Stainless Steel Coil Tube (Coiltube) — Thermal Performance Grade
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered continuous spiral-wound tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed primarily for heat exchange, evaporation, and condensation systems, this product series integrates high-performance austenitic stainless steel with advanced coiling geometry to deliver superior thermal transfer efficiency, mechanical durability, and corrosion resistance in demanding industrial environments.
The coil tube architecture represents a significant advancement in heat exchanger design, offering a high surface-area-to-volume ratio that maximizes thermal contact between process fluids and the working medium. Through rigorous three-dimensional numerical simulation of thermal characteristics (as documented in Three-Dimensional Numerical Simulation of Thermal Performance of Coiled Tube Evaporators), the geometric parameters and material selection have been optimized to achieve peak heat transfer coefficients while minimizing pressure drop and flow maldistribution.
2. Material & Properties
2.1 Base Alloy Composition
The Coiltube is fabricated from premium austenitic stainless steel grades, selected for their exceptional combination of corrosion resistance, thermal conductivity, and formability at both ambient and elevated temperatures. The primary material grades include:
- SAE 304 (UNS S30408) — General-purpose austenitic stainless steel with balanced corrosion resistance and weldability
- SAE 316L (UNS S31603) — Low-carbon variant with molybdenum addition for enhanced resistance to pitting and crevice corrosion
- SAE 321 (UNS S32100) — Stabilized grade with titanium addition for resistance to sensitization at elevated temperatures
2.2 Key Mechanical and Physical Properties
| Property | SAE 304 | SAE 316L | SAE 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (0.2% offset, MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (% at break) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 | 16.3 |
| Thermal Expansion (×10⁻⁶/K, 20–100°C) | 17.3 | 17.1 | 17.3 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 |
| Maximum Service Temperature (°C) | 870 | 870 | 980 |
| Corrosion Resistance (Pitting) | Moderate | Excellent | Moderate |
2.3 Surface Finish Options
- 2B Finish — Cold-rolled, annealed, and skin-passed; standard general-purpose surface
- No. 4 Brushed Finish — Uniformly directional grain; suitable for decorative and mild-corrosion environments
- No. 8 Mirror Finish — Polished to reflectivity; reduces fouling and biofilm adhesion in hygienic applications
- Electro-polished Surface — Removes surface roughness to Ra ≤ 0.2 μm; critical for pharmaceutical and food-grade use
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Material Grade | SAE 304 / 304L / 316 / 316L / 321 |
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") |
| Wall Thickness | 0.3 mm – 3.0 mm |
| Coil Pitch (Center-to-Center) | 5 mm – 50 mm (adjustable per design) |
| Coil Diameter (OD of Coil) | 100 mm – 2000 mm |
| Coil Length | 1 m – 50 m (continuous or segmented) |
| Manufacturing Standard | ASTM A213 / ASTM A269 / EN 10217-7 / GB/T 12771 |
| Pressure Rating | Up to 25 MPa (PN25), dependent on wall thickness and temperature |
| Operating Temperature Range | −196°C to +870°C (cryogenic to high-temperature) |
| Tolerance on OD | ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% of nominal |
| End Form | Plain / Beveled / Threaded / Flanged / Brazed |
4. Manufacturing Process
4.1 Raw Material Preparation
Production begins with the selection of certified stainless steel strip or seamless tubing from approved mill suppliers. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition within the tight tolerances specified by the applicable ASTM or EN standard. Mechanical property verification is performed through tensile testing and hardness measurement prior to any forming operations.
4.2 Precision Coiling / Winding
The core manufacturing step involves the controlled spiral coiling of the tube stock. This process is executed using CNC-controlled coiling machines that maintain precise control over:
- Coil pitch accuracy — Ensuring uniform spacing between adjacent turns to promote consistent fluid distribution and heat transfer
- Wall thickness integrity — Preventing thinning or thickening at bend radii through optimized die geometry and lubrication
- Dimensional consistency — Maintaining coil diameter tolerance within ±1% of nominal
4.3 Heat Treatment and Stress Relief
Following coiling, the assembly is subjected to solution annealing (typically at 1050°C – 1150°C) followed by controlled cooling. This process:
- Relieves residual stresses introduced during cold forming
- Restores full austenitic microstructure and maximum ductility
- Enhances corrosion resistance by dissolving any carbide precipitation at grain boundaries
- Ensures consistent mechanical properties throughout the component
4.4 Surface Treatment and Finishing
Post-annealing surface treatment includes pickling and passivation to remove oxide scale and establish a protective chromium oxide layer. For applications requiring enhanced cleanliness or corrosion resistance, additional electro-polishing or chemical passivation treatments are applied.
