Stainless Steel Coil Tube (Coil Tube) — Technical Specification
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1634) offers premium-grade Stainless Steel Coil Tubes (盘管, Coiltube) engineered for demanding industrial heat-transfer applications. These coil tubes are cold-formed into continuous helical or spiral configurations, providing high surface-area-to-volume ratios ideal for waste heat recovery systems, process heating, and thermal exchange environments. The product line is designed to withstand aggressive thermal cycling, chemical exposure, and mechanical fatigue over extended service life.
The coil tube geometry delivers superior convective heat transfer characteristics compared to straight-tube alternatives, making them indispensable in waste heat boiler systems, superheaters, economizers, and steam generators operating under high-temperature, high-pressure conditions.
Material & Properties
The stainless steel coil tubes are manufactured from corrosion-resistant austenitic and duplex stainless steel grades, selected to ensure long-term performance in oxidizing, reducing, and mixed gas environments typical of waste heat recovery applications.
- Primary Grades: AISI 304 (UNS S30408), AISI 316 (UNS S31608), AISI 321 (UNS S32108), AISI 310S (UNS S31008), and Duplex 2205 (UNS S31803)
- Mechanical Properties: Tensile strength ranging from 515 MPa to 760 MPa (depending on grade); elongation ≥ 35% at break
- Thermal Conductivity: 14–16 W/(m·K) for 304 grade; 12–14 W/(m·K) for 316 grade
- Maximum Service Temperature: Up to 1150°C for 310S grade; up to 870°C for 321 grade
- Corrosion Resistance: Excellent resistance to oxidation, sulfuric acid, phosphoric acid, and flue gas environments containing SO₂ and HCl
- Surface Finish: Bright annealed (BA), pickled and passivated (PP), or custom mill finish
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Product No. | 1634 |
| Outer Diameter (OD) | Φ9.5 mm – Φ60.3 mm (custom sizes available) |
| Wall Thickness | 0.5 mm – 4.0 mm |
| Coil Pitch (Helix Spacing) | 10 mm – 50 mm (configurable per design requirements) |
| Coil Diameter | 50 mm – 500 mm |
| Coil Length | Up to 50 m continuous (or custom lengths) |
| Material Grades | 304, 304L, 316, 316L, 321, 310S, 2205, 309 |
| Manufacturing Standard | ASTM A269, ASTM A213, GB/T 14976, EN 10216-5 |
| Surface Treatment | Pickled & Passivated, Bright Annealed |
| Maximum Working Pressure | Up to 25 MPa (pressure tested per specification) |
| Operating Temperature Range | −196°C to +1150°C (grade dependent) |
| Joining Method | TIG Welding (GTAW), Orbital Welding, Brazing |
| Packaging | Wooden crate, export-grade protective wrapping |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip is procured from certified mills with full chemical composition (CMC) and mill test reports (MTR) verification.
- Coil Forming: Precision CNC-controlled coil winding machines form the flat strip into helical tube geometry with controlled springback compensation. Forming speeds and die configurations are optimized to prevent work-hardening and micro-cracking.
- Welding: Longitudinal seams are welded using Gas Tungsten Arc Welding (GTAW/TIG) under inert gas shielding (argon or argon-helium mixture) to ensure full-penetration welds with minimal heat-affected zone (HAZ).
- Heat Treatment: Solution annealing at 1050°C–1150°C followed by controlled cooling to restore full austenitic structure and eliminate residual stresses introduced during forming and welding.
- Pickling & Passivation: Surface treatment using acid pickling (HNO₃ + HF blend or citric acid) to remove oxide scale, followed by passivation to establish a protective chromium oxide layer. This process is critical for resistance to flue gas corrosion in waste heat boiler applications.
- Quality Inspection: 100% visual inspection, dimensional verification (caliper, micrometer), hydrostatic pressure testing, and optional Non-Destructive Testing (NDT) including dye penetrant testing (PT) and ultrasonic testing (UT) for weld integrity.
Applications
Wenzhou Jixing's stainless steel coil tubes are engineered for the following high-performance industrial applications:
- Waste Heat Boiler Systems (废热锅炉): Primary application for flue gas heat recovery in cement kilns, glass furnaces, steel mills, and power generation plants. The coil geometry maximizes heat exchange efficiency in compact footprints.
- Superheaters & Economizers: Steam superheating and feedwater preheating in industrial boilers operating under high-temperature, high-pressure conditions.
- Chemical Processing: Heat exchange in chemical reactors where corrosion resistance to aggressive media (acids, alkalis, halogenated compounds) is essential.
- Petrochemical Industry: Crude oil distillation, catalytic cracking units, and hydrogen production systems requiring reliable heat transfer under cyclic thermal loads.
- Power Generation: Flue gas desulfurization (FGD) systems and waste-to-energy plant heat recovery systems.
- Food & Pharmaceutical Processing: Sanitary heat exchangers requiring hygienic surface finishes and compliance with FDA/3-A standards.
Scale Removal & Maintenance Considerations
In waste heat boiler applications, coil tubes are subject to scale deposition from flue gas particulates and condensate. Industry-standard cleaning protocols include:
- Hydrofluoric Acid (HF) – Hydrochloric Acid (HCl) Method: A controlled chemical cleaning process using diluted HF-HCl mixtures to dissolve iron oxide, calcium sulfate, and silicate deposits. This method is effective for moderate to heavy scale buildup but requires strict concentration control, temperature management (typically 30°C–60°C), and thorough rinsing to prevent intergranular corrosion or pitting.
- Acid Pickling: Post-cleaning pickling with nitric acid (HNO₃) to restore the passive chromium oxide film and ensure continued corrosion resistance.
- Mechanical Cleaning: Brushing or abrasive blasting for localized deposits, followed by passivation treatment.
Technical Advisory: Wenzhou Jixing recommends selecting 316L or duplex 2205 grade coil tubes for waste heat boiler applications subject to frequent scale removal cycles, as these grades offer superior resistance to acid attack during cleaning operations compared to standard 304 grade.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — European Conformity for pressure equipment and components
- PED 2014/68/EU — Pressure Equipment Directive compliance
- ASME — American Society of Mechanical Engineers stamp certification (available upon request)
- EN 10204 3.1 — Material Test Certificate (Mill Test Report) with third-party inspection
- Material Traceability: Full heat-number traceability from raw material mill through final product delivery
Unique Selling Points
- Precision Coil Geometry: CNC-controlled winding ensures consistent coil pitch and diameter, optimizing heat transfer performance and reducing flow resistance.
- Multi-Grade Capability: In-house availability of 304, 316, 321, 310S, and 2205 grades allows customers to match material selection precisely to operating environment and corrosion challenge.
- Waste Heat Boiler Expertise: Deep technical knowledge of scale formation mechanisms and cleaning protocols (including HF-HCl acid cleaning methods), enabling material and surface treatment recommendations that extend service life between maintenance intervals.
- Custom Engineering: Bespoke coil configurations, lengths, and surface treatments tailored to specific heat exchanger designs and process requirements.
- Full Traceability & Certification: Every coil tube batch is accompanied by complete material documentation, ensuring regulatory compliance and procurement audit readiness.
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 1634 | Classification: Literature & Technical Reference — Waste Heat Boiler Coil Tube Scale Removal (HF-HCl Method)