Stainless Steel Coil Tube — X-Ray / Gamma-Ray Radiographic Testing (RT) Specification

1. Product Overview

Wenzhou Jixing Metal Materials Co., Ltd (JXMM) manufactures high-grade stainless steel coil tubes (盘管, Coil Tube) engineered for demanding industrial applications. As part of the company's rigorous quality assurance framework, every coil tube production lot undergoes comprehensive Non-Destructive Testing (NDT), with particular emphasis on Radiographic Testing (RT) utilizing X-ray and Gamma-ray imaging techniques. This specification documents the radiographic examination protocol employed to ensure weld integrity, volumetric defect detection, and compliance with international quality standards.

The Radiographic Testing method applied by JXMM employs both conventional film-based imaging and modern digital radiographic imaging (Computed Radiography — CR, and Digital Radiography — DR) to achieve superior defect identification rates. RT is designated as the definitive arbitration method for weld quality assessment, providing irrefutable evidence of internal structural integrity in seamless and welded coil tube assemblies.

2. Material & Properties

2.1 Base Material Composition

• Grade: 304, 304L, 316, 316L, 321, 310S, 904L, and custom austenitic/ferritic stainless steel grades
• Material Form: Cold-rolled stainless steel coil, slit and formed into precision tube profiles
• Surface Finish: 2B, BA (Bright Annealed), No. 4, No. 8 mirror polish, or custom finishes
• Chemical Compliance: ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771

2.2 Radiographic Sensitivity Requirements

• Volumetric Defect Detection: Porosity (气孔), slag inclusions (夹渣), cavities, and internal voids
• Minimum Detectable Defect Size: ≥ 0.5 mm equivalent diameter at 2T image quality
• Image Quality Indicator (IQI): Type A wire IQI per ASME Section V / EN ISO 17636-1
• Minimum IQI Readability: 2T (two-digit) on both film and digital receptors

3. Specifications

Parameter	Specification / Requirement	Standard Reference
Testing Method	X-ray Radiographic Testing (XRT) and Gamma-ray Radiographic Testing (γRT)	ASME BPV Section V, Article 2; EN ISO 17636-1; GB/T 3323
Imaging Technique	Single-wall (SWS) and Double-wall Single-image (DWSI)	ASME Section V T-276; EN ISO 17636-2
X-Ray Source	Tube voltage 60–450 kV, adjustable focal spot (0.4–2.0 mm)	IEC 60336; GB/T 16507
Gamma-Ray Source	Iridium-192 (Ir-192), Cobalt-60 (Co-60), or Thulium-170 (Tm-170)	ISO 9934-1; GB/T 12604
Image Receptor (Film)	Industrial radiographic film, medium-speed (Type M) or fine-grain (Type F)	ASTM E938; EN ISO 5817
Image Receptor (Digital)	Computed Radiography (CR) phosphor plates or Digital Radiography (DR) flat-panel detectors	ISO 11699; ASTM E2745
Source-to-Object Distance (SOD)	≥ 500 mm (minimum); magnification ratio ≥ 1.05	ASME Section V T-276
Penetration Time	Adjusted per material thickness; minimum 2T IQI density range 1.0–4.0 (film)	EN ISO 17636-1
Acceptance Criteria	ASME BPV Section VIII Div. 1 UW-51(b); EN ISO 5817 Level B; GB/T 11345	See above
Defect Classification	Volumetric: Porosity, slag, cavity; Planar: Cracks, laminations (supplementary)	ASME Section V; ISO 10675-1
Reporting	Detailed RT report with film/digital image archiving, defect mapping, and pass/fail determination	ISO 17636-7

4. Manufacturing Process & RT Integration

4.1 Coil Tube Production Workflow

1. Coil Slitting & Edge Preparation: Stainless steel coil is slit to precise width and edges are trimmed for uniform welding.
2. Forming & Welding: Slit coil is formed into tube profiles via roll-forming or hydraulic bending; longitudinal welds are produced by TIG (GTAW) or laser welding.
3. Heat Treatment: Solution annealing and pickling passivation to restore corrosion resistance and relieve residual stresses.
4. Dimensional Inspection: OD, wall thickness, roundness, and straightness verification.
5. Non-Destructive Testing (NDT): Multi-modal NDT including visual testing (VT), dye penetrant testing (PT), magnetic particle testing (MT), and Radiographic Testing (RT).
6. Final Verification & Packaging: Pressure testing, surface finish verification, and protective packaging for shipment.

4.2 Radiographic Testing Execution

1. Weld Identification & Marking: Each weld zone is uniquely marked and catalogued for traceability.
2. Source Positioning: X-ray or Gamma-ray source is positioned at the geometric center of the weld, perpendicular to the weld axis.
3. Image Receptor Placement: Film packets or digital detectors are placed on the opposite side of the weld from the source.
4. Exposure & Acquisition: Radiographic exposure is performed; exposure parameters (kV, mA, time, SOD) are recorded.
5. Image Processing: Film is developed, fixed, and dried; digital images undergo histogram equalization and contrast enhancement.
6. Image Evaluation: Certified NDT Level III inspectors evaluate images for volumetric defects against acceptance criteria.
7. Reporting & Archiving: Results are documented in a formal RT report; images are archived for minimum 10-year traceability.

