Stainless Steel Coil Tube — Organic Heat Carrier Furnace Application Series
Product Code: 1089 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) product line manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is engineered for demanding thermal-fluid systems, particularly organic heat carrier furnaces (also known as thermal oil heaters). These coils are fabricated from high-grade austenitic stainless steel and delivered in continuous coiled configurations to facilitate installation in heat exchangers, fired heaters, and process piping systems operating under elevated temperature and pressure conditions.
The operational safety and thermal performance of coil-type organic heat carrier furnaces are governed by the hydraulic behavior of the circulating heat transfer fluid. A thorough theoretical analysis utilizing the Reynolds Number (Re) — the dimensionless ratio of inertial forces to viscous forces in a fluid flow — provides critical insight into the transition between laminar and turbulent flow regimes within the coil geometry. This fluid-dynamic analysis is essential for ensuring adequate heat transfer coefficients, preventing localized overheating, and maintaining the integrity of the tube wall material under sustained thermal cycling.
Reynolds Number: Re = ρvD/μ, where ρ is fluid density (kg/m³), v is fluid velocity (m/s), D is the hydraulic diameter of the tube (m), and μ is the dynamic viscosity of the heat transfer fluid (Pa·s). For organic heat carrier fluids, a Reynolds number exceeding 10,000 typically ensures fully turbulent flow, which is the design target for optimal heat transfer performance and safe operation.
2. Material & Properties
2.1 Base Alloy Grades
The coil tube is manufactured from premium austenitic stainless steel grades selected for their superior corrosion resistance, thermal stability, and mechanical integrity at elevated operating temperatures:
- SUS304 / AISI 304 (UNS S30400) — Chromium-Nickel austenitic stainless steel (18Cr-8Ni), offering excellent general corrosion resistance and formability.
- SUS316L / AISI 316L (UNS S31603) — Low-carbon Chromium-Nickel-Molybdenum austenitic stainless steel (18Cr-10Ni-2Mo), providing enhanced resistance to pitting and crevice corrosion, particularly in chloride-containing environments.
- SUS310S / AISI 310S (UNS S31008) — High-temperature Chromium-Nickel austenitic stainless steel (25Cr-20Ni), designed for sustained service at temperatures up to 1150°C with excellent oxidation resistance.
2.2 Mechanical Properties
| Property | SUS304 | SUS316L | SUS310S |
|---|---|---|---|
| Tensile Strength (MPa, min.) | 515 | 485 | 515 |
| Yield Strength (MPa, min. 0.2% offset) | 205 | 170 | 205 |
| Elongation (% min., 50 mm gauge) | 40 | 40 | 40 |
| Density (kg/m³, at 20°C) | 8000 | 8000 | 8000 |
| Thermal Conductivity (W/m·K, at 100°C) | 16.3 | 14.6 | 26.2 |
| Coefficient of Thermal Expansion (10⁻⁶/K, 20–100°C) | 17.3 | 16.0 | 18.0 |
| Maximum Service Temperature (°C) | 870 | 870 | 1150 |
2.3 Chemical Composition (Typical, wt%)
| Element | SUS304 | SUS316L | SUS310S |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 |
| Cr (Chromium) | 18.0 – 20.0 | 16.5 – 18.5 | 24.0 – 26.0 |
| Ni (Nickel) | 8.0 – 10.5 | 10.0 – 14.0 | 19.0 – 22.0 |
| Mo (Molybdenum) | — | 2.0 – 3.0 | — |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 | ≤ 0.055 |
| Si (Silicon) | ≤ 0.75 | ≤ 0.75 | ≤ 1.50 |
| Fe (Iron) | Bal. | Bal. | Bal. |
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ 12 mm – Φ 114.3 mm (customizable) |
| Wall Thickness | 0.5 mm – 6.0 mm (customizable) |
| OD Tolerance | ± 0.1 mm (standard); ± 0.05 mm (precision grade) |
| Wall Thickness Tolerance | ± 10% (standard); ± 5% (precision grade) |
| Coil Inner Diameter (ID) | Φ 200 mm – Φ 600 mm |
| Coil Length per Piece | 50 m – 500 m (adjustable per order) |
| Surface Finish | Ba&P (Bright & Pickled), No. 4 Brushed, or Mirror Polished (2B / 2D / #8) |
| End Condition | Plain ends, beveled ends, or threaded ends (as specified) |
| Bending Radius | ≥ 5D (cold bend); ≥ 3D (hot bend) |
| Operating Pressure Range | Up to 4.0 MPa (design-dependent) |
| Operating Temperature Range | −40°C to +650°C (SUS304/316L); −40°C to +1150°C (SUS310S) |
| Heat Transfer Fluid Compatibility | Mineral-based thermal oils, synthetic organic heat transfer fluids, Dowtherm, Therminol, and equivalent fluids |
| Packaging | Wooden crate with moisture-proof wrapping, protective end caps |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement & Inspection: Cold-rolled stainless steel strip is sourced from certified mill producers (e.g., POSCO, Outokumpu, ThyssenKrupp, or domestic equivalents) and subjected to incoming inspection including chemical composition verification (via Optical Emission Spectrometry — OES), mechanical property testing, and surface quality assessment per ASTM E165.
