Stainless Steel Coil Tube (Coil Tubing) — Fan Coil Unit Integration Grade
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product Code: 1607). Specifically designed for integration into Fan Coil Units (FCUs) and hydronic air-handling systems, this coil tube delivers superior thermal conductivity, corrosion resistance, and mechanical integrity under continuous cyclic thermal loading. The product is supplied in continuous coil form, enabling seamless secondary processing—including coiling, straightening, cutting, and bending—tailored to OEM and ODM requirements for HVAC (Heating, Ventilation, and Air Conditioning) heat exchanger assemblies.
Unlike conventional copper or aluminum tubing, the stainless steel coil tube offers an extended service life in aggressive chemical environments, making it a preferred material for applications involving deionized water, glycol-based heat transfer fluids, and brine solutions. The product has been validated through rigorous field studies documented in industry design literature, including analyses of fan coil unit thermal performance and hydraulic resistance optimization.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, conforming to internationally recognized metallurgical standards. The following table summarizes the key material properties:
- Base Material: Austenitic Stainless Steel (SAE 304 / SAE 316 grade)
- Chemical Composition (SAE 304): Carbon ≤ 0.08%, Chromium 18.0–20.0%, Nickel 8.0–10.5%, Manganese ≤ 2.0%, Silicon ≤ 1.0%, Phosphorus ≤ 0.045%, Sulfur ≤ 0.030%
- Chemical Composition (SAE 316): Carbon ≤ 0.08%, Chromium 16.0–18.0%, Nickel 10.0–14.0%, Molybdenum 2.0–3.0%, Manganese ≤ 2.0%, Silicon ≤ 1.0%
- Thermal Conductivity: 14–16 W/(m·K) at 25°C (significantly higher than carbon steel, enabling efficient heat exchange in FCU applications)
- Density: 7.93 g/cm³ (SAE 304); 8.00 g/cm³ (SAE 316)
- Operating Temperature Range: −196°C to +870°C (SAE 304); −196°C to +870°C (SAE 316)
- Yield Strength: ≥ 205 MPa (annealed condition)
- Tensile Strength: ≥ 515 MPa (annealed condition)
- Elongation: ≥ 40% (minimum, as per ASTM A213)
- Surface Finish: Bright annealed (BA) or pickled and passivated (PP), with surface roughness Ra ≤ 0.8 μm
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, weak acids, alkalis, and chloride-containing environments (SAE 316 grade)
Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | φ6.0 mm – φ25.4 mm (customizable upon request) | GB/T 12771; ASTM A213 |
| Wall Thickness | 0.30 mm – 1.50 mm | GB/T 12771 |
| Coil Inner Diameter | φ500 mm – φ1200 mm | Manufacturer specification |
| Coil Length | Continuous coil, 100 m – 500 m per spool (typical) | Custom order |
| OD Tolerance | ±0.10 mm | GB/T 12771 |
| Wall Thickness Tolerance | ±10% (nominal) | GB/T 12771 |
| Roundness | ≤ 5% of nominal OD | ISO 1128 |
| Surface Defects | No cracks, pitting, rolled-in scale, or excessive oxidation | ASTM A269 |
| Hydrostatic Test Pressure | ≥ 2.0 MPa (performed on sampled lots) | GB/T 12771 |
| Material Grade Options | SAE 304, SAE 316, SAE 316L, SAE 321, SAE 304L | ASTM A213; EN 10216-5 |
| Delivery Condition | Annealed, Bright Annealed (BA), or Solution Annealed | ASTM A213 |
| Maximum Working Pressure | Up to 2.5 MPa (dependent on OD and wall thickness) | Calculated per ASME B31.9 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage process chain, ensuring dimensional accuracy, metallurgical homogeneity, and surface integrity:
- Hot-Rolled Seamless Tube Production: Starting from vacuum-induction melted (VIM) or argon-oxygen decarburization (AOD) steel billets, continuous hot rolling produces seamless pipe blanks with uniform grain structure and minimized inclusion content.
- Piercing & Elongation: The billets are pierced at temperatures of 1,150°C–1,250°C and elongated to the desired outer diameter range using modern piercing mills.
- Intermediate Annealing & Descaling: The hot-rolled tube undergoes controlled annealing to relieve internal stresses, followed by acid pickling (using a mixture of hydrofluoric acid and nitric acid) to remove surface scale and restore the passive chromium oxide layer.
- Cold Drawing (Cold Reduction): The tube is cold-drawn through precision tungsten carbide (WC) dies to achieve the final outer diameter, wall thickness, and roundness specifications. Cold drawing enhances surface finish and mechanical properties.
- Solution Annealing: The cold-drawn tube is annealed at 1,050°C–1,150°C followed by rapid water quenching to dissolve carbide precipitates, restore full austenitic structure, and maximize corrosion resistance and ductility.
