Stainless Steel Coil Tube (Coil Pipe) for Heat Carrier Furnace Applications
1. Product Overview
The Stainless Steel Coil Tube (Coil Pipe) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous tube product designed primarily for thermal fluid transfer systems, particularly for use in the convective sections of heat carrier heating furnaces. These coil tubes are arranged in multi-layer configurations and are integral to the efficient heat exchange process in industrial furnaces utilizing thermal oil (heat transfer fluid) as the medium.
Coil tubes offer significant advantages over straight tube assemblies in compact furnace designs, including reduced footprint, improved heat transfer surface area per unit volume, and enhanced structural resilience under thermal cycling conditions. The product is specifically engineered to accommodate soot blowing structures (Soot Blowing Structure Design) positioned between dual-layer coil tube banks within the convective zone, ensuring sustained thermal efficiency and operational reliability in demanding industrial environments.
2. Material & Properties
Stainless steel coil tubes are fabricated from high-quality austenitic stainless steel grades, selected for their exceptional corrosion resistance, thermal stability, and mechanical strength under elevated temperature conditions.
2.1 Commonly Used Grades
- SUS304 / AISI 304 (UNS S30408): General-purpose austenitic stainless steel offering excellent corrosion resistance and formability. Suitable for moderate-temperature heat transfer applications up to approximately 870°C (1598°F).
- SUS316L / AISI 316L (UNS S31603): Enhanced molybdenum-bearing grade providing superior resistance to pitting and crevice corrosion. Recommended for applications involving chlorinated heat transfer media or aggressive chemical environments.
- SUS321 / AISI 321 (UNS S32100): Titanium-stabilized grade with improved resistance to intergranular corrosion, suitable for sustained high-temperature service conditions.
- SUS310S / AISI 310S (UNS S31008): High-temperature grade with excellent oxidation resistance, applicable for furnace convective sections operating at temperatures exceeding 1000°C (1832°F).
2.2 Key Mechanical & Physical Properties (Typical for SUS304)
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (Tensile Strength, σb) | ≥ 520 MPa | ASTM A269 / ASTM A213 |
| Yield Strength (Yield Strength, σ0.2) | ≥ 205 MPa | ASTM A269 / ASTM A213 |
| Elongation (Elongation, A50) | ≥ 40% | ASTM A269 / ASTM A213 |
| Thermal Conductivity (Thermal Conductivity, k) | 16.3 W/(m·K) at 100°C | ASME Boiler & Pressure Vessel Code |
| Maximum Service Temperature (Maximum Service Temperature) | 870°C (1598°F) [SUS304]; 1093°C (2000°F) [SUS310S] | ASTM A213 |
| Surface Finish (Surface Finish) | 2B, No.4, No.8, or BA (Bright Annealed) | ASTM A480 |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name (Product Name) | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Product Series No. (Product Series No.) | 822 |
| Outer Diameter (Outer Diameter, OD) | Φ9.5 mm – Φ57 mm (customizable upon request) |
| Wall Thickness (Wall Thickness, WT) | 0.5 mm – 3.0 mm |
| Coil Pitch (Coil Pitch, P) | 15 mm – 100 mm (adjustable per design requirements) |
| Coil Diameter (Coil Diameter, D) | 100 mm – 600 mm |
| Tube Length per Coil (Tube Length per Coil) | 5 m – 500 m (continuous coil supply) |
| Manufacturing Standard (Manufacturing Standard) | ASTM A269, ASTM A213, GB/T 12771, GB/T 14976 |
| Heat Treatment (Heat Treatment) | Solution Annealing (Solution Annealing) at 1050°C – 1150°C followed by water quench |
| End Condition (End Condition) | Plain, Beveled, or Threaded (per customer specification) |
| Surface Treatment (Surface Treatment) | Pickling & Passivation (Pickling & Passivation) available |
| Maximum Operating Pressure (Maximum Operating Pressure) | Up to 2.5 MPa (typical for thermal fluid systems) |
| Heat Transfer Medium (Heat Transfer Medium) | Thermal Oil / Heat Transfer Fluid (HTF) |
4. Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage manufacturing process that ensures dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection (Raw Material Selection): Procurement of certified stainless steel strip or bar stock meeting ASTM/GB specifications, with verified chemical composition and mechanical properties.
- Forming & Coiling (Forming & Coiling): Precision roll-forming or mandrel-drawing processes are employed to shape the tube into a continuous helical coil configuration. The coil pitch and diameter are controlled within ±0.5 mm tolerance.
