Stainless Steel Coil Tube — HVAC & Laboratory Humidity Control System
Product Overview
The Stainless Steel Coil Tube (Product No. 696) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping product designed for use in fan coil unit (FCU) systems, laboratory humidity regulation apparatus, and industrial thermal management applications. This coil tube is formed from high-grade austenitic stainless steel wire through continuous cold-coiling processes, delivering superior corrosion resistance, thermal conductivity, and mechanical durability in demanding environmental control scenarios.
The product is specifically optimized for integration into fan coil unit laboratory humidity adjustment systems, where precise temperature-humidity coupling control is essential for environmental simulation testing, material conditioning, and process validation. The coil geometry maximizes surface area-to-volume ratio, facilitating efficient heat exchange between the working fluid and ambient air within enclosed test chambers.
Material & Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel — SUS304 / SUS316 / SUS316L (equivalent to AISI 304 / 316 / 316L)
- Wire Form: Cold-drawn annealed stainless steel wire, precision-diameter tolerance ±0.05 mm
- Surface Finish: Bright annealed (BA) or electrolytic polished (EP), surface roughness Ra ≤ 0.4 μm
Key Material Properties
- Corrosion Resistance: Excellent resistance to atmospheric, acidic, and chloride-containing environments (SUS316 grade)
- Thermal Conductivity: 14.9 – 16.3 W/(m·K) at 20°C (SUS304 grade)
- Operating Temperature Range: −196°C to +870°C (continuous service)
- Mechanical Strength: Tensile strength ≥ 520 MPa; yield strength ≥ 205 MPa (annealed condition)
- Non-magnetic: Susceptibility ≤ 1.5 × 10⁻⁵ m³/kg (annealed state)
- Hygienic Compliance: FDA-compliant surface, suitable for food-grade and pharmaceutical applications
Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 3.0 – 25.0 mm (customizable) | ±0.10 mm |
| Wall Thickness (WT) | 0.3 – 2.0 mm | ±0.05 mm |
| Coil Pitch (Center-to-Center) | 5.0 – 30.0 mm (adjustable per design) | ±0.30 mm |
| Coil Diameter (Helical) | 100 – 800 mm | ±2.0 mm |
| Coil Length | 0.5 – 12.0 m (standard); up to 25.0 m (special order) | ±50 mm |
| Number of Turns | 20 – 500 turns | ±2 turns |
| End Forming | Flared, threaded (G/NPT/M), or flat-cut with deburring | — |
| Pressure Rating | Up to 4.0 MPa (working pressure at 20°C) | — |
| Hydrostatic Test Pressure | 6.0 MPa (30 seconds hold, no leakage) | — |
| Surface Treatment | Bright annealed / Electropolished / Passivated | — |
| Packaging | Anti-static PE film wrapped, wooden crate or carton | — |
Manufacturing Process
- Wire Selection & Inspection: Cold-drawn stainless steel wire is sourced from certified suppliers and undergoes spectroscopic analysis (PMI) to confirm alloy composition compliance with ASTM A213 / EN 10216-5 standards.
- Wire Annealing: Wire is solution-annealed at 1050–1150°C followed by controlled air cooling to achieve a fully austenitic, stress-free microstructure with optimal formability.
- Precision Coiling: Computerized CNC coiling machines form the wire into helical coils with programmable pitch, diameter, and turn count. The process maintains uniform curvature without introducing residual stress concentrations.
- Heat Treatment (Post-Coiling): Optional stress-relief annealing at 400–500°C stabilizes dimensional accuracy and eliminates work-hardening effects introduced during forming.
- End Processing: Coil ends are machined, flared, or threaded according to customer specifications. Deburring ensures smooth fluid flow entry/exit.
- Surface Finishing: Electropolishing or passivation treatment removes free iron contamination and establishes a chromium-rich passive oxide layer (Cr₂O₃) for enhanced corrosion protection.
- Quality Inspection: Each coil undergoes dimensional verification (caliper/micrometer), hydrostatic pressure testing, and visual surface inspection. Batch sampling includes hardness testing and intergranular corrosion testing (ASTM A262 Practice E).
- Packaging & Labeling: Coils are individually wrapped in anti-static protective film, labeled with product identification, material grade, and traceability batch number.
Applications
Primary Application Domains
- Fan Coil Unit (FCU) Systems: Serves as the heat exchange coil element in commercial HVAC fan coil units, facilitating precise temperature and humidity control in indoor environments.
- Laboratory Humidity Regulation: Integral component in environmental test chambers and laboratory humidity adjustment apparatus, where stainless steel coil tubes circulate chilled or heated water to maintain set-point temperature-humidity conditions (e.g., 23°C/50% RH ±2% for material conditioning per ASTM D523).
- Process Cooling/Heating: Used in chemical processing, pharmaceutical manufacturing, and food industry heat exchangers where hygienic and corrosion-resistant tubing is mandated.
- Refrigeration & Chiller Systems: Functions as evaporator or condenser coil in industrial refrigeration units operating with water or glycol-based secondary refrigerants.
- Specialty Equipment: Incorporated into scientific instruments, laboratory reactors, and pilot-scale equipment requiring inert, non-contaminating fluid circulation paths.
Unique Selling Points
- Superior Corrosion Performance: SUS316L grade offers exceptional resistance to chloride pitting and intergranular corrosion, extending service life in humid and chemically aggressive environments beyond carbon steel alternatives.
- Precision Geometric Control: CNC-driven coiling ensures repeatable pitch and diameter accuracy (±0.30 mm), critical for consistent heat transfer performance across production batches.
- Hygienic Surface Quality: Electropolished finish with Ra ≤ 0.4 μm prevents bacterial adhesion and fluid contamination — essential for pharmaceutical and food-grade applications.
- Full Traceability: Each coil carries a unique batch identification enabling complete material traceability from wire mill certification through final product delivery.
- Customization Capability: Flexible configuration options (diameter, pitch, length, end form) allow tailored integration into specific system designs without compromising material integrity.
- Thermal Efficiency: Optimized coil geometry maximizes heat transfer surface area while maintaining low flow resistance, reducing pumping energy requirements in closed-loop systems.
Quality Certifications & Standards Compliance
| Standard / Certification | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Manufacturing & Supply Chain |
| ASTM A213 / A269 | Material specification for austenitic stainless steel tube & pipe |
| EN 10216-5 | European standard for seamless austenitic stainless steel tubes |
| GB/T 12771 | Chinese national standard for stainless steel seamless tubes |
| ASTM A262 Practice E | Intergranular corrosion resistance testing |
| NSF/ANSI 61 | Drinking water system components — health effects |
| 3-A Sanitary Standards | Dairy & food processing equipment hygiene requirements |
| CE Marking | European Conformity for pressure equipment (PED 2014/68/EU) |
Testing & Verification Protocol
- Material Verification: Portable XRF (X-ray Fluorescence) spectroscopy for 100% batch alloy composition confirmation
- Dimensional Inspection: Coordinate Measuring Machine (CMM) or laser scanning for coil geometry verification
- Pressure Testing: Hydrostatic test at 1.5× working pressure for 30-second hold time with zero leakage criterion
- Surface Integrity: Visual and dye penetrant inspection (ASTM E165) for surface defects, cracks, or laps
- Chromium Passivation Test: Copper-acetic acid immersion test (ASTM A967) verifying minimum 6-hour resistance without staining
Note: Wenzhou Jixing Metal Materials Co., Ltd. maintains a commitment to continuous improvement and technical excellence. All coil tube products are manufactured under documented procedures with full traceability, ensuring consistent quality performance across production cycles. Custom engineering support is available for specialized humidity control and thermal management applications.