Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州继兴金属材料有限公司)
Product Catalog No.: 950
Classification: Stainless Steel Coil Pipe / Coil Tube (盘管)
Product Overview
The Stainless Steel Coil Tube (also referred to as Coil Pipe or Coiltube) is a precision-engineered continuous-length tubular product formed into a compact coil configuration. This product is manufactured from high-purity austenitic stainless steel grades and is designed to meet the rigorous demands of heat exchange, refrigeration, chemical processing, and gas cooling applications.
Coil tubes are distinguished from straight seamless or welded pipe by their continuous coil form, which offers superior storage efficiency, reduced handling waste, and enhanced flexibility in downstream fabrication. The coiled geometry is particularly advantageous for applications requiring long, uninterrupted tube lengths without joint interruptions—such as gas coolers, condensers, evaporators, and heat exchanger assemblies.
This specification draws upon documented technical knowledge regarding coil-type gas cooler cleaning technology and maintenance practices (《盘管式燃气冷却器清洗工艺与技术》), integrating operational insights to define performance expectations for coil tubes deployed in gas cooling service.
Material & Properties
2.1 Common Grades
- SAE 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- SAE 316 / 316L (UNS S31600 / S31603) — Enhanced resistance to chloride-induced pitting and crevice corrosion; preferred for aggressive chemical and marine environments.
- SAE 321 (UNS S32100) — Titanium-stabilized grade offering superior resistance to intergranular corrosion at elevated temperatures.
- SAE 310S (UNS S31008) — High-temperature grade suitable for sustained service above 800°C.
2.2 Mechanical Properties (Typical — Annealed Condition)
| Property | SAE 304 | SAE 316 / 316L | SAE 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (0.2% Offset, MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (% ≥ 50 mm) | ≥ 40 | ≥ 40 | ≥ 40 |
| Hardness (HBW, max) | ≤ 201 | ≤ 217 | ≤ 201 |
| Density (g/cm³) | 8.0 | 8.0 | 8.0 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
2.3 Chemical Composition (Typical, wt%)
| Element | SAE 304 | SAE 316L | SAE 321 |
|---|---|---|---|
| C | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 |
| Cr | 18.0–20.0 | 16.0–18.0 | 18.0–20.0 |
| Ni | 8.0–12.0 | 10.0–14.0 | 9.0–13.0 |
| Mo | — | 2.0–3.0 | — |
| Ti | — | — | 5 × (C × 100) – 0.70 (min) |
| Mn | ≤ 2.0 | ≤ 2.0 | ≤ 2.0 |
| S | ≤ 0.03 | ≤ 0.03 | ≤ 0.03 |
| P | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
2.4 Key Material Advantages
- Corrosion Resistance: The passive chromium oxide film provides inherent resistance to atmospheric, aqueous, and many chemical corrosives without requiring coatings or linings.
- Hygienic Surface: Low surface roughness (Ra ≤ 0.5 μm achievable) facilitates cleaning and prevents biofilm accumulation—critical for gas cooler and food-grade applications.
- Weldability: Austenitic grades offer excellent weldability, enabling reliable fabrication of coil tube assemblies with minimal distortion.
- Low Temperature Performance: No ductile-to-brittle transition; retains toughness at cryogenic temperatures down to −196°C.
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ 3.0 mm – Φ 25.4 mm (typical); custom sizes available up to Φ 50 mm | ASTM A554 / GB/T 12771 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm | ASTM A554 / GB/T 12771 |
| Coil Inner Diameter (CID) | Φ 100 mm – Φ 600 mm | Manufacturer specification |
| Coil Length (per coil) | 50 m – 500 m (continuous) | — |
| Tolerance on OD | ± 0.05 mm (precision); ± 0.10 mm (standard) | ASTM A554 |
| Tolerance on Wall Thickness | ± 10% of nominal (standard); ± 5% (precision) | ASTM A554 |
| Surface Finish | Bright annealed / Pickled and passivated (2B finish); Ra ≤ 0.5 μm (polished) | ASTM A473 / GB/T 4237 |
| End Condition | Plain end / Beveled / Flanged (on request) | — |
| Heat Treatment | Full annealing at 1050–1100°C followed by water quench | ASTM A473 |
| Applicable Standards | ASTM A554, ASTM A778, GB/T 12771, EN 10217-7, JIS G3459 | — |
| Packaging | Wooden pallet with moisture-proof wrapping; coil secured with steel straps | ISO 4180 |
Manufacturing Process
3.1 Process Flow
- Raw Material Procurement: High-purity stainless steel ingots or continuous casting slabs sourced from certified mills, verified for chemical composition and mechanical properties.
