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Turbochargers safety and procedure for turbocharger cleaning

Turbochargers are among the most technologically advanced engine component onboard ship. Impeller blades of a medium sized turbocharger regularly rotate at as much as 400 revolutions per second. The outer edges of the rotor blades thus move at 1.5 times the speed of sound.

Safety
Great care must be exercised in the operation and maintenance of turbochargers. With regard to safety, it is essential to avoid the build up of fuel, cylinder or lubricating oil in the exhaust trunking before the turbocharger as it may result in combustion taking place in the exhaust manifold. Under these conditions the increase in quantity of exhaust gas available to the turbocharger can result in disastrous over speeding.

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The conditions leading to this phenomenon are generally to be found following long periods of slow steaming.

Exhaust gas turbocharger arrangement
Fig:Exhaust gas turbocharger arrangement

marine turbocharger

Fig:A turbocharger

If your vessel is involved in extended periods of slow steaming i.e. more than 24 hours the relevant management office must be advised and the following precautions are to be adhered to at daily intervals:
Overhauls

It is not recommended to extend overhaul periods beyond the manufacturers’ recommendations/PMS instructions. In the case of turbochargers using ball or roller bearings the overhaul period is generally controlled by the manufacturers recommendations regarding the change out of these bearings. Please ensure that the correct recommended and authorised bearings are used.

At each overhaul, the following are to be checked by the Chief Engineer
  1. Cleaning and Inspection of all parts as appropriate.
  2. Bearings change (roller or ball bearing type), check this carefully.
  3. Lubricating oil pump change (roller or ball bearing type).
  4. Balancing of the rotor assembly.
  5. Checking of the intake grid integrity.
  6. Examination for erosion and crack detection of the nozzle ring.
  7. Ultrasonic testing of the casings, particularly at cooling water inlet if any.
  8. Checking and re-securing of the silencer felt as required.
  9. Cleaning of the air filter elements.
  10. Examination of the bearing resilient housing.
  11. Measuring and recording of the impeller, bearings, thrust, seal clearances as appropriate to the type of turbocharger.
  12. Change of oil charge.

Turbocharger Cleaning

In order to maintain maximum performance cleaning of the turbocharger air and gas sides while the main engine is running must be in accordance with the manufacturer’s instructions. This usually takes the form of Water washing of the compressor side and either water washing or a combination of water and dry washing of the turbine side.

It must be remembered that the washing process of the compressor side, can result in deposits building up on the scavenge air cooler lines, and must therefore be followed if possible by cleaning of the air cooler. It is essential that air filters are kept clean , at intervals decided by pressure drop or visual inspection .Extra filter material should not be fitted outside of the manufacturers fitted units, except temporarily where the vessel is subject to ingress of sand or dust. For example sandstorm or while in / out of an iron ore port.



Read more on:

Turbo failure prevention
Damage to main engine and auxiliary engine turbochargers have a significant impact on the vessel’s ability to trade. Damages can lead to costly repairs, significant reduction in speed while at sea and can be a considerable safety hazard.More....

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