Stainless Steel Coil Tube (Coiltube) — HVAC Energy-Efficient Application Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-length tubular product specifically designed for integration into large-space HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly in configurations involving Fresh Air Ventilators with Fan Coil Units (FCUs). This product series is engineered to optimize thermal transfer efficiency while maintaining structural integrity under prolonged operational conditions, thereby contributing to significant energy conservation in commercial, industrial, and institutional large-space applications.
As a coiled continuous tube, the product eliminates the need for extensive field welding or joining, reducing installation labor and potential leak points. The coil configuration allows for compact storage, efficient transportation, and rapid deployment in mechanical system installations. The fundamental design philosophy is rooted in the principles of thermodynamic efficiency and system-level energy optimization, as validated by comprehensive studies on energy-saving analysis in large-space ventilation systems employing fan coil unit configurations.
Material & Properties
Base Material Composition
- Primary Alloy: Austenitic Stainless Steel conforming to AISI 304 (UNS S30400) or AISI 316L (UNS S31603) specifications, selected based on application corrosivity requirements.
- Carbon Content (C): ≤ 0.08% (304) or ≤ 0.03% (316L) — ensuring resistance to intergranular corrosion during thermal cycling.
- Chromium (Cr): 18.0–20.0% — providing the passive oxide layer essential for corrosion resistance.
- Nickel (Ni): 8.0–10.5% — stabilizing the austenitic microstructure for ductility and toughness.
- Molybdenum (Mo): 2.0–2.5% (316L grade) — enhancing resistance to pitting and crevice corrosion in chloride-containing environments.
Mechanical Properties
- Tensile Strength: ≥ 520 MPa (75,000 psi) minimum
- Yield Strength: ≥ 205 MPa (29,700 psi) minimum
- Elongation: ≥ 40% (indicating excellent formability for coiling operations)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C — providing reliable heat transfer performance for HVAC coil applications
- Operating Temperature Range: −196°C to +870°C (continuous service)
Surface Finish & Corrosion Resistance
- Surface Treatment: Pickled and passivated (acid-etched finish) to establish a uniform chromium oxide passive film.
- Potential Difference (PD): ≥ 500 mV (indicating adequate passivation quality per ASTM A967).
- Pitting Resistance Number (PREN): 19–20 (316L grade) — superior resistance to localized corrosion in humid HVAC environments.
Specifications
| Parameter | Specification |
|---|---|
| Product Category | Stainless Steel Coil Tube (Continuous Coiled Tubing) |
| Material Grade | AISI 304 / 304L / 316L / 321 (upon request) |
| Outer Diameter (OD) | Φ6.0 mm – Φ50.8 mm (1/4" – 2" nominal) |
| Wall Thickness | 0.30 mm – 3.00 mm (customizable per application requirements) |
| Coil Width | Up to 200 mm (flat coil configuration) or single-tube continuous coil |
| Coil Length per Spool | 30 m – 300 m (continuous, spool-wound) |
| Dimensional Tolerance | OD: ±0.05 mm; Wall: ±0.02 mm (precision cold-drawn) |
| Surface Roughness (Ra) | ≤ 0.8 μm (interior); ≤ 0.4 μm (exterior, upon request) |
| Formability | Capable of 360° bending with minimum bend radius of 1.5× OD without cracking |
| Pressure Rating | Up to 1.6 MPa (232 psi) at 20°C, depending on wall thickness |
| Standards Compliance | ASTM A213, ASTM A269, EN 10216-5, GB/T 14976 |
| Package | Wooden reel or steel drum with moisture-proof inner wrapping |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorously controlled multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Hot-Rolled Coil Production: Continuous casting of stainless steel slabs followed by hot rolling to produce strip or pipe blank coils. This initial stage establishes the base microstructure and approximate dimensions.
- Pickling & Annealing: The hot-rolled coil undergoes acid pickling (using a mixture of hydrochloric and nitric acids) to remove mill scale and oxidation. Subsequent annealing at 1050–1150°C in a controlled-atmosphere furnace (protective gas or vacuum) homogenizes the grain structure and restores full ductility.
- Cold Drawing (Precision Forming): The annealed strip is cold-drawn through progressively smaller dies to achieve the final outer diameter and wall thickness within tight tolerances. This process induces beneficial work hardening while maintaining formability.
