Stainless Steel Coil Tube (盘管 Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tubing product formed into a helical coil configuration. This product is primarily designed for thermal exchange and fluid transport applications, with particular suitability in HVAC (Heating, Ventilation, and Air Conditioning) systems, including Fan Coil Units (FCUs) such as the ECR400 series. The coil tube serves as a critical heat exchanger element, enabling efficient transfer of thermal energy between a working fluid and ambient air.
As a product under the "Literature Learning" (文献学习) classification, this coil tube has been extensively studied in experimental research contexts, particularly regarding its performance characteristics in fan coil unit assemblies. The ECR400-type Fan Coil Unit performance research has identified key influencing factors including coil geometry, fluid flow velocity, fin spacing, and material thermal conductivity — all of which are directly addressed in the design and manufacturing of this product.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, and mechanical integrity under cyclic thermal loading conditions.
2.1 Material Grades
- 304 Stainless Steel (UNS S30400 / AISI 304): The standard grade offering excellent general-purpose corrosion resistance with 18% Chromium (Cr) and 8% Nickel (Ni) composition.
- 316L Stainless Steel (UNS S31603 / AISI 316L): Enhanced grade with added Molybdenum (Mo, 2–3%) for superior resistance to pitting and crevice corrosion in aggressive chemical environments.
- 321 Stainless Steel (UNS S32100 / AISI 321): Titanium-stabilized grade providing resistance to intergranular corrosion at elevated operating temperatures.
2.2 Key Mechanical & Physical Properties
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C
- Specific Heat Capacity: 0.502 J/(g·°C)
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C
- Yield Strength (0.2% offset): ≥ 205 MPa (annealed condition)
- Tensile Strength: 515–700 MPa
- Operating Temperature Range: −196°C to +870°C
- Maximum Working Pressure: Up to 1.6 MPa (depending on wall thickness and diameter)
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.0 mm, 8.0 mm, 10.0 mm, 12.0 mm, 16.0 mm, 20.0 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Pitch (Helix Spacing) | 10 mm – 50 mm (configurable per application) |
| Coil Diameter | 150 mm – 800 mm |
| Coil Length | Up to 10,000 m per continuous coil |
| Surface Finish | 2B (cold-rolled annealed), No.4 (brushed), or BA (Bright Annealed) |
| Tolerance (OD) | ±0.05 mm – ±0.10 mm |
| Tolerance (Wall Thickness) | ±0.03 mm – ±0.08 mm |
| End Treatment | Flat-cut, chamfered, or pre-flared |
| Surface Roughness (Ra) | ≤ 0.8 μm (internal); ≤ 1.6 μm (external) |
| Applicable Standards | ASTM A213/A213M, ASTM A269/A269M, GB/T 12771, EN 10216-5 |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing sequence:
- Hot Rolling (Hot Rolling Mill): Stainless steel slab is heated to approximately 1,100–1,200°C and hot-rolled into a round or rectangular cross-section strip of specified dimensions.
- Pickle & Anneal: The hot-rolled strip undergoes acid pickling to remove oxide scale, followed by solution annealing to restore full austenitic microstructure.
- Cold Reduction: The strip is cold-rolled to achieve the desired final wall thickness and dimensional precision, introducing beneficial strain hardening.
- Tube Forming: The strip is formed into a tubular configuration using either the helical welding method or seamless piercing (for larger diameters).
- Welding (if applicable): Helical or longitudinal welding is performed using TIG (Tungsten Inert Gas) welding with argon shielding to ensure a high-integrity, leak-tight weld seam.
- Post-Weld Annealing: The welded tube is annealed at 1,050–1,100°C followed by water quenching to homogenize the weld zone and restore corrosion resistance.
- Coil Forming (Coiling): The straight tube is wound into the specified helical coil geometry using a precision coiling machine that maintains consistent pitch and diameter.
- Final Annealing: Optional stress-relief annealing to eliminate residual stresses introduced during coiling.
