Stainless Steel Coil Tube — Fan Coil Unit Series (Ref. No. 1471)
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed specifically for integration into Fan Coil Unit (FCU) systems used in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) applications. These coil tubes are formed through a continuous cold-rolling and bending process, resulting in a helically wound configuration that maximizes heat transfer surface area within a compact volumetric envelope.
The product adheres to the principles outlined in the technical literature "Rational Selection of Fan Coil Unit Systems" (风机盘管机组的合理选用), which emphasizes optimal coil tube geometry, material integrity, and thermal-hydraulic performance to ensure energy-efficient operation and long service life in fan coil unit assemblies.
2. Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical strength, and thermal conductivity. The primary material grades include:
- SUS304 (AISI 304 / 1.4301) — General-purpose grade with excellent weldability and corrosion resistance, suitable for most HVAC environments.
- SUS316 (AISI 316 / 1.4401) — Molybdenum-enhanced grade offering superior resistance to chlorides and aggressive chemical environments.
- SUS304L / SUS316L — Low-carbon variants designed for enhanced weldability and resistance to intergranular corrosion.
Key material properties include:
- Thermal Conductivity: 14–16 W/(m·K)
- Density: 7,900 kg/m³
- Yield Strength: ≥ 205 MPa (SUS304), ≥ 170 MPa (SUS316)
- Tensile Strength: 515–720 MPa
- Operating Temperature Range: −196 °C to +870 °C
- Corrosion Resistance: Excellent against water, steam, dilute acids, and atmospheric corrosion
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Reference No. | 1471 | Internal Catalog |
| Product Name | Coil Tube (盘管) | — |
| Material Grade | SUS304 / SUS316 / SUS304L / SUS316L | ASTM A213 / GB/T 12771 |
| Outer Diameter (OD) | φ9.52 mm – φ15.88 mm (standard); custom available | ASME B36.19M |
| Wall Thickness | 0.50 mm – 1.50 mm | ASME B36.19M |
| Coil Pitch (Helix Spacing) | 12 mm – 25 mm (adjustable per design) | Custom |
| Coil Length | Up to 12,000 mm (standard); longer on request | Custom |
| Surface Finish | Mirror polished (Ra ≤ 0.4 μm), satin finish, or pickled & passivated | ASTM A967 |
| Tolerance (OD) | ±0.05 mm | ISO 4287 |
| Tolerance (Wall Thickness) | ±10% | ASTM A213 |
| End Treatment | Clean-cut, chamfered, or threaded per specification | Custom |
| Maximum Operating Pressure | 1.6 MPa (standard); 4.0 MPa (pressure-tested) | ASME B31.9 |
| Heat Transfer Coefficient | ≥ 45 W/(m²·K) (air-side), ≥ 1,500 W/(m²·K) (water-side) | ASHRAE Handbook |
| Weight | Varies by configuration; approximately 0.15–0.35 kg/m | Calculated per geometry |
| Packaging | Wooden crate with desiccant; export-grade packaging available | ISO 4180 |
4. Manufacturing Process
The production of the stainless steel coil tubes follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, material integrity, and functional reliability:
- Raw Material Selection & Inspection: Stainless steel strip or seamless pipe stock is sourced from certified suppliers. Incoming materials undergo spectroscopic analysis (PMI — Positive Material Identification) to verify alloy composition and confirm compliance with specified grades (SUS304/SUS316).
- Coil Winding / Helical Forming: The stainless steel tube is wound into a precise helical coil using CNC-controlled coil-winding machinery. The winding process maintains constant tension and pitch to prevent deformation, ovality, or stress concentration. Tolerance on coil pitch is maintained within ±0.2 mm.
- Welding & Seam Integrity: For welded coil tube configurations, the longitudinal seam is welded using TIG (Tungsten Inert Gas) welding under a protective argon atmosphere to prevent oxidation. Weld quality is verified through visual inspection and, where required, dye penetrant testing (DPT) or eddy current testing (ECT).
- Surface Finishing: The coil tube undergoes surface treatment including pickling (acid removal of oxide scale), passivation (chromium enrichment for corrosion resistance), and mechanical polishing (for mirror-finish applications). The final surface roughness (Ra) is measured and documented.
- Hydrostatic Pressure Testing: Each coil tube assembly is subjected to hydrostatic pressure testing at 1.5× the maximum operating pressure for a minimum dwell time of 30 seconds to verify leak tightness and structural integrity.
