Stainless Steel Coil Tube (Half-Coil Tube) for Heat Exchanger Vessels
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-grade Stainless Steel Coil Tubes (Half-Coil Tubes / Semi-Coil Tubes) designed specifically for integration into pressure vessels and heat exchanger systems. These coil tubes are engineered to serve as an efficient internal heat transfer medium, offering superior thermal performance compared to conventional jacketed vessel designs. The product is categorized under technical literature and engineering reference materials, drawing from rigorous comparative studies on the heat transfer efficiency and economic viability of jacketed vessels versus semi-coil tube vessels.
Unlike traditional jacketed vessels that rely on an external shell-and-jacket configuration, semi-coil tube vessels incorporate coiled stainless steel tubing directly within the vessel interior. This design eliminates the need for a large external jacket, significantly reducing the overall footprint, weight, and material consumption of the equipment while enhancing heat transfer coefficients. The coil tube configuration creates a turbulent flow regime within the tube, promoting efficient convective heat exchange between the process medium and the heating or cooling fluid.
Material & Properties
Stainless Steel Grades
- SUS 304 / AISI 304 (1.4301) — Austenitic stainless steel with excellent general corrosion resistance, suitable for food-grade, pharmaceutical, and general chemical processing applications.
- SUS 316 / AISI 316 (1.4401) — Molybdenum-enhanced austenitic stainless steel offering superior resistance to pitting and crevice corrosion in chloride-containing environments.
- SUS 316L / AISI 316L (1.4404) — Low-carbon variant of 316 with enhanced weldability and resistance to intergranular corrosion, ideal for high-purity and sanitary applications.
- SUS 321 / AISI 321 (1.4541) — Titanium-stabilized austenitic grade providing excellent resistance to intergranular corrosion at elevated temperatures (up to 870°C).
- SUS 304L / AISI 304L (1.4307) — Low-carbon version of 304 with improved weldability for applications requiring extensive welding operations.
Mechanical & Physical Properties
| Property | SUS 304 | SUS 316 | SUS 316L |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 485 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 170 |
| Thermal Conductivity (W/m·K at 20°C) | 16.3 | 14.6 | 14.6 |
| Specific Heat (J/kg·K) | 500 | 500 | 500 |
| Thermal Expansion Coefficient (×10⁻⁶/K) | 17.3 | 16.0 | 16.0 |
| Maximum Service Temperature (°C) | 870 | 870 | 870 |
| Corrosion Resistance (ASTM G48, 10% NaCl, 60°C) | Moderate | Excellent | Excellent |
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Half-Coil / Semi-Coil Tube) |
| Catalog Number | 832 |
| Tube Outer Diameter (OD) | 12 mm – 51 mm (customizable) |
| Tube Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch (Spacing Between Turns) | 10 mm – 50 mm (configurable per thermal design) |
| Coil Diameter | 200 mm – 2,000 mm (adaptable to vessel size) |
| Coil Length | Up to 3,000 mm (continuous seamless coil) |
| Surface Finish | 2B, BA (Bright Annealed), No. 4 Brushed, or Electropolished (Ra ≤ 0.4 μm) |
| Seam Type | Welded (TIG/argon arc) or Seamless (depending on tube OD) |
| Welding Quality | Full-penetration weld, 100% visual inspection, optional dye penetrant testing (PT) |
| Operating Pressure | Up to 1.6 MPa (design pressure, dependent on vessel configuration) |
| Operating Temperature Range | -196°C to 870°C |
| Helix Type | Single helix, double helix, or spiral coil configurations |
| End Connections | Flanged, threaded, socket-welded, or sanitary tri-clamp fittings |
| Standards Compliance | GB/T 12771, ASTM A269/A270, EN 10217-7, JIS G3459 |
| Customization | Available per customer-provided drawings and thermal engineering specifications |
Manufacturing Process
The production of stainless steel coil tubes follows a precisely controlled multi-stage manufacturing workflow to ensure dimensional accuracy, mechanical integrity, and corrosion resistance:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mill suppliers. Each batch undergoes spectroscopic analysis (PMI — Positive Material Identification) to verify alloy composition compliance with the specified grade. Incoming material is inspected for surface defects, dimensional tolerances, and mechanical properties.
- Coil Forming (Tube Bending): The straight stainless steel tube is fed through a precision CNC-controlled tube bending machine. The bending process employs a combination of mandrel support, wiper dies, and clamping dies to achieve uniform curvature without wall thinning, ovality, or kinking. The coil pitch and diameter are programmed according to the customer's thermal design specifications.
- Springback Compensation: Post-bending springback is calculated using material-specific elastic modulus and yield strength data. The bending machine parameters are pre-compensated to ensure the final coil geometry meets dimensional tolerances (±1 mm on coil diameter, ±0.5 mm on pitch).
- Welding (for Coil Assembly): Where multiple coil sections are required, TIG (Tungsten Inert Gas) welding is performed under argon shielding to produce full-penetration, leak-tight joints. The weld zone is maintained under continuous internal and external gas protection to prevent oxidation and ensure metallurgical integrity.
