Stainless Steel Coil Tube (Coiltube) — HVAC & Air Conditioning Applications

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Catalog No.: 733

1. Product Overview

The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured in continuous coiled form, specifically designed for use in heating, ventilation, and air conditioning (HVAC) systems, fresh air treatment units, and heat exchange assemblies. Unlike conventional straight-length piping, coil tubes are supplied in long, continuous helical or spiral configurations, enabling efficient deployment in compact coil windings, louver-type fresh air handlers, and independent air treatment conditioning systems.

This product category encompasses a wide range of stainless steel grades tailored to specific thermal, mechanical, and corrosion resistance requirements. The continuous coil form factor minimizes material waste during coil winding operations, reduces the need for field welding or brazing joints, and facilitates rapid installation in heat exchanger banks, evaporator coils, and condenser assemblies.

2. Material Composition & Properties

Wenzhou Jixing Metal Materials Co., Ltd. offers stainless steel coil tubes in multiple austenitic and duplex grades, each selected to meet the demanding thermal cycling, humidity exposure, and chemical resistance demands of air conditioning and ventilation systems.

• Austenitic Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS316L (UNS S31603), and SUS321 (UNS S32100) provide excellent corrosion resistance, weldability, and formability at elevated and ambient temperatures.
• Duplex Grades: SUS2205 (UNS S32205) offers superior yield strength and resistance to chloride-induced pitting and crevice corrosion in coastal or industrial environments.
• Heat-Resistant Grades: SUS310S (UNS S31008) is available for high-temperature heat recovery applications exceeding 1000°C (1832°F).

Key material properties include:

• Operating temperature range: −196°C to 870°C (depending on grade)
• Tensile strength: 520–720 MPa (typical for annealed austenitic grades)
• Yield strength: 205–450 MPa (grade-dependent)
• Thermal conductivity: 14–16 W/(m·K) (austenitic grades at 20°C)
• Linear thermal expansion coefficient: 16–18 × 10⁻⁶ /°C

3. Technical Specifications

Parameter	Specification Range	Standard / Reference
Outer Diameter (OD)	3.0 mm – 50.8 mm (1/8" – 2")	ASTM A213 / EN 10216-5
Wall Thickness	0.3 mm – 2.5 mm	ASTM A213 / ISO 3506
Coil Length (Continuous)	50 m – 500 m per coil	Manufacturer Specification
Coil Diameter (Winding)	300 mm – 1500 mm	Application-Dependent
Tolerance on OD	±0.1 mm (precision); ±0.5 mm (standard)	ASTM A213M
Tolerance on Wall Thickness	±10% (standard); ±5% (precision)	ASTM A213M
Surface Finish	Mirror (Ra ≤ 0.2 μm), Hairline (Ra ≤ 0.8 μm), 2B (Ra ≤ 1.6 μm), Pickled & Passivated	ASTM A480
End Form	Plain cut, Beveled, Flared, or Bent to specification	Customer Drawing
Heat Treatment	Annealed (Solution Annealed), Stress-Relieved	ASTM A213
Maximum Operating Pressure	Up to 4.0 MPa (600 PSI) — grade and dimension dependent	ASME B31.3
Corrosion Resistance	Equivalent to or exceeding 316L for chloride environments	ASTM G48

4. Manufacturing Process

The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:

1. Raw Material Selection: High-purity stainless steel strip is procured from certified mill sources, with full chemical composition verification via Optical Emission Spectrometry (OES) and Positive Material Identification (PMI) testing.
2. Coil Forming (Tube Rolling): Precision flat strip is fed through a series of progressively narrowing forming rolls, which incrementally bend the strip into a tubular configuration while maintaining uniform wall thickness and roundness.
3. Welding: The formed tube is welded along the longitudinal seam using either Automatic Argon Arc Welding (TIG/GTAW) or Laser Welding. TIG welding is the industry standard for stainless steel coil tubes, providing high-quality, leak-tight weld seams with minimal heat-affected zone (HAZ) distortion.
4. Pipe Weld Inspection: Each weld seam undergoes 100% visual inspection and is subjected to volumetric testing (eddy current or ultrasonic) to detect discontinuities, porosity, or incomplete fusion.
5. Sizing & Straightening: The welded tube passes through calibrated sizing rolls to achieve precise OD and wall thickness tolerances, followed by straightening to ensure geometric linearity within the coil form.
6. Heat Treatment (Solution Annealing): Tubes are annealed at 1050°C–1100°C in a protective atmosphere (argon or endothermic gas) to restore full austenitic microstructure, relieve residual welding stresses, and maximize corrosion resistance.
7. Pickling & Passivation: Post-annealing tubes are pickled in a mixed acid bath (HNO₃ + HF) to remove the oxide scale, followed by passivation to establish a protective chromium oxide layer on the surface.
8. Surface Finishing: Depending on application requirements, tubes may undergo mechanical polishing, electropolishing, or mechanical brushing to achieve specified surface roughness values.
9. Coil Winding: The finished tube is wound onto precision steel or aluminum coil cores at controlled tension to prevent deformation, ovality, or kinking.
10. Final Quality Control: Comprehensive dimensional measurement, hydrostatic pressure testing (where applicable), surface inspection, and chemical analysis are performed prior to packaging and shipment.

