Stainless Steel Coil Tube — Fan Coil Unit Pipeline System Component
Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into fan coil unit (FCU) pipeline systems and wind tunnel detection apparatus. As a critical structural and functional element in HVAC (Heating, Ventilation, and Air Conditioning) thermal exchange systems, the coil tube serves as the primary medium for heat transfer between refrigerant fluids and ambient air streams. The product is engineered to withstand cyclic thermal loading, high-pressure differential conditions, and prolonged exposure to corrosive environments inherent in industrial and commercial air handling installations.
This coil tube product line has been specifically optimized for applications in wind tunnel fan coil detection devices, where precise geometric tolerances, uniform wall thickness, and superior thermal conductivity are paramount for accurate airflow and thermal performance measurement. The design philosophy draws upon advanced pipeline system optimization principles, ensuring minimal pressure drop, maximum heat exchange efficiency, and long-term structural integrity under dynamic operational conditions.
Material Composition & Physical Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal performance. The following materials are available depending on application requirements:
- AISI 304 (UNS S30400) — General-purpose grade offering excellent corrosion resistance in atmospheric and mildly aggressive environments. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- AISI 316 (UNS S31600) — Enhanced corrosion resistance grade with 2–3% Molybdenum (Mo) addition, suitable for chlorinated environments and marine HVAC applications.
- AISI 321 (UNS S32100) — Stabilized grade with Titanium (Ti) addition, recommended for elevated temperature service up to 870°C (1600°F) in industrial wind tunnel testing facilities.
- AISI 316L (UNS S31603) — Low-carbon variant of 316 for improved weldability and resistance to intergranular corrosion in post-welding service conditions.
| Property | Specification / Value | Test Standard |
|---|---|---|
| Density | 7.90 – 8.00 g/cm³ | ASTM E8/E8M |
| Thermal Conductivity (at 20°C) | 14.9 – 16.3 W/(m·K) | ASTM E153 |
| Specific Heat Capacity | 500 J/(kg·K) | ASTM E209 |
| Tensile Strength | 515 – 720 MPa (min.) | ASTM A269 / A270 |
| Yield Strength (0.2% offset) | 205 – 310 MPa (min.) | ASTM A269 / A270 |
| Elongation (at fracture) | ≥ 40% | ASTM A269 / A270 |
| Operating Temperature Range | −196°C to +870°C | — |
| Surface Roughness (Ra) | 0.4 – 1.6 μm (interior) | ASTM B471 |
| Corrosion Resistance (Pitting) | PREN ≥ 19 (316 grade) | ASTM G48 |
Technical Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm – 50.8 mm (¼" – 2") | ± 0.05 mm |
| Wall Thickness | 0.5 mm – 3.0 mm | ± 10% |
| Coil Pitch (Center-to-Center) | 3.0 mm – 15.0 mm (configurable) | ± 0.1 mm |
| Number of Turns | 2 – 50 turns (customizable) | ± 1 turn |
| Tube Length (Uncoiled) | 1.0 m – 50.0 m | ± 2% |
| Coil Diameter | 15 mm – 200 mm | ± 0.5 mm |
| End Finishing | Plain, Flared, Threaded, or Grooved | Per drawing |
| Surface Finish | Bright Annealed (BA), Pickled, or Polished | Ra ≤ 1.6 μm |
| Pressure Rating | Up to 2.5 MPa (working pressure) | Hydrostatic test at 1.5× WP |
| Standard Reference | ASTM A269 / A270 / A511 | — |
Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a rigorous, multi-stage manufacturing process designed to ensure dimensional accuracy, material homogeneity, and surface integrity:
- Raw Material Selection & Verification — Stainless steel strip or seamless tube stock is procured from certified mills and subjected to spectroscopic analysis (optical emission spectrometry) to confirm chemical composition compliance with the specified ASTM grade.
- Cold Drawing & Forming — The tube blank is cold-drawn through precision tungsten carbide (WC) dies to achieve the target outer diameter and wall thickness with minimal work hardening. This step ensures uniform cross-sectional geometry.
- Coil Winding / Bending — Using CNC-controlled rotary bending machinery, the straight tube is precisely wound into the specified coil geometry. The bending process is optimized to prevent ovalization, kinking, or material thinning at bend radii. A minimum bend radius of 3× OD is maintained to preserve structural integrity.
