Overview: The Cost-Effective Solution for High-Velocity Seawater Cooling
ASTM B111 C68700 (Aluminum Brass) is a high-performance copper-zinc alloy seamless tube engineered specifically for the rigorous cooling water circuits of coastal power plants. Manufactured strictly to ASTM B111 standards, this alloy is widely recognized as the industry benchmark for main and auxiliary steam surface condensers operating on raw seawater.
Unlike standard brass tubes that suffer from rapid dezincification, C68700 integrates a precise addition of aluminum (approx. 2%) and trace amounts of arsenic. This unique metallurgical design solves two catastrophic operational challenges in power generation: high-velocity seawater impingement attack and selective dezincification corrosion. For power plant EPC contractors and utility procurement managers, C68700 offers a proven, highly economical solution that ensures continuous thermal efficiency, minimizes unplanned turbine shutdowns, and delivers a predictable, long-term service lifecycle.
Application & Compliance: Where It is Used and What Problems It Solves
In coastal power generation, the condenser is the most critical heat exchanger. A single tube failure can lead to seawater ingress into the high-purity boiler feedwater, causing catastrophic equipment damage. Our C68700 tubes are deployed in specific power plant scenarios to mitigate these risks.
1. Main Steam Surface Condensers
Working Scenario: The tube bundle experiences continuous exposure to high-velocity, oxygenated, and often polluted seawater. The cooling water flows rapidly through the tubes to maintain a strict vacuum on the shell side.
What it solves: C68700's aluminum-rich surface forms a dense, self-repairing oxide layer. This provides exceptional resistance to impingement attack at the tube inlets, preventing wall thinning and premature failure caused by turbulent seawater flow.
2. Auxiliary Condensers & Cooling Water Heat Exchangers
Working Scenario: Frequent thermal cycling and exposure to varying seawater velocities during plant load changes.
What it solves: The addition of arsenic acts as a potent inhibitor against selective dezincification. It prevents the aggressive loss of zinc from the brass matrix, ensuring that the tube retains its structural strength and pressure integrity over decades of operation.
3. Why Choose C68700 over C7060X (90/10 CuNi)?
Cost Efficiency: For coastal plants where seawater quality is relatively stable and flow rates are kept within standard design parameters (typically up to 2.2 - 2.5 m/s), C68700 provides an excellent heat transfer coefficient at a significantly lower CAPEX compared to Cupronickel. It is the pragmatic choice for conventional coastal condensers.
Technical Specifications & Material Comparison
We supply ASTM B111 C68700 tubes in exact dimensions to match your condenser tube sheets and maintain optimal water velocity.
1. Dimensional & Mechanical Properties
| Parameter | Standard Specification (ASTM B111 C68700) |
|---|---|
| Outer Diameter (OD) | 12.7 mm to 35.0 mm (Standard condenser sizes) |
| Wall Thickness (WT) | 0.7 mm to 1.5 mm (BWG 12 to BWG 18) |
| Temper Condition | Soft Annealed (O61) / Light Drawn |
| Tensile Strength | Min. 370 MPa (54 ksi) |
| Yield Strength | Min. 140 MPa (20 ksi) |
| Elongation | Min. 40% (Excellent for roller tube expansion) |
| Thermal Conductivity | Approx. 105 W/(m·K) |
| Standard Length | 6 meters / 12 meters or custom cutting |
2. Chemical Composition (Critical for Anti-Dezincification)
| Element | Cu | Al | As (Arsenic) | Zn | Pb | Fe |
|---|---|---|---|---|---|---|
| Min. | 76.0 | 1.8 | 0.02 | Remainder | - | - |
| Max. | 79.0 | 2.5 | 0.06 | - | 0.07 | 0.06 |
(Note: The Arsenic (As) content is strictly controlled between 0.02% and 0.06% to guarantee resistance to dezincification).
3. Material Selection Matrix (Coastal Power Plants)
| Material | Max Seawater Flow | Anti-Dezincification | Impingement Resistance | Relative Cost |
|---|---|---|---|---|
| C68700 (Aluminum Brass) | 2.2 - 2.5 m/s | Excellent (with As) | Excellent | Low - Moderate |
| C7060X (90/10 CuNi) | 2.4 - 3.0 m/s | N/A | Superior (Sand/High flow) | Moderate |
| C71500 (70/30 CuNi) | > 3.5 m/s | N/A | Outstanding | High |
| Carbon Steel | < 1.0 m/s | Poor | Poor | Very Low |
QA/QC & Certifications: Proof of Reliability for Power Utilities
For power plant utility procurement, material failure is not an option. We enforce stringent quality control and provide comprehensive documentation for EPC project approval.
