Turbochargers of Marine Engines are important part of the system as they utilise the waste heat of the exhaust in order to supply charge air for scavenging of the engine. The equipment consists of turbine and blower attached on the same shaft. The rotation of turbine side as a result of the exhaust gases flowing over it turns the blower and supplies air to the scavenge side.
Turbocharger converts the waste energy of exhaust gas into useful work and hence it is important to maintain the machinery, or else the reduced efficiency will hamper the power output of the marine engine.
The Cleaning of the Turbine side and blower side is carried out at regular interval of time to remove carbon, soot, and other exhaust deposits. The cleaning of turbocharger is carried out when the engine is running.
If the turbine side cleaning is not carried out then the fouling may lead to back pressure & surging resulting in breakage of turbine blades.
If the blower side cleaning is not carried out properly, then the supply of air to engine will be reduced, resulting in lack of of air and improper combustion with black smoke.
Procedure for cleaning turbine side
Two methods are used to clean turbine side–
1) Water Washing
In this method, the engine speed is reduced until the temperature of the exhaust inlet falls below 420 °C. Fresh Water used for washing must be slightly hot and the water is injected through a regulating valve connected to the the turbine side. This is done to avoid thermal shock to the machinery.
While performing water washing the drain is kept open. When the water feed is closed the drain is observed until no water comes out.
The engine is run for further 20 minutes with less rpm to dry out the turbine from water. Before increasing the rpm, drain is shut and any abnormal vibration must be observed.
2) Dry Washing
For Dry washing carbon granules are used which are injected inside the turbine through compressed air system.
The engine speed is not reduced as there is no risk of thermal stresses in dry washing.
Procedure For Cleaning Blower Side
The Blower side of turbocharger is cleaned by fresh water. The engine is run at its full load rpm to achieve best possible cleaning. A container is fitted with an inlet line coming from the blower discharge side and the outlet line from the container or cylinder goes for washing blower side.
When the valve in the inlet of cylinder or container is opened, compressed air carry water with pressure and the kinetic energy of water cleans the blower.