Stainless Steel Coil Tube with Thermal Conductive Adhesive — External Heating/Cooling Equipment
1. Product Overview
The stainless steel coil tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange component designed for external heating and cooling applications. This product integrates thermally conductive adhesive (thermal paste) technology with high-grade stainless steel coil tubing to achieve superior thermal transfer efficiency. The coil tube system serves as a critical interface between thermal media and process equipment, enabling precise temperature control in industrial, chemical, pharmaceutical, and food processing environments.
Unlike conventional bare coil tubes, this product incorporates a specialized thermally conductive filler between the coil tube and the mating surface, significantly reducing thermal contact resistance. This innovation results in enhanced heat dissipation rates, reduced energy consumption, and improved operational reliability under sustained thermal cycling conditions.
2. Material & Properties
2.1 Base Material
- Grade: SUS304 / SUS316L / SUS321 (Austenitic Stainless Steel)
- Standard Composition (SUS304): Cr 18–20%, Ni 8–10.5%, C ≤ 0.08%, Mn ≤ 2.0%, Si ≤ 1.0%
- Surface Finish: Electropolished (Ra ≤ 0.4 μm) or BA (Bright Annealed)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and aqueous environments; pitting resistance equivalent number (PREN) ≥ 19 (SUS304) or ≥ 24 (SUS316L)
2.2 Thermal Conductive Adhesive
- Type: Silicone-based or epoxy-based thermal paste
- Thermal Conductivity: 1.0 – 8.0 W/(m·K) (depending on formulation)
- Operating Temperature Range: −60 °C to +250 °C
- Dielectric Strength: ≥ 15 kV/mm
- Cure Temperature: Room temperature (RT) or 80–120 °C (oven-assisted)
2.3 Key Physical Properties
- Density: 7.93 g/cm³ (SUS304)
- Thermal Conductivity (Steel): 16.3 W/(m·K) at 20 °C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)
- Maximum Service Temperature: 870 °C (SUS304); 925 °C (SUS316L)
3. Technical Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | Φ6 – Φ50 mm | ±0.1 mm |
| Wall Thickness | 0.5 – 3.0 mm | ±0.05 mm |
| Coil Pitch | 10 – 60 mm | ±0.5 mm |
| Coil Length | 100 mm – 5,000 mm | ±2 mm |
| Coil Turns | 5 – 200 turns | ±1 turn |
| Thermal Paste Layer Thickness | 0.05 – 0.30 mm | ±0.02 mm |
| Pressure Rating | Up to 4.0 MPa (PN40) | — |
| Heat Transfer Coefficient | ≥ 850 W/(m²·K) (with paste) | — |
| Temperature Uniformity | ±3 °C across surface | — |
| Weight | Varies by configuration | — |
| Applicable Standards | ASTM A213/A269, GB/T 12771, JIS G3459 | — |
4. Manufacturing Process
4.1 Process Flow
- Material Selection & Incoming Inspection: Certified stainless steel seamless or welded tube stock is inspected for chemical composition (spectroscopic analysis), mechanical properties (tensile, hardness), and dimensional accuracy.
- Tube Straightening & Cutting: Raw tube is cold-straightened to achieve straightness tolerance ≤ 0.5 mm/m and cut to required coil length using precision laser or plasma cutting.
- Coil Forming: The straightened tube is fed into a CNC-controlled coiling machine to form the specified coil geometry (OD, pitch, number of turns) with minimal work hardening. Forming is performed at controlled speeds to prevent ovality exceeding 2% of OD.
- Solution Annealing (if required): Post-forming annealing at 1050–1100 °C followed by water quench to restore full austenitic microstructure, relieve residual stresses, and maximize corrosion resistance.
- Surface Treatment: Electropolishing or passivation treatment to remove surface contaminants, achieve mirror finish (Ra ≤ 0.4 μm), and form a stable chromium oxide passive layer.
- Thermal Paste Application: A precisely metered layer of thermally conductive adhesive is applied to the designated contact surface using automated dispensing equipment. Layer thickness is controlled within ±0.02 mm to ensure consistent thermal impedance.
- Curing & Bonding: The assembly is placed on the mating surface and subjected to controlled pressure and temperature (80–120 °C for 2–4 hours) to achieve full cure of the thermal adhesive, establishing a permanent low-thermal-resistance bond.
