Stainless Steel Coil Tube (Coiltube) for HVAC Fan Coil Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered tubular component specifically designed for integration into Fan Coil Unit (FCU) systems within high-rise building Heating, Ventilation, and Air Conditioning (HVAC) infrastructure. As a critical heat exchange element, the coil tube facilitates efficient thermal transfer between the working fluid (water or refrigerant) and the ambient air stream, thereby delivering superior climate control performance in commercial and residential high-rise environments.
This product represents a specialized segment of stainless steel tubing technology, combining metallurgical excellence with application-specific geometric design to meet the demanding requirements of modern building services engineering.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, mechanical integrity, and thermal stability under continuous cyclic operating conditions. Key material properties include:
- Base Material Grade: SUS304 (UNS S30400) / SUS316L (UNS S31603), conforming to ASTM A213/A269 standards
- Corrosion Resistance: Superior resistance to chlorides, condensation water, and atmospheric pollutants; critical for HVAC environments where moisture and chemical exposure are prevalent
- Thermal Conductivity: Adequate thermal transfer efficiency while maintaining structural integrity at operating temperatures ranging from -40°C to +150°C
- Mechanical Strength: Minimum yield strength of 205 MPa (SUS304) and 170 MPa (SUS316L), ensuring resistance to pressure cycling and mechanical vibration
- Weldability: Excellent cold-forming and welding characteristics, enabling seamless coil formation without material degradation
- Hygienic Surface Finish: Low carbon (LC) variants available to prevent intergranular corrosion and ensure long-term service life
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Item No. | 283 |
| Tube Outer Diameter (OD) | 6.35 mm (1/4") / 9.53 mm (3/8") / 12.7 mm (1/2") — customizable |
| Wall Thickness | 0.5 mm – 1.5 mm (customizable per application) |
| Coil Pitch (Spiral Spacing) | 6 mm – 15 mm (optimized for airflow resistance and heat exchange efficiency) |
| Coil Diameter (Bundled) | Standard bundles ranging from 150 mm to 600 mm |
| Available Lengths | Custom-cut to specification; standard coils up to 50 meters |
| Material Grade | SUS304 / SUS316L / SUS321 |
| Surface Finish | BA (Bright Annealed) / No.4 Brushed / Mirror Polish |
| Operating Pressure | Up to 1.6 MPa (gauge) standard; 2.5 MPa available on request |
| Operating Temperature | -40°C to +150°C |
| Tolerance (OD) | ±0.05 mm (precision grade) |
| Tolerance (Wall Thickness) | ±10% |
| Standard Conformity | ASTM A213 / A269, GB/T 12771, EN 10217 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical homogeneity, and surface quality:
- Raw Material Selection & Inspection: Virgin stainless steel strip or seamless tube stock sourced from certified mills, subjected to spectroscopic analysis for chemical composition verification.
- Cold Drawing / Seamless Forming: Tube blanks are cold-drawn through precision dies to achieve target outer diameter and wall thickness with tight tolerances.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1050°C – 1100°C followed by controlled water quenching to achieve a fully austenitic microstructure, eliminating residual stresses and ensuring maximum corrosion resistance.
- Spiral Coiling / Finning: Tubes are precision-bent into helical coil configurations using CNC-controlled coiling equipment. Where applicable, aluminum or copper fins are mechanically attached to enhance heat transfer surface area.
- Welding & Brazing: Header connections and end caps are TIG-welded (Gas Tungsten Arc Welding) under inert gas shielding to prevent oxidation. Brazed joints are inspected for void-free penetration.
- Hydrostatic Pressure Testing: Each coil assembly undergoes hydrostatic testing at 1.5× the maximum operating pressure to verify leak-tightness and structural integrity.
- Surface Finishing & Cleaning: Final passivation treatment (citric acid or nitric acid based) removes scale and contaminants, forming a stable chromium oxide protective layer.
- Final Quality Inspection: Dimensional verification, visual inspection, and non-destructive testing (eddy current or dye penetrant) prior to packaging.
