Spiral Stainless Steel Coil Tube for Industrial Drying Systems
Product Overview
The Spiral Stainless Steel Coil Tube is a precision-engineered heat exchange component designed for use in spiral coil tube dryers, particularly in the thermal processing of precipitated carbon black (PCB) and similar particulate materials. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a critical element in continuous drying operations where efficient heat transfer, corrosion resistance, and mechanical durability are paramount. The coil tube functions as the primary heat transfer medium, circulating heated fluids (steam, thermal oil, or hot water) through a helically wound configuration to maximize surface area exposure and thermal efficiency within a compact footprint.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior combination of corrosion resistance, thermal conductivity, and mechanical integrity under sustained high-temperature service conditions.
- Primary Alloy Grade: SUS304 (ASTM A213 TP304) / SUS316L (ASTM A213 TP316L) — depending on service environment and fluid compatibility requirements
- Chromium (Cr) Content: 18.0–20.0% (SUS304) / 16.0–18.0% (SUS316L)
- Nickel (Ni) Content: 8.0–10.5% (SUS304) / 10.0–14.0% (SUS316L)
- Molybdenum (Mo) Content: 2.0–2.5% (SUS316L only — provides enhanced resistance to chloride-induced pitting and crevice corrosion)
- Maximum Operating Temperature: Up to 870°C (SUS304) / Up to 815°C (SUS316L) in continuous oxidation environments
- Thermal Conductivity: 16.3 W/(m·K) at 100°C (SUS304) / 14.6 W/(m·K) at 100°C (SUS316L)
- Surface Finish: 2B (Cold Rolled and Annealed) or BA (Bright Annealed), with surface roughness Ra ≤ 0.8 μm
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, weak acids, alkalis, and oxidizing environments; SUS316L grade offers superior resistance to chlorides and marine atmospheres
- Non-magnetic Properties: Austenitic microstructure ensures non-magnetic behavior, beneficial for applications involving electromagnetic compatibility
Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | Φ8 mm – Φ50 mm (custom sizes available) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Helical Coil Diameter | Φ200 mm – Φ2000 mm (customizable per dryer design) |
| Coil Pitch | 10 mm – 50 mm (adjustable for flow velocity and heat transfer optimization) |
| Coil Length / Development Length | Up to 500 m per continuous helical section |
| End Connection Type | Threaded (NPT/BSP), Flanged (ANSI/ISO), Welded (TIG/Orbital), or Quick-Disconnect fittings |
| Design Pressure | Up to 1.6 MPa (16 bar) standard; up to 4.0 MPa (40 bar) for high-pressure variants |
| Design Temperature Range | −40°C to +450°C (standard); up to +870°C (SUS304 high-temperature variant) |
| Surface Treatment | Pickled and Passivated (PP); optional electropolishing for food-grade or pharmaceutical applications |
| Compliance Standards | ASTM A213 / A269, EN 10216-5, GB/T 12771, JIS G3459 |
| Heat Transfer Medium | Steam (saturated/superheated), thermal oil, hot water, or other process fluids |
Manufacturing Process
The production of the Spiral Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and long-term operational reliability:
- Raw Material Inspection: Incoming stainless steel seamless tubing undergoes spectroscopic composition analysis, mechanical property verification, and hydrostatic pressure testing per ASTM A213 requirements.
- Coil Winding (Helical Forming): Precision CNC-controlled coil winding machines form the straight tubing into a continuous helical configuration. Winding parameters (pitch, diameter, tension) are programmatically controlled to maintain ±0.5 mm dimensional tolerance throughout the coil length.
- Heat Treatment (if required): Solution annealing at 1050–1150°C followed by controlled water quenching to restore full austenitic microstructure and relieve residual stresses from cold forming.
- Pickling and Passivation: The coil is immersed in an acid pickling bath (typically a mixture of nitric acid and hydrofluoric acid) to remove oxide scale and contaminants. Subsequent passivation treatment forms a stable chromium oxide (Cr₂O₃) protective film on the surface.
