Stainless Steel Large-Diameter Flexible Coil Tube (Coil Tube)
Product Code: 258 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Large-Diameter Flexible Coil Tube is an advanced tubular product engineered for demanding industrial applications requiring both high pressure resistance and exceptional flexibility. This product represents the culmination of specialized research into assembly process methodologies for large-diameter flexible coil tubes, integrating state-of-the-art metallurgical practices with precision manufacturing techniques to deliver a superior coil tube solution.
Unlike conventional rigid piping systems, this coil tube product leverages its inherent helical geometry to provide outstanding flexibility, vibration damping, and thermal expansion accommodation, making it particularly suitable for complex routing configurations in high-temperature and high-pressure environments.
2. Material & Properties
2.1 Base Material Composition
The coil tube is fabricated from premium-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal stability. Commonly employed grades include:
- 304 / 304L (UNS S30400 / S30403) — General-purpose corrosion resistance
- 316 / 316L (UNS S31600 / S31603) — Enhanced chloride and acid resistance
- 321 (UNS S32100) — Stabilized for high-temperature applications
- 310S (UNS S31008) — Ultra-high-temperature service
2.2 Key Mechanical Properties
- Tensile Strength: ≥ 520 MPa (75 ksi) minimum
- Yield Strength: ≥ 205 MPa (30 ksi) minimum
- Elongation: ≥ 40% (measured at fracture)
- Hardness: ≤ 92 HRB (annealed condition)
- Operating Temperature Range: −196 °C to +1150 °C (depending on grade)
2.3 Physical & Corrosion Resistance Characteristics
- Excellent resistance to intergranular corrosion, pitting, and crevice corrosion
- Outstanding oxidation resistance at elevated temperatures
- Non-magnetic in annealed condition (304/316 grades)
- Low thermal conductivity relative to carbon steels
- High resistance to stress corrosion cracking in non-chloride environments
3. Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 19 mm – 273 mm (custom sizes available) | ASTM A213 / ASME SA-213 |
| Wall Thickness | 1.0 mm – 12.0 mm | ASTM A213 |
| Coil Diameter (Bundled) | 1.0 m – 6.0 m (large-diameter configurations) | Manufacturer specification |
| Coil Length (per bundle) | 50 m – 500 m (configurable) | Manufacturer specification |
| Surface Finish | Pickled & Passivated, or Mirror Polish (Ra ≤ 0.4 μm) | ASTM A479 |
| Pressure Rating | Up to 60 MPa (8,700 psi) at operating temperature | ASME B31.3 |
| Minimum Bend Radius | 3D (D = tube outer diameter) | ASME B31.3 |
| Heat Treatment | Solution Annealed (1050–1150 °C, water/quench cooled) | ASTM A213 |
| Forming Method | Hot-rolled (HR), Cold-drawn (CD), or Seamless (SM) | ASTM A269 / A213 |
| End Condition | Plain, Beveled, Threaded, or Flanged (as specified) | ASME B16.11 / B16.5 |
4. Manufacturing Process
4.1 Raw Material Preparation
Manufacturing commences with the selection of certified stainless steel seamless pipe or strip, subjected to rigorous incoming inspection including spectroscopic chemical analysis (OES), mechanical property verification, and dimensional accuracy checks. Only material meeting or exceeding ASTM/ASME standards proceeds to the production line.
4.2 Coil Forming & Large-Diameter Assembly Process
The core differentiator of this product lies in the proprietary large-diameter flexible coil tube assembly process, which involves the following critical stages:
- Tube Straightening: Incoming tube is mechanically straightened to achieve dimensional tolerance of ±0.05 mm/m straightness deviation.
- Coil Winding: The tube is wound onto a precision mandrel system to form the desired helical geometry. For large-diameter configurations, a multi-axis forming system ensures uniform curvature without introducing wall thinning or ovality exceeding 1% of nominal OD.
- Intermediate Annealing: Where required, stress-relief annealing is performed at 850–1050 °C followed by controlled cooling to eliminate residual stresses introduced during forming.
- Bundle Assembly: Multiple coil tubes are assembled into a bundled configuration using specialized spacing fixtures, ensuring uniform pitch and maintaining the structural integrity of each individual coil.
- Welding & Brazing: Header connections are fabricated using orbital GTAW (Gas Tungsten Arc Welding) or TIG welding with inert gas back-purging to ensure full penetration and corrosion-free weld zones.
- Surface Treatment: Final pickling and passivation are performed to remove oxidation scale and establish a protective chromium oxide film on the surface.
4.3 Quality Control Integration
In-process quality control is embedded at every critical stage:
- Visual Inspection (VI): 100% inspection of weld seams and surface finish
- Dimensional Inspection: CMM (Coordinate Measuring Machine) verification of OD, wall thickness, and coil geometry
- Non-Destructive Testing (NDT): Eddy Current Testing (ECT) and/or Ultrasonic Testing (UT) for internal and external defect detection
- Pressure Testing: Hydrostatic testing at 1.5× design pressure with 100% pass rate requirement
- Chemical Analysis: Spectrographic verification of material composition
5. Applications
The stainless steel large-diameter flexible coil tube finds extensive application across multiple high-value industries:
- Oil & Gas Industry: Subsea production risers, flexible flow lines, Christmas tree connections, and wellhead assemblies where flexibility and corrosion resistance are paramount.
- Chemical Processing: Heat exchanger coil bundles, reactor internals, and process piping handling aggressive chemical media.
- Power Generation: Steam generator tubes, condensers, and superheater assemblies in both fossil-fuel and nuclear power plants.
- Pharmaceutical & Food Processing: Hygienic process piping requiring high surface finish and corrosion resistance under CIP (Clean-in-Place) conditions.
- Marine & Offshore: Ballast water systems, seawater cooling circuits, and subsea umbilical systems.
- HVAC & Refrigeration: Large-diameter coil assemblies for industrial chillers and heat recovery systems.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- ASME "U" Stamp — Pressure Vessel Manufacturing Authorization
- NACE MR0175 / ISO 15156 — Compliance for oil & gas sour service
- EN 10204 3.1 / 3.2 — Material Testing Certificates
- ASTM / ASME / EN / JIS — Product conformity to applicable standards
- API Monogram License — Where applicable for oil & gas components
7. Unique Selling Points
Proprietary Large-Diameter Assembly Process: The company's specialized research and development in large-diameter flexible coil tube assembly methodology delivers superior geometric accuracy, enhanced fatigue life, and improved bundle uniformity compared to conventional manufacturing approaches.
- Customizable Geometry: Tailored coil diameters, pitches, and bundle configurations to meet specific project requirements.
- Full Traceability: Every coil tube bundle is accompanied by a complete material traceability record from raw material mill certificate through final inspection.
- Extended Service Life: Optimized heat treatment and surface passivation extend operational lifespan significantly in corrosive environments.
- Reduced Installation Complexity: Inherent flexibility minimizes the need for additional expansion joints and support structures, lowering overall system cost.
- Engineering Support: Dedicated technical team provides selection guidance, stress analysis, and installation recommendations for optimal system performance.
This product represents the integration of advanced materials science with specialized manufacturing expertise, delivering a reliable, high-performance solution for the most demanding industrial applications.