Stainless Steel Coil Tube (Coiltube) – Fan Coil Unit Series
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled piping component designed for integration into fan coil unit (FCU) systems and HVAC (Heating, Ventilation, and Air Conditioning) applications. This product represents an optimized design solution that addresses critical performance parameters including airflow volume, thermal transfer efficiency, and structural integrity under variable operating conditions.
The coil tube is fabricated from high-grade austenitic stainless steel, ensuring superior corrosion resistance, mechanical durability, and long service life in demanding industrial and commercial environments. The product conforms to rigorous international manufacturing standards and has been validated through comprehensive air volume testing and thermal performance analysis.
2. Material & Properties
The primary material composition of this coil tube product utilizes austenitic stainless steel grades selected for their exceptional balance of corrosion resistance, formability, and high-temperature performance:
- Grade 304 (SAE 304 / UNS S30400): The most widely used austenitic stainless steel, containing approximately 18% Chromium (Cr) and 8% Nickel (Ni), offering excellent general corrosion resistance and weldability.
- Grade 316 (SAE 316 / UNS S31600): Enhanced with 2–3% Molybdenum (Mo), providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- Grade 321 (SAE 321 / UNS S32100): Stabilized with Titanium (Ti) to prevent intergranular corrosion during high-temperature service.
Key material properties include:
- Thermal conductivity: 14–16 W/(m·K) at 20°C
- Linear thermal expansion coefficient: 17.3 × 10⁻⁶ /°C
- Yield strength (minimum): 205 MPa (Grade 304, annealed condition)
- Ultimate tensile strength: 515–720 MPa
- Corrosion resistance: Excellent against atmospheric, aqueous, and chemical environments
- Maximum service temperature: 870°C (oxidation resistance limit)
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 9.52 mm, 12.7 mm, 15.88 mm, 19.05 mm, 22.23 mm, 28.58 mm | ASME B36.19M |
| Wall Thickness (WT) | 0.8 mm – 3.0 mm (customizable) | ASTM A269 / ASTM A270 |
| Coil Pitch | 12 mm – 25 mm (adjustable per design requirement) | Project-specific |
| Number of Rows | 2 rows, 4 rows, 6 rows (standard configurations) | — |
| Tube Length (per circuit) | Up to 4,000 mm | — | Coil Diameter | 300 mm – 600 mm | — |
| Operating Pressure | 1.0 MPa – 1.6 MPa (standard); up to 2.5 MPa (high-pressure) | EN 12828 |
| Operating Temperature Range | -40°C to +180°C (standard); -196°C to +400°C (special grade) | ASME B31.9 |
| Surface Finish | Pickled and passivated (Ra ≤ 0.8 μm); optionally electropolished | ASTM A967 |
| Welding Process | TIG (Tungsten Inert Gas) welding with argon shielding | ASME BPV Section IX |
| Fin Type (if finned) | Hydrophilic aluminum fins; fin density 10 FPI – 14 FPI | — |
| End Connection | Flanged, threaded (BSP/NPT), brazed, or welded | ASME B16.5 / B1.20.1 |
4. Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a meticulously controlled multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and functional performance:
- Raw Material Selection and Inspection: Certified stainless steel strip or seamless tube material is procured from approved mills. Incoming material undergoes spectroscopic analysis (OES), mechanical testing, and visual inspection to verify compliance with ASTM/EN specifications.
- Forming and Coiling: Precision CNC (Computer Numerical Control) coiling machines shape the tube into the specified helical geometry. Coil pitch, diameter, and row count are programmatically controlled to achieve ±0.5 mm dimensional tolerance.
- Welding: TIG welding is performed at coil intersections and header connections using high-purity argon (99.99%) as shielding gas. Weld parameters (current, voltage, travel speed) are optimized to minimize heat-affected zone (HAZ) distortion and prevent sensitization.
- Heat Treatment (if required): Solution annealing at 1010–1120°C followed by rapid water quenching restores full austenitic structure and maximizes corrosion resistance, particularly for Grade 304 and 316.
- Pickling and Passivation: The coil tube assembly is subjected to acid pickling (nitric/hydrofluoric acid blend) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide film (Cr₂O₃).
- Pressure Testing: Hydrostatic pressure testing is conducted at 1.5× the maximum operating pressure for a minimum of 10 minutes to verify leak-tightness and structural soundness.
- Air Volume and Thermal Performance Testing: Following the optimized testing methodology (as referenced in the technical analysis of fan coil unit airflow volume testing), the coil tube assembly is validated in a calibrated wind tunnel environment. Airflow rate (CFM/m³·h), pressure drop (ΔP), and heat transfer coefficient (U-value) are measured at multiple operating points to confirm design compliance.
- Final Inspection and Packaging: Each unit undergoes dimensional verification, surface quality assessment, and documentation review before protective packaging and dispatch.
5. Applications
The stainless steel coil tube is engineered for a broad spectrum of thermal management applications:
- Fan Coil Units (FCU): Primary application as the heat exchange core in commercial and residential HVAC systems, where the coil tube transfers thermal energy between the circulating fluid and the air stream.
- Chilled Water Systems: Cooling coils in central air handling units (AHU) for large-scale commercial buildings, hospitals, and data centers.
- Hot Water Heating Systems: Heating coils for radiant floor systems, underfloor heating, and industrial process heating.
- Industrial Process Cooling: Heat exchangers in chemical processing, food and beverage manufacturing, and pharmaceutical production lines requiring sanitary-grade piping.
- Marine and Offshore Applications: Corrosion-resistant coil assemblies for shipboard HVAC systems and offshore platform utilities where chloride exposure is prevalent.
- Clean Room Environments: Precision temperature and humidity control in semiconductor fabrication, biotechnology laboratories, and pharmaceutical manufacturing facilities.
- Refrigeration and Cryogenic Systems: Low-temperature coil assemblies for cold storage facilities, ice rinks, and industrial refrigeration circuits.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and compliances:
- ISO 9001:2015 – Quality Management Systems (QMS)
- ISO 14001:2015 – Environmental Management Systems (EMS)
- ISO 45001:2018 – Occupational Health and Safety Management
- CE Marking – Conformity with European Union directives (EN 10217-7, EN 10216-5)
- PED 2014/68/EU – Pressure Equipment Directive compliance for pressure-rated coil assemblies
- ASTM A269 / A270 – Seamless and welded stainless steel tubing
- ASME B31.9 – Pressure Piping, Refrigeration and Air-Conditioning
- EN 12828 – Heating systems in buildings – Design requirements
- GB/T 12771 – Chinese national standard for seamless stainless steel tubes
- GB/T 14976 – Chinese national standard for welded stainless steel tubes
7. Unique Selling Points
Optimized Airflow Performance: The coil tube geometry has been refined through advanced computational fluid dynamics (CFD) simulation and validated via rigorous wind tunnel testing, resulting in improved airflow distribution uniformity and reduced pressure drop across the heat exchange core.
Superior Corrosion Resistance: The use of high-purity austenitic stainless steel with full pickling and passivation treatment ensures a service life exceeding 25 years even in aggressive chemical and marine environments.
Customizable Engineering: Flexible configuration options including variable coil pitch, adjustable row count, and multiple end-connection types enable tailored solutions for diverse project requirements.
Full Traceability: Every coil tube assembly is traceable from raw material mill certificate through final test report, ensuring complete supply chain accountability and regulatory compliance.
Integrated Testing Methodology: The manufacturing and quality assurance process incorporates the optimized fan coil unit airflow volume testing protocol, guaranteeing that each delivered product meets or exceeds specified thermal performance criteria.
8. Technical Documentation
Each product shipment is accompanied by the following documentation package:
- Mill Test Certificate (MTC) – EN 10204 Type 3.1
- Weld Procedure Specification (WPS) and Welder Qualification Records (WQR)
- Hydrostatic Pressure Test Report
- Air Volume and Thermal Performance Test Report
- Material Certification (Certificate of Analysis – CoA)
- Non-Destructive Testing (NDT) Report (if applicable – dye penetrant or radiographic inspection)
- Product Data Sheet and Installation Guidelines
For further technical inquiries, custom design consultation, or project-specific specification development, please contact Wenzhou Jixing Metal Materials Co., Ltd directly.