- End Preparation and Fitting Installation: Tube ends are cut square, deburred, and fitted with the specified connection hardware (threads, flanges, or weld preparations). All weld joints are completed via Gas Tungsten Arc Welding (GTAW/TIG) with argon shielding gas to maintain interior purity.
- Pressure and Leak Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× the design pressure, followed by helium or soap-bubble leak detection at all joints and welds.
- Final Inspection and Packaging: Visual inspection, dimensional verification, and surface finish measurement are performed. The coil is then wrapped in protective film, placed in export-grade wooden crates, and secured for transportation.
Applications
The Spiral Stainless Steel Coil Tube is a versatile component employed across multiple industrial sectors where efficient, corrosion-resistant heat exchange is required:
- Precipitated Carbon Black (PCB) Drying: As the primary heat transfer element in spiral coil tube dryers, the coil tube facilitates efficient thermal evaporation of water from wet carbon black slurry, achieving target moisture content (typically < 1.0% by weight) in a continuous, space-efficient process. The helical configuration ensures uniform heat distribution and prevents material channeling or dead zones.
- Chemical Processing: Used in reactors, condensers, and heat exchangers handling aggressive chemicals including acids, alkalis, and solvents where carbon steel would corrode rapidly.
- Pharmaceutical and Food Processing: SUS316L grade coil tubes with electropolished interiors meet FDA and EU GMP requirements for sanitary heat exchange in dairy, beverage, and pharmaceutical production lines.
- Power Generation: Employed in auxiliary heating systems, feedwater heaters, and steam superheaters in thermal power plants.
- Petrochemical Industry: Used in distillation columns, reboilers, and process heating systems exposed to hydrocarbons, sulfides, and chlorides.
- Environmental Engineering: Applied in flue gas desulfurization (FGD) systems, wastewater treatment heat recovery, and industrial waste incineration heat exchange systems.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification, demonstrating consistent adherence to international quality standards throughout the manufacturing lifecycle.
- ISO 14001:2015 — Environmental Management System certification, ensuring environmentally responsible production practices.
- ASME Section VIII — Compliance for pressure vessel and heat exchanger components where applicable.
- CE Marking — Conformity with European directives for machinery and pressure equipment (PED 2014/68/EU).
- Materiel Test Reports (MTR): Every batch of coil tube is accompanied by a full mill test certificate documenting chemical composition, mechanical properties (tensile strength, yield strength, elongation), and heat treatment records.
- NACE/AMPP — Compliance with corrosion prevention standards for oil and gas industry applications.
- 3.1 Material Certificates (EN 10204): Third-party inspection and test reports available upon request for critical applications.
Unique Selling Points
1. Superior Helical Geometry for Enhanced Heat Transfer: The continuous spiral configuration maximizes the surface-area-to-volume ratio, enabling significantly higher heat transfer coefficients compared to straight-tube designs. In PCB drying applications, this translates to reduced dryer footprint, lower energy consumption, and faster throughput.
2. Full-Length Corrosion Resistance: Unlike carbon steel alternatives that require internal coatings or linings, the austenitic stainless steel construction provides inherent, uniform corrosion resistance across both the internal and external surfaces — eliminating coating failure risks and extending service life to 10–20+ years in aggressive environments.
3. Customizable Engineering Solutions: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil tube designs, with parameters including tube diameter, wall thickness, coil pitch, helical diameter, and end connections tailored to specific dryer configurations and process requirements. Rapid prototyping and short lead times support project-specific development.
4. Proven Performance in Carbon Black Drying: The coil tube design has been validated in industrial-scale precipitated carbon black drying operations, where it delivers consistent moisture reduction rates and minimal product degradation — critical for maintaining carbon black particle morphology and end-use performance in rubber, ink, and pigment applications.
5. Comprehensive Quality Assurance: From raw material spectroscopic verification through final pressure testing and third-party inspection, every coil tube undergoes a multi-stage quality control protocol ensuring conformance to international standards and customer specifications.