Stainless Steel Spiral Coil Tube (Coiltube) — Technical Specification

Product Code: WX-CT-1415  |  Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

The Stainless Steel Spiral Coil Tube (Coiltube) is a precision-engineered tubular component formed by continuously bending stainless steel seamless tube into a helical (spiral) configuration. This product is specifically designed for heat exchange, fluid conveyance, and thermal processing applications where compact geometry, uniform heat transfer characteristics, and superior corrosion resistance are paramount. The coil tube finds extensive application in industrial drying systems, particularly in helical coil drying equipment, where its geometry facilitates efficient convective and conductive heat transfer between a process medium and the surrounding material being dried.

1. Product Overview

The Spiral Coil Tube represents a class of continuously formed tubular elements that leverage the inherent advantages of a helical geometry to maximize surface-area-to-volume ratios within constrained installation footprints. Unlike conventional straight-pipe heat exchangers, coil tubes achieve turbulent flow conditions at relatively low Reynolds numbers due to the secondary Dean vortex generated by centrifugal forces acting on the fluid within the curved path. This results in enhanced heat transfer coefficients, typically 20%–40% higher than equivalent straight-tube configurations under identical operating conditions.

Wenzhou Jixing Metal Materials Co., Ltd. manufactures coil tubes to meet the rigorous demands of industrial drying, chemical processing, pharmaceutical manufacturing, and food-grade thermal systems. The product line encompasses both single-layer helical coils and multi-layer concentric coils, each optimized for specific thermal duty cycles and flow requirements.

Key Design Philosophy: The spiral coil tube integrates the mechanical robustness of seamless stainless steel tubing with the thermal efficiency of helical geometry, delivering a durable, high-performance component suitable for continuous industrial operation under aggressive chemical and thermal environments.

2. Material & Properties

Coil tubes are fabricated from a range of austenitic and duplex stainless steel grades, each selected based on the specific corrosive environment, temperature range, and mechanical stress conditions encountered during service.

2.1 Available Material Grades

2.2 Typical Mechanical Properties (Annealed Condition, SUS304)

Property Unit Typical Value
Tensile Strength (Rm) MPa ≥ 520
Yield Strength (Rp0.2) MPa ≥ 205
Elongation (A50) % ≥ 40
Hardness (HV) — ≤ 200
Density (ρ) g/cm³ 7.93
Thermal Conductivity (λ, 20°C) W/(m·K) 16.3
Thermal Conductivity (λ, 500°C) W/(m·K) 26.7
Specific Heat (Cp, 20°C) J/(g·K) 500
Linear Expansion Coefficient (α, 20–100°C) ×10⁻⁶/K 17.3

3. Specifications

3.1 Geometric Specifications

Parameter Range / Options Standard Reference
Outer Diameter (OD) 6.0 mm – 108.0 mm ASTM A269 / GB/T 12771
Wall Thickness 0.5 mm – 6.0 mm ASTM A269 / GB/T 12771
Coil Pitch (Center-to-Center) 10 mm – 200 mm (customizable) Per customer drawing
Coil Diameter (Mean) 50 mm – 2000 mm Per customer drawing
Number of Turns 1 – 500 (customizable) Per customer drawing
Tube Length (Developed) Up to 3000 m (continuous coil) —
End Preparation Plain, Beveled, Threaded, Flanged ASME B1.20.1 / ASME B16.5
Surface Finish Ra ≤ 0.8 μm (Polished); Ra ≤ 1.6 μm (Pickled) ASTM A270 / GB/T 14976

3.2 Performance Specifications

Parameter Specification
Maximum Operating Temperature Up to 1150°C (SUS310S); Up to 870°C (SUS304/316L)
Maximum Operating Pressure Up to 40 MPa (depending on OD, wall thickness, and grade)
Corrosion Resistance Excellent resistance to pitting, crevice corrosion, and Cl-SCC (316L, 2205, 904L grades)
Hygienic Compliance Available in electropolished finish (Ra ≤ 0.4 μm) for food/pharmaceutical applications
Weldability Excellent (austenitic grades); suitable for TIG/GTAW welding

4. Manufacturing Process

The production of stainless steel spiral coil tubes follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional accuracy, mechanical integrity, and surface quality. The process is outlined below:

  1. Raw Material Selection & Incoming Inspection:

    Seamless stainless steel tube blanks are sourced from certified mills and subjected to incoming quality control, including chemical composition verification (via optical emission spectrometry, OES), mechanical property testing, and visual surface inspection in accordance with ASTM A269 and applicable national standards.

