Stainless Steel Coil Tube — Fan Coil Unit Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed primarily for integration into fan coil unit (FCU) systems, this product delivers superior thermal transfer performance, exceptional corrosion resistance, and extended service life under demanding HVAC (Heating, Ventilation, and Air Conditioning) operating conditions. The coil tube is supplied in continuous coil form, enabling efficient downstream forming, cutting, and assembly operations without the need for additional welding joints, thereby minimizing potential failure points and maximizing system reliability.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, typically conforming to grades 304 (UNS S30400) and 316L (UNS S31603), selected for their outstanding resistance to oxidation, pitting, and crevice corrosion. The material composition ensures long-term structural integrity when exposed to humid environments, condensate formation, and periodic chemical cleaning agents common in HVAC maintenance cycles.
- Base Material: Austenitic Stainless Steel (Type 304 / 316L)
- Tensile Strength: ≥ 515 MPa (75,000 psi)
- Yield Strength: ≥ 205 MPa (29,750 psi)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and mild chemical environments
- Temperature Range: −196°C to +870°C (−321°F to +1,598°F)
- Surface Finish: Bright annealed (BA) or 2B finish; optional electropolished
- Hygienic Grade: Available in sanitary-grade finish (Ra ≤ 0.5 μm) for pharmaceutical and food-grade applications
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.18 mm (1/8") – 19.05 mm (3/4") |
| Wall Thickness | 0.30 mm – 1.20 mm | Coil Inner Diameter | 300 mm – 600 mm |
| Coil Length per Roll | 50 m – 500 m (customizable) |
| Material Grade | SUS 304 / SUS 316L / UNS S30400 / UNS S31603 |
| Surface Treatment | Bright Annealed, 2B, Passivated, or Electropolished |
| Dimensional Tolerance | OD: ±0.05 mm; Wall Thickness: ±0.02 mm |
| Roundness | ≤ 0.02 mm |
| Standard Compliance | ASTM A213/A213M, ASTM A554, EN 10217-7, GB/T 12771 |
| Packaging | Wooden pallet with moisture-proof wrapping; export-grade crating available |
Manufacturing Process
The production of stainless steel coil tube follows a rigorous multi-stage process ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Strip Preparation: Cold-rolled stainless steel strip is inspected for surface defects, chemical composition, and mechanical properties prior to forming.
- Forming (Seamless or Welded): The strip is wound around a mandrel using a high-precision forming machine. For welded coil tube, a TIG (Tungsten Inert Gas) welding process is employed with internal helium backing to ensure full-penetration weld integrity.
- Heat Treatment / Annealing: Bright bar annealing (BBA) is performed under a controlled reducing atmosphere to relieve residual stresses and restore full ductility.
- Precision Sizing: Multi-roll sizing passes reduce dimensional tolerances to ±0.05 mm and ensure roundness compliance.
- Surface Finishing: Passivation treatment removes free iron contamination, enhancing passive film stability. Optional electropolishing achieves mirror-like surface finishes.
- Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification via laser measurement, and periodic hydrostatic testing or eddy current flaw detection.
- Coiling & Packaging: The finished tube is coiled onto precision rollers and packaged with protective wrapping to prevent mechanical damage and moisture exposure during transit.
Applications
The stainless steel coil tube serves as a critical heat exchange element across multiple industries:
- HVAC Systems: Primary application in fan coil units (FCU), air handling units (AHU), and chilled water terminal units for commercial buildings, hospitals, and data centers.
- Refrigeration & Cryogenics: Low-temperature heat exchangers, evaporators, and condensers in industrial refrigeration plants.
- Food & Beverage Processing: Hygienic-grade heat transfer coils in pasteurization systems, CIP (Clean-in-Place) loops, and dairy processing equipment.
- Pharmaceutical Manufacturing: GMP-compliant heat exchange systems requiring sanitary-grade surface finishes and traceability documentation.
- Chemical Processing: Corrosion-resistant heat exchange coils for aggressive chemical environments, including acid handling and solvent recovery systems.
- Marine & Offshore: Seawater-cooled heat exchangers where chloride-induced pitting corrosion resistance is paramount (316L grade).
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and inspection processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- CE Marking — Conformity with European health, safety, and environmental protection standards.
- EN 10204 3.1 — Third-party material test certificates provided with each shipment, documenting chemical analysis, mechanical testing, and dimensional verification.
- ASTM/ASME Compliance — Products manufactured in accordance with ASTM A213/A213M and ASME B31.3 pressure piping codes.
- Mill Test Reports (MTR) — Full traceability documentation including heat number, chemical composition, and mechanical property data for every production lot.
- Third-Party Inspection: Independent inspection available by SGS, Bureau Veritas, or TÜV upon customer request.
Unique Selling Points
1. Seamless Heat Transfer Efficiency: Continuous coil form eliminates longitudinal weld seams, providing uniform thermal conductivity and eliminating potential leak paths associated with welded joints in critical service.
2. Precision Dimensional Control: Advanced multi-roll sizing technology achieves tolerances of ±0.05 mm on outer diameter, ensuring optimal fit in tube sheets and brazed plate heat exchangers.
3. Comprehensive Grade Selection: Availability in both 304 and 316L grades allows customers to optimize material cost versus corrosion resistance requirements for their specific application environment.
4. Extended Service Life: Superior corrosion resistance extends equipment service intervals, reducing maintenance frequency and total cost of ownership (TCO) over the lifecycle of the installation.
5. Customizable Specifications: Flexible manufacturing capability accommodates non-standard diameters, wall thicknesses, coil dimensions, and surface finishes to meet project-specific engineering requirements.
6. Full Traceability: End-to-end material traceability from mill origin through final inspection, supported by digital documentation and barcode-based lot tracking systems.
Maintenance & Operational Recommendations
Based on established industry best practices for fan coil unit systems incorporating stainless steel coil tubes, the following maintenance guidelines are recommended to maximize operational efficiency and service life:
- Perform visual inspection of coil surfaces at intervals not exceeding 6 months to detect fouling, scaling, or physical damage.
- Implement a scheduled chemical cleaning program using pH-neutral, stainless steel-compatible cleaning agents to prevent chloride-induced stress corrosion cracking.
- Monitor differential pressure across coil circuits; a 20% increase may indicate internal fouling requiring descaling or replacement.
- Ensure proper water treatment in closed-loop systems, maintaining pH between 8.5 and 9.5 and limiting dissolved oxygen to below 0.05 ppm.
- Verify condensate drain pan integrity and proper slope to prevent standing water that could promote microbial growth or localized corrosion.
- Document all maintenance activities in a centralized asset management system for regulatory compliance and predictive maintenance planning.