Stainless Steel Spiral Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd
Product Series: Coiltube (Spiral Coil Tubing) | Reference No.: 1626
Wenzhou Jixing Metal Materials Co., Ltd is a leading manufacturer of high-performance stainless steel coil tubes engineered for thermal processing, heat exchange, and industrial heating applications. This product line encompasses helical and spiral coil tubes designed in accordance with the principles outlined in advanced furnace engineering, including the design methodologies for Spiral Coil Cylindrical Heating Furnaces (螺旋盘管式圆筒加热炉). The coil tubes are precision-manufactured to deliver exceptional thermal efficiency, mechanical integrity, and long-term corrosion resistance in demanding industrial environments.
1. Product Overview
The Stainless Steel Spiral Coil Tube is a continuous length of stainless steel tubing formed into a helical or spiral configuration, designed to maximize surface area within a compact cylindrical or tubular envelope. This geometry is particularly advantageous in heat exchangers, heating furnaces, steam generators, and thermal oil systems where high heat transfer rates and uniform temperature distribution are critical.
Coiltube products are available in both cold-formed and hot-formed configurations, accommodating a wide range of tube diameters, wall thicknesses, and coil pitches. The spiral design ensures efficient fluid dynamics, minimizes dead zones, and promotes turbulent flow — all of which contribute to superior heat transfer performance.
Key Design Philosophy: The coil tube geometry follows the engineering principles of spiral coil cylindrical furnace design, where the helical arrangement of tubes optimizes the balance between heat absorption, structural rigidity, and thermal expansion accommodation.
2. Material & Properties
2.1 Available Grades
- AISI 304 (UNS S30400 / 08Cr18Ni10): The most widely used austenitic stainless steel for general-purpose coil tube applications. Offers excellent corrosion resistance, formability, and weldability. Suitable for temperatures up to 870°C in continuous service.
- AISI 304L (UNS S30403 / 022Cr18Ni10): Low-carbon variant of 304, preferred for applications requiring extensive welding with minimal sensitization risk. Carbon content ≤ 0.03%.
- AISI 316 (UNS S31600 / 06Cr17Ni12Mo2): Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion in chloride-containing environments. Ideal for chemical processing and marine applications.
- AISI 316L (UNS S31603 / 022Cr17Ni12Mo2): Low-carbon version of 316, recommended for welded coil assemblies exposed to elevated temperatures.
- AISI 321 (UNS S32100 / 06Cr18Ni11Ti): Titanium-stabilized austenitic grade providing enhanced resistance to intergranular corrosion. Suitable for high-temperature furnace coil applications up to 900°C.
- AISI 310S (UNS S31008 / 06Cr25Ni20): High-temperature austenitic grade with outstanding oxidation resistance. Designed for continuous service at temperatures up to 1150°C in furnace environments.
- AISI 347 (UNS S34700 / 06Cr18Ni11Nb): Niobium-stabilized grade offering excellent resistance to sensitization and intergranular corrosion at elevated temperatures.