- Heat Treatment & Stress Relief: The formed coil tubes undergo solution annealing (1050°C – 1150°C) followed by controlled water quenching to restore full austenitic microstructure and maximize corrosion resistance. Alternatively, stress relief annealing at 300°C – 400°C may be applied to relieve residual bending stresses without sensitization.
- Surface Finishing: Depending on application requirements, the coil tubes may undergo pickling and passivation (HNO₃/HF acid bath) to remove surface oxide and contaminants, or electropolishing to achieve a Ra ≤ 0.4 μm surface finish for sanitary applications.
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Quality Inspection & Testing: Every coil tube assembly is subjected to:
- Visual inspection of welds and coil geometry
- Dimensional measurement (OD, wall thickness, coil diameter, pitch) using calipers, micrometers, and coordinate measuring machines (CMM)
- Hydrostatic pressure testing at 1.5× design pressure for 30 minutes with no visible leakage
- Dye penetrant testing (PT) on welds per ASTM E709
- Optional: Eddy current testing for wall thickness verification and defect detection
- Optional: Chemical composition verification via XRF or optical emission spectrometry (OES)
- Packaging & Dispatch: Finished coil tubes are wrapped in protective plastic film, placed on wooden pallets, and secured for transport. Each shipment includes a material test certificate (MTC / EN 10204 3.1), dimensional inspection report, and pressure test certificate.
Applications
Stainless steel coil tubes are integral components in a wide range of industrial and process engineering applications where efficient, compact heat exchange is required:
- Chemical Processing: Reactors and holding tanks requiring controlled heating or cooling of chemical feedstocks, intermediates, and final products. The coil tube configuration is particularly advantageous for viscous fluids where jacketed vessel designs may suffer from poor heat transfer due to stagnant boundary layers.
- Pharmaceutical Industry: Sanitary-grade reactors, crystallization vessels, and sterilization tanks where high surface finish (electropolished, Ra ≤ 0.4 μm) and full traceability are mandatory per GMP (Good Manufacturing Practice) standards.
- Food & Beverage Processing: Pasteurization tanks, CIP (Clean-in-Place) compatible heating vessels, dairy processing equipment, and brewing fermentation tanks. SUS 304 and SUS 316L grades meet FDA and EHEDG requirements.
- Petrochemical Industry: Intermediate heat exchange in distillation columns, reflux condensers, and process reactors handling aggressive hydrocarbon streams. SUS 316 and duplex stainless steel grades provide resistance to sulfuric acid and chloride corrosion.
- Power Generation: Auxiliary heating systems, feedwater preheaters, and thermal oil circulation loops in combined cycle power plants.
- Textile & Dyeing Industry: Dyeing kettles and heat exchange vessels requiring rapid temperature changes and resistance to acidic/alkaline dye solutions.
- Biotechnology & Bioreactors: Fermentation tanks requiring precise temperature control with minimal dead zones, leveraging the enhanced heat transfer coefficient of coil tube configurations.
Unique Selling Points: Coil Tube vs. Jacketed Vessel
Based on comparative engineering studies (Reference: "Comparison of Heat Transfer Efficiency and Economic Analysis Between Jacketed Vessels and Semi-Coil Tube Vessels"), the stainless steel coil tube design demonstrates significant advantages over conventional jacketed vessel configurations.
- Superior Heat Transfer Coefficient: The internal coil tube configuration creates a significantly higher heat transfer area per unit volume compared to external jacket designs. The forced convection within the coil tube eliminates the stagnant fluid layer inherent in jacketed vessels, resulting in overall heat transfer coefficients (U-values) that are 20%–40% higher than equivalent jacketed vessel designs.
- Reduced Equipment Footprint & Weight: By eliminating the bulky external jacket shell, coil tube vessels achieve a 30%–50% reduction in overall vessel diameter and weight. This translates to lower structural support costs, reduced transportation expenses, and easier installation in space-constrained facilities.
- Cost-Effective Thermal Design: The enhanced heat transfer efficiency reduces the required heating/cooling medium flow rate, lowering operational energy consumption. Additionally, the reduced material volume (no jacket shell) decreases fabrication costs. Comprehensive economic analysis confirms that the total cost of ownership (TCO) for coil tube vessels is substantially lower than jacketed alternatives over the equipment lifecycle.
- Elimination of Dead Zones: Jacketed vessels often suffer from poor heat transfer at the bottom of the vessel where the jacket cannot extend. Coil tubes can be configured to extend to the vessel bottom, ensuring uniform temperature distribution and eliminating thermal dead zones critical in pharmaceutical and food processing applications.
- Scalability & Customization: Coil tube geometry (pitch, diameter, number of turns) can be precisely optimized for any specific thermal duty, providing engineers with a flexible design tool for custom process requirements.
- Corrosion Resistance: The use of high-grade austenitic stainless steel (SUS 304/316/316L) ensures long-term resistance to corrosion in aggressive process environments, minimizing maintenance downtime and extending equipment service life beyond 15 years under normal operating conditions.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |