Stainless Steel Spiral Coil Tube — Product Technical Specification
1. Product Overview
The Stainless Steel Spiral Coil Tube (Product No. 1078) is a precision-engineered coiled tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product represents the culmination of advanced coil bending technology, combining material science with geometric precision to deliver high-performance tubing solutions for demanding industrial applications. The spiral coil tube is formed through a controlled bending process that maintains dimensional integrity, metallurgical stability, and surface quality throughout the entire manufacturing cycle.
Unlike standard straight-length stainless steel tubing, spiral coil tubes offer unique advantages in thermal exchange efficiency, space utilization, and fluid dynamics performance. The "skillful bending" (巧弯) methodology employed by Wenzhou Jixing ensures that each coil maintains consistent curvature, uniform wall thickness, and free of work-hardening-induced microstructural degradation — critical factors for long-term service reliability in corrosive and high-temperature environments.
2. Material & Properties
2.1 Base Material Grades
The stainless steel spiral coil tube is available in a comprehensive range of austenitic, ferritic, and duplex stainless steel grades, selected to meet specific application requirements:
- Austenitic Grades: SUS304 / AISI 304, SUS316 / AISI 316, SUS316L, SUS321, SUS347, SUS904L
- Ferritic Grades: SUS430, SUS444, SUS409
- Duplex Grades: SUS2205 (UNS S32205), SUS2507 (UNS S32750)
2.2 Key Mechanical Properties (Typical — SUS316L)
- Tensile Strength (UTS): ≥ 485 MPa (70,300 psi)
- Yield Strength (0.2% Offset): ≥ 205 MPa (29,700 psi)
- Elongation at Break: ≥ 40%
- Hardness: ≤ 250 HB (Brinell)
- Density: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 25°C
- Coefficient of Thermal Expansion: 16.0 × 10⁻⁶ /°C (20–100°C)
2.3 Corrosion Resistance
The coil bending process at Wenzhou Jixing is designed to preserve the passive chromium oxide film on the tube surface. Post-bending passivation treatment ensures that the Pitting Resistance Equivalent Number (PREN) is maintained at or above specification levels. For SUS316L, the PREN value exceeds 24, providing excellent resistance to chloride-induced pitting and crevice corrosion.
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Tube Outer Diameter (OD) | Φ6.0 mm – Φ159.0 mm (1/4" – 6") | ASTM A554 / ASME SA-554 |
| Wall Thickness | 0.5 mm – 6.0 mm | ASTM A269 / ASME SA-269 |
| Coil Outer Diameter (C-OD) | 100 mm – 2,000 mm (adjustable) | Customer specification |
| Coil Length (per bundle) | 5 m – 500 m | Customer specification |
| Bend Radius (minimum) | ≥ 3D (D = tube outer diameter) | ASME B31.3 / B31.9 |
| Spiral Pitch | 15 mm – 200 mm (customizable) | Customer specification |
| Number of Turns | 10 – 5,000+ (per coil assembly) | Customer specification |
| Surface Finish | 2B, BA (Bright Annealed), No. 4, No. 8 Mirror, Custom | ASTM A403 / A666 |
| End Form | Plain, Beveled, Threaded, Flanged, Weld-prep | ASME B16.5 / B16.11 |
| Tolerance — OD | ±0.05 mm (precision) / ±0.10 mm (standard) | ASTM A554 |
| Tolerance — Wall Thickness | ±10% (standard) / ±5% (precision) | ASTM A269 |
| Applicable Standards | ASTM, ASME, EN, DIN, JIS, GB/T | — |
| Operating Temperature Range | −196°C to +1,150°C (grade-dependent) | ASME BPVC Section VIII |
| Maximum Working Pressure | Up to 420 bar (grade & geometry dependent) | ASME BPVC Section VIII Div.1 |
4. Manufacturing Process
The production of the Stainless Steel Spiral Coil Tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorously controlled multi-stage process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
4.1 Process Flow
- Material Selection & Inspection: Raw stainless steel strip or seamless tube stock is received with full mill certification. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition within ASTM/EN specification limits.
- Coil Winding Preparation: The tube blank is stress-relieved through controlled annealing (solution treatment at 1,050–1,150°C for austenitic grades) to eliminate residual stresses from prior cold working.
- Induction Heating (if applicable): For larger diameter tubes requiring enhanced formability, localized induction heating is applied to the bend zone, raising the temperature to the optimal plastic deformation range (900–1,050°C) without compromising the overall microstructure.
- Spiral Coil Bending: The core "skillful bending" (巧弯) operation utilizes CNC-controlled mandrel bending machines with synchronized feed and rotation. The bending parameters — bend radius, angular velocity, feed rate, and support geometry — are precisely calibrated to each tube specification to prevent:
- Wall thinning exceeding 10% at the bend apex
- Surface wrinkling or ovality distortion
- Work hardening exceeding HRC 30 in the bend zone
- Loss of passive film integrity
- Post-Bend Stress Relief: Coiled assemblies undergo controlled thermal stress relief (620–850°C for austenitic grades) to recover ductility and minimize residual stresses that could lead to stress corrosion cracking (SCC).
- Passivation & Surface Treatment: Nitric acid or citric acid passivation is applied to restore and enhance the chromium oxide passive layer. Surface finishing (polishing, electropolishing) is performed to achieve specified surface roughness (Ra ≤ 0.2 μm for sanitary applications).
