Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed into continuous helical coils, specifically designed for thermal-fluid exchange applications including fan coil units (FCUs), air handling units (AHUs), and industrial heat exchanger systems. The product is supplied in coil form to facilitate seamless integration into downstream forming, bending, and assembly operations, minimizing material waste and reducing fabrication time.
This product line encompasses austenitic and duplex stainless steel coil tubes engineered to withstand aggressive chemical environments, high thermal cycling, and sustained mechanical loads. The coil configuration enables efficient storage, transportation, and downstream processing through automated coil-to-straight-line conversion systems.
2. Material Composition & Properties
2.1 Chemical Composition (Typical)
| Grade | C (%) | Mn (%) | Si (%) | Cr (%) | Ni (%) | Mo (%) | N (%) | Fe (Balance) |
|---|---|---|---|---|---|---|---|---|
| 304 (UNS S30400) | ≤0.08 | ≤2.00 | ≤1.00 | 18.0–20.0 | 8.0–10.5 | — | — | Balance |
| 316L (UNS S31603) | ≤0.03 | ≤2.00 | ≤1.00 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | Balance |
| Duplex 2205 (UNS S32205) | ≤0.030 | ≤2.00 | ≤1.00 | 22.0–23.0 | 4.0–7.0 | 3.0–3.5 | 0.14–0.20 | Balance |
2.2 Mechanical Properties (Annealed Condition)
| Property | 304 | 316L | Duplex 2205 |
|---|---|---|---|
| Tensile Strength (Rm, MPa) | 515–720 | 485–720 | ≥550 |
| Yield Strength (Rp0.2, MPa) | ≥205 | ≥170 | ≥450 |
| Elongation (A50, %) | ≥40 | ≥40 | ≥25 |
| Hardness (HV) | ≤200 | ≤190 | ≤310 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 14.6 | — |
2.3 Corrosion Resistance
- Pitting Resistance Number (PREN): 304: 18–20; 316L: 24–26; Duplex 2205: 32–34
- Intergranular Corrosion: All grades comply with ASTM A240/A479 intergranular corrosion test requirements (3% HCl–HNO3 immersion test)
- Stress Corrosion Cracking (SCC) Resistance: 316L and Duplex 2205 demonstrate superior resistance in chloride-containing environments per ASTM G48
3. Dimensions & Specifications
| Parameter | Specification | Tolerance / Standard |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ±0.10 mm (ASTM A213 / EN 10216-5) |
| Wall Thickness (WT) | 0.50 mm – 3.00 mm | ±10% of nominal (or ±0.05 mm, whichever is greater) |
| Coil Pitch | 15 mm – 100 mm (customizable) | ±1.0 mm |
| Coil Inner Diameter (CID) | 200 mm – 600 mm | ±5 mm |
| Coil Length (Uncoiled) | 5 m – 200 m (customizable) | ±2% |
| Surface Finish | No.1 (Pickled), 2B, BA (Bright Annealed), Hairline | Per ASTM A479 / EN 10216-5 |
| Maximum Wall Thickness Ratio (OD/WT) | ≤ 20:1 | — |
| Maximum Working Pressure (Design) | Up to 16 bar (grade-dependent) | ASME B31.3 / EN 13480 |
| Operating Temperature Range | −196°C to +650°C (304); −196°C to +425°C (316L); −196°C to +350°C (Duplex) | — |
4. Manufacturing Process
- Raw Material Selection: High-purity stainless steel slabs or ingots from certified mills, with full chemical composition verification via Optical Emission Spectroscopy (OES) and mass spectrometry.
- Hot Rolling: Slabs are reheated to 1150°C–1250°C and hot-rolled into seamless tube blanks or ERW (Electric Resistance Welded) base pipe, depending on the target grade and dimensions.
- Heat Treatment (Solution Annealing): Tubes are austenitized at 1010°C–1150°C followed by rapid water quenching to achieve full solution treatment, ensuring carbide dissolution and optimal corrosion resistance. For 316L, stabilization at 870°C–900°C with controlled cooling prevents sensitization.
