Stainless Steel Coil Tube (盘管) — Technical Specification & Engineering Reference
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube") is a continuous, helically wound tubular product manufactured from austenitic or duplex stainless steel grades, supplied in coil form to facilitate downstream forming, welding, and installation processes. Wenzhou Jixing Metal Materials Co., Ltd (温州吉兴金属材料有限公司) produces and supplies Coil Tubes engineered for critical service environments where corrosion resistance, mechanical integrity, and long-term reliability are paramount.
This specification document incorporates engineering insights derived from internal technical literature titled "Causes and Improvement of Internal Coil Tube Connection Leakage" (《内盘管接管泄漏成因及改进》), which provides a systematic analysis of leakage failure modes at coil tube joints and validated corrective measures. These lessons are integrated into the design, manufacturing, and quality assurance protocols described herein.
2. Material & Properties
2.1 Commonly Available Grades
- Austenitic Stainless Steel (奥氏体不锈钢): AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316L (UNS S31603), AISI 321 (UNS S32100)
- Duplex Stainless Steel (双相不锈钢): 2205 (UNS S32205), 2507 (UNS S32750)
- Super Austenitic (超级奥氏体): 904L (UNS N08904)
2.2 Mechanical Properties (Typical for Grade 316L)
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (75 ksi) | ASTM A269 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa (30 ksi) | ASTM A269 / GB/T 12771 |
| Elongation (延伸率) | ≥ 35% | ASTM A269 |
| Corrosion Resistance (耐蚀性) | Excellent in oxidizing and reducing environments | ASTM G48 / GB/T 4334 |
| Operating Temperature Range (使用温度范围) | −196 °C to +425 °C (−321 °F to +797 °F) | ASME BPVC Section IX |
| Surface Roughness (表面粗糙度) | ≤ Ra 0.8 μm (polished); ≤ Ra 3.2 μm (industrial) | GB/T 1031 |
3. Dimensions & Specifications
| Parameter | Range / Value | Standard |
|---|---|---|
| Outer Diameter (外径, OD) | 6.0 mm – 219.0 mm | ASTM A269 / GB/T 12771 |
| Wall Thickness (壁厚, WT) | 0.3 mm – 6.0 mm | ASTM A269 |
| Coil Inner Diameter (盘管内径) | 300 mm – 1,200 mm (adjustable per order) | Enterprise Standard (企业标准) |
| Coil Length (盘管长度) | 50 m – 1,000 m (continuous) | Enterprise Standard |
| Manufacturing Method (制造工艺) | Seamless (无缝) / Welded (焊接: ERW, TIG) | ASTM A269 / ASTM A554 |
| Tolerance (公差) | ±0.05 mm (OD); ±10% (WT) | GB/T 12771 |
| End Preparation (端部处理) | Plain, Beveled (坡口), Threaded (螺纹), Flanged (法兰) | ASME B16.9 / GB/T 12459 |
4. Manufacturing Process
4.1 Seamless Coil Tube Production (无缝盘管)
- Hot Rolling (热轧): Billet is heated to 1,150–1,250 °C and pierced to form hollow blanks.
- Cold Drawing (冷拔): Blanks are drawn through precision dies to achieve final OD and wall thickness tolerances.
- Heat Treatment (热处理): Solution annealing (固溶处理) at 1,050–1,150 °C followed by rapid quenching to restore full austenitic microstructure and corrosion resistance.
- Pickling & Passivation (酸洗钝化): Removal of mill scale and formation of protective chromium oxide film (Cr₂O₃).
- Coiling (盘绕): Continuous tube is wound onto precision mandrels under controlled tension to produce uniform coil geometry.
4.2 Welded Coil Tube Production (焊接盘管)
- Strip Slitting (分条): Cold-rolled stainless steel strip is slit to precise width.
- Forming & Welding (成型焊接): Strip is formed into tube geometry and welded via Electric Resistance Welding (ERW) or Tungsten Inert Gas (TIG) welding.
- Weld Heat-Affected Zone (HAZ) Treatment (焊缝热影响区处理): Localized annealing to eliminate sensitization (敏化) and restore intergranular corrosion resistance (晶间耐蚀性).
- Hydrostatic Testing (水压试验): Each coil undergoes hydrostatic pressure testing at 1.5× working pressure for a minimum dwell time of 30 seconds.
4.3 Critical Process Control — Connection Integrity (连接完整性控制)
Based on the technical study "Causes and Improvement of Internal Coil Tube Connection Leakage", the following root causes of leakage at coil tube joints have been identified and systematically addressed:
- Improper Fit-Up (组对不当): Mismatch in OD tolerance between tube end and fitting creates radial gaps exceeding 0.5 mm. Corrective measure: Mandatory laser gauge inspection of each tube end prior to assembly.
- Inadequate Weld Penetration (焊缝未熔透): Insufficient heat input results in lack of fusion (未熔合) at the root of butt welds. Corrective measure: Implementation of pre-weld groove verification and post-weld radiographic testing (RT) per ASME Section V, Article 2.
- Thermal Distortion (热变形): Localized heating during welding causes angular misalignment of the coil tube relative to the header. Corrective measure: Use of clamping fixtures with real-time angular measurement (±0.5° tolerance).
- Corrosion-Induced Degradation (腐蚀退化): Crevice corrosion (缝隙腐蚀) at gasket interfaces under prolonged service. Corrective measure: Specification of high-integrity gaskets (e.g., spiral wound with PTFE filler) and periodic NDT inspection intervals.
- Stress Corrosion Cracking (SCC, 应力腐蚀开裂): Residual welding stresses combined with chloride-containing environments. Corrective measure: Post-weld stress relief annealing (焊后去应力退火) at 300–350 °C for sensitized grades, and selection of super austenitic or duplex grades for high-chloride service.
5. Applications
- Petrochemical & Refinery (石油化工): Heat exchanger bundles, reactor internals, distillation column internals, process piping coils.
- Power Generation (发电): Boiler economizer coils, superheater tubes, steam turbine condenser tubes, nuclear-grade instrumentation tubing.
- Food & Pharmaceutical (食品医药): Sanitary process piping, CIP (Clean-in-Place) loop coils, fermentation vessel internals.
- Marine & Offshore (海洋工程): Ballast water system tubing, seawater cooling coils, offshore platform risers.
- Chemical Processing (化工): Acid storage tank internals, chemical transfer coil systems, evaporator and crystallizer coil assemblies.
- Oil & Gas (油气): Subsea production tubing, wellhead instrumentation coils, LNG (Liquefied Natural Gas) transfer lines.
6. Quality Certifications & Testing
6.1 Applicable Standards
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
- ASTM A554: Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing
- ASME BPVC Section IX: Welding, Brazing, and Fusing Qualifications
- GB/T 12771: Stainless Steel Seamless Tubes for General Purposes (中国国家标准)
- EN 10216-5: Technical Delivery Conditions for Seamless Steel Tubes — Austenitic and Austenitic-Ferritic Grades
- ISO 15530: Welded Steel Tubes for General Purposes
6.2 Incoming & In-Process Inspection (来料及过程检验)
| Test Method | Frequency | Acceptance Criteria |
|---|---|---|
| Spectrochemical Analysis (光谱分析) | Per heat lot (每炉批) | Composition within ASTM A269 Table 1 limits |
| Hydrostatic Test (水压试验) | 100% of coils | No leakage at 1.5× working pressure, 30 s dwell |
| Dimensional Inspection (尺寸检验) | Every 10 m of tube length | OD ±0.05 mm; WT ±10% |
| Radiographic Testing (RT, 射线检测) | Per ASME Section V, Article 2 (welded tubes) | No indications exceeding acceptance criteria |
| Intergranular Corrosion Test (晶间腐蚀试验) | Per ASTM A269 / ASTM G28 | No intergranular attack in 65% boiling HNO₃ (24 h) |
| Surface Defect Inspection (表面缺陷检验) | 100% visual + Eddy Current (涡流检测) | No cracks, laps, or surface imperfections |
6.3 Certifications & Traceability
- MTR (Mill Test Report, 材质证明书): Provided with every shipment, including chemical composition, mechanical properties, and test results.
- Heat Number Traceability (炉号追溯): Full traceability from raw material mill certificate through final product delivery.
- ISO 9001:2015 Quality Management System (质量管理体系认证): Certified manufacturing and quality assurance processes.
- NACE MR0175 / ISO 15156: Available for sour service (含硫环境) applications.
- PED 2014/68/EU Compliance (欧盟压力设备指令合规): Available for pressure equipment applications in European markets.
7. Unique Selling Points (独特卖点)
- Leakage-Prevention Engineering Heritage (防泄漏工程积淀): Decades of documented field experience in diagnosing and preventing coil tube connection failures, translating directly into superior product reliability.
- Full-Grade Material Flexibility (全牌号材料灵活性): Supply capability spanning standard austenitic, duplex, and super austenitic grades to match the most demanding service environments.
- Integrated Coil-to-Installation Support (盘管到安装一体化支持): Engineering assistance for coil springback calculation (回弹计算), installation fixture design, and field welding procedure qualification.
- Traceability & Documentation Rigor (追溯与文件严谨性): Complete MTR and test documentation packages meeting international regulatory requirements (ASME, PED, NACE).
- Customized Coil Geometry (定制化盘管几何): Tailored coil inner diameter, pitch, and end preparation to minimize handling damage and optimize installation efficiency.
8. Packaging & Shipping
- Each coil is wrapped in moisture-proof kraft paper and secured with steel strapping.
- Coils are loaded on wooden pallets or steel saddles for container or bulk vessel transport.
- Custom crating available for export shipments to prevent coil movement and surface damage during transit.
9. Technical Support & After-Sales
Wenzhou Jixing Metal Materials Co., Ltd provides comprehensive technical support including:
- Welding procedure qualification assistance (焊接工艺评定协助)
- Corrosion resistance selection guidance for specific service media (腐蚀介质选型指导)
- Field failure analysis and root cause investigation (现场失效分析与根本原因调查)
- Ongoing literature and training resources on coil tube integrity management (盘管完整性管理培训资料)
Note: This technical specification is derived from and informed by the internal engineering study "Causes and Improvement of Internal Coil Tube Connection Leakage" (《内盘管接管泄漏成因及改进》), which systematically addresses the five primary failure modes at coil tube connections — improper fit-up, inadequate weld penetration, thermal distortion, corrosion-induced degradation, and stress corrosion cracking — and prescribes validated corrective measures now embedded in the manufacturing and quality assurance protocols of Wenzhou Jixing Metal Materials Co., Ltd.