Stainless Steel Spiral Coil Tube (Coil Tube) — Product No. 757
1. Product Overview
The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Specifically designed for heat exchange applications involving Organic Heat Transfer Fluids (OHTF), this product leverages the inherent advantages of spiral geometry to achieve superior convective heat transfer performance, compact heat exchange surface area, and efficient fluid distribution. The spiral coil configuration promotes secondary flow patterns within the tube, enhancing turbulent intensity and thereby improving the overall heat transfer coefficient compared to conventional straight-tube heat exchangers.
This product line represents an advanced solution for industrial thermal management systems where high thermal efficiency, chemical resistance, and long-term reliability are paramount. The coil tube is particularly suited for applications requiring the circulation of synthetic organic heat transfer media (e.g., thermal oils, molten salts) under controlled temperature and pressure conditions.
2. Material & Properties
2.1 Base Material
The Coil Tube is fabricated from austenitic stainless steel grades conforming to international standards, with the following primary options:
- 304 (UNS S30408 / 1.4301): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- 316 (UNS S31608 / 1.4401): Enhanced corrosion resistance grade with 2–3% Molybdenum (Mo) addition, suitable for aggressive chemical environments and chloride-containing media.
- 321 (UNS S32108 / 1.4541): Stabilized grade with Titanium (Ti) addition, resistant to sensitization at elevated temperatures, ideal for high-temperature heat transfer applications.
- 310S (UNS S31008 / 1.4845): High-temperature grade with elevated Ni and Cr content, suitable for sustained operation above 1000°C.
2.2 Key Material Properties
| Property | Grade 304 | Grade 316 | Grade 321 | Grade 310S |
|---|---|---|---|---|
| Chromium (Cr) Content (%) | 18.0–20.0 | 16.0–18.0 | 17.0–19.0 | 24.0–26.0 |
| Nickel (Ni) Content (%) | 8.0–10.5 | 10.0–14.0 | 9.0–12.0 | 19.0–22.0 |
| Molybdenum (Mo) Content (%) | — | 2.0–3.0 | — | — |
| Titanium (Ti) Content (%) | — | — | 5×(C−0.02)–0.70 | — |
| Maximum Service Temperature (°C) | 870 | 870 | 900 | 1150 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 | 19.2 |
| Specific Heat Capacity at 100°C (J/kg·K) | 500 | 500 | 500 | 500 |
| Linear Thermal Expansion (10⁻⁶/K, 20–100°C) | 17.3 | 17.3 | 17.3 | 18.0 |
| Tensile Strength (MPa, minimum) | 520 | 520 | 520 | 520 |
| Yield Strength (MPa, minimum) | 205 | 205 | 205 | 205 |
| Corrosion Resistance Rating | Good | Excellent | Good | Good |
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Spiral Coil Tube (Coil Tube) |
| Product No. | 757 |
| Tube Outer Diameter (OD) | 6 mm – 51 mm (customizable) |
| Tube Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Outer Diameter | 100 mm – 2000 mm |
| Coil Length (Developed) | 1 m – 50 m (customizable) |
| Number of Turns | 2 – 500 turns |
| Helix Angle | Adjustable per application requirement |
| Surface Finish | Ba ≤ 0.5 μm (electropolished); Ra ≤ 1.6 μm (standard) |
| Operating Pressure | Up to 4.0 MPa (design-dependent) |
| Operating Temperature Range | −196°C to +1150°C (grade-dependent) |
| Heat Transfer Medium | Organic Heat Transfer Fluids (OHTF), thermal oils, molten salts, water, steam |
| End Connections | Welded, threaded, flanged, or socket-welded (per customer specification) |
| Applicable Standards | ASTM A269, ASTM A213, EN 10216-5, GB/T 12771 |
4. Manufacturing Process
The production of the Stainless Steel Spiral Coil Tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Inspection: Incoming stainless steel tubes are verified against material certificates (Mill Test Certificates, MTC) confirming chemical composition, mechanical properties, and traceability per ASTM A269 or equivalent standards.
- Material Preparation: Tubes are cut to required lengths, deburred, and cleaned to remove surface contaminants. Pre-forming annealing may be applied to ensure uniform mechanical properties.
- Spiral Coiling (Cold Forming): Using precision CNC-controlled coiling machines, the straight tube is formed into a helical/spiral geometry. The coiling process is performed at controlled speeds to minimize work hardening and residual stress. The helix pitch, coil diameter, and number of turns are precisely controlled per engineering drawings.
