Stainless Steel Helical Coil Tube (盘管 / Coiltube) — Technical Specification

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd (温州吉兴金属材料有限公司)

Product Code: 1600

Category: Literature Learning / Technical Reference

1. Product Overview

Stainless steel helical coil tubes (also referred to as coil tubes or盘管) are precision-engineered tubular products formed by winding seamless stainless steel pipe into a helical configuration. These products are widely employed in thermal exchange systems, industrial heating and cooling applications, and process engineering where compact heat transfer surface area and efficient fluid dynamics are critical. The helical geometry of the coil tube enhances turbulence within the fluid stream, significantly improving convective heat transfer coefficients compared to straight-tube configurations.

Wenzhou Jixing Metal Materials Co., Ltd specializes in the manufacturing and supply of high-quality stainless steel coil tubes, adhering to rigorous international standards. The company's product line encompasses a wide range of diameters, wall thicknesses, and coil configurations tailored to meet diverse industrial requirements. The following technical specification is derived from the company's internal literature learning program, specifically addressing the optimal conditions for selecting helical coil tube thermal performance (《选择螺旋盘管热性能的最佳条件》).

2. Material & Properties

2.1 Common Material Grades

2.2 Key Physical Properties (Typical for AISI 316L)

PropertySpecification
Density8.0 g/cm³
Thermal Conductivity (at 20°C)14.5 W/(m·K)
Specific Heat Capacity0.50 J/(g·K)
Coefficient of Thermal Expansion16.0 × 10⁻⁶ /K
Maximum Operating Temperature870°C (oxidation resistant)
Yield Strength (min.)170 MPa (0.2% offset)
Tensile Strength (min.)485 MPa
Corrosion ResistanceExcellent against pitting, crevice, and intergranular corrosion

2.3 Material Selection Criteria for Thermal Performance

Based on the literature learning program (《选择螺旋盘管热性能的最佳条件》), the optimal material selection for helical coil tubes is governed by the following principles:

  1. Thermal Conductivity Matching: The thermal conductivity of the tube material should be compatible with the working fluid's properties to minimize thermal resistance at the tube wall.
  2. Creep Resistance: For high-temperature applications, materials with superior creep strength (e.g., Alloy 625, Alloy 800H) should be selected to maintain structural integrity over extended service periods.
  3. Thermal Expansion Compatibility: The coefficient of thermal expansion (CTE) of the coil tube material must be compatible with the housing or support structure to prevent thermal stress-induced failure.
  4. Corrosion Resistance in Service Environment: Material selection must account for the chemical composition of the process fluid, including chloride concentration, pH levels, and oxidizing potential.
  5. Cost-Performance Optimization: A balance between material cost and performance longevity should be achieved through life-cycle cost analysis.

3. Specifications

3.1 Dimensional Specifications

ParameterRange / Standard
Tube Outer Diameter (OD)3 mm – 108 mm (1/8" – 4")
Tube Wall Thickness0.3 mm – 6.0 mm
Tube Length (per coil)1 m – 100 m (customizable)
Coil Inner Diameter (CID)50 mm – 2000 mm
Coil Outer Diameter (COD)100 mm – 3000 mm
Coil Height50 mm – 500 mm
Helix Pitch1.5 mm – 25 mm
End PreparationPlain, beveled, threaded, or welded to headers
Tolerance (OD)±0.05 mm – ±0.5 mm (per ASME B36.19M)
Surface FinishNo. 4 polished, 2B finish, or passivated

3.2 Thermal Performance Parameters

ParameterTypical Value / Range
Overall Heat Transfer Coefficient (U)500 – 2,500 W/(m²·K) (depending on fluid and flow regime)
Pressure Drop (ΔP)0.1 – 5.0 bar (per coil length, flow-dependent)
Reynolds Number (Re) — Turbulent Regime> 10,000 (enhanced by helical geometry)
Nusselt Number Enhancement1.5× – 3.0× compared to straight tube
Maximum Operating PressureUp to 40 bar (depending on wall thickness)

