Stainless Steel Coil Tube with 100% Online Eddy Current Inspection
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 90) manufactures high-precision stainless steel coil tubes (coiltubes) designed for demanding industrial applications requiring superior dimensional accuracy, surface integrity, and material homogeneity. What distinguishes this product line is the company's commitment to uncompromised quality assurance through a fully automated, 100% online non-destructive testing (NDT) regime employing advanced through-type coil eddy current technology.
Every length of coil tube produced passes through a state-of-the-art through-type eddy current (ET) inspection system operating at speeds up to 60 m/min, ensuring that no defective material reaches the customer. This comprehensive quality control approach provides absolute traceability and confidence in the integrity of every coil tube delivered.
Material & Properties
Stainless steel coil tubes are fabricated from a range of austenitic, duplex, and ferritic stainless steel grades, with 304, 304L, 316, 316L, 321, and 310S being the most commonly specified. The material exhibits the following key properties:
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and aqueous environments due to the passive chromium oxide film layer (minimum 10.5% Cr content for austenitic grades).
- Mechanical Strength: Tensile strength ranging from 515 MPa (74,700 psi) to 760 MPa (110,200 psi) depending on grade and temper condition.
- Thermal Stability: Maintains structural integrity at elevated temperatures up to 870°C (1,598°F) for standard austenitic grades.
- Hygienic Surface: Achievable surface finish as low as Ra 0.4 μm (Ra 0.016 in) for sanitary and pharmaceutical applications.
- Formability: Superior cold-workability allowing bending, flaring, and crimping without cracking.
Specifications
| Parameter | Specification |
|---|---|
| Product Type | Stainless Steel Coil Tube (Continuous Length) |
| Product Code | 90 |
| Outer Diameter (OD) | 3.0 mm – 100.0 mm (0.118 in – 3.937 in) |
| Wall Thickness | 0.3 mm – 6.0 mm (0.012 in – 0.236 in) |
| OD Tolerance | ±0.05 mm (±0.002 in) standard; ±0.02 mm (±0.0008 in) precision |
| Wall Thickness Tolerance | ±0.03 mm (±0.0012 in) standard; ±0.01 mm (±0.0004 in) precision |
| Material Grades | 304, 304L, 316, 316L, 321, 310S, 321H, 904L, 2205 (duplex) |
| Surface Finish | Mill finish, 2B, No. 4 brushed, BA, mirror (Ra 0.2 μm) |
| Coil Length | 50 m – 2,000 m (164 ft – 6,562 ft) per coil |
| Coil Inner Diameter | 300 mm – 800 mm (11.8 in – 31.5 in) |
| Applicable Standards | ASTM A269, ASTM A213, EN 10216-5, GB/T 14976, JIS G3459 |
| Heat Treatment | Solution annealed (1050°C – 1150°C / 1,922°F – 2,092°F), pickled & passivated |
Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a rigorous multi-stage manufacturing process:
- Raw Material Selection: Only certified stainless steel strip or seamless tube blanks from approved mills are used, with full chemical composition verification prior to processing.
- Forming / Cold Drawing: High-precision forming or cold drawing equipment shapes the tube to exact dimensional specifications with minimal work hardening.
- Heat Treatment: Tubes are solution annealed in continuous or batch furnaces at controlled temperatures (1050°C – 1150°C) followed by rapid cooling to restore full austenitic structure and mechanical properties.
- Pickling & Passivation: Chemical pickling removes oxide scale; passivation treatment establishes a protective chromium oxide film for maximum corrosion resistance.
- Dimensional Calibration: Precision sizing and straightening to achieve tight OD and wall thickness tolerances.
- 100% Online Eddy Current Testing (ET): All coil tubes pass through a through-type coil eddy current inspection system at speeds up to 60 m/min. This critical quality gate detects surface and near-surface defects including cracks, laps (folds), and inclusions with zero escape rate.
- Coiling & Packaging: Qualified tubes are coiled to specified lengths, protected against mechanical damage and corrosion, and packaged for shipment.
Quality Certifications & NDT Capabilities
100% Online Eddy Current Testing (Through-Type Coil)
The hallmark of Wenzhou Jixing's quality assurance program is the deployment of a through-type coil eddy current (ET) inspection system integrated directly into the production line. This system operates at 100% coverage with throughput speeds reaching 60 m/min, ensuring that every single meter of coil tube is inspected without exception.
The through-type coil ET system is specifically capable of detecting:
- Surface Cracks: Longitudinal and circumferential surface-breaking cracks caused by tool wear, material defects, or processing damage.
- Near-Surface Cracks: Sub-surface discontinuities within the coil's detection depth, which could propagate under service stress.
- Laps (Folds): Material folding defects originating from upstream forming or rolling processes.
- Inclusions: Non-metallic inclusions (slag, oxide, or manganese sulfide) that compromise fatigue life and corrosion resistance.
Certifications
- ISO 9001:2015 Quality Management System
- ISO 14001:2015 Environmental Management System
- EN 10204 3.1 / 3.2 Material Test Certification
- ASME "S" Stamp (where applicable)
- CE Marking / PED 2014/68/EU compliance
- Nadcap NDT Level II & III personnel certification
Applications
The combination of precise dimensional control, superior surface quality, and guaranteed defect-free material makes these stainless steel coil tubes suitable for the following demanding applications:
- Heat Exchangers & Condensers: Precision OD and wall thickness tolerances ensure optimal thermal transfer and leak-free assembly in shell-and-tube, plate, and air-cooled heat exchangers.
- Food & Beverage Processing: Hygienic surface finishes and verified material purity meet FDA, 3-A Sanitary, and EHEDG requirements for dairy, brewing, and pharmaceutical processing equipment.
- Chemical & Petrochemical Industry: 316L and 904L grades resist aggressive chemical environments in reactors, distillation columns, and piping systems.
- Medical Devices & Instruments: Ultra-clean surface finish and traceable material documentation support medical device manufacturing to ISO 13485 standards.
- Aerospace Components: High-purity, defect-free tubing for hydraulic lines, fuel systems, and structural components.
- Automotive Exhaust Systems: 321 and 310S grades withstand high-temperature exhaust gas environments.
- Hydrogen & Energy Systems: Emerging applications in hydrogen fuel cell manifolds and electrolyzer components.
Unique Selling Points
- Zero-Defect Guarantee: 100% online eddy current inspection with through-type coils ensures no defective material escapes to the customer — a competitive advantage over suppliers relying on sampling inspection.
- High-Throughput Inspection: Inspection speed of up to 60 m/min enables large-volume production without compromising quality assurance, reducing lead times and maintaining cost competitiveness.
- Comprehensive Defect Detection: The ET system simultaneously identifies cracks, laps, and inclusions — three distinct defect categories that require different inspection approaches in less advanced facilities.
- Full Traceability: Every coil is traceable to its raw material heat number, processing parameters, and NDT results, supporting rigorous quality documentation requirements.
- Multi-Grade Capability: Ability to produce across a wide range of stainless steel grades from standard austenitic to high-alloy and duplex grades from a single production platform.
- Custom Specifications: Flexibility to accommodate special OD, wall thickness, surface finish, and coil length requirements tailored to specific customer engineering drawings.