Stainless Steel Coil Tube — Coil Tube for Industrial Heating Applications
1. Product Overview
The Stainless Steel Coil Tube (also referred to as Coiled Pipe or Continuous Coil Tube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, designed for demanding industrial heating and thermal management applications. This product is supplied in continuous coil form, enabling seamless integration into large-scale heat exchange systems, process heating circuits, and specialized environmental control installations.
Particularly notable is its application in Electrostatic Precipitator (ESP) Wall Panel Heating Systems for submerged arc furnaces (mineral furnaces), where the coil tube serves as the primary heat transfer medium to prevent dust adhesion, corrosion, and material buildup on the ESP housing. The coil geometry provides high surface-area-to-volume ratios, maximizing thermal efficiency while maintaining structural integrity under cyclic thermal loading.
2. Material & Properties
2.1 Material Grades
- AISI 304 / SUS 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- AISI 316L (UNS S31603) — Low-carbon variant with superior resistance to chloride-induced pitting and intergranular corrosion
- AISI 321 (UNS S32100) — Titanium-stabilized grade suitable for elevated-temperature service up to 870°C
- AISI 310S (UNS S31008) — High-temperature austenitic grade for extreme thermal environments
2.2 Mechanical & Physical Properties
- Tensile Strength: ≥ 520 MPa (ASTM A213/A269)
- Yield Strength: ≥ 205 MPa (at 0.2% offset)
- Elongation: ≥ 40% (minimum, in annealed condition)
- Thermal Conductivity: 16.3 W/(m·K) at 25°C (AISI 304)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Operating Temperature Range: −196°C to 870°C (grade-dependent)
- Corrosion Resistance: Excellent against atmospheric, aqueous, and mildly oxidizing environments
2.3 Key Performance Advantages
- Outstanding resistance to thermal cycling fatigue, essential for ESP heating applications involving repeated start/stop cycles
- Non-magnetic in annealed condition, compatible with electromagnetic equipment
- Hygienic surface finish (Ra ≤ 0.4 μm available upon request) for food-grade and pharmaceutical variants
- Weldability to ASTM A240 plate and structural components without cracking
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (custom sizes available) | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A213 / EN 10216-5 |
| Coil Inner Diameter (CID) | 300 mm – 1,200 mm | Manufacturer Standard |
| Coil Length per Spool | Up to 500 m (continuous) | — |
| Surface Finish | 2B, No. 4 Brushed, BA (Bright Annealed), Mirror (Ra ≤ 0.2 μm) | ASTM A480 |
| Tolerance — OD | ±0.1 mm (standard); ±0.05 mm (precision) | ISO 4287 |
| Tolerance — Wall Thickness | ±10% (standard); ±5% (precision) | ASTM A213 |
| End Condition | Open, capped, or welded to fittings | Custom |
| Heat Treatment | Solution Annealed (1050–1150°C) + Water Quenched | ASTM A213 |
| Maximum Working Pressure | Up to 16 MPa (pressure-tested) | PNEumatic/HYDRAULIC test |
| Applicable Standards | ASTM A213, A269, A778; EN 10216-5; GB/T 12771; JIS G3459 | — |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Selection — Certified stainless steel strip or seamless tube blanks sourced from accredited mills (e.g., Outokumpu, POSCO, Baosteel), accompanied by mill test certificates (MTC) per EN 10204 3.1.
- Coiling / Pipe Forming — High-precision coiling machinery (continuous tube coiler) forms the tube into the required coil geometry with controlled bend radii (minimum bend radius ≥ 3× OD) to prevent wall thinning and ovality.
- Welding (for welded coil tube) — Automatic TIG (GTAW) or orbital welding along the longitudinal seam with 100% helium or argon back-purge to ensure full penetration and oxidation-free internal welds.
- Heat Treatment — Solution annealing in a continuous furnace or batch furnace at 1050–1150°C followed by rapid quenching to achieve full austenitic microstructure and maximum corrosion resistance.
- Pickling & Passivation — Immersion in nitric/hydrofluoric acid bath to remove oxide scale, followed by passivation treatment to restore the chromium oxide protective layer.
- Surface Finishing — Mechanical polishing, electropolishing, or chemical brightening depending on the required surface quality (2B, BA, No. 4, or Mirror finish).
