Stainless Steel Coil Tube for Converter Station Valve Cooling System
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-tube product designed specifically for high-voltage direct current (HVDC) converter station valve cooling systems. This product serves as a critical component within cooling tower heat exchange assemblies, where it facilitates efficient thermal dissipation from the valve hall's high-power thyristor valves. The coil tube architecture eliminates the need for welded joints along the tube length, thereby minimizing potential leak points and enhancing system reliability under continuous high-pressure, high-temperature operating conditions.
This product line has been developed with reference to advanced research on converter station valve cooling system cooling tower coil descaling electric device technology, incorporating lessons learned from industrial descaling mechanisms to optimize coil tube geometry, surface finish, and material selection for maximum heat transfer efficiency and long-term fouling resistance.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, primarily utilizing the following material grades:
- SUS 304 / ASTM A213 TP304 — General-purpose austenitic stainless steel offering excellent corrosion resistance and formability.
- SUS 316L / ASTM A213 TP316L — Low-carbon, molybdenum-enhanced austenitic stainless steel providing superior resistance to pitting and crevice corrosion in cooling water environments.
- SUS 321 / ASTM A213 TP321 — Titanium-stabilized austenitic stainless steel for applications requiring enhanced resistance to intergranular corrosion at elevated temperatures.
Key material properties include:
- Non-magnetic in the annealed condition
- Excellent resistance to oxidation at temperatures up to 870°C (1600°F)
- Superior resistance to scaling and corrosion in cooling water (including treated water containing inhibitors)
- High ductility enabling continuous coiling without cracking
- Smooth internal surface finish (Ra ≤ 0.8 μm) to minimize scale adhesion and facilitate automated cleaning
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Product Code | No. 299 |
| Outer Diameter (OD) | 12 mm – 50 mm (customizable) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Length | Up to 500 m per continuous coil |
| Coil Outer Diameter | 500 mm – 2000 mm |
| Material Grades | SUS 304, SUS 316L, SUS 321, SUS 310S |
| Surface Finish | Bright annealed / Pickled & Passivated |
| Internal Surface Roughness | Ra ≤ 0.8 μm (polished available on request) |
| Tolerance on OD | ±0.05 mm |
| Tolerance on Wall Thickness | ±0.03 mm |
| Operating Temperature Range | -196°C to +870°C |
| Maximum Operating Pressure | Up to 2.5 MPa (design-dependent) |
| Applicable Standards | ASTM A213/A213M, GB/T 12771, EN 10216-5 |
| End Condition | Plain end / Beveled / Threaded (customizable) |
| Packaging | Wooden drum / Steel frame with moisture-proof wrapping |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Hot Rolling & Annealing — The parent stainless steel strip is hot-rolled to approximate dimensions and then solution-annealed to achieve a uniform austenitic microstructure with maximum ductility.
- Precision Cold Drawing — The strip undergoes multi-pass cold drawing through calibrated dies to achieve the exact target outer diameter and wall thickness with tight tolerances.
- Intermediate Annealing — Periodic annealing cycles are performed during cold working to relieve accumulated work-hardening and maintain formability throughout the drawing process.
- Continuous Coiling — The drawn tube is fed through a series of guide rollers and a coiling head, forming a continuous spiral coil without any intermediate welding or splicing. This is the defining characteristic of the coil tube product.
- Final Annealing & Pickling — The coiled tube is subjected to a final annealing and acid pickling treatment to remove scale, restore the passive chromium oxide layer, and ensure a bright, corrosion-resistant surface.
- Passivation Treatment — A chemical passivation step further enriches the surface chromium content, enhancing long-term corrosion resistance in cooling water environments.
- Quality Inspection — Each coil undergoes 100% visual inspection, dimensional verification, hydrostatic pressure testing, and periodic destructive testing (tensile, hardness, grain structure analysis).
- Internal Polishing (Optional) — For applications requiring ultra-smooth internal surfaces to resist scaling and facilitate descaling operations, mechanical or electrochemical internal polishing is applied.
Applications
The stainless steel coil tube is engineered for demanding thermal management applications, with primary use cases including:
- HVDC Converter Station Valve Cooling Systems — Serves as the primary heat transfer element in cooling tower heat exchangers, dissipating waste heat generated by high-power thyristor valves in ±500 kV, ±800 kV, and ±1100 kV converter stations.
- Cooling Tower Coil Descaling Systems — Designed to integrate with electric descaling devices, the smooth internal surface and precise geometry facilitate effective scale removal and long-term maintenance of heat transfer efficiency.
- Nuclear Power Plant Cooling Loops — Used in secondary and tertiary cooling circuits where high corrosion resistance and non-magnetic properties are mandatory.
- Chemical Processing Heat Exchangers — Deployed in aggressive chemical environments requiring continuous, joint-free tubing for thermal exchange.
- Power Generation Auxiliary Cooling — Applied in condensate cooling, turbine oil cooling, and generator hydrogen cooling systems in thermal and gas-fired power plants.
- Marine Engineering — Utilized in seawater-cooled heat exchangers aboard naval and commercial vessels.
Unique Selling Points
- Joint-Free Continuous Construction — The coil tube is formed as a single continuous length, eliminating hundreds of potential leak points that would exist in a welded tube assembly of equivalent length, dramatically improving system integrity and reducing maintenance requirements.
- Enhanced Fouling Resistance — The precision internal surface finish (Ra ≤ 0.8 μm) minimizes scale nucleation sites, extending the time between required descaling interventions and maintaining peak thermal performance over extended operating cycles.
- Reference-Grade Design Basis — Product development incorporates validated engineering insights from converter station valve cooling system cooling tower coil descaling research, ensuring real-world performance in the most demanding HVDC transmission environments.
- Material Versatility — Available in multiple stainless steel grades to match specific environmental and performance requirements, from general cooling water (SUS 304) to aggressive chloride-containing environments (SUS 316L).
- Customizable Geometry — Coil dimensions, tube diameter, wall thickness, and end configurations are tailored to the specific heat exchanger design and installation constraints of each project.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure consistent product performance and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and supply chain processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- EN 10204 Type 3.1 — Third-party inspection and certification for each batch of coil tubes, including material composition analysis, mechanical testing, and dimensional verification.
- Mill Test Certificates (MTC) — Provided with every shipment, documenting chemical composition (per ASTM E415), mechanical properties (per ASTM E8/E8M), and heat treatment history.
- Hydrostatic Test Report — 100% of coils are subjected to hydrostatic pressure testing at 1.5 times the maximum design pressure, with test results documented.
- NACE MR0175 / ISO 15156 — Compliance available for coil tubes intended for use in sour service environments.
- Nuclear Quality Assurance (NQA-1) — Available upon request for coil tubes supplied to nuclear-grade applications.
Note: All specifications are subject to project-specific requirements and applicable engineering standards. Customers are advised to provide detailed design parameters, operating conditions, and applicable code requirements to facilitate optimal product selection and specification. Wenzhou Jixing Metal Materials Co., Ltd. offers full engineering support, including thermal hydraulic analysis, material selection consultation, and on-site technical assistance for converter station valve cooling system integrations.