Stainless Steel Coil Tube (盘管) — Boiler Application Grade

1. Product Overview

The Stainless Steel Coil Tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司) is a precision-engineered tubular product designed primarily for boiler systems, heat exchangers, and high-temperature industrial applications. Coil tubes are formed from seamless or welded stainless steel pipe stock into continuous helical or serpentine configurations, enabling compact heat transfer surfaces within constrained spatial footprints.

This product line addresses critical industrial needs including boiler water circulation systems, superheater and reheater assemblies, economizers, and low-pressure steam generation units. The coil geometry maximizes heat exchange efficiency while maintaining structural integrity under cyclic thermal loading conditions.

2. Material & Properties

2.1 Common Material Grades

2.2 Key Physical & Mechanical Properties (Typical for Grade 304)

Property Value Unit
Density (密度) 7.93 g/cm³
Melting Range (熔化范围) 1400 – 1450 °C
Thermal Conductivity (热导率, at 100 °C) 16.3 W/(m·K)
Specific Heat Capacity (比热容) 500 J/(kg·K)
Tensile Strength (抗拉强度, minimum) 515 MPa
Yield Strength (屈服强度, 0.2% offset) 205 MPa
Elongation (延伸率, minimum) 40 %
Modulus of Elasticity (弹性模量) 193 GPa
Coefficient of Thermal Expansion (热膨胀系数, 20–100 °C) 17.3 × 10⁻⁶/°C
Maximum Service Temperature (最高使用温度) 870 °C
Corrosion Resistance (耐蚀性) Excellent in oxidizing acids; good in atmospheric conditions —

2.3 Chemical Composition (Typical for Grade 304, wt%)

Element (元素) C Si Mn P S Cr Ni N Fe
Maximum / Nominal 0.08 1.00 2.00 0.045 0.030 18.00–20.00 8.00–10.50 0.10 Balance

3. Specifications

3.1 Dimensional Specifications

Parameter (参数) Specification (规格)
Outer Diameter (外径, OD) Φ6 – Φ108 mm (standard range); custom sizes available upon request
Wall Thickness (壁厚) 0.5 – 6.0 mm; tolerance ±10% or per ASTM A213
Coil Diameter (盘管外径) 300 – 3000 mm (adjustable per application requirement)
Coil Length (盘管展开长度) 5 – 200 m per coil (custom lengths available)
Pitch / Spacing (间距) Configurable: 10 – 50 mm center-to-center spacing
Number of Turns (圈数) 2 – 500 turns depending on coil geometry
End Condition (端部处理) Plain end, beveled end, threaded end, or flanged end
Surface Finish (表面状态) Mill finish (热轧态), pickled & passivated (酸洗钝化), polished (抛光)
Delivery Form (交货形式) Coiled (盘卷装), cut-to-length (定尺), or pre-formed assemblies (成型组件)

3.2 Governing Standards & Specifications (执行标准)

Standard (标准) Description (说明)
ASTM A213 / A213M Standard Specification for Seamless Austenitic Stainless Steel Tubing for High-Temperature Service
ASTM A269 Standard Specification for Welded Austenitic Stainless Steel Tubing
GB/T 12771 Chinese National Standard for Stainless Steel Tubes for General Purposes
GB/T 14976 Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport
EN 10216-5 European Standard for Heat Exchanger Tubes and Heat Sink Tubes — Austenitic Stainless Steel
ASME SA-213 American Society of Mechanical Engineers Specification for Boiler Tubes
ISO 3506 International Standard for Stainless Steel Tubes — Dimensions and Masses

4. Manufacturing Process

4.1 Production Workflow

  1. Raw Material Inspection (原材料检验): Incoming stainless steel pipe stock is verified against mill test certificates (MTC), chemical composition analysis (spectroscopic analysis per ASTM E415), and dimensional tolerance checks (per ASTM A213/A269).
  2. Heat Treatment (热处理): Annealing at 1050–1100 °C followed by controlled cooling to relieve residual stresses from prior forming operations and restore full austenitic microstructure. Solution annealing ensures optimal corrosion resistance and mechanical properties.
  3. Pickling & Passivation (酸洗钝化): Immersion in mixed acid solution (nitric acid + hydrofluoric acid blend) to remove mill scale, oxidation films, and surface contaminants. Subsequent passivation treatment forms a chromium oxide protective layer.
  4. Coil Forming (盘管成型): Pipe stock is cold-bent into helical or serpentine configurations using precision coil-forming machines. Forming parameters (bend radius, pitch, tension) are controlled to prevent wall thinning, ovality distortion, or micro-cracking. Minimum bend radius is typically 3× OD for Grade 304.
  5. Welding (焊接) [if applicable]: For welded coil assemblies, TIG (Tungsten Inert Gas) welding per ASME Section IX is employed. Back-purging with argon or nitrogen prevents internal oxidation. Weld parameters are qualified through Welding Procedure Qualification Records (WPQR).
  6. Post-Forming Heat Treatment (成型后热处理): Stress-relief annealing at 870–900 °C to recover ductility and eliminate forming-induced residual stresses, particularly critical for coils operating under cyclic thermal loading.
  7. Non-Destructive Testing (无损检测, NDT):
    • Visual Inspection (目视检验): Surface examination for defects, distortion, and weld quality.
    • Eddy Current Testing (涡流检测): Detection of surface and near-surface defects in both seamless and welded tubes.
    • Hydrostatic Testing (水压试验): Pressure testing at 1.5× working pressure to verify integrity and absence of leaks.
    • Dimensional Inspection (尺寸检验): Verification of OD, wall thickness, coil diameter, pitch, and overall geometry using calibrated instruments.
  8. Final Cleaning & Packaging (终清与包装): Thorough cleaning to remove handling oils and residues. Packaging with protective end caps, moisture-absorbing desiccants, and wooden or steel crates for transport.

4.2 Critical Process Controls — Boiler Coil Tube Blockage Prevention

Based on operational experience documented in 《锅炉盘管阻塞的检修》 (Inspection and Maintenance of Boiler Coil Tube Blockage), the following process controls are integral to ensuring long-term reliability:

5. Applications

5.1 Primary Application Domains