Stainless Steel Coil Tube — Shell-and-Coil Heat Exchanger Grade

Product Overview

The Stainless Steel Coil Tube (盘管 / Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered continuous tubing product formed into a compact helical or spiral coil configuration. This product is specifically designed for integration into Shell-and-Coil Heat Exchangers (SCHE), where it serves as the primary heat transfer element within a closed shell enclosure. The coil tube architecture maximizes heat exchange surface area per unit volume, offering superior thermal performance compared to conventional straight-tube heat exchanger designs.

Unlike traditional shell-and-tube heat exchangers that rely on discrete tube bundles, the coil tube configuration provides a continuous, uninterrupted flow path that minimizes dead zones, reduces fouling accumulation, and enhances turbulence-induced heat transfer coefficients. This product line is compatible with both stainless steel and titanium material grades, accommodating a wide range of aggressive chemical and thermal environments.

Material & Properties

The coil tube is fabricated from high-purity austenitic stainless steel and titanium alloys, selected for their exceptional corrosion resistance, mechanical integrity under thermal cycling, and long-term service reliability in demanding industrial conditions.

Primary Material Grades

Key Physical & Mechanical Properties

Property 304 / 304L 316 / 316L 321 Titanium Gr. 2 Ti-6Al-4V (Gr. 5)
Density (g/cm³) 8.0 8.0 8.0 4.51 4.43
Tensile Strength (MPa) ≥ 515 ≥ 515 ≥ 485 ≥ 275 ≥ 895
Yield Strength (MPa) ≥ 205 ≥ 205 ≥ 205 ≥ 138 ≥ 828
Elongation (%) ≥ 40 ≥ 40 ≥ 35 ≥ 24 ≥ 10
Thermal Conductivity (W/m·K, 25°C) 16.3 14.6 16.3 21.9 6.7
Maximum Service Temperature (°C) 870 870 870 400 400
Chloride Pitting Resistance Moderate High Moderate Excellent Excellent

Specifications

Parameter Specification / Range Standard Reference
Outer Diameter (OD) 3.0 mm – 50.8 mm (1/8" – 2") ASTM A213 / A269
Wall Thickness 0.3 mm – 3.0 mm ASME B36.19M
Coil Diameter (Mean) 50 mm – 300 mm Custom / Customer-Specified
Coil Pitch 3.0 mm – 15.0 mm Custom / Customer-Specified
Tubing Length per Coil 5 m – 120 m (continuous) —
Surface Finish Bright Annealed, Electropolished (Ra ≤ 0.4 μm), or Commercial Pickled ASTM A269 / AMS 2700
End Treatment Flat, Beveled, Threaded, or Fitted with Weld Ends Customer-Specified
Pressure Rating Up to 25.0 MPa (3,625 psi) at 25°C ASME VIII Div. 1
Operating Temperature Range −196°C (LN₂) to +870°C (SS grades) —
Forming Tolerance (OD) ± 0.05 mm (precision coils) —
Forming Tolerance (Pitch) ± 0.10 mm —
Delivery Condition Cold-worked (CW), Solution Annealed (SA), or Strain Hardened (SH) ASTM A213 / A269

Manufacturing Process

The production of high-quality stainless steel coil tubes follows a rigorous multi-stage manufacturing workflow, ensuring dimensional precision, metallurgical integrity, and surface finish quality suitable for critical heat exchanger service.

  1. Raw Material Selection & Incoming Inspection:

    High-purity stainless steel or titanium wire rod is sourced from certified mill suppliers. Each batch undergoes spectroscopic chemical analysis (OES / XRF) to verify alloy composition compliance with ASTM / AMS specifications. Certificates of Conformance (CoC) and Mill Test Reports (MTR) are reviewed and archived.

  2. Pipe Forming & Sizing:

    Wire rod is converted into seamless tubing via Autoclave (Audi) tube forming or Drawn & Annealed (D&A) processes. The resulting straight tubes are then cold-drawn through precision dies to achieve the target outer diameter and wall thickness with tight tolerances.

  3. Coil Forming (Cold Bending):

    Strain-hardened straight tubes are fed through a CNC-controlled coil forming machine equipped with precision roller guides. The tube is continuously bent into a helical coil at a controlled rate to prevent plastic deformation, kinking, or wall thinning. Critical forming parameters include bend radius, pitch uniformity, and residual stress management.

  4. Solution Annealing & Pickling:

    Formed coils are subjected to a solution annealing cycle in a controlled-atmosphere furnace (typically 1050–1150°C for stainless steel) to relieve cold-work stresses, restore full ductility, and homogenize the microstructure. The coils are then pickled and passivated to remove oxide scale and form a protective chromium oxide passive layer.

  5. Surface Finishing:

    For applications requiring ultra-low surface roughness (e.g., pharmaceutical, semiconductor, or food-grade), coils undergo electropolishing in a controlled DC electrolytic process, achieving surface roughness values of Ra ≤ 0.4 μm. This process simultaneously removes surface contamination and enhances corrosion resistance.

  6. Hydrostatic & Non-Destructive Testing:

    Each coil tube is subjected to hydrostatic pressure testing (typically at 1.5× design pressure for a minimum 30-second hold) to verify weld integrity and structural soundness. Additional eddy current testing (ECT) and visual inspection are performed to detect surface defects, cracks, or dimensional deviations.

  7. Final Dimensional Verification & Packaging:

    Completed coil tubes are measured for OD, wall thickness, coil diameter, pitch, and total length using calibrated instruments. Each coil is individually packaged with protective end caps, desiccant, and labeled with a unique traceability tag linking to its full quality documentation.

Applications

The Stainless Steel Coil Tube is a versatile heat transfer component deployed across a broad spectrum of industrial and commercial applications:

Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that every coil tube product meets or exceeds international standards:

Unique Selling Points

1. Superior Thermal Efficiency: The continuous helical coil geometry generates inherent turbulence within the tube, significantly increasing the convective heat transfer coefficient (h) by 30–50% compared to straight tubes of equivalent diameter. This translates to a 20–40% reduction in required heat transfer surface area for the same thermal duty.
2. Compact Footprint: Coil tubes achieve up to 3× higher heat transfer surface density (m²/m³) than conventional tube bundles, enabling dramatically smaller heat exchanger vessels and reduced capital and installation costs.
3. Fouling Resistance: The continuous flow path eliminates tube-to-tube dead zones and stagnant areas where fouling deposits typically accumulate.