Stainless Steel Coil Tube (Coiltube) — Evaporative Cooling Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 246). Designed primarily for evaporative cooling systems and heat exchange applications, this coil tube is formed through advanced cold-rolling and coil-winding techniques to produce a seamless, continuous helical configuration. The product is engineered to ensure optimal surface water distribution uniformity — a critical performance parameter in evaporative cooling environments — across varying pipe diameters and flow configurations.
Coil tubes serve as the fundamental structural and functional element in evaporative coolers, chillers, condensers, and industrial heat exchangers. Their continuous helical geometry maximizes heat transfer surface area while minimizing pressure drop, making them indispensable in both HVAC (Heating, Ventilation, and Air Conditioning) and process engineering applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for superior corrosion resistance, mechanical strength, and thermal conductivity. The primary material grades include:
- 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent formability and resistance to atmospheric and chemical corrosion.
- 316 (UNS S31600) — Enhanced molybdenum-containing grade offering superior resistance to pitting and crevice corrosion, particularly in chloride-rich environments.
- 321 (UNS S32100) — Titanium-stabilized grade suitable for high-temperature service applications.
Key Mechanical and Physical Properties
| Property | Specification |
|---|---|
| Tensile Strength (Minimum) | ≥ 520 MPa (304) / ≥ 485 MPa (316) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (304) / ≥ 170 MPa (316) |
| Elongation (A50mm) | ≥ 40% |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) (304) / 14.6 W/(m·K) (316) |
| Corrosion Resistance | Excellent resistance to acid, alkali, chloride, and atmospheric corrosion |
| Operating Temperature Range | −196°C to +870°C (304) / −196°C to +870°C (316) |
| Surface Finish | 2B / BA (Bright Annealed) / No. 4 / Mirror (Ra ≤ 0.4 μm) |
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A269 / A213 |
| Wall Thickness | 0.3 mm – 3.0 mm | ASTM A269 |
| Diameter Tolerance | ± 0.1 mm (± 0.004") | ASTM A269 |
| Wall Thickness Tolerance | ± 10% of nominal | ASTM A269 |
| Coil Winding Diameter | 500 mm – 2,000 mm (adjustable) | Manufacturer Specification |
| Coil Length per Reel | 50 m – 500 m (continuous) | Manufacturer Specification |
| Seam Type | Seamless / Welded (per ASTM A213) | ASTM A213 / A269 |
| End Condition | Plain / Beveled / Flanged | Per Customer Requirement |
| Surface Treatment | Pickled & Passivated (P&P) | ASTM A967 |
| Hydrostatic Test Pressure | 1.5 × Maximum Allowable Working Pressure | ASTM A269 |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, surface integrity, and metallurgical homogeneity:
- Raw Material Selection & Inspection: Only certified stainless steel strip or round bar from approved mills is accepted. Incoming materials undergo spectroscopic analysis (OES) to verify chemical composition compliance with ASTM/EN specifications.
- Coil Winding & Forming: Continuous stainless steel strip is precisely wound onto a mandrel using CNC-controlled winding machines. The winding tension is dynamically adjusted to maintain uniform helical geometry and consistent pitch throughout the coil length.
- Seam Welding (if applicable): Where welded construction is specified, the coil edges are joined via orbital TIG (Tungsten Inert Gas) welding or laser welding under argon shielding atmosphere to achieve full-penetration, leak-tight welds.
- Solution Annealing: The formed coil tube is subjected to solution annealing at 1010°C – 1150°C followed by rapid water quenching. This process eliminates cold-work hardening, restores full austenitic microstructure, and maximizes corrosion resistance.
- Pickling & Passivation: Post-annealing surface scale is removed via hydrofluoric-nitric acid pickling, followed by nitric acid passivation to establish a protective chromium oxide film on the surface (per ASTM A967).
- Dimensional Inspection & Testing: Each coil is subjected to ultrasonic thickness testing, optical diameter measurement, and hydrostatic pressure testing. Surface quality is verified through visual and eddy current inspection.
- Final Packaging & Dispatch: Qualified coil tubes are wrapped in moisture-proof film, sleeved in protective end caps, and secured on wooden or steel pallets for safe transit.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. is deployed across a broad spectrum of industrial and commercial applications:
- Evaporative Cooling Systems: As the primary heat transfer element in evaporative coolers, where uniform surface water distribution is critical for maximizing evaporative heat exchange efficiency. Research studies have demonstrated that coil tube diameter and surface finish significantly influence water film uniformity, directly impacting cooling capacity and energy efficiency.
- HVAC & Chiller Systems: Used as evaporator and condenser coils in commercial and industrial refrigeration units, air handling units, and process chillers.
- Food & Beverage Processing: Employed in pasteurization heat exchangers, CIP (Clean-in-Place) systems, and hygienic fluid transfer due to the material's non-reactive, corrosion-resistant properties.
- Pharmaceutical & Biotechnology: Utilized in bioreactor cooling jackets, sterilization loops, and sanitary process piping where cleanliness and corrosion resistance are paramount.
- Chemical & Petrochemical Processing: Deployed in heat exchange coils, reactor cooling systems, and distillation column internals where resistance to aggressive chemical media is required.
- Power Generation: Used in condensers, feedwater heaters, and waste heat recovery systems in both conventional and renewable energy installations.
- Marine & Offshore: Applied in seawater cooling loops and desalination plant heat exchangers, leveraging the chloride resistance of 316-grade material.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management and holds the following certifications and standards compliance:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001 — Environmental Management System certification demonstrating environmental responsibility in manufacturing operations.
- ASTM A269 / A213 — Full compliance with American Society for Testing and Materials standards for wrought austenitic stainless steel tubing and pipe.
- EN 10216-5 — European standard compliance for seamless and welded stainless steel tubes for heat exchangers.
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for fluid transport.
- ASME SA-213 / SA-269 — Compliance with American Society of Mechanical Engineers standards for boiler, heat exchanger, and similar applications.
- NACE MR0175 / ISO 15156 — Compliance for sour service applications (where applicable).
- Third-Party Inspection: Products are available for independent inspection by SGS, Bureau Veritas, or TÜV upon customer request.
Unique Selling Points
Superior Water Distribution Uniformity: Extensive research has been conducted on the influence of pipe diameter and surface configuration on evaporative cooling coil tube water distribution uniformity. Wenzhou Jixing's precision manufacturing tolerances ensure that the coil tube surface geometry promotes even water film coverage, maximizing evaporative cooling efficiency and minimizing dry-spot formation.
- Precision Dimensional Control: Tight tolerances (± 0.1 mm on OD) ensure seamless integration into heat exchanger banks and coil assemblies, reducing installation time and minimizing flow maldistribution.
- Full Material Traceability: Every coil is accompanied by a Mill Test Certificate (MTC) with heat number, chemical composition, and mechanical property data, enabling complete supply chain traceability.
- Customizable Specifications: Tailored OD, wall thickness, coil winding diameter, surface finish, and end treatment options to meet specific project requirements.
- Proven Corrosion Resistance: The pickled and passivated surface finish, combined with austenitic stainless steel chemistry, ensures long service life even in aggressive chemical and marine environments.
- Comprehensive Quality Assurance: Multi-stage inspection protocol including ultrasonic, eddy current, hydrostatic, and visual testing at every production stage.