Stainless Steel Coil Tube for Fan Coil Unit (FCU) Refrigeration Systems
Product Overview
The stainless steel coil tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1348) is a precision-engineered heat exchange component specifically designed for Fan Coil Unit (FCU) refrigeration systems. These coil tubes serve as the core thermal transfer elements within air conditioning and ventilation systems, facilitating efficient heat exchange between circulating refrigerant and ambient air. The product combines the corrosion resistance and mechanical integrity of austenitic stainless steel with optimized helical geometry to maximize surface-area-to-volume ratio, thereby enhancing thermal performance in compact installations.
Stainless steel coil tubes represent a critical upgrade over traditional copper or carbon steel alternatives in environments demanding high hygiene standards, chemical resistance, and extended service life. Their application in FCU systems addresses the growing industry requirement for reliable, maintenance-free heat exchange solutions in commercial, industrial, and institutional buildings.
Material & Properties
Material Composition
The coil tubes are fabricated from high-grade austenitic stainless steel, predominantly SUS304 (UNS S30400) and SUS316L (UNS S31603), selected for their superior combination of mechanical strength, corrosion resistance, and weldability.
- SUS304 (18/8 Stainless Steel): Contains 18% Chromium (Cr) and 8% Nickel (Ni), offering excellent general corrosion resistance suitable for most indoor HVAC applications.
- SUS316L (Low-Carbon Marine Grade): Incorporates 2–3% Molybdenum (Mo) with reduced Carbon (C ≤ 0.03%), providing enhanced resistance to chlorides, pitting, and crevice corrosion in coastal or chemically aggressive environments.
Mechanical Properties
- Tensile Strength (UTS): 515–720 MPa (SUS304); 530–720 MPa (SUS316L)
- Yield Strength (0.2% Offset): 205–310 MPa
- Elongation at Break: ≥ 40%
- Thermal Conductivity: 14.5–16.5 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Density: 8.00 g/cm³
- Operating Temperature Range: −196°C to +870°C
Corrosion Resistance
The passive chromium oxide film (Cr₂O₃) formed naturally on the stainless steel surface provides robust protection against oxidation, acid rain, condensation water, and common HVAC refrigerants. SUS316L grade further resists dezincification and intergranular corrosion, ensuring decades of reliable service in demanding applications.
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Product No. | 1348 | — |
| Product Name | Stainless Steel Coil Tube (盘管) | — |
| Material Grade | SUS304 / SUS316L | — |
| Outer Diameter (OD) | 6.35 / 9.53 / 12.70 / 15.88 | mm |
| Wall Thickness | 0.50 / 0.65 / 0.80 / 1.00 | mm |
| Coil Pitch (Center-to-Center) | 12 – 32 | mm |
| Coil Diameter | 50 – 500 | mm |
| Effective Length per Section | 150 – 1200 | mm |
| Number of Rows (Passes) | 1 – 6 | — |
| Reinforcing Fins (Optional) | Aluminum or Stainless Steel Plate Fins | — |
| Fin Pitch | 1.5 – 3.0 | mm |
| Maximum Operating Pressure | 1.6 – 4.0 | MPa |
| Refrigerant Compatibility | R-410A, R-32, R-134a, R-404A, Water/Glycol | — |
| Surface Finish | Ba & E (Bright Annealed & Pickled), Ra ≤ 0.8 μm | — |
| End Connection | Flare, Compression, or Brazed (Copper/SS) | — |
| Standards Compliance | ASTM A269, ASTM A213, EN 10216-5, GB/T 14976 | — |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a precisely controlled multi-stage process to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Raw Material Procurement: Cold-rolled stainless steel strip or seamless tube blanks conforming to ASTM A269/A213 specifications are sourced from certified mills with full mill test certificates (MTC).
- Coiling & Forming: The tube blank is precisely wound into the target helical geometry using CNC-controlled coiling machinery. Controlled springback compensation ensures dimensional accuracy within ±0.2 mm tolerance.
- Welding (if applicable): Spiral-wound coils are seam-welded using Pulse Inert Gas Welding (P-IGW) under Argon (Ar) shielding to prevent oxidation. Weld penetration is verified via radiographic testing (RT) or ultrasonic testing (UT).
- Fin Installation (if equipped): Aluminum or stainless steel plate fins are inserted at precise pitches using automated slitting and insertion equipment, ensuring uniform thermal contact without distortion.
- Heat Treatment: Stress-relief annealing at 850–950°C followed by controlled cooling eliminates residual forming stresses and restores full austenitic microstructure.
- Surface Treatment: Pickling and passivation removes oxide scale and contaminants, forming a stable chromium oxide passive layer for maximum corrosion resistance.
- Pressure Testing: Each coil undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure to verify leak-tightness and structural integrity.
- Final Inspection & Packaging: Dimensional verification, visual inspection, and material certification are completed before protective packaging for shipment.
Applications
Stainless steel coil tubes for FCU systems find extensive application across multiple sectors:
- Commercial HVAC Systems: Office buildings, shopping malls, hotels, and hospitals where Fan Coil Units provide zone-level temperature control with high hygiene requirements.
- Industrial Processes: Chemical processing plants, pharmaceutical manufacturing, and food/beverage facilities requiring corrosion-resistant heat exchange in aggressive environments.
- Marine & Coastal Installations: Seaside resorts, offshore platforms, and naval applications where chloride-induced corrosion is a primary concern (SUS316L grade).
- Cleanroom & Laboratory Environments: Semiconductor fabrication, biotechnology labs, and hospital operating rooms demanding ultra-low particulate and contamination-free surfaces.
- Radiant Heating & Cooling Systems: Underfloor and ceiling-mounted coil systems for residential and commercial temperature regulation.
- Refrigeration & Cold Chain: Chilled water coil applications in warehouse cold storage and distribution centers.
Quality Certifications & Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems to ensure product excellence:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System demonstrating sustainable manufacturing practices.
- CE Marking — European Conformity certification for compliance with relevant EU directives.
- ASTM / ASME Compliance — Products manufactured to ASTM A269 (seamless tubing) and ASTM A213 (heat transfer tubing) specifications.
- EN 10216-5 — European standard for stainless steel welded tubes for heat exchangers.
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for fluid conveyance.
- Mill Test Certificates (MTC): Full chemical composition and mechanical property documentation provided with each batch.
- Non-Destructive Testing (NDT): 100% ultrasonic testing and dye penetrant inspection (DPI) on welds and critical surfaces.
Unique Selling Points
1. Superior Corrosion Resistance: Unlike carbon steel or copper alternatives, the austenitic stainless steel construction provides exceptional resistance to condensation water, chemical contaminants, and atmospheric corrosion—eliminating the need for chemical treatment or protective coatings.
2. Extended Service Life: With proper installation, these coil tubes offer 25–50+ years of reliable operation, significantly reducing lifecycle costs compared to copper coil alternatives that suffer from galvanic corrosion and oxidation.
3. Hygienic Surface: The smooth, non-porous stainless steel surface (Ra ≤ 0.8 μm) resists microbial growth, making it ideal for pharmaceutical, food-grade, and healthcare applications.
4. Thermal Efficiency: Optimized helical geometry with precision-controlled coil pitch maximizes heat transfer coefficient while maintaining low pressure drop, improving overall system COP (Coefficient of Performance).
5. Environmentally Friendly: Stainless steel is 100% recyclable with no loss of material properties, aligning with green building certifications (LEED, BREEAM) and sustainable HVAC design principles.