Stainless Steel Coil Tube for HVAC Fan Coil Systems
Product Overview
The Stainless Steel Coil Tube (Product Code: 1010) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product specifically designed for integration into fan coil unit (FCU) systems and air conditioning heat exchangers. This coil tube is engineered to meet the demanding requirements of high-temperature, high-humidity (HTHH) environments, where conventional carbon steel or copper-based coil tubes suffer from accelerated corrosion, reduced thermal efficiency, and shortened service life.
Based on extensive research into the adaptability of independent fresh air combined with dry-type fan coil air conditioning systems in HTHH regions, this stainless steel coil tube addresses critical performance degradation issues observed in traditional coil tube designs. The product leverages the superior corrosion resistance, thermal stability, and mechanical integrity of austenitic stainless steel to deliver reliable, long-term performance in the most challenging climatic conditions.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and formability. The primary alloy grades utilized are as follows:
- Grade 304 (UNS S30400) — Chromium-Nickel austenitic stainless steel with 18% Cr and 8% Ni, offering excellent general-purpose corrosion resistance and weldability.
- Grade 316L (UNS S31603) — Low-carbon variant with added 2–3% Molybdenum, providing superior resistance to chlorides, acids, and marine atmospheres prevalent in coastal HTHH regions.
- Grade 321 (UNS S32100) — Stabilized with Titanium, suitable for elevated-temperature service where sensitization must be prevented.
Key Mechanical Properties
| Property | Grade 304 | Grade 316L | Grade 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K) at 20°C | 16.3 | 16.3 | 16.3 |
| Density (kg/m³) | 7930 | 8000 | 7930 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
| Corrosion Resistance (ASTM G48) | Good | Excellent | Good |
Specifications
| Parameter | Specification |
|---|---|
| Product Code | 1010 |
| Product Name | Coil Tube (盘管) |
| Outer Diameter (OD) | 6.0 mm – 16.0 mm (customizable) |
| Wall Thickness | 0.3 mm – 1.2 mm (customizable) |
| Coil Length | Up to 200 m per continuous coil |
| Surface Finish | Bright Annealed (BA), No. 4 Brushed, or Mirror Polished (Ra ≤ 0.4 μm) |
| Tube End Condition | Deburred, squared, or beveled per customer specification |
| Dimensional Tolerance (OD) | ±0.05 mm (standard); ±0.02 mm (precision grade) |
| Dimensional Tolerance (Wall) | ±0.01 mm |
| Roundness | ≤ 0.02 mm |
| Coil Pitch | 2.0 mm – 8.0 mm (adjustable for heat exchanger design) |
| Operating Pressure Rating | Up to 1.6 MPa (standard); 2.5 MPa (reinforced) |
| Service Fluids | Chilled water, glycol-water mixtures, refrigerants (R-134a, R-410A, R-32) |
| Standards Compliance | ASTM A269, ASTM A270, GB/T 12771, EN 10216-5 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement & Verification — Certified stainless steel coils (annealed condition) are sourced from approved mills. Each batch undergoes spectroscopic analysis (OES) to verify chemical composition against ASTM/GB specifications.
- Coil Forming & Bending — Precision coil forming equipment creates the helical tube geometry with controlled pitch and radius. The forming process is executed in a single continuous operation to minimize work hardening and stress concentration.
- Welding (if applicable) — Where continuous coils are required with longitudinal seams, automated TIG (Tungsten Inert Gas) welding is employed with argon shielding gas to achieve full-penetration welds with minimum heat-affected zone (HAZ).
- Pickling & Passivation — The formed coil tube undergoes acid pickling to remove mill scale and welding discoloration, followed by citric or nitric acid passivation to establish a protective chromium oxide layer (Cr₂O₃).
- Surface Finishing — Depending on the application requirement, the tube may undergo mechanical polishing, electrolytic polishing, or chemical brightening to achieve the specified surface roughness.
- Dimensional Inspection — Each coil tube is measured using laser micrometers, calipers, and roundness gauges. Statistical Process Control (SPC) is applied throughout production.
- Pressure Testing — Hydrostatic pressure testing at 1.5× the rated working pressure is conducted to verify weld integrity and wall thickness uniformity.
- Packaging & Dispatch — Tubes are coiled, wrapped in protective film, and packed in wooden crates or export-grade containers to prevent damage during transit.
Applications
The stainless steel coil tube is purpose-engineered for the following critical applications:
- Independent Fresh Air + Dry Fan Coil Systems — As demonstrated in adaptability research for high-temperature, high-humidity regions, this coil tube serves as the core heat exchange element in dry-type fan coil units, where condensate-free operation and corrosion resistance are paramount.
- Hospital & Pharmaceutical HVAC Systems — The hygienic surface finish and resistance to microbial growth (biofilm inhibition) make this product ideal for cleanroom and laboratory air handling units.
- Marine & Coastal Building HVAC — Grade 316L coil tubes withstand aggressive chloride-containing atmospheres in coastal environments without pitting or crevice corrosion.
- Food & Beverage Processing Plants — Compliance with sanitary standards (FDA, 3-A) ensures suitability for washdown environments and direct food-contact air systems.
- Commercial & Industrial Chilled Water Systems — Integration into air handling units (AHUs), rooftop units (RTUs), and precision cooling systems for data centers and manufacturing facilities.
- Desert & Tropical Climate Buildings — Superior thermal cycling resistance and resistance to condensation-induced corrosion in environments with extreme diurnal temperature variation.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product consistency and traceability:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and inspection processes.
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices.
- CE Marking — Conformity with European directives for construction products and machinery.
- ASTM A269/A270 — American standards compliance for welded and seamless 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.
- Mill Test Certificates (MTC) — En 10204 Type 3.1 certificates provided with every shipment, including full chemical analysis, mechanical test results, and heat traceability.
- Third-Party Inspection — Available upon request through SGS, BV, or TÜV for buyer verification.
Unique Selling Points
The following differentiators distinguish this stainless steel coil tube from competing products in the market:
- HTHH-Optimized Design — Specifically engineered based on research findings for high-temperature, high-humidity adaptability, addressing condensate accumulation and corrosion failure modes identified in conventional coil tube systems.
- Extended Service Life — Up to 10–15× longer lifespan compared to carbon steel coil tubes in aggressive environments, significantly reducing total cost of ownership (TCO).
- Corrosion-Free Heat Exchange — Eliminates the risk of iron ion contamination in chilled water circuits, preventing downstream scaling and maintaining system efficiency over the operational lifetime.
- Customizable Geometry — Flexible coil pitch, OD, and wall thickness options allow OEMs to optimize heat transfer performance for specific fan coil unit designs.
- Full Traceability — Every coil tube is traceable to its heat number, enabling complete supply chain accountability and facilitating warranty claims.
- Hygienic Surface Finish — Electrolytically polished surfaces with Ra ≤ 0.4 μm inhibit bacterial colonization, meeting pharmaceutical and food-grade requirements without additional treatment.
Note: All specifications are subject to revision without prior notice. For project-specific requirements, Wenzhou Jixing Metal Materials Co., Ltd offers custom engineering support, sample fabrication, and on-site technical consultation to ensure optimal system integration.