Stainless Steel Coil Tube (Coil Tube) — Technical Product Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Code: JX-CT-1031
Classification: Seamless / Welded Stainless Steel Coil Tube for HVAC & Energy Recovery Systems
1. Product Overview
The Stainless Steel Coil Tube (Coil Tube) is a precision-engineered tubular component supplied in continuous coil form, designed for use in air-conditioning systems, air-air energy recovery devices (Energy Recovery Ventilators, ERVs), fan coil units (FCUs), and heat exchange applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product is specifically optimized for dry-condition operation scenarios where energy efficiency and corrosion resistance are critical performance parameters.
Coil tubes in this category serve as the core heat transfer elements within air-handling equipment. When integrated into air-air energy recovery devices, these coil tubes facilitate the transfer of sensible and latent heat between supply and exhaust air streams, thereby significantly reducing the energy consumption of HVAC systems operating under dry conditions. The product is available in a wide range of outer diameters (OD), wall thicknesses, and coil lengths to accommodate diverse system design requirements.
Key Performance Insight: Studies on air-air energy recovery devices have demonstrated that the use of high-grade stainless steel coil tubes in fan coil unit dry-condition operation can achieve energy savings of up to 25–40% compared to conventional carbon steel alternatives, owing to superior thermal conductivity, corrosion resistance, and long-term dimensional stability.
2. Material & Properties
2.1 Material Grades
The coil tubes are manufactured from high-quality austenitic stainless steel grades conforming to international standards:
- AISI 304 / SUS 304 / 06Cr19Ni10 — General-purpose corrosion-resistant grade with excellent formability
- AISI 316 / SUS 316 / 022Cr17Ni12Mo2 — Enhanced molybdenum content for superior resistance to chloride-induced pitting and crevice corrosion
- AISI 316L / SUS 316L / 022Cr17Ni12Mo2 (Low Carbon) — Low-carbon variant for improved weldability and reduced intergranular corrosion risk
- AISI 321 / SUS 321 / 06Cr18Ni11Ti — Titanium-stabilized grade for high-temperature applications
2.2 Mechanical Properties
| Property | Unit | Typical Value (AISI 304) | Typical Value (AISI 316L) |
|---|---|---|---|
| Tensile Strength | MPa | ≥ 520 | ≥ 485 |
| Yield Strength (0.2% Offset) | MPa | ≥ 205 | ≥ 170 |
| Elongation (at Break) | % | ≥ 40 | ≥ 40 |
| Thermal Conductivity (20°C) | W/(m·K) | 16.3 | 14.6 |
| Thermal Expansion Coefficient (20–100°C) | ×10⁻⁶ /K | 17.3 | 16.0 |
| Density | g/cm³ | 7.93 | 8.00 |
| Maximum Service Temperature | °C | 870 | 870 |
2.3 Surface Finish Options
- 2B Finish (Cold Rolled & Annealed): Standard mill finish with a smooth, semi-matte appearance; suitable for general industrial applications.
- No. 4 Brushed Finish: Fine linear grain pattern; provides enhanced aesthetic appearance for visible installations.
- Mirror / 8K Finish: High-gloss reflective surface achieved through mechanical polishing; ideal for food-grade and pharmaceutical applications.
- Pickled & Passivated: Chemical treatment to remove scale and form a protective chromium oxide passive layer for maximum corrosion resistance.
3. Technical Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Product Type | Stainless Steel Coil Tube (Continuous Coil Form) | — |
| Outer Diameter (OD) | Φ6 mm – Φ108 mm | ASTM A213 / EN 10216-5 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A213 / EN 10216-5 |
| Coil Length | 5 m – 200 m (customizable) | — |
| Coil Inner Diameter (ID) | Φ100 mm – Φ500 mm | — |
| Tolerance on OD | ±0.05 mm – ±0.15 mm (per diameter range) | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Manufacturing Method | Seamless (Pierced) or ERW Welded (Electric Resistance Welded) | ASTM A269 / ASTM A312 |
| End Condition | Plain, Beveled, or Threaded (upon request) | — |
| Heat Treatment | Solution Annealed (1050–1150°C) + Water Quenched | ASTM A213 |
| Packaging | Export-grade wooden pallet / plastic wrap / moisture-proof packaging | ISO 4180 |
3.1 Common Size Chart (Selected Dimensions)
| OD (mm) | Wall Thickness (mm) | Inner Diameter (mm) | Weight (kg/m) | Typical Application |
|---|---|---|---|---|
| 6.35 | 0.81 | 4.73 | 0.11 | Micro-channel heat exchangers |
| 9.52 | 1.02 | 7.48 | 0.22 | Fan coil unit coils |
| 12.70 | 1.24 | 10.22 | 0.37 | ERV heat transfer cores |
| 15.88 | 1.24 | 13.40 | 0.46 | Air conditioning condensers |
| 19.05 | 1.50 | 16.05 | 0.70 | Medium-duty HVAC systems |
| 25.40 | 1.65 | 22.10 | 1.02 | Large capacity heat exchangers |
| 31.75 | 2.00 | 27.75 | 1.45 | Industrial process cooling |
| 38.10 | 2.00 | 34.10 | 1.88 | High-flow air handling units |
4. Manufacturing Process
4.1 Seamless Coil Tube Production
- Raw Material Preparation: High-purity stainless steel billets are procured from certified mills. Incoming material undergoes spectroscopic analysis to verify chemical composition compliance.
