C68700 Aluminum Brass Tube in Desalination Plants: 3 Project Case Studies

ASTM B111 C68700 aluminum brass tube is the preferred material for desalination heat exchangers and evaporators. Over 40 desalination plants in the Middle East and North Africa use C68700 tubes. Thermal conductivity (105 W/m·K) is double that of C70600 copper nickel, cutting energy costs by 8–12%.

Location: Coastal power plant, Tianjin, China
Plant type: Multi-stage flash (MSF) desalination, 50,000 m³/day
C68700 tubes installed: 12,000 pieces, OD 25 mm × 2.0 mm wall × 6,000 mm length
Operating conditions: Seawater intake temperature 15–28°C, brine temperature 45°C, flow velocity 2.8 m/s

Problem before C68700: Original tubes were C27000 yellow brass. Failed in 3 years due to dezincification. Replacement cost: $480,000 per shutdown.

Solution: GNEE supplied ASTM B111 C68700-O60 seamless tubes. Surface treatment: as-drawn.

Results after 12 years:

Average dezincification depth: 0.28 mm

Maximum pit depth: 0.41 mm

Remaining wall thickness: 1.59 mm (from 2.0 mm original)

No tube replacements needed

Annual inspection cost: $8,000 (down from $35,000 with yellow brass)

Annual savings vs. yellow brass: $42,000 in maintenance + $480,000 avoided replacement every 3 years.

GNEE comment: C68700 paid for itself within 18 months. Plant now standardizes on C68700 for all seawater sections.

Location: Desalination plant, Fujairah, UAE
Plant type: Reverse osmosis (RO) with pre-heat exchanger, 100,000 m³/day
Seawater conditions: Temperature 28–35°C, chlorides 45,000 ppm, biofouling potential high

Challenge: Standard C68700 tubes showed barnacle attachment after 14 months. Cleaning required plant shutdown.

Solution: GNEE supplied nano-treated ASTM B111 C68700 tubes (polished inner surface + surface nanocrystallization). OD 32 mm × 2.5 mm wall.

Nano-treatment specifications:

Surface grain size: 50–100 nm (standard C68700: 10–30 microns)

Surface hardness: 220 HB (standard: 160 HB)

Corrosion resistance: +40% per ASTM G48

Biofouling attachment strength: 70% lower than standard

Results after 24 months:

Payback period: Nano-treated C68700 cost 18% more than standard. Saved $95,000 in cleaning and downtime in first 2 years. Payback: 7 months.

Location: Desalination plant, Barcelona, Spain (supplied via GNEE Europe distribution)
Plant type: Thermal vapor compression (TVC), 30,000 m³/day
Operating temperature: Brine side 75–85°C (above C68700 typical limit)

Challenge: Most suppliers refused to quote C68700 above 70°C. C70600 was quoted at 2.2× price.

GNEE solution: Supplied ASTM B111 C68700 tubes with controlled aluminum content (2.2–2.5%, above standard 1.5–2.5% range). Higher aluminum improves high-temperature oxide film stability.

Modified specification:

Aluminum: 2.2–2.5% (standard: 1.5–2.5%)

Wall thickness: 2.5 mm (extra safety margin)

Temper: Aged at 300°C for 2 hours (not standard O60)

Post-installation: Passivation with 15% nitric acid

Performance after 8 years:

Operating temperature: 78°C average

Measured dezincification rate: 0.045 mm/year (projected 0.07 mm/year at this temperature)

Tubes inspected at year 5 and year 8 – no failures

Plant expects 12–15 year life (C70600 would have achieved 20+ years but at 2.2× cost)

Cost comparison:

Verdict: C68700 provided lower annualized cost even at 78°C. Plant now uses GNEE's high-aluminum C68700 as standard for TVC sections.

GNEE recommendation: Use C68700 for 80% of desalination heat transfer applications. Use C70600 only for ammonia or >80°C. Use titanium only for high-velocity (>5 m/s) or very aggressive chemical cleaning.

GNEE (China) supplies these common desalination sizes from stock:

Lead time: Stock sizes: 7-10 days. Custom lengths: 15-20 days. Nano-treatment adds 5 days.

Q1: Is ASTM B111 C68700 suitable for high-temperature desalination brine?
A: Yes – up to 70°C for standard C68700, up to 85°C for high-aluminum (2.2-2.5%) version.
GNEE tested C68700 at 80°C for 6 months. Dezincification rate was 0.06 mm/year – acceptable for 2.5 mm wall tube (15+ year life). Above 85°C, switch to C70600 or titanium. Request GNEE's high-aluminum C68700 for any application above 70°C.