- Final Quality Control: Dimensional verification (CMM), pressure testing (1.5× working pressure), thermal performance testing, and visual inspection.
4.2 Key Process Controls
- CNC coiling ensures repeatability and dimensional consistency across batches
- Thermal paste dispensing is automated to eliminate human error in layer thickness
- In-process monitoring includes ultrasonic thickness measurement and dye penetrant testing (DPT) for weld integrity
5. Applications
5.1 Primary Application Domains
- Chemical Processing: Heat exchange in reactors, distillation columns, and mixing vessels where corrosion resistance and thermal efficiency are critical.
- Pharmaceutical Manufacturing: Precise temperature control in bioreactors, crystallization vessels, and CIP (Clean-In-Place) systems; compliance with FDA and GMP standards.
- Food & Beverage Industry: Pasteurization equipment, sterilization units, and heat recovery systems; SUS316L grade preferred for hygienic applications.
- Power Generation: External cooling coils for turbine components, transformer cooling systems, and nuclear-grade heat exchangers (SUS321 grade for high-temperature service).
- Electronics & Semiconductor: Thermal management of high-power electronic components, laser cooling systems, and battery thermal regulation.
- Automotive & Aerospace: Heat exchangers in engine cooling, brake systems, and aircraft hydraulic fluid temperature control.
5.2 Unique Selling Points (USPs)
Differentiated Advantages of the Thermal Paste-Integrated Coil Tube:
- Reduced Thermal Contact Resistance: The thermally conductive adhesive eliminates air gaps at the coil-to-surface interface, reducing thermal impedance by 60–80% compared to bare metal contact.
- Uniform Heat Distribution: Achieves ±3 °C temperature uniformity across the heated/cooled surface, critical for process consistency.
- Enhanced Durability: The cured adhesive bond resists vibration, thermal cycling, and mechanical shock without degradation of thermal performance.
- Customizable Geometry: CNC manufacturing enables bespoke coil configurations tailored to specific equipment interfaces.
- Energy Efficiency: Lower thermal resistance translates to reduced energy consumption (15–25% improvement) and smaller heating/cooling equipment sizing.
- Corrosion-Resistant Construction: Austenitic stainless steel base ensures long service life in aggressive chemical and aqueous environments.
6. Quality Certifications & Standards Compliance
6.1 Manufacturing Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management
- ASME Stamp — Pressure Vessel & Piping Components (where applicable)
- CE Marking — European Conformity for Pressure Equipment Directive (PED 2014/68/EU)
6.2 Material & Product Standards
- ASTM A213/A213M — Standard Specification for Ferritic, Austenitic, and Ferritic-Austenitic (Duplex) Stainless Steel Tubing for Heat Exchangers and Heat Transfer Equipment
- ASTM A269/A269M — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Other Similar Severe Service Applications
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transportation
- JIS G3459 — Japanese Industrial Standard for Stainless Steel Tubes for General Use
- DIN EN 10216-5 — European Standard for Non-Alloy and Alloy Steel Tubes — Technical Delivery Conditions — Part 5: Cold-Pulled Tubes of Austenitic Steels for Heat Exchangers and Similar Applications
6.3 Testing & Inspection Protocols
- Hydrostatic Pressure Testing: 1.5× maximum working pressure, held for ≥ 10 seconds with no leakage or visible deformation
- Chemical Analysis: Spark OES (Optical Emission Spectroscopy) for elemental verification
- Mechanical Testing: Tensile strength ≥ 520 MPa, elongation ≥ 40% (SUS304, per ASTM A213)
- Corrosion Testing: Salt spray test (ASTM B117) ≥ 1000 hours; intergranular corrosion test (ASTM A240/A240M)
- Thermal Performance Verification: Steady-state heat flux measurement to confirm ≥ 850 W/(m²·K) heat transfer coefficient
- Non-Destructive Testing (NDT): Eddy current testing (ECT) for surface and near-surface defects; magnetic particle inspection (MPI) where applicable
6.4 Traceability & Documentation
Each coil tube assembly is accompanied by a comprehensive Mill Test Certificate (MTC) and Heat Treatment Certificate, providing full material traceability from raw stock through final assembly. Batch-specific thermal paste datasheets and cure verification records are included to ensure complete quality documentation for end-user audit and regulatory compliance purposes.