- Heating: Billets are heated in a controlled-temperature furnace to the piercing temperature (approximately 1150–1250°C), ensuring uniform austenitization.
- Piercing: The heated billet is pierced using a mandrel piercing mill to produce a hollow shell (tube blank).
- Elongation & Reduction: The pierced tube passes through multiple reduction stands to achieve the target outer diameter and wall thickness.
- Coiling: The finished tube is wound onto a coiling reel to produce the continuous coil form. Tension and speed are precisely controlled to maintain dimensional accuracy.
- Solution Annealing: The coil tube is annealed at 1050–1150°C followed by rapid water quenching to achieve full solution treatment, eliminating residual stresses and optimizing corrosion resistance.
- Pickling & Passivation: Chemical treatment to remove any surface oxide scale and establish a protective chromium-rich passive layer.
- Quality Inspection: 100% inline inspection including dimensional measurement, visual examination, and hydrostatic pressure testing.
- Packaging & Dispatch: Coils are wrapped in protective plastic film and secured on export-grade wooden pallets.
4.2 ERW Welded Coil Tube Production
- Strip Forming: Pre-cut stainless steel strip is fed through a series of forming rolls to produce a tubular shape.
- Edge Preparation: Strip edges are trimmed and prepared for welding.
- Welding: High-frequency electric resistance welding (ERW) joins the tube seam with minimal heat-affected zone.
- Weld Annealing: The welded tube is locally annealed to homogenize the weld zone metallurgy.
- OD Sizing & Coiling: Final outer diameter is set via sizing rolls, followed by coiling.
- Post-Weld Heat Treatment & Surface Treatment: Full solution annealing and pickling as per seamless process.
4.3 Process Control Highlights
- Continuous online monitoring of tube OD, wall thickness, and roundness via laser measurement systems
- Hydrostatic pressure testing at 1.5× working pressure for 100% of production
- Electromagnetic and eddy-current flaw detection for seam integrity verification
- In-process chemical composition verification via XRF (X-Ray Fluorescence) analyzers
5. Applications
5.1 HVAC & Energy Recovery Systems
- Air-Air Energy Recovery Devices (ERV / HRV): Coil tubes serve as the heat transfer medium in enthalpy wheels and plate heat exchangers, recovering both sensible and latent energy from exhaust air streams. The corrosion-resistant properties of stainless steel ensure long-term efficiency in high-humidity environments.
- Fan Coil Units (FCU) — Dry Condition Operation: In dry-condition operation modes, stainless steel coil tubes maintain optimal heat transfer performance without degradation, enabling significant energy savings compared to copper or carbon steel alternatives.
- Air Conditioners & Chillers: Used in evaporator and condenser coil assemblies where resistance to refrigerant corrosion and condensate attack is essential.
5.2 Industrial & Commercial Applications
- Food Processing & Beverage Industry: Compliant with FDA and 3-A Sanitary Standards for food-grade heat exchange applications.
- Pharmaceutical Manufacturing: GMP-compliant coil tubes for clean steam generation and process cooling systems.
- Chemical Processing: AISI 316/316L grades withstand aggressive chemical environments and corrosive process fluids.
- Marine & Offshore Systems: Superior chloride resistance in seawater-cooled heat exchangers and ballast water systems.
- Solar Thermal Systems: High-temperature resistance of austenitic grades enables use in concentrated solar power (CSP) heat transfer loops.
5.3 Architectural & Specialized Applications
- Decorative piping in commercial and residential interiors
- Medical equipment fluid transfer systems
- Semiconductor manufacturing clean room HVAC systems
6. Quality Certifications & Compliance
6.1 International Standards Compliance
| Standard | Description | Applicability |
|---|---|---|
| ASTM A213 | Standard Specification for Seamless Austenitic Chromium-Chromium-Nickel Steel Tubing for High-Temperature Service | Material & Mechanical Properties |
| ASTM A269 | Standard Specification for Welded Austenitic Chromium-Chromium-Nickel Steel Tubing and Pipe | Welded Tube Manufacturing |
| ASTM A312 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipe, Tubing, and Hollow Shapes | General Product Specification |
| EN 10216-5 | Technical Delivery Conditions for Stainless Steel Tubes — Part 5: Seamless Tubes for General Purposes | European Market Compliance |
| GB/T 14976 | Stainless Steel Seamless Tubes for Fluid Transport (Chinese National Standard) | Domestic Market Compliance |
| ISO 4180 | Steel Tubes — Packaging and Marking | Packaging Standards |
| ASME |