Stainless Steel Coil Tube for Floating Coil Heat Exchanger Systems
Product Code: No. 1192 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Category: Coil Tube (盘管) — Industrial Heat Exchange Components
1. Product Overview
The stainless steel coil tube is a precision-engineered helical or spiral-wound tubing product specifically designed for integration into Floating Coil Heat Exchangers (FCHE). Unlike fixed-tube heat exchangers, floating coil systems allow the coil element to expand and contract thermally without generating excessive stress on the shell or end connections. This product line draws upon advanced structural and process innovations derived from extensive research into copper tube welding configurations within floating coil heat exchangers, translating those improvements into a superior stainless steel coil tube solution.
The coil tube serves as the primary heat transfer surface, where process fluid flows through the helical channel while a secondary medium circulates within the enclosing shell. The floating design accommodates differential thermal expansion between the coil and the vessel, making this product ideal for high-temperature-differential applications in HVAC, chemical processing, and power generation industries.
2. Material & Properties
2.1 Base Materials
- Austenitic Stainless Steel: AISI 304 (UNS S30400), AISI 316 (UNS S31600), and AISI 321 (UNS S32100)
- Super-Austenitic Grades: AISI 316L (UNS S31603), Alloy 904L (UNS N08904) for highly corrosive environments
- Custom Alloys: Available upon request for specialized chemical resistance requirements
2.2 Mechanical Properties
- Tensile Strength (Ultimate): ≥ 520 MPa (AISI 304), ≥ 550 MPa (AISI 316)
- Yield Strength (0.2% Proof): ≥ 205 MPa (AISI 304), ≥ 240 MPa (AISI 316)
- Elongation at Break: ≥ 40% (AISI 304), ≥ 35% (AISI 316)
- Operating Temperature Range: −196 °C to +870 °C (depending on grade)
2.3 Physical Properties
- Density: 8.00 g/cm³ (AISI 304), 8.03 g/cm³ (AISI 316)
- Thermal Conductivity: 16.3 W/(m·K) at 20 °C (AISI 304)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (AISI 304), 16.0 × 10⁻⁶ /°C (AISI 316)
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical corrosion; pitting resistance index (PREN) ≥ 24 for AISI 316
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm – 50.80 mm (¼" – 2") | ASTM A213 / ASTM A269 |
| Wall Thickness | 0.50 mm – 3.18 mm (0.020" – 0.125") | ASTM A213 / ASTM A269 |
| Coil Mean Diameter (CMD) | 100 mm – 1500 mm | Custom / Client-Specified |
| Coil Length (Total Developed Length) | 5 m – 500 m | Custom / Client-Specified |
| Number of Coils (Turns) | 10 – 500 turns | Custom / Client-Specified |
| Coil Pitch (Center-to-Center) | 1.5× OD – 3.0× OD | ASME PTB-12 |
| Surface Finish | Baer (2B), Pickled & Passivated, Electro-Polished (Ra ≤ 0.4 μm) | ASTM A478 |
| End Configuration | Plain, Beveled, Threaded, Flanged, or Weld-Prepended | ASME B1.20.1 / ASME B16.5 |
| Welding Method | Orbital TIG (GTAW), Laser Welding, Resistance Welding | ASME Section IX / ISO 6947 |
| Design Pressure | Up to 4.0 MPa (580 psi) | ASME BPV Code Section IV |
| Design Temperature | Up to 400 °C (752 °F) | ASME BPV Code Section IV |
| Hydrostatic Test Pressure | 1.5 × Design Pressure (minimum) | ASME BPV Code Section IV |
| Applicable Standards | ASTM A213, ASTM A269, ASME BPV Code Sec. IV, EN 10217, GB/T 12771 | — |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel seamless or welded tube undergoes full chemical composition analysis (OES/SEM), mechanical property verification, and visual surface inspection per ASTM A213 / A269 requirements.
- End Preparation: Tube ends are deburred, chamfered, and cleaned to ensure proper fit-up for subsequent welding operations. Precision cutting ensures perpendicularity within ±0.5°.
- Coil Winding: High-precision CNC coil winding machines form the helical geometry. The winding parameters (CMD, pitch, number of turns) are controlled by servo-driven systems with positional accuracy of ±0.5 mm.
- Welding (Critical Step): The coil tube is joined using Orbital Tungsten Inert Gas Welding (GTAW) in accordance with ASME Section IX qualification procedures. This process ensures uniform, defect-free welds around the entire circumference. The welding parameters (current, voltage, travel speed, shielding gas flow) are optimized for each tube geometry.
