ASME SB111 C68700 U Bend Boiler Tube Application

1. Marine & Offshore Systems

• Seawater Cooled Condensers & Heat Exchangers: Shipboard condensers (main engine cooling), Offshore oil rig heat exchangers (cooling hydraulic systems, lube oil), Desalination plants (multi-stage flash evaporators).

2. Power Generation (Fossil & Nuclear)

• Steam Surface Condensers: Coastal/nuclear power plants (seawater-cooled condensers), Waste heat recovery units (exhaust gas boilers).

3. Chemical & Petrochemical Processing

• Application: Corrosive Fluid Heat Transfer: Refinery coolers (hydrocarbon processing), Ammonia condensers (fertilizer plants).

4. HVAC & Refrigeration

• Chillers & Evaporators: Compact design fits shell-and-tube evaporators (e.g., industrial chillers), Seawater-cooled HVAC (tropical coastal buildings), Industrial refrigeration systems.

5. Industrial Process Cooling

• High-Temperature/Pressure Exchangers: Meets strict dimensional tolerances for high-pressure systems, Brewery/distillery wort coolers, Pulp & paper mill heat recovery.

ASME SB111 C68700 Bend Boiler Tube Strength

1. Mechanical Properties of C68700 Aluminum Brass The SB111 specification ensures the tube meets certain strength criteria.

Typical room-temperature properties for C68700 (ASTM B111, ASME SB111) are:

2. Factors Affecting Strength

A. Temperature Effects

• At Elevated Temperatures (~150–250°C / 302–482°F):
• Tensile strength decreases by ~20–30%.
• Risk of creep deformation if stressed near yield limits.
• Below 0°C (32°F):
• Becomes slightly stronger but more brittle (impact resistance drops).

B. Corrosion & Erosion Impact

• Dezincification or pitting can reduce effective wall thickness, lowering pressure-bearing capacity.
• Erosion-corrosion (high-velocity seawater) may accelerate wear.

C. U-Bend Stress Considerations

• The bent region is work-hardened, increasing local strength but risking stress cracking if improperly annealed.
• Residual stresses from bending may require stress relief annealing.

3. Strength Comparison with Other Heat Exchanger Tubes

4. Design & Operational Strength Limits

• Max Allowable Pressure: Depends on tube diameter/wall thickness (use ASME BPVC Section VIII for calculations).
• Fatigue Life: Excellent for cyclic thermal loads (U-bend accommodates expansion).
• Avoid: Over-tightening in tube sheets (can collapse thin-walled tubes). Excessive vibration (may cause fretting wear).

5. Testing & Certification

• Hydrostatic Test: Ensures no leaks at 1.5x design pressure.
• Eddy Current/UT Testing: Checks for defects affecting strength.
• Certifications: ASTM B111 / ASME SB111, EN 12451 (EU).

​