4.3 Unique Selling Points of JXMM Radiographic Testing

• Superior Volumetric Defect Detection: X-ray and Gamma-ray RT achieves the highest detection sensitivity for volumetric defects including porosity (气孔), slag inclusions (夹渣), internal cavities, and shrinkage voids — defects that are invisible to surface NDT methods such as PT or MT.
• Arbitration-Grade Quality Assurance: RT is recognized internationally as the definitive arbitration method for weld quality disputes. JXMM's RT protocol provides legally defensible, permanent image records that resolve any quality disagreements between parties.
• Dual-Modality Approach: JXMM deploys both X-ray (high resolution, ideal for thin-wall tubes) and Gamma-ray (portable, ideal for thick-wall and field applications) sources, ensuring comprehensive coverage across the full product range.
• Digital Imaging Integration: Computed Radiography (CR) and Digital Radiography (DR) technologies enable rapid image acquisition, real-time defect analysis, and digital archiving — significantly enhancing traceability and customer communication.
• Certified Inspection Personnel: All RT operations are conducted by personnel certified to Level III per ASNT SNT-TC-1A / ISO 9712, ensuring consistency, accuracy, and regulatory compliance.

5. Applications

The combination of premium stainless steel coil tube materials and rigorous RT quality assurance makes JXMM products suitable for the following critical applications:

• Petroleum & Natural Gas Industry: Downhole tubing, wellhead components, and subsea pipeline connections where volumetric weld integrity is paramount.
• Chemical & Pharmaceutical Processing: Reactor vessels, heat exchanger tubes, and sanitary process piping requiring zero-defect weld quality.
• Power Generation: Boiler tubes, superheater elements, and nuclear-grade piping assemblies subject to ASME and NQA-1 standards.
• Food & Beverage Processing: Hygienic coil tubing for dairy, brewing, and beverage production lines requiring BA or mirror finishes.
• Automotive & Aerospace: Exhaust systems, fuel delivery lines, and structural tubing where weld integrity directly impacts safety.
• Marine & Offshore: Ballast water systems, seawater cooling circuits, and corrosion-resistant structural tubing.
• Medical Equipment: Surgical instrument tubing, MRI scanner components, and pharmaceutical-grade fluid handling systems.

6. Quality Certifications & Compliance

6.1 System Certifications

• ISO 9001:2015 — Quality Management System
• ISO 3834-2 — Requirements for Quality Assurance for Fusion Welding of Metallic Materials
• EN 10204 — Type 3.1 Inspection Certificates (Material Test Reports with test results from an independent body)
• ASME "Q" Stamp — Quality System for Pressure Vessel Fabrication (where applicable)
• API Q1 — Quality Management Systems for Petroleum, Petrochemical, and Natural Gas Industries (where applicable)

6.2 NDT Personnel & Equipment Certifications

• ASNT SNT-TC-1A — NDT personnel certification (Level II and Level III)
• ISO 9712 — International NDT personnel certification standard
• PCN (British) / IASND — NDT technician and examiner accreditation (where applicable)
• NDT Equipment Calibration: X-ray generators calibrated per IEC 61217-1; Gamma-ray sources with verified activity per ISO 9934-1; IQIs verified per ISO 19232-1

6.3 Material & Product Standards Compliance

• ASTM A213 / A269 — Seamless and welded austenitic stainless steel tube for heat exchangers and high-temperature service
• ASME SA-213 / SA-269 — Boiler and pressure vessel code quality tube
• EN 10216-5 — Non-ferrous metallic seamless tubes for technical uses
• GB/T 12771 — Chinese national standard for welded stainless steel tubes
• GB/T 14976 — Chinese national standard for seamless stainless steel tubes
• ASTM E94 / E1010 / E2745 — Radiographic testing standards for film and digital imaging

6.4 Third-Party Verification

JXMM welcomes and supports third-party inspection (TPI) by recognized agencies including SGS, Bureau Veritas, DNV, Lloyd's Register, and TUV. All RT reports are available for independent review and can be supplemented with on-site witness inspections upon customer request.

Important Note: While Radiographic Testing is recognized as the most effective method for detecting volumetric defects and serves as the definitive arbitration method for weld quality, it is acknowledged that RT carries higher operational costs and slower inspection throughput compared to alternative NDT methods such as Ultrasonic Testing (UT) or Eddy Current Testing (ET). JXMM strategically deploys RT for critical weld zones, high-value product lots, and arbitration scenarios where maximum detection confidence is required, while utilizing faster NDT methods for routine screening. This balanced approach optimizes quality assurance while maintaining competitive lead times and cost efficiency.