- Welding (if applicable) — For continuous coil configurations, TIG (Tungsten Inert Gas) welding is employed with argon shielding gas to produce full-penetration welds with minimal heat-affected zone (HAZ). Weld bead geometry is inspected for porosity and lack of fusion.
- Heat Treatment & Stress Relief — The formed coil tube undergoes solution annealing at 1050°C – 1150°C followed by controlled cooling to relieve residual stresses from forming operations and restore full austenitic microstructure.
- Pickling & Passivation — A hydrofluoric/nitric acid pickling bath removes oxide scale and welding discoloration. Subsequent passivation treatment forms a stable chromium oxide (Cr₂O₃) protective film on the surface.
- Dimensional Inspection & Non-Destructive Testing (NDT) — Each coil tube is inspected using ultrasonic testing (UT) for wall thickness verification, eddy current testing (ECT) for surface defect detection, and dimensional measurement via coordinate measuring machine (CMM) or laser scanning.
- Hydrostatic Pressure Testing — Every coil tube assembly is pressure-tested at 1.5× the maximum working pressure for a minimum hold time of 15 minutes to verify leak-tightness and structural adequacy.
- Final Quality Assurance & Packaging — Products passing all inspection criteria are cleaned, protected with anti-corrosion packaging, and labeled with traceable heat numbers and lot identification for full supply chain accountability.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd is applicable across a broad spectrum of industrial, commercial, and research domains:
- Wind Tunnel Fan Coil Detection Systems — Primary application for thermal performance validation of fan coil units under controlled aerodynamic conditions. The coil tube serves as the reference heat exchange element in calibration and testing apparatus.
- HVAC Chiller & Condenser Units — Integral components in vapor-compression refrigeration cycles for commercial and industrial air conditioning systems.
- Process Heat Exchangers — Used in chemical processing, food and beverage pasteurization, pharmaceutical clean-room HVAC, and semiconductor manufacturing environments requiring sanitary-grade tubing.
- Marine & Offshore HVAC Systems — 316/316L grade coil tubes provide critical corrosion resistance in salt-laden marine atmospheres and humid offshore platform environments.
- Research & Development Laboratories — Custom coil tube geometries for thermodynamic research, fluid dynamics experimentation, and thermal imaging studies.
- Automotive & Aerospace Thermal Management — Lightweight, high-performance coil tubes for onboard air conditioning units and environmental control systems.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, inspection, and delivery processes.
- ISO 14001:2015 — Environmental Management System ensuring sustainable manufacturing practices and waste minimization.
- ISO/TS 22163 — Special Process Audits for welding and heat treatment operations.
- ASTM A269 / A270 / A511 — Full compliance with American Society for Testing and Materials (ASTM) specifications for stainless steel tubing.
- EN 10217-7 / EN 10216-5 — European standard compliance for welded and seamless stainless steel tubes.
- ASME B31.3 / B31.9 — Pressure piping design and construction code adherence for process and refrigeration service.
- Material Test Reports (MTR) — Each production lot is accompanied by a full material test report documenting chemical composition, mechanical properties, and heat treatment parameters.
Unique Selling Points
- Precision Geometry Optimization — CNC-controlled coil winding ensures repeatable pitch accuracy of ± 0.1 mm, critical for consistent heat transfer performance in detection and calibration applications.
- Superior Surface Finish — Interior surface roughness of Ra ≤ 1.6 μm minimizes fluid friction losses and enhances convective heat transfer coefficients, directly improving system efficiency.
- Full Traceability — Each coil tube carries unique heat and lot identification enabling complete supply chain traceability from raw material mill to end installation.
- Customizable Configurations — Flexible manufacturing capability supports custom OD, wall thickness, coil pitch, turn count, and end-fitting specifications to meet project-specific engineering requirements.
- Extended Service Life — Solution-annealed austenitic microstructure combined with passivated surface finish delivers 2–3× the service life of carbon steel alternatives in corrosive HVAC environments.
- Wind Tunnel Application Expertise — Specialized design knowledge for thermal detection apparatus, ensuring coil tube performance meets the stringent accuracy demands of aerodynamic testing facilities.
Note: All specifications presented herein are based on standard configurations. Custom engineering solutions are available upon submission of detailed technical drawings and performance requirements to Wenzhou Jixing Metal Materials Co., Ltd engineering team. Product performance may vary based on specific application conditions; consult our technical department for application-specific guidance.