Stainless Steel Coil Tube — TOFD/Phased Array Ultrasonic Testing Specification
Product Overview
The stainless steel coil tube (盘管 Coiltube) produced by Wenzhou Jixing Metal Materials Co., Ltd. is a high-precision rolled stainless steel tubing product designed for demanding industrial applications. This specification document focuses on the advanced non-destructive testing (NDT) methodology employed to ensure product integrity — specifically Time of Flight Diffraction (TOFD) and Phased Array Ultrasonic Testing (PAUT). These digital imaging techniques represent the cutting edge of ultrasonic flaw detection (UT), offering superior defect quantification accuracy compared to conventional methods.
As the industry transitions toward more sophisticated inspection protocols, TOFD and Phased Array technologies are increasingly replacing traditional radiographic testing (RT) in high-end projects, driven by their ability to provide real-time, quantitative defect characterization without the hazards and limitations associated with ionizing radiation.
Material & Properties
Base Material Grades
- Austenitic Stainless Steel: 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 347 (UNS S34700)
- Super Austenitic: 904L (UNS N08904), 2205 Duplex (UNS S32205), 2507 Super Duplex (UNS S32750)
- High-Temperature Alloys: 310S (UNS S31008), Inconel 625 (UNS N06625)
Key Physical Properties
- Acoustic impedance optimized for ultrasonic wave propagation in austenitic grain structures
- Low magnetic permeability enabling reliable electromagnetic auxiliary couplants
- High corrosion resistance ensuring long-term service integrity in aggressive environments
- Thermal conductivity suitable for consistent coupling during inspection cycles
Specifications
| Parameter | Specification / Value | Standard Reference |
|---|---|---|
| Product Category | Stainless Steel Coil Tube (盘管) | — |
| Outer Diameter (OD) | 6.0 mm – 219.1 mm | ASTM A511 / ASME B36.19M |
| Wall Thickness | 0.5 mm – 12.7 mm | ASTM A511 |
| Coil Length | Up to 120 m per coil | Manufacturer Specification |
| Surface Finish | 2B / BA / Pickled & Passivated / Custom | ASTM A478 |
| Weld Type | Continuous Welded (PWHT optional) | ASTM A511 |
| NDT Method | TOFD / Phased Array Ultrasonic Testing | EN ISO 22810 / EN ISO 13588 |
| Defect Detection Sensitivity | ≥ 0.5 mm crack length (TOFD); ≥ 0.2 mm resolution (PAUT) | ASME BPVC Section V, Article 4 |
| Inspection Coverage | 100% volumetric examination of weld seam | Client / Project Specification |
| Acceptance Criteria | ASME Section V / EN 14305 / Client-specific | Per project requirement |
Manufacturing Process
Production Workflow
- Raw Material Verification: Incoming stainless steel strip undergoes chemical composition analysis (OES/SEM) and mechanical property testing to confirm compliance with specified grade requirements.
- Forming & Welding: Precision roll-forming machines shape the strip into a tubular configuration. A high-energy TIG (Tungsten Inert Gas) or laser welding process creates a continuous longitudinal seam with minimal heat-affected zone (HAZ).
- Post-Weld Heat Treatment (PWHT): Where required, the welded coil tube is solution-annealed at 1040–1120 °C followed by rapid quenching to restore full austenitic microstructure and relieve residual stresses.
- Coiling: The finished tube is wound onto precision mandrels to maintain dimensional accuracy and prevent mechanical deformation.
- NDT Inspection — TOFD/Phased Array: See detailed inspection protocol below.
- Final Dimensional Verification: Laser-based OD and wall thickness gauging systems confirm conformance to tolerance limits.
- Packaging & Dispatch: Coils are protected with moisture barriers, wooden crating, or export-grade steel banding.
TOFD/Phased Array Inspection Protocol
- Probe Configuration:
- TOFD: Dual-element transducer array with separately angled transmitter and receiver (typically 45°–70° refracted angle), providing diffraction-based crack sizing.
- Phased Array (PAUT): Multi-element linear or matrix array (e.g., 64-element or 128-element probe) with electronic beam steering and focusing for full beam-scan coverage.
- Couplant Application: Water-based or oil-based couplant ensures optimal acoustic impedance matching between transducer and stainless steel surface.
- Data Acquisition: High-resolution digital signal processing captures A-scan, B-scan, C-scan, and S-scan representations of the weld volume in real time.
- Defect Characterization: Digital imaging algorithms quantify defect dimensions (length, height, width), orientation, and volumetric position with sub-millimeter accuracy.
- Reporting: Full digital records are archived with automated pass/fail determination against project-specific acceptance criteria.
Applications
The stainless steel coil tube with TOFD/Phased Array verified integrity is deployed across a broad spectrum of high-integrity industries:
- Oil & Gas: Subsea pipelines, offshore platforms, refineries, and LNG processing facilities
- Power Generation: Nuclear reactor coolant loops, steam generators, supercritical boilers
- Chemical & Petrochemical: Reactor vessels, heat exchangers, corrosion-resistant piping systems
- Food & Pharmaceutical: Hygienic process piping, CIP (Clean-in-Place) systems
- Aerospace: Hydraulic lines, fuel system tubing, structural components
- Marine & Shipbuilding: Ballast systems, seawater piping, desalination plants
- Medical Devices: Surgical instrument tubing, implant manufacturing feedstock
Quality Certifications & Standards Compliance
Company Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management
- NADCAP — Special Processes (where applicable for aerospace customers)
- EN 10204 3.1 — Material Test Certificate compliance
NDT Personnel & Equipment Certification
- All TOFD/Phased Array operators certified to SNT-TC-1A Level III or EN ISO 9712 Level II/III
- Inspection equipment calibrated per ASME Section V, Article 4 requirements
- Daily reference block verification using calibrated notched specimens (e.g., SFL, HCF, V1 blocks)
- Traceable calibration records maintained for audit purposes
Governing Standards
- EN ISO 22810:2018 — Ultrasonic testing — TOFD techniques
- EN ISO 13588:2016 — Ultrasonic testing — Phased array methods
- ASME BPVC Section V, Article 4 — Nondestructive Examination
- API 1104 / API 1105 — Welding of Pipelines and Related Facilities
- EN 14305 — Steel piping systems — Testing requirements
Unique Selling Points
Digital Imaging Superiority: TOFD and Phased Array technologies deliver quantitative, three-dimensional defect characterization that surpasses the binary pass/fail limitations of conventional radiographic testing. Defect size accuracy is improved by up to 40% compared to manual RT interpretation.
Regulatory Advantage: As regulatory bodies worldwide phase out ionizing radiation exposure requirements, TOFD/PAUT offers a radiation-free, operator-safe alternative that aligns with modern occupational health mandates.
Real-Time Decision Making: Digital beam-scan imaging enables immediate on-line inspection decisions, reducing production bottlenecks and enabling just-in-time manufacturing workflows.
Full Data Traceability: Complete digital records of every inspection are archived, providing unparalleled documentation for regulatory audits, lifecycle management, and forensic analysis.
Wenzhou Jixing Metal Materials Co., Ltd. remains committed to advancing stainless steel coil tube quality through state-of-the-art non-destructive testing methodologies, ensuring every product meets the highest standards of dimensional accuracy, metallurgical integrity, and service reliability.