Stainless Steel Coil Tube (Coiltube) — HVAC & Process Cooling Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product designed for high-performance thermal exchange applications. Supplied in continuous coil form, this product is specifically tailored for use in Fan Coil Unit (FCU) air conditioning systems, fresh air handling units, and process cooling circuits where corrosion resistance, thermal conductivity, and long-term structural integrity are paramount. The coil configuration facilitates downstream forming, bending, and heat exchanger assembly operations without the need for welding seams at coil joints, thereby minimizing potential leak points and enhancing system reliability.
Material & Properties
The Coil Tube is fabricated from austenitic stainless steel grades conforming to international standards, ensuring superior mechanical and chemical performance across a wide range of operating environments.
- Primary Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), and AISI 321 (UNS S32100)
- Equivalent Standards: EN 1.4301 (304), EN 1.4401 (316), GB/T 30408 (Chinese National Standard for stainless steel seamless tubes)
- Surface Finish: 2B cold-rolled finish or electropolished (Ra ≤ 0.4 μm) for hygienic applications
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, acidic condensate, and chlorinated water environments (particularly Grade 316)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer performance
- Operating Temperature Range: −196°C to +870°C (continuous service)
- Magnetic Properties: Non-magnetic or weakly magnetic (≤ 3.5 Gs)
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.00 mm – 50.80 mm (¼" – 2", ±0.15 mm tolerance) |
| Wall Thickness | 0.50 mm – 3.00 mm (±10% tolerance) |
| Coil Length | Standard: 50 m – 300 m per coil; Custom lengths available upon request |
| Coil Inner Diameter | 300 mm – 1200 mm (configurable based on packaging and handling requirements) |
| Tolerance Class | EN 10216-5 / ASTM A269 — Precision drawn |
| End Condition | Plain cut, or custom (flared, beveled, threaded, or press-fit prepared) |
| Heat Treatment | Solution annealed (1050–1150°C), followed by water quenching |
| Maximum Working Pressure | Up to 1.6 MPa (PN16) at 20°C; derated at elevated temperatures |
| Minimum Bend Radius | 1.5 × OD (cold bending without cracking) |
| Packaging | Wooden pallet with VCI (Volatile Corrosion Inhibitor) paper wrapping and steel banding |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical quality, and surface integrity:
- Raw Material Procurement: High-purity stainless steel billets or wire rod sourced from certified mills (e.g., Outokumpu, POSCO, Taiyuan Stainless Steel) with full mill test certificates (MTC/EN 10204 3.1).
- Piercing & Hot Rolling: Billets are heated to 1200–1250°C and pierced to form seamless hollow tubes, eliminating weld seams and ensuring uniform microstructure.
- Hot Finishing & Pickling: Tubes are acid-pickled in mixed HNO₃/HF solutions to remove oxide scale, followed by descaling and neutralization.
- Cold Drawing / Cold Pilgering: Tubes are drawn through precision tungsten carbide dies to achieve final dimensions within ±0.1 mm tolerance, improving surface finish and mechanical properties.
- Solution Annealing: Tubes are heated to 1050–1150°C in a controlled atmosphere furnace and rapidly quenched to restore full austenitic structure, relieve residual stresses, and maximize corrosion resistance.
- Coiling & Inspection: Finished tubes are coiled on precision winding equipment, followed by 100% ultrasonic testing (UT), eddy current testing (ECT), and dimensional verification.
- Surface Treatment (Optional): Electropolishing or passivation (citric acid or nitric acid based) for enhanced surface cleanliness and passivation layer integrity.
Applications
The Stainless Steel Coil Tube is engineered for demanding thermal management and fluid transport applications, including but not limited to:
- Fan Coil Unit (FCU) Systems: Primary tubing for cold water and hot water circuits in commercial HVAC (Heating, Ventilation, and Air Conditioning) installations, where condensate corrosion resistance is critical.
- Fresh Air Handling Units (AHU): Coil tube for pre-cooling and dehumidification sections in ventilation systems serving cleanrooms, hospitals, and pharmaceutical facilities.
- Plate & Shell Heat Exchangers: Bifilar or spiral wound configurations for compact heat exchange in refrigeration and process cooling.
- Food & Beverage Processing: Sanitary-grade tubing for CIP (Clean-In-Place) compatible cooling circuits in dairy, brewery, and beverage production lines.
- Pharmaceutical & Biotech: GMP (Good Manufacturing Practice) compliant tubing for cleanroom HVAC and process fluid distribution.
- Marine & Offshore: Saltwater-resistant coil tubing (Grade 316L) for shipboard HVAC and bilge cooling systems.
- Solar Thermal & Heat Pump Systems: Coil tubing for closed-loop geothermal and air-source heat pump applications.
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 Systems certification
- ISO 14001:2015 — Environmental Management Systems certification
- EN 10216-5 — Technical delivery conditions for seamless and welded stainless steel tubes for technical purposes
- ASTM A269 / A213 — Standard specification for austenitic stainless steel tubing
- GB/T 30408 — Chinese National Standard for seamless stainless steel tubes
- NSF/ANSI 61 — Drinking water system components (for food-grade applications)
- CE Marking — Compliance with European directives for machinery and pressure equipment
Unique Selling Points
Seamless Coil Configuration: Unlike welded tube-in-coil products, the seamless coil tube eliminates the risk of weld-induced corrosion initiation points, providing a significantly longer service life in aggressive HVAC condensate environments.
Optimized for Fan Coil Unit Commissioning: The dimensional precision and consistent wall thickness of this coil tube directly support reliable thermal performance in fan coil unit air conditioning systems, reducing commissioning iterations and ensuring design heat transfer coefficients are achieved.
Multi-Grade Availability: Single-source procurement of Grades 304, 316, and 321 enables system designers to select the optimal alloy for specific corrosion and temperature requirements without switching suppliers.
Full Traceability: Each coil is accompanied by a complete Mill Test Certificate (MTC) with heat number traceability, chemical composition analysis, and mechanical test results per EN 10204 Type 3.1.