An abnormal flow reversal in a turbocharger compressor, evidenced by a loud banging or barking noise, caused by sudden load changes.
In practice
A single transient surge episode rarely causes immediate damage, but prolonged surging can damage compressor blades, loosen impeller nuts, and distort the volute casing. Engineers respond to surging by reducing engine load, adjusting the auxiliary blower, or opening the turbocharger bypass valve if fitted. Classification society rules and engine maker guidelines specify the action required in the event of repeated surge, including inspection of compressor blades for erosion and checking bearing clearances. Surge prevention strategies are particularly important on vessels fitted with selective catalytic reduction systems, where changes in exhaust backpressure affect turbocharger operating point.
Regulatory detail & full definition
Turbocharger surge is an aerodynamic instability that occurs when the compressor stage of a turbocharger attempts to maintain flow against a pressure ratio higher than it can sustain, causing the airflow to collapse and momentarily reverse. The resulting rapid pressure oscillation produces a distinctive repetitive banging or barking sound. On marine diesel engines surge typically occurs during rapid manoeuvring, heavy weather operation, scavenge fire, or when a cylinder is cut out of service, all of which alter the balance between exhaust energy and compressor demand.
A single transient surge episode rarely causes immediate damage, but prolonged surging can damage compressor blades, loosen impeller nuts, and distort the volute casing. Engineers respond to surging by reducing engine load, adjusting the auxiliary blower, or opening the turbocharger bypass valve if fitted. Classification society rules and engine maker guidelines specify the action required in the event of repeated surge, including inspection of compressor blades for erosion and checking bearing clearances. Surge prevention strategies are particularly important on vessels fitted with selective catalytic reduction systems, where changes in exhaust backpressure affect turbocharger operating point.