4.5 Quality Inspection and Testing
Every coil tube production batch undergoes comprehensive inspection including:
- Dimensional verification — Laser scanning for coil geometry, pitch, and diameter conformity
- Hydrostatic pressure testing — At 1.5× design pressure for minimum 30 seconds with zero leakage
- Non-destructive testing (NDT) — Eddy current and/or ultrasonic inspection for wall thickness uniformity and internal defect detection
- Surface quality assessment — Visual and profilometric evaluation of surface finish
- Chemical spot-check — Spectroscopic verification of material grade
5. Applications
The Stainless Steel Coil Tube is engineered for a broad spectrum of industrial and commercial applications where thermal efficiency, corrosion resistance, and reliability are paramount:
5.1 Heat Exchangers and Evaporators
Primary application domain. The coiled geometry provides exceptional heat transfer surface density, making it ideal for shell-and-coil heat exchangers, evaporator bundles, condensers, and reboilers in chemical processing, petrochemical, and power generation plants.
5.2 Refrigeration and Cryogenic Systems
SAE 316L and SAE 304 coil tubes are extensively used in refrigeration evaporators, air conditioning systems, and cryogenic fluid handling equipment where low-temperature ductility and non-magnetic properties are required.
5.3 Pharmaceutical and Food Processing
Electro-polished coil tubes meet FDA and 3-A sanitary standards, suitable for pasteurization, sterilization (SIP/CIP), and clean-in-place systems where product purity and hygienic design are critical.
5.4 Power Generation
Used in steam generators, feedwater heaters, and condensate recovery systems in both conventional and nuclear power plants, where SAE 321 grade provides resistance to thermal sensitization at sustained elevated temperatures.
5.5 Marine and Offshore Engineering
SAE 316L coil tubes deliver superior resistance to chloride-induced pitting and crevice corrosion in seawater environments, making them suitable for shipboard cooling systems, desalination plants, and offshore platform heat exchangers.
5.6 Oil and Gas Industry
Applied in subsea production systems, separator internals, and gas processing heat exchangers where resistance to sour gas (H₂S) environments and high-pressure operation are essential.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for manufacturing excellence
- ISO 14001:2015 — Environmental Management System certification
- ASME Stamp — Authorized fabrication of pressure-containing components per ASME Boiler and Pressure Vessel Code
- CE Marking — Compliance with European Pressure Equipment Directive (PED 2014/68/EU)
- EN 10204 3.1 — Third-party material test certificates provided for every production lot
- NORSOK M-650 — Compliance for oil and gas industry applications
- 3-A Sanitary Standards — For food and dairy processing applications
- FDA Compliance — For pharmaceutical and food-contact applications
Quality Commitment: Every Coiltube product is accompanied by a full material traceability dossier including mill test certificates, heat number identification, chemical composition analysis, mechanical property test reports, and dimensional inspection records. Wenzhou Jixing Metal Materials Co., Ltd adheres to a policy of zero-defect delivery, supported by statistical process control (SPC) monitoring throughout the manufacturing lifecycle.
7. Unique Selling Points
- Simulation-Optimized Geometry — Coil pitch, diameter, and tube dimensions are validated through 3D CFD thermal simulation, ensuring peak heat transfer performance with minimized pressure drop
- Cryogenic to High-Temperature Versatility — Single product family spans −196°C to +870°C service conditions through appropriate grade selection
- Full Traceability — Heat-number-based material tracking from mill to finished coil ensures complete supply chain transparency
- Custom Engineering Capability — Tailored coil geometries, end treatments, and surface finishes available to meet specific project requirements
- Multi-Standard Compliance — Simultaneous compliance with ASTM, EN, ASME, and GB standards provides global project flexibility