Stainless Steel Coil Tube (FCU Coiltube) – HVAC Fan Coil Unit Series
Product Overview
The Stainless Steel Coil Tube (Product Catalog No. 805) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping solution specifically designed for Fan Coil Unit (FCU) systems in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications. This product addresses a critical industry challenge—ceiling water leakage (吊顶渗水) in suspended ceiling installations—by providing a corrosion-resistant, structurally robust coil tube that serves as the condensate drainage and heat exchange medium within fan coil unit assemblies.
Unlike conventional carbon steel or copper coil tubes, the stainless steel construction offers superior resistance to corrosion, scale buildup, and microbial growth, making it an ideal retrofit solution for existing FCU systems experiencing persistent moisture-related failures.
Material & Properties
Base Material
- Primary Alloy Grade: AISI 304 / 316L Stainless Steel (UNS S30400 / S31603)
- Alternative Grades Available: AISI 321, 310S, 2205 Duplex, 904L (upon request for high-temperature or marine environments)
- Surface Finish: BA (Bright Annealed), 2B (Cold Rolled), No. 4 Brushed, or Passivated (per ASTM A967)
Mechanical & Physical Properties
- Tensile Strength (UTS): ≥ 520 MPa (AISI 304); ≥ 580 MPa (AISI 316L)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Operating Temperature Range: −196 °C to +450 °C
- Thermal Conductivity: 16.3 W/(m·K) at 20 °C
- Corrosion Resistance: Excellent resistance to pitting (ASTM G48), crevice corrosion, and intergranular corrosion (IGC) per ASTM A240
- Chloride Resistance (316L): Superior to 304 grade; suitable for environments with elevated chloride ion concentrations (e.g., coastal HVAC installations)
Key Unique Selling Points
- Eliminates Ceiling Leakage: The inherent corrosion resistance of stainless steel prevents the micro-perforation and wall-thinning that leads to condensate seepage through ceiling cavities—a failure mode common in carbon steel coil tubes after 3–5 years of service.
- Extended Service Life: 2–3× longer operational lifespan compared to copper or galvanized steel alternatives, reducing lifecycle replacement costs.
- Low Maintenance: Immune to galvanic corrosion when paired with dissimilar metals; no internal scale accumulation requiring periodic chemical flushing.
- Hygienic & Food-Safe: Compliant with FDA 21 CFR 184.1954 and EU 1935/2004, suitable for pharmaceutical cleanrooms, food processing facilities, and healthcare HVAC systems.
- Retrofit Compatibility: Designed with standard dimensioning to allow direct replacement of existing FCU coil tubes without structural modification to the unit housing.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / FCU Coiltube) |
| Catalog No. | 805 |
| Outer Diameter (OD) | φ6 mm, φ8 mm, φ10 mm, φ12 mm (standard); custom upon request |
| Wall Thickness | 0.5 mm – 1.5 mm (standard); 0.3 mm – 2.0 mm (custom) |
| Coil Diameter | φ100 mm – φ300 mm (adjustable per FCU unit design) |
| Tube Length per Coil | 2 m – 12 m (standard); up to 20 m (special order) |
| Number of Rows | 2-row, 3-row, 4-row configurations |
| Fin Material | Aluminum (AL 1100) or Stainless Steel (304) — corrugated or integral |
| Fin Pitch | 1.5 mm – 3.0 mm (adjustable for thermal performance optimization) |
| Maximum Working Pressure | 1.0 MPa (10 bar); 1.6 MPa (16 bar) for reinforced variants |
| Test Pressure | 1.5× working pressure (hydrostatic, per EN 12729) |
| End Connection Type | Flared, threaded (BSP/NPT), socket-weld, or brazed (per ASME B31.9) |
| Applicable Standards | ASTM A269 / A270, EN 10217-7, GB/T 12771, JIS G3446 |
| Applicable Media | Chilled water, hot water, glycol-water mixtures, condensate |
| Operating Temperature | −196 °C to +450 °C |
| Typical Thermal Efficiency (COP contribution) | ≥ 92% heat transfer efficiency (with AL fins, 3-row configuration) |
Manufacturing Process
Process Flow
- Raw Material Procurement: Cold-rolled stainless steel strip (coil) sourced from certified mills (e.g., POSCO, Outokumpu, Taigang), with full chemical composition analysis (ICP-OES) and mechanical property verification per ASTM A240/A270.
- Strip Slitting & Annealing: Coil strip is slit to precise width and annealed at 1050–1100 °C followed by controlled cooling to achieve target grain structure and surface finish (BA or 2B).
- Tube Forming (Cold Drawing / Roll Forming): Formed tubes are produced via cold-drawing (per ASTM A269) or roll-forming (per ASTM A270) processes, ensuring dimensional accuracy of ±0.1 mm on OD and wall thickness.
- Coil Bending: Tubes are bent into the required coil geometry using CNC-controlled coil bending machines. Bend radius is calculated to prevent wall thinning (minimum bend radius ≥ 4× tube OD) and avoid ovality distortion.
- Fin Attachment: Aluminum or stainless steel fins are applied via brazing (for stainless steel fins) or mechanical crimping (for aluminum fins) at the specified fin pitch.
- End Finishing & Connection Fitting: Tube ends are deburred, chamfered, and fitted with the required connection type (flared, threaded, or socket-weld).
