Stainless Steel Spiral Coil Tube — Product Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Coil Tube (Spiral-Wound Heat Exchange Tubing)
Document Reference: No. 227 — Technical Literature Study Series
1. Product Overview
The Stainless Steel Spiral Coil Tube is a precision-engineered heat exchange component manufactured in continuous coiled form. Unlike straight seamless or welded tubes, coil tubes are formed into helical or spiral geometries during production, enabling compact volumetric heat transfer surfaces with superior thermal-hydraulic performance. This product line is specifically designed for integration into spiral coil-type evaporators, condensers, and other heat exchange assemblies where high surface-area-to-volume ratios, uniform flow distribution, and resistance to mechanical vibration are critical design requirements.
Based on the research framework of "Spiral Coil Evaporator Heat Transfer Performance Enhancement and Multi-Parameter Collaborative Optimization," Wenzhou Jixing Metal Materials Co., Ltd. has developed coil tubes that address key engineering challenges including flow maldistribution, pressure drop optimization, fouling resistance, and long-term material integrity under cyclic thermal loading.
2. Material Composition & Properties
2.1 Available Material Grades
- AISI 304 / UNS S30400 / S30403 — Austenitic stainless steel with excellent general corrosion resistance; the most widely specified grade for food-grade and chemical process applications.
- AISI 304L / UNS S30403 — Low-carbon variant of 304 offering enhanced weldability and resistance to intergranular corrosion.
- AISI 316 / UNS S31600 / S31603 — Molybdenum-enhanced austenitic grade providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- AISI 316L / UNS S31603 — Low-carbon variant of 316 for critical welding applications.
- AISI 321 / UNS S32100 / S32101 — Titanium-stabilized grade for elevated temperature service up to 870 °C.
- AISI 347 / UNS S34700 / S34701 — Niobium-stabilized grade for sustained high-temperature applications.
- AISI 310S / UNS S31008 — High-temperature austenitic grade suitable for oxidizing environments up to 1150 °C.
- Duplex 2205 / UNS S31803 / S32205 — Duplex austenitic-ferritic steel offering high strength and excellent chloride stress corrosion cracking (SCC) resistance.
- Super Duplex 2507 / UNS S32750 / S32760 — Ultra-high-strength duplex grade for the most severe corrosive environments.
2.2 Mechanical Properties (Typical — Annealed Condition)
| Property | Grade 304/304L | Grade 316/316L | Duplex 2205 |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 520 MPa | ≥ 550 MPa |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 205 MPa | ≥ 450 MPa |
| Elongation (A5) | ≥ 40 % | ≥ 40 % | ≥ 25 % |
| Thermal Conductivity (20 °C) | 16.3 W/(m·K) | 14.6 W/(m·K) | 18.3 W/(m·K) |
| Maximum Service Temperature | 870 °C | 870 °C | 315 °C (continuous) |
2.3 Chemical Composition Requirements (wt%)
| Element | 304/304L | 316/316L | 2205 |
|---|---|---|---|
| C | ≤ 0.08 / ≤ 0.03 | ≤ 0.08 / ≤ 0.03 | ≤ 0.030 |
| Cr | 18.0 – 20.0 | 16.0 – 18.0 | 22.0 – 23.0 |
| Ni | 8.0 – 10.5 | 10.0 – 14.0 | 4.5 – 6.5 |
| Mo | — | 2.0 – 3.0 | 3.0 – 3.5 |
| N | — | — | 0.14 – 0.20 |
| Si | ≤ 0.75 | ≤ 0.75 | ≤ 1.00 |
| Mn | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
| P | ≤ 0.045 | ≤ 0.045 | ≤ 0.030 |
| S | ≤ 0.030 | ≤ 0.030 | ≤ 0.020 |
3. Product Specifications
3.1 Dimensional Parameters
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | φ 3.0 mm – φ 50.8 mm | ASTM A213 / A269 / EN 10216-5 |
| Wall Thickness (WT) | 0.3 mm – 4.0 mm (tolerance ±10%) | ASTM A213 / A269 |
| Coil Diameter (CD) | φ 200 mm – φ 2,000 mm | Custom / Client-Specified |
| Coil Length | 5 m – 500 m (continuous) | — |
| Helix Pitch | 5 mm – 50 mm (adjustable) | — |
| Number of Turns | Up to 10,000+ turns | — |
| End Preparation | Plain, Beveled (37°/45°), Threaded, Flanged, or Brazed Fitting | ASME B31.3 / EN 1092 |
3.2 Surface Finish Options
| Finish Type | Roughness (Ra) | Application |
|---|---|---|
| Pickle & Passivate (P&P) | 0.4 – 0.8 μm | General chemical, food processing |
| Mechanical Polishing | 0.2 – 0.4 μm | Pharmaceutical, dairy |
| Electropolishing (EP) | 0.05 – 0.2 μm | Biopharmaceutical, ultra-pure fluid service |
| Baer Finish (Bright Annealed) | 0.2 – 0.6 μm | Decorative, architectural |
3.3 Heat Treatment Conditions
- Solution Annealing: 1010 – 1150 °C, followed by rapid water quench
- Stress Relief: 425 – 595 °C, held 1 h per 25 mm thickness, air cool
- Passivation: Per ASTM A967 / ASTM A380, using nitric acid or citric acid solution
4. Manufacturing Process
4.1 Production Flow
- Hot Rolling & Annealing: Stainless steel strip or coil is produced via hot-rolled and cold-rolled processes. Intermediate annealing cycles are performed to control grain structure and mechanical properties.
