Turbocharger surging

What is turbocharger surging and how can it be avoided?

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Turbocharger surging occurs when the pressure of the exhaust gas is higher than the scavenge air pressure and hence backpressure develops in the turbocharger.
Usually noise and/or vibration is observer on the Turbocharger when surging occurs, while turbocharger RPM fluctuates rapidly.

Causes of surging can vary and are related but not limited to the following:

i) Improper balance of power generated by the engine
ii) Dirty or damaged turbocharger parts (i.e. compressor wheel, turbocharger bearings, nozzle ring, turbine wheel).
iii) Scavenging system irregularities. Mainly related to air cooler clogging or damaged tubes, damaged fins of mist catcher, high scavenge air temperature.
iv) Exhaust valve issues.
v) Fuel system issues, associated with improper operation of fuel valves, worn out plunger/barrels in fuel pumps (where applicable), quality of fuel, incorrect pre-heating temperature of the fuel.

In order to avoid the T/C surging the following practices should be followed:

  1. T/C washing (both dry and wet) to be performed following makers’ intervals.
  2. Air filter of the T/C should be cleaned.
  3. Air cooler pressure drop shall be monitored and when the drop indicates that the cooler is dirty, air cooler shall be chemically cleaned.
  4. Frequent mist catcher inspections to be done to evaluate condition.
  5. Main Engine performance to be evaluated and if any abnormality is detected (high exhaust gas, deviation in Pmax/Pcomp) the cause should be investigated immediately. Engine could be unbalanced and hence one cylinder can produce less power than the others.
  6. Avoid sudden changes of Main Engine Load.
  7. Turbocharger maintenance will need to be followed as per makers’ manual, with emphasis on the intervals of bearings replacement.
  8. Grating before the turbocharger will need to be inspected regularly and it should be clean and free of any deposits.
  9. Frequent scavenge inspections, ensuring no excessive carbon deposits in scavenge ports. Additionally, piston rings shall be intact, while flaps in the air receiver should also need to be intact without any damages.
  10. Exhaust gas boiler will need to be clean and free of any soot, as quite frequently dirty EGB can cause backpressure.