- Precision Cold Drawing: Tubes are cold-drawn through tungsten carbide (WC-Co) dies to achieve final OD and wall thickness within tight tolerances. Multi-pass drawing ensures dimensional accuracy and improved surface finish.
- Pickling & Passivation: Tubes undergo pickling in a mixed HNO3/H2SO4 bath to remove scale and oxidation, followed by passivation treatment to form a stable chromium oxide protective layer.
- Coil Forming: Straight tubes are fed through a CNC-controlled coiling head that forms precise helical coils with controlled pitch and diameter. The coiling process employs tension-controlled feed to prevent ovality, kinking, or springback.
- Final Inspection: Each coil undergoes non-destructive testing (NDT) including eddy current inspection (per ASTM E309), hydrostatic pressure testing (per ASTM A213), and visual surface inspection.
5. Applications
- Fan Coil Units (FCU): Primary application — coil tubes serve as refrigerant/heat-transfer fluid channels in commercial HVAC fan coil systems, requiring precise coil geometry for optimal air-side heat transfer efficiency.
- Air Handling Units (AHU): Heating and cooling coils in large-scale HVAC systems.
- Industrial Heat Exchangers: Shell-and-tube, plate-fin, and spiral heat exchanger applications in chemical processing, food & beverage, and pharmaceutical industries.
- Refrigeration & Air Conditioning: Evaporator and condenser coils in commercial refrigeration systems.
- Marine & Offshore Systems: Seawater cooling coils in marine propulsion and power generation systems, leveraging 316L and Duplex 2205 corrosion resistance.
- Food Processing Equipment: Sanitary-grade heat transfer coils in pasteurization, UHT (Ultra-High Temperature) processing, and dairy equipment.
- Energy Systems: Solar thermal collector tubes and geothermal heat exchange coils.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — certified manufacturing process |
| ISO 14001:2015 | Environmental Management System |
| CE Marking (EU) | Compliance with European pressure equipment directive (PED 2014/68/EU) |
| EN 10204 3.1 | Material Test Report — independent third-party inspection |
| ASTM A213 / A269 | Standard specifications for seamless and welded austenitic stainless steel tubes |
| ASME SA-213 / SA-269 | American Society for Mechanical Engineers boiler and heat exchanger tube standards |
| EN 10216-5 | European standard for pressure tubes — heat exchanger tubes |
| NSF/ANSI 61 | Drinking water system components — health effects certification (where applicable) |
| 3-A Sanitary Standards | Food-grade surface finish and design compliance (BA finish) |
7. Unique Selling Points
- Precision Coil Geometry: CNC-controlled coiling ensures pitch accuracy within ±1.0 mm, critical for downstream heat exchanger assembly and optimal thermal performance in fan coil unit applications.
- Multi-Grade Capability: Full product range spanning austenitic (304, 316L), super-austenitic (904L), and duplex (2205, 2507) stainless steels to address diverse corrosion and mechanical requirements.
- Integrated Traceability: Each coil is laser-marked with heat number, grade, dimensions, and production date for full supply chain traceability per ISO 9001 requirements.
- Custom Engineering: Bespoke coil pitch, length, and geometry configurations available to match specific OEM (Original Equipment Manufacturer) design requirements for FCU and AHU applications.
- Performance-Verified: Product performance validated through fan coil unit testing protocols per AHRI 210/240 and EN 12830 standards, with documented heat transfer coefficient (U-value) data available upon request.
- Cost-Efficient Supply: Coil format reduces cutting waste by up to 30% compared to cut-length tube supply, offering significant material cost savings for high-volume fabrication.
8. Packaging & Delivery
- Coils are wrapped in protective polyethylene film with interlayer kraft paper to prevent surface damage.
- Outer packaging: VCI (Vapor Corrosion Inhibitor) treated shrink wrap with wooden pallet base and steel banding.
- Each coil accompanied by EN 10204 Type 3.1 material certificate, dimensional inspection report, and NDT results.
- Shipping: Export-grade palletized coils suitable for containerized (20'/40') or break-bulk ocean freight.