2.2 Mechanical Properties (Typical Values — Annealed Condition)
| Property | 304 / 304L | 316 / 316L | 321 | 310S | 347 |
|---|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 | ≥ 515 | ≥ 515 |
| Yield Strength (0.2% Proof, MPa) | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (% min.) | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (kg/m³) | 8000 | 8000 | 8000 | 8000 | 8000 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 | 16.3 | 16.3 |
| Thermal Expansion 20–100°C (×10⁻⁶/K) | 17.2 | 17.2 | 17.2 | 17.2 | 17.2 |
| Maximum Continuous Service Temperature (°C) | 870 | 870 | 900 | 1150 | 900 |
2.3 Chemical Composition (Typical, % by Weight)
| Grade | C (max) | Cr | Ni | Mo | Ti | Nb | Si (max) | Mn (max) | S (max) | P (max) |
|---|---|---|---|---|---|---|---|---|---|---|
| 304 | 0.08 | 18.0–20.0 | 8.0–10.5 | — | — | — | 1.00 | 2.00 | 0.030 | 0.045 |
| 304L | 0.03 | 18.0–20.0 | 8.0–10.5 | — | — | — | 1.00 | 2.00 | 0.030 | 0.045 |
| 316 | 0.08 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — | 1.00 | 2.00 | 0.030 | 0.045 |
| 316L | 0.03 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | — | 1.00 | 2.00 | 0.030 | 0.045 |
| 321 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | 5×C–0.70 | — | 1.00 | 2.00 | 0.030 | 0.045 |
| 310S | 0.08 | 24.0–26.0 | 19.0–22.0 | — | — | — | 1.50 | 2.00 | 0.030 | 0.045 |
| 347 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | — | 10×C–1.00 | 1.00 | 2.00 | 0.030 | 0.045 |
3. Specifications
3.1 Geometric Dimensions
| Parameter | Range / Options | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 168.3 mm (¼" – 6") | ASTM A269 / ASME SA-269 |
| Wall Thickness | 0.5 mm – 6.0 mm (0.020" – 0.236") | ASTM A269 / ASME SA-269 |
| Coil Pitch (Center-to-Center Spacing) | Custom; typically 1.5× to 4.0× OD | Project-specific |
| Coil Diameter (Mean) | 150 mm – 3000 mm | Project-specific |
| Number of Turns | 5 – 500+ | Project-specific |
| Tube Length (Pre-Coil) | Up to 12,000 mm per continuous length | Manufacturer capability |
| End Preparation | Plain, Beveled, Threaded (NPT/BSP), Flanged, or Custom | ASME B1.20.1 / B18.1 |
| Surface Finish | Mill Finish (2B), Bright Annealed, Pickled & Passivated, Polished (Ra ≤ 0.8 μm) | ASTM A473 |
3.2 Applicable Standards & Specifications
- ASTM A269 / ASME SA-269: Standard Specification for Austenitic Stainless Steel Seamless, Welded, and Heavy-Welded Tubes for Chemical and Heat-Transfer Service
- ASTM A312 / ASME SA-312: Standard Specification for Austenitic Stainless Steel Seamless, Welded, and Heavy-Welded Boilers, Heat Exchanger, and Condenser Tubes
- ASTM A270: Standard Specification for Austenitic Stainless Steel Tube for Instrumentation, Condensers, and Heat Exchangers
- EN 10216-5: Seamless and Welded Steel Tubes for Technical Uses — Technical Delivery Conditions for Austenitic Stainless Steel Tubes
- ISO 3506: Stainless Steel Tubes — Technical Delivery Conditions
- GB/T 12771: Chinese National Standard for Stainless Steel Tubes for General Purposes
- GB/T 14976: Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport
3.3 Tolerance Classification
| Dimension | OD Tolerance | Wall Thickness Tolerance |
|---|---|---|
| Standard | ± 0.05 × OD (min ± 0.1 mm, max ± 0.5 mm) | ± 10% of nominal |
| Close | ± 0.025 × OD (min ± 0.05 mm, max ± 0.3 mm) | ± 5% of nominal |
| Ultra-Close | ± 0.01 × OD (min ± 0.025 mm, max ± 0.15 mm) | ± 3% of nominal |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection & Certification: Incoming stainless steel seamless or welded tube stock is verified against mill test certificates (MTC) for chemical composition, mechanical properties, and heat number traceability.
- End Preparation & Cleaning: Tube ends are cut, deburred, chamfered, and cleaned to ensure proper coil forming and subsequent welding. Surface contaminants are removed via pickling and passivation.
- Coil Forming (Cold or Hot):
- Cold Coiling: Tubes are formed at ambient temperature using CNC-controlled spiral coiling machinery. This method preserves the annealed mechanical properties and surface finish. Suitable for OD ≤ 63.5 mm and moderate coil diameters.
- Hot Coiling: For larger diameters or thicker wall tubes, the tube is heated to 800–1000°C and formed on a mandrel. This approach reduces forming forces and prevents work hardening. Post-forming annealing restores the solution-annealed microstructure.
- Welding (if multi-pass or multi-segment): Helical coils requiring multiple tube segments are joined using TIG (Gas Tungsten Arc Welding / GTAW) with inert gas (argon or argon-helium mixture) shielding. Weld seams undergo 100% visual inspection and spot radiographic testing.
- Heat Treatment & Anne