- Dimensional Inspection & Quality Control: Final products are inspected for outer diameter, wall thickness, coil pitch, overall length, straightness, and surface finish. Non-conforming units are rejected and reprocessed or scrapped in accordance with the quality management system.
- Packaging & Dispatch: Qualified coil tubes are cleaned, wrapped in protective film, and packed in export-grade wooden crates with moisture-absorbing desiccants to prevent corrosion during transit and storage.
5. Applications
The stainless steel coil tubes are primarily designed for integration into Fan Coil Unit (FCU) systems, but their versatility extends to a broad range of industrial and commercial applications:
- Commercial HVAC Systems: Fan coil units for office buildings, hotels, hospitals, shopping malls, and residential complexes, where the coil tube serves as the primary heat exchanger for air conditioning and heating.
- Industrial Process Heating & Cooling: Heat exchangers, evaporators, and condensers in chemical processing, food and beverage production, and pharmaceutical manufacturing.
- Refrigeration Systems: Evaporator coils and condenser coils in commercial refrigeration units, cold storage facilities, and refrigerated transport.
- Marine & Offshore Applications: Corrosion-resistant coil tubes for marine HVAC systems and offshore platform climate control, leveraging the superior chloride resistance of SUS316 grade.
- Cleanroom & Laboratory Environments: Precision air handling units requiring high surface finish quality and minimal particulate emission.
- Custom OEM/ODM Applications: Tailored coil tube assemblies for original equipment manufacturers requiring specific geometries, materials, or performance characteristics.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality assurance framework to ensure product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification, covering all aspects of design, manufacturing, and delivery.
- ISO 14001:2015 — Environmental Management System certification, demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Conformity with European health, safety, and environmental protection standards.
- ASME B31.9 — Compliance with the Pressure Piping Code for Building Services.
- ASTM A213 — Material specification compliance for seamless austenitic stainless steel tubing.
- GB/T 12771 — Chinese national standard for welded stainless steel tubing.
- EN 10216-5 — European standard for welded austenitic stainless steel tubes.
All production batches are accompanied by Mill Test Certificates (MTC) and Certificates of Conformance (CoC), providing full traceability of material origin, heat numbers, chemical composition, and mechanical test results.
7. Unique Selling Points
The stainless steel coil tubes offered by Wenzhou Jixing Metal Materials Co., Ltd. distinguish themselves through several key competitive advantages:
- Optimized Heat Transfer Geometry: The helical coil design provides a significantly higher surface-area-to-volume ratio compared to straight-tube heat exchangers, resulting in enhanced thermal efficiency and reduced energy consumption. This aligns with the principles of rational fan coil unit selection documented in industry literature.
- Superior Corrosion Resistance: The use of high-grade austenitic stainless steel (SUS304/SUS316) ensures exceptional resistance to water-side corrosion, scaling, and chemical attack, extending service life to 20–30 years under normal operating conditions — far exceeding the lifespan of copper or carbon steel alternatives.
- Dimensional Precision: CNC-controlled manufacturing ensures tight tolerances on outer diameter (±0.05 mm), wall thickness (±10%), and coil pitch (±0.2 mm), guaranteeing seamless integration into fan coil unit housings and air handlers.
- Hygienic Surface Quality: Mirror-polished surfaces (Ra ≤ 0.4 μm) minimize biofilm formation and facilitate cleaning, making these coil tubes ideal for pharmaceutical, food-grade, and cleanroom HVAC applications.
- Customization Flexibility: The manufacturer offers fully customizable configurations, including material grade, dimensions, coil geometry, surface finish, and end treatments, enabling tailored solutions for specialized engineering requirements.
- Comprehensive Quality Traceability: Full batch traceability through Mill Test Certificates, heat number tracking, and documented inspection records ensures complete supply chain transparency and regulatory compliance.
- Cost-Effective Lifecycle Value: While the initial material cost may be higher than copper alternatives, the extended service life, reduced maintenance frequency, and lower replacement costs deliver superior total cost of ownership (TCO) over the system lifecycle.
8. Technical Literature Reference
The design philosophy and selection criteria for these coil tubes are informed by the technical study "Rational Selection of Fan Coil Unit Systems" (风机盘管机组的合理选用), which addresses the critical factors in matching coil tube geometry, material properties, and thermal performance to specific HVAC application requirements. Key considerations include coil tube surface area adequacy, air-side and water-side heat transfer coefficients, pressure drop optimization, and the avoidance of under- or over-sizing that leads to inefficiency or inadequate thermal performance.