5. Applications

Stainless steel coil tubes are integral components across a broad spectrum of industrial and commercial systems. Key application domains include:

5.1 HVAC & Air Conditioning Systems

• Louver Coil-Type Fresh Air Handlers: As documented in thermodynamic analyses of independent fresh air treatment air conditioning systems, coil tubes serve as the primary heat transfer elements in louver-type coil assemblies. These systems utilize numerically simulated coil geometries to optimize airflow distribution, thermal efficiency, and dehumidification performance.
• Evaporator & Condenser Coils: Continuous coil tubes are wound into serpentine or spiral coil configurations for use in chiller evaporators, air-cooled condensers, and heat recovery units.
• Heat Exchanger Bundles: Coil tubes are arranged in tube bundles for plate-fin heat exchangers, cross-flow heat exchangers, and shell-and-tube configurations in commercial and industrial refrigeration.

5.2 Fresh Air Treatment & Ventilation

• Independent fresh air conditioning systems employing coil tubes for sensible and latent heat exchange
• Makeup air units with integrated preheating or cooling coils
• Energy recovery ventilators (ERV) and heat recovery ventilators (HRV)

5.3 Additional Industrial Applications

• Automotive AC condenser tubes and evaporator coils
• Food processing and pharmaceutical equipment (hygienic-grade 316L)
• Marine HVAC systems (duplex 2205 for chloride resistance)
• Solar thermal collector absorber tubes
• Industrial process cooling and heating loops

6. Unique Selling Points

Thermodynamic Optimization: The coil tube geometry, when properly designed and numerically simulated, achieves superior heat transfer coefficients compared to straight-pipe configurations. The continuous helical path induces secondary flow patterns (Dean vortices) within the tube, enhancing turbulent mixing and convective heat transfer — a principle extensively validated in CFD-based numerical simulations of louver coil-type fresh air systems.

• Seamless Performance in a Welded Form: Modern TIG and laser welding techniques achieve weld integrity comparable to seamless tubing, eliminating the cost premium of seamless production while maintaining full pressure containment and corrosion resistance.
• Zero-Joint Installation: The continuous coil form eliminates field-welded joints, reducing leak points and installation labor by up to 40% compared to cut-and-weld straight pipe assemblies.
• Material Efficiency: Coil production yields 95–98% material utilization, minimizing trim waste and reducing overall project material costs.
• Full Traceability: Every coil is serialized with heat number, grade certification, dimensional test data, and NDT (Non-Destructive Testing) records, ensuring complete supply chain traceability per ISO 9001 quality management requirements.
• Custom Coil Geometry: Wenzhou Jixing supports custom coil diameters, pitch configurations, and end-forming to match specific coil winding machine specifications and heat exchanger design parameters.

7. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality assurance program with the following certifications and standards compliance:

• ISO 9001:2015 — Quality Management System Certification
• ISO 14001:2015 — Environmental Management System
• ASTM A213 / A213M — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
• EN 10216-5 — European Standard for Seamless and Welded Stainless Steel Tubes for General Purposes
• GB/T 14976 — Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport
• JIS G3459 — Japanese Industrial Standard for Stainless Steel Tubes for General Purposes
• ASME B31.3 — Process Piping Design Code Compliance
• SPIF (Stainless Pipe & Tube Institute of America) Membership — Industry Quality Standard Adherence

8. Testing & Inspection Protocol

Each production lot undergoes a multi-stage inspection regime:

1. Chemical Analysis: Spectrometric verification of Cr, Ni, Mo, C, Si, Mn, and other alloying elements per ASTM A276.
2. Mechanical Testing: Tensile and hardness testing per ASTM A276, with reported values for yield strength, ultimate tensile strength, and elongation.
3. Hydrostatic Pressure Testing: 100% inline hydrostatic testing at 2× working pressure for a minimum dwell time of 5 seconds, ensuring zero leakage.
4. Non-Destructive Testing (NDT): 100% eddy current or ultrasonic examination of the longitudinal weld seam per ASTM E709 or EN ISO 22806.
5. Dimensional Inspection: OD, wall thickness, roundness, and straightness measured per ASTM A213 tolerance tables.
6. Corrosion Testing (Upon Request): Salt spray testing per ASTM B117 (minimum 500 hours for 316L) or pitting resistance index (PREN) calculation.

9. Packaging & Delivery

Coil tubes are wound onto robust steel or aluminum coil cores, wrapped with VCI (Vapor Corrosion Inhibitor) film and stretch wrap, and secured with steel strapping. Each coil is labeled with a unique identification plate indicating grade, heat number, dimensions, coil weight, and production date. Shipping is available via standard export packaging or custom crating for international freight.

10. Technical Support & Customization

Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:

• Custom coil geometry design to match specific coil winding equipment parameters
• Grade selection consultation based on application environment (chloride, sulfur, high-temperature, cryogenic)
• CFD (Computational Fluid Dynamics) integration support for heat exchanger and air conditioning system design optimization
• Sample provision and trial manufacturing for prototype validation
• Technical data sheets (TDS), Material Test Certificates (MTC per EN 10204 3.1/3.2), and full traceability documentation

For detailed quotation, sample requests, or custom specification inquiries, contact Wenzhou Jixing Metal Materials Co., Ltd. directly with your application requirements, target grade, dimensional specifications, and quantity requirements.