- Misalignment of bushes
- Poor material, design of liner and seals
- Contaminated oil supply with foreign materials
- Fishing net, rope and similar material entering into seal due to defective rope guard.
- Electro static pitting on shaft due to defective shaft earthing device.
- Prolonged low speed operation, in which hydrodynamic oil film could not attain.
- Keep good alignment of bushes.
- Use good material and an improved seal design.
- Always maintain L.O level due to draught condition.
- Keep sufficient aft peak tank water level.
- Use good design of rope guard.
- Keep earthing device in good order.
- When stern tube seal leaks at sea, minimized as possible. To continue the voyage, following actions are to be taken.
- Correct the vessel trim, as possible as minimum astern, to certain allowable trim
- Use more viscous oil (e.g. Cylinder oil)
- Use lower header tank. If not possible, reduce the oil pressure-head by using a 'temporary header tank with flexible hose to obtain only slight pressure head above SW pressure.
- If required, reduce rpm to avoid boundary lubrication.
- Repairs or renewal of aft seal done either in dock or afloat.
- If vessel is due for dry docking survey or a dry dock facility is available, arrange to enter dry dock and renew both seals.
- If dry dock facility is not available, renewal of shaft seals done by Bonding method in port without removing propeller and tail shaft.
- Necessary vessel trim by ahead until propeller shaft exposed to correct position above water level and to set up "scaffolding.
- Renewal of sealing ring done by cutting and joining it on shaft with special tool and high temperature bonding method.
- When leakage occurs, inform to head office or owner through captain.
- When arrive in port, invite Class Survey and Underwriter Surveyor.
- Survey damage and by their recommendation, repair to be carried out as per Class requirement.
- Quotation of repairs and repair cost submitted to Underwriter Surveyor to negotiate for any reduction appear necessary.
- Both surveyors will survey the repaired work when completed.
- For insurance claim purpose, repair cost and bills endorsed by Underwriter Surveyor, but exclude transportation charges.
For insurance claim purpose the following items are necessary,
- Damage report
- log abstracts
- Damage report form for insurance claim
- Class Surveyor recommendation
- Repair bills endorsed by Underwriter Surveyor
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