Stainless Steel Helical Coil Tube — Product Technical Specification
1. Product Overview
The Stainless Steel Helical Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. through advanced helical coil forming processes. This product is characterized by its continuous spiral geometry, which provides a significantly larger heat transfer surface area relative to its occupied volume compared to conventional straight tubing. The Coil Tube is fabricated from high-grade austenitic stainless steel and is designed for demanding thermal exchange, fluid distribution, and structural applications across multiple industrial sectors.
The product designation Coiltube (Catalog No. 1360) encompasses a family of helically wound stainless steel tubes that may be supplied in either pre-formed coil configurations or as straightened sections depending on the end-use requirements. The spiral geometry is produced through controlled cold or hot forming techniques that maintain material integrity and dimensional precision throughout the winding process.
2. Material & Properties
The Coil Tube is manufactured from premium austenitic stainless steel grades selected for their exceptional corrosion resistance, mechanical strength, and thermal performance. The primary material grades include:
- ASTM 304 (UNS S30400 / 06Cr19Ni10): The standard grade offering excellent general corrosion resistance, formability, and weldability. Chromium content ≥18%, Nickel content ≥8%.
- ASTM 316 (UNS S31600 / 022Cr19Ni10Mo): Enhanced resistance to pitting and crevice corrosion due to the addition of 2–3% Molybdenum (Mo), making it suitable for aggressive chemical environments.
- ASTM 321 (UNS S32100 / 06Cr18Ni11Ti): Titanium-stabilized grade providing superior resistance to intergranular corrosion at elevated temperatures (450–850°C).
- ASTM 316L (UNS S31603 / 022Cr17Ni12Mo2): Low-carbon variant of 316 with improved weldability and resistance to sensitization.
Mechanical Properties (Typical Values for ASTM 304 Grade)
- Tensile Strength (UTS): ≥515 MPa (75,000 psi)
- Yield Strength (0.2% Offset): ≥205 MPa (29,700 psi)
- Elongation (in 50 mm / 2"): ≥40%
- Hardness (Brinell): ≤217 HB
- Thermal Conductivity (at 100°C): 16.3 W/(m·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (⅛" – 2") | ASTM A269 / ASME SA-269 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm (0.012" – 0.118") | ASTM A269 / ASME SA-269 |
| Helical Coil Pitch | 5.0 mm – 25.0 mm (adjustable per design) | Custom / ISO 14224 |
| Coil Diameter (Helix Diameter) | 25 mm – 500 mm (per application requirement) | Custom |
| Tube Length (per coil / per section) | Up to 100 m (continuous); straightened sections up to 12 m | Custom |
| Surface Finish | Pickled & Passivated (P&P), Mirror Polish (Ra ≤ 0.05 μm), Brushed | ASTM A270 / ASME SA-270 |
| End Condition | Plain, Beveled, Threaded, Flanged, or Weld-Prepared | ASME B16.11 / B16.5 |
| Operating Temperature Range | −196°C to +870°C (grade-dependent) | ASTM A269 |
| Pressure Rating | Up to 40 MPa (5,800 psi) — PN40 class | EN 10217 / ASME B31.3 |
| Tolerance on OD | ±0.1 mm or ±0.15% (whichever is greater) | ASTM A269 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A269 |
| Applicable Standards | ASTM A269, A270, A213; ASME SA-269, SA-270, SA-213; EN 10217-7; GB/T 12771 | — |
4. Manufacturing Process
The production of Stainless Steel Helical Coil Tubes follows a rigorous multi-stage manufacturing workflow that ensures dimensional accuracy, material integrity, and surface quality. The process is grounded in research on Helical Coil Forming Technology (螺旋盘管成型工艺), which addresses the complex mechanics of plastic deformation during spiral winding.
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel seamless or welded tubes are verified against material certificates (Mill Test Certificates, MTC) for chemical composition, mechanical properties, and dimensional compliance. Ultrasonic testing (UT) and eddy current testing (ECT) are performed to detect internal and surface defects.
- Pre-Treatment & Annealing: Tubes are subjected to solution annealing (1050–1150°C) followed by rapid quenching to achieve a uniform austenitic microstructure. This step eliminates residual stresses from prior cold working and ensures optimal formability.
- Precision Sizing: The tubes pass through a series of calibrated sizing rollers to achieve the exact outer diameter and wall thickness tolerances required for the final coil geometry.
- Helical Coil Forming (核心工艺 — Core Process): The tube is guided through a numerically controlled (CNC) spiral winding machine. Key process parameters include:
- Winding Angle: Controlled to maintain uniform helix pitch and prevent ovalization.
- Bend Radius: Set to avoid excessive plastic strain that could lead to cracking or thinning.
- Tension Control: Active tension systems maintain constant tube tension to prevent buckling or kinking during the spiral winding operation.
- Tooling Geometry: Precision-machined forming dies and guide rollers ensure consistent cross-sectional shape throughout the coil.
- Post-Forming Stress Relief: Following helical forming, the coil tube undergoes stress relief annealing (typically 400–500°C) to reduce residual stresses introduced during the forming process, thereby improving dimensional stability and fatigue resistance.
- Pickling & Passivation: The formed coil tube is immersed in a pickling solution (dilute nitric acid and hydrofluoric acid mixture) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide (Cr₂O₃) surface layer. This ensures long-term corrosion resistance.
- Surface Finishing: Depending on the application, the tube surface may undergo additional finishing including electropolishing, mechanical polishing, or chemical mirror polishing to achieve surface roughness values as low as Ra ≤ 0.05 μm.
- Quality Inspection & Testing:
- Dimensional inspection using laser measuring systems and coordinate measuring machines (CMM).