- Pickling & Passivation: Post-annealing pickling removes residual scale, followed by passivation treatment to establish a protective chromium oxide film (typically 2–5 nm thick), ensuring long-term corrosion protection.
- Coiling & Packaging: The finished tube is coiled onto precision mandrels, wrapped with protective film, and packed in export-grade steel crates or wooden pallets with moisture-absorbing desiccants to prevent intergranular corrosion during transit.
Applications
The stainless steel coil tube is engineered for a broad spectrum of industrial and commercial applications, with particular emphasis on the following sectors:
- Fan Coil Units (FCUs) & Air Handling Units (AHUs): The primary design application. The coil tube serves as the heat transfer element in evaporator and condenser coils within FCUs, providing efficient latent and sensible heat exchange. Studies referenced in industry design literature confirm that stainless steel coil tubes offer hydraulic efficiency advantages over copper tubing in certain glycol-water mixture configurations, with reduced fouling tendencies.
- Chilled Water & Hot Water Distribution Systems: Used in secondary loop piping for central air conditioning systems, where long-term corrosion resistance eliminates the risk of iron contamination in the water loop.
- Food & Beverage Processing Equipment: Compliant with FDA 21 CFR and EU Regulation 1935/2004 for food-contact applications, including pasteurization heat exchangers, CIP (Clean-in-Place) systems, and process cooling loops.
- Pharmaceutical Manufacturing: SAE 316L grade tubing meets USP Class VI and pharmacopeial standards for sterile processing equipment and cleanroom HVAC systems.
- Chemical Processing & Petrochemical Plants: Resistant to chlorides, sulfuric acid, and caustic solutions, making it suitable for reactor cooling jackets, distillation column condensers, and reflux piping.
- Marine & Offshore Systems: SAE 316 and SAE 316L grades provide excellent resistance to seawater corrosion for shipboard HVAC systems and offshore platform cooling circuits.
- Power Generation: Used in nuclear and thermal power plant condensers, feedwater preheaters, and steam turbine cooling loops.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification covering the full production and supply chain
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- CE Marking — Compliance with European Union Machinery Directive 2006/42/EC and Pressure Equipment Directive 2014/68/EU (PED) for pressure-rated applications
- EN 10204 3.1 — Material test certificates (MTC) issued per lot, providing chemical analysis, mechanical test data, and dimensional verification
- ASTM A213 / A269 — Product testing conforms to American Society for Testing and Materials (ASTM) standards for seamless stainless steel tube
- GB/T 12771 — Chinese National Standard for stainless steel seamless tubes for general applications
- ASME SA-213 — American Society of Mechanical Engineers (ASME) standard for boiler, heat-exchanger, and superheater tubes
- Third-Party Inspection: Available upon request through SGS, Bureau Veritas, or TÜV Rheinland for critical consignments
Unique Selling Points
1. Engineered for Fan Coil Unit Integration: Unlike generic stainless steel tubing, this product is specifically dimensioned and surface-finished for optimal integration into FCU heat exchanger assemblies, minimizing hydraulic resistance and maximizing heat transfer coefficients as validated in industry design literature.
2. Superior Corrosion Resistance in Glycol-Based Fluids: SAE 316/316L grade options provide exceptional resistance to ethylene glycol and propylene glycol heat transfer fluids, eliminating the risk of galvanic corrosion that can occur with copper-aluminum heat exchangers.
3. Continuous Coil Supply for High-Throughput Processing: Delivered in continuous coil form (up to 500 m per spool), the product enables uninterrupted automated cutting, bending, and coil-winding operations, reducing material waste and labor costs for downstream manufacturers.
4. Precision Dimensional Tolerances: Tight tolerances on outer diameter (±0.10 mm) and roundness (≤ 5% of OD) ensure consistent fitment with heat exchanger tube sheets, reducing assembly time and improving overall system reliability.
5. Full Traceability & Documentation: Every production lot is accompanied by EN 10204 3.1 material test certificates, enabling complete supply chain traceability from raw steel mill to end-user installation.
Conclusion
The Stainless Steel Coil Tube (Product Code 1607) from Wenzhou Jixing Metal Materials Co., Ltd. represents a technically advanced, specification-compliant solution for high-performance heat exchanger applications, particularly within the fan coil unit and HVAC sectors. Its combination of metallurgical excellence, dimensional precision, and comprehensive quality documentation positions it as a reliable choice for OEM manufacturers, system integrators, and engineering procurement agents worldwide. For custom specifications, material grade variations, or volume procurement inquiries, direct technical consultation with Wenzhou Jixing Metal Materials Co., Ltd. is recommended.