ASTM B111 C70600 Copper Nickel Tube for Heat Exchangers

Because C70600 offers the best balance of corrosion resistance and heat transfer.

Heat exchanger tubes face three constant threats: corrosion from cooling water, fouling from marine organisms, and erosion from high flow velocity. ASTM B111 C70600 addresses all three.

Key advantages for heat exchangers:

Thermal conductivity of 45 W/(m·K) – efficient heat transfer without excessive wall thickness

Seawater corrosion resistance – lasts 20+ years in coastal power plant condensers

Biofouling resistance – reduces frequency of tube cleaning

Erosion resistance – withstands flow velocity up to 3.0 m/s with minimal wear

Standard OD ranges available from stock

Maximum tube length: up to 30 meters seamless. Longer lengths available upon request.

Wall thickness selection depends on three factors: pressure, corrosion allowance, and tube support spacing.

Step 1 – Calculate internal pressure requirement

For cooling water below 2.0 MPa, 0.89mm (20 BWG) is generally sufficient

For higher pressure or steam service, use 1.24mm (18 BWG) or thicker

Step 2 – Add corrosion allowance

Clean seawater: 0.1 – 0.2mm

Polluted or brackish water: 0.3 – 0.5mm

No additional allowance for internal corrosion if flow velocity is controlled

Step 3 – Check tube support spacing

Thinner tubes (0.89mm) require closer support spacing to prevent vibration

Thicker tubes (1.65mm+) can span longer distances between baffles

Common industrial practice: Most shell-and-tube heat exchangers with C70600 tubes use 19.05mm OD x 1.24mm wall thickness (18 BWG) for seawater cooling.

Even with excellent material properties, failures happen. Here are the real causes:

Most common failure location: Inlet end of tubes (first 300mm) due to turbulence and debris impingement.

Proper maintenance extends tube life to 25+ years.

Maintenance checklist:

Monthly

Monitor flow velocity (keep between 1.0 – 3.0 m/s)

Check inlet water debris (strainers / filters)

Record pressure drop across exchanger (sudden increase indicates fouling)

Quarterly

Perform eddy current testing on representative tubes

Measure wall thickness at inlet ends

Inspect tube sheet joints for leakage

Annually

Clean tubes with sponge balls or chemical cleaning (avoid ammonia-based cleaners)

Replace end caps and gaskets

Review water chemistry report (chloride, ammonia, oxygen, pH)

Do not use:

Hydrochloric acid for cleaning (causes pitting)

Steel brushes (scratches the protective oxide layer)

Ammonia-based solvents (causes stress corrosion cracking)

What is the maximum flow velocity for C70600 heat exchanger tube?

3.0 m/s for continuous seawater service. Up to 3.5 m/s is acceptable for clean water without solids. Above 3.5 m/s, erosion corrosion accelerates rapidly.

Can C70600 tube be used in brackish water service?

Yes, C70600 is one of the best materials for brackish water. The corrosion resistance is excellent even with variable salinity. However, avoid stagnant conditions and maintain flow above 1.0 m/s.

What is the difference between C70600 and C71500 for condenser tubes?

C70600 has higher thermal conductivity (45 vs 29 W/m·K) and lower cost. C71500 has better ammonia resistance and higher strength. For most power plant surface condensers, C70600 is the standard choice.

How to clean C70600 tubes without damaging them?

Use sponge balls (polyurethane) or chemical cleaning with sulfamic acid. Never use hydrochloric acid. Never use steel brushes. For heavy scale, consult a qualified chemical cleaning contractor.

What eddy current test standard applies to C70600 heat exchanger tubes?

ASTM E243 is the standard practice for eddy current testing of copper and copper alloy tubes. Request 100% eddy current testing with calibration standards per ASTM E243.

Is C70600 tube suitable for U-bundle heat exchangers?

Yes, C70600 is highly suitable for U-bend applications. Use stress-relieved tubes (not fully annealed) to reduce spring-back. Minimum bend radius is typically 1.5 x tube OD.

What is the typical tube pitch for C70600 in shell and tube heat exchanger?

Standard tube pitch is 1.25 x tube OD for triangular pattern, or 1.30 x tube OD for square pattern. For 19.05mm OD tubes, common pitches are 23.8mm (triangular) and 24.8mm (square).

Can C70600 tubes be expanded into tube sheets?

Yes, C70600 tubes expand easily. Use controlled rolling with 10–15% reduction in tube wall thickness. Always test expand two tubes before full production.

What gasket material is compatible with C70600 tube sheet joints?

Use non-asbestos gaskets or EPDM. Avoid gaskets containing free sulfur or high chlorides. Neoprene and nitrile are also acceptable.

How long does C70600 tube last in power plant surface condenser?

Typically 20–30 years with proper water chemistry and flow control. Many coastal power plants report 25+ years of service. Replace when wall thickness reduces by 40% or when frequent tube leaks occur.

What is the standard temper for C70600 heat exchanger tubes?

O60 (soft annealed) is standard. For U-bend applications, request stress-relieved tubes. Hard drawn tubes are not used for heat exchangers.

Does tube OD tolerance matter for heat exchanger assembly?

Yes, tight OD tolerance ensures proper fit in tube sheets. ASTM B111 requires OD tolerance of ±0.05mm for tubes under 25.4mm OD, and ±0.08mm for larger sizes.

Eddy current test (ECT) to ASTM E243

Hydrostatic test up to 20 MPa

PMI (XRF) for alloy verification on every heat

Mechanical property test (tensile, hardness, flattening, expansion)

Microscopic examination for grain structure

Flattening test per ASTM B111

Reverse flattening test for welded tubes (where applicable)

Plastic end caps on both ends to prevent contamination

Individual polybag wrapping for each tube

Wooden crates or steel spools for export

Moisture-proof paper and desiccant for sea shipment

Label with heat number, size, and quantity on each package

Color-coded bands for alloy identification

Extrusion press (1500T and 2500T)

Cold drawing machines (10 lines, OD range 4mm to 90mm)

Annealing furnaces (controlled atmosphere, 650–750°C)

Straightening and cutting lines

U-bending machine for heat exchanger tubes

Eddy current testing machines (3 units)

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