Heat Exchanger Failure Library
A guide to heat exchanger failure modes — tube fouling, tube leakage, gasket failure, corrosion, and erosion. Each includes symptoms, causes, and prevention.
Understanding Heat Exchanger Failures
Heat exchangers fail through fouling (efficiency loss), leakage (cross-contamination), and mechanical damage. Many failures are preventable through proper water treatment, filtration, and maintenance.
Tube Fouling
Fouling is the deposition of scale, biological growth, or particulate matter on heat transfer surfaces, reducing efficiency.
- Symptoms: Reduced heat transfer (approach temperature increases), increased pressure drop, reduced flow, and higher energy consumption for the same duty.
- Root causes: Hardness scaling (calcium/magnesium deposition from hot water), biological fouling (algae, bacteria in cooling water), particulate fouling (suspended solids), and chemical reaction fouling (polymerisation, corrosion products).
- Prevention: Maintain water treatment (scale inhibitor, biocide), install strainers or filters on the inlet, maintain flow velocity (above 1 m/s to prevent settling), use online cleaning (backwash, sponge ball cleaning), and clean on schedule.
Inspection tip
Monitor approach temperature (difference between hot outlet and cold outlet) — an increasing approach indicates fouling. Trend pressure drop. Inspect tubes during shutdown — look for scale, biological growth, and deposits.
Tube Leakage
Tube leakage allows cross-contamination between the two fluids, which can cause product contamination, safety hazards, or equipment damage.
- Symptoms: Fluid mixing (one fluid appears in the other), pressure changes, product contamination, and in hazardous service, safety risks.
- Root causes: Tube corrosion (pitting from water-side oxygen, chloride stress corrosion), tube erosion (high-velocity flow or particle impingement), vibration fatigue (flow-induced vibration at high velocities), thermal stress (rapid temperature changes), and freeze damage.
- Prevention: Maintain water treatment (oxygen scavenger, corrosion inhibitor), control flow velocity (not too high to cause erosion, not too low to cause fouling), install anti-vibration baffles, avoid rapid temperature changes, and use compatible tube materials.
Inspection tip
Pressure test tubes during shutdown (hydrotest at 1.5× design pressure). Use eddy current testing to detect tube wall thinning. Inspect for leakage by pressurising one side and monitoring the other.
Gasket Failure (Plate Exchangers)
In plate heat exchangers, gasket failure causes external leakage or internal cross-leakage between fluids.
- Symptoms: External fluid leakage from the plate pack, cross-contamination of fluids, loss of pressure, and need for frequent re-tightening.
- Root causes: Gasket ageing (hardening, compression set), chemical incompatibility (wrong gasket material for the fluid), thermal cycling (causes fatigue), over-compression (plates tightened too much), and gasket damage during reassembly.
- Prevention: Use the correct gasket material (EPDM for water/steam, NBR for oils, Viton for chemicals), replace gaskets on schedule, follow the manufacturer's tightening sequence and torque, and avoid thermal shock.
Inspection tip
Inspect for external leakage during operation. During maintenance, inspect gaskets for hardening, swelling, cracks, and compression set. Replace all gaskets when reassembling.
Corrosion
Corrosion attacks heat exchanger tubes, shells, and water boxes, causing leakage and eventual failure.
- Symptoms: Tube wall thinning (detected by eddy current testing), pitting on tube surfaces, rusty water, and eventual tube perforation.
- Root causes: Oxygen pitting (inadequate water treatment), galvanic corrosion (dissimilar tube and tubesheet materials), chloride stress corrosion (in stainless tubes handling chlorides), under-deposit corrosion (under scale or biological growth), and erosion-corrosion (flow-accelerated).
- Prevention: Maintain water treatment (oxygen scavenger, corrosion inhibitor, biocide), select compatible materials (316 for chlorides, titanium for seawater), install cathodic protection in water boxes, control flow velocity, and prevent fouling.
Inspection tip
Perform eddy current testing annually on critical tubes. Measure tube wall thickness. Inspect water boxes for pitting and galvanic corrosion. Check for under-deposit corrosion during cleaning.
Erosion
Erosion removes material from tube inlets, U-bends, and impingement areas through high-velocity fluid or particle impact.
- Symptoms: Localized wall thinning (tube inlets, U-bends), reduced tube life, and eventual tube perforation at erosion points.
- Root causes: High-velocity flow (above design), particulate matter in the fluid, cavitation (in liquid service), and impingement (fluid entering the shell directly hitting tubes).
- Prevention: Control flow velocity within design limits, install impingement plates at shell inlet, install strainers or filters, use harder tube materials (cupro-nickel, titanium for erosive service), and avoid throttling valves that cause high-velocity jets.
Inspection tip
Inspect tube inlets and U-bends for smooth, polished wear during shutdown. Use eddy current testing to detect wall thinning. Check impingement plates for wear.
How CHI can help
Ask CHI about heat exchanger failure diagnosis and to recommend cleaning methods or material upgrades for your application. The CHI assistant can help you diagnose failure modes from symptoms, recommend inspection methods, and suggest preventive maintenance actions to avoid similar failures.