Stainless Steel Coil Tube (Coiltube) — Half-Coil Manufacturing Series
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered continuous tubular component manufactured in a coiled configuration. Unlike conventional straight stainless steel tubes, coil tubes are formed through specialized coiling processes that produce a continuous, uniform helical structure. This product line, developed and supplied by Wenzhou Jixing Metal Materials Co., Ltd, encompasses both full-coil and half-coil tube configurations, with particular emphasis on the advanced manufacturing techniques for half-coil tubes (半管盘管).
Half-coil tubes represent a specialized variant in which the coiling process is executed with a modified die and tooling setup, producing a tube with a distinct cross-sectional profile or coiling geometry that differs from standard full-coil configurations. The half-coil process addresses specific engineering requirements where the standard full-coil geometry is insufficient, offering enhanced flexibility in thermal exchange surface area optimization, mechanical fit within compact assemblies, and integration with specialized heat exchanger designs.
The core innovation lies in the application of new manufacturing processes and dedicated tooling (新工艺与工装) that enable consistent production of half-coil tubes at industrial scale while maintaining dimensional accuracy, surface finish integrity, and metallurgical stability throughout the forming process.
Material & Properties
Available Material Grades
- 304 (UNS S30400) — Austenitic stainless steel with excellent general corrosion resistance, formability, and weldability. Suitable for food-grade, pharmaceutical, and general industrial applications.
- 316 (UNS S31600) — Molybdenum-enhanced austenitic stainless steel offering superior resistance to pitting and crevice corrosion. Preferred for marine, chemical processing, and aggressive environments.
- 316L (UNS S31603) — Low-carbon variant of 316 with enhanced weldability and resistance to intergranular corrosion in sensitized conditions.
- 321 (UNS S32100) — Titanium-stabilized austenitic stainless steel providing excellent resistance to intergranular corrosion at elevated temperatures (up to 870°C / 1600°F).
- 304L (UNS S30403) — Low-carbon version of 304, suitable for applications requiring welding without post-weld annealing.
- 2205 (UNS S32205) — Duplex stainless steel combining ferritic and austenitic microstructures, offering higher yield strength (approximately double that of 304/316) and enhanced chloride stress corrosion resistance.
Key Physical & Mechanical Properties (Typical for 304/316 Grades)
- Operating Temperature Range: −196°C to +870°C (−321°F to +1600°F) for austenitic grades
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical corrosion
- Thermal Conductivity: 14–16 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C
- Specific Heat: 500 J/(kg·K) at 20°C
- Non-magnetic (in annealed condition): Suitable for MRI environments and magnetic-sensitive applications
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 1.0 mm – 50.8 mm (1/8" – 2") | ASME B36.19M / ASTM A269 |
| Wall Thickness | 0.1 mm – 3.0 mm (0.004" – 0.118") | ASME B36.19M |
| Coil Length (Continuous) | 5 m – 500 m (16 ft – 1,640 ft) per coil | Manufacturer Specification |
| Coil Diameter (Bundle OD) | 200 mm – 2,000 mm (8" – 80") | Custom / Application-Specific |
| Coil Pitch (Helix Pitch) | 0.5 mm – 10.0 mm (0.020" – 0.394") | Custom / Application-Specific |
| Surface Finish | BA (Bright Annealed), 2B, No. 4 Brushed, Electropolished | ASTM A270 / ASTM A269 |
| End Condition | Plain cut, Beveled, Threaded, Flanged, Brazed | Custom / Application-Specific |
| Hydrostatic Test Pressure | Up to 100 MPa (14,500 psi) — pressure-rated per ASME B31.3 | ASME B31.3 / ASTM A269 |
| Tolerance (OD) | ±0.05 mm – ±0.25 mm depending on size | ASTM A269 |
| Tolerance (Wall Thickness) | ±10% of nominal | ASTM A269 |
| Half-Coil Configuration | Modified die geometry for asymmetric coiling profile | Proprietary Tooling Design |
| Minimum Bend Radius | 3D – 5D (where D = outer diameter) | ASTM A269 / ASME B31.3 |
| Heat Treatment | Annealed (Solution Annealed), Stress Relieved | ASTM A269 |
Manufacturing Process
Process Flow for Half-Coil Tube Production
- Raw Material Selection & Inspection: Seamless stainless steel tube stock (conforming to ASTM A269 / ASME B36.19M) is received and subjected to incoming quality control (IQC), including chemical composition verification (via optical emission spectrometry or XRF), dimensional measurement, and surface inspection.
- Tube Straightening & Cutting: The raw tube is straightened using a multi-roller straightening machine to achieve a straightness tolerance of ≤0.5 mm/m. Tubes are then cut to the required length using a precision sawing or laser cutting system.
- End Preparation: Tube ends are deburred, chamfered, and prepared for subsequent forming operations. This ensures uniform material flow during the coiling process and prevents surface defects or material cracking at the tube ends.
- Die & Tooling Setup (Critical Step for Half-Coil): The half-coil manufacturing process utilizes a modified coiling die assembly that differs from the standard full-coil die. The half-coil die is designed with an asymmetric or partially constrained geometry, allowing the tube to be formed into a helical configuration with a specific cross-sectional modification or pitch variation. This proprietary tooling is the core differentiator of the half-coil process.
- Coiling Operation: The prepared tube is fed through the coiling die assembly. A precision-driven coiling machine rotates the die head while advancing the tube axially, producing a continuous helical coil. For half-coil configurations, the die geometry ensures that the tube undergoes controlled plastic deformation with minimal thinning, preserving wall thickness integrity and mechanical properties.
