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Shell & Tube Tube Sheet Leakage (Galvanic Corrosion)

Likely causes

Copper tubes contacting steel tube sheet (dissimilar metals)

Check: galvanic corrosion erodes rolled joint

What to do: Confirm refrigerant/water cross-contamination: sample water side → refrigerant detector or bubble test; pressurize refrigerant side with N2 at 1.0 MPa and monitor water side

Cooling water pH < 7.0 or chloride > 200 ppm

Check: accelerated corrosion

What to do: Locate leaking tube: isolate water side, pressure-test each tube at 0.5 MPa → use soap film to find leak point on tube sheet

Poor tube rolling expansion

Check: crevice corrosion at tube-tubesheet interface

What to do: Minor leak: insert tube plug (brass/SS), retest pressure — if < 10% of tubes affected, continued operation acceptable

Operational vibration causes fatigue cracking at tube-tubesheet joint

Check: Inspect with instruments or visually

What to do: Severe leak: replace complete STHE; upgrade tube material to 90-10 cupronickel (Cu-Ni) to eliminate galvanic issue

Refrigerant pressure (> 1.5 MPa) exceeds water pressure

Check: refrigerant leaks into water side

What to do: Water treatment: maintain pH 7.2~8.5, chloride < 100 ppm, monthly water analysis

Field tip

If a refrigerant detector reacts to the water-side sample, 100% tube failure — stop operation immediately and plug tubes.

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