- Heat Treatment (if applicable): Post-weld annealing or solution heat treatment may be performed at 1050–1150 °C followed by rapid quenching to restore full austenitic microstructure and eliminate sensitization.
- Pickling & Passivation: The finished coil is subjected to acid pickling (HNO₃/HF blend) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide layer (minimum 100 ppm chromium content in surface film).
- Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× design pressure for a minimum dwell time of 30 minutes, with no leakage permitted.
- Final Inspection: Visual inspection, dimensional verification (CMM or laser scanning), and radiographic testing (RT) or ultrasonic testing (UT) of critical welds per ASME BPV Code requirements.
4.2 Welding Structure & Process Improvements (Key Innovation)
Derived from advanced research into floating coil heat exchanger welding configurations: The welding joint design has been optimized to minimize stress concentration at the coil-to-end-plate connection. Key improvements include:
- Enhanced Fillet Weld Geometry: Transition from conventional right-angle fillet welds to reinforced J-groove or beveled configurations, increasing weld throat thickness by 20–35% and significantly reducing fatigue crack initiation risk.
- Multi-Pass Welding Strategy: Implementation of multi-pass orbital GTAW with interpass temperature control (≤ 150 °C) to minimize thermal distortion and prevent sensitization in the heat-affected zone (HAZ).
- Improved Fit-Up Tolerance: Gap control tightened to 0.5–1.0 mm with root face preparation, ensuring full-penetration welds with no root concavity defects.
- Shielding Gas Optimization: Use of high-purity argon (≥ 99.99%) with helium blend (Ar/He 70:30) for thicker wall sections to ensure deep, uniform penetration and minimize porosity.
- Post-Weld Stress Relief: Low-temperature stress relief at 425–550 °C for 2–4 hours to reduce residual stresses by up to 60% without affecting mechanical properties.
5. Applications
- HVAC Systems: Chilled water coils, hot water heating coils, and condenser/evaporator elements in commercial and industrial air handling units.
- Chemical Processing: Reactor jacket cooling coils, distillation column condensers, and heat recovery systems handling aggressive chemicals (acids, chlorides, alkalis).
- Food & Beverage Industry: Pasteurization coils, sterilization (HTST) systems, and thermal processing equipment requiring hygienic-grade surfaces (Ra ≤ 0.5 μm).
- Pharmaceutical Manufacturing: Clean-in-place (CIP) compatible heat exchangers for process fluid heating and cooling.
- Power Generation: Feedwater preheating coils, steam condensers, and thermal oil heating systems in power plants.
- Marine & Offshore: Sea water cooling coils, bilge water heat exchangers, and ballast water treatment systems.
- Oil & Gas: Downstream process cooling, refinery heat integration, and LNG (Liquefied Natural Gas) processing applications.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Full production process certification |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| ASME "S" Stamp | Pressure Vessel Manufacturer Authorization (Section VIII Div. 1) |
| ASME BPV Code Section IV | Heating Boiler Code compliance for heat exchanger components |
| CE Marking (PED 2014/68/EU) | European Pressure Equipment Directive compliance |
| EN 10204 Type 3.1 | Inspection Certificate with material test reports |
| NORSOK M-650 | Offshore welding procedure qualification (if applicable) |
| 3-A Sanitary Standards | Food and dairy industry hygienic design compliance (for electropolished finish) |
7. Unique Selling Points
- Optimized Welding Architecture: Proprietary weld joint design informed by advanced research into floating coil heat exchanger welding configurations, delivering 35% improvement in fatigue life and superior joint integrity under cyclic thermal loading.
- Precision CNC Coil Winding: Automated winding with ±0.5 mm positional accuracy ensures uniform pitch distribution, consistent heat transfer coefficients, and balanced flow distribution across all coil passes.
- Full Traceability: Every coil tube is accompanied by a complete material traceability package including mill certificates, chemical analysis, mechanical test reports, and welding procedure qualifications (WPQ/WPS).
- Custom Engineering Capability: Flexible design parameters accommodate virtually any coil geometry, material grade, and end-connection configuration to meet specific application requirements.
- Corrosion-Resistant Construction: Selection of appropriate stainless steel grades ensures long service life in aggressive environments, with optional electropolished surfaces for hygienic and high-purity applications.
- Thermal Efficiency: The floating coil design combined with optimized coil pitch and tube geometry maximizes heat transfer area while minimizing pressure drop through the tube side.
Wenzhou Jixing Metal Materials Co., Ltd. — Engineering Excellence in Stainless Steel Coil Tube Solutions for Floating Coil Heat Exchanger Applications.