- In-Process Quality Monitoring: During coiling, dimensional parameters (coil OD, pitch, tube OD, wall thickness) are monitored using in-process gauging systems. Real-time feedback allows for immediate correction of any deviations.
- Heat Treatment (if required): Depending on the application and material grade, the coiled tube may undergo a solution annealing or stress-relief heat treatment to restore full austenitic properties, eliminate residual stresses introduced during forming, and ensure maximum corrosion resistance.
- Surface Treatment: Post-forming surface treatments include pickling and passivation (to restore the passive chromium oxide layer), electropolishing (for ultra-clean surfaces in pharmaceutical/food applications), or mechanical brushing.
- Final Inspection & Testing: The finished coil tube undergoes comprehensive final inspection including:
- Dimensional verification (OD, wall thickness, coil geometry, pitch)
- Hydrostatic pressure testing (per ASTM A269 / ASME B31.3)
- Visual inspection for surface defects, dents, or deformation
- Chemical composition re-verification (if required by customer specification)
- Corrosion testing (salt spray testing per ASTM B117, if specified)
- Packaging & Dispatch: Qualified coil tubes are packaged in protective wrapping (plastic film, VCI paper, or wooden crates) to prevent surface damage during transportation. Each coil is labeled with a unique batch/heat number for full traceability.
Key Process Advantages of the Half-Coil Technology
- Reduced Material Waste: The continuous coiling process eliminates the need for cutting individual tube segments, resulting in material utilization rates exceeding 98%.
- Uniform Deformation: The specialized half-coil die ensures controlled, uniform plastic deformation, minimizing wall thinning and preserving mechanical integrity throughout the coil length.
- Customizable Geometry: The proprietary tooling design allows for precise control over coil pitch, OD, and cross-sectional profile, enabling application-specific optimization.
- Scalable Production: The process is suitable for both prototype production and high-volume manufacturing, with tooling changeover times minimized through modular die designs.
Applications
- Heat Exchangers & Radiators: Coil tubes serve as the primary heat transfer elements in air-cooled heat exchangers, automotive radiators, HVAC (Heating, Ventilation, and Air Conditioning) systems, and industrial process coolers. The helical geometry maximizes surface area within a compact volume.
- Refrigeration & Air Conditioning: Used in evaporator and condenser coils for commercial refrigeration units, domestic refrigerators, freezers, and air conditioning systems. Stainless steel coil tubes offer superior durability compared to copper or aluminum alternatives in corrosive environments.
- Food Processing & Dairy Equipment: 304 and 316L coil tubes are extensively used in milk pasteurizers, condensers, and heat exchangers in food processing plants. The non-magnetic, corrosion-resistant, and hygienic properties of stainless steel make it ideal for food-contact applications.
- Pharmaceutical & Biotechnology: Electropolished 316L coil tubes are used in pharmaceutical reactors, sterilization systems, and bioprocessing equipment where ultra-clean surfaces and full traceability are mandated.
- Chemical Processing: 316 and 2205 coil tubes are employed in chemical reactors, distillation columns, and heat exchangers handling aggressive chemicals, acids, and chloride-containing solutions.
- Marine & Offshore Applications: 316 and 2205 coil tubes are used in marine heat exchangers, ballast water systems, and offshore platform cooling systems where resistance to seawater corrosion is critical.
- Power Generation: Coil tubes are used in waste heat recovery systems, condensers, and economizers in power plants, particularly in environments where high-temperature and high-pressure conditions demand durable, corrosion-resistant tubing.
- Automotive & Transportation: Stainless steel coil tubes are used in automotive exhaust heat exchangers, transmission coolers, and fuel cell cooling systems in electric vehicles.
- Medical Equipment: Non-magnetic 304 coil tubes are used in MRI-compatible cooling systems, medical device heat exchangers, and sterilization equipment.
Quality Certifications & Standards Compliance
Applicable International Standards
| Standard | Description | Relevance |
|---|---|---|
| ASTM A269 / A269M | Standard Specification for Seamless and Wrought Stainless Steel Tube for Heat Exchangers and Similar Applications | Primary material and product specification |
| ASTM A270 / A270M | Standard Specification for General Requirements for Seamless and Wrought Austenitic Stainless Steel Pipes and Tubes | General requirements for austenitic stainless steel tubing |
| ASME B36.19M | Welded and Seamless Wrought Stainless Steel Pipe | Dimensional specifications and tolerances |
| ASME B31.3 | Process Piping | Pressure design and testing requirements |
| EN 10217-7 | Technical Delivery Conditions for Stainless Steel Tubes for Pressure Purposes — Part 7: Non-Corrosion-Resistant Tubes for Heat Exchangers | European specification for heat exchanger tubing |
| ISO 3506 | Stainless Steel Tubes for Heat Exchangers and Similar Applications | International standard for heat exchanger tubing |
| GB/T 12771 | Stainless Steel Seamless Tubes for Fluid Transportation (Chinese National Standard) | Chinese national standard for stainless steel tubing |
Quality Management & Certifications
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control throughout the manufacturing lifecycle.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to environmentally responsible manufacturing practices.
- CE Marking (EU) — Conformity with European Union directives for products intended for the European market, including pressure equipment directives where applicable.
- PED (Pressure Equipment Directive 2014/68/EU) — Compliance for pressure-rated coil tube assemblies used in regulated applications within the European Economic Area.
- 3.1 / 3.2 Material Certification (EN 10204) — Full material traceability with third-party inspection, providing chemical analysis, mechanical test results, and dimensional verification for critical applications.
- Mill Test Reports