Applications
The stainless steel coil tube is a foundational component in the following engineering domains:
- Fan Coil Unit (FCU) Systems: Primary heat exchange element in direct-expansion and hydronic fan coil units installed in high-rise office buildings, hotels, and residential towers. The coil tube efficiently transfers thermal energy between circulating water/refrigerant and the airstream drawn across the coil face by the integrated fan.
- VAV (Variable Air Volume) Systems: Integrated into VAV terminal units where precise modulation of cooling and heating capacity is required for zone-level climate control in large commercial spaces.
- Chilled Water Systems: Serves as the heat exchange medium in chilled water coils, where water at 6°C – 12°C absorbs heat from the building interior air.
- Hospital & Cleanroom HVAC: The hygienic surface finish and corrosion resistance of SUS316L grade make these coil tubes ideal for pharmaceutical, laboratory, and healthcare facility ventilation systems where bacterial growth and contamination must be prevented.
- Marine & Coastal HVAC: SUS316L variants provide enhanced chloride resistance for HVAC installations in coastal high-rise structures exposed to salt-laden atmospheres.
- Industrial Process Cooling: Adapted for heat recovery and process cooling applications in food processing, chemical manufacturing, and electronics fabrication facilities.
Performance Optimization in High-Rise Building HVAC Systems
Based on applied research into fan coil system performance optimization for high-rise ventilation and air conditioning, the following engineering considerations are integral to the design and deployment of this product:
- Hydronic Balance: Coil tube geometry is optimized to minimize pressure drop while maximizing heat transfer coefficient, contributing to overall system energy efficiency and reducing pumping power consumption.
- Stratification Mitigation: In tall building risers, coil tube performance is evaluated under varying static pressure conditions to ensure consistent thermal output across all floors.
- Condensation Management: Surface finish and material selection minimize condensation formation on coil surfaces, reducing microbial growth risk and improving indoor air quality (IAQ).
- Energy Efficiency: Enhanced fin-to-tube contact resistance and optimized coil pitch contribute to improved COP (Coefficient of Performance) for the overall HVAC system.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework, with certifications and compliance including:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — European Conformity for pressure equipment and HVAC components
- ASTM F903 — Certified for plumbing and fluid systems
- EN 10204 3.1 — Material inspection certificates provided per batch
- SGS / Bureau Veritas — Third-party testing and verification reports available
- RoHS & REACH Compliance — Restriction of Hazardous Substances and chemical registration compliance
- Mill Test Reports (MTR) — Provided with every shipment, documenting chemical composition, mechanical properties, and heat treatment history
Unique Selling Points
1. Application-Specific Engineering: Unlike generic stainless steel tubing, this coil tube product is purpose-engineered for HVAC fan coil integration, with geometry, surface finish, and material grade selected through rigorous thermal-hydraulic analysis.
2. Superior Corrosion Longevity: The use of low-carbon austenitic stainless steel (SUS304/SUS316L) ensures service life exceeding 25 years even in aggressive condensation and humid environments, significantly outperforming carbon steel alternatives.
3. Precision Coiling Technology: CNC-controlled coiling ensures uniform pitch and concentricity, critical for balanced airflow distribution and optimal heat exchange efficiency in fan coil units.
4. Customization Capability: Flexible manufacturing allows customization of tube dimensions, coil geometry, material grade, and surface finish to match specific OEM or project requirements.
5. Full Traceability: Every coil tube batch is fully traceable from raw material mill certificate through final inspection, providing complete supply chain accountability for critical infrastructure applications.
Technical Summary
The Stainless Steel Coil Tube (Coiltube) by Wenzhou Jixing Metal Materials Co., Ltd represents a high-performance, reliability-oriented solution for heat exchange applications in modern HVAC systems. Its metallurgical integrity, precision manufacturing, and application-specific design make it an indispensable component in the thermal management infrastructure of high-rise commercial and residential buildings. The product aligns with international standards and quality frameworks, ensuring seamless integration into global construction and engineering projects.