- Welding (Welding): For seamless coil tubes, cold-drawn or hot-rolled seamless processes are used. Where welded construction is required, TIG (Tungsten Inert Gas) welding is performed under argon shielding to maintain internal surface quality and prevent oxidation.
- Solution Annealing (Solution Annealing): Tubes are heated to 1050°C–1150°C in a controlled atmosphere furnace to relieve residual stresses, restore full austenitic microstructure, and enhance corrosion resistance.
- Pickling & Passivation (Pickling & Passivation): The surface is treated with a nitric/hydrofluoric acid solution to remove oxide scale and mill scale, followed by passivation to establish a protective chromium oxide layer.
- Quality Inspection (Quality Inspection): Comprehensive inspection including dimensional measurement, hydrostatic pressure testing, ultrasonic flaw detection (Ultrasonic Flaw Detection, UT), and visual surface examination.
5. Applications
Stainless steel coil tubes are widely employed across multiple industrial sectors, with particular emphasis on thermal fluid heating systems:
- Heat Carrier Furnace Convective Sections (Heat Carrier Furnace Convective Section): Dual-layer coil tube banks are arranged in the convective zone of thermal oil furnaces. The inter-layer soot blowing structure (Soot Blowing Structure) is designed to periodically remove accumulated particulate deposits (ash and soot), maintaining optimal heat transfer efficiency and preventing fouling-related thermal degradation.
- Thermal Oil Heating Systems (Thermal Oil Heating Systems): Coil tubes serve as heat exchange surfaces in indirect-fired thermal oil furnaces used in petrochemical, food processing, and polymer manufacturing industries.
- Industrial Boilers & Waste Heat Recovery (Industrial Boilers & Waste Heat Recovery): Utilized in superheaters, economizers, and air preheaters for efficient waste heat capture.
- Chemical Processing (Chemical Processing): Resistant to a wide range of corrosive media, making coil tubes suitable for chemical reactors and heat exchangers.
- Food & Pharmaceutical Industry (Food & Pharmaceutical Industry): Hygienic-grade surface finishes (BA finish) meet sanitary requirements for processing equipment.
- Power Generation (Power Generation): Applied in auxiliary heating systems and condensate recovery units.
6. Unique Selling Points
- Multi-Layer Coil Configuration with Integrated Soot Blowing Compatibility: The coil tube design is specifically compatible with inter-layer soot blowing structures, enabling automated cleaning of deposits between coil banks without operational shutdown, thereby extending maintenance intervals and improving overall thermal efficiency.
- Continuous Coil Supply: Delivered as a continuous coil eliminates the need for field welding of individual tube segments, reducing installation labor, minimizing leak points, and ensuring uniform thermal performance.
- Thermal Cycling Resilience: The austenitic stainless steel microstructure provides superior resistance to thermal fatigue, ensuring long service life under repeated heating and cooling cycles typical in furnace applications.
- Customizable Geometric Parameters: Coil pitch, diameter, and tube dimensions can be tailored to specific furnace design requirements, enabling optimal heat transfer surface area and flow dynamics within the convective zone.
- Comprehensive Material Traceability: Each coil tube batch is accompanied by mill test certificates (Mill Test Certificates, MTC) with full chemical and mechanical property documentation.
7. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System (Quality Management System) certification ensuring consistent product quality and process control. |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severities of Service. |
| ASTM A213 | Standard Specification for Seamless Austenitic Stainless Steel Tubing for High-Temperature Service. |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Conveyance. |
| GB/T 14976 | Chinese National Standard for Cold-Drawn Stainless Steel Tubes for Fluid Conveyance. |
| ASME BPVC Section IX | Welding qualification standards for pressure-bearing applications. |
| EN 10216-5 | European Standard for Stainless Steel Tubes for Heat Exchangers and Similar Applications. |
8. Technical Notes on Soot Blowing Structure Integration
In heat carrier furnace convective sections, coil tubes are typically arranged in two or more parallel layers. The inter-layer soot blowing structure (Inter-Layer Soot Blowing Structure) is designed to deploy rotating or reciprocating soot blowers through dedicated ports between coil layers. This design ensures that accumulated deposits on the tube surfaces are effectively removed, preventing the formation of insulating ash layers that would otherwise reduce heat transfer coefficients and increase fuel consumption. The coil tube geometry must be designed with adequate inter-pitch clearance (typically ≥ 25 mm between adjacent coil layers) to accommodate the soot blowing mechanism and ensure unobstructed cleaning coverage across the entire tube surface.
Wenzhou Jixing Metal Materials Co., Ltd provides engineering consultation and custom coil tube solutions tailored to specific furnace configurations, ensuring seamless integration with soot blowing systems and optimal thermal performance throughout the operational lifecycle.