to-volume ratio minimizes the temperature differential required for effective heat transfer, reducing overall system energy consumption and operational costs.