Stainless Steel Coil Tube (Coiltube) – Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous-length tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in a coiled configuration, enabling efficient storage, transportation, and downstream processing. Coil tubes are integral components in HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial heat exchangers, fluid conveyance systems, and various mechanical assemblies where corrosion resistance, thermal conductivity, and mechanical durability are paramount.
The coiled form factor eliminates the need for field welding and joining, significantly reducing installation labor, minimizing leak points, and enhancing system reliability. This product line adheres to international manufacturing standards and is engineered to meet the rigorous performance demands of modern industrial and commercial applications.
2. Material & Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel – Grade 304 (UNS S30400) and Grade 316L (UNS S31603)
- Alternative Grades: 201 (UNS S30100), 304L (UNS S30403), 316 (UNS S31600), 321 (UNS S32100), 310S (UNS S31008)
- Form: Seamless and welded coil tubing, cold-drawn or cold-rolled
2.2 Key Mechanical Properties (Grade 304)
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (minimum, in 50 mm gauge length)
- Hardness: ≤ 92 HRB (Rockwell B scale)
- Density: 8.00 g/cm³
2.3 Key Mechanical Properties (Grade 316L)
- Tensile Strength: ≥ 485 MPa (70,300 psi)
- Yield Strength: ≥ 170 MPa (24,700 psi)
- Elongation: ≥ 40%
- Hardness: ≤ 92 HRB
2.4 Physical & Chemical Properties
- Corrosion Resistance: Superior resistance to atmospheric, chemical, and marine environments; Grade 316L offers enhanced pitting and crevice corrosion resistance due to molybdenum (Mo) content (2.0–3.0%)
- Operating Temperature Range: −196 °C to +870 °C (continuous service)
- Thermal Conductivity: 16.3 W/(m·K) at 100 °C (Grade 304)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)
- Surface Finish: Bright annealed, pickled, or polished (Ra ≤ 0.8 μm available upon request)
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A269 / EN 10217 |
| Wall Thickness | 0.3 mm – 3.0 mm (0.012" – 0.118") | ASTM A269 / ASME B36.19M |
| Coil Length per Spool | 50 m – 300 m (typical); custom lengths available | — |
| Coil Inner Diameter (Coil ID) | 200 mm – 600 mm | — |
| OD Tolerance | ±0.05 mm (precision grade); ±0.1 mm (commercial grade) | ASTM A269 |
| Wall Thickness Tolerance | ±10% (commercial); ±5% (precision) | ASTM A269 / EN 10217 |
| Roundness | ≤ 10% of nominal OD | — |
| Maximum Operating Pressure | Up to 25 MPa (3,625 psi) depending on geometry | ASME B31.3 |
| Minimum Bend Radius | 3D (3 × outer diameter) without mandrel | — |
| Surface Finish | Bright Annealed (BA), No. 4 Polished, Mirror Polished | ASTM A480 |
| Packaging | Wooden reel or steel drum with protective wrapping | ISO 11607 |
| Applicable Standards | ASTM A269, ASTM A778, EN 10217-7, GB/T 14976, JIS G3459 | — |
4. Manufacturing Process
4.1 Process Flow
- Material Selection & Incoming Inspection: Virgin stainless steel wire rod or strip is sourced from certified mills. Each batch undergoes spectroscopic analysis (OES) and mechanical testing to verify chemical composition and mechanical properties conform to the specified grade.
- Piercing & Extrusion (Seamless Route): Billet is heated to 1,150–1,250 °C and pierced on a mandrel to produce hollow tube blanks. Alternatively, cold extrusion is employed for precision small-diameter tubing.
- Hot Rolling / Cold Drawing: Tube blanks are progressively reduced through a series of cold-drawing dies to achieve the target OD and wall thickness with high dimensional accuracy.
- Heat Treatment (Solution Annealing): Tubes are annealed at 1,050–1,150 °C followed by rapid quenching (air or water) to restore full austenitic structure, relieve residual stresses, and maximize corrosion resistance.
- Pickling & Passivation: Post-heat-treatment surface oxide is removed via acid pickling (nitric + hydrofluoric acid blend), followed by passivation to establish a chromium-rich passive oxide layer (minimum Cr₂O₃ content ≥ 20% by weight).
- Coiling: Continuous-length tubing is wound onto precision reels using controlled tension systems to maintain uniform coil geometry and prevent kinking or deformation.
