Stainless Steel & Titanium Coil Tubes (Coiltube) for Hydrolysis Kettles — Technical Specification
1. Product Overview
The Coil Tube (Coiltube) product line manufactured by Wenzhou Jixing Metal Materials Co., Ltd represents a specialized category of continuously wound tubular heat-transfer components designed for high-performance thermal exchange systems. These coil tubes are engineered primarily for integration into hydrolysis kettles and similar pressure vessels, where they serve as the core heat-transfer element, facilitating efficient thermal energy transfer between process fluids and heating/cooling media.
Coil tubes are distinguished from straight pipes by their continuous helical geometry, which significantly increases the surface-area-to-volume ratio within a compact footprint. This geometric advantage enables superior heat-transfer coefficients, reduced fluid residence time, and enhanced resistance to fouling compared to conventional straight-tube heat exchangers. The product line encompasses both stainless steel coil tubes (grades such as SUS304, SUS316L, SUS321) and titanium coil tubes (grades such as Gr.2, Gr.5), selected according to the corrosive environment and process requirements of the target application.
2. Material & Properties
2.1 Stainless Steel Grades
- SUS304 (AISI 304 / 1.4301) — General-purpose austenitic stainless steel with excellent formability, weldability, and moderate corrosion resistance. Suitable for non-chloride, mildly corrosive hydrolysis environments.
- SUS316L (AISI 316L / 1.4404) — Low-carbon austenitic grade with added molybdenum (Mo 2.0–2.5%), providing superior resistance to pitting and crevice corrosion, particularly in chloride-containing solutions.
- SUS321 (AISI 321 / 1.4541) — Titanium-stabilized austenitic grade with enhanced resistance to intergranular corrosion at elevated temperatures (up to 870 °C).
2.2 Titanium Grades
- Titanium Gr.2 (Ti Gr.2 / ASTM B348) — Commercially pure titanium with outstanding corrosion resistance in oxidizing acids, chloride solutions, and seawater. Ideal for hydrolysis kettles processing aggressive chemical media.
- Ti-6Al-4V (Ti Gr.5 / ASTM B348) — Alpha-beta titanium alloy offering higher mechanical strength (UTS ≥ 895 MPa) while retaining excellent corrosion resistance, suitable for high-pressure hydrolysis applications.
2.3 Key Mechanical & Physical Properties (Typical Values)
| Property | SUS304 (Annealed) | SUS316L (Annealed) | Ti Gr.2 (Annealed) | Ti-6Al-4V (Annealed) |
|---|---|---|---|---|
| Tensile Strength (UTS), MPa | ≥ 515 | ≥ 485 | ≥ 275 | ≥ 895 |
| Yield Strength (0.2% offset), MPa | ≥ 205 | ≥ 170 | ≥ 170 | ≥ 828 |
| Elongation (%), min. | 40 | 40 | 50 | 10 |
| Density, g/cm³ | 8.0 | 8.0 | 4.51 | 4.43 |
| Thermal Conductivity (25 °C), W/(m·K) | 16.3 | 14.6 | 21.9 | 7.0 |
| Maximum Service Temperature, °C | 870 | 870 | 400 | 400 |
| Corrosion Resistance (HCl 10%, 60 °C) | Poor | Moderate | Excellent | Excellent |
| Corrosion Resistance (Seawater) | Poor | Moderate | Excellent | Excellent |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Coil Tube (Coiltube) — 盘管 |
| Catalog Reference No. | 1663 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Tube Outer Diameter (OD) | Φ6 mm – Φ50 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch (Helix Pitch) | 10 mm – 80 mm (adjustable per thermal design) |
| Coil Diameter | Φ100 mm – Φ2000 mm |
| Coil Length / Turns | Up to 100+ turns; continuous winding without joints |
| End Forming | Flat end, beveled end, socket weld, or custom flanged connections |
| Surface Finish | Pickled & Passivated (Ra ≤ 0.8 μm); optional electropolished (Ra ≤ 0.4 μm) |
| Applicable Standards | ASTM A213 / A269, ASTM B348, GB/T 12771, GB/T 24511, EN 10216-5 |
| Pressure Rating | Up to 4.0 MPa (design-dependent); titanium grades up to 6.0 MPa |
| Operating Temperature Range | −196 °C to +400 °C (material-dependent) |
| Heat Treatment | Solution annealing (1050–1150 °C, water quench); stress relief for titanium |
4. Manufacturing Process
The production of high-precision coil tubes involves a rigorous multi-stage manufacturing sequence, each step critical to ensuring dimensional accuracy, metallurgical integrity, and corrosion resistance:
- Raw Material Selection & Verification — Certified bar stock or seamless tube from accredited mills (e.g., Outokumpu, KME, Tioxide, Baoji Titanium) undergoes incoming inspection for chemical composition (spectroscopic analysis), mechanical properties, and certification traceability.
- Tube Forming & Calibration — Seamless tubes are drawn, cold-worked, or hot-rolled to the required OD and wall thickness. Dimensional calibration ensures uniformity within ±0.05 mm tolerance.
- Coil Winding (Helical Forming) — The tube is wound around a precision-mandrel using CNC-controlled coil-winding machinery. The helix geometry (pitch, diameter, number of turns) is programmed to meet the specific thermal-exchange design parameters. Continuous winding eliminates weld joints, reducing potential leakage paths.
