Stainless Steel Coil Tube (Coil Tube) for Industrial Heat Exchanger Applications
1. Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. supplies high-performance Stainless Steel Coil Tubes (盘管) engineered for demanding industrial heat exchange applications, particularly within ammonia storage and processing facilities. These coil tubes are precision-formed into continuous helical or spiral configurations, designed to maximize heat transfer surface area within compact installation footprints. The product is widely deployed in liquid ammonia evaporators (液氨蒸发器), refrigeration systems, chemical processing plants, and power generation facilities where reliable thermal management is critical.
Coil tubes present unique engineering challenges compared to straight tube applications, including susceptibility to internal blockage (堵塞), vibration-induced fatigue, and thermal stress accumulation. Wenzhou Jixing addresses these challenges through optimized material selection, precise manufacturing tolerances, and rigorous quality control protocols, ensuring long service life and operational safety in ammonia service environments.
2. Material & Properties
The coil tubes are manufactured from austenitic stainless steel grades selected for their superior corrosion resistance, mechanical integrity, and compatibility with ammonia media. Key material grades include:
- SUS304 / AISI 304 — General-purpose austenitic stainless steel offering excellent corrosion resistance in non-chloride environments; minimum nickel (Ni) content of 8.0%.
- SUS316L / AISI 316L — Low-carbon variant with added molybdenum (Mo 2.0–3.0%) for enhanced resistance to pitting and crevice corrosion; preferred for ammonia service.
- SUS321 / AISI 321 — Titanium-stabilized grade providing superior resistance to intergranular corrosion and thermal stress cracking under cyclic heating conditions.
| Property | Specification |
|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa (AISI 304); ≥ 485 MPa (AISI 316L) |
| Yield Strength (屈服强度) | ≥ 205 MPa |
| Elongation (延伸率) | ≥ 40% (A50mm) |
| Thermal Conductivity (热导率) | 14.9 W/(m·K) at 25°C (AISI 304) |
| Operating Temperature Range | −196°C to +870°C (non-cyclic); −196°C to +425°C (cyclic/pressure vessels) |
| Corrosion Resistance (氨腐蚀) | Excellent resistance to anhydrous ammonia and aqueous ammonia solutions |
| Surface Finish (表面粗糙度) | Ra ≤ 0.8 μm (interior); Ra ≤ 1.6 μm (exterior) |
3. Specifications
| Parameter | Typical Specification |
|---|---|
| Outer Diameter (外径) | Φ6.35 mm – Φ38.1 mm (standard); custom sizes available |
| Wall Thickness (壁厚) | 0.5 mm – 3.0 mm |
| Coil Pitch (盘管节距) | 10 mm – 50 mm (adjustable per design) |
| Coil Diameter (盘管直径) | Φ100 mm – Φ2000 mm |
| Coil Length (盘管长度) | 5 m – 200 m (continuous coil); custom lengths available |
| Pressure Rating (压力等级) | Up to 4.0 MPa (working pressure); design pressure per GB 150 / ASME VIII |
| Standard (执行标准) | GB/T 14976, GB/T 13296, ASTM A213, EN 10216-5 |
| Connection Type (连接方式) | Welded (TIG/自动氩弧焊), Flanged, or Threaded end fittings |
| Surface Treatment (表面处理) | Pickled & Passivated (酸洗钝化); optional electropolishing |
4. Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage process chain ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Preparation — Cold-rolled stainless steel strip or seamless tube stock (from certified mills such as Outokumpu, POSCO, or domestic Tier-1 producers) undergoes incoming inspection including chemical composition analysis (光谱分析) and mechanical property verification.
- Tube Forming (制管) — Strip is formed into round tube via precision roll-forming or drawn from seamless stock, with controlled reduction ratios to maintain grain structure integrity.
- Coil Bending (盘绕成型) — The formed tube is bent into helical coil geometry using CNC-controlled coil winding machines. Bend radii are calculated to prevent ovalization (椭圆度 ≤ 2%) and avoid compressive wrinkling on the inner fiber of the bend.