- Hydrostatic pressure testing at 1.5× the design pressure.
- Helium leak testing for hermeticity-critical applications.
- Visual and dye penetrant inspection (PT) for surface defects.
- Chemical analysis verification via optical emission spectrometry (OES).
- Packaging & Delivery: Coils are wrapped in protective film, placed on wooden pallets or steel cradles, and shipped in moisture-proof packaging to prevent handling damage and atmospheric corrosion.
4.2 Key Forming Technology Insights
The helical coil forming process involves complex multiaxial stress states at the bending zone, where the tube experiences simultaneous tension, compression, and torsion. Research into this process has identified critical parameters that govern forming quality:
- Minimum Bend Diameter Ratio (D/t): The ratio of the helix inner diameter to the tube wall thickness must exceed a critical threshold (typically D/t ≥ 8 for austenitic stainless steel) to prevent wall thinning beyond acceptable limits and to avoid cracking on the outer curvature.
- Ovalization Control: The ellipticity (ovalization) of the tube cross-section at the bend is a critical quality metric. Advanced forming tools with segmented roller profiles are employed to minimize ovalization to ≤5% of nominal diameter.
- Work Hardening Effects: Austenitic stainless steels exhibit significant strain hardening during cold forming. Process parameters are optimized to keep the accumulated plastic strain within the ductile range, ensuring the final product retains adequate formability for subsequent installation operations (e.g., tube bending, welding).
5. Applications
The Stainless Steel Helical Coil Tube finds extensive application across multiple industries due to its superior heat transfer efficiency, compact geometry, and corrosion resistance:
- Heat Exchangers & Heat Transfer Systems: Spiral wound heat exchangers, air-to-liquid heat exchangers, condensers, evaporators, and refrigeration coils. The helical geometry enhances turbulence and convective heat transfer coefficients, achieving up to 30% higher thermal performance compared to straight tube designs.
- Chemical & Petrochemical Industry: Reactor internals, distillation column packing, heat tracing systems, and process piping where corrosion resistance is paramount. Grades 316 and 316L are preferred for handling aggressive chemicals such as sulfuric acid, hydrochloric acid, and caustic solutions.
- Food & Beverage Processing: Sanitary-grade heat exchangers for pasteurization, sterilization, and thermal processing of food and dairy products. Mirror-polished surfaces (Ra ≤ 0.05 μm) comply with FDA and 3-A Sanitary Standards.
- Pharmaceutical Industry: CIP/SIP (Clean-in-Place / Sterilize-in-Place) compatible heat exchange systems for pharmaceutical manufacturing. The smooth surface finish prevents microbial adhesion and biofilm formation.
- Power Generation: Boiler tube bundles, economizers, and air preheaters in coal-fired, gas-fired, and nuclear power plants. Grade 321 is utilized in high-temperature furnace applications.
- Automotive & HVAC: Radiator cores, condenser coils, and evaporator assemblies for vehicle thermal management systems and building climate control.
- Oil & Gas: Subsea heat exchangers, platform cooling systems, and offshore process piping where resistance to seawater corrosion and high-pressure operation are critical.
- Electronic Cooling: Compact spiral heat exchangers for high-power electronics, data center cooling, and battery thermal management systems in electric vehicles.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System Certification, ensuring consistent product quality and customer satisfaction.
- ISO 14001:2015 — Environmental Management System Certification, demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System Certification.
- CE Marking — Conformity with European directives for pressure equipment (PED 2014/68/EU) where applicable.
- ASME Stamp — Authorization for fabrication of pressure-containing components per ASME Boiler and Pressure Vessel Code (Section VIII, Division 1).
- NACE MR0175 / ISO 15156 — Compliance for use in sour service environments (hydrogen sulfide-containing) where applicable grades are specified.
- EN 10204 3.1 / 3.2 — Material Test Certificate Type 3.1 (inspection certificate) or Type 3.2 (inspection statement) provided with each shipment, issued by an authorized inspector.
All production batches are subject to a full traceability system, with each coil tube lot linked to its raw material heat number, processing parameters, and inspection records. This ensures complete quality traceability from raw material through to the final delivered product.
7. Unique Selling Points
- Research-Driven Manufacturing: The production process is informed by dedicated research into helical coil forming mechanics (螺旋盘管成型工艺研究), resulting in optimized forming parameters that minimize defects and maximize product reliability.
- High Thermal Efficiency: The helical geometry inherently promotes turbulent flow within the tube, enhancing heat transfer coefficients and enabling more compact heat exchanger designs with reduced footprint.
- Full Grade Availability: Complete range of austenitic stainless steel grades (304, 316, 321, 316L, and custom alloys) available to match specific corrosion and temperature requirements.
- Precision Dimensional Control: CNC-controlled forming equipment ensures tight tolerances on helix pitch, coil diameter, and tube geometry, facilitating seamless integration into engineered systems.
- Superior Surface Quality: Capabilities for mirror polishing to Ra ≤ 0.05 μm meet the most stringent sanitary and pharmaceutical surface requirements.
- Customization Flexibility: Tailored coil geometries, end preparations, surface finishes, and material specifications to meet unique customer engineering requirements.
8. Technical Support & Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including thermal performance calculations, stress analysis, material selection guidance, and installation recommendations. Customers are encouraged to provide detailed application parameters (operating temperature, pressure, fluid type, corrosion environment, and dimensional requirements) to enable optimal product specification and selection.
Product Catalog Reference: Catalog No. 1360 — Stainless Steel Helical Coil Tube (Coiltube)
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Technical Classification: Literature & Learning Reference — Helical Coil Forming Technology Research