Spiral Heating Coil Tube (盘管) — Technical Product Specification

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州集兴金属材料有限公司)
Product Reference No.: 714
Classification: Stainless Steel Coil Tube — Spiral Heating Type

1. Product Overview

The Spiral Heating Coil Tube (螺旋型加热盘管) is a precision-engineered tubular component manufactured from high-grade austenitic stainless steel, specifically designed for industrial heating, heat exchange, and thermal transfer applications. Unlike conventional straight heating elements, the spiral geometry provides a significantly increased surface-area-to-volume ratio, enabling superior heat dissipation efficiency within compact installation envelopes.

These coil tubes are fabricated through a specialized cold- or hot-forming process that imparts a uniform helical profile while preserving the metallurgical integrity of the base material. The resulting product delivers consistent thermal performance, extended service life, and resistance to thermal fatigue cycling — making it a critical component in high-temperature industrial processes.

2. Material & Properties

2.1 Base Material Grades

2.2 Mechanical Properties (Typical Values — Annealed Condition)

Property SUS304 SUS316L SUS310S SUS321
Tensile Strength (MPa) ≥ 520 ≥ 485 ≥ 485 ≥ 515
Yield Strength (MPa, 0.2% offset) ≥ 205 ≥ 170 ≥ 205 ≥ 205
Elongation (%) ≥ 40 ≥ 45 ≥ 40 ≥ 40
Maximum Service Temperature (°C) 870 925 1150 1000
Density (g/cm³) 8.0 8.0 8.0 8.0
Thermal Conductivity at 100 °C (W/m·K) 16.3 14.6 31.5 16.3
Linear Expansion Coefficient (10⁻⁶/°C, 20–100 °C) 17.3 16.0 18.5 17.3

2.3 Surface Finish Options

3. Specifications

Parameter Specification Range
Outer Diameter (OD) 6.0 mm – 50.8 mm (¼" – 2")
Wall Thickness 0.5 mm – 3.0 mm
Coil Diameter (Helical Pitch Diameter) 50 mm – 500 mm
Coil Length (Straightened / As-Coiled) Custom — typically 1 m – 12 m
Coil Pitch (Center-to-Center Spacing) 10 mm – 100 mm (configurable)
Number of Turns 3 – 200 (application-dependent)
End Preparation Plain cut, beveled, threaded, flanged, or socket-welded
Tolerance on OD ±0.1 mm (custom tolerances available)
Tolerance on Wall Thickness ±10% of nominal
Helical Profile Tolerance ±0.5 mm on pitch diameter; ±2° on helix angle
Delivery Form Coiled, straightened, or pre-assembled sub-components

4. Manufacturing Process

The fabrication of spiral heating coil tubes involves a multi-stage process combining precision tube forming, helical bending, and post-processing to ensure dimensional accuracy and metallurgical soundness. The following process flow represents the standard manufacturing sequence:

4.1 Process Flow

  1. Raw Material Inspection: Incoming stainless steel seamless or welded tube stock is verified against material certificates (MTC), with spectroscopic analysis confirming chemical composition compliance.
  2. Cut-to-Length: Tube blanks are cut to required lengths using automated plasma or saw cutting, with burr-free end preparation.
  3. End Forming / Threading: End connections are machined per drawing specifications — including NPT threads, socket weld preparation, or flange attachment.
  4. Helical Coiling (Bending): The tube is wound around a precision mandrel or formed using a CNC-controlled spiral bending machine. The critical parameters — coil diameter, pitch, and number of turns — are controlled within tight tolerances. Cold forming is preferred for smaller diameters (≤ 25 mm OD) to preserve surface quality; hot forming may be employed for larger diameters or thicker walls.
  5. Stress Relief Annealing: Post-forming annealing at 1050–1150 °C (furnace or induction) relieves residual stresses introduced during bending, restores full annealed mechanical properties, and prevents cold-work hardening effects that could lead to stress corrosion cracking.
  6. Pickling & Passivation: The coiled tube is immersed in a mixed acid solution (typically HNO₃/HF or H₂SO₄/HNO₃) to remove any oxide scale or discoloration, followed by passivation to re-establish the protective chromium oxide film.
  7. Dimensional Inspection & Non-Destructive Testing (NDT): Final inspection includes OD/wall thickness measurement, helix geometry verification, and hydrostatic pressure testing (typically 1.5–2.0× working pressure) to ensure leak-tight integrity. Radiographic or eddy current testing may be applied for critical applications.
  8. Packaging & Dispatch: Finished coil tubes are individually wrapped in protective film or VCI (Volatile Corrosion Inhibitor) paper, secured in wooden or steel crates, and shipped with accompanying material traceability documentation.

4.2 Key Process Considerations

Helix Angle Optimization: The spiral angle (typically 15°–45° from the coil axis) directly influences heat transfer efficiency. A steeper helix angle increases the projected surface area and promotes turbulence in the internal fluid, enhancing convective heat transfer coefficients by 20–40% compared to straight tubes of equivalent length.

Springback Compensation: During cold coiling, elastic springback causes the coil diameter to expand slightly after removal from the mandrel. Advanced CNC bending systems incorporate real-time compensation algorithms to achieve the target helix geometry within ±0.5 mm tolerance.

5. Applications

The Spiral Heating Coil Tube finds widespread use across multiple industrial sectors due to its compact geometry, high heat-transfer efficiency, and corrosion-resistant construction:

5.1 Primary Applications

5.2 Industry-Specific Standards Compliance

6. Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure consistent product performance and regulatory compliance:

6.1 Management System Certifications

6.2 Product & Process Certifications

6.3 Inspection & Testing Protocols

7. Unique Selling Points

  1. Optimized Spiral Geometry: Precision CNC helical forming ensures uniform pitch and coil diameter, delivering repeatable thermal performance and minimizing turbulent flow losses.
  2. Multi-Grade Material Flexibility: Availability across SUS304, SUS316L, SUS310S, and SUS321 grades allows selection tailored to specific temperature, corrosion, and mechanical requirements.
  3. Compact Footprint with High Efficiency: The spiral configuration achieves up to 40% greater heat-transfer surface area per unit volume compared to straight-tube equivalents, enabling space-constrained installations without performance compromise.
  4. Full Traceability: Each production batch is accompanied by a complete material test certificate (EN 10204 3.1), ensuring end-to-end traceability from mill certificate to finished product.
  5. Custom Engineering Capability: OEM (Original Equipment Manufacturer) support for custom coil diameters, pitches, end preparations, and length configurations to meet specific customer drawings and specifications.
  6. Extended Service Life: Post-forming stress-relief annealing eliminates cold-work effects, significantly reducing the risk of stress corrosion cracking (SCC) and fatigue failure in cyclic thermal environments.

8. Ordering Information

To place an order or request a quotation, customers should provide the following information:

This technical specification is provided for informational and reference purposes. All dimensions, properties, and process parameters are subject to verification against applicable standards and customer-specific requirements. Wenzhou Jixing Metal Materials Co., Ltd. reserves the right to update specifications based on technological advancements and regulatory changes.