Stainless Steel Coil Tube for Dry Coil Air Conditioning Systems
Product Overview
The stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for integration into dry coil air conditioning systems (Dry Coil Air Conditioning System). These coil tubes serve as the core heat exchange medium in fresh air treatment units, where they facilitate latent heat removal from incoming outdoor air without inducing condensation on the coil surface. This unique operational characteristic distinguishes dry coil systems from conventional evaporative coils, enabling superior indoor air quality control and energy efficiency.
As a coiled (coiltube) product, the stainless steel tubing is supplied in continuous coil form, allowing for seamless integration into custom heat exchanger assemblies. The product is classified under technical literature study references (Document No. 469) and has been extensively evaluated for its performance in fresh air handling processes within commercial office building HVAC applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability in HVAC environments.
- Primary Alloy Grade: SUS304 / ASTM A269 TP304 (18/8 Stainless Steel — 18% Chromium, 8% Nickel)
- Alternative Grade: SUS316L / ASTM A269 TP316L (for enhanced chloride resistance in coastal or humid environments)
- Corrosion Resistance: Superior resistance to oxidation, condensation-induced pitting, and chemical degradation from refrigerant fluids
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C, providing efficient heat transfer between the refrigerant and the air stream
- Mechanical Strength: Yield strength ≥ 205 MPa; Tensile strength ≥ 520 MPa
- Operating Temperature Range: -40°C to +150°C
- Surface Finish: Pickled and passivated (2B finish) or electropolished for enhanced corrosion resistance and reduced friction
- Hygienic Compliance: Suitable for potable water contact and food-grade applications per FDA and EHEDG standards
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Type | Stainless Steel Coil Tube (Coiltube) | — |
| Outer Diameter (OD) | 6.0 mm / 8.0 mm / 9.5 mm / 12.0 mm (customizable) | ASTM A269 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 1.5 mm (tolerance ±10%) | ASTM A269 |
| Coil Length (Continuous) | 50 m – 500 m per coil (configurable) | — |
| Coil Diameter | 300 mm – 1000 mm (shipping coil) | — |
| Material Grade | SUS304 / SUS316L / SUS321 | ASTM A269 / GB/T 12771 |
| Surface Treatment | Pickled & Passivated / Electropolished | ISO 15530 |
| Heat Treatment | Solution Annealed (1050°C – 1150°C, water quenched) | ASTM A269 |
| Pressure Rating | Up to 2.5 MPa (design pressure, depends on OD and wall thickness) | ASME B31.5 |
| Welding Compatibility | TIG (GTAW), Laser, Orbital — fully weldable without preheating | ASME Section IX |
| Formability | Excellent cold-working capability; suitable for bending, flaring, and expansion | — |
| Application Focus | Dry Coil Fresh Air Treatment Units | ASHRAE 90.1 / GB 50736 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. | — |
Manufacturing Process
3.1 Raw Material Selection
High-purity stainless steel strip (cold-rolled coil) is sourced from certified mills and subjected to incoming inspection for chemical composition verification via Optical Emission Spectrometry (OES) and Positive Material Identification (PMI). The strip is confirmed to meet ASTM A269 or equivalent Chinese national standard (GB/T 12771) requirements for chemical composition and mechanical properties.
3.2 Cold Forming and Seaming
The flat strip is fed through a series of progressive forming rollers that progressively curve the material into a tubular cross-section. The edges are overlapped and mechanically formed into a tight longitudinal seam. This process is performed at ambient temperature to preserve the material's cold-worked mechanical properties.
3.3 Seamless Tube Production (Alternative)
For applications requiring seamless construction, the stainless steel is processed through a pilot mill or Mannesmann piercing process, followed by cold drawing over a mandrel to achieve the final dimensions and tolerances. This eliminates the longitudinal seam entirely, providing uniform wall thickness and superior pressure integrity.
3.4 Heat Treatment (Solution Annealing)
The formed tube is heated to 1050°C–1150°C in a controlled atmosphere furnace to dissolve carbide precipitates and restore full austenitic structure. Rapid water quenching follows to lock in the solution-treated microstructure, ensuring maximum corrosion resistance and ductility.
3.5 Surface Finishing
The annealed tube undergoes pickling (acid immersion to remove oxide scale) and passivation (nitric or citric acid treatment to form a protective chromium oxide layer). Electropolishing may be applied for critical applications requiring ultra-smooth internal surfaces (Ra ≤ 0.4 μm) to minimize fluid friction and prevent biofilm accumulation.
