Stainless Steel Coil Tube — Helium Mass Spectrometry & Bubble Leak Detection Specification
Product Overview
The stainless steel coil tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for critical applications in high-purity piping systems, vacuum engineering, and process instrumentation. As a coiled configuration of seamless stainless steel tubing, this product maintains dimensional integrity and mechanical stability while facilitating installation in confined or complex geometries.
The defining quality assurance protocol for this product line is the application of Helium Mass Spectrometry (Helium Leak Detection) and the Bubble Test Method — two industry-recognized techniques for identifying micro-leaks at sensitivities as low as 10⁻⁹ mbar·L/s. These methods serve as the primary verification means for periodic integrity validation of high-purity piping and vacuum systems, ensuring that every coil tube meets the stringent leak-tightness requirements of its intended service environment.
Material & Properties
Base Material
The coil tube is fabricated from high-grade austenitic stainless steel, typically conforming to the following material specifications:
- Grade 304 (UNS S30400 / 1.4301) — General-purpose applications requiring corrosion resistance and moderate mechanical strength
- Grade 316 (UNS S31600 / 1.4401) — Enhanced resistance to pitting and crevice corrosion due to molybdenum (Mo) alloying addition
- Grade 316L (UNS S31603 / 1.4404) — Low-carbon variant for superior weldability and resistance to sensitization in high-purity service
- Grade 304L (UNS S30403 / 1.4307) — Low-carbon variant for critical hygienic and pharmaceutical applications
Key Material Properties
- Surface Finish: Electropolished or passivated interior surface with Ra ≤ 0.4 μm for high-purity applications; mechanical polishing available for general service
- Chemical Composition: Conforms to ASTM A269 / A270, EN 10216-5, and ISO 3506 standards
- Mechanical Properties: Tensile strength ≥ 520 MPa (304), ≥ 570 MPa (316); elongation ≥ 40%
- Leak Tightness: Verified to detect leaks at 10⁻⁹ mbar·L/s via helium mass spectrometry
- Operating Temperature Range: −196 °C to +650 °C (depending on grade)
- Maximum Working Pressure: Up to 40 MPa (subject to wall thickness and diameter)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) — Item No. 226 | Wenzhou Jixing Metal Materials Co., Ltd. |
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A269 / EN 10216-5 |
| Wall Thickness | 0.3 mm – 3.0 mm | Per customer specification |
| Coil Inner Diameter | 200 mm – 600 mm | Custom configuration available |
| Coil Length | 5 m – 500 m (per coil) | Continuous coil supply |
| Surface Roughness (Interior) | Ra ≤ 0.4 μm (electropolished); Ra ≤ 0.8 μm (mechanically polished) | ASTM A270 |
| Leak Detection Sensitivity | 10⁻⁹ mbar·L/s (helium mass spectrometry) | ISO 10059 / EN 1779 |
| Leak Detection Method | Helium Mass Spectrometry; Bubble Test (soap solution) | ISO 10059; ASTM F2929 |
| Heat Treatment | Solution annealed and pickled; passivated (citric acid or nitric acid) | ASTM A270 |
| End Condition | Plain cut, beveled, or threaded per specification | Per customer drawing |
| Packaging | Vacuum-sealed in PE film, wooden crate with desiccant | ISO 11607 (for medical/purity applications) |
| Applicable Standards | ASTM A269, A270; EN 10216-5; ISO 3506; GB/T 14976 | Multi-standard compliance |
Manufacturing Process
1. Raw Material Selection and Incoming Inspection
Only certified stainless steel rounds or slabs from approved suppliers are accepted. Incoming materials undergo spectroscopic analysis (OES/PES) to verify chemical composition, along with mechanical property testing and ultrasonic flaw detection (UT) to ensure freedom from internal defects.
2. Piercing and Hot Rolling
The selected billet is pierced on a mandrel piercing mill and subsequently hot-rolled to the desired outer diameter and wall thickness. Hot rolling establishes the initial geometry and ensures uniform grain structure throughout the tube cross-section.
3. Cold Drawing / Cold Pilgering
The hot-rolled tube is cold-drawn through precision-die tooling to achieve the final dimensional tolerances (typically ±0.05 mm for OD and ±0.05 mm for wall thickness). Cold working enhances mechanical properties and surface finish while providing superior dimensional accuracy.
4. Intermediate Annealing
Periodic solution annealing (at 1050–1150 °C in inert atmosphere or vacuum) is performed during multi-pass cold drawing to relieve accumulated cold work and restore ductility. This ensures the tube can be coiled without risk of cracking or deformation.
5. Surface Treatment
- Pickling: Removal of scale and oxide films using mixed acid baths (HNO₃/HF or HNO₃/H₂SO₄)
- Passivation: Chemical treatment with citric acid or nitric acid to establish a stable, protective chromium oxide passive layer
- Electropolishing: (Optional) Electrochemical removal of surface contamination and micro-roughness to achieve Ra ≤ 0.4 μm
6. Coiling
The finished tube is coiled onto a precision mandrel or coil former to achieve the specified coil inner diameter. Coiling is performed under controlled tension to prevent ovality, kinking, or surface marring. Each coil is labeled and traceable to its heat number and manufacturing batch.