  2. Tube Annealing & Stress Relief:

    Tubes are solution-annealed at temperatures between 1010°C and 1150°C (depending on grade) followed by controlled cooling to eliminate residual stresses from prior cold working and to restore full austenitic microstructure and maximum corrosion resistance.

  3. Coil Forming (Cold Bending):

    Continuous coil forming is performed using high-precision CNC-controlled bending machines equipped with adjustable forming rollers and a central mandrel to maintain internal tube geometry. The bending process is executed under controlled strain rates to prevent wall thinning, ovalization, or buckling. Key process parameters include:

    • Minimum bending radius: ≥ 3.0 × tube OD (to prevent excessive deformation)
    • Roller diameter ratio: optimized for uniform strain distribution
    • Forming speed: 0.5–5.0 m/min (grade-dependent)
  4. Post-Forming Heat Treatment (if required):

    For applications requiring enhanced mechanical properties or specific metallurgical conditions, a post-forming temper or solution anneal may be applied. This step restores ductility and eliminates cold-work hardening introduced during the forming process.

  5. Surface Finishing:

    Finished coils may undergo additional surface treatment depending on application requirements:

    • Pickling & Passivation: Acid bath treatment to remove oxide scale and form a protective chromium oxide passive layer (per ASTM A967).
    • Mechanical Polishing: Achieves Ra ≤ 1.6 μm surface roughness for general industrial use.
    • Electropolishing: Electrochemical finishing achieves Ra ≤ 0.4 μm for hygienic (food/pharmaceutical) applications (per ASTM A270, Grade 3).
  6. Dimensional Inspection & Quality Control:

    Each coil batch undergoes comprehensive dimensional and performance verification, including:

    • Coil diameter and pitch measurement (±0.5 mm tolerance)
    • Wall thickness measurement at multiple points along the coil (ultrasonic thickness gauge, UT)
    • Hydrostatic pressure testing at 1.5× maximum working pressure (per ASTM A269, Section 7)
    • Visual inspection for surface defects, deformation, or work hardening indicators
    • Chemical spot-check verification (OES analysis)
  7. Packaging & Dispatch:

    Finished coils are wrapped in protective film, secured on wooden pallets or steel racks, and labeled with full traceability documentation including material certification, heat number, and inspection report.

5. Applications

The stainless steel spiral coil tube is deployed across a broad spectrum of industrial and commercial applications where its unique geometry and material properties deliver superior performance:

5.1 Industrial Drying Systems

The primary application domain for the WX-CT-1415 coil tube is in helical coil drying equipment (螺旋盘管式干燥机). In these systems, the coil tube functions as the heat transfer element through which a heating medium (hot water, steam, or thermal oil) circulates, transferring thermal energy to the material being dried (typically granular or powdered solids). The helical geometry ensures:

5.2 Chemical & Petrochemical Processing

Coil tubes are extensively used in chemical reactors, heat exchangers, and distillation columns where aggressive process chemicals (acids, alkalis, halogenated compounds) demand high corrosion resistance. Grades such as 316L, 2205, and 904L are preferred for chloride-rich environments.

5.3 Pharmaceutical & Food Processing

Electropolished coil tubes (Ra ≤ 0.4 μm) conform to sanitary design requirements for pharmaceutical manufacturing and food processing. Applications include:

5.4 Power Generation & Energy

Coil tubes serve as heat transfer elements in boiler systems, solar thermal collectors, and geothermal heat exchange systems. High-temperature grades (310S, 321) are specified for furnace and combustion applications.

5.5 Aerospace & Defense

Lightweight, high-strength coil tubes are used in aerospace fuel systems, hydraulic lines, and thermal