Stainless Steel Coil Tube (Coil Tube) — Product No. 307

1. Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube" or "盘管") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specializing in coiled configurations of austenitic stainless steel tubing. Unlike conventional straight-length piping, Coil Tubes are formed into continuous helical or spiral geometries, offering superior surface-area-to-volume ratios that make them indispensable in heat exchange, fluid distribution, and cooling applications.

This product line is particularly suited for industrial thermal management systems, including technical water supply cooling circuits, where compact heat dissipation footprints and high thermal efficiency are critical. The Coil Tube is available in a wide range of diameters, wall thicknesses, coil pitches, and total coil lengths to accommodate diverse engineering requirements.

2. Material & Properties

2.1 Base Material Grades

Coil Tubes are fabricated from high-quality austenitic stainless steel, with the following grades commonly offered:

2.2 Mechanical Properties (Typical — Grade 304, Annealed Condition)

Property Specification Unit
Tensile Strength (Rm) ≥ 520 MPa
Yield Strength (Rp0.2) ≥ 205 MPa
Elongation (A) ≥ 40 %
Density 7.93 g/cm³
Thermal Conductivity (at 100°C) 16.3 W/(m·K)
Thermal Expansion Coefficient (20–100°C) 16.0 × 10⁻⁶ 1/K
Maximum Service Temperature 870 °C
Corrosion Potential (Ecorr in 3.5% NaCl) ≥ -0.200 V (vs. SCE)

2.3 Chemical Composition (Grade 304 — Typical)

Element C Si Mn P S Cr Ni N
Max / Min (%) 0.08 1.00 2.00 0.045 0.030 18.00–20.00 8.00–10.50 0.10

3. Specifications

3.1 Geometric & Dimensional Parameters

Parameter Range / Value Notes
Outer Diameter (OD) Φ6.0 – Φ108.0 mm Custom sizes available upon request
Wall Thickness (WT) 0.30 – 6.00 mm ±0.10 mm tolerance
Coil Pitch (Center-to-Center Spacing) 3.0 – 50.0 mm Configurable per application thermal load
Total Coil Length 1.0 – 500.0 m (per unit) Continuous or segmented supply
Coil Diameter (Bundle OD) Φ50 – Φ2000 mm Adaptable to heat exchanger shell dimensions
Number of Coils per Bundle 1 – 50 Multi-coil assemblies available
End Preparation Plain, Beveled, Threaded (G/BSPT/NPT), Flanged Per customer drawing
Surface Finish 2B, BA (Bright Annealed), Electropolished (Ra ≤ 0.4 μm), Pickled Custom finish available
Hardness (Annealed) ≤ 200 HV10 Work-hardened variants: up to 350 HV10

3.2 Applicable Standards & Specifications

4. Manufacturing Process

The production of high-precision Stainless Steel Coil Tubes follows a rigorously controlled multi-stage manufacturing workflow:

  1. Raw Material Procurement & Inspection — Certified stainless steel bars or seamless/welded tubes are sourced from approved mills. Incoming material undergoes spectrographic analysis (OES), chemical composition verification, and mechanical property testing to ensure conformance to specified grades.
  2. Coil Forming (Bending & Coiling) — Straight tubes are fed through CNC-controlled bending machines that apply controlled radial and axial forces to form precise helical geometries. The forming process employs die sets calibrated for specific OD/WT combinations, ensuring uniform curvature without wall thinning, ovality exceeding 0.5%, or micro-cracking.
  3. Heat Treatment (Annealing) — Post-forming stress-relief annealing is performed at 1050–1150°C followed by controlled cooling (air or furnace cooling) to restore full solution-annealed microstructure, eliminate residual stresses, and ensure maximum corrosion resistance and ductility.
  4. Pickling & Passivation — The annealed surface is treated with dilute nitric acid/hydrofluoric acid mixtures to remove oxide scale, followed by passivation to establish a stable chromium oxide (Cr₂O₃) protective film on the surface.
  5. Surface Finishing — Depending on the application, surfaces may undergo mechanical polishing, electropolishing (to achieve Ra ≤ 0.4 μm), or brushing to meet specified finish requirements.
  6. Dimensional Inspection & Non-Destructive Testing (NDT) — Each coil tube unit undergoes 100% dimensional verification (OD, WT, pitch, total length) using laser micrometers and coordinate measuring systems. Magnetic particle testing (MT) or eddy current testing (ECT) is performed to detect surface and near-surface defects. Hydrostatic pressure testing (typically 1.5× working pressure, held for 30 seconds) verifies weld integrity for welded variants.
  7. End Machining & Assembly — Tube ends are prepared per customer specifications (beveling, threading, flanging). Multi-coil bundles are assembled with stainless steel tie rods, spacers, and headers as required.
  8. Final Testing & Packaging — Completed assemblies pass final visual inspection, dimensional audit, and functional testing. Products are packaged in protective wrapping (VCI film, wooden crates) with complete traceability documentation.

5. Applications

5.1 Technical Water Supply Cooling Systems

A primary application domain for this Coil Tube product is in technical water supply system cooling circuits for large-scale pump stations. In such systems, the Coil Tube serves as the core heat exchange element, dissipating thermal energy generated by pump motors, lubrication systems, and hydraulic actuators. The compact helical geometry maximizes heat transfer area within constrained installation footprints, making it ideal for retrofit applications where spatial constraints limit the use of larger shell-and-tube exchangers.

Reference Application: The Coil Tube cooling unit was successfully deployed in the Songzhuang Pump Station Technical Water Supply System Retrofit Project, where it replaced legacy cooling components with improved thermal efficiency and reduced maintenance intervals. The self-contained coil tube cooler design demonstrated superior performance under continuous duty cycles, achieving stable outlet temperatures within ±1.5°C of design setpoint.

5.2 Additional Application Sectors

6. Quality Certifications & Compliance

6.1 Product Certifications

6.2 Material & Process Certifications

6.3 Quality Assurance Protocol

Inspection Stage Method Acceptance Criteria
Incoming Material OES Spectroscopy + Mechanical Testing 100% conformance to ASTM/EN chemical & mechanical specs
Post-Forming Laser Micrometer + Optical Comparator OD ±0.10 mm; Ovality ≤ 0.5%; Pitch ±0.5 mm
Post-Annealing Hardness Test
"Professional Coil Tubes, Professionally Made"
© 2026 Wenzhou Jixing Metal Materials Co., Ltd · This content is for technical reference only. Final order specifications are subject to the signed contract and mill test certificate.