- Hot Rolling / Pipe Blank Preparation: Slabs are hot-rolled into flat strip or pipe blanks meeting dimensional tolerances for the target coil tube specification.
- Forming: Flat strip is rolled and formed into a tubular shape. For precision small-bore coil tubes, the ERW (Electric Resistance Welding) or FW (Furnace Welding) method is employed; for larger diameters, seamless piercing may be utilized.
- Welding (if applicable): Longitudinal seam welding with precise heat input control to minimize grain growth and maintain metallurgical integrity. Weld strength must meet ≥ 90% of base metal tensile strength.
- Heat Treatment (Annealing): The formed tube is fully annealed at 1050–1100°C in a protective atmosphere (hydrogen or nitrogen) to relieve residual stresses, homogenize microstructure, and restore full ductility.
- Pickling & Passivation: Chemical treatment to remove oxide scale, followed by passivation to re-establish the protective chromium oxide film. This step is critical for corrosion resistance and hygienic performance.
- Coiling: The continuous tube is wound into a compact coil of specified inner diameter using a controlled tension winding system to prevent kinking, ovality, or deformation.
- Quality Inspection: Comprehensive dimensional, visual, and non-destructive testing (see Section 6).
- Packaging & Shipping: Coils are wrapped, strapped, and palletized per export or domestic delivery standards.
3.2 Key Process Controls
- Dimensional Stability: Laser measurement systems monitor OD and wall thickness in real time during forming, with automated diameter control (ADC) systems ensuring consistency.
- Atmosphere Control: Annealing furnaces are equipped with dew point monitors to ensure oxygen levels remain below 10 ppm, preventing surface scaling.
- Coil Winding Tension: Precision-controlled hydraulic tension systems prevent inter-coil contact damage and maintain uniform coil geometry.
Applications
4.1 Primary Application Domains
| Application Sector | Specific Use Case | Relevant Requirements |
|---|---|---|
| Gas Cooling & Refrigeration | Coil-type gas coolers, condensers, evaporators, chiller coils | High thermal conductivity, corrosion resistance to refrigerants (R-410A, R-32, R-134a), cleanable surface |
| Chemical Processing | Reactor heat exchangers, distillation column internals, process piping coils | Resistance to acids, alkalis, and halide-containing process streams; pressure rating compliance |
| Food & Beverage Industry | Pasteurization coils, milk cooling systems, brewing heat exchangers | Hygienic surface finish (Ra ≤ 0.5 μm), FDA/3-A compliance, easy-to-clean geometry |
| Pharmaceutical & Biotech | CIP (Clean-In-Place) compatible heat exchangers, bioreactor cooling coils | GMP compliance, electropolished surfaces, zero dead-leg design |
| Power Generation | Heat recovery steam generators (HRSG), boiler economizer coils | High-temperature creep resistance, thermal cycling durability |
| Automotive | Heat exchanger cores, EV battery thermal management coils | Lightweight, compact coil geometry, vibration resistance |
| Oil & Gas | Subsea heat exchangers, gas processing coils | NACE MR0175 compliance, resistance to sour gas (H₂S) environments |
4.2 Gas Cooler Cleaning Technology — Operational Insight
Based on documented technical knowledge regarding coil-type gas cooler cleaning technology (盘管式燃气冷却器清洗工艺), the following operational considerations are integral to product design and specification:
Cleanability is a design parameter. Coil tubes deployed in gas coolers must accommodate periodic cleaning to remove scale, fouling, and chemical deposits. Key design considerations include:
- Smooth Internal Surface: Internal surface roughness should be maintained at Ra ≤ 0.8 μm to minimize fouling accumulation and facilitate chemical or mechanical cleaning.
- Access for Cleaning Media: Coil geometry must permit the passage of cleaning agents (acid solutions, chelating inhibitors, or mechanical brushes) without trapping residues in dead zones.
- Material Compatibility with Cleaning Agents: The stainless steel grade must withstand repeated exposure to cleaning chemicals (e.g., citric acid, hydrofluoric acid solutions, alkaline cleaners) without degradation of the passive film.
- Post-Cleaning Passivation: After aggressive cleaning, the tube surface should be readily re-passivated to restore corrosion resistance.
- Thermal Cycling Durability: Repeated heating and cooling cycles during gas cooler operation must not induce stress-corrosion cracking (SCC) or intergranular attack, particularly at weld joints.
Quality Certifications & Testing
5.1 Applicable Standards
- ASTM A554 — Standard Specification for Stainless Steel Tubing, Seamless, Austenitic, for General Applications
- ASTM A778 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Services
- ASTM A473 — Standard Specification for Heat Treatment of Stainless Steels
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes
- EN 10217-7 — European Standard for Non-Al