Stainless Steel Coil Tube — Networked Fan Coil Unit (FCU) System Application
Product Overview
The Stainless Steel Coil Tube (Product No. 936) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubular product designed for integration into Networked Fan Coil Unit (Networked Fan Coil Unit, NFCU) systems and broader HVAC (Heating, Ventilation, and Air Conditioning) infrastructure. This coil tube serves as a critical heat exchanger medium, facilitating efficient thermal transfer between circulating refrigerant and ambient air within modern building climate control systems.
Networked fan coil unit systems represent the next generation of decentralized HVAC architecture, where individual terminal units are interconnected via a centralized control network to optimize energy consumption, zoning control, and operational diagnostics. The coil tube is the thermal core component that directly determines the system's cooling and heating capacity, making its material integrity, dimensional accuracy, and surface finish paramount to overall system performance.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, mechanical strength, and long-term durability under cyclic thermal loading conditions.
- Primary Alloy Grade: SUS304 / AISI 304 (18/8 Stainless Steel), containing a minimum of 18% Chromium (Cr) and 8% Nickel (Ni), providing robust resistance to oxidation and chloride-induced pitting corrosion.
- Alternative Grade Option: SUS316 / AISI 316 (22/10 Stainless Steel), incorporating 2–3% Molybdenum (Mo) for enhanced resistance in aggressive chemical or marine environments.
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C, ensuring efficient heat transfer across the coil surface.
- Operating Temperature Range: −196°C to +870°C (SUS304), accommodating both cryogenic and high-temperature HVAC applications.
- Surface Finish: 2B cold-rolled finish (standard), with optional BA (Bright Annealed) or electropolished surfaces for applications requiring superior hygienic or aesthetic properties.
- Wall Thickness Tolerance: ±10% of nominal thickness, conforming to ASTM A213 / ASTM A269 standards.
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) | — |
| Product No. | 936 | — |
| Outer Diameter (OD) | 6.0 mm – 22.0 mm (customizable) | ASTM A213 / A269 |
| Wall Thickness | 0.3 mm – 1.5 mm | ASTM A269 |
| Coil Diameter (CD) | 300 mm – 1,500 mm | ISO 2852 |
| Tube Length per Coil | Up to 500 m (continuous coil) | — |
| Material Grade | SUS304 / SUS316 / SUS321 | ASTM A213, ASTM A269 |
| Surface Treatment | 2B, BA, Electropolished | — |
| Maximum Operating Pressure | Up to 1.6 MPa (16 bar) | EN 10216-5 |
| Coil Packaging | Wooden pallet with moisture-proof wrapping | ISO 4180 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. | — |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional precision, metallurgical homogeneity, and surface integrity:
- Hot Rolling (HR): Stainless steel slabs are heated to approximately 1,200°C and hot-rolled into seamless tube blanks at controlled reduction rates to achieve uniform grain structure.
- Piercing & Elongation: The hot-rolled billet is pierced using a Mannesmann-style piercing mill, followed by elongation passes to produce the desired outer diameter and wall thickness pre-form.
- Cold Drawing / Cold Pilgering: The pre-formed tube is cold-drawn through precision dies to achieve final dimensional tolerances (±0.05 mm on OD, ±0.01 mm on wall thickness), enhancing surface finish and mechanical properties.
- Solution Annealing: Tubes are annealed at 1,050°C – 1,150°C in a protective atmosphere (argon or vacuum) to relieve residual stresses, restore full austenitic microstructure, and maximize corrosion resistance.
- Pickling & Passivation: Surface oxide scales are removed via acid pickling (HNO₃/HF blend), followed by passivation treatment to form a stable chromium oxide (Cr₂O₃) protective film.
- Coiling: The finished tube is wound onto a precision coil reel at controlled tension to maintain dimensional stability and prevent kinking or ovality.
- Quality Inspection: Each coil undergoes 100% visual inspection, hydrostatic pressure testing (per ASTM A269), dimensional verification via ultrasonic thickness gauging, and spectroscopic chemical analysis (OES).
Applications
The Stainless Steel Coil Tube is deployed across a wide spectrum of industrial and commercial applications, with particular emphasis on networked fan coil unit systems:
- Networked Fan Coil Unit (NFCU) Systems: The coil tube forms the heat exchange core within fan coil units, enabling precise temperature regulation in office buildings, hospitals, hotels, and commercial complexes. In networked configurations, the coil tube's consistent thermal performance ensures reliable data feedback to the Building Management System (BMS), facilitating adaptive control algorithms.
- HVAC Heat Exchangers: Used in evaporator and condenser coils for centralized and decentralized air conditioning systems.
- Refrigeration & Cryogenic Systems: The low-temperature ductility of SUS304 and SUS316 makes the coil tube suitable for ammonia, Freon, and liquid nitrogen heat exchangers.
- Food & Pharmaceutical Processing: Electropolished coil tubes meet FDA and EU 1935/2004 standards for sanitary applications in pasteurization, brewing, and pharmaceutical fluid handling.
- Chemical Processing: SUS316 coil tubes resist aggressive chemical media including acids, alkalis, and chlorinated solutions.
- Marine & Offshore Platforms: Corrosion-resistant coil tubes withstand saltwater spray and humid coastal environments.
- Automotive & Aerospace Thermal Management: Lightweight, high-performance coil tubes for engine cooling, cabin HVAC, and thermal control systems.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that every coil tube product meets international standards:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing quality.
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- ASTM A213 — Standard Specification for Seamless Ferritic, Austenitic, and Ferritic-Austenitic Stainless Steel Tubes for High-Temperature Service.
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tube for Chemical and Similar Severely Corrosive Services.
- EN 10216-5 — European Standard for Technical Delivery Conditions for Tubes for Pressure Purposes — Non-Alloy, Alloyed and Stainless Steel Tubes for General Purposes.
- GB/T 14976 — Chinese National Standard for Cold-Rolled or Cold-Drawn Seamless Stainless Steel Tubes for General Purposes.
- NSF/ANSI 61 — Drinking Water System Components certification (for food-grade and potable water applications).
Unique Selling Points
1. Engineered for Networked Smart HVAC Integration: The dimensional consistency and thermal uniformity of this coil tube enable seamless integration into networked fan coil unit systems, where sensor-embedded control loops demand predictable heat transfer coefficients across the entire coil length. Variations in wall thickness or surface roughness can degrade control accuracy; this product eliminates such variability through precision cold-drawing and 100% ultrasonic inspection.
2. Superior Corrosion Resistance in Diverse Environments: The austenitic microstructure of SUS304/SUS316 provides passive film self-healing capabilities, ensuring decades of service life even in humid, chemically aggressive, or marine environments where carbon steel coils would succumb to rapid degradation.
3. Customizable Coil Geometry: Wenzhou Jixing offers flexible customization of coil diameter, tube OD, wall thickness, and surface finish to match specific OEM (Original Equipment Manufacturer) requirements for fan coil unit assemblies, enabling reduced assembly time and optimized thermal performance.
4. Full Traceability & Documentation: Each coil batch is accompanied by a Mill Test Certificate (MTC) conforming to EN 10204 3.1, including chemical composition analysis, mechanical property data, hydrostatic test results, and heat number traceability — ensuring compliance with stringent procurement and regulatory requirements.
5. Sustainable Manufacturing: The production process incorporates energy-efficient electric arc furnace (EAF) remelting with >85% recycled stainless steel feedstock, aligning with global decarbonization goals and green building certification programs (LEED, BREEAM).