Q2: How does C68700 compare to C70600 for energy efficiency in desalination?
A: C68700 reduces energy consumption by 8-12% due to higher thermal conductivity (105 vs 45 W/m·K).
For a 50,000 m³/day plant, 8% energy savings = $350,000 per year (at $0.10/kWh). Over 15 years, C68700 saves $5.2 million in energy – far outweighing any material cost difference.

Q3: Does GNEE offer C68700 tubes with anti-biofouling coating for desalination?
A: No coating needed – nano-treated C68700 surface naturally resists biofouling.
Coatings peel off in high-flow desalination service. GNEE's nano-treatment modifies the metal surface itself: grain size reduced to 50-100 nm, barnacle attachment strength reduced 70%. In UAE case study (Case 2), nano-treated C68700 showed <5% biofouling after 24 months – better than coated titanium.

Q4: What is the maximum chlorides level for C68700 in desalination?
A: C68700 handles up to 50,000 ppm chlorides – typical for seawater desalination.
The aluminum oxide film is stable up to 50,000 ppm Cl⁻. Above this (e.g., brine reject at 70,000 ppm), specify 2.5 mm wall or nano-treated. GNEE has supplied C68700 for brine concentrations up to 65,000 ppm with no failures after 6 years.

Q5: Can I weld C68700 tubes in desalination heat exchangers?
A: Yes – but only for repair, not for original fabrication.
Desalination heat exchangers should use seamless tubes (ASTM B111) with rolled expansion into tube sheets. For repairs, weld with C68700 filler, then post-weld heat treat at 300°C for 1 hour. GNEE sells repair-length tubes (1-3 meters) for maintenance.

Q6: What is the typical delivery time for GNEE C68700 to Middle East desalination projects?
A: 25-35 days door-to-door from GNEE (China) to UAE, Saudi, or Qatar.
Stock sizes: 7 days production + 18 days shipping. Custom sizes: 20 days production + 18 days shipping. Nano-treated: add 5 days. GNEE has a Dubai warehouse for urgent projects (2-3 day delivery for stock sizes).

Q7: How does GNEE verify C68700 quality for desalination specifications?
A: Each batch undergoes 6 tests: chemical analysis, tensile, hardness, ASTM G48 dezincification, eddy current, and hydrostatic.
GNEE's lab is ISO 17025 certified. For desalination projects, GNEE adds a biofouling resistance test (60-day immersion in live seawater). Test report included with mill certificate. Third-party inspection (SGS, BV) available.

Q8: What is the cost difference between standard and nano-treated C68700 for desalination?
A: Nano-treated costs 18-22% more but extends cleaning interval from 8 months to 24+ months.
For a 100,000 m³/day plant, each cleaning shutdown costs $120,000 in lost production + $40,000 in labor. Nano-treated avoids 2 cleanings per year = $320,000 annual savings. Payback period: 3-4 months. GNEE recommends nano-treated for all warm-water desalination (above 25°C).

Every batch of C68700 material undergoes a strict multi-step inspection process. Using optical emission spectrometry (OES), we verify the chemical composition - especially the critical aluminum (2.0–3.0%) and arsenic content - to guarantee dezincification corrosion resistance. Tensile testing and Rockwell hardness checks confirm mechanical properties, while hydrostatic and ultrasonic tests ensure leak-free integrity for heat exchanger or condenser tube applications. We also provide full traceability reports, including dimensional, surface roughness, and grain size analyses. All tests are performed in our ISO 17025-accredited lab, ensuring compliance with ASTM B111, ASME SB111, or customer-specific standards.

After passing inspection, all tubes are packed according to export standards and customer-specific requirements. The packing process is documented below to ensure traceability and damage-free delivery.

Packing steps shown in video & images:
1. Tube cleaning & drying
2. Plastic end caps on both ends
3. VCI anti-rust paper wrapping
4. Bundle strapping with moisture barrier film
5. Plywood wooden case (ISPM-15 compliant) with foam padding
6. Labeling with ASTM grade, lot number, and inspection stamp

Our factory is equipped with advanced horizontal continuous casting machines, heavy-duty extrusion presses (up to 3,500 tons), and high-accuracy cold drawing lines specifically calibrated for C68700 aluminum brass. To ensure microstructure uniformity and defect-free surfaces, we also employ online eddy current testing systems and automatic cutting & chamfering units. The entire production process is controlled via a central SCADA system, enabling real-time monitoring of parameters like temperature, speed, and lubrication - guaranteeing consistent mechanical properties and dimensional accuracy for every C68700 tube or rod.

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