100% Eddy Current Testing: Every inch of the C68700 tube undergoes non-destructive testing (NDT) according to ASTM E243 to detect any internal defects, wall thickness variations, or cracks.
Hydrostatic Testing: Tubes are tested under high pressure to guarantee absolute leak-free performance before installation.
Material Test Certificates (MTC): EN 10204 3.1 Mill Test Certificates are issued with every shipment. The chemical composition, especially the Arsenic (As) content, is clearly recorded to prove compliance with anti-dezincification requirements.
Third-Party Inspection: We fully support and coordinate pre-shipment inspections by SGS, BV, TUV, or the plant's designated third-party inspection agency.
Eddy Current Report: Detailed EC test reports with a 100% scanning record are provided alongside the delivery.
Installation & Maintenance Guide (For EPC Contractors)
To maximize the 20-30 year lifespan of C68700 tubes in a coastal power plant, proper installation and operational control are mandatory:
Strict Velocity Control: Maintain the seawater flow rate strictly below 2.5 m/s inside the tubes. High local velocities caused by tube blockages (debris, bio-fouling) will strip the protective aluminum oxide film and cause rapid impingement attack.
Tube Expansion: The excellent elongation of soft-annealed C68700 allows for easy roller expansion. Ensure the expansion degree is controlled to avoid over-rolling stress.
Water Quality Monitoring: While C68700 is resistant to dezincification, it is sensitive to polluted seawater containing high levels of ammonia or hydrogen sulfide. Continuous monitoring of cooling water quality is recommended.
Cleaning Practices: Use soft nylon brushes or low-pressure hydro-blasting for routine cleaning. Never use carbon steel wire brushes, as embedded iron particles will cause localized galvanic corrosion.
B2B Purchasing Terms & Commercial Conditions
We understand the stringent procurement metrics of EPC projects. We offer transparent terms to ensure your supply chain proceeds without friction.
MOQ (Minimum Order Quantity): 1 Ton (approx. 500 pieces for standard sizes) per size. For urgent maintenance and retubing projects, we can negotiate based on current mill stock.
FOB Lead Time:
Standard sizes in stock: 10 to 15 days.
Custom OD/WT production for large EPC orders: 25 to 35 days after receipt of the prepayment or Irrevocable L/C.
Payment Terms: 30% T/T Advance Deposit, 70% balance against copy of B/L. Alternatively, 100% Irrevocable L/C at sight for large utility contracts.
Packaging & Shipping (Seaworthy Export Standard):
Tubes are bundled with plastic end-caps to prevent seawater/moisture ingress during transit.
Wrapped in neutral VCI (Volatile Corrosion Inhibitor) anti-rust paper.
Secured in export-grade wooden cases with steel strapping. Max 2,000 kgs per case to ensure safe lifting and transport.
FAQ: Sourcing C68700 Tubes for Power Plants
Q1: How do you guarantee the anti-dezincification performance of C68700?
A: We strictly control the Arsenic (As) content between 0.02% and 0.06% during the melting process. The MTC will clearly show this data. We also conduct accelerated corrosion tests (Mercury Nitrate Test) upon request to verify dezincification resistance.
Q2: What is the typical FOB lead time for an EPC condenser retubing project?
A: For standard condenser sizes (e.g., 25.4mm OD x 1.24mm WT), our lead time is typically 15-25 days. We prioritize power plant maintenance schedules and can arrange expedited shipping if required.
Q3: Are your tubes suitable for roller expansion into a Naval Brass or Muntz Metal tube sheet?
A: Yes. C68700 is highly ductile and pairs perfectly with Naval Brass tube sheets. It is recommended to use a controlled roller expansion process (typically 4%-6% wall thinning) to prevent stress corrosion cracking.
Q4: Can you provide test certificates for EPC compliance?
A: Absolutely. We provide EN 10204 3.1 MTC, 100% Eddy Current Test reports, and Hydrostatic Test certificates. If your project requires 3.2 certification (witnessed by a third party), we can arrange that with SGS or BV prior to shipment.
