Stainless Steel Coil Tube — HVAC & Thermal Application Series
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered coiled tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for integration into Fan Coil Units (FCUs), air-handling systems, and thermal exchange applications, particularly within high-traffic environments such as metro public areas. The coil tube serves as the primary heat-transfer medium in combined ventilation schemes that integrate Fresh Air Supply (FAS) with Cylindrical Surface Attached Air Distribution (CSAAD), delivering superior thermal regulation and airflow performance in large-scale public infrastructure.
As a critical component in the Fan Coil Unit plus Fresh Air with Cylindrical Surface Attached Air Supply combined scheme, this coil tube enables efficient convective and conductive heat exchange, supporting the demanding requirements of underground transit systems where thermal comfort, air quality, and energy efficiency are paramount.
Material & Properties
The coil tube is fabricated from premium-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability under prolonged operational stress.
- Base Material: Austenitic Stainless Steel (e.g., SUS304 / SUS316 / AISI 304 / AISI 316)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and moisture-induced corrosion, including resistance to chloride-induced pitting in high-humidity metro environments
- Thermal Conductivity: Approximately 14–16 W/(m·K) at 20°C, ensuring efficient heat transfer between the working fluid and surrounding air
- Mechanical Strength: High tensile strength (≥520 MPa) and elongation (≥40%), providing structural integrity under pressure cycling and thermal expansion
- Temperature Range: Operational capability from −196°C to +870°C, accommodating extreme thermal conditions
- Hygienic Surface: Passivated and polished finish with surface roughness Ra ≤ 0.4 μm, preventing biofilm accumulation and facilitating cleaning in public-area HVAC systems
- Non-Magnetic: Fully non-magnetic properties, eliminating interference with sensitive metro instrumentation
- Recyclability: 100% recyclable, aligning with sustainable manufacturing and green infrastructure standards
Specifications
| Parameter | Specification | Unit | Standard / Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 / 8.0 / 10.0 / 12.0 / 16.0 | mm | ASTM A213 / GB/T 14976 |
| Wall Thickness (WT) | 0.5 / 0.6 / 0.8 / 1.0 | mm | ASTM A213 / GB/T 14976 |
| Coil Diameter (CD) | 80 / 100 / 120 / 150 / 200 (customizable) | mm | Custom / OEM |
| Effective Length (EL) | 1,000 – 5,000 (customizable) | mm | Custom / OEM |
| Coil Pitch / Spacing | 15 / 20 / 25 / 30 | mm | ASHRAE 15 / ISO 5189 |
| Number of Rows | 1 – 6 | Rows | Custom / OEM |
| Surface Finish | No. 1 / 2B / BA / Electropolished | — | ASTM A480 |
| Working Pressure | 0.6 – 1.6 | MPa | GB/T 14976 |
| Hydrostatic Test Pressure | 1.5 × Working Pressure (minimum 2.5 MPa) | MPa | ASTM A213 |
| End Form | Plain / Flared / Threaded / Socket Weld | — | ASME B16.18 |
| Welding Method | TIG (GTAW) / Orbital / Resistance | — | ISO 6947 / AWS D10.6 |
| Applicable Fluids | Water / Glycol / Steam / Refrigerant / Condensate | — | — |
| Coating / Treatment | Passivation / Pickling / Anti-Fouling Coating (optional) | — | ASTM A967 |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and thermal performance consistency.
- Raw Material Procurement & Inspection: Cold-rolled stainless steel strip or seamless tubing is sourced from certified mills. Incoming material undergoes spectroscopic analysis (PMI — Positive Material Identification) to verify alloy composition compliance with ASTM/GB specifications.
- Dimensional Cutting & Forming: Precision CNC cutting machines trim tubing to specified lengths. Coil forming is executed using CNC-controlled coiling equipment to achieve exact coil diameter, pitch, and row configuration with tolerance of ±0.5 mm.
- Welding & Joining: Header connections and coil terminations are fabricated using TIG (Tungsten Inert Gas) welding or orbital welding techniques. Weld parameters are optimized to minimize heat-affected zone (HAZ) distortion and preserve corrosion resistance at weld joints.
- Heat Treatment & Stress Relief: Post-weld annealing is performed at 1050–1150°C followed by controlled cooling to relieve residual stresses, restore full annealed microstructure, and ensure uniform mechanical properties throughout the coil assembly.
- Surface Treatment & Passivation: The coil surface undergoes acid pickling and passivation treatment per ASTM A967 to remove scale, oxidation, and contaminants, establishing a protective chromium oxide film that enhances long-term corrosion resistance.
