Marine Seawater Cooler Coil Tube — CuNi 70/30 & Duplex 2205
Product Overview
The Marine Seawater Cooler Coil Tube (Model No. 159) is a precision-engineered coil tube product specifically designed for shipboard seawater cooling systems operating under demanding marine conditions. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is engineered to withstand continuous exposure to seawater at temperatures exceeding 30°C, aggressive biological fouling, and sustained flow velocities of 2–3 m/s. The product is constructed from either Copper-Nickel Alloy 70/30 (CuNi 70/30) or Duplex Stainless Steel 2205 (UNS S31803/S32205), both materials selected for their exceptional corrosion resistance in chloride-rich marine environments.
This coil tube represents a critical component in the seawater system of marine engineering applications, serving as the heat exchange medium in onboard cooling circuits that manage thermal loads for auxiliary engines, generators, and other critical shipboard systems. The product incorporates an anti-marine organism attachment design to mitigate biofouling, which is a primary cause of reduced thermal efficiency and accelerated degradation in seawater cooling applications.
Material & Properties
Copper-Nickel Alloy 70/30 (CuNi 70/30)
- Composition: 70% Copper (Cu), 30% Nickel (Ni), with trace elements of Iron (Fe), Tin (Sn), and Zinc (Zn)
- UNS Designation: C70600 / C70300
- ASTM Standard: ASTM B111 (Bar and Rod), ASTM B152 (Tube)
- Tensile Strength: 310–450 MPa (depending on condition)
- Elongation: ≥ 25%
- Corrosion Resistance: Superior resistance to seawater corrosion; forms a protective copper-nickel oxide film that self-heals upon exposure to oxygenated seawater
- Thermal Conductivity: 28–40 W/(m·K) — favorable for heat exchange efficiency
- Maximum Operating Temperature: Up to 300°C (short-term); sustained operation at seawater temperatures above 30°C is well within design limits
Duplex Stainless Steel 2205 (UNS S31803 / S32205)
- Composition: ~22% Chromium (Cr), ~5% Nickel (Ni), ~3% Molybdenum (Mo), ~1.5% Nitrogen (N), ~6% Iron (Fe) balance
- UNS Designation: S31803 (standard) / S32205 (higher nitrogen variant)
- ASTM Standard: ASTM A790 (Tube), ASTM A188 (Tube)
- Tensile Strength: 550–800 MPa
- Elongation: ≥ 20%
- PREN (Pitting Resistance Equivalent Number): 32–38, indicating excellent resistance to pitting and crevice corrosion in chloride environments
- Corrosion Resistance: Outstanding resistance to chloride-induced stress corrosion cracking (Cl-SCC); suitable for high-temperature seawater applications
- Thermal Conductivity: 15–18 W/(m·K)
- Maximum Operating Temperature: Up to 350°C (continuous); well suited for sustained seawater temperatures above 30°C
Key Material Performance Under Operating Conditions
| Performance Parameter | CuNi 70/30 | Duplex 2205 | Operating Requirement |
|---|---|---|---|
| Seawater Temperature Resistance | ≥ 30°C (continuous) | ≥ 30°C (continuous) | 30°C+ |
| Flow Velocity Tolerance | Up to 5 m/s | Up to 5 m/s | 2–3 m/s |
| Corrosion Rate (ASTM G48) | < 0.05 mm/year | < 0.02 mm/year | Ultra-low corrosion |
| Biofouling Resistance | High (self-passivating surface) | High (passive film stability) | Anti-organism attachment |
| Pitting Resistance (PREN) | N/A (non-ferrous) | 32–38 | High PREN required |
| Design Service Life | 15–20 years | 20–25 years | Full vessel lifecycle |
Specifications
| Specification Item | Parameter / Value |
|---|---|
| Product Name | Marine Seawater Cooler Coil Tube |
| Model / Catalog No. | 159 |
| Material Options | CuNi 70/30 (C70600/C70300) or Duplex 2205 (S31803/S32205) |
| Outer Diameter (OD) | Standard: 12.7 mm, 15.9 mm, 19.0 mm, 22.2 mm, 25.4 mm (custom sizes available) |
| Wall Thickness | 1.0 mm – 2.5 mm (customizable per application requirements) |
| Coil Inner Diameter (CID) | 100 mm – 600 mm (configurable based on heat exchanger geometry) |
| Coil Length | Up to 1,500 m per coil (continuous winding) |
| Operating Seawater Temperature | Up to 30°C+ (continuous operation) |
| Flow Velocity | 2–3 m/s (design range) |
| Surface Finish | Anti-marine organism attachment surface treatment; Ra ≤ 0.4 μm (polished) or Ra ≤ 0.8 μm (standard) |
| Manufacturing Standard | ASTM B152 (CuNi), ASTM A790/A188 (Duplex); EN 10217-7 |
| Welding Compatibility | TIG (GTAW) welding compatible; filler materials matched to base metal |
| Maximum Design Pressure | 1.6 MPa (standard); up to 4.0 MPa (thick-wall configuration) |
| Delivery Condition | Coiled, with end protection caps; descaled and passivated |
Manufacturing Process
The production of the Marine Seawater Cooler Coil Tube follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, material integrity, and corrosion performance:
- Material Selection & Incoming Inspection: Raw material coils are sourced from certified mills (e.g., Outokumpu, VDM Metals, Jiangsu Jiuli for CuNi). Each batch undergoes full chemical analysis (spectrographic) and mechanical property verification prior to acceptance.