- Welding & Joining (焊接) — End-to-end joints and header connections are performed using Gas Tungsten Arc Welding (GTAW/TIG) with argon shielding gas, ensuring full-penetration welds with minimal heat-affected zone (HAZ) distortion.
- Pickling & Passivation (酸洗钝化) — The finished coil is subjected to nitric acid/hydrofluoric acid pickling to remove oxide scale and welding discoloration, followed by passivation to form a protective chromium oxide film (Cr₂O₃), critical for ammonia service corrosion resistance.
- Hydrostatic Pressure Testing (水压试验) — Each coil assembly is pressure-tested at 1.5× working pressure with hold time of minimum 10 minutes to verify leak-tightness and structural integrity.
- Final Inspection (终检) — Dimensional verification (laser measurement), surface roughness profiling, and visual/dye penetrant testing (PT) of welds per ASME Section V.
5. Applications
Wenzhou Jixing stainless steel coil tubes serve a broad spectrum of industrial applications:
- Ammonia Evaporators (氨蒸发器) — Primary application in ammonia storage and vaporization systems; coil tubes facilitate efficient heat absorption for liquid-to-vapor phase change.
- Industrial Refrigeration (工业制冷) — Heat exchange coils in ammonia-based refrigeration circuits for food processing, cold storage, and chemical plants.
- Chemical Processing (化工) — Reactor jacket cooling, distillation column condensers, and heat recovery systems handling corrosive media.
- Power Generation (发电) — Economizer tubes and air preheater elements in boiler systems.
- Marine & Offshore (海洋工程) — Seawater-cooled heat exchanger coils with enhanced corrosion-resistant grades.
- Pharmaceutical & Food Industry (医药食品) — Sanitary-grade coils for pasteurization, sterilization, and CIP (Clean-in-Place) systems requiring electropolished surfaces.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification covering the full manufacturing and supply chain.
- ISO 14001:2015 — Environmental Management System certification.
- GB/T 19001 — Chinese national standard for quality management systems.
- Pressure Vessel Compliance — Products manufactured per GB 150 (压力容器), ASME BPV Section VIII, and TSG 21 regulations.
- Material Traceability — Each coil tube batch is accompanied by a Mill Test Certificate (MTC/材质证明书) with full chemical composition (CE/EN 10204 Type 3.1) and mechanical test data.
- NDE Compliance — Non-Destructive Testing (无损检测) including Dye Penetrant Testing (PT), Radiographic Testing (RT), and Ultrasonic Testing (UT) per ASME Section V and EN ISO 17637.
7. Unique Selling Points & Anti-Blockage Engineering
Based on extensive field experience with ammonia evaporator coil blockage incidents (氨区液氨蒸发器盘管堵塞), Wenzhou Jixing integrates specialized engineering solutions directly into the product design:
Key Differentiators:
- Optimized Interior Surface Finish — Electropolished interior surfaces (Ra ≤ 0.4 μm) significantly reduce fouling (结垢) and ammonia decomposition product accumulation, directly addressing the primary cause of coil blockage in ammonia service.
- Smooth Bend Geometry — Large bend radii (R ≥ 5×D) and uniform coil pitch minimize flow turbulence and dead zones where particulate deposition and ice formation (结冰) can initiate blockage.
- Anti-Corrosion Passivation — Enhanced passivation treatment specifically formulated for ammonia environments, preventing localized pitting that can lead to tube wall thinning and eventual perforation.
- Customizable Flow Velocity Design — Engineering support to optimize coil diameter and pitch for target flow velocities (≥ 1.0 m/s minimum) that prevent sedimentation and maintain self-cleaning characteristics.
- Integrated Drainage & Purge Ports — Coil assemblies can be designed with integrated drain points and purge connections to facilitate maintenance and prevent residual ammonia accumulation during shutdown.
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including coil layout design, flow simulation (CFD analysis), and maintenance guidance to ensure maximum operational reliability and service life in demanding ammonia processing environments.