- Passivation & Surface Treatment: All stainless steel surfaces undergo acid pickling and passivation per ASTM A967 to remove free iron and restore the protective chromium oxide layer.
- Hydrostatic Pressure Testing: Each coil assembly is pressure-tested at 1.5× maximum working pressure for a minimum of 5 minutes with zero leakage tolerance (per EN 12729 / GB/T 24511).
- Non-Destructive Testing (NDT): Random sample inspection via eddy current testing (ECT) per ASTM E3097 and visual inspection (VT) for surface defects, weld integrity, and dimensional compliance.
- Final Inspection, Packaging & Shipping: Products are inspected, labeled with traceability markings (heat number, batch code, certification reference), and packed in protective corrugated boxes or wooden crates with moisture-absorbing desiccants for export shipping.
Applications
Primary Application Domain: HVAC Fan Coil Unit Systems
The primary application of this stainless steel coil tube is as the heat exchange coil within Fan Coil Units (FCU) installed in commercial buildings, hospitals, hotels, office complexes, and industrial facilities. The product specifically addresses the following application scenarios:
- Ceiling Leakage Prevention: In suspended ceiling (吊顶) installations, where condensate from FCU units drips through ceiling cavities, the stainless steel coil tube's corrosion resistance eliminates the root cause of micro-leakage from tube wall degradation.
- FCU System Retrofit: Replacement of aged or corroded carbon steel / copper coil tubes in existing FCU systems as part of energy efficiency upgrades and maintenance programs.
- Chilled Water / Hot Water Distribution: Serving as the internal coil in both cooling (chilled water, 6–12 °C supply) and heating (hot water, 40–70 °C supply) FCU configurations.
Extended Applications
- Pharmaceutical & Cleanroom HVAC: Hygienic stainless steel coils for ISO 14644 cleanroom environments in pharmaceutical manufacturing, biotechnology labs, and hospital operating rooms.
- Food & Beverage Processing: Condensate management and heat exchange in food processing plants requiring FDA-compliant materials.
- Marine & Coastal HVAC: 316L stainless steel coils for HVAC systems in coastal buildings, offshore platforms, and marine vessels where chloride-induced pitting corrosion is a concern.
- Industrial Process Cooling: Condensers and evaporators in industrial refrigeration, chemical processing, and petrochemical applications requiring high-temperature and high-pressure resistance.
- Water Treatment Systems: Heat exchange coils in water purification and desalination plants.
- Automotive HVAC: Compact coil assemblies for vehicle air conditioning and cabin climate control systems.
Quality Certifications & Standards Compliance
Management System Certifications
- ISO 9001:2015 – Quality Management System (QMS)
- ISO 14001:2015 – Environmental Management System (EMS)
- ISO 45001:2018 – Occupational Health and Safety Management System
- ISO 50001:2018 – Energy Management System
Product & Material Certifications
- EN 10204 Type 3.1 – Material Test Certificate (MTC) with chemical and mechanical test results
- EN 10217-7 – Seamless steel tubes for pressure purposes – Part 7: Technical delivery conditions for austenitic stainless steel tubes
- ASTM A269 / A270 – Seamless and welded austenitic stainless steel tubes
- GB/T 12771 – Chinese national standard for welded stainless steel tubes
- ASME B31.9 – Pressure Piping, Process Piping (for end connection design)
- EN 12729 – Pressure testing of heat exchangers
- FDA 21 CFR 184.1954 – Food contact material compliance (for hygienic applications)
- EU 1935/2004 & EC 1935/2004 – European food contact material regulation
- NORSOK M-650 – Materials and fabrication for offshore production systems (for marine applications)
- SGS / TÜV / Intertek – Third-party inspection and verification available upon request
Testing & Quality Assurance
- Chemical Analysis: ICP-OES (Inductively Coupled Plasma – Optical Emission Spectroscopy) for full elemental composition verification per ASTM E415.
- Mechanical Testing: Tensile testing per ASTM A370; hardness testing per ASTM E18 (Rockwell).
- Dimensional Inspection: Optical comparators and CMM (Coordinate Measuring Machine) for OD, wall thickness, and coil geometry.
- Corrosion Testing: Salt spray testing per ASTM B117 (≥ 1000 hours for 316L grade); pitting resistance per ASTM G48 Method A.
- Intergranular Corrosion (IGC) Testing: Per ASTM A262 Practice No. 1E (Epicut test) to verify proper heat treatment and stabilization.
- Hydrostatic Testing: 100% inspection at 1.5× working pressure with automated leak detection.
- Eddy Current Testing (ECT): Random sample (minimum 10%) per ASTM E3097 for subsurface defect detection.
Technical Note: The stainless steel coil tube (FCU Coiltube, Catalog No. 805) from Wenzhou Jixing Metal Materials Co., Ltd. represents a purpose-engineered solution to the persistent ceiling water leakage problem in commercial HVAC installations. By leveraging the inherent corrosion resistance, hygienic properties, and extended service life of austenitic stainless steel, this product delivers a reliable, low-maintenance heat exchange and condensate management solution that significantly reduces total cost of ownership (TCO) compared to conventional carbon steel or copper coil alternatives. All products are manufactured under a fully traceable quality system with complete documentation from raw material to final delivery, ensuring compliance with international standards and customer specifications.