- Heat Treatment — Stainless steel coils undergo solution annealing followed by water quenching to restore full austenitic structure and maximize corrosion resistance. Titanium coils receive stress-relief annealing at 450–550 °C to relieve residual stresses introduced during winding.
- Pickling & Passivation — Coils are immersed in an acid bath (HNO₃/HF mixture) to remove scale and oxide layers, followed by passivation treatment to form a stable chromium-oxide protective film. Titanium coils receive hydrogen-peroxide or nitric-acid passivation.
- End Forming & Connection Fabrication — Tube ends are formed to the specified connection type (bevel, socket, flange, or custom fitting) using precision tooling.
- Pressure Testing & Non-Destructive Testing (NDT) — Each coil tube undergoes hydrostatic pressure testing at 1.5× the design pressure. Surface NDT (dye penetrant or magnetic particle inspection) and volumetric NDT (ultrasonic testing) are performed to detect subsurface defects.
- Final Inspection & Packaging — Dimensional verification, visual inspection, and certification documentation are completed. Coils are packaged in protective wooden crates or vacuum-sealed containers to prevent surface contamination during transit.
5. Applications
5.1 Hydrolysis Kettles (Primary Application)
The primary application highlighted in the technical study literature is the use of titanium coil tubes within hydrolysis kettles. Hydrolysis processes involve the chemical decomposition of compounds using water, often under elevated temperatures and pressures, in the presence of acidic or alkaline catalysts. The aggressive chemical environment demands exceptional corrosion resistance, which titanium coil tubes provide due to the formation of a self-healing, adherent TiO₂ passive film.
Key Finding from Technical Study: Titanium coil tubes installed in hydrolysis kettles demonstrated negligible wall-thickness reduction over extended service periods (exceeding 5 years), whereas conventional stainless steel alternatives exhibited significant pitting and intergranular corrosion under identical process conditions. The continuous helical geometry further enhanced heat-transfer efficiency by 30–50% compared to straight-tube designs, while the absence of weld joints eliminated potential failure points in the corrosive environment.
5.2 Additional Application Domains
- Pharmaceutical & Biotechnology — Reactor cooling/heating coils in GMP-compliant production environments; electropolished surfaces meet sanitary-grade requirements.
- Food Processing — UHT (Ultra-High Temperature) pasteurization systems, sterilization kettles, and CIP (Clean-in-Place) compatible heat exchangers.
- Chemical Processing — Acid digestion vessels, neutralization reactors, and evaporation systems handling chlorides, sulfates, and organic acids.
- Power Generation — Waste-heat recovery systems, feedwater preheating, and auxiliary cooling circuits.
- Marine & Offshore — Seawater heat exchangers and desalination plant components where chloride-induced stress corrosion cracking is a critical concern.
- Petrochemical — Crude oil fractionation, distillation column reboilers, and process condensers.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification |
| CE Marking | European conformity marking for pressure equipment (PED 2014/68/EU) |
| ASTM A213 / A269 | Standard specification for austenitic stainless steel seamless, welded, and wrought fittings |
| ASTM B348 | Standard specification for titanium and titanium alloy tube and pipe |
| GB/T 12771 | Chinese national standard for stainless steel seamless tubes |
| GB/T 24511 | Chinese national standard for stainless steel welded tubes |
| EN 10216-5 | European standard for non-ferrous metal tubes for general use |
| NACE MR0175 / ISO 15156 | Suitability for sour-service applications (H₂S-containing environments) |
| 3.1 / 3.2 Material Testing | Full material certification per EN 10204, including chemical analysis, mechanical test results, and NDT reports |
7. Unique Selling Points
- Joint-Free Continuous Winding — The seamless helical construction eliminates internal weld seams, drastically reducing the risk of stress-corrosion cracking (SCC) and leakage in aggressive hydrolysis environments.
- Superior Heat-Transfer Performance — The helical geometry induces secondary flow (Dean vortices), enhancing turbulent mixing and achieving heat-transfer coefficients 30–50% higher than equivalent straight-tube designs.
- Material Versatility — Availability in both stainless steel and titanium grades allows engineers to optimize the cost-performance ratio based on the specific corrosive medium, temperature, and pressure conditions.
- Customizable Geometry — Coil diameter, pitch, number of turns, and end-forming configurations are tailored to the exact thermal-hydraulic design requirements of each vessel.
- Extended Service Life in Hydrolysis — Empirical data from field installations confirms that titanium coil tubes in hydrolysis kettles exhibit wall-thickness reduction rates below 0.01 mm/year, significantly outperforming standard stainless steel alternatives.
- Full Traceability & Certification — Every coil tube is accompanied by a complete quality dossier including mill certificates, chemical analysis reports, mechanical test data, NDT results, and pressure-test records, ensuring full regulatory compliance.
8. Conclusion
The Coil Tube (Coiltube) product line from Wenzhou Jixing Metal Materials Co., Ltd represents a state-of-the-art solution for thermal management in hydrolysis and chemical processing applications. The combination of advanced metallurgical materials (stainless steel and titanium), precision CNC coil-winding technology, and rigorous quality assurance protocols delivers components that are simultaneously high-performance, corrosion-resistant, and fully compliant with international standards. The technical study literature on titanium coil tubes in hydrolysis kettles further validates the exceptional durability and thermal efficiency of these products, positioning them as the preferred choice for demanding industrial process environments.