Stainless Steel Coil Tube for Water-Jacketed Heating Furnace Applications
Product Overview
The Stainless Steel Coil Tube (Product No. 948) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed specifically for integration into water-jacketed heating furnace systems (Water-Jacketed Heating Furnace). These coil tubes serve as critical heat exchange elements within industrial furnaces, where they facilitate efficient thermal transfer while withstanding extreme operating conditions including high temperatures, thermal cycling, and exposure to corrosive flue gases and scale-forming compounds.
The coil tube geometry provides an optimized surface-area-to-volume ratio, enabling superior heat absorption and dissipation characteristics compared to straight tube configurations. This product is engineered to resist fouling (scaling) accumulation — a prevalent operational challenge in water-jacketed heating systems — through careful material selection, surface finishing, and dimensional precision.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel grades, selected for their exceptional resistance to oxidation, thermal fatigue, and scale adhesion under furnace operating conditions.
- Primary Grade: AISI 304 / 304L (UNS S30400 / S30403) — General-purpose austenitic stainless steel offering excellent corrosion resistance and weldability.
- High-Temperature Grade: AISI 310S (UNS S31008) — Enhanced resistance to high-temperature oxidation and scaling, suitable for furnace temperatures exceeding 1100 °C.
- Alternative Grade: AISI 321 (UNS S32100) — Titanium-stabilized austenitic stainless steel providing superior resistance to intergranular corrosion during heat treatment.
Key Mechanical Properties:
- Tensile Strength (Ultimate): ≥ 520 MPa (304); ≥ 515 MPa (310S)
- Yield Strength: ≥ 205 MPa (304); ≥ 205 MPa (310S)
- Elongation: ≥ 40% (304); ≥ 40% (310S)
- Maximum Continuous Service Temperature: 870 °C (304); 1150 °C (310S)
- Thermal Conductivity: 16.3 W/(m·K) at 100 °C
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 10 mm – 108 mm (custom sizes available) | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 6.0 mm | ASTM A213 / GB/T 12771 |
| Coil Bend Radius | 50 mm – 500 mm (configurable per application) | Custom / Client-Specified |
| Coil Length (Uncoiled) | Up to 12,000 mm per coil | — |
| Surface Finish | 2B, BA (Bright Annealed), or Polished | ASTM A480 |
| Surface Roughness (Ra) | ≤ 0.8 μm (BA finish); ≤ 0.4 μm (Polished) | ISO 1302 |
| Tolerance on OD | ±0.05 mm – ±0.15 mm (per diameter class) | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Coil Packing | Wooden crate / Pallet with protective wrapping | ISO 4180 |
| Heat Treatment | Solution Annealed (1050–1150 °C) followed by water quench | ASTM A473 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and resistance to operational fouling:
- Raw Material Selection: Cold-rolled stainless steel strip (coil) is sourced from certified mills, with chemical composition verified via Optical Emission Spectroscopy (OES) and Positive Material Identification (PMI).
- Coil Winding / Bending: The flat strip is wound onto a precision mandrel using CNC-controlled coiling equipment to achieve the specified bend radius without introducing plastic deformation, cracking, or work hardening in the material.
- Welding (if applicable): Seams are formed using Automatic Metal Inert Gas (MIG) welding or TIG welding with argon gas shielding to prevent oxidation. Weld penetration is verified through non-destructive testing (NDT).
- Heat Treatment: Solution annealing at 1050–1150 °C in a protective atmosphere (argon or vacuum) followed by controlled cooling to dissolve carbides and restore full austenitic microstructure.
- Pickling and Passivation: Acid pickling (nitric/hydrofluoric acid blend) removes oxide scale; subsequent passivation forms a protective chromium oxide film (Cr₂O₃) on the surface.
- Surface Finishing: Mechanical polishing or electro-polishing is applied to achieve ultra-smooth surface roughness, minimizing the adhesion of scale and deposit formation during furnace operation.
- Quality Inspection: Dimensional verification, hydrostatic pressure testing, and surface defect inspection per ASTM A213 requirements.
Applications
The stainless steel coil tube is engineered for demanding industrial thermal processing applications, including but not limited to:
- Water-Jacketed Heating Furnaces: Primary application — coil tubes circulate cooling water within furnace walls to control shell temperature and protect structural components.
- Industrial Heat Exchangers: Used in shell-and-coil heat exchangers for process heating and cooling in chemical, pharmaceutical, and food processing industries.
- Boiler Tube Assemblies: Integration into water-tube boilers and waste heat recovery systems.
- Annealing Furnaces: Coil configurations for continuous annealing lines in metal processing.
- Power Generation: Auxiliary heating and cooling circuits in power plant equipment.
Fouling Prevention Considerations
Based on operational experience with water-jacketed heating furnace systems, the following design features are incorporated to prevent and mitigate coil tube fouling (scale deposition):
- Optimized Water Flow Velocity: Coil geometry is designed to maintain water flow velocities between 1.5–3.0 m/s, preventing stagnation and promoting turbulent flow that inhibits particulate and mineral deposit accumulation.
- Smooth Internal Surface: Ultra-low surface roughness (Ra ≤ 0.4 μm) significantly reduces the nucleation sites for calcium carbonate (CaCO₃) and magnesium hydroxide (Mg(OH)₂) scale formation.
- Uniform Heat Distribution: Coil spacing and diameter are calculated to avoid localized hot spots that accelerate scaling kinetics.
- Material Selection for Anti-Scale Properties: High-purity austenitic grades with low carbon content (≤ 0.03% C for 304L) minimize chromium carbide precipitation, maintaining passive film integrity.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 — Type 3.1 Test Certificate provided with each shipment
- ASTM A213 / A269 — Compliance with American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tube
- GB/T 12771 — Chinese National Standard for welded stainless steel tubes for general applications
- CE Marking — Conformity with European directives for pressure equipment
Unique Selling Points
1. Anti-Fouling Engineering Design: Unlike conventional coil tubes, this product incorporates lessons learned from field experience in water-jacketed heating furnace applications. The optimized coil geometry, ultra-smooth surface finish, and material purity collectively reduce fouling rates by an estimated 40–60%, extending maintenance intervals and reducing unplanned downtime.
2. Precision Dimensional Control: CNC coiling technology ensures consistent bend radius and tube geometry, guaranteeing uniform heat transfer performance and ease of integration into existing furnace systems.
3. Full Traceability: Each coil tube batch is accompanied by a complete material traceability record including mill test certificates, chemical analysis reports, and dimensional inspection data.
4. Custom Engineering Support: Wenzhou Jixing offers tailored coil configurations — including custom bend radii, lengths, and end treatments — to match specific furnace design requirements.
Technical Data Summary
| Property | 304 / 304L | 310S | 321 |
|---|---|---|---|
| Chromium (Cr) | 18.0 – 20.0% | 24.0 – 26.0% | 17.0 – 19.0% |
| Nickel (Ni) | 8.0 – 10.5% | 19.0 – 22.0% | 9.0 – 12.0% |
| Carbon (C, max) | 0.08% / 0.03% | 0.15% | 0.08% |
| Max. Service Temp. (°C) | 870 | 1150 | 925 |
| Corrosion Resistance | Excellent | Outstanding | Excellent |
| Scale Resistance | Good | Excellent | Good |
For further technical inquiries, custom specifications, or sample requests, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. All products are manufactured in accordance with applicable international and national standards and are subject to rigorous pre-shipment quality assurance protocols.