- Tubular Forming: The flat strip is converted into a seamless tube via either the roll-forming method (for larger diameters) or the extrusion method (for smaller, thinner-walled tubes). Welded coil tubes are produced by transverse or longitudinal welding of precision-cut strip.
- Coil Winding (Spiral Forming): The formed tube is wound onto a precision-controlled mandrel to create the desired helical coil geometry. Computer Numerical Control (CNC) winding machines ensure uniform helix pitch and consistent coil diameter throughout the length. Multi-parameter optimization algorithms govern the winding parameters to minimize residual stress and distortion.
- Welding (for welded coil tubes): Longitudinal weld seams are produced via Argon Arc Welding (TIG / GTAW) or Laser Welding, with continuous visual and automated ultrasonic inspection.
- Heat Treatment: Solution annealing is performed in a vacuum or inert-atmosphere (N2/H2) furnace to restore full austenitic structure, eliminate residual stresses, and ensure maximum corrosion resistance.
- Surface Treatment: Pickle and passivate (P&P) treatment removes oxide scale and forms a protective chromium oxide passive film. Optional electropolishing or mechanical polishing is applied per customer specification.
- Quality Inspection & Testing: Comprehensive dimensional, chemical, mechanical, and non-destructive testing (NDT) is performed before dispatch.
- Marking, Packaging & Dispatch: Each coil is individually marked with heat number, grade, dimensions, and manufacturer identification. Coils are wrapped in moisture-proof film, secured with strapping, and palletized for safe transport.
4.2 Process Quality Controls
- In-line Optical Inspection: Real-time detection of surface defects, dimensional deviations, and weld seam anomalies during coil winding.
- Hydrostatic Pressure Testing: Performed at 1.5× the maximum design pressure per ASTM A213 / EN 10216-5 to verify tube integrity and weld soundness.
- Eddy Current Testing (ECT): For detection of subsurface and surface discontinuities in both seamless and welded tubing.
- Chemical Spectroscopic Analysis: Optical Emission Spectrometry (OES) or X-Ray Fluorescence (XRF) for 100% verification of chemical composition per heat lot.
- Hardness Testing: Vickers hardness (HV) verification per ASTM E92.
- Intergranular Corrosion Testing: Per ASTM A262 Practice No. 1E (for grades susceptible to sensitization).
- Crevice Corrosion Testing: Per ASTM G44 / ASTM G150 for chloride-environment applications.
5. Applications
5.1 Primary Application Domains
- Refrigeration & Air Conditioning (HVAC): Spiral coil tubes serve as the core heat transfer element in evaporators, condensers, and air-cooled heat exchangers. The helical geometry promotes turbulent flow, enhancing the convective heat transfer coefficient (hi) while maintaining manageable pressure drop (ΔP).
- Process Cooling & Heating: Used in shell-and-coil heat exchangers, liquid-to-liquid heat exchangers, and thermal oil systems in chemical, petrochemical, and polymer processing industries.
- Food & Beverage Processing: Sanitary-grade coil tubes (electropolished, 316L) are employed in pasteurization systems, milk cooling coils, brewing heat exchangers, and CIP (Clean-In-Place) compatible systems.
- Pharmaceutical & Biotechnology: High-purity 316L coil tubes with electropolished internal surfaces (Ra ≤ 0.25 μm) are used in bioreactor cooling jackets, sterilizer coils, and ultra-pure water (UPW) distribution systems.
- Power Generation: Coil tubes are utilized in waste heat recovery systems, solar thermal collectors, and geothermal heat exchangers.
- Marine & Offshore: Duplex and super-duplex coil tubes are specified for seawater heat exchangers, ballast water systems, and marine HVAC applications where chloride pitting and SCC resistance are paramount.
- Automotive & Transportation: Compact coil heat exchangers in hybrid/electric vehicle battery thermal management systems and industrial vehicle cooling circuits.
5.2 Performance Enhancement Characteristics
As demonstrated in the referenced study on "Spiral Coil Evaporator Heat Transfer Performance Enhancement and Multi-Parameter Collaborative Optimization," the helical coil geometry inherently induces secondary Dean vortices within the tube flow. These vortices disrupt the thermal boundary layer, resulting in a 20–60% enhancement in the Nusselt number (Nu) compared to straight-tube equivalents at equivalent Reynolds numbers (Re). The multi-parameter optimization framework considers the interplay of coil diameter, tube diameter, helix pitch, fluid velocity, and inlet temperature to maximize the Overall Heat Transfer Coefficient (U) while minimizing pumping power consumption (fcoil · L/D).