Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into building HVAC (Heating, Ventilation, and Air Conditioning) systems. As a critical component within Fan Coil Units (FCUs), the coil tube serves as the primary heat exchange medium, facilitating efficient thermal transfer between circulating refrigerant/water and ambient air. This product is engineered to address the complex interface challenges between mechanical coil assemblies and architectural building envelopes, ensuring seamless integration, optimal thermal performance, and long-term structural reliability within both commercial and residential building systems.
The coil tube is supplied in continuous coiled form, allowing for flexible on-site fabrication and installation to accommodate diverse architectural geometries, ductwork configurations, and space-constrained building environments. This coiled delivery format minimizes material waste, reduces field welding requirements, and enables rapid deployment in multi-unit building projects.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical strength, and thermal conductivity properties. The following material characteristics define the product's performance envelope:
- Base Material: Austenitic stainless steel (Grade 304 / 316L, per ASTM A213 / EN 10216-5)
- Corrosion Resistance: Excellent resistance to oxidation, chlorides, and condensate-induced corrosion in humid HVAC environments
- Thermal Conductivity: Optimized for efficient heat exchange between fluid media and surrounding air
- Mechanical Strength: High tensile strength and yield strength ensuring dimensional stability under thermal cycling and pressure differentials
- Hygienic Surface: Smooth inner and outer wall finish (Ra ≤ 0.8 μm) minimizing fouling and facilitating cleaning
- Temperature Range: Suitable for continuous operation from -40 °C to +200 °C
- Non-Magnetic: Austenitic microstructure ensures non-magnetic properties
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Material Grade | ASTM A213 TP304 / TP316L | ASTM A213 / EN 10216-5 |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (1/4" – 1") | ISO 65 / EN 10217 |
| Wall Thickness | 0.5 mm – 1.5 mm | ±0.05 mm tolerance |
| Coil Diameter | 300 mm – 1500 mm (adjustable) | Per project requirement |
| Coil Length | Up to 500 m per coil (continuous) | Customizable |
| Surface Finish | Bright annealed / Pickled and passivated | ISO 11463 |
| Pressure Rating | Up to 1.6 MPa (232 psi) | ASME B31.9 |
| Welding Compatibility | TIG (GTAW) / Orbital / Laser welding | ASME Section IX |
| Packaging | Wooden crate / Steel frame with moisture barrier | ISO 4180 |
| Customization | OD, wall thickness, coil diameter, length, and bend radius available per drawing | Per customer specification |
4. 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 consistent surface quality:
- Raw Material Selection & Inspection: High-purity austenitic stainless steel wire rod is sourced from certified mills and subjected to spectroscopic analysis (OES / PMI) to verify chemical composition compliance with ASTM A213 specifications.
- Draw & Form (Tube Drawing): The wire rod is drawn through precision tungsten carbide dies to achieve the target outer diameter and wall thickness. Multiple drawing passes ensure uniform cross-sectional geometry and dimensional tolerances within ±0.05 mm.
- Heat Treatment & Annealing: The formed tube undergoes controlled bright annealing in a continuous annealing furnace (CAF) under a reducing atmosphere to relieve residual stresses, restore full austenitic microstructure, and achieve the desired mechanical properties.
- Pickling & Passivation: The annealed tube is treated with a controlled acid pickling solution to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide film on the surface, enhancing corrosion resistance.
- Coiling & Winding: The finished tube is wound into continuous coils on precision winding mandrels. Coil diameter and winding tension are controlled to prevent kinking, ovality, or surface damage during coiling.
- Quality Inspection: Each coil undergoes non-destructive testing (NDT) including eddy current inspection for wall thickness verification, dimensional gauge checks, surface quality assessment, and hydrostatic pressure testing at 1.5× working pressure.
- Packaging & Dispatch: Coils are wrapped with moisture-proof film, secured with steel strapping, and packed in reinforced wooden crates or steel frames for safe transportation and storage.
5. Applications
The stainless steel coil tube is engineered for integration into Fan Coil Units (FCUs) and building HVAC systems, addressing the critical interface between mechanical coil assemblies and architectural building structures. Key application domains include:
- Commercial Building HVAC Systems: Primary heat exchange coils in ceiling-mounted, wall-mounted, and concealed Fan Coil Units for office buildings, hotels, hospitals, and retail complexes. The coil tube's corrosion resistance ensures long service life in high-humidity environments where condensate formation is prevalent.
- Residential Climate Control: Coil assemblies for residential FCUs and air handling units (AHUs) in high-end residential developments, providing quiet, efficient, and hygienic indoor climate regulation.
- Industrial Process Cooling & Heating: Heat exchange coils in industrial ventilation systems, process air conditioning, and temperature-controlled cleanrooms where stainless steel's hygienic and chemical resistance properties are essential.
- Building Envelope Integration: The coiled form factor facilitates adaptation to irregular architectural geometries, tight installation spaces, and custom ductwork routing, directly addressing the "coil-to-building interface" challenges identified in building integration studies.
- Condenser & Evaporator Coils: Use in both evaporator and condenser sections of split-system FCUs, where the tube's thermal conductivity and dimensional stability ensure consistent heat transfer performance over extended thermal cycling.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring that every production batch meets international standards and regulatory requirements:
- ISO 9001:2015: Quality Management System certification covering all aspects of design, manufacturing, inspection, and delivery
- ISO 14001:2015: Environmental Management System certification demonstrating commitment to sustainable manufacturing practices
- Material Certification: Each coil is accompanied by a Mill Test Certificate (MTC) / Certificate of Conformance (CoC) verifying chemical composition and mechanical properties per ASTM A213 / EN 10216-5
- NDT Compliance: Eddy current testing, hydrostatic pressure testing, and dimensional inspection performed per ISO 9955 / ASME B31.9
- RoHS & REACH Compliance: Material composition verified to comply with European Restriction of Hazardous Substances and Registration, Evaluation, Authorisation and Restriction of Chemicals directives
- Third-Party Inspection: Available upon request — SGS, Bureau Veritas, or TÜV inspection for international project compliance
7. Unique Selling Points
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd distinguishes itself through the following value propositions:
- Architectural Integration Optimization: The continuous coiled form factor directly addresses the well-documented challenge of integrating mechanical coil assemblies with diverse building envelope geometries, enabling flexible on-site adaptation without compromising thermal performance.
- Superior Corrosion Resistance: The austenitic stainless steel construction provides exceptional resistance to condensate-induced corrosion — a primary failure mode in HVAC coil applications — extending service life significantly beyond carbon steel alternatives.
- Hygienic Performance: The smooth, passivated inner surface minimizes biofilm formation and fouling, ensuring consistent thermal efficiency over the product lifecycle and reducing maintenance requirements.
- Customizable Specifications: Full range of OD, wall thickness, coil diameter, and length options available to match specific project requirements, enabling optimization for both performance and space-constrained installations.
- Full Traceability: Every coil is traceable to its raw material batch through certified mill documentation, ensuring accountability across the supply chain.
- Reduced Installation Complexity: The coiled delivery format minimizes field welding, reduces installation labor time, and decreases the risk of installation-induced defects compared to straight-length tube solutions.