- Hot Rolling & Annealing: Billet or slab stock is hot-rolled to produce seamless tube blanks. Subsequent solution annealing (1050–1100°C for Duplex 2205; 950–1050°C for CuNi 70/30) ensures optimal microstructural homogeneity and corrosion resistance.
- Pilger Drawing / Cold Drawing: The tube blank is cold-drawn through precision dies to achieve the final outer diameter and wall thickness with tight dimensional tolerances (± 0.05 mm OD; ± 0.02 mm wall thickness).
- Intermediate Annealing: Where multiple drawing passes are required, intermediate annealing relieves accumulated cold-work stresses and restores formability without compromising the corrosion-resistant microstructure.
- Coil Winding: The drawn tube is wound onto precision mandrels using CNC-controlled coiling equipment to produce uniform coil geometry with consistent pitch and no kinking or ovality.
- Surface Treatment & Anti-Fouling Design: The coil tube surface undergoes specialized treatment — including electrolytic polishing (for Duplex 2205) or controlled oxide film stabilization (for CuNi 70/30) — to minimize marine organism attachment. The anti-marine organism attachment design incorporates surface micro-texturing and/or specialized coating technologies that inhibit biofilm formation and fouling organism colonization.
- Passivation & Descaling: Acid pickling (nitric/hydrofluoric acid blend for stainless; sulfuric acid for CuNi) followed by water rinsing to remove all surface contaminants and establish a stable passive film.
- Final Quality Inspection: Each coil undergoes hydrostatic pressure testing (ASTM A751), ultrasonic flaw detection (ASTM A576 for seamless tubes), visual surface inspection, and dimensional verification per customer specifications.
Applications
Primary Application: Marine Engineering — Seawater Systems
The Marine Seawater Cooler Coil Tube (Model 159) is purpose-built for the seawater system segment of marine engineering, with the following specific applications:
- Shipboard Seawater Coolers: Primary heat exchanger tubes in seawater-cooled systems for diesel main engines, auxiliary engines, and generators on commercial vessels, container ships, tankers, and offshore support vessels.
- Offshore Platform Cooling Systems: Seawater cooling loops for topside equipment, hydraulic systems, and gas compressors on fixed and floating production platforms.
- Marine Auxiliary Machinery: Cooling circuits for turbochargers, lube oil coolers, jacket water coolers, and exhaust gas coolers.
- Subsea Systems: Seawater intake and distribution manifolds in subsea production systems requiring corrosion-resistant coil tubing.
- Naval Vessel Cooling: Seawater cooling applications in naval and defense vessels where material reliability under extreme conditions is paramount.
Operating Environment Challenges Addressed
- High Seawater Temperature (30°C+): Tropical and subtropical operating conditions where elevated seawater temperatures accelerate corrosion and reduce heat transfer efficiency.
- Aggressive Biological Fouling: Tropical waters with high concentrations of fouling organisms (barnacles, tube worms, mussels, biofilm bacteria) that deposit on tube surfaces and reduce flow area.
- Elevated Flow Velocity (2–3 m/s): High-velocity seawater flow that induces erosion-corrosion synergy and cavitation risk, requiring materials with superior erosion-corrosion resistance.
Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering the full manufacturing process from raw material procurement through final inspection. |
| ISO 14001:2015 | Environmental Management System certification demonstrating sustainable manufacturing practices and environmental compliance. |
| ISO 3834-2 | Quality requirements for welding of metallic materials — ensures welding process qualification for coil tube fabrication and repair. |
| EN 10204 3.1 | Inspection document (certificate of compliance) — independent third-party inspection of material and product conformity. |
| EN 10204 3.2 | Inspection document (product certificate) — manufacturer's declaration of conformity with specified requirements. |
| ASTM B152 / B111 | Compliance with ASTM standards for copper-nickel alloy tube and bar products. |
| ASTM A790 / A188 | Compliance with ASTM standards for austenitic and duplex stainless steel tube products. |
| DNV-GL / |