- Quality Inspection — Hydrostatic or pneumatic pressure testing, dimensional verification (OD, wall thickness, straightness), visual inspection of welds, and optional eddy current or ultrasonic flaw detection.
- Packaging & Dispatch — Coils wrapped in moisture-proof polyethylene film, secured on wooden pallets or steel cradles, and labeled with product identification, batch traceability, and shipping documentation.
4.2 Quality Control Milestones
- Incoming inspection of raw materials with spectrometric composition verification (OES analysis)
- In-process monitoring of coil diameter, wall thickness, and surface quality at defined intervals
- Final product testing including pressure testing at 1.5× maximum working pressure for a minimum of 30 seconds
- Full traceability from heat number to finished coil, enabling recall or forensic analysis if required
5. Applications
5.1 Primary Applications
- Electrostatic Precipitator (ESP) Wall Panel Heating — The coil tube is installed on the interior walls of ESP housings in submerged arc furnaces (mineral furnaces) to maintain surface temperatures above the dew point, preventing the adhesion of molten slag, dust, and corrosive gases. This application requires precise thermal calculation of heat flux, coil spacing, and flow velocity to ensure uniform wall temperature distribution.
- Industrial Process Heating — Heat transfer coils in chemical reactors, evaporators, condensers, and heat exchangers where corrosion resistance and thermal stability are paramount.
- Power Generation — Superheater tubes, economizers, and air preheaters in boiler systems.
- Oil & Gas — Subsea umbilical heating coils, wellhead flow assurance systems, and offshore platform heating circuits.
- Food & Pharmaceutical — CIP (Clean-in-Place) systems, sterilization loops, and sanitary heat exchangers requiring hygienic surface finishes.
- Automotive & Aerospace — Engine cooling circuits, hydraulic lines, and fuel system tubing requiring high-temperature resistance and weight optimization.
5.2 ESP Heating Coil — Special Considerations
In the context of submerged arc furnace (SAF) electrostatic precipitator wall panel heating, the coil tube design must account for:
- Thermal load calculation — Determination of required heat input based on furnace exhaust gas temperature, ESP housing surface area, and ambient conditions
- Flow velocity optimization — Ensuring adequate medium (steam, hot oil, or heated water) velocity to prevent local overheating and scaling
- Thermal expansion management — Incorporation of expansion loops or flexible joints to accommodate differential thermal expansion between the coil and the ESP housing
- Corrosion protection — Selection of grade (typically AISI 316L or 321) based on the chemical composition of the furnace exhaust gases (SO₂, HCl, HF, etc.)
- Mechanical vibration resistance — Secure mounting to withstand gas flow-induced vibration without fatigue failure
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Certified manufacturing processes |
| ISO 14001:2015 | Environmental Management System — Sustainable production practices |
| ISO 45001:2018 | Occupational Health & Safety Management |
| CE (EU) Marking | Compliance with European directives for pressure equipment and materials |
| EN 10204 3.1 | Inspection Certificate — Material and product test documentation |
| ASTM / ASME | Compliance with American Society for Testing and Materials / American Society of Mechanical Engineers standards |
| TÜV / SGS Inspection | Third-party verification of material composition, mechanical properties, and dimensional accuracy |
| PED (Pressure Equipment Directive 2014/68/EU) | Applicable for coil tubes used in pressure-containing systems |
7. Unique Selling Points
- Engineered for Thermal Cycling — The coil tube is specifically designed to withstand repeated thermal expansion and contraction cycles, making it ideal for ESP heating systems in mineral furnaces where operating conditions are highly variable.
- Continuous Coil Supply — Up to 500-meter continuous lengths eliminate field welding requirements, reducing leak points and installation time.
- Custom Geometry Capability — Flexible coil inner diameters and tube dimensions allow adaptation to specific ESP housing geometries and process requirements.
- Full Traceability — Every coil is traceable to its mill heat number, enabling complete supply chain accountability and quality assurance.
- Multi-Grade Availability — From standard AISI 304 to high-performance AISI 310S, customers can select the optimal grade for their specific service environment.
- Technical Support — Wenzhou Jixing Metal Materials Co., Ltd provides engineering consultation for thermal calculations, coil layout design, and system integration for specialized applications such as ESP wall panel heating.