Class 2 (2nd Engineer) MEKG 📅 Mar 2021

Exam Question

Explain how the ingress of sea water is prevented in an oil lubricated stern bearing system. Should the system fail, describe the corrective action possible whilst the vessel is afloat. State why two stern bearing oil header tanks are fitted in some instances?

Reference Answer

Oil-Lubricated Stern Bearing System
The primary method for preventing seawater ingress into an oil-lubricated stern bearing system is a combination of mechanical seals and maintaining a balanced oil pressure. The system uses lip seals to contain the lubricating oil within the stern tube. An oil header tank ensures the oil pressure inside the stern tube is approximately equal to the surrounding seawater pressure. This balanced pressure prevents seawater from entering the stern tube.
Corrective Actions While Afloat
If the stern bearing system fails and seawater begins to ingress, the following temporary corrective actions can be taken while the vessel is still afloat:

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