- Final Inspection & Testing: Comprehensive quality verification includes dimensional measurement (laser scanning), visual inspection, dye penetrant testing (PT) for surface defects, and hydrostatic pressure testing at 1.5× working pressure for a minimum hold time of 60 seconds.
4.2 Process Control Highlights
The "Skillful Spiral Coil Bending" methodology developed by Wenzhou Jixing incorporates real-time monitoring of bending force, angular velocity, and tube deformation through integrated sensors and PLC control systems. This closed-loop process control ensures that each coil tube meets tight tolerance specifications regardless of batch size, achieving a first-pass yield rate exceeding 99.2%.
5. Applications
The Stainless Steel Spiral Coil Tube finds extensive application across multiple high-performance industries:
5.1 Industrial Applications
- Heat Exchangers & Radiators: Spiral coil geometry maximizes surface-to-volume ratio, enhancing thermal exchange efficiency in shell-and-coil heat exchangers, air-cooled condensers, and evaporators.
- Oil & Gas Industry: Used in subsea production systems, flow lines, gas lift manifolds, and heat tracing systems where corrosion resistance and pressure integrity are paramount.
- Chemical Processing: Reactor cooling coils, heat exchanger bundles, and process piping in aggressive chemical environments (acids, alkalis, chlorides).
- Food & Beverage Industry: Pasteurization systems, milk processing heat exchangers, brewing systems, and pharmaceutical CIP/SIP (Clean-in-Place / Sterilize-in-Place) systems.
- Petrochemical & Refining: Crude oil preheaters, distillation column internals, and heat recovery units.
- Power Generation: Boiler economizer tubes, superheater coils, condenser tubes, and heat recovery steam generators (HRSG).
- Automotive & Aerospace: Turbocharger cooling circuits, fuel system lines, and hydraulic actuator assemblies.
- Marine Engineering: Seawater cooling systems, ballast water treatment, and marine heat exchangers.
- HVAC & Refrigeration: Chiller coils, condenser tubes, and refrigerant circuit coils.
- Medical Devices: Dialysis equipment, medical gas lines, and sterilization system components.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product compliance with international standards:
6.1 Quality Management Systems
- ISO 9001:2015 — Quality Management Systems (QMS)
- ISO 14001:2015 — Environmental Management Systems (EMS)
- ISO 45001:2018 — Occupational Health & Safety Management
6.2 Product & Industry Certifications
- NADCAP (National Aerospace and Defense Contractors Accreditation Program) — for aerospace-grade coil bending operations
- API Monogram (American Petroleum Institute) — for oil & gas industry products
- EN 10204 3.1 / 3.2 — Material Test Reports (MTR) with independent third-party verification
- ASME "U" Stamp — Pressure Vessel and Piping certification
- WRAS / W3 — Water Regulations Advisory Scheme (for potable water applications)
- NSF/ANSI 61 — Drinking Water System Components
- PED 2014/68/EU — Pressure Equipment Directive compliance (European market)
- CRN (Canadian Registration Number) — for Canadian pressure equipment
6.3 Testing & Inspection Protocols
| Test Method | Standard | Purpose |
|---|---|---|
| Hydrostatic Pressure Test | ASTM A269 / ASME SA-269 | Leak integrity verification |
| Dye Penetrant Testing (PT) | ASTM E709 / ISO 3452 | Surface defect detection |
| Magnetic Particle Testing (MT) | ASTM E1444 / ISO 9934 | Surface & near-surface defect detection (ferritic/duplex) |
| Chemical Composition Analysis (OES) | ASTM E1968 | Grade verification |
| Mechanical Testing (Tensile, Hardness) | ASTM E8 / E10 / E92 | Property verification |
| Intergranular Corrosion Test (IGC) | ASTM A262 Practice E / A / B | Weld sensitization assessment |
| Pitting Corrosion Test | ASTM G48 | Chloride pitting resistance |
| Dimensional Inspection | ASTM A554 / ASME SA-554 | Geometric accuracy verification |
| Surface Roughness Measurement | ASTM B466 / ISO 4287 | Surface finish verification |
7. Unique Selling Points
- Precision Spiral Geometry: Proprietary CNC bending technology achieves spiral pitch tolerances of ±0.5 mm and bend radius consistency of ±1%, enabling superior heat transfer performance and seamless integration into compact system designs.
- Metallurgical Integrity Preservation: Advanced process control prevents work hardening, microstructural degradation, and passive film disruption during the coil forming operation, ensuring the final product retains full material performance characteristics.
- Multi-Grade Capability: Manufacturing capability across austenitic, ferritic, and duplex stainless steel grades provides customers with a single-source solution for diverse corrosion and mechanical requirements.
- Custom Engineering Support: Full design-to-delivery capability including CAD modeling, finite element analysis (FEA) of coil stress distribution, thermal simulation, and prototyping for bespoke applications.
- Traceability & Documentation: Complete material traceability from mill heat number through final product, with comprehensive test documentation (EN 10204 3.1/3.2) for regulatory and project compliance.
- Scalable Production: Capacity to produce from prototype quantities to high-volume production runs without compromising quality consistency.
8. Conclusion
The Stainless Steel Spiral Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a premium engineered product combining advanced materials science, precision manufacturing technology, and rigorous quality assurance. The company's expertise in the "skillful spiral coil bending" methodology ensures that each product delivers optimal performance in thermal efficiency, mechanical integrity, and corrosion resistance — making it the preferred choice for demanding industrial applications worldwide.