- Post-Forming Stress Relief: Coiled tubes undergo stress-relief annealing (typically at 850–950°C for austenitic grades) to eliminate residual stresses introduced during cold forming, ensuring dimensional stability and preventing springback.
- Surface Treatment: Depending on application requirements, tubes may undergo pickling and passivation (to restore the chromium oxide passive film), electropolishing (for ultra-smooth surfaces and enhanced corrosion resistance), or passivation treatment.
- Dimensional Inspection: Coils are inspected for dimensional accuracy including coil OD, pitch consistency, tube OD/wall thickness uniformity, and straightness of end sections using coordinate measuring machines (CMM) and laser scanning systems.
- Pressure Testing: Each coil assembly undergoes hydrostatic or pneumatic pressure testing to verify structural integrity and absence of leaks at pressures exceeding the design operating pressure (typically 1.5× design pressure).
- Non-Destructive Testing (NDT): Welds and critical areas are inspected using radiographic testing (RT), ultrasonic testing (UT), or dye penetrant testing (PT) to detect internal or surface defects.
- Final Packaging & Dispatch: Qualified products are packaged with protective end caps, wrapped in moisture-proof materials, and dispatched with complete documentation including MTC, dimensional inspection reports, and pressure test certificates.
5. Applications
The Stainless Steel Spiral Coil Tube is engineered for a diverse range of industrial thermal applications:
- Organic Heat Transfer Fluid (OHTF) Systems: Primary application domain. The spiral geometry enhances turbulence and secondary flow, improving heat transfer efficiency when circulating thermal oils (e.g., Therminol VP-1, Dowtherm A) in industrial heating processes.
- Chemical Processing Industries: Reactor cooling, distillation column condensers, and heat recovery systems where corrosion-resistant heat exchange elements are required.
- Petrochemical & Refinery Applications: Crude oil fractionation, heat integration networks, and waste heat recovery systems.
- Pharmaceutical Manufacturing: Sterile heat exchange systems requiring high surface finish and resistance to chemical cleaning agents.
- Food & Beverage Processing: Pasteurization, sterilization, and thermal processing equipment requiring hygienic-grade surfaces.
- Power Generation: Auxiliary heating systems, feedwater preheaters, and thermal oil-based energy storage systems.
- Molten Salt Thermal Energy Storage (TES): Heat exchange coils for concentrated solar power (CSP) plants and industrial molten salt storage tanks.
- Cryogenic Applications: When fabricated from appropriate grades, suitable for cryogenic heat exchange at temperatures as low as −196°C (LNG applications).
6. Unique Selling Points
The Spiral Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through the following technical advantages:
- Enhanced Heat Transfer Performance: The helical geometry induces Dean vortices (secondary flow patterns), increasing the convective heat transfer coefficient by 20–50% compared to straight tubes of equivalent cross-section. This is particularly critical for Organic Heat Transfer Fluid (OHTF) systems where maximizing thermal efficiency reduces energy consumption.
- Compact Thermal Design: The spiral configuration provides a large heat transfer surface area within a compact volumetric envelope, reducing equipment footprint and installation costs.
- Superior Corrosion Resistance: Austenitic stainless steel construction ensures long-term resistance to oxidation, scaling, and chemical attack from organic heat transfer media, even at elevated temperatures.
- Precision Manufacturing: CNC-controlled coiling ensures dimensional accuracy within ±0.5 mm tolerance, guaranteeing proper fit and function in heat exchanger assemblies.
- Full Customization Capability: Flexible manufacturing capacity allows customization of coil diameter, pitch, tube dimensions, material grade, and end connections to meet specific engineering requirements.
- Thermal Cycling Durability: Post-forming stress relief and proper material selection ensure dimensional stability and fatigue resistance under repeated thermal cycling conditions.
7. Quality Certifications & Compliance
The manufacturing process and product quality are governed by internationally recognized standards and certifications:
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices |
| ASTM A269 | Standard specification for seamless austenitic stainless steel tube |
| ASTM A213 | Standard specification for seamless austenitic chromium-chromium-nickel steel heat-exchanger and heat-transfer tubing |
| EN 10216-5 | European standard for welded stainless steel tubes for heat exchangers |
| GB/T 12771 | Chinese national standard for welded stainless steel tubes for heat exchangers |