3.3 Applicable Standards

4. Manufacturing Process

4.1 Production Workflow

  1. Raw Material Procurement: Selection of certified stainless steel seamless or welded pipe from qualified mills, with full chemical composition and mechanical property verification.
  2. Incoming Inspection: Dimensional verification, visual examination, and material certification (Mill Test Report / MTR) validation.
  3. Surface Preparation: Cleaning and degreasing of the tube surface to ensure proper forming and prevent contamination.
  4. Coil Forming (Bending): The straight tube is fed into a precision coil winding machine equipped with mandrel support to form the helical geometry. Critical parameters include:
    • Bend radius control (minimum bend radius ≥ 4× tube OD to prevent ovalization)
    • Tooling material selection (hardened steel or ceramic-coated dies)
    • Winding speed and tension control
    • Pitch consistency monitoring
  5. Stress Relief (if required): Post-forming annealing treatment at 850°C – 1,100°C (depending on grade) to relieve residual stresses introduced during cold forming.
  6. End Processing: Cutting, deburring, beveling, threading, or welding of end connections to headers or manifolds.
  7. Heat Treatment (if applicable): Solution annealing and pickling to restore corrosion resistance and achieve desired microstructure.
  8. Passivation: Chemical treatment (citric acid or nitric acid-based) to enhance surface passivation and remove free iron contamination.
  9. Quality Inspection: Dimensional verification, hydrostatic pressure testing, visual examination, and non-destructive testing (NDT) as required.
  10. Packaging and Delivery: Protective wrapping, labeling with product identification, and secure packaging for transportation.

4.2 Key Manufacturing Considerations for Thermal Performance

As emphasized in the learning material (《选择螺旋盘管热性能的最佳条件》), the manufacturing parameters that most significantly influence the thermal performance of helical coil tubes include:

  • Helix Diameter-to-Tube Diameter Ratio (D/d): A ratio of 20–40 provides optimal balance between heat transfer enhancement and pressure drop.
  • Pitch-to-Diameter Ratio (p/d): Typically 1.0–2.0 for enhanced turbulence generation.
  • Surface Roughness: Controlled surface roughness (Ra 0.4–1.6 μm) optimizes the trade-off between friction factor and heat transfer coefficient.
  • Uniformity of Coil Geometry: Deviations in coil diameter and pitch create flow maldistribution, reducing overall thermal efficiency.

5. Applications

5.1 Primary Industrial Applications

5.2 Selection Guidance for Application-Specific Performance

ApplicationRecommended GradeKey Design Consideration
General Chemical Processing316LPitting corrosion resistance
High-Temperature Service (>600°C)321 / 347 / Alloy 625Creep resistance and oxidation resistance
Seawater / Chloride Environment2205 Duplex / 2507 Super DuplexResistance to chloride stress corrosion cracking (SCC)
Food & Pharmaceutical304L / 316LSanitary finish, low carbon content
Acid ProcessingAlloy C-276 / Alloy 625Resistance to reducing acids
Low-Temperature / Cryogenic304L / 316LMaintained ductility at cryogenic temperatures

6. Quality Certifications

6.1 Company Certifications

6.2 Product Testing and Inspection

  1. Chemical Analysis: Full chemical composition verification via optical emission spectroscopy (OES) or inductively coupled plasma (ICP) analysis.
  2. Mechanical Testing: Tensile testing, hardness testing (Rockwell/Brinell), and impact testing (Charpy V-notch) per ASTM A370.
  3. Hydrostatic Pressure Testing: Performed at 1.5× working pressure for a minimum dwell time of 10 seconds, per ASTM A269.
  4. Dimensional Inspection: Verification of OD, wall thickness, coil diameter, pitch, and overall dimensions using precision measuring instruments.
  5. Visual Inspection: Examination of surface finish, weld quality, and absence of defects (cracks, laps, seams).
  6. Non-Destructive Testing (NDT): Eddy current testing (ECT) for weld inspection, magnetic particle testing (MT) for surface defects, and ultrasonic testing (UT) for internal flaws.
  7. Intergranular Corrosion Testing: ASTM A240 Practice 2 or Practice 6 for grades requiring sensitization resistance verification.
  8. Heat Treatment Verification: Microstructural examination to confirm proper solution treatment and absence of carbide precipitation.

6.3 Documentation Provided

7. Unique Selling Points