- Final Inspection & Testing: Each coil undergoes hydrostatic testing (at 1.5× working pressure, minimum 30 seconds dwell), dimensional measurement, surface inspection, and optional eddy current or ultrasonic flaw detection.
- Packaging & Dispatch: Coils are wrapped in moisture-proof film, secured on export-grade wooden reels or steel drums, and labeled with mill test certificates (MTC/EN 10204 3.1).
4.2 Quality Control Points
- Incoming material certification and lot traceability
- In-process dimensional monitoring at each drawing pass
- 100% hydrostatic pressure testing
- Non-destructive testing (NDT) – Eddy Current (EC) or Magnetic Particle Inspection (MPI) for surface defects
- Chemical composition verification via Optical Emission Spectroscopy (OES)
- Final dimensional audit against customer-specific tolerances
5. Applications
5.1 HVAC & Fan Coil Units (FCU)
Stainless steel coil tubes are extensively used in Fan Coil Unit (FCU) systems as the heat exchange element within air handling apparatus. In test apparatus for fan coil units, the supply air static pressure chamber (送风静压腔) height is a critical design parameter that directly influences airflow distribution uniformity and system efficiency. The coil tube's precise geometry and consistent thermal performance ensure accurate heat transfer characteristics during commissioning and operational testing.
5.2 Industrial Heat Exchangers
- Shell-and-tube heat exchangers
- Plate-fin and microchannel heat exchangers
- Condensers and evaporators in refrigeration systems
- Process cooling and heating circuits
5.3 Fluid Conveyance Systems
- Food and beverage processing (FDA-compliant)
- Pharmaceutical and bioprocessing (cGMP environments)
- Chemical and petrochemical pipelines
- Compressed air and gas distribution
5.4 Specialized Applications
- Automotive exhaust and fuel system tubing
- Medical device instrumentation
- Cryogenic fluid transfer (Grade 316L, rated to −196 °C)
- Marine and offshore platforms (Grade 316L / Super Duplex)
- Solar thermal collector systems
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System – certified manufacturing processes |
| ISO 14001:2015 | Environmental Management System |
| EN 10204 3.1 | Material Test Certificate – inspection results conforming to specified requirements |
| ASTM A269 / A778 | Standard specification for austenitic stainless steel seamless, welded, and cold-drawn tubing |
| EN 10217-7 | European standard for stainless steel tubes for heat exchangers and condensers |
| GB/T 14976 | Chinese national standard for cold-rolled stainless steel seamless tubes |
| CE Marking | Conformity to European directives for machinery and pressure equipment |
| ASME B31.3 | Process piping design and fabrication compliance |
| 3-A Sanitary Standard | Sanitary design for dairy, food, and pharmaceutical applications |
7. Unique Selling Points
- Continuous-Length Supply: Coiled configuration eliminates field joints and welds, reducing potential failure points by up to 90% compared to segmented pipe installations.
- Dimensional Precision: Cold-drawing process achieves OD tolerances as tight as ±0.05 mm, ensuring optimal fit in automated assembly and heat exchanger tube sheets.
- Full Traceability: Every coil is accompanied by a Mill Test Certificate (MTC) with lot-specific chemical analysis, mechanical test results, and heat treatment records.
- Multi-Grade Availability: Comprehensive grade portfolio (201, 304, 304L, 316, 316L, 321, 310S) accommodates diverse environmental and performance requirements.
- Custom Fabrication: Special ODs, wall thicknesses, coil lengths, and surface finishes available upon request with lead times as short as 15 working days.
- Corrosion Performance: Passivated surfaces provide a corrosion rate below 0.05 mm/year in most industrial environments; Grade 316L achieves < 0.01 mm/year in chloride-containing solutions.
- Hygienic Design: Available in electropolished finish (Ra ≤ 0.4 μm) meeting 3-A and EHEDG standards for food-grade and pharmaceutical applications.
8. Storage & Handling Recommendations
- Store in a dry, well-ventilated indoor environment; avoid contact with carbon steel to prevent galvanic contamination.
- Protect coils from mechanical damage during transport; use non-ferrous slings (nylon or synthetic fiber) for lifting.
- Maintain original protective wrapping until point of installation to preserve surface integrity.
- Recommended maximum storage duration: 24 months under controlled conditions.
Note: All specifications listed herein are subject to continuous improvement and may be updated without prior notice. Customers requiring exact compliance with specific project requirements should submit detailed technical drawings and applicable code references for formal quotation and production scheduling.