Class 2 (2nd Engineer) MEKG 📅 Nov 2023

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? (16)

Reference Answer

### 1. Prevention of Seawater Ingress in Oil Lubricated Stern Bearings (6 Marks)
The prevention of seawater ingress into an oil-lubricated stern tube is achieved through a combination of a precisely engineered sealing system and a carefully controlled static pressure head.
**A. Stern Tube Sealing Arrangement:**
* **Aft Seal Assembly:** This is the primary barrier against seawater. It is located at the outboard end of the stern tube. The assembly typically consists of multiple (usually 3 to 4) radial lip seals made from a durable, oil-resistant elastomer like Viton.

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