7. Leak Detection — Helium Mass Spectrometry and Bubble Testing
This is the critical quality verification step that defines the product's suitability for high-purity and vacuum applications.
7.1 Helium Mass Spectrometry (Helium Leak Testing)
Principle: A helium mass spectrometer detects helium atoms (He-4) that escape from the test article through microscopic leaks. Helium is used as the tracer gas due to its small atomic radius, non-reactivity, and low natural background concentration (5.24 ppm in atmosphere).
The coil tube (or discrete sections) is pressurized internally with helium gas. The external surface is then scanned with a calibrated helium mass spectrometer probe. Any leak path, however minute, will permit helium to escape, which is detected and quantified by the spectrometer. The system achieves a detection sensitivity of 10⁻⁹ mbar·L/s, enabling identification of leaks as small as 10⁻⁹ cubic centimeters per second.
7.2 Bubble Test Method
Principle: A soap-solution (surfactant-based) bath is applied to the external surface of the pressurized tube. Air or helium escaping through a leak forms visible bubbles, providing a visual indication of the leak location.
The bubble test serves as a complementary, field-deployable method for rapid leak localization. While its sensitivity is lower than helium mass spectrometry (typically 10⁻⁵ to 10⁻⁶ mbar·L/s), it provides immediate visual confirmation and precise spatial identification of leak sites.
8. Final Inspection and Certification
Each coil tube undergoes final dimensional verification (OD, wall thickness, straightness), surface finish measurement, and chemical composition confirmation. A comprehensive test certificate (EN 10204 Type 3.1) is issued, documenting all test results including helium leak test data.
Applications
The stainless steel coil tube with verified helium leak tightness is specified for the following critical applications:
- High-Purity Gas Piping Systems: Semiconductor manufacturing (photolithography, etching, CVD), where ultra-high purity (UHP) gas delivery requires leak-tight, low-outgassing pathways
- Vacuum Systems: Industrial and research vacuum chambers, molecular beam epitaxy (MBE) systems, and particle accelerator components requiring base pressures below 10⁻⁶ mbar
- Pharmaceutical and Bioprocessing: Cleanroom piping, sterile gas transfer, and bioreactor connections where cross-contamination must be eliminated
- Food and Beverage Industry: Hygienic process piping for CIP (Clean-in-Place) systems requiring leak-free, corrosion-resistant connections
- Cryogenic Systems: Liquefied natural gas (LNG), liquid helium (LHe), and liquid nitrogen (LN₂) transfer lines operating at extreme sub-zero temperatures
- Oil and Gas / Petrochemical: Downstream processing, hydrogen purification, and noble gas recovery systems
- Power Generation: Nuclear reactor coolant loops, steam generator tubes, and turbine instrumentation lines
- Aerospace: Fuel system tubing, hydraulic lines, and environmental control system (ECS) components
Quality Certifications and Compliance
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Full manufacturing process |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health and Safety Management |
| EN 10204 Type 3.1 | Inspection Certificate — Individual test results per batch |
| ISO 10059 / EN 1779 | Helium leak detection — Methodology and equipment calibration |
| ASTM F2929 | Standard Practice for Leak Detection — Bubble testing |
| ASME BPE | Bioprocessing Equipment — For pharmaceutical-grade coil tubes |
| 3-A Sanitary Standards | Dairy and food processing — Hygienic design and surface finish |
| PED 2014/68/EU | Pressure Equipment Directive — For pressure-containing applications |
| CE / PED Marking | European conformity for pressure equipment |
Unique Selling Points
- Verified Leak Tightness at 10⁻⁹ mbar·L/s: Every coil tube is certified through helium mass spectrometry, providing quantifiable, traceable proof of leak-tightness — a critical differentiator for semiconductor and vacuum applications
- Dual Verification Protocol: Combination of helium mass spectrometry (quantitative, laboratory-grade) and bubble testing (qualitative, field-deployable) ensures comprehensive leak detection coverage
- Full Traceability: Each coil is traceable from raw material heat number through manufacturing, testing, and final certification, supporting regulatory compliance in regulated industries
- Multi-Grade Availability: Selection from 304, 304L, 316, and 316L grades accommodates diverse chemical and mechanical requirements
- Precision Coiling: Controlled coiling process ensures zero ovality, zero kinks, and surface integrity preservation — critical for downstream forming and welding operations
- Electropolished Surface Option: Ra ≤ 0.4 μm interior finish minimizes particle adhesion and enables effective CIP/CIP-S (Clean-in-Place / Clean-in-Place Sterilization)
Periodic Verification Recommendations
For installations utilizing this coil tube in high-purity or vacuum service, the following periodic verification schedule is recommended:
| System Category | Recommended Verification Interval | Method |
|---|---|---|
| Semiconductor UHP gas lines | Every 6 months | Helium mass spectrometry |
| Vacuum chamber systems (≤ 10⁻⁶ mbar) |