- Surface Treatment: Final surface finishing to the specified grade (2B, No.4, or BA) with optional passivation treatment for enhanced corrosion resistance.
- Quality Inspection: Comprehensive non-destructive testing (NDT) including eddy current inspection, hydrostatic pressure testing, and visual examination.
5. Applications
The Stainless Steel Coil Tube finds extensive application across multiple industrial sectors:
- HVAC Systems: Primary application in Fan Coil Units (FCUs), including the ECR400 series, as the core heat exchange element for air conditioning and heating systems in commercial and residential buildings.
- Refrigeration & Cold Chain: Evaporator and condenser coils in refrigeration units, cold storage facilities, and freeze-drying equipment.
- Food & Beverage Processing: Sanitary-grade heat exchangers in dairy, brewing, and pharmaceutical processing where hygienic standards mandate stainless steel construction.
- Automotive Industry: Intercooler tubes, oil coolers, and heater core assemblies in vehicle thermal management systems.
- Chemical Processing: Heat exchangers and process coils in chemical reactors where resistance to aggressive media is required.
- Marine Applications: Seawater-cooled heat exchanger coils benefiting from 316L grade's superior chloride resistance.
- Geothermal Systems: Underground heat exchange coils for geothermal heating and cooling installations.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance systems and holds the following certifications:
- ISO 9001:2015: Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015: Environmental Management System certification for sustainable manufacturing practices.
- ISO 45001:2018: Occupational Health and Safety Management System certification.
- CE Marking (European Conformity): Compliance with European directives for market access in the European Economic Area.
- PED 2014/68/EU: Pressure Equipment Directive compliance for pressure-rated coil assemblies.
- EN 10204 3.1: Material Test Certificate (MTC) provided with each batch, documenting chemical composition and mechanical properties.
- ASME B31.3: Compliance with piping code requirements for process applications.
Each production batch undergoes rigorous inspection protocols including:
- Chemical composition analysis (spectroscopic verification)
- Mechanical property testing (tensile, hardness, impact)
- Dimensional measurement (OD, wall thickness, coil pitch, coil diameter)
- Surface quality assessment (visual and roughness profiling)
- Pressure testing (hydrostatic or pneumatic at 1.5× working pressure)
- Corrosion resistance testing (salt spray test per ASTM B117, minimum 480 hours for 304; 1,000 hours for 316L)
7. Unique Selling Points
- Research-Validated Performance: Product design informed by experimental research on ECR400-type Fan Coil Unit performance influencing factors, ensuring optimized thermal efficiency through validated coil geometry parameters.
- Customizable Coil Geometry: Flexible manufacturing capability allowing precise control over coil pitch, diameter, and length to match specific heat exchange requirements.
- Superior Corrosion Resistance: Austenitic stainless steel construction provides decades of service life without degradation, even in humid or chemically aggressive environments.
- Hygienic Internal Surface: Smooth internal bore (Ra ≤ 0.8 μm) minimizes fouling and facilitates CIP (Clean-in-Place) procedures in food and pharmaceutical applications.
- Thermal Cycling Durability: Excellent fatigue resistance under repeated thermal cycling, critical for HVAC applications with frequent on/off operation.
- Full Traceability: Complete material traceability from raw steel mill through final product, with documented MTC for every coil.
- Environmental Sustainability: Stainless steel is 100% recyclable without loss of properties; manufacturing process adheres to ISO 14001 environmental standards.
8. Packaging & Delivery
Coil tubes are delivered wound on protective wooden or steel reels, wrapped with moisture-proof plastic film and secured with stainless steel strapping. Each unit is labeled with product identification, heat number, dimensions, and certification documentation. Standard delivery packaging supports sea freight, rail transport, and road logistics worldwide.
9. Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive technical consultation for coil tube selection and system integration. Custom manufacturing is available for non-standard dimensions, special grades, and application-specific configurations. Engineering support includes thermal performance simulation, pressure drop calculations, and material selection guidance tailored to specific operating conditions.