Stainless Steel Coil Tube for Boiler Scale Treatment Systems — GLC-60-Ⅱ Series
Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed specifically for integration into steam boiler water scale treatment systems, including the GLC-60-Ⅱ type steam car boiler descaling apparatus. These coil tubes serve as critical heat-exchange and fluid-circulation elements within industrial boiler maintenance systems, enabling efficient thermal transfer and controlled chemical treatment of scale deposits on boiler internal surfaces.
Coil tubes are formed by cold-bending continuous lengths of stainless steel tubing into helical or serpentine configurations, providing maximum surface area within a compact volume. This geometry is essential for applications requiring rapid heat exchange, chemical circulation, and uniform thermal distribution in high-pressure boiler environments.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for its exceptional resistance to corrosion, scale adhesion, and thermal fatigue under repeated heating and cooling cycles typical of boiler operations.
- Base Material: Austenitic Stainless Steel (奥氏体不锈钢), commonly grades 304 (UNS S30408) or 316L (UNS S31603) for enhanced chloride resistance
- Corrosion Resistance: Superior resistance to acidic descaling agents (e.g., hydrochloric acid, citric acid solutions) used in GLC-60-Ⅱ scale removal processes
- Temperature Tolerance: Continuous operating temperature up to 350°C; intermittent tolerance up to 870°C
- Mechanical Strength: Yield strength ≥ 205 MPa (Grade 304); Tensile strength ≥ 515 MPa
- Surface Finish: Mirror-polished (Ra ≤ 0.4 μm) or sanitary-grade electropolished interior to minimize scale re-deposition
- Thermal Conductivity: 16.3 W/(m·K) at 20°C, ensuring efficient heat propagation throughout the coil assembly
- Non-magnetic Properties: Austenitic microstructure ensures non-magnetic behavior, critical for certain instrumented boiler systems
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 14 mm – 51 mm (customizable) | ASTM A269 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / GB/T 12771 |
| Bend Radius | ≥ 3D (D = tube outer diameter) | ISO 4427 |
| Coil Length | Up to 50 m per continuous coil (spooled) | Manufacturer specification |
| Operating Pressure | Up to 1.6 MPa (standard); 4.0 MPa (reinforced) | GB/T 1538 |
| Maximum Operating Temperature | 350°C (continuous); 870°C (intermittent) | ASTM A269 |
| Minimum Bend Diameter | ≥ 14 mm OD for cold bending applications | ISO 4427 |
| Surface Treatment | Pickled & Passivated (P&P); optional electropolishing | ASTM A967 |
| End Condition | Plain cut, beveled, threaded, or flanged | Customer specification |
| Packaging | Wooden spool or protective coil rack with moisture barrier | ISO 4180 |
Manufacturing Process
- Raw Material Selection & Inspection: Certified stainless steel seamless or welded tubing is procured per ASTM A269 or GB/T 12771 standards. Each batch undergoes spectroscopic analysis (PMI), chemical composition verification, and mechanical testing prior to processing.
- Heat Treatment & Annealing: Incoming tubing is solution-annealed at 1040–1150°C followed by controlled air cooling to restore full austenitic microstructure and eliminate residual stresses from prior forming operations.
- Dimensional Verification: Optical and ultrasonic thickness gauging ensures OD, wall thickness, and straightness tolerances comply with ±0.1 mm (OD) and ±10% (wall) specifications.
- Coil Forming (Cold Bending): Precision CNC coil-bending machinery forms the tubing into the required helical or serpentine geometry. The bending process employs mandrel-supported tooling to prevent ovalization, wrinkling, and thinning at bend radii. Bend radius is maintained at a minimum of 3× tube OD to preserve structural integrity.
- Post-Form Annealing (Optional): For applications requiring full mechanical property restoration, the formed coil undergoes a low-temperature stress-relief anneal at 650–750°C in a protective atmosphere.
- Pickling & Passivation: The coil tube assembly is immersed in a nitric-hydrofluoric acid solution to remove mill scale and oxidation products, followed by passivation with dilute nitric acid to establish a stable chromium oxide protective film (minimum 10–20 nm thickness).
- Non-Destructive Testing (NDT): Hydrostatic pressure testing at 1.5× working pressure, eddy-current inspection for wall thickness verification, and visual examination of weld joints (for welded coil configurations).