- Slitting & Leveling: The stainless steel strip is slit to the required width using a precision slitting line and leveled to eliminate coil set and ensure flatness tolerances of ≤ 0.15 mm/m.
- Cold Forming / Tube Milling: The leveled strip is fed through a multi-stand rotary draw or roll-forming tube mill. Progressive forming rolls shape the strip into a seamless tube with controlled wall thickness and ovality. The process is performed at ambient temperature to preserve the cold-worked mechanical properties and achieve tight dimensional tolerances.
- Welding (if applicable):strong> For welded coil tube configurations, a Transverse Seam Welding (TSW) or Longitudinal Seam Welding (LSW) process is employed using Gas Tungsten Arc Welding (GTAW/TIG) with inert gas shielding (Argon — Ar). Weld parameters are optimized to achieve full penetration with minimal heat-affected zone (HAZ) distortion.
- Heat Treatment & Annealing: Where required, the formed tube undergoes solution annealing at 1040–1120°C followed by controlled water quenching to restore full austenitic microstructure, eliminate residual stresses, and maximize corrosion resistance. For SUS316L and low-carbon grades, annealing also prevents sensitization and intergranular corrosion susceptibility.
- Pickling & Passivation: The annealed tube is subjected to acid pickling (using a mixture of nitric acid and hydrofluoric acid) to remove scale and oxide layers, followed by passivation to establish a protective chromium oxide film on the surface.
- Coiling & Spooling: The finished tube is wound onto a precision coiling mandrel to form the final coil configuration. Tension is carefully controlled to prevent kinking, ovality, or plastic deformation during coiling.
- Final Inspection & Testing: Each coil undergoes comprehensive final inspection including dimensional measurement (OD, wall thickness, coil diameter), hydrostatic pressure testing (to 1.5× design pressure), eddy current testing (ECT) for internal and external defects, and visual surface examination.
5. Applications
5.1 Organic Heat Carrier Furnaces (Thermal Oil Heaters)
The primary application domain for this coil tube product is in the construction of organic heat carrier furnaces — systems that use synthetic or mineral-based thermal oils as the heat transfer medium to transfer thermal energy to industrial processes. The coil geometry provides a high surface-area-to-volume ratio, enabling efficient heat absorption from the furnace burner and transfer to the circulating oil. The Reynolds number analysis of the oil flow within the coil is critical for:
- Ensuring turbulent flow (Re > 10,000) to maximize convective heat transfer coefficients and prevent the formation of hot spots or thermal decomposition zones on the tube inner wall.
- Verifying that the oil velocity within the coil remains within the manufacturer-specified range (typically 0.8–2.5 m/s) to avoid both inadequate heat transfer (low velocity) and excessive erosion or pressure drop (high velocity).
- Validating that the pressure drop across the coil circuit does not exceed the capacity of the circulation pump, which would compromise system flow rate and thermal performance.
5.2 Additional Application Areas
- Chemical Processing Industry: Reactor jacket cooling coils, distillation column internals, and heat exchanger bundles for corrosive chemical service.
- Petrochemical & Refinery: Process heating and cooling coils, furnace radiant sections, and overhead line piping in crude oil and petroleum refining units.
- Pharmaceutical Industry: Steam sterilization coils, reactor heating/cooling loops, and clean-in-place (CIP) piping systems requiring high-purity, corrosion-resistant tubing.
- Food & Beverage Processing: Pasteurization and sterilization heat exchangers, cooking and heating coils, and process piping compliant with food-grade requirements.
- Power Generation: Auxiliary heating systems, boiler feedwater preheating coils, and thermal management circuits in combined heat and power (CHP) installations.
- Textile & Paper Industry: Drying oven heating coils, calender heating systems, and process steam distribution networks.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certification portfolio to assure customers of consistent product quality and regulatory compliance:
6.1 Quality Management Systems
- ISO 9001:2015 — Quality Management Systems certification
- ISO 14001:2015 — Environmental Management Systems certification
- ISO 45001:2018 — Occupational Health and Safety Management Systems certification
6.2 Product Standards & Specifications
| Standard | Description |
|---|---|
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Fertilizer Industry Service |
| ASTM A312 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tube for High-Pressure and High-Temperature Boilers and Heat Exchangers |
| ASME SA-269 / SA-312 | Boiler and Pressure Vessel Code — Material Specifications for Stainless Steel Tube |
| GB/T 14976 | Chinese National Standard — Seamless Stainless Steel Tubes for Fluid Transport |
| GB/T 12771 | Chinese National Standard — Welded Stainless Steel Tubes for Fluid Transport |
| EN 10216-5 | European Standard — Heat Exchangers and Related Equipment — Tubes of Austenitic and Austenitic-Ferritic Stainless Steels |