- Intermediate Annealing: Where required for thicker wall sections, intermediate annealing cycles are applied between cold-drawing passes to prevent excessive work hardening and cracking.
- Seam Welding (if applicable): For welded tube configurations, high-frequency induction welding (HFW) or TIG (Tungsten Inert Gas) orbital welding is employed with precise heat input control to minimize distortion and ensure weld integrity.
- Coiling: The finished tube is wound onto precision reels or drums in continuous coil form. Tension control during coiling ensures uniform layer-to-layer contact and prevents springback or kinking.
- Final Passivation & Surface Treatment: The coiled product undergoes final passivation treatment per ASTM A967 to ensure the chromium oxide film is fully established and protective.
- Quality Inspection & Packaging: Each coil is subjected to dimensional verification, visual inspection, and non-destructive testing (NDT) prior to protective packaging and dispatch.
Applications
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. finds primary application in the following domains:
HVAC Systems — Large-Space Ventilation & Fan Coil Units
- Fresh Air Ventilator Coils: Serving as heat exchange elements in large-space fresh air handling units, where the coil tube facilitates efficient sensible and latent heat transfer between air streams and refrigerant or hydronic fluid.
- Fan Coil Unit (FCU) Integration: The continuous coil configuration enables compact, high-surface-area heat exchangers within fan coil units deployed in commercial buildings, hospitals, data centers, and industrial facilities. Studies on energy-saving analysis in large-space applications have demonstrated that optimized coil tube geometry and material selection can reduce system energy consumption by 15–25% compared to conventional configurations.
- Chilled Water & Hot Water Circulation Loops: Corrosion-resistant tubing for secondary hydronic circuits in large-scale HVAC distribution systems.
Additional Application Areas
- Food & Pharmaceutical Processing: Sanitary-grade tubing (316L) for CIP (Clean-in-Place) compatible heat exchangers.
- Marine & Offshore Systems: 316L-grade coil tubes for HVAC systems in environments with high chloride exposure.
- Chemical Processing: Resistant to aggressive process fluids in heat exchange and distribution applications.
- Automotive & Aerospace: Precision-formed coil tubes for thermal management systems requiring lightweight, high-performance heat transfer.
- Renewable Energy Systems: Heat recovery units and thermal storage applications.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification frameworks:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System, reflecting commitment to sustainable manufacturing practices.
- ISO/TS 22163 — Quality management system for automotive components (where applicable to supply chain requirements).
- CE Marking — European Conformity for products intended for the European Economic Area market.
- Mill Test Reports (MTR): Full chemical analysis and mechanical property certification provided with each batch per ASTM E415.
- Non-Destructive Testing (NDT): 100% eddy current testing and/or ultrasonic testing available for weld seam integrity verification.
- Hydrostatic Testing: All tubes subjected to hydrostatic pressure testing per ASTM A213/A269 requirements.
- Third-Party Inspection: Available upon request through recognized inspection bodies (SGS, Bureau Veritas, TUV).
Unique Selling Points
Energy Efficiency Optimization: The coil tube product line has been specifically validated through energy-saving analysis studies for large-space HVAC applications. The continuous coil geometry maximizes heat transfer surface area per unit volume, directly contributing to reduced fan power consumption and improved Coefficient of Performance (COP) in fan coil unit systems.
- Zero-Weld Installation: The continuous coil format eliminates field welds, reducing installation time by up to 40% and virtually eliminating leak points.
- Superior Corrosion Longevity: Austenitic stainless steel construction provides service life exceeding 25 years in aggressive HVAC environments, far surpassing carbon steel alternatives.
- Precision Dimensional Control: Cold-drawn manufacturing ensures ±0.05 mm dimensional accuracy, enabling seamless integration with precision HVAC fittings and heat exchanger assemblies.
- Custom Configurability: Flexible OD, wall thickness, coil length, and material grade selection to match specific system design parameters.
- Sustainability: Stainless steel is 100% recyclable without loss of material properties, aligning with green building certification requirements (LEED, BREEAM, Green Star).
Technical Data Sheet Reference
For detailed dimensional drawings, material certificates, and application-specific engineering support, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Technical documentation is available in both English and Chinese to support international project requirements.