Stern Tubes

Question 1

List the stern tube arrangements?

Answer 1

• Water lubricated
• Oil lubricated
• Shaft seal

Question 2

What maintenance needs to be carried out?

Answer 2

Oil
- Oil samples
- Oil changes
- Oil temperature monitoring

Shaft Seals
- Worn seals/ Gaskets
- Alignment checks

Water
- Refresh stagnate water

• Inspect bearings
• Lubricate/ Grease bearings
• Cleaning

Question 3

Explain Oil lubricated bearings?

Answer 3

Oil is circulated around the bearings which could be either thrust bearings or hydro dynamic bearings. These creating a film between the shaft and bearing allowing it to rotate with minimal wear

Question 4

What is in place to protect you if the temperature gets too high?

Answer 4

Temperature sensors which will alarm, some systems may even alarm causing an automatic shut down

Question 5

Stern tube oil sampling, what are you looking for?

Answer 5

• Physical appearance - Colour, Smell, Viscosity, Cloudy
• Water content
• Metal wear such as iron, copper, aluminium and chromium
• Acid number - Increase means degradation
• Base number - Amount of lubricating properties remaining

Question 6

How would water get into stern tube?

Answer 6

• Worn / Failure of a seal
• Incorrect installation of a seal
• Damage to the hull causing a change in shape

Question 7

Drawing and arrangement of water / oil cooled sterntube. Working knowledge?

Answer 7

See one note

Question 8

What if the stern tube oil was milky?

Answer 8

It indicates the presence of water meaning that a seal is leaking. A milky oil is a sign of emulsification