- Packaging & Dispatch: Completed coil tubes are wound onto protective wooden spools or coiled onto steel racks with inner-diameter protective plugs. Each unit is labeled with a unique batch traceability code, material certificate reference, and dimensional data.
Applications
Primary Application: Boiler Scale Treatment (GLC-60-Ⅱ Type)
The coil tube serves as the core circulation and heat-transfer element in GLC-60-Ⅱ type steam car boiler descaling systems. In this application, the coil tube functions as follows:
- Chemical Circulation Pathway: The helical geometry provides an extended flow path for acidic descaling solutions (typically 5–10% HCl or citric acid) to circulate through the boiler interior, maximizing contact time with scale deposits.
- Thermal Activation: Integrated heating elements or external steam supply heats the circulating solution to 60–80°C, accelerating the chemical dissolution of calcium carbonate (CaCO₃) and magnesium hydroxide [Mg(OH)₂] scale formations.
- Pressure Containment: The coil tube maintains system pressure integrity during the descaling cycle, preventing solution leakage and ensuring uniform distribution throughout the boiler heat-transfer surfaces.
Additional Applications
- Industrial Steam Boiler Systems: Heat-transfer coils in fire-tube and water-tube boilers for power generation, chemical processing, and marine propulsion
- Food & Pharmaceutical Processing: Sanitary-grade coil heat exchangers in pasteurization, sterilization, and CIP (Clean-in-Place) systems
- Chemical Processing: Reactor cooling coils and distillation column internals requiring corrosion resistance to aggressive process media
- Heat Recovery Systems: Exhaust gas heat exchangers and waste-heat recovery units in industrial furnaces
- Marine & Shipbuilding: Boiler economizer coils and condensate recovery systems in marine power plants
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems ensuring compliance with international and national standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- GB/T 19001-2016 — Chinese National Quality Management Standard
- Material Certification: EN 10204 3.1 Certificate of Compliance for each production batch
- Pressure Vessel Standards: Compliance with GB/T 150 (Chinese National Standard for Pressure Vessels) and PED 2014/68/EU (EU Pressure Equipment Directive) for applicable components
- Welding Qualification: ISO 3834-2 (Full Quality Requirements) for any welded coil assemblies
- Third-Party Inspection: Available upon customer request through SGS, BV (Bureau Veritas), or TÜV inspection agencies
Unique Selling Points
Specialized Boiler Descaling Expertise: The GLC-60-Ⅱ coil tube is purpose-engineered for the demanding environment of steam boiler scale removal, where conventional tubing fails due to acid corrosion and thermal cycling fatigue. The combination of austenitic stainless steel, precision coil geometry, and controlled surface finish provides a service life exceeding 5× that of carbon steel alternatives in descaling applications.
- Custom Coil Geometry: CNC-forming capability allows bespoke helical, serpentine, and multi-pass configurations tailored to specific boiler internal dimensions and flow requirements
- Full Traceability: Each coil tube is traceable from raw material heat number through all manufacturing operations, ensuring complete quality documentation for regulatory compliance
- Electropolished Interior Option: Reduces surface roughness to Ra ≤ 0.2 μm, minimizing scale re-deposition and facilitating easy cleaning in food-grade and pharmaceutical applications
- Integrated Heat Treatment: Post-forming stress-relief annealing ensures dimensional stability and prevents spring-back during installation, reducing field-fabrication requirements
- Multi-Grade Availability: Options include 304, 304L, 316, 316L, 321 (UNS S32101) for high-temperature service, and 904L for extreme corrosion environments
- Comprehensive Testing: Every coil tube undergoes 100% hydrostatic testing, ultrasonic wall-thickness verification, and visual inspection — not just sampling
Technical Notes
When integrating the GLC-60-Ⅱ coil tube into boiler descaling systems, engineers should observe the following design parameters:
- Maximum flow velocity within the coil tube should not exceed 3 m/s to prevent erosion-corrosion of the internal surface
- Descaling solution residence time within the coil should be maintained at 2–4 hours for complete scale dissolution
- Post-descaling, a neutralization and flushing cycle using sodium bicarbonate solution (pH 7–8) is recommended to restore the passive film integrity
- For continuous descaling operations exceeding 100 cycles, periodic eddy-current thickness monitoring is advised to detect localized thinning
Wenzhou Jixing Metal Materials Co., Ltd. provides full engineering support, including CAD modeling, finite element analysis (FEA) of coil stress distributions, and on-site installation guidance for all coil tube products in the GLC series.