Stainless Steel Coil Tube — HVAC Fan Coil Unit Grade
Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-formed tubular product engineered for critical applications in heating, ventilation, and air conditioning (HVAC) systems, particularly within fan coil units (FCU) deployed in commercial and office building environments. These coil tubes are formed from high-purity austenitic stainless steel wire through advanced cold-drawing and coiling processes, delivering superior thermal conductivity, mechanical integrity, and long-term corrosion resistance under demanding indoor air handling conditions.
As a core heat exchange component, the coil tube serves as the primary medium for transferring thermal energy between circulating refrigerant (or hot water) and ambient air within fan coil units. The coil geometry maximizes surface area within a compact footprint, enabling efficient convective and conductive heat exchange in office buildings, hospitals, hotels, and institutional facilities.
Material & Properties
The coil tube is fabricated from austenitic stainless steel wire conforming to internationally recognized standards, ensuring optimal performance across a wide range of operating temperatures and environmental conditions.
Chemical Composition (Typical, wt%)
| Element | Minimum | Maximum | Element | Minimum | Maximum |
|---|---|---|---|---|---|
| C (Carbon) | — | 0.08 | Mn (Manganese) | — | 2.00 |
| Si (Silicon) | — | 1.00 | N (Nitrogen) | — | 0.10 |
| Cr (Chromium) | 17.00 | 19.00 | Fe (Iron) | Balance | |
| Ni (Nickel) | 8.00 | 11.00 | P (Phosphorus) | — | 0.045 |
| S (Sulfur) | — | 0.030 | — | — | — |
Mechanical Properties
| Property | Specification | Test Method |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ASTM A380 / ISO 6892-1 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ASTM A380 / ISO 6892-1 |
| Elongation (A50mm) | ≥ 40% | ASTM A380 / ISO 6892-1 |
| Hardness (HV10) | ≤ 210 HV | ISO 6507 |
| Thermal Conductivity (25°C) | 16.3 W/(m·K) | ASTM E1225 |
| Operating Temperature Range | −40°C to +200°C | — |
| Corrosion Resistance (Pitting, %Cr_eq) | PREN ≥ 20 | ASTM G48 |
Specifications
| Parameter | Specification | Notes |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) | Order No. 1695 |
| Material Grade | SUS304 / ASTM 304 / EN 1.4301 | Austenitic stainless steel |
| Outer Diameter (OD) | Φ6.0 mm – Φ12.0 mm | Customizable upon request |
| Wall Thickness | 0.4 mm – 1.0 mm | Tolerance ±0.05 mm |
| Coil Pitch (Center-to-Center) | 15 mm – 40 mm | Adjustable per design requirements |
| Coil Length (Developed) | 2.0 m – 15.0 m | Continuous or segmented |
| Surface Finish | Bright Annealed (BA) / Pickled | Ra ≤ 0.8 μm |
| End Treatment | Flared / Grooved / Plain / Threaded | Per application specification |
| Maximum Working Pressure | ≤ 1.6 MPa (hot water) / ≤ 2.5 MPa (refrigerant) | Hydrostatic test at 1.5× working pressure |
| Standard Reference | ASTM A380 / EN 10217-7 / GB/T 14976 | Multinational compliance |
| Packaging | Wooden pallet with protective wrapping | Moisture-proof, anti-collision |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Virgin stainless steel wire (SUS304 grade) is sourced from certified mills, subjected to incoming inspection for chemical composition (via Optical Emission Spectroscopy, OES) and mechanical properties verification.
- Cold Drawing: The wire is drawn through precision tungsten carbide (WC) dies to achieve the target outer diameter and wall thickness with tight dimensional tolerances. This process induces beneficial work hardening and enhances surface finish.
- Intermediate Annealing: Periodic solution annealing at 1050°C – 1100°C in a controlled atmosphere furnace relieves accumulated cold-work stresses, restores ductility, and ensures uniform microstructure prior to further forming.
- Coil Forming (Bending): A computerized CNC coil-forming machine (numerical control) bends the drawn tube into the specified helical coil geometry. The bending process is executed at controlled speeds to prevent wall thinning, ovalization, or micro-cracking. The coil pitch and diameter are maintained within ±0.5 mm tolerance.
- Post-Forming Heat Treatment: Where required, a stress-relief anneal at 600°C – 800°C is performed to eliminate residual bending stresses and ensure dimensional stability during subsequent service.
- Surface Treatment: Bright annealing in a reducing atmosphere (endothermic gas) or chemical pickling and passivation removes scale, oxidation, and contaminants, restoring the full corrosion resistance of the chromium oxide passive layer.
- End Processing: Ends are processed according to application requirements — flared for brazing connections, grooved for mechanical fittings, or threaded for threaded joints.
- Quality Inspection: Each batch undergoes 100% visual inspection, dimensional verification (laser micrometry), hydrostatic pressure testing, and random sampling for chemical and mechanical testing.
- Packaging & Dispatch: Inspected coils are bundled, wrapped in moisture-barrier film, and secured on wooden pallets for export or domestic delivery.
Applications
The Stainless Steel Coil Tube is a versatile component with broad industrial and commercial applications:
- HVAC Fan Coil Units (FCU): Primary heat exchange coils in air handling units (AHU), cassette-type FCUs, concealed ceiling units, and wall-mounted fan coils for office buildings, commercial complexes, and institutional facilities.
- Chilled Water / Hot Water Circulation Systems: Serving as the heat transfer element in central air conditioning water loops, where the coil tube interfaces with chilled water (4°C – 18°C) or hot water (40°C – 80°C) to regulate indoor thermal comfort.
- Refrigeration Systems: Evaporator and condenser coils in commercial refrigeration equipment, cold storage units, and display cases, handling refrigerants such as R-410A, R-32, and R-134a.
- Water Heating Systems: Coil elements in electric and gas water heaters, solar thermal collectors, and industrial process heating applications.
- Food & Pharmaceutical Industry: Hygienic-grade coil tubes in pasteurization equipment, CIP (Clean-in-Place) systems, and pharmaceutical process piping where corrosion resistance and cleanability are paramount.
- Automotive & Marine HVAC: Compact coil assemblies in vehicle air conditioning condensers, marine air conditioning units, and railway carriage climate control systems.
- Building Services Integration: As referenced in the installation methodology for office building fan coil units, these coils are integrated into suspended ceiling systems, ducted distribution networks, and variable refrigerant flow (VRF) terminal units.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management systems and product certifications to assure international market compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and supply chain processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating sustainable manufacturing practices.
- CE Marking (EU Conformity) — Compliance with European directives for pressure equipment (PED 2014/68/EU) and machinery safety.
- EN 10204 3.1 — Material test certificates issued by authorized inspection personnel for each production batch.
- ASTM A380 / ASTM A778 — Compliance with American Society for Testing and Materials (ASTM) standards for stainless steel tubing.
- GB/T 14976 — Chinese national standard compliance for seamless stainless steel tubes used in fluid conveyance.
- EN 10217-7 — European standard for seamless and welded stainless steel tubes for heat exchangers.
- Hydrostatic Pressure Testing — 100% batch testing at 1.5× maximum working pressure with zero-defect acceptance criteria.
- Third-Party Inspection — Optional on-site inspection by SGS, Bureau Veritas, or TÜV for critical project applications.
Unique Selling Points
Exceptional Corrosion Resistance: The SUS304 austenitic matrix, enriched with 17–19% chromium and 8–11% nickel, provides outstanding resistance to pitting, crevice, and atmospheric corrosion — critical for long-term reliability in humid HVAC environments and aggressive refrigerant circuits.
Precision Coil Geometry: CNC-controlled coil forming ensures uniform pitch, consistent diameter, and minimal residual stress, translating to superior heat transfer efficiency and reduced vibration during operation.
Full Traceability: Every coil tube batch is accompanied by mill test certificates (MTC), chemical analysis reports, and dimensional inspection records, providing complete supply chain traceability from raw material to finished product.
Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd offers flexible customization of coil diameter, pitch, length, surface finish, and end treatment to meet specific OEM and project requirements.
Cost-Effective Lifecycle: The combination of corrosion resistance, mechanical durability, and thermal performance yields a total cost of ownership (TCO) significantly lower than carbon steel alternatives requiring periodic replacement or protective coatings.
Installation & Integration Guidance
Based on established methodologies for office building fan coil unit installation, the following best practices are recommended for integrating the stainless steel coil tube into HVAC systems:
- Mounting Configuration: The coil assembly should be installed in a horizontal or inclined orientation within the FCU housing, secured with vibration-dampening mounts to minimize noise transmission through the building structure.
- Connection Method: Brazing (with phosphorus-copper filler rod) is recommended for permanent, leak-free joints between the coil tube and header piping. Mechanical compression fittings are acceptable for field-serviceable connections.
- Insulation: External insulation (closed-cell foam, minimum 25 mm thickness) must be applied to prevent condensation formation and thermal losses on the coil surface.
- Drainage: A condensate drain pan with proper slope (≥ 1:100) must be positioned beneath the coil to manage moisture accumulation during dehumidification cycles.
- Pressure Testing: After installation, the complete circuit must undergo a hydrostatic pressure test at 1.5× design pressure for a minimum hold time of 30 minutes before commissioning.
- Commissioning: Verify airflow rates, temperature differentials, and refrigerant charge (where applicable) against design specifications prior to system handover.
Manufacturer Information
| Item | Details |
|---|---|
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd (温州继兴金属材料有限公司) |
| Product Catalog No. | 1695 |
| Product Classification | Stainless Steel Coil Tube — Literature & Technical Reference |
| Place of Origin | Wenzhou, Zhejiang Province, China |
| Minimum Order Quantity (MOQ) | Negotiable based on specification |
| Lead Time | 15 – 30 calendar days (standard); expedited upon request |
| Warranty | 12 months against manufacturing defects under normal operating conditions |