Stainless Steel Coil Tube (FCU Water Circuit Application)
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Code: 1682
Product Overview
The Stainless Steel Coil Tube is a precision-engineered coiled tubing product specifically designed for use in the water circuit systems of Fan Coil Units (FCU). As a critical heat exchange component, this coil tube facilitates efficient thermal transfer between the circulating water medium and the air stream within HVAC (Heating, Ventilation, and Air Conditioning) systems. The product represents an advanced improvement over conventional coil designs, addressing issues such as flow maldistribution, pressure drop optimization, and enhanced heat transfer surface utilization.
Wenzhou Jixing Metal Materials Co., Ltd. applies advanced metallurgical expertise and precision forming technology to produce coil tubes that meet the rigorous demands of modern commercial and residential HVAC applications. The coil tube geometry is optimized to maximize the effective heat exchange area while minimizing hydraulic resistance within the water circuit.
Material & Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel — Grade 304 (UNS S30400) or Grade 316L (UNS S31603)
- Equivalent Standards: EN 1.4301 (304), EN 1.4401 (316L)
- Composition (304): Cr 18.0–20.0%, Ni 8.0–10.5%, Mn ≤2.0%, Si ≤0.75%, C ≤0.08%, P ≤0.045%, S ≤0.030%
- Composition (316L): Cr 16.0–18.0%, Ni 10.0–14.0%, Mo 2.0–3.0%, C ≤0.03%, Si ≤0.75%, Mn ≤2.0%
Mechanical Properties
- Tensile Strength: ≥520 MPa (304), ≥515 MPa (316L)
- Yield Strength: ≥205 MPa (304), ≥170 MPa (316L)
- Elongation at Break: ≥40% (minimum)
- Hardness: ≤217 HB (annealed condition)
- Operating Temperature Range: −196°C to +450°C
- Maximum Working Pressure: Up to 1.6 MPa (standard), configurable to 2.5 MPa
Corrosion Resistance
- Excellent resistance to atmospheric corrosion, industrial atmospheres, and non-chloride-containing water
- Grade 316L provides superior resistance to chloride-induced pitting and crevice corrosion
- Passive film self-healing capability in oxidizing environments
- Compliant with NSF/ANSI 61 for potable water contact applications
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm / 8.0 mm / 9.53 mm / 12.0 mm (configurable) | ASTM A213 |
| Wall Thickness | 0.5 mm – 1.5 mm (typical: 0.8 mm) | ASTM A269 |
| Coil Pitch (Center-to-Center Spacing) | 8.0 mm – 15.0 mm (optimizable per thermal load) | ASHRAE 34 |
| Row Depth | 2-row / 4-row / 6-row / 8-row configurations | — |
| Coil Length (Per Section) | 300 mm – 1,200 mm | — |
| Surface Finish | Mirror Polish (Ra ≤ 0.4 μm) or Satin Finish (Ra ≤ 1.6 μm) | ASTM A480 |
| Tube Forming Process | Continuous Push-Through Bending | — |
| Hydrostatic Test Pressure | 1.5 × Working Pressure (minimum 2.4 MPa) | EN 10216-5 |
| Water Flow Velocity (Design) | 1.0 – 1.5 m/s | ASHRAE 90.1 |
| Heat Transfer Coefficient (Water Side) | ≥ 3,500 W/(m²·K) | — |
| Design Service Life | ≥ 25 years (indoor application) | — |
Manufacturing Process
- Raw Material Inspection: Incoming stainless steel strip undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify alloy composition compliance with ASTM/EN specifications. Mill test certificates are cross-referenced.
- Strip Annealing & Cleaning: Cold-rolled strip is solution-annealed at 1,050–1,100°C followed by controlled cooling to achieve full austenitic microstructure. Surface is chemically pickled and passivated to establish a stable chromium oxide passive layer.
- Tube Forming (Spiral Winding): The flat strip is wound into a continuous helical coil using a CNC-controlled winding machine. Precise control of pitch, diameter, and wall thickness is maintained within ±0.05 mm tolerance.
- Push-Through Bending: The helical coil is fed through precision forming dies to create the characteristic serpentine U-bend pattern. Bend radii are calculated to prevent wall thinning below 70% of original thickness and to avoid ovalization exceeding 5%.
- Copper Brazing: Individual coil sections are joined at headers (inlet/outlet manifolds) using phosphorus-free copper brazing alloy (CuSn0.7Zn0.3 per EN 1083) at 620–650°C under nitrogen atmosphere protection.
- Hydrostatic Pressure Testing: Each completed coil assembly is subjected to hydrostatic testing at 1.5× the design working pressure for a minimum of 30 seconds to verify weld integrity and structural soundness.
- Final Inspection & Cleaning: Internal bores are flushed with deionized water and dried. Surface finish is verified by profilometry. Dimensional accuracy is confirmed using CMM (Coordinate Measuring Machine) where applicable.
Applications
- Fan Coil Units (FCU): Primary application — serves as the water-side heat exchange element in ceiling-mounted, wall-mounted, and concealed ducted FCUs for commercial and residential HVAC systems.
- Chilled Water Systems: Efficient cooling coil operation in air handling units (AHU) and terminal units in district cooling networks.
- Hot Water Heating: Radiant heating coils in underfloor systems and convective heating terminals.
- Refrigeration Evaporators: Low-temperature evaporator coils in commercial refrigeration units (with appropriate alloy selection for low-temperature ductility).
- Industrial Process Cooling: Precision temperature control coils in pharmaceutical, food processing, and electronics manufacturing facilities.
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System — sustainable manufacturing practices |
| CE Marking (EU) | Compliance with European Machinery Directive 2006/42/EC and Pressure Equipment Directive 2014/68/EU (PED) |
| ASTM A213 / A269 | Standard specifications for wrought austenitic stainless steel tube |
| EN 10216-5 | European standard for welded austenitic stainless steel tubes for pressure purposes |
| NSF/ANSI 61 | Health effects standard for drinking water system components |
| UL Listed (Component) | Underwriters Laboratories safety certification for HVAC component applications |
| RoHS 2011/65/EU | Restriction of Hazardous Substances — compliance with EU directive |
Unique Selling Points
- Optimized Water Circuit Design: Improved flow distribution architecture derived from computational fluid dynamics (CFD) analysis, reducing pressure drop by up to 18% compared to conventional coil geometries while maintaining equivalent thermal performance.
- Enhanced Heat Transfer Efficiency: Internal surface micro-texturing and optimized coil pitch geometry increase the effective heat transfer area by 12–15%, improving COP (Coefficient of Performance) in the overall HVAC system.
- Superior Corrosion Durability: Full austenitic stainless steel construction eliminates risk of intergranular corrosion and galvanic degradation, ensuring 25+ year service life without replacement.
- Precision Manufacturing Tolerances: CNC-controlled forming ensures dimensional consistency across production batches, guaranteeing reliable assembly integration with FCU housing components.
- Customizable Configurations: Modular design philosophy allows adaptation of coil dimensions, row depth, and pitch to specific thermal load requirements (from 0.5 kW to 15 kW cooling capacity per unit).
- Low Maintenance Requirement: Smooth internal bore finish (Ra ≤ 0.4 μm) minimizes scale and biofilm accumulation, reducing maintenance frequency and extending operational intervals.
Note: All specifications are subject to verification against the applicable version of referenced standards at the time of order. Custom engineering solutions are available upon request with detailed thermal load data and installation constraints. Wenzhou Jixing Metal Materials Co., Ltd. provides full traceability documentation including Mill Test Reports (MTR), heat numbers, and lot-specific inspection records for every production batch.