Stainless Steel Coil Tube (Coiltube) for HVAC & Fan Coil Unit Applications
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered tubular product designed specifically for use in Fan Coil Units (FCU), HVAC (Heating, Ventilation, and Air Conditioning) systems, and automated thermal management assemblies. This product is supplied in continuous coil form, enabling high-efficiency downstream processing through automated coiling, cutting, bending, and brazing operations. The coil tube serves as the primary heat exchange conduit within fan coil unit assemblies, where it facilitates thermal energy transfer between refrigerant or hot/cold water circuits and ambient air.
The design and testing of coil tubes for fan coil unit applications are governed by rigorous automated testing protocols, as documented in industry-standard methodologies such as the "Design of Automated Testing System for Fan Coil Unit" framework. This ensures that every coil tube meets precise dimensional, thermal, and pressure integrity requirements prior to integration into end-use assemblies.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, mechanical strength, and long-term durability under cyclic thermal loading conditions. The following table summarizes the key material properties:
| Property | Specification | Standard / Method |
|---|---|---|
| Base Material | Stainless Steel (AISI 304 / AISI 316 / AISI 321) | ASTM A213 / ASTM A269 |
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.7 mm (1/2") — customizable | ISO 3506 |
| Wall Thickness (WT) | 0.4 mm – 1.0 mm (tolerance ±0.05 mm) | ASTM A213 |
| Thermal Conductivity | 14.2 – 16.3 W/(m·K) at 20°C | ASTM E1225 |
| Tensile Strength (UTS) | ≥ 515 MPa (AISI 304) | ASTM A370 |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ASTM A370 |
| Elongation (at Break) | ≥ 40% | ASTM A370 |
| Operating Temperature Range | −196°C to +870°C (depending on grade) | — |
| Surface Finish | 2B Annealed / BA (Bright Annealed) / Polished (Ra ≤ 0.4 μm) | ASTM A480 |
| Corrosion Resistance | Passive film stability in chloride environments (AISI 316) | ASTM A967 |
| Coil Form | Continuous coil, inner diameter 400 mm – 600 mm | Custom specification |
| Coil Weight | 200 kg – 800 kg per coil (standard) | — |
Specifications
| Parameter | Standard Value | Tolerance |
|---|---|---|
| OD Tolerance | As per customer drawing | ±0.02 mm |
| Wall Thickness Tolerance | As per customer drawing | ±0.05 mm |
| Straightness (per 1000 mm) | — | ≤ 1.5 mm |
| Roundness | — | ≤ 0.05 mm |
| Helix Pitch (Coil) | Uniform winding | ±0.5 mm |
| Hydrostatic Pressure Test | 2.0 × Working Pressure | Hold for 10 s, no leakage |
| Helium Leak Test (optional) | ≤ 1 × 10⁻⁹ Pa·m³/s | — |
| Heat Exchanger Efficiency | ≥ 85% (in FCU assembly) | Per ASHRAE 15 standard |
| Refrigerant Compatibility | R-410A, R-32, R-22, R-134a, Water-Glycol | — |
Manufacturing Process
- Raw Material Selection: Cold-rolled stainless steel strip (AISI 304/316) is procured from certified mills with full mill test certificates (MTC) conforming to ASTM A480 and EN 10204 standards.
- Strip Inspection & Preparation: Incoming strips undergo dimensional verification, surface quality inspection (visual and automated), and chemical composition analysis via Optical Emission Spectroscopy (OES).
- Forming (Roll Forming / Pipe Making): The strip is fed through precision roll-forming stations to create a seamless tubular geometry. Hydraulic or pneumatic pressure-assisted forming ensures uniform wall thickness and minimal residual stress.
- Welding (if applicable): For welded coil tubes, longitudinal seams are joined using TIG (Tungsten Inert Gas) welding with argon shielding gas, achieving a hermetic, penetration-quality weld seam.
- Heat Treatment (Annealing): The formed tube undergoes controlled annealing (typically 1050°C – 1150°C for austenitic grades) followed by quenching to restore ductility, relieve residual stresses, and establish the passive chromium oxide film.
- Pickling & Passivation: Post-annealing oxide scale is removed through acid pickling (nitric/hydrofluoric acid bath), followed by passivation treatment to ensure a stable, protective Cr₂O₃ passive layer.
- Surface Finishing: Tubes are polished or bright-annealed (BA) to achieve the specified surface roughness (Ra ≤ 0.4 μm), critical for minimizing flow resistance and fouling in heat exchanger applications.
- Coiling: The finished tube is wound onto a precision coil former to produce a uniform helical coil with consistent pitch and no kinking or deformation.
- Automated Testing: Each coil tube lot undergoes hydrostatic pressure testing, dimensional measurement (CMM or laser-based), surface defect detection (eddy current or magnetic particle inspection), and, where applicable, helium leak testing — all aligned with the automated testing system design protocols for fan coil unit components.
- Packaging & Dispatch: Coils are wrapped in protective film, sleeved in cardboard or wooden drums, and labeled with batch traceability information for shipment.
Applications
- Fan Coil Units (FCU): Primary heat exchange tubes in residential and commercial fan coil unit assemblies for heating and cooling air distribution.
- HVAC Heat Exchangers: Evaporators and condensers in split-system air conditioners, chiller units, and rooftop packages.
- Automated Testing Systems: Reference and test specimens in automated FCU testing systems, where precise thermal and flow characteristics are critical for calibration and performance verification.
- Refrigeration & Cryogenic Systems: Tubing for refrigerant distribution in commercial refrigeration, cold storage, and industrial process cooling.
- Sanitary & Food-Grade Systems: Hygienic fluid transfer in food and beverage processing, pharmaceutical manufacturing, and dairy equipment (AISI 316L grades).
- Automotive Thermal Management: Cooling system tubing and heat exchanger components in electric and hybrid vehicle thermal management architectures.
Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — certified manufacturing processes |
| ISO 14001:2015 | Environmental Management System |
| CE Marking (EU) | Compliance with European Machinery and Pressure Equipment Directives |
| EN 10204 3.1 | Inspection Certificate — material test reports per European standard |
| ASTM A213 / A269 | Material and product specifications for austenitic stainless steel tubes |
| GB/T 14976 (China) | National standard for seamless stainless steel tubes |
| ASHRAE 15 | Standard for safe use of refrigerants in HVAC systems |
| SGS / BV Third-Party Inspection | Independent verification of dimensional accuracy, chemical composition, and mechanical properties |
Unique Selling Points
- Automated Test-Validated Performance: Coil tubes are validated against automated fan coil unit testing system protocols, ensuring repeatable thermal efficiency and pressure integrity data for every production lot.
- Ultra-Tight Tolerances: OD and wall thickness tolerances of ±0.02 mm and ±0.05 mm respectively, enabling seamless integration into automated brazing and assembly lines without rework.
- Full Traceability: Each coil is assigned a unique batch identifier with complete traceability from raw material mill certificate through final inspection, supporting regulatory compliance and quality audits.
- Customizable Geometries: OD, wall thickness, coil inner diameter, and surface finish are fully customizable to match specific OEM fan coil unit and heat exchanger design requirements.
- Multi-Grade Availability: AISI 304, 316, 321, and 316L grades available to address diverse corrosion environments, from standard HVAC to aggressive chloride and food-grade applications.
Wenzhou Jixing Metal Materials Co., Ltd — A dedicated manufacturer and supplier of precision stainless steel coil tubes, committed to delivering products that meet the highest international standards for HVAC, refrigeration, and industrial heat exchange applications. Our automated testing and quality assurance infrastructure ensures that every coil tube meets the rigorous performance demands of modern fan coil unit and thermal management systems.