- Quality Inspection & Testing: Each coil tube assembly undergoes comprehensive inspection including:
- Dimensional Inspection: CMM (Coordinate Measuring Machine) verification of OD, WT, coil diameter, pitch, and overall dimensions
- Hydrostatic Pressure Testing: All units tested at 1.5× working pressure for a minimum hold time of 60 seconds to verify leak-tightness
- Visual & Dye Penetrant Inspection (DPI): Weld joints and coil surfaces inspected per ISO 3452-2 for surface defects
- Thermal Performance Testing: Selected units subjected to airflow and heat-transfer rate testing per ASHRAE standards to validate design specifications
- Packaging & Dispatch: Finished coil tubes are individually wrapped in protective film, crated in moisture-resistant packaging, and labeled with material certificates and traceability documentation prior to shipment.
Applications
The Stainless Steel Coil Tube is engineered for versatile deployment across a broad spectrum of thermal and ventilation systems, with particular emphasis on large-scale public infrastructure:
- Metro & Railway Station HVAC Systems: Integration into Fan Coil Units for thermal conditioning of metro public areas, station concourses, and platform zones. The coil tube supports the combined Fan Coil Unit + Fresh Air + Cylindrical Surface Attached Air Supply scheme, delivering uniform temperature distribution and superior air quality in high-occupancy underground environments.
- Commercial Building Air Conditioning: Chilled water and hot water coil assemblies for air handling units (AHUs), rooftop units (RTUs), and packaged terminal air conditioners (PTACs) in commercial and institutional buildings.
- Industrial Heat Exchangers: Process cooling and heating applications in food processing, pharmaceutical manufacturing, and chemical plants where corrosion resistance and hygienic standards are critical.
- Refrigeration & Cold Chain Systems: Evaporator and condenser coils for commercial refrigeration, cold storage facilities, and cold chain logistics equipment.
- Geothermal & Renewable Energy Systems: Heat exchange coils in ground-source heat pump systems and solar thermal collection arrays.
- Marine & Offshore Applications: Corrosion-resistant coil assemblies for shipboard HVAC, offshore platform climate control, and desalination systems.
Unique Selling Points
- Optimized for Metro-Grade Performance: Specifically validated for the combined Fan Coil Unit + Fresh Air + Cylindrical Surface Attached Air Supply scheme in metro public areas, ensuring superior thermal uniformity and air distribution efficiency in large enclosed underground spaces.
- Superior Corrosion Resistance: Stainless steel construction eliminates the risk of internal corrosion and rust contamination that plagues carbon steel coils, extending service life to 20+ years in aggressive metro environments.
- Hygienic & Cleanable Design: Smooth, passivated inner and outer surfaces prevent scale buildup and biofilm formation, reducing maintenance frequency and ensuring consistent thermal performance over the product lifecycle.
- Full Customization Capability: Flexible dimensional configuration (OD, WT, coil diameter, pitch, rows, length) to meet project-specific thermal load calculations and spatial constraints.
- Energy Efficiency: High thermal conductivity and optimized coil geometry minimize pressure drop while maximizing heat transfer coefficient, reducing fan power consumption and overall system energy usage.
- Complete Traceability: Every coil tube assembly is accompanied by full material test certificates (MTC), heat numbers, and inspection records for end-to-end supply chain traceability.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following international and national standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Ensures consistent product quality and customer satisfaction through documented processes |
| ISO 14001:2015 | Environmental Management System — Demonstrates commitment to environmental responsibility and sustainable manufacturing |
| ISO 45001:2018 | Occupational Health & Safety Management System — Ensures safe working conditions and risk mitigation |
| CE Marking | Conformity to European Union health, safety, and environmental protection standards |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High Temperature and High Pressure Boilers, Heat Exchangers, and Similar Applications |
| ASTM A480 | Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plates, Sheets, and Strip for Pressure Vessels |
| ASTM A967 | Standard Practice for Chemical Passivation of Stainless Steel Parts |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport |
| GB/T 12771 | Chinese National Standard for Welded Stainless Steel Tubes for Fluid Transport |
| ASHRAE 15 / 34 | American Society of Heating, Refrigerating and Air-Conditioning Engineers standards for refrigeration safety and HVAC equipment |
| EN 10216-5 | European Standard for Seamless Stainless Steel Tubes for General Purposes — Technical Delivery Conditions |
Each production batch is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 Type 3.1, providing full chemical composition analysis, mechanical property verification, and dimensional compliance documentation. The company's quality assurance program incorporates Statistical Process Control (SPC) and Root Cause Analysis (RCA) methodologies to continuously improve manufacturing consistency and product reliability.