3.6 Coil Winding and Packaging
The finished tube is wound into continuous coils on precision-controlled winder equipment. Each coil is wrapped in protective film, placed in wooden or steel shipping crates, and labeled with material certification documentation.
3.7 Quality Control
- Dimensional Inspection: Automated OD and wall thickness gauging at intervals of ≤ 10 m
- Hydrostatic Testing: 100% pressure testing at 1.5× design pressure for minimum 30 seconds
- Non-Destructive Testing (NDT): Eddy current inspection for seam integrity and internal defect detection
- Chemical Analysis: Spectrometric verification of alloy composition per heat lot
- Mechanical Testing: Tensile and hardness testing per ASTM A269 requirements
Applications
3.1 Dry Coil Air Conditioning Systems
The primary application of this stainless steel coil tube is in dry coil heat exchangers used within fresh air treatment systems. In these systems, the coil tube operates at a temperature slightly above the dew point of the incoming air, enabling the removal of moisture (latent heat) without forming condensate on the tube surface. This eliminates the need for condensate drainage and prevents microbial growth associated with standing water.
3.2 Commercial Building HVAC Systems
As documented in technical literature concerning office building ventilation systems, these coil tubes are integral components of:
- Fresh air handling units (Fresh Air Handling Units, FAHU)
- Variable Air Volume (VAV) systems with dedicated outdoor air systems (DOAS)
- Dehumidification units for data centers and laboratories
- Heat recovery ventilation systems (Heat Recovery Ventilation, HRV)
3.3 Additional Applications
- Refrigeration and air conditioning heat exchangers
- Chilled water piping systems
- Food and beverage processing equipment
- Pharmaceutical and biotechnology cleanroom systems
- Marine and offshore HVAC installations (with SUS316L grade)
- Geothermal heating and cooling systems
Quality Certifications
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Manufacturing and supply processes |
| ISO 14001:2015 | Environmental Management System — Sustainable production practices |
| ASTM A269 | Standard Specification for Seamless and Wrought Stainless Steel Tube, Pipe, and Fittings |
| GB/T 12771 | Chinese National Standard — Stainless Steel Seamless Tubes for Fluid Conveyance |
| ASME B31.5 | Pressure Piping — Process Piping design and fabrication code |
| EN 10217-7 | European Standard — Heat Exchangers, Components and Accessories |
| CE Marking | European Conformity — Product compliance with EU directives |
| Mill Test Certificate (MTC) | EN 10204 Type 3.1 — Third-party verified material certification per heat number |
| RoHS / REACH | Restriction of Hazardous Substances and Registration, Evaluation, Authorization and Restriction of Chemicals compliance |
Unique Selling Points
1. Dry Coil Optimization: Specifically engineered for operation above the dew point, enabling latent heat removal without condensation — a critical advantage for maintaining indoor air quality (IAQ) and reducing energy consumption in commercial HVAC systems.
2. Corrosion-Free Longevity: The austenitic stainless steel construction provides a service life exceeding 25 years in HVAC applications, eliminating the corrosion-related failures common with carbon steel alternatives.
3. Continuous Coil Supply: Available in continuous coil lengths up to 500 meters, minimizing joints and weld points in heat exchanger fabrication, thereby reducing leak potential and improving system reliability.
4. Precision Dimensional Control: Tight tolerances on outer diameter (±0.05 mm) and wall thickness (±10%) ensure optimal fit in heat exchanger tube sheets and consistent heat transfer performance.
5. Full Traceability: Every coil is accompanied by a Mill Test Certificate (EN 10204 Type 3.1) with complete chemical and mechanical property data, enabling full supply chain traceability from raw material to installation.
6. Custom Fabrication Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers custom outer diameter, wall thickness, coil length, and surface finish configurations to meet specific project requirements and OEM specifications.
Technical Note
This product specification is derived from technical literature study (Document No. 469) examining the fresh air treatment process in dry coil air conditioning systems for commercial office buildings. The analysis demonstrates that stainless steel coil tubes operating in dry coil mode achieve dehumidification efficiencies of 70%–85% while consuming 30%–40% less energy compared to conventional evaporative cooling approaches. The material's corrosion resistance and dimensional stability under repeated